jdk-sandbox: comparison hotspot/src/share/vm/runtime/synchronizer.cpp

equal deleted inserted replaced

-:11c11e616b91
+:dc9b63952682
 #define ATTR __attribute__((noinline))
 #else
 #define ATTR
 #endif
-// Native markword accessors for synchronization and hashCode().
-//
 // The "core" versions of monitor enter and exit reside in this file.
 // The interpreter and compilers contain specialized transliterated
 // variants of the enter-exit fast-path operations.  See i486.ad fast_lock(),
 // for instance.  If you make changes here, make sure to modify the
 // interpreter, and both C1 and C2 fast-path inline locking code emission.
 //
-// TODO: merge the objectMonitor and synchronizer classes.
 //
 // -----------------------------------------------------------------------------
 #ifdef DTRACE_ENABLED
 // TODO-FIXME: probes should not fire when caller is _blocked.  assert() accordingly.
 HS_DTRACE_PROBE_DECL5(hotspot, monitor__wait,
 jlong, uintptr_t, char*, int, long);
 HS_DTRACE_PROBE_DECL4(hotspot, monitor__waited,
-jlong, uintptr_t, char*, int);
-HS_DTRACE_PROBE_DECL4(hotspot, monitor__notify,
-jlong, uintptr_t, char*, int);
-HS_DTRACE_PROBE_DECL4(hotspot, monitor__notifyAll,
-jlong, uintptr_t, char*, int);
-HS_DTRACE_PROBE_DECL4(hotspot, monitor__contended__enter,
-jlong, uintptr_t, char*, int);
-HS_DTRACE_PROBE_DECL4(hotspot, monitor__contended__entered,
-jlong, uintptr_t, char*, int);
-HS_DTRACE_PROBE_DECL4(hotspot, monitor__contended__exit,
 jlong, uintptr_t, char*, int);
 #define DTRACE_MONITOR_PROBE_COMMON(klassOop, thread)                      \
 char* bytes = NULL;                                                      \
 int len = 0;                                                             \
 #define DTRACE_MONITOR_WAIT_PROBE(klassOop, thread, millis, mon)    {;}
 #define DTRACE_MONITOR_PROBE(probe, klassOop, thread, mon)          {;}
 #endif // ndef DTRACE_ENABLED
-// ObjectWaiter serves as a "proxy" or surrogate thread.
+// This exists only as a workaround of dtrace bug 6254741
-// TODO-FIXME: Eliminate ObjectWaiter and use the thread-specific
+int dtrace_waited_probe(ObjectMonitor* monitor, Handle obj, Thread* thr) {
-// ParkEvent instead.  Beware, however, that the JVMTI code
+DTRACE_MONITOR_PROBE(waited, monitor, obj(), thr);
-// knows about ObjectWaiters, so we'll have to reconcile that code.
+return 0;
-// See next_waiter(), first_waiter(), etc.
+}
-class ObjectWaiter : public StackObj {
+#define NINFLATIONLOCKS 256
-public:
+static volatile intptr_t InflationLocks [NINFLATIONLOCKS] ;
-enum TStates { TS_UNDEF, TS_READY, TS_RUN, TS_WAIT, TS_ENTER, TS_CXQ } ;
-enum Sorted  { PREPEND, APPEND, SORTED } ;
+ObjectMonitor * ObjectSynchronizer::gBlockList = NULL ;
-ObjectWaiter * volatile _next;
+ObjectMonitor * volatile ObjectSynchronizer::gFreeList  = NULL ;
-ObjectWaiter * volatile _prev;
+ObjectMonitor * volatile ObjectSynchronizer::gOmInUseList  = NULL ;
-Thread*       _thread;
+int ObjectSynchronizer::gOmInUseCount = 0;
-ParkEvent *   _event;
+static volatile intptr_t ListLock = 0 ;      // protects global monitor free-list cache
-volatile int  _notified ;
+static volatile int MonitorFreeCount  = 0 ;      // # on gFreeList
-volatile TStates TState ;
+static volatile int MonitorPopulation = 0 ;      // # Extant -- in circulation
-Sorted        _Sorted ;           // List placement disposition
+#define CHAINMARKER ((oop)-1)
-bool          _active ;           // Contention monitoring is enabled
-public:
+// -----------------------------------------------------------------------------
-ObjectWaiter(Thread* thread) {
+//  Fast Monitor Enter/Exit
-_next     = NULL;
+// This the fast monitor enter. The interpreter and compiler use
-_prev     = NULL;
+// some assembly copies of this code. Make sure update those code
-_notified = 0;
+// if the following function is changed. The implementation is
-TState    = TS_RUN ;
+// extremely sensitive to race condition. Be careful.
-_thread   = thread;
-_event    = thread->_ParkEvent ;
+void ObjectSynchronizer::fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias, TRAPS) {
-_active   = false;
+if (UseBiasedLocking) {
-assert (_event != NULL, "invariant") ;
+if (!SafepointSynchronize::is_at_safepoint()) {
-}
+BiasedLocking::Condition cond = BiasedLocking::revoke_and_rebias(obj, attempt_rebias, THREAD);
+if (cond == BiasedLocking::BIAS_REVOKED_AND_REBIASED) {
-void wait_reenter_begin(ObjectMonitor *mon) {
+return;
-JavaThread *jt = (JavaThread *)this->_thread;
+}
-_active = JavaThreadBlockedOnMonitorEnterState::wait_reenter_begin(jt, mon);
+} else {
-}
+assert(!attempt_rebias, "can not rebias toward VM thread");
+BiasedLocking::revoke_at_safepoint(obj);
-void wait_reenter_end(ObjectMonitor *mon) {
+}
-JavaThread *jt = (JavaThread *)this->_thread;
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-JavaThreadBlockedOnMonitorEnterState::wait_reenter_end(jt, _active);
+}
-}
-};
+slow_enter (obj, lock, THREAD) ;
+}
-enum ManifestConstants {
-ClearResponsibleAtSTW   = 0,
+void ObjectSynchronizer::fast_exit(oop object, BasicLock* lock, TRAPS) {
-MaximumRecheckInterval  = 1000
+assert(!object->mark()->has_bias_pattern(), "should not see bias pattern here");
-} ;
+// if displaced header is null, the previous enter is recursive enter, no-op
+markOop dhw = lock->displaced_header();
+markOop mark ;
-#undef TEVENT
+if (dhw == NULL) {
-#define TEVENT(nom) {if (SyncVerbose) FEVENT(nom); }
+// Recursive stack-lock.
+// Diagnostics -- Could be: stack-locked, inflating, inflated.
-#define FEVENT(nom) { static volatile int ctr = 0 ; int v = ++ctr ; if ((v & (v-1)) == 0) { ::printf (#nom " : %d \n", v); ::fflush(stdout); }}
+mark = object->mark() ;
+assert (!mark->is_neutral(), "invariant") ;
-#undef  TEVENT
+if (mark->has_locker() && mark != markOopDesc::INFLATING()) {
-#define TEVENT(nom) {;}
+assert(THREAD->is_lock_owned((address)mark->locker()), "invariant") ;
+}
+if (mark->has_monitor()) {
+ObjectMonitor * m = mark->monitor() ;
+assert(((oop)(m->object()))->mark() == mark, "invariant") ;
+assert(m->is_entered(THREAD), "invariant") ;
+}
+return ;
+}
+mark = object->mark() ;
+// If the object is stack-locked by the current thread, try to
+// swing the displaced header from the box back to the mark.
+if (mark == (markOop) lock) {
+assert (dhw->is_neutral(), "invariant") ;
+if ((markOop) Atomic::cmpxchg_ptr (dhw, object->mark_addr(), mark) == mark) {
+TEVENT (fast_exit: release stacklock) ;
+return;
+}
+}
+ObjectSynchronizer::inflate(THREAD, object)->exit (THREAD) ;
+}
+// -----------------------------------------------------------------------------
+// Interpreter/Compiler Slow Case
+// This routine is used to handle interpreter/compiler slow case
+// We don't need to use fast path here, because it must have been
+// failed in the interpreter/compiler code.
+void ObjectSynchronizer::slow_enter(Handle obj, BasicLock* lock, TRAPS) {
+markOop mark = obj->mark();
+assert(!mark->has_bias_pattern(), "should not see bias pattern here");
+if (mark->is_neutral()) {
+// Anticipate successful CAS -- the ST of the displaced mark must
+// be visible <= the ST performed by the CAS.
+lock->set_displaced_header(mark);
+if (mark == (markOop) Atomic::cmpxchg_ptr(lock, obj()->mark_addr(), mark)) {
+TEVENT (slow_enter: release stacklock) ;
+return ;
+}
+// Fall through to inflate() ...
+} else
+if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) {
+assert(lock != mark->locker(), "must not re-lock the same lock");
+assert(lock != (BasicLock*)obj->mark(), "don't relock with same BasicLock");
+lock->set_displaced_header(NULL);
+return;
+}
+#if 0
+// The following optimization isn't particularly useful.
+if (mark->has_monitor() && mark->monitor()->is_entered(THREAD)) {
+lock->set_displaced_header (NULL) ;
+return ;
+}
+#endif
+// The object header will never be displaced to this lock,
+// so it does not matter what the value is, except that it
+// must be non-zero to avoid looking like a re-entrant lock,
+// and must not look locked either.
+lock->set_displaced_header(markOopDesc::unused_mark());
+ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD);
+}
+// This routine is used to handle interpreter/compiler slow case
+// We don't need to use fast path here, because it must have
+// failed in the interpreter/compiler code. Simply use the heavy
+// weight monitor should be ok, unless someone find otherwise.
+void ObjectSynchronizer::slow_exit(oop object, BasicLock* lock, TRAPS) {
+fast_exit (object, lock, THREAD) ;
+}
+// -----------------------------------------------------------------------------
+// Class Loader  support to workaround deadlocks on the class loader lock objects
+// Also used by GC
+// complete_exit()/reenter() are used to wait on a nested lock
+// i.e. to give up an outer lock completely and then re-enter
+// Used when holding nested locks - lock acquisition order: lock1 then lock2
+//  1) complete_exit lock1 - saving recursion count
+//  2) wait on lock2
+//  3) when notified on lock2, unlock lock2
+//  4) reenter lock1 with original recursion count
+//  5) lock lock2
+// NOTE: must use heavy weight monitor to handle complete_exit/reenter()
+intptr_t ObjectSynchronizer::complete_exit(Handle obj, TRAPS) {
+TEVENT (complete_exit) ;
+if (UseBiasedLocking) {
+BiasedLocking::revoke_and_rebias(obj, false, THREAD);
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj());
+return monitor->complete_exit(THREAD);
+}
+// NOTE: must use heavy weight monitor to handle complete_exit/reenter()
+void ObjectSynchronizer::reenter(Handle obj, intptr_t recursion, TRAPS) {
+TEVENT (reenter) ;
+if (UseBiasedLocking) {
+BiasedLocking::revoke_and_rebias(obj, false, THREAD);
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj());
+monitor->reenter(recursion, THREAD);
+}
+// -----------------------------------------------------------------------------
+// JNI locks on java objects
+// NOTE: must use heavy weight monitor to handle jni monitor enter
+void ObjectSynchronizer::jni_enter(Handle obj, TRAPS) { // possible entry from jni enter
+// the current locking is from JNI instead of Java code
+TEVENT (jni_enter) ;
+if (UseBiasedLocking) {
+BiasedLocking::revoke_and_rebias(obj, false, THREAD);
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+THREAD->set_current_pending_monitor_is_from_java(false);
+ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD);
+THREAD->set_current_pending_monitor_is_from_java(true);
+}
+// NOTE: must use heavy weight monitor to handle jni monitor enter
+bool ObjectSynchronizer::jni_try_enter(Handle obj, Thread* THREAD) {
+if (UseBiasedLocking) {
+BiasedLocking::revoke_and_rebias(obj, false, THREAD);
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+ObjectMonitor* monitor = ObjectSynchronizer::inflate_helper(obj());
+return monitor->try_enter(THREAD);
+}
+// NOTE: must use heavy weight monitor to handle jni monitor exit
+void ObjectSynchronizer::jni_exit(oop obj, Thread* THREAD) {
+TEVENT (jni_exit) ;
+if (UseBiasedLocking) {
+BiasedLocking::revoke_and_rebias(obj, false, THREAD);
+}
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj);
+// If this thread has locked the object, exit the monitor.  Note:  can't use
+// monitor->check(CHECK); must exit even if an exception is pending.
+if (monitor->check(THREAD)) {
+monitor->exit(THREAD);
+}
+}
+// -----------------------------------------------------------------------------
+// Internal VM locks on java objects
+// standard constructor, allows locking failures
+ObjectLocker::ObjectLocker(Handle obj, Thread* thread, bool doLock) {
+_dolock = doLock;
+_thread = thread;
+debug_only(if (StrictSafepointChecks) _thread->check_for_valid_safepoint_state(false);)
+_obj = obj;
+if (_dolock) {
+TEVENT (ObjectLocker) ;
+ObjectSynchronizer::fast_enter(_obj, &_lock, false, _thread);
+}
+}
+ObjectLocker::~ObjectLocker() {
+if (_dolock) {
+ObjectSynchronizer::fast_exit(_obj(), &_lock, _thread);
+}
+}
+// -----------------------------------------------------------------------------
+//  Wait/Notify/NotifyAll
+// NOTE: must use heavy weight monitor to handle wait()
+void ObjectSynchronizer::wait(Handle obj, jlong millis, TRAPS) {
+if (UseBiasedLocking) {
+BiasedLocking::revoke_and_rebias(obj, false, THREAD);
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+if (millis < 0) {
+TEVENT (wait - throw IAX) ;
+THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative");
+}
+ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj());
+DTRACE_MONITOR_WAIT_PROBE(monitor, obj(), THREAD, millis);
+monitor->wait(millis, true, THREAD);
+/* This dummy call is in place to get around dtrace bug 6254741.  Once
+that's fixed we can uncomment the following line and remove the call */
+// DTRACE_MONITOR_PROBE(waited, monitor, obj(), THREAD);
+dtrace_waited_probe(monitor, obj, THREAD);
+}
+void ObjectSynchronizer::waitUninterruptibly (Handle obj, jlong millis, TRAPS) {
+if (UseBiasedLocking) {
+BiasedLocking::revoke_and_rebias(obj, false, THREAD);
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+if (millis < 0) {
+TEVENT (wait - throw IAX) ;
+THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative");
+}
+ObjectSynchronizer::inflate(THREAD, obj()) -> wait(millis, false, THREAD) ;
+}
+void ObjectSynchronizer::notify(Handle obj, TRAPS) {
+if (UseBiasedLocking) {
+BiasedLocking::revoke_and_rebias(obj, false, THREAD);
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+markOop mark = obj->mark();
+if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) {
+return;
+}
+ObjectSynchronizer::inflate(THREAD, obj())->notify(THREAD);
+}
+// NOTE: see comment of notify()
+void ObjectSynchronizer::notifyall(Handle obj, TRAPS) {
+if (UseBiasedLocking) {
+BiasedLocking::revoke_and_rebias(obj, false, THREAD);
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+markOop mark = obj->mark();
+if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) {
+return;
+}
+ObjectSynchronizer::inflate(THREAD, obj())->notifyAll(THREAD);
+}
+// -----------------------------------------------------------------------------
+// Hash Code handling
+//
 // Performance concern:
 // OrderAccess::storestore() calls release() which STs 0 into the global volatile
 // OrderAccess::Dummy variable.  This store is unnecessary for correctness.
 // Many threads STing into a common location causes considerable cache migration
 // or "sloshing" on large SMP system.  As such, I avoid using OrderAccess::storestore()
 } ;
 static SharedGlobals GVars ;
 static int MonitorScavengeThreshold = 1000000 ;
 static volatile int ForceMonitorScavenge = 0 ; // Scavenge required and pending
-// Tunables ...
-// The knob* variables are effectively final.  Once set they should
-// never be modified hence.  Consider using __read_mostly with GCC.
-static int Knob_LogSpins           = 0 ;       // enable jvmstat tally for spins
-static int Knob_HandOff            = 0 ;
-static int Knob_Verbose            = 0 ;
-static int Knob_ReportSettings     = 0 ;
-static int Knob_SpinLimit          = 5000 ;    // derived by an external tool -
-static int Knob_SpinBase           = 0 ;       // Floor AKA SpinMin
-static int Knob_SpinBackOff        = 0 ;       // spin-loop backoff
-static int Knob_CASPenalty         = -1 ;      // Penalty for failed CAS
-static int Knob_OXPenalty          = -1 ;      // Penalty for observed _owner change
-static int Knob_SpinSetSucc        = 1 ;       // spinners set the _succ field
-static int Knob_SpinEarly          = 1 ;
-static int Knob_SuccEnabled        = 1 ;       // futile wake throttling
-static int Knob_SuccRestrict       = 0 ;       // Limit successors + spinners to at-most-one
-static int Knob_MaxSpinners        = -1 ;      // Should be a function of # CPUs
-static int Knob_Bonus              = 100 ;     // spin success bonus
-static int Knob_BonusB             = 100 ;     // spin success bonus
-static int Knob_Penalty            = 200 ;     // spin failure penalty
-static int Knob_Poverty            = 1000 ;
-static int Knob_SpinAfterFutile    = 1 ;       // Spin after returning from park()
-static int Knob_FixedSpin          = 0 ;
-static int Knob_OState             = 3 ;       // Spinner checks thread state of _owner
-static int Knob_UsePause           = 1 ;
-static int Knob_ExitPolicy         = 0 ;
-static int Knob_PreSpin            = 10 ;      // 20-100 likely better
-static int Knob_ResetEvent         = 0 ;
-static int BackOffMask             = 0 ;
-static int Knob_FastHSSEC          = 0 ;
-static int Knob_MoveNotifyee       = 2 ;       // notify() - disposition of notifyee
-static int Knob_QMode              = 0 ;       // EntryList-cxq policy - queue discipline
-static volatile int InitDone       = 0 ;
-// hashCode() generation :
-//
-// Possibilities:
-// * MD5Digest of {obj,stwRandom}
-// * CRC32 of {obj,stwRandom} or any linear-feedback shift register function.
-// * A DES- or AES-style SBox[] mechanism
-// * One of the Phi-based schemes, such as:
-//   2654435761 = 2^32 * Phi (golden ratio)
-//   HashCodeValue = ((uintptr_t(obj) >> 3) * 2654435761) ^ GVars.stwRandom ;
-// * A variation of Marsaglia's shift-xor RNG scheme.
-// * (obj ^ stwRandom) is appealing, but can result
-//   in undesirable regularity in the hashCode values of adjacent objects
-//   (objects allocated back-to-back, in particular).  This could potentially
-//   result in hashtable collisions and reduced hashtable efficiency.
-//   There are simple ways to "diffuse" the middle address bits over the
-//   generated hashCode values:
-//
-static inline intptr_t get_next_hash(Thread * Self, oop obj) {
-intptr_t value = 0 ;
-if (hashCode == 0) {
-// This form uses an unguarded global Park-Miller RNG,
-// so it's possible for two threads to race and generate the same RNG.
-// On MP system we'll have lots of RW access to a global, so the
-// mechanism induces lots of coherency traffic.
-value = os::random() ;
-} else
-if (hashCode == 1) {
-// This variation has the property of being stable (idempotent)
-// between STW operations.  This can be useful in some of the 1-0
-// synchronization schemes.
-intptr_t addrBits = intptr_t(obj) >> 3 ;
-value = addrBits ^ (addrBits >> 5) ^ GVars.stwRandom ;
-} else
-if (hashCode == 2) {
-value = 1 ;            // for sensitivity testing
-} else
-if (hashCode == 3) {
-value = ++GVars.hcSequence ;
-} else
-if (hashCode == 4) {
-value = intptr_t(obj) ;
-} else {
-// Marsaglia's xor-shift scheme with thread-specific state
-// This is probably the best overall implementation -- we'll
-// likely make this the default in future releases.
-unsigned t = Self->_hashStateX ;
-t ^= (t << 11) ;
-Self->_hashStateX = Self->_hashStateY ;
-Self->_hashStateY = Self->_hashStateZ ;
-Self->_hashStateZ = Self->_hashStateW ;
-unsigned v = Self->_hashStateW ;
-v = (v ^ (v >> 19)) ^ (t ^ (t >> 8)) ;
-Self->_hashStateW = v ;
-value = v ;
-}
-value &= markOopDesc::hash_mask;
-if (value == 0) value = 0xBAD ;
-assert (value != markOopDesc::no_hash, "invariant") ;
-TEVENT (hashCode: GENERATE) ;
-return value;
-}
-void BasicLock::print_on(outputStream* st) const {
-st->print("monitor");
-}
-void BasicLock::move_to(oop obj, BasicLock* dest) {
-// Check to see if we need to inflate the lock. This is only needed
-// if an object is locked using "this" lightweight monitor. In that
-// case, the displaced_header() is unlocked, because the
-// displaced_header() contains the header for the originally unlocked
-// object. However the object could have already been inflated. But it
-// does not matter, the inflation will just a no-op. For other cases,
-// the displaced header will be either 0x0 or 0x3, which are location
-// independent, therefore the BasicLock is free to move.
-//
-// During OSR we may need to relocate a BasicLock (which contains a
-// displaced word) from a location in an interpreter frame to a
-// new location in a compiled frame.  "this" refers to the source
-// basiclock in the interpreter frame.  "dest" refers to the destination
-// basiclock in the new compiled frame.  We *always* inflate in move_to().
-// The always-Inflate policy works properly, but in 1.5.0 it can sometimes
-// cause performance problems in code that makes heavy use of a small # of
-// uncontended locks.   (We'd inflate during OSR, and then sync performance
-// would subsequently plummet because the thread would be forced thru the slow-path).
-// This problem has been made largely moot on IA32 by inlining the inflated fast-path
-// operations in Fast_Lock and Fast_Unlock in i486.ad.
-//
-// Note that there is a way to safely swing the object's markword from
-// one stack location to another.  This avoids inflation.  Obviously,
-// we need to ensure that both locations refer to the current thread's stack.
-// There are some subtle concurrency issues, however, and since the benefit is
-// is small (given the support for inflated fast-path locking in the fast_lock, etc)
-// we'll leave that optimization for another time.
-if (displaced_header()->is_neutral()) {
-ObjectSynchronizer::inflate_helper(obj);
-// WARNING: We can not put check here, because the inflation
-// will not update the displaced header. Once BasicLock is inflated,
-// no one should ever look at its content.
-} else {
-// Typically the displaced header will be 0 (recursive stack lock) or
-// unused_mark.  Naively we'd like to assert that the displaced mark
-// value is either 0, neutral, or 3.  But with the advent of the
-// store-before-CAS avoidance in fast_lock/compiler_lock_object
-// we can find any flavor mark in the displaced mark.
-}
-// [RGV] The next line appears to do nothing!
-intptr_t dh = (intptr_t) displaced_header();
-dest->set_displaced_header(displaced_header());
-}
-// -----------------------------------------------------------------------------
-// standard constructor, allows locking failures
-ObjectLocker::ObjectLocker(Handle obj, Thread* thread, bool doLock) {
-_dolock = doLock;
-_thread = thread;
-debug_only(if (StrictSafepointChecks) _thread->check_for_valid_safepoint_state(false);)
-_obj = obj;
-if (_dolock) {
-TEVENT (ObjectLocker) ;
-ObjectSynchronizer::fast_enter(_obj, &_lock, false, _thread);
-}
-}
-ObjectLocker::~ObjectLocker() {
-if (_dolock) {
-ObjectSynchronizer::fast_exit(_obj(), &_lock, _thread);
-}
-}
-// -----------------------------------------------------------------------------
-PerfCounter * ObjectSynchronizer::_sync_Inflations                  = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_Deflations                  = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_ContendedLockAttempts       = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_FutileWakeups               = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_Parks                       = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_EmptyNotifications          = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_Notifications               = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_PrivateA                    = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_PrivateB                    = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_SlowExit                    = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_SlowEnter                   = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_SlowNotify                  = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_SlowNotifyAll               = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_FailedSpins                 = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_SuccessfulSpins             = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_MonInCirculation            = NULL ;
-PerfCounter * ObjectSynchronizer::_sync_MonScavenged                = NULL ;
-PerfLongVariable * ObjectSynchronizer::_sync_MonExtant              = NULL ;
-// One-shot global initialization for the sync subsystem.
-// We could also defer initialization and initialize on-demand
-// the first time we call inflate().  Initialization would
-// be protected - like so many things - by the MonitorCache_lock.
-void ObjectSynchronizer::Initialize () {
-static int InitializationCompleted = 0 ;
-assert (InitializationCompleted == 0, "invariant") ;
-InitializationCompleted = 1 ;
-if (UsePerfData) {
-EXCEPTION_MARK ;
-#define NEWPERFCOUNTER(n)   {n = PerfDataManager::create_counter(SUN_RT, #n, PerfData::U_Events,CHECK); }
-#define NEWPERFVARIABLE(n)  {n = PerfDataManager::create_variable(SUN_RT, #n, PerfData::U_Events,CHECK); }
-NEWPERFCOUNTER(_sync_Inflations) ;
-NEWPERFCOUNTER(_sync_Deflations) ;
-NEWPERFCOUNTER(_sync_ContendedLockAttempts) ;
-NEWPERFCOUNTER(_sync_FutileWakeups) ;
-NEWPERFCOUNTER(_sync_Parks) ;
-NEWPERFCOUNTER(_sync_EmptyNotifications) ;
-NEWPERFCOUNTER(_sync_Notifications) ;
-NEWPERFCOUNTER(_sync_SlowEnter) ;
-NEWPERFCOUNTER(_sync_SlowExit) ;
-NEWPERFCOUNTER(_sync_SlowNotify) ;
-NEWPERFCOUNTER(_sync_SlowNotifyAll) ;
-NEWPERFCOUNTER(_sync_FailedSpins) ;
-NEWPERFCOUNTER(_sync_SuccessfulSpins) ;
-NEWPERFCOUNTER(_sync_PrivateA) ;
-NEWPERFCOUNTER(_sync_PrivateB) ;
-NEWPERFCOUNTER(_sync_MonInCirculation) ;
-NEWPERFCOUNTER(_sync_MonScavenged) ;
-NEWPERFVARIABLE(_sync_MonExtant) ;
-#undef NEWPERFCOUNTER
-}
-}
-// Compile-time asserts
-// When possible, it's better to catch errors deterministically at
-// compile-time than at runtime.  The down-side to using compile-time
-// asserts is that error message -- often something about negative array
-// indices -- is opaque.
-#define CTASSERT(x) { int tag[1-(2*!(x))]; printf ("Tag @" INTPTR_FORMAT "\n", (intptr_t)tag); }
-void ObjectMonitor::ctAsserts() {
-CTASSERT(offset_of (ObjectMonitor, _header) == 0);
-}
-static int Adjust (volatile int * adr, int dx) {
-int v ;
-for (v = *adr ; Atomic::cmpxchg (v + dx, adr, v) != v; v = *adr) ;
-return v ;
-}
-// Ad-hoc mutual exclusion primitives: SpinLock and Mux
-//
-// We employ SpinLocks _only for low-contention, fixed-length
-// short-duration critical sections where we're concerned
-// about native mutex_t or HotSpot Mutex:: latency.
-// The mux construct provides a spin-then-block mutual exclusion
-// mechanism.
-//
-// Testing has shown that contention on the ListLock guarding gFreeList
-// is common.  If we implement ListLock as a simple SpinLock it's common
-// for the JVM to devolve to yielding with little progress.  This is true
-// despite the fact that the critical sections protected by ListLock are
-// extremely short.
-//
-// TODO-FIXME: ListLock should be of type SpinLock.
-// We should make this a 1st-class type, integrated into the lock
-// hierarchy as leaf-locks.  Critically, the SpinLock structure
-// should have sufficient padding to avoid false-sharing and excessive
-// cache-coherency traffic.
-typedef volatile int SpinLockT ;
-void Thread::SpinAcquire (volatile int * adr, const char * LockName) {
-if (Atomic::cmpxchg (1, adr, 0) == 0) {
-return ;   // normal fast-path return
-}
-// Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
-TEVENT (SpinAcquire - ctx) ;
-int ctr = 0 ;
-int Yields = 0 ;
-for (;;) {
-while (*adr != 0) {
-++ctr ;
-if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
-if (Yields > 5) {
-// Consider using a simple NakedSleep() instead.
-// Then SpinAcquire could be called by non-JVM threads
-Thread::current()->_ParkEvent->park(1) ;
-} else {
-os::NakedYield() ;
-++Yields ;
-}
-} else {
-SpinPause() ;
-}
-}
-if (Atomic::cmpxchg (1, adr, 0) == 0) return ;
-}
-}
-void Thread::SpinRelease (volatile int * adr) {
-assert (*adr != 0, "invariant") ;
-OrderAccess::fence() ;      // guarantee at least release consistency.
-// Roach-motel semantics.
-// It's safe if subsequent LDs and STs float "up" into the critical section,
-// but prior LDs and STs within the critical section can't be allowed
-// to reorder or float past the ST that releases the lock.
-*adr = 0 ;
-}
-// muxAcquire and muxRelease:
-//
-// *  muxAcquire and muxRelease support a single-word lock-word construct.
-//    The LSB of the word is set IFF the lock is held.
-//    The remainder of the word points to the head of a singly-linked list
-//    of threads blocked on the lock.
-//
-// *  The current implementation of muxAcquire-muxRelease uses its own
-//    dedicated Thread._MuxEvent instance.  If we're interested in
-//    minimizing the peak number of extant ParkEvent instances then
-//    we could eliminate _MuxEvent and "borrow" _ParkEvent as long
-//    as certain invariants were satisfied.  Specifically, care would need
-//    to be taken with regards to consuming unpark() "permits".
-//    A safe rule of thumb is that a thread would never call muxAcquire()
-//    if it's enqueued (cxq, EntryList, WaitList, etc) and will subsequently
-//    park().  Otherwise the _ParkEvent park() operation in muxAcquire() could
-//    consume an unpark() permit intended for monitorenter, for instance.
-//    One way around this would be to widen the restricted-range semaphore
-//    implemented in park().  Another alternative would be to provide
-//    multiple instances of the PlatformEvent() for each thread.  One
-//    instance would be dedicated to muxAcquire-muxRelease, for instance.
-//
-// *  Usage:
-//    -- Only as leaf locks
-//    -- for short-term locking only as muxAcquire does not perform
-//       thread state transitions.
-//
-// Alternatives:
-// *  We could implement muxAcquire and muxRelease with MCS or CLH locks
-//    but with parking or spin-then-park instead of pure spinning.
-// *  Use Taura-Oyama-Yonenzawa locks.
-// *  It's possible to construct a 1-0 lock if we encode the lockword as
-//    (List,LockByte).  Acquire will CAS the full lockword while Release
-//    will STB 0 into the LockByte.  The 1-0 scheme admits stranding, so
-//    acquiring threads use timers (ParkTimed) to detect and recover from
-//    the stranding window.  Thread/Node structures must be aligned on 256-byte
-//    boundaries by using placement-new.
-// *  Augment MCS with advisory back-link fields maintained with CAS().
-//    Pictorially:  LockWord -> T1 <-> T2 <-> T3 <-> ... <-> Tn <-> Owner.
-//    The validity of the backlinks must be ratified before we trust the value.
-//    If the backlinks are invalid the exiting thread must back-track through the
-//    the forward links, which are always trustworthy.
-// *  Add a successor indication.  The LockWord is currently encoded as
-//    (List, LOCKBIT:1).  We could also add a SUCCBIT or an explicit _succ variable
-//    to provide the usual futile-wakeup optimization.
-//    See RTStt for details.
-// *  Consider schedctl.sc_nopreempt to cover the critical section.
-//
-typedef volatile intptr_t MutexT ;      // Mux Lock-word
-enum MuxBits { LOCKBIT = 1 } ;
-void Thread::muxAcquire (volatile intptr_t * Lock, const char * LockName) {
-intptr_t w = Atomic::cmpxchg_ptr (LOCKBIT, Lock, 0) ;
-if (w == 0) return ;
-if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
-return ;
-}
-TEVENT (muxAcquire - Contention) ;
-ParkEvent * const Self = Thread::current()->_MuxEvent ;
-assert ((intptr_t(Self) & LOCKBIT) == 0, "invariant") ;
-for (;;) {
-int its = (os::is_MP() ? 100 : 0) + 1 ;
-// Optional spin phase: spin-then-park strategy
-while (--its >= 0) {
-w = *Lock ;
-if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
-return ;
-}
-}
-Self->reset() ;
-Self->OnList = intptr_t(Lock) ;
-// The following fence() isn't _strictly necessary as the subsequent
-// CAS() both serializes execution and ratifies the fetched *Lock value.
-OrderAccess::fence();
-for (;;) {
-w = *Lock ;
-if ((w & LOCKBIT) == 0) {
-if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
-Self->OnList = 0 ;   // hygiene - allows stronger asserts
-return ;
-}
-continue ;      // Interference -- *Lock changed -- Just retry
-}
-assert (w & LOCKBIT, "invariant") ;
-Self->ListNext = (ParkEvent *) (w & ~LOCKBIT );
-if (Atomic::cmpxchg_ptr (intptr_t(Self)|LOCKBIT, Lock, w) == w) break ;
-}
-while (Self->OnList != 0) {
-Self->park() ;
-}
-}
-}
-void Thread::muxAcquireW (volatile intptr_t * Lock, ParkEvent * ev) {
-intptr_t w = Atomic::cmpxchg_ptr (LOCKBIT, Lock, 0) ;
-if (w == 0) return ;
-if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
-return ;
-}
-TEVENT (muxAcquire - Contention) ;
-ParkEvent * ReleaseAfter = NULL ;
-if (ev == NULL) {
-ev = ReleaseAfter = ParkEvent::Allocate (NULL) ;
-}
-assert ((intptr_t(ev) & LOCKBIT) == 0, "invariant") ;
-for (;;) {
-guarantee (ev->OnList == 0, "invariant") ;
-int its = (os::is_MP() ? 100 : 0) + 1 ;
-// Optional spin phase: spin-then-park strategy
-while (--its >= 0) {
-w = *Lock ;
-if ((w & LOCKBIT) == 0 && Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
-if (ReleaseAfter != NULL) {
-ParkEvent::Release (ReleaseAfter) ;
-}
-return ;
-}
-}
-ev->reset() ;
-ev->OnList = intptr_t(Lock) ;
-// The following fence() isn't _strictly necessary as the subsequent
-// CAS() both serializes execution and ratifies the fetched *Lock value.
-OrderAccess::fence();
-for (;;) {
-w = *Lock ;
-if ((w & LOCKBIT) == 0) {
-if (Atomic::cmpxchg_ptr (w|LOCKBIT, Lock, w) == w) {
-ev->OnList = 0 ;
-// We call ::Release while holding the outer lock, thus
-// artificially lengthening the critical section.
-// Consider deferring the ::Release() until the subsequent unlock(),
-// after we've dropped the outer lock.
-if (ReleaseAfter != NULL) {
-ParkEvent::Release (ReleaseAfter) ;
-}
-return ;
-}
-continue ;      // Interference -- *Lock changed -- Just retry
-}
-assert (w & LOCKBIT, "invariant") ;
-ev->ListNext = (ParkEvent *) (w & ~LOCKBIT );
-if (Atomic::cmpxchg_ptr (intptr_t(ev)|LOCKBIT, Lock, w) == w) break ;
-}
-while (ev->OnList != 0) {
-ev->park() ;
-}
-}
-}
-// Release() must extract a successor from the list and then wake that thread.
-// It can "pop" the front of the list or use a detach-modify-reattach (DMR) scheme
-// similar to that used by ParkEvent::Allocate() and ::Release().  DMR-based
-// Release() would :
-// (A) CAS() or swap() null to *Lock, releasing the lock and detaching the list.
-// (B) Extract a successor from the private list "in-hand"
-// (C) attempt to CAS() the residual back into *Lock over null.
-//     If there were any newly arrived threads and the CAS() would fail.
-//     In that case Release() would detach the RATs, re-merge the list in-hand
-//     with the RATs and repeat as needed.  Alternately, Release() might
-//     detach and extract a successor, but then pass the residual list to the wakee.
-//     The wakee would be responsible for reattaching and remerging before it
-//     competed for the lock.
-//
-// Both "pop" and DMR are immune from ABA corruption -- there can be
-// multiple concurrent pushers, but only one popper or detacher.
-// This implementation pops from the head of the list.  This is unfair,
-// but tends to provide excellent throughput as hot threads remain hot.
-// (We wake recently run threads first).
-void Thread::muxRelease (volatile intptr_t * Lock)  {
-for (;;) {
-const intptr_t w = Atomic::cmpxchg_ptr (0, Lock, LOCKBIT) ;
-assert (w & LOCKBIT, "invariant") ;
-if (w == LOCKBIT) return ;
-ParkEvent * List = (ParkEvent *) (w & ~LOCKBIT) ;
-assert (List != NULL, "invariant") ;
-assert (List->OnList == intptr_t(Lock), "invariant") ;
-ParkEvent * nxt = List->ListNext ;
-// The following CAS() releases the lock and pops the head element.
-if (Atomic::cmpxchg_ptr (intptr_t(nxt), Lock, w) != w) {
-continue ;
-}
-List->OnList = 0 ;
-OrderAccess::fence() ;
-List->unpark () ;
-return ;
-}
-}
-// ObjectMonitor Lifecycle
-// -----------------------
-// Inflation unlinks monitors from the global gFreeList and
-// associates them with objects.  Deflation -- which occurs at
-// STW-time -- disassociates idle monitors from objects.  Such
-// scavenged monitors are returned to the gFreeList.
-//
-// The global list is protected by ListLock.  All the critical sections
-// are short and operate in constant-time.
-//
-// ObjectMonitors reside in type-stable memory (TSM) and are immortal.
-//
-// Lifecycle:
-// --   unassigned and on the global free list
-// --   unassigned and on a thread's private omFreeList
-// --   assigned to an object.  The object is inflated and the mark refers
-//      to the objectmonitor.
-//
-// TODO-FIXME:
-//
-// *  We currently protect the gFreeList with a simple lock.
-//    An alternate lock-free scheme would be to pop elements from the gFreeList
-//    with CAS.  This would be safe from ABA corruption as long we only
-//    recycled previously appearing elements onto the list in deflate_idle_monitors()
-//    at STW-time.  Completely new elements could always be pushed onto the gFreeList
-//    with CAS.  Elements that appeared previously on the list could only
-//    be installed at STW-time.
-//
-// *  For efficiency and to help reduce the store-before-CAS penalty
-//    the objectmonitors on gFreeList or local free lists should be ready to install
-//    with the exception of _header and _object.  _object can be set after inflation.
-//    In particular, keep all objectMonitors on a thread's private list in ready-to-install
-//    state with m.Owner set properly.
-//
-// *  We could all diffuse contention by using multiple global (FreeList, Lock)
-//    pairs -- threads could use trylock() and a cyclic-scan strategy to search for
-//    an unlocked free list.
-//
-// *  Add lifecycle tags and assert()s.
-//
-// *  Be more consistent about when we clear an objectmonitor's fields:
-//    A.  After extracting the objectmonitor from a free list.
-//    B.  After adding an objectmonitor to a free list.
-//
-ObjectMonitor * ObjectSynchronizer::gBlockList = NULL ;
-ObjectMonitor * volatile ObjectSynchronizer::gFreeList  = NULL ;
-ObjectMonitor * volatile ObjectSynchronizer::gOmInUseList  = NULL ;
-int ObjectSynchronizer::gOmInUseCount = 0;
-static volatile intptr_t ListLock = 0 ;      // protects global monitor free-list cache
-static volatile int MonitorFreeCount  = 0 ;      // # on gFreeList
-static volatile int MonitorPopulation = 0 ;      // # Extant -- in circulation
-#define CHAINMARKER ((oop)-1)
-// Constraining monitor pool growth via MonitorBound ...
-//
-// The monitor pool is grow-only.  We scavenge at STW safepoint-time, but the
-// the rate of scavenging is driven primarily by GC.  As such,  we can find
-// an inordinate number of monitors in circulation.
-// To avoid that scenario we can artificially induce a STW safepoint
-// if the pool appears to be growing past some reasonable bound.
-// Generally we favor time in space-time tradeoffs, but as there's no
-// natural back-pressure on the # of extant monitors we need to impose some
-// type of limit.  Beware that if MonitorBound is set to too low a value
-// we could just loop. In addition, if MonitorBound is set to a low value
-// we'll incur more safepoints, which are harmful to performance.
-// See also: GuaranteedSafepointInterval
-//
-// As noted elsewhere, the correct long-term solution is to deflate at
-// monitorexit-time, in which case the number of inflated objects is bounded
-// by the number of threads.  That policy obviates the need for scavenging at
-// STW safepoint time.   As an aside, scavenging can be time-consuming when the
-// # of extant monitors is large.   Unfortunately there's a day-1 assumption baked
-// into much HotSpot code that the object::monitor relationship, once established
-// or observed, will remain stable except over potential safepoints.
-//
-// We can use either a blocking synchronous VM operation or an async VM operation.
-// -- If we use a blocking VM operation :
-//    Calls to ScavengeCheck() should be inserted only into 'safe' locations in paths
-//    that lead to ::inflate() or ::omAlloc().
-//    Even though the safepoint will not directly induce GC, a GC might
-//    piggyback on the safepoint operation, so the caller should hold no naked oops.
-//    Furthermore, monitor::object relationships are NOT necessarily stable over this call
-//    unless the caller has made provisions to "pin" the object to the monitor, say
-//    by incrementing the monitor's _count field.
-// -- If we use a non-blocking asynchronous VM operation :
-//    the constraints above don't apply.  The safepoint will fire in the future
-//    at a more convenient time.  On the other hand the latency between posting and
-//    running the safepoint introduces or admits "slop" or laxity during which the
-//    monitor population can climb further above the threshold.  The monitor population,
-//    however, tends to converge asymptotically over time to a count that's slightly
-//    above the target value specified by MonitorBound.   That is, we avoid unbounded
-//    growth, albeit with some imprecision.
-//
-// The current implementation uses asynchronous VM operations.
-//
-// Ideally we'd check if (MonitorPopulation > MonitorBound) in omAlloc()
-// immediately before trying to grow the global list via allocation.
-// If the predicate was true then we'd induce a synchronous safepoint, wait
-// for the safepoint to complete, and then again to allocate from the global
-// free list.  This approach is much simpler and precise, admitting no "slop".
-// Unfortunately we can't safely safepoint in the midst of omAlloc(), so
-// instead we use asynchronous safepoints.
-static void InduceScavenge (Thread * Self, const char * Whence) {
-// Induce STW safepoint to trim monitors
-// Ultimately, this results in a call to deflate_idle_monitors() in the near future.
-// More precisely, trigger an asynchronous STW safepoint as the number
-// of active monitors passes the specified threshold.
-// TODO: assert thread state is reasonable
-if (ForceMonitorScavenge == 0 && Atomic::xchg (1, &ForceMonitorScavenge) == 0) {
-if (Knob_Verbose) {
-::printf ("Monitor scavenge - Induced STW @%s (%d)\n", Whence, ForceMonitorScavenge) ;
-::fflush(stdout) ;
-}
-// Induce a 'null' safepoint to scavenge monitors
-// Must VM_Operation instance be heap allocated as the op will be enqueue and posted
-// to the VMthread and have a lifespan longer than that of this activation record.
-// The VMThread will delete the op when completed.
-VMThread::execute (new VM_ForceAsyncSafepoint()) ;
-if (Knob_Verbose) {
-::printf ("Monitor scavenge - STW posted @%s (%d)\n", Whence, ForceMonitorScavenge) ;
-::fflush(stdout) ;
-}
-}
-}
-/* Too slow for general assert or debug
-void ObjectSynchronizer::verifyInUse (Thread *Self) {
-ObjectMonitor* mid;
-int inusetally = 0;
-for (mid = Self->omInUseList; mid != NULL; mid = mid->FreeNext) {
-inusetally ++;
-}
-assert(inusetally == Self->omInUseCount, "inuse count off");
-int freetally = 0;
-for (mid = Self->omFreeList; mid != NULL; mid = mid->FreeNext) {
-freetally ++;
-}
-assert(freetally == Self->omFreeCount, "free count off");
-}
-*/
-ObjectMonitor * ATTR ObjectSynchronizer::omAlloc (Thread * Self) {
-// A large MAXPRIVATE value reduces both list lock contention
-// and list coherency traffic, but also tends to increase the
-// number of objectMonitors in circulation as well as the STW
-// scavenge costs.  As usual, we lean toward time in space-time
-// tradeoffs.
-const int MAXPRIVATE = 1024 ;
-for (;;) {
-ObjectMonitor * m ;
-// 1: try to allocate from the thread's local omFreeList.
-// Threads will attempt to allocate first from their local list, then
-// from the global list, and only after those attempts fail will the thread
-// attempt to instantiate new monitors.   Thread-local free lists take
-// heat off the ListLock and improve allocation latency, as well as reducing
-// coherency traffic on the shared global list.
-m = Self->omFreeList ;
-if (m != NULL) {
-Self->omFreeList = m->FreeNext ;
-Self->omFreeCount -- ;
-// CONSIDER: set m->FreeNext = BAD -- diagnostic hygiene
-guarantee (m->object() == NULL, "invariant") ;
-if (MonitorInUseLists) {
-m->FreeNext = Self->omInUseList;
-Self->omInUseList = m;
-Self->omInUseCount ++;
-// verifyInUse(Self);
-} else {
-m->FreeNext = NULL;
-}
-return m ;
-}
-// 2: try to allocate from the global gFreeList
-// CONSIDER: use muxTry() instead of muxAcquire().
-// If the muxTry() fails then drop immediately into case 3.
-// If we're using thread-local free lists then try
-// to reprovision the caller's free list.
-if (gFreeList != NULL) {
-// Reprovision the thread's omFreeList.
-// Use bulk transfers to reduce the allocation rate and heat
-// on various locks.
-Thread::muxAcquire (&ListLock, "omAlloc") ;
-for (int i = Self->omFreeProvision; --i >= 0 && gFreeList != NULL; ) {
-MonitorFreeCount --;
-ObjectMonitor * take = gFreeList ;
-gFreeList = take->FreeNext ;
-guarantee (take->object() == NULL, "invariant") ;
-guarantee (!take->is_busy(), "invariant") ;
-take->Recycle() ;
-omRelease (Self, take, false) ;
-}
-Thread::muxRelease (&ListLock) ;
-Self->omFreeProvision += 1 + (Self->omFreeProvision/2) ;
-if (Self->omFreeProvision > MAXPRIVATE ) Self->omFreeProvision = MAXPRIVATE ;
-TEVENT (omFirst - reprovision) ;
-const int mx = MonitorBound ;
-if (mx > 0 && (MonitorPopulation-MonitorFreeCount) > mx) {
-// We can't safely induce a STW safepoint from omAlloc() as our thread
-// state may not be appropriate for such activities and callers may hold
-// naked oops, so instead we defer the action.
-InduceScavenge (Self, "omAlloc") ;
-}
-continue;
-}
-// 3: allocate a block of new ObjectMonitors
-// Both the local and global free lists are empty -- resort to malloc().
-// In the current implementation objectMonitors are TSM - immortal.
-assert (_BLOCKSIZE > 1, "invariant") ;
-ObjectMonitor * temp = new ObjectMonitor[_BLOCKSIZE];
-// NOTE: (almost) no way to recover if allocation failed.
-// We might be able to induce a STW safepoint and scavenge enough
-// objectMonitors to permit progress.
-if (temp == NULL) {
-vm_exit_out_of_memory (sizeof (ObjectMonitor[_BLOCKSIZE]), "Allocate ObjectMonitors") ;
-}
-// Format the block.
-// initialize the linked list, each monitor points to its next
-// forming the single linked free list, the very first monitor
-// will points to next block, which forms the block list.
-// The trick of using the 1st element in the block as gBlockList
-// linkage should be reconsidered.  A better implementation would
-// look like: class Block { Block * next; int N; ObjectMonitor Body [N] ; }
-for (int i = 1; i < _BLOCKSIZE ; i++) {
-temp[i].FreeNext = &temp[i+1];
-}
-// terminate the last monitor as the end of list
-temp[_BLOCKSIZE - 1].FreeNext = NULL ;
-// Element [0] is reserved for global list linkage
-temp[0].set_object(CHAINMARKER);
-// Consider carving out this thread's current request from the
-// block in hand.  This avoids some lock traffic and redundant
-// list activity.
-// Acquire the ListLock to manipulate BlockList and FreeList.
-// An Oyama-Taura-Yonezawa scheme might be more efficient.
-Thread::muxAcquire (&ListLock, "omAlloc [2]") ;
-MonitorPopulation += _BLOCKSIZE-1;
-MonitorFreeCount += _BLOCKSIZE-1;
-// Add the new block to the list of extant blocks (gBlockList).
-// The very first objectMonitor in a block is reserved and dedicated.
-// It serves as blocklist "next" linkage.
-temp[0].FreeNext = gBlockList;
-gBlockList = temp;
-// Add the new string of objectMonitors to the global free list
-temp[_BLOCKSIZE - 1].FreeNext = gFreeList ;
-gFreeList = temp + 1;
-Thread::muxRelease (&ListLock) ;
-TEVENT (Allocate block of monitors) ;
-}
-}
-// Place "m" on the caller's private per-thread omFreeList.
-// In practice there's no need to clamp or limit the number of
-// monitors on a thread's omFreeList as the only time we'll call
-// omRelease is to return a monitor to the free list after a CAS
-// attempt failed.  This doesn't allow unbounded #s of monitors to
-// accumulate on a thread's free list.
-//
-// In the future the usage of omRelease() might change and monitors
-// could migrate between free lists.  In that case to avoid excessive
-// accumulation we could  limit omCount to (omProvision*2), otherwise return
-// the objectMonitor to the global list.  We should drain (return) in reasonable chunks.
-// That is, *not* one-at-a-time.
-void ObjectSynchronizer::omRelease (Thread * Self, ObjectMonitor * m, bool fromPerThreadAlloc) {
-guarantee (m->object() == NULL, "invariant") ;
-// Remove from omInUseList
-if (MonitorInUseLists && fromPerThreadAlloc) {
-ObjectMonitor* curmidinuse = NULL;
-for (ObjectMonitor* mid = Self->omInUseList; mid != NULL; ) {
-if (m == mid) {
-// extract from per-thread in-use-list
-if (mid == Self->omInUseList) {
-Self->omInUseList = mid->FreeNext;
-} else if (curmidinuse != NULL) {
-curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist
-}
-Self->omInUseCount --;
-// verifyInUse(Self);
-break;
-} else {
-curmidinuse = mid;
-mid = mid->FreeNext;
-}
-}
-}
-// FreeNext is used for both onInUseList and omFreeList, so clear old before setting new
-m->FreeNext = Self->omFreeList ;
-Self->omFreeList = m ;
-Self->omFreeCount ++ ;
-}
-// Return the monitors of a moribund thread's local free list to
-// the global free list.  Typically a thread calls omFlush() when
-// it's dying.  We could also consider having the VM thread steal
-// monitors from threads that have not run java code over a few
-// consecutive STW safepoints.  Relatedly, we might decay
-// omFreeProvision at STW safepoints.
-//
-// Also return the monitors of a moribund thread"s omInUseList to
-// a global gOmInUseList under the global list lock so these
-// will continue to be scanned.
-//
-// We currently call omFlush() from the Thread:: dtor _after the thread
-// has been excised from the thread list and is no longer a mutator.
-// That means that omFlush() can run concurrently with a safepoint and
-// the scavenge operator.  Calling omFlush() from JavaThread::exit() might
-// be a better choice as we could safely reason that that the JVM is
-// not at a safepoint at the time of the call, and thus there could
-// be not inopportune interleavings between omFlush() and the scavenge
-// operator.
-void ObjectSynchronizer::omFlush (Thread * Self) {
-ObjectMonitor * List = Self->omFreeList ;  // Null-terminated SLL
-Self->omFreeList = NULL ;
-ObjectMonitor * Tail = NULL ;
-int Tally = 0;
-if (List != NULL) {
-ObjectMonitor * s ;
-for (s = List ; s != NULL ; s = s->FreeNext) {
-Tally ++ ;
-Tail = s ;
-guarantee (s->object() == NULL, "invariant") ;
-guarantee (!s->is_busy(), "invariant") ;
-s->set_owner (NULL) ;   // redundant but good hygiene
-TEVENT (omFlush - Move one) ;
-}
-guarantee (Tail != NULL && List != NULL, "invariant") ;
-}
-ObjectMonitor * InUseList = Self->omInUseList;
-ObjectMonitor * InUseTail = NULL ;
-int InUseTally = 0;
-if (InUseList != NULL) {
-Self->omInUseList = NULL;
-ObjectMonitor *curom;
-for (curom = InUseList; curom != NULL; curom = curom->FreeNext) {
-InUseTail = curom;
-InUseTally++;
-}
-// TODO debug
-assert(Self->omInUseCount == InUseTally, "inuse count off");
-Self->omInUseCount = 0;
-guarantee (InUseTail != NULL && InUseList != NULL, "invariant");
-}
-Thread::muxAcquire (&ListLock, "omFlush") ;
-if (Tail != NULL) {
-Tail->FreeNext = gFreeList ;
-gFreeList = List ;
-MonitorFreeCount += Tally;
-}
-if (InUseTail != NULL) {
-InUseTail->FreeNext = gOmInUseList;
-gOmInUseList = InUseList;
-gOmInUseCount += InUseTally;
-}
-Thread::muxRelease (&ListLock) ;
-TEVENT (omFlush) ;
-}
-// Get the next block in the block list.
-static inline ObjectMonitor* next(ObjectMonitor* block) {
-assert(block->object() == CHAINMARKER, "must be a block header");
-block = block->FreeNext ;
-assert(block == NULL || block->object() == CHAINMARKER, "must be a block header");
-return block;
-}
-// Fast path code shared by multiple functions
-ObjectMonitor* ObjectSynchronizer::inflate_helper(oop obj) {
-markOop mark = obj->mark();
-if (mark->has_monitor()) {
-assert(ObjectSynchronizer::verify_objmon_isinpool(mark->monitor()), "monitor is invalid");
-assert(mark->monitor()->header()->is_neutral(), "monitor must record a good object header");
-return mark->monitor();
-}
-return ObjectSynchronizer::inflate(Thread::current(), obj);
-}
-// Note that we could encounter some performance loss through false-sharing as
-// multiple locks occupy the same $ line.  Padding might be appropriate.
-#define NINFLATIONLOCKS 256
-static volatile intptr_t InflationLocks [NINFLATIONLOCKS] ;
 static markOop ReadStableMark (oop obj) {
 markOop mark = obj->mark() ;
 if (!mark->is_being_inflated()) {
 return mark ;       // normal fast-path return
 SpinPause() ;       // SMP-polite spinning
 }
 }
 }
+// hashCode() generation :
+//
+// Possibilities:
+// * MD5Digest of {obj,stwRandom}
+// * CRC32 of {obj,stwRandom} or any linear-feedback shift register function.
+// * A DES- or AES-style SBox[] mechanism
+// * One of the Phi-based schemes, such as:
+//   2654435761 = 2^32 * Phi (golden ratio)
+//   HashCodeValue = ((uintptr_t(obj) >> 3) * 2654435761) ^ GVars.stwRandom ;
+// * A variation of Marsaglia's shift-xor RNG scheme.
+// * (obj ^ stwRandom) is appealing, but can result
+//   in undesirable regularity in the hashCode values of adjacent objects
+//   (objects allocated back-to-back, in particular).  This could potentially
+//   result in hashtable collisions and reduced hashtable efficiency.
+//   There are simple ways to "diffuse" the middle address bits over the
+//   generated hashCode values:
+//
+static inline intptr_t get_next_hash(Thread * Self, oop obj) {
+intptr_t value = 0 ;
+if (hashCode == 0) {
+// This form uses an unguarded global Park-Miller RNG,
+// so it's possible for two threads to race and generate the same RNG.
+// On MP system we'll have lots of RW access to a global, so the
+// mechanism induces lots of coherency traffic.
+value = os::random() ;
+} else
+if (hashCode == 1) {
+// This variation has the property of being stable (idempotent)
+// between STW operations.  This can be useful in some of the 1-0
+// synchronization schemes.
+intptr_t addrBits = intptr_t(obj) >> 3 ;
+value = addrBits ^ (addrBits >> 5) ^ GVars.stwRandom ;
+} else
+if (hashCode == 2) {
+value = 1 ;            // for sensitivity testing
+} else
+if (hashCode == 3) {
+value = ++GVars.hcSequence ;
+} else
+if (hashCode == 4) {
+value = intptr_t(obj) ;
+} else {
+// Marsaglia's xor-shift scheme with thread-specific state
+// This is probably the best overall implementation -- we'll
+// likely make this the default in future releases.
+unsigned t = Self->_hashStateX ;
+t ^= (t << 11) ;
+Self->_hashStateX = Self->_hashStateY ;
+Self->_hashStateY = Self->_hashStateZ ;
+Self->_hashStateZ = Self->_hashStateW ;
+unsigned v = Self->_hashStateW ;
+v = (v ^ (v >> 19)) ^ (t ^ (t >> 8)) ;
+Self->_hashStateW = v ;
+value = v ;
+}
+value &= markOopDesc::hash_mask;
+if (value == 0) value = 0xBAD ;
+assert (value != markOopDesc::no_hash, "invariant") ;
+TEVENT (hashCode: GENERATE) ;
+return value;
+}
+//
+intptr_t ObjectSynchronizer::FastHashCode (Thread * Self, oop obj) {
+if (UseBiasedLocking) {
+// NOTE: many places throughout the JVM do not expect a safepoint
+// to be taken here, in particular most operations on perm gen
+// objects. However, we only ever bias Java instances and all of
+// the call sites of identity_hash that might revoke biases have
+// been checked to make sure they can handle a safepoint. The
+// added check of the bias pattern is to avoid useless calls to
+// thread-local storage.
+if (obj->mark()->has_bias_pattern()) {
+// Box and unbox the raw reference just in case we cause a STW safepoint.
+Handle hobj (Self, obj) ;
+// Relaxing assertion for bug 6320749.
+assert (Universe::verify_in_progress() ||
+!SafepointSynchronize::is_at_safepoint(),
+"biases should not be seen by VM thread here");
+BiasedLocking::revoke_and_rebias(hobj, false, JavaThread::current());
+obj = hobj() ;
+assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+}
+// hashCode() is a heap mutator ...
+// Relaxing assertion for bug 6320749.
+assert (Universe::verify_in_progress() ||
+!SafepointSynchronize::is_at_safepoint(), "invariant") ;
+assert (Universe::verify_in_progress() ||
+Self->is_Java_thread() , "invariant") ;
+assert (Universe::verify_in_progress() ||
+((JavaThread *)Self)->thread_state() != _thread_blocked, "invariant") ;
+ObjectMonitor* monitor = NULL;
+markOop temp, test;
+intptr_t hash;
+markOop mark = ReadStableMark (obj);
+// object should remain ineligible for biased locking
+assert (!mark->has_bias_pattern(), "invariant") ;
+if (mark->is_neutral()) {
+hash = mark->hash();              // this is a normal header
+if (hash) {                       // if it has hash, just return it
+return hash;
+}
+hash = get_next_hash(Self, obj);  // allocate a new hash code
+temp = mark->copy_set_hash(hash); // merge the hash code into header
+// use (machine word version) atomic operation to install the hash
+test = (markOop) Atomic::cmpxchg_ptr(temp, obj->mark_addr(), mark);
+if (test == mark) {
+return hash;
+}
+// If atomic operation failed, we must inflate the header
+// into heavy weight monitor. We could add more code here
+// for fast path, but it does not worth the complexity.
+} else if (mark->has_monitor()) {
+monitor = mark->monitor();
+temp = monitor->header();
+assert (temp->is_neutral(), "invariant") ;
+hash = temp->hash();
+if (hash) {
+return hash;
+}
+// Skip to the following code to reduce code size
+} else if (Self->is_lock_owned((address)mark->locker())) {
+temp = mark->displaced_mark_helper(); // this is a lightweight monitor owned
+assert (temp->is_neutral(), "invariant") ;
+hash = temp->hash();              // by current thread, check if the displaced
+if (hash) {                       // header contains hash code
+return hash;
+}
+// WARNING:
+//   The displaced header is strictly immutable.
+// It can NOT be changed in ANY cases. So we have
+// to inflate the header into heavyweight monitor
+// even the current thread owns the lock. The reason
+// is the BasicLock (stack slot) will be asynchronously
+// read by other threads during the inflate() function.
+// Any change to stack may not propagate to other threads
+// correctly.
+}
+// Inflate the monitor to set hash code
+monitor = ObjectSynchronizer::inflate(Self, obj);
+// Load displaced header and check it has hash code
+mark = monitor->header();
+assert (mark->is_neutral(), "invariant") ;
+hash = mark->hash();
+if (hash == 0) {
+hash = get_next_hash(Self, obj);
+temp = mark->copy_set_hash(hash); // merge hash code into header
+assert (temp->is_neutral(), "invariant") ;
+test = (markOop) Atomic::cmpxchg_ptr(temp, monitor, mark);
+if (test != mark) {
+// The only update to the header in the monitor (outside GC)
+// is install the hash code. If someone add new usage of
+// displaced header, please update this code
+hash = test->hash();
+assert (test->is_neutral(), "invariant") ;
+assert (hash != 0, "Trivial unexpected object/monitor header usage.");
+}
+}
+// We finally get the hash
+return hash;
+}
+// Deprecated -- use FastHashCode() instead.
+intptr_t ObjectSynchronizer::identity_hash_value_for(Handle obj) {
+return FastHashCode (Thread::current(), obj()) ;
+}
+bool ObjectSynchronizer::current_thread_holds_lock(JavaThread* thread,
+Handle h_obj) {
+if (UseBiasedLocking) {
+BiasedLocking::revoke_and_rebias(h_obj, false, thread);
+assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+assert(thread == JavaThread::current(), "Can only be called on current thread");
+oop obj = h_obj();
+markOop mark = ReadStableMark (obj) ;
+// Uncontended case, header points to stack
+if (mark->has_locker()) {
+return thread->is_lock_owned((address)mark->locker());
+}
+// Contended case, header points to ObjectMonitor (tagged pointer)
+if (mark->has_monitor()) {
+ObjectMonitor* monitor = mark->monitor();
+return monitor->is_entered(thread) != 0 ;
+}
+// Unlocked case, header in place
+assert(mark->is_neutral(), "sanity check");
+return false;
+}
+// Be aware of this method could revoke bias of the lock object.
+// This method querys the ownership of the lock handle specified by 'h_obj'.
+// If the current thread owns the lock, it returns owner_self. If no
+// thread owns the lock, it returns owner_none. Otherwise, it will return
+// ower_other.
+ObjectSynchronizer::LockOwnership ObjectSynchronizer::query_lock_ownership
+(JavaThread *self, Handle h_obj) {
+// The caller must beware this method can revoke bias, and
+// revocation can result in a safepoint.
+assert (!SafepointSynchronize::is_at_safepoint(), "invariant") ;
+assert (self->thread_state() != _thread_blocked , "invariant") ;
+// Possible mark states: neutral, biased, stack-locked, inflated
+if (UseBiasedLocking && h_obj()->mark()->has_bias_pattern()) {
+// CASE: biased
+BiasedLocking::revoke_and_rebias(h_obj, false, self);
+assert(!h_obj->mark()->has_bias_pattern(),
+"biases should be revoked by now");
+}
+assert(self == JavaThread::current(), "Can only be called on current thread");
+oop obj = h_obj();
+markOop mark = ReadStableMark (obj) ;
+// CASE: stack-locked.  Mark points to a BasicLock on the owner's stack.
+if (mark->has_locker()) {
+return self->is_lock_owned((address)mark->locker()) ?
+owner_self : owner_other;
+}
+// CASE: inflated. Mark (tagged pointer) points to an objectMonitor.
+// The Object:ObjectMonitor relationship is stable as long as we're
+// not at a safepoint.
+if (mark->has_monitor()) {
+void * owner = mark->monitor()->_owner ;
+if (owner == NULL) return owner_none ;
+return (owner == self ||
+self->is_lock_owned((address)owner)) ? owner_self : owner_other;
+}
+// CASE: neutral
+assert(mark->is_neutral(), "sanity check");
+return owner_none ;           // it's unlocked
+}
+// FIXME: jvmti should call this
+JavaThread* ObjectSynchronizer::get_lock_owner(Handle h_obj, bool doLock) {
+if (UseBiasedLocking) {
+if (SafepointSynchronize::is_at_safepoint()) {
+BiasedLocking::revoke_at_safepoint(h_obj);
+} else {
+BiasedLocking::revoke_and_rebias(h_obj, false, JavaThread::current());
+}
+assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now");
+}
+oop obj = h_obj();
+address owner = NULL;
+markOop mark = ReadStableMark (obj) ;
+// Uncontended case, header points to stack
+if (mark->has_locker()) {
+owner = (address) mark->locker();
+}
+// Contended case, header points to ObjectMonitor (tagged pointer)
+if (mark->has_monitor()) {
+ObjectMonitor* monitor = mark->monitor();
+assert(monitor != NULL, "monitor should be non-null");
+owner = (address) monitor->owner();
+}
+if (owner != NULL) {
+return Threads::owning_thread_from_monitor_owner(owner, doLock);
+}
+// Unlocked case, header in place
+// Cannot have assertion since this object may have been
+// locked by another thread when reaching here.
+// assert(mark->is_neutral(), "sanity check");
+return NULL;
+}
+// Visitors ...
+void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure) {
+ObjectMonitor* block = gBlockList;
+ObjectMonitor* mid;
+while (block) {
+assert(block->object() == CHAINMARKER, "must be a block header");
+for (int i = _BLOCKSIZE - 1; i > 0; i--) {
+mid = block + i;
+oop object = (oop) mid->object();
+if (object != NULL) {
+closure->do_monitor(mid);
+}
+}
+block = (ObjectMonitor*) block->FreeNext;
+}
+}
+// Get the next block in the block list.
+static inline ObjectMonitor* next(ObjectMonitor* block) {
+assert(block->object() == CHAINMARKER, "must be a block header");
+block = block->FreeNext ;
+assert(block == NULL || block->object() == CHAINMARKER, "must be a block header");
+return block;
+}
+void ObjectSynchronizer::oops_do(OopClosure* f) {
+assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+for (ObjectMonitor* block = gBlockList; block != NULL; block = next(block)) {
+assert(block->object() == CHAINMARKER, "must be a block header");
+for (int i = 1; i < _BLOCKSIZE; i++) {
+ObjectMonitor* mid = &block[i];
+if (mid->object() != NULL) {
+f->do_oop((oop*)mid->object_addr());
+}
+}
+}
+}
+// -----------------------------------------------------------------------------
+// ObjectMonitor Lifecycle
+// -----------------------
+// Inflation unlinks monitors from the global gFreeList and
+// associates them with objects.  Deflation -- which occurs at
+// STW-time -- disassociates idle monitors from objects.  Such
+// scavenged monitors are returned to the gFreeList.
+//
+// The global list is protected by ListLock.  All the critical sections
+// are short and operate in constant-time.
+//
+// ObjectMonitors reside in type-stable memory (TSM) and are immortal.
+//
+// Lifecycle:
+// --   unassigned and on the global free list
+// --   unassigned and on a thread's private omFreeList
+// --   assigned to an object.  The object is inflated and the mark refers
+//      to the objectmonitor.
+//
+// Constraining monitor pool growth via MonitorBound ...
+//
+// The monitor pool is grow-only.  We scavenge at STW safepoint-time, but the
+// the rate of scavenging is driven primarily by GC.  As such,  we can find
+// an inordinate number of monitors in circulation.
+// To avoid that scenario we can artificially induce a STW safepoint
+// if the pool appears to be growing past some reasonable bound.
+// Generally we favor time in space-time tradeoffs, but as there's no
+// natural back-pressure on the # of extant monitors we need to impose some
+// type of limit.  Beware that if MonitorBound is set to too low a value
+// we could just loop. In addition, if MonitorBound is set to a low value
+// we'll incur more safepoints, which are harmful to performance.
+// See also: GuaranteedSafepointInterval
+//
+// The current implementation uses asynchronous VM operations.
+//
+static void InduceScavenge (Thread * Self, const char * Whence) {
+// Induce STW safepoint to trim monitors
+// Ultimately, this results in a call to deflate_idle_monitors() in the near future.
+// More precisely, trigger an asynchronous STW safepoint as the number
+// of active monitors passes the specified threshold.
+// TODO: assert thread state is reasonable
+if (ForceMonitorScavenge == 0 && Atomic::xchg (1, &ForceMonitorScavenge) == 0) {
+if (ObjectMonitor::Knob_Verbose) {
+::printf ("Monitor scavenge - Induced STW @%s (%d)\n", Whence, ForceMonitorScavenge) ;
+::fflush(stdout) ;
+}
+// Induce a 'null' safepoint to scavenge monitors
+// Must VM_Operation instance be heap allocated as the op will be enqueue and posted
+// to the VMthread and have a lifespan longer than that of this activation record.
+// The VMThread will delete the op when completed.
+VMThread::execute (new VM_ForceAsyncSafepoint()) ;
+if (ObjectMonitor::Knob_Verbose) {
+::printf ("Monitor scavenge - STW posted @%s (%d)\n", Whence, ForceMonitorScavenge) ;
+::fflush(stdout) ;
+}
+}
+}
+/* Too slow for general assert or debug
+void ObjectSynchronizer::verifyInUse (Thread *Self) {
+ObjectMonitor* mid;
+int inusetally = 0;
+for (mid = Self->omInUseList; mid != NULL; mid = mid->FreeNext) {
+inusetally ++;
+}
+assert(inusetally == Self->omInUseCount, "inuse count off");
+int freetally = 0;
+for (mid = Self->omFreeList; mid != NULL; mid = mid->FreeNext) {
+freetally ++;
+}
+assert(freetally == Self->omFreeCount, "free count off");
+}
+*/
+ObjectMonitor * ATTR ObjectSynchronizer::omAlloc (Thread * Self) {
+// A large MAXPRIVATE value reduces both list lock contention
+// and list coherency traffic, but also tends to increase the
+// number of objectMonitors in circulation as well as the STW
+// scavenge costs.  As usual, we lean toward time in space-time
+// tradeoffs.
+const int MAXPRIVATE = 1024 ;
+for (;;) {
+ObjectMonitor * m ;
+// 1: try to allocate from the thread's local omFreeList.
+// Threads will attempt to allocate first from their local list, then
+// from the global list, and only after those attempts fail will the thread
+// attempt to instantiate new monitors.   Thread-local free lists take
+// heat off the ListLock and improve allocation latency, as well as reducing
+// coherency traffic on the shared global list.
+m = Self->omFreeList ;
+if (m != NULL) {
+Self->omFreeList = m->FreeNext ;
+Self->omFreeCount -- ;
+// CONSIDER: set m->FreeNext = BAD -- diagnostic hygiene
+guarantee (m->object() == NULL, "invariant") ;
+if (MonitorInUseLists) {
+m->FreeNext = Self->omInUseList;
+Self->omInUseList = m;
+Self->omInUseCount ++;
+// verifyInUse(Self);
+} else {
+m->FreeNext = NULL;
+}
+return m ;
+}
+// 2: try to allocate from the global gFreeList
+// CONSIDER: use muxTry() instead of muxAcquire().
+// If the muxTry() fails then drop immediately into case 3.
+// If we're using thread-local free lists then try
+// to reprovision the caller's free list.
+if (gFreeList != NULL) {
+// Reprovision the thread's omFreeList.
+// Use bulk transfers to reduce the allocation rate and heat
+// on various locks.
+Thread::muxAcquire (&ListLock, "omAlloc") ;
+for (int i = Self->omFreeProvision; --i >= 0 && gFreeList != NULL; ) {
+MonitorFreeCount --;
+ObjectMonitor * take = gFreeList ;
+gFreeList = take->FreeNext ;
+guarantee (take->object() == NULL, "invariant") ;
+guarantee (!take->is_busy(), "invariant") ;
+take->Recycle() ;
+omRelease (Self, take, false) ;
+}
+Thread::muxRelease (&ListLock) ;
+Self->omFreeProvision += 1 + (Self->omFreeProvision/2) ;
+if (Self->omFreeProvision > MAXPRIVATE ) Self->omFreeProvision = MAXPRIVATE ;
+TEVENT (omFirst - reprovision) ;
+const int mx = MonitorBound ;
+if (mx > 0 && (MonitorPopulation-MonitorFreeCount) > mx) {
+// We can't safely induce a STW safepoint from omAlloc() as our thread
+// state may not be appropriate for such activities and callers may hold
+// naked oops, so instead we defer the action.
+InduceScavenge (Self, "omAlloc") ;
+}
+continue;
+}
+// 3: allocate a block of new ObjectMonitors
+// Both the local and global free lists are empty -- resort to malloc().
+// In the current implementation objectMonitors are TSM - immortal.
+assert (_BLOCKSIZE > 1, "invariant") ;
+ObjectMonitor * temp = new ObjectMonitor[_BLOCKSIZE];
+// NOTE: (almost) no way to recover if allocation failed.
+// We might be able to induce a STW safepoint and scavenge enough
+// objectMonitors to permit progress.
+if (temp == NULL) {
+vm_exit_out_of_memory (sizeof (ObjectMonitor[_BLOCKSIZE]), "Allocate ObjectMonitors") ;
+}
+// Format the block.
+// initialize the linked list, each monitor points to its next
+// forming the single linked free list, the very first monitor
+// will points to next block, which forms the block list.
+// The trick of using the 1st element in the block as gBlockList
+// linkage should be reconsidered.  A better implementation would
+// look like: class Block { Block * next; int N; ObjectMonitor Body [N] ; }
+for (int i = 1; i < _BLOCKSIZE ; i++) {
+temp[i].FreeNext = &temp[i+1];
+}
+// terminate the last monitor as the end of list
+temp[_BLOCKSIZE - 1].FreeNext = NULL ;
+// Element [0] is reserved for global list linkage
+temp[0].set_object(CHAINMARKER);
+// Consider carving out this thread's current request from the
+// block in hand.  This avoids some lock traffic and redundant
+// list activity.
+// Acquire the ListLock to manipulate BlockList and FreeList.
+// An Oyama-Taura-Yonezawa scheme might be more efficient.
+Thread::muxAcquire (&ListLock, "omAlloc [2]") ;
+MonitorPopulation += _BLOCKSIZE-1;
+MonitorFreeCount += _BLOCKSIZE-1;
+// Add the new block to the list of extant blocks (gBlockList).
+// The very first objectMonitor in a block is reserved and dedicated.
+// It serves as blocklist "next" linkage.
+temp[0].FreeNext = gBlockList;
+gBlockList = temp;
+// Add the new string of objectMonitors to the global free list
+temp[_BLOCKSIZE - 1].FreeNext = gFreeList ;
+gFreeList = temp + 1;
+Thread::muxRelease (&ListLock) ;
+TEVENT (Allocate block of monitors) ;
+}
+}
+// Place "m" on the caller's private per-thread omFreeList.
+// In practice there's no need to clamp or limit the number of
+// monitors on a thread's omFreeList as the only time we'll call
+// omRelease is to return a monitor to the free list after a CAS
+// attempt failed.  This doesn't allow unbounded #s of monitors to
+// accumulate on a thread's free list.
+//
+void ObjectSynchronizer::omRelease (Thread * Self, ObjectMonitor * m, bool fromPerThreadAlloc) {
+guarantee (m->object() == NULL, "invariant") ;
+// Remove from omInUseList
+if (MonitorInUseLists && fromPerThreadAlloc) {
+ObjectMonitor* curmidinuse = NULL;
+for (ObjectMonitor* mid = Self->omInUseList; mid != NULL; ) {
+if (m == mid) {
+// extract from per-thread in-use-list
+if (mid == Self->omInUseList) {
+Self->omInUseList = mid->FreeNext;
+} else if (curmidinuse != NULL) {
+curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist
+}
+Self->omInUseCount --;
+// verifyInUse(Self);
+break;
+} else {
+curmidinuse = mid;
+mid = mid->FreeNext;
+}
+}
+}
+// FreeNext is used for both onInUseList and omFreeList, so clear old before setting new
+m->FreeNext = Self->omFreeList ;
+Self->omFreeList = m ;
+Self->omFreeCount ++ ;
+}
+// Return the monitors of a moribund thread's local free list to
+// the global free list.  Typically a thread calls omFlush() when
+// it's dying.  We could also consider having the VM thread steal
+// monitors from threads that have not run java code over a few
+// consecutive STW safepoints.  Relatedly, we might decay
+// omFreeProvision at STW safepoints.
+//
+// Also return the monitors of a moribund thread"s omInUseList to
+// a global gOmInUseList under the global list lock so these
+// will continue to be scanned.
+//
+// We currently call omFlush() from the Thread:: dtor _after the thread
+// has been excised from the thread list and is no longer a mutator.
+// That means that omFlush() can run concurrently with a safepoint and
+// the scavenge operator.  Calling omFlush() from JavaThread::exit() might
+// be a better choice as we could safely reason that that the JVM is
+// not at a safepoint at the time of the call, and thus there could
+// be not inopportune interleavings between omFlush() and the scavenge
+// operator.
+void ObjectSynchronizer::omFlush (Thread * Self) {
+ObjectMonitor * List = Self->omFreeList ;  // Null-terminated SLL
+Self->omFreeList = NULL ;
+ObjectMonitor * Tail = NULL ;
+int Tally = 0;
+if (List != NULL) {
+ObjectMonitor * s ;
+for (s = List ; s != NULL ; s = s->FreeNext) {
+Tally ++ ;
+Tail = s ;
+guarantee (s->object() == NULL, "invariant") ;
+guarantee (!s->is_busy(), "invariant") ;
+s->set_owner (NULL) ;   // redundant but good hygiene
+TEVENT (omFlush - Move one) ;
+}
+guarantee (Tail != NULL && List != NULL, "invariant") ;
+}
+ObjectMonitor * InUseList = Self->omInUseList;
+ObjectMonitor * InUseTail = NULL ;
+int InUseTally = 0;
+if (InUseList != NULL) {
+Self->omInUseList = NULL;
+ObjectMonitor *curom;
+for (curom = InUseList; curom != NULL; curom = curom->FreeNext) {
+InUseTail = curom;
+InUseTally++;
+}
+// TODO debug
+assert(Self->omInUseCount == InUseTally, "inuse count off");
+Self->omInUseCount = 0;
+guarantee (InUseTail != NULL && InUseList != NULL, "invariant");
+}
+Thread::muxAcquire (&ListLock, "omFlush") ;
+if (Tail != NULL) {
+Tail->FreeNext = gFreeList ;
+gFreeList = List ;
+MonitorFreeCount += Tally;
+}
+if (InUseTail != NULL) {
+InUseTail->FreeNext = gOmInUseList;
+gOmInUseList = InUseList;
+gOmInUseCount += InUseTally;
+}
+Thread::muxRelease (&ListLock) ;
+TEVENT (omFlush) ;
+}
+// Fast path code shared by multiple functions
+ObjectMonitor* ObjectSynchronizer::inflate_helper(oop obj) {
+markOop mark = obj->mark();
+if (mark->has_monitor()) {
+assert(ObjectSynchronizer::verify_objmon_isinpool(mark->monitor()), "monitor is invalid");
+assert(mark->monitor()->header()->is_neutral(), "monitor must record a good object header");
+return mark->monitor();
+}
+return ObjectSynchronizer::inflate(Thread::current(), obj);
+}
+// Note that we could encounter some performance loss through false-sharing as
+// multiple locks occupy the same $ line.  Padding might be appropriate.
 ObjectMonitor * ATTR ObjectSynchronizer::inflate (Thread * Self, oop object) {
 // Inflate mutates the heap ...
 // Relaxing assertion for bug 6320749.
 assert (Universe::verify_in_progress() ||
 !SafepointSynchronize::is_at_safepoint(), "invariant") ;
 // in which INFLATING appears in the mark.
 m->Recycle();
 m->_Responsible  = NULL ;
 m->OwnerIsThread = 0 ;
 m->_recursions   = 0 ;
-m->_SpinDuration = Knob_SpinLimit ;   // Consider: maintain by type/class
+m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ;   // Consider: maintain by type/class
 markOop cmp = (markOop) Atomic::cmpxchg_ptr (markOopDesc::INFLATING(), object->mark_addr(), mark) ;
 if (cmp != mark) {
 omRelease (Self, m, true) ;
 continue ;       // Interference -- just retry
 guarantee (object->mark() == markOopDesc::INFLATING(), "invariant") ;
 object->release_set_mark(markOopDesc::encode(m));
 // Hopefully the performance counters are allocated on distinct cache lines
 // to avoid false sharing on MP systems ...
-if (_sync_Inflations != NULL) _sync_Inflations->inc() ;
+if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ;
 TEVENT(Inflate: overwrite stacklock) ;
 if (TraceMonitorInflation) {
 if (object->is_instance()) {
 ResourceMark rm;
 tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s",
 m->set_owner(NULL);
 m->set_object(object);
 m->OwnerIsThread = 1 ;
 m->_recursions   = 0 ;
 m->_Responsible  = NULL ;
-m->_SpinDuration = Knob_SpinLimit ;       // consider: keep metastats by type/class
+m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ;       // consider: keep metastats by type/class
 if (Atomic::cmpxchg_ptr (markOopDesc::encode(m), object->mark_addr(), mark) != mark) {
 m->set_object (NULL) ;
 m->set_owner  (NULL) ;
 m->OwnerIsThread = 0 ;
 // live-lock -- "Inflated" is an absorbing state.
 }
 // Hopefully the performance counters are allocated on distinct
 // cache lines to avoid false sharing on MP systems ...
-if (_sync_Inflations != NULL) _sync_Inflations->inc() ;
+if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ;
 TEVENT(Inflate: overwrite neutral) ;
 if (TraceMonitorInflation) {
 if (object->is_instance()) {
 ResourceMark rm;
 tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s",
 }
 return m ;
 }
 }
+// Note that we could encounter some performance loss through false-sharing as
-// This the fast monitor enter. The interpreter and compiler use
+// multiple locks occupy the same $ line.  Padding might be appropriate.
-// some assembly copies of this code. Make sure update those code
-// if the following function is changed. The implementation is
-// extremely sensitive to race condition. Be careful.
-void ObjectSynchronizer::fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias, TRAPS) {
-if (UseBiasedLocking) {
-if (!SafepointSynchronize::is_at_safepoint()) {
-BiasedLocking::Condition cond = BiasedLocking::revoke_and_rebias(obj, attempt_rebias, THREAD);
-if (cond == BiasedLocking::BIAS_REVOKED_AND_REBIASED) {
-return;
-}
-} else {
-assert(!attempt_rebias, "can not rebias toward VM thread");
-BiasedLocking::revoke_at_safepoint(obj);
-}
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-slow_enter (obj, lock, THREAD) ;
-}
-void ObjectSynchronizer::fast_exit(oop object, BasicLock* lock, TRAPS) {
-assert(!object->mark()->has_bias_pattern(), "should not see bias pattern here");
-// if displaced header is null, the previous enter is recursive enter, no-op
-markOop dhw = lock->displaced_header();
-markOop mark ;
-if (dhw == NULL) {
-// Recursive stack-lock.
-// Diagnostics -- Could be: stack-locked, inflating, inflated.
-mark = object->mark() ;
-assert (!mark->is_neutral(), "invariant") ;
-if (mark->has_locker() && mark != markOopDesc::INFLATING()) {
-assert(THREAD->is_lock_owned((address)mark->locker()), "invariant") ;
-}
-if (mark->has_monitor()) {
-ObjectMonitor * m = mark->monitor() ;
-assert(((oop)(m->object()))->mark() == mark, "invariant") ;
-assert(m->is_entered(THREAD), "invariant") ;
-}
-return ;
-}
-mark = object->mark() ;
-// If the object is stack-locked by the current thread, try to
-// swing the displaced header from the box back to the mark.
-if (mark == (markOop) lock) {
-assert (dhw->is_neutral(), "invariant") ;
-if ((markOop) Atomic::cmpxchg_ptr (dhw, object->mark_addr(), mark) == mark) {
-TEVENT (fast_exit: release stacklock) ;
-return;
-}
-}
-ObjectSynchronizer::inflate(THREAD, object)->exit (THREAD) ;
-}
-// This routine is used to handle interpreter/compiler slow case
-// We don't need to use fast path here, because it must have been
-// failed in the interpreter/compiler code.
-void ObjectSynchronizer::slow_enter(Handle obj, BasicLock* lock, TRAPS) {
-markOop mark = obj->mark();
-assert(!mark->has_bias_pattern(), "should not see bias pattern here");
-if (mark->is_neutral()) {
-// Anticipate successful CAS -- the ST of the displaced mark must
-// be visible <= the ST performed by the CAS.
-lock->set_displaced_header(mark);
-if (mark == (markOop) Atomic::cmpxchg_ptr(lock, obj()->mark_addr(), mark)) {
-TEVENT (slow_enter: release stacklock) ;
-return ;
-}
-// Fall through to inflate() ...
-} else
-if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) {
-assert(lock != mark->locker(), "must not re-lock the same lock");
-assert(lock != (BasicLock*)obj->mark(), "don't relock with same BasicLock");
-lock->set_displaced_header(NULL);
-return;
-}
-#if 0
-// The following optimization isn't particularly useful.
-if (mark->has_monitor() && mark->monitor()->is_entered(THREAD)) {
-lock->set_displaced_header (NULL) ;
-return ;
-}
-#endif
-// The object header will never be displaced to this lock,
-// so it does not matter what the value is, except that it
-// must be non-zero to avoid looking like a re-entrant lock,
-// and must not look locked either.
-lock->set_displaced_header(markOopDesc::unused_mark());
-ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD);
-}
-// This routine is used to handle interpreter/compiler slow case
-// We don't need to use fast path here, because it must have
-// failed in the interpreter/compiler code. Simply use the heavy
-// weight monitor should be ok, unless someone find otherwise.
-void ObjectSynchronizer::slow_exit(oop object, BasicLock* lock, TRAPS) {
-fast_exit (object, lock, THREAD) ;
-}
-// NOTE: must use heavy weight monitor to handle jni monitor enter
-void ObjectSynchronizer::jni_enter(Handle obj, TRAPS) { // possible entry from jni enter
-// the current locking is from JNI instead of Java code
-TEVENT (jni_enter) ;
-if (UseBiasedLocking) {
-BiasedLocking::revoke_and_rebias(obj, false, THREAD);
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-THREAD->set_current_pending_monitor_is_from_java(false);
-ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD);
-THREAD->set_current_pending_monitor_is_from_java(true);
-}
-// NOTE: must use heavy weight monitor to handle jni monitor enter
-bool ObjectSynchronizer::jni_try_enter(Handle obj, Thread* THREAD) {
-if (UseBiasedLocking) {
-BiasedLocking::revoke_and_rebias(obj, false, THREAD);
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-ObjectMonitor* monitor = ObjectSynchronizer::inflate_helper(obj());
-return monitor->try_enter(THREAD);
-}
-// NOTE: must use heavy weight monitor to handle jni monitor exit
-void ObjectSynchronizer::jni_exit(oop obj, Thread* THREAD) {
-TEVENT (jni_exit) ;
-if (UseBiasedLocking) {
-BiasedLocking::revoke_and_rebias(obj, false, THREAD);
-}
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj);
-// If this thread has locked the object, exit the monitor.  Note:  can't use
-// monitor->check(CHECK); must exit even if an exception is pending.
-if (monitor->check(THREAD)) {
-monitor->exit(THREAD);
-}
-}
-// complete_exit()/reenter() are used to wait on a nested lock
-// i.e. to give up an outer lock completely and then re-enter
-// Used when holding nested locks - lock acquisition order: lock1 then lock2
-//  1) complete_exit lock1 - saving recursion count
-//  2) wait on lock2
-//  3) when notified on lock2, unlock lock2
-//  4) reenter lock1 with original recursion count
-//  5) lock lock2
-// NOTE: must use heavy weight monitor to handle complete_exit/reenter()
-intptr_t ObjectSynchronizer::complete_exit(Handle obj, TRAPS) {
-TEVENT (complete_exit) ;
-if (UseBiasedLocking) {
-BiasedLocking::revoke_and_rebias(obj, false, THREAD);
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj());
-return monitor->complete_exit(THREAD);
-}
-// NOTE: must use heavy weight monitor to handle complete_exit/reenter()
-void ObjectSynchronizer::reenter(Handle obj, intptr_t recursion, TRAPS) {
-TEVENT (reenter) ;
-if (UseBiasedLocking) {
-BiasedLocking::revoke_and_rebias(obj, false, THREAD);
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj());
-monitor->reenter(recursion, THREAD);
-}
-// This exists only as a workaround of dtrace bug 6254741
-int dtrace_waited_probe(ObjectMonitor* monitor, Handle obj, Thread* thr) {
-DTRACE_MONITOR_PROBE(waited, monitor, obj(), thr);
-return 0;
-}
-// NOTE: must use heavy weight monitor to handle wait()
-void ObjectSynchronizer::wait(Handle obj, jlong millis, TRAPS) {
-if (UseBiasedLocking) {
-BiasedLocking::revoke_and_rebias(obj, false, THREAD);
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-if (millis < 0) {
-TEVENT (wait - throw IAX) ;
-THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative");
-}
-ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj());
-DTRACE_MONITOR_WAIT_PROBE(monitor, obj(), THREAD, millis);
-monitor->wait(millis, true, THREAD);
-/* This dummy call is in place to get around dtrace bug 6254741.  Once
-that's fixed we can uncomment the following line and remove the call */
-// DTRACE_MONITOR_PROBE(waited, monitor, obj(), THREAD);
-dtrace_waited_probe(monitor, obj, THREAD);
-}
-void ObjectSynchronizer::waitUninterruptibly (Handle obj, jlong millis, TRAPS) {
-if (UseBiasedLocking) {
-BiasedLocking::revoke_and_rebias(obj, false, THREAD);
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-if (millis < 0) {
-TEVENT (wait - throw IAX) ;
-THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative");
-}
-ObjectSynchronizer::inflate(THREAD, obj()) -> wait(millis, false, THREAD) ;
-}
-void ObjectSynchronizer::notify(Handle obj, TRAPS) {
-if (UseBiasedLocking) {
-BiasedLocking::revoke_and_rebias(obj, false, THREAD);
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-markOop mark = obj->mark();
-if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) {
-return;
-}
-ObjectSynchronizer::inflate(THREAD, obj())->notify(THREAD);
-}
-// NOTE: see comment of notify()
-void ObjectSynchronizer::notifyall(Handle obj, TRAPS) {
-if (UseBiasedLocking) {
-BiasedLocking::revoke_and_rebias(obj, false, THREAD);
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-markOop mark = obj->mark();
-if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) {
-return;
-}
-ObjectSynchronizer::inflate(THREAD, obj())->notifyAll(THREAD);
-}
-intptr_t ObjectSynchronizer::FastHashCode (Thread * Self, oop obj) {
-if (UseBiasedLocking) {
-// NOTE: many places throughout the JVM do not expect a safepoint
-// to be taken here, in particular most operations on perm gen
-// objects. However, we only ever bias Java instances and all of
-// the call sites of identity_hash that might revoke biases have
-// been checked to make sure they can handle a safepoint. The
-// added check of the bias pattern is to avoid useless calls to
-// thread-local storage.
-if (obj->mark()->has_bias_pattern()) {
-// Box and unbox the raw reference just in case we cause a STW safepoint.
-Handle hobj (Self, obj) ;
-// Relaxing assertion for bug 6320749.
-assert (Universe::verify_in_progress() ||
-!SafepointSynchronize::is_at_safepoint(),
-"biases should not be seen by VM thread here");
-BiasedLocking::revoke_and_rebias(hobj, false, JavaThread::current());
-obj = hobj() ;
-assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-}
-// hashCode() is a heap mutator ...
-// Relaxing assertion for bug 6320749.
-assert (Universe::verify_in_progress() ||
-!SafepointSynchronize::is_at_safepoint(), "invariant") ;
-assert (Universe::verify_in_progress() ||
-Self->is_Java_thread() , "invariant") ;
-assert (Universe::verify_in_progress() ||
-((JavaThread *)Self)->thread_state() != _thread_blocked, "invariant") ;
-ObjectMonitor* monitor = NULL;
-markOop temp, test;
-intptr_t hash;
-markOop mark = ReadStableMark (obj);
-// object should remain ineligible for biased locking
-assert (!mark->has_bias_pattern(), "invariant") ;
-if (mark->is_neutral()) {
-hash = mark->hash();              // this is a normal header
-if (hash) {                       // if it has hash, just return it
-return hash;
-}
-hash = get_next_hash(Self, obj);  // allocate a new hash code
-temp = mark->copy_set_hash(hash); // merge the hash code into header
-// use (machine word version) atomic operation to install the hash
-test = (markOop) Atomic::cmpxchg_ptr(temp, obj->mark_addr(), mark);
-if (test == mark) {
-return hash;
-}
-// If atomic operation failed, we must inflate the header
-// into heavy weight monitor. We could add more code here
-// for fast path, but it does not worth the complexity.
-} else if (mark->has_monitor()) {
-monitor = mark->monitor();
-temp = monitor->header();
-assert (temp->is_neutral(), "invariant") ;
-hash = temp->hash();
-if (hash) {
-return hash;
-}
-// Skip to the following code to reduce code size
-} else if (Self->is_lock_owned((address)mark->locker())) {
-temp = mark->displaced_mark_helper(); // this is a lightweight monitor owned
-assert (temp->is_neutral(), "invariant") ;
-hash = temp->hash();              // by current thread, check if the displaced
-if (hash) {                       // header contains hash code
-return hash;
-}
-// WARNING:
-//   The displaced header is strictly immutable.
-// It can NOT be changed in ANY cases. So we have
-// to inflate the header into heavyweight monitor
-// even the current thread owns the lock. The reason
-// is the BasicLock (stack slot) will be asynchronously
-// read by other threads during the inflate() function.
-// Any change to stack may not propagate to other threads
-// correctly.
-}
-// Inflate the monitor to set hash code
-monitor = ObjectSynchronizer::inflate(Self, obj);
-// Load displaced header and check it has hash code
-mark = monitor->header();
-assert (mark->is_neutral(), "invariant") ;
-hash = mark->hash();
-if (hash == 0) {
-hash = get_next_hash(Self, obj);
-temp = mark->copy_set_hash(hash); // merge hash code into header
-assert (temp->is_neutral(), "invariant") ;
-test = (markOop) Atomic::cmpxchg_ptr(temp, monitor, mark);
-if (test != mark) {
-// The only update to the header in the monitor (outside GC)
-// is install the hash code. If someone add new usage of
-// displaced header, please update this code
-hash = test->hash();
-assert (test->is_neutral(), "invariant") ;
-assert (hash != 0, "Trivial unexpected object/monitor header usage.");
-}
-}
-// We finally get the hash
-return hash;
-}
-// Deprecated -- use FastHashCode() instead.
-intptr_t ObjectSynchronizer::identity_hash_value_for(Handle obj) {
-return FastHashCode (Thread::current(), obj()) ;
-}
-bool ObjectSynchronizer::current_thread_holds_lock(JavaThread* thread,
-Handle h_obj) {
-if (UseBiasedLocking) {
-BiasedLocking::revoke_and_rebias(h_obj, false, thread);
-assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-assert(thread == JavaThread::current(), "Can only be called on current thread");
-oop obj = h_obj();
-markOop mark = ReadStableMark (obj) ;
-// Uncontended case, header points to stack
-if (mark->has_locker()) {
-return thread->is_lock_owned((address)mark->locker());
-}
-// Contended case, header points to ObjectMonitor (tagged pointer)
-if (mark->has_monitor()) {
-ObjectMonitor* monitor = mark->monitor();
-return monitor->is_entered(thread) != 0 ;
-}
-// Unlocked case, header in place
-assert(mark->is_neutral(), "sanity check");
-return false;
-}
-// Be aware of this method could revoke bias of the lock object.
-// This method querys the ownership of the lock handle specified by 'h_obj'.
-// If the current thread owns the lock, it returns owner_self. If no
-// thread owns the lock, it returns owner_none. Otherwise, it will return
-// ower_other.
-ObjectSynchronizer::LockOwnership ObjectSynchronizer::query_lock_ownership
-(JavaThread *self, Handle h_obj) {
-// The caller must beware this method can revoke bias, and
-// revocation can result in a safepoint.
-assert (!SafepointSynchronize::is_at_safepoint(), "invariant") ;
-assert (self->thread_state() != _thread_blocked , "invariant") ;
-// Possible mark states: neutral, biased, stack-locked, inflated
-if (UseBiasedLocking && h_obj()->mark()->has_bias_pattern()) {
-// CASE: biased
-BiasedLocking::revoke_and_rebias(h_obj, false, self);
-assert(!h_obj->mark()->has_bias_pattern(),
-"biases should be revoked by now");
-}
-assert(self == JavaThread::current(), "Can only be called on current thread");
-oop obj = h_obj();
-markOop mark = ReadStableMark (obj) ;
-// CASE: stack-locked.  Mark points to a BasicLock on the owner's stack.
-if (mark->has_locker()) {
-return self->is_lock_owned((address)mark->locker()) ?
-owner_self : owner_other;
-}
-// CASE: inflated. Mark (tagged pointer) points to an objectMonitor.
-// The Object:ObjectMonitor relationship is stable as long as we're
-// not at a safepoint.
-if (mark->has_monitor()) {
-void * owner = mark->monitor()->_owner ;
-if (owner == NULL) return owner_none ;
-return (owner == self ||
-self->is_lock_owned((address)owner)) ? owner_self : owner_other;
-}
-// CASE: neutral
-assert(mark->is_neutral(), "sanity check");
-return owner_none ;           // it's unlocked
-}
-// FIXME: jvmti should call this
-JavaThread* ObjectSynchronizer::get_lock_owner(Handle h_obj, bool doLock) {
-if (UseBiasedLocking) {
-if (SafepointSynchronize::is_at_safepoint()) {
-BiasedLocking::revoke_at_safepoint(h_obj);
-} else {
-BiasedLocking::revoke_and_rebias(h_obj, false, JavaThread::current());
-}
-assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now");
-}
-oop obj = h_obj();
-address owner = NULL;
-markOop mark = ReadStableMark (obj) ;
-// Uncontended case, header points to stack
-if (mark->has_locker()) {
-owner = (address) mark->locker();
-}
-// Contended case, header points to ObjectMonitor (tagged pointer)
-if (mark->has_monitor()) {
-ObjectMonitor* monitor = mark->monitor();
-assert(monitor != NULL, "monitor should be non-null");
-owner = (address) monitor->owner();
-}
-if (owner != NULL) {
-return Threads::owning_thread_from_monitor_owner(owner, doLock);
-}
-// Unlocked case, header in place
-// Cannot have assertion since this object may have been
-// locked by another thread when reaching here.
-// assert(mark->is_neutral(), "sanity check");
-return NULL;
-}
-// Iterate through monitor cache and attempt to release thread's monitors
-// Gives up on a particular monitor if an exception occurs, but continues
-// the overall iteration, swallowing the exception.
-class ReleaseJavaMonitorsClosure: public MonitorClosure {
-private:
-TRAPS;
-public:
-ReleaseJavaMonitorsClosure(Thread* thread) : THREAD(thread) {}
-void do_monitor(ObjectMonitor* mid) {
-if (mid->owner() == THREAD) {
-(void)mid->complete_exit(CHECK);
-}
-}
-};
-// Release all inflated monitors owned by THREAD.  Lightweight monitors are
-// ignored.  This is meant to be called during JNI thread detach which assumes
-// all remaining monitors are heavyweight.  All exceptions are swallowed.
-// Scanning the extant monitor list can be time consuming.
-// A simple optimization is to add a per-thread flag that indicates a thread
-// called jni_monitorenter() during its lifetime.
-//
-// Instead of No_Savepoint_Verifier it might be cheaper to
-// use an idiom of the form:
-//   auto int tmp = SafepointSynchronize::_safepoint_counter ;
-//   <code that must not run at safepoint>
-//   guarantee (((tmp ^ _safepoint_counter) | (tmp & 1)) == 0) ;
-// Since the tests are extremely cheap we could leave them enabled
-// for normal product builds.
-void ObjectSynchronizer::release_monitors_owned_by_thread(TRAPS) {
-assert(THREAD == JavaThread::current(), "must be current Java thread");
-No_Safepoint_Verifier nsv ;
-ReleaseJavaMonitorsClosure rjmc(THREAD);
-Thread::muxAcquire(&ListLock, "release_monitors_owned_by_thread");
-ObjectSynchronizer::monitors_iterate(&rjmc);
-Thread::muxRelease(&ListLock);
-THREAD->clear_pending_exception();
-}
-// Visitors ...
-void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure) {
-ObjectMonitor* block = gBlockList;
-ObjectMonitor* mid;
-while (block) {
-assert(block->object() == CHAINMARKER, "must be a block header");
-for (int i = _BLOCKSIZE - 1; i > 0; i--) {
-mid = block + i;
-oop object = (oop) mid->object();
-if (object != NULL) {
-closure->do_monitor(mid);
-}
-}
-block = (ObjectMonitor*) block->FreeNext;
-}
-}
-void ObjectSynchronizer::oops_do(OopClosure* f) {
-assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
-for (ObjectMonitor* block = gBlockList; block != NULL; block = next(block)) {
-assert(block->object() == CHAINMARKER, "must be a block header");
-for (int i = 1; i < _BLOCKSIZE; i++) {
-ObjectMonitor* mid = &block[i];
-if (mid->object() != NULL) {
-f->do_oop((oop*)mid->object_addr());
-}
-}
-}
-}
 // Deflate_idle_monitors() is called at all safepoints, immediately
 // after all mutators are stopped, but before any objects have moved.
 // It traverses the list of known monitors, deflating where possible.
 // The scavenged monitor are returned to the monitor free list.
 // Perversely, the heap size -- and thus the STW safepoint rate --
 // typically drives the scavenge rate.  Large heaps can mean infrequent GC,
 // which in turn can mean large(r) numbers of objectmonitors in circulation.
 // This is an unfortunate aspect of this design.
 //
-// Another refinement would be to refrain from calling deflate_idle_monitors()
-// except at stop-the-world points associated with garbage collections.
+enum ManifestConstants {
-//
+ClearResponsibleAtSTW   = 0,
-// An even better solution would be to deflate on-the-fly, aggressively,
+MaximumRecheckInterval  = 1000
-// at monitorexit-time as is done in EVM's metalock or Relaxed Locks.
+} ;
 // Deflate a single monitor if not in use
 // Return true if deflated, false if in use
 bool ObjectSynchronizer::deflate_monitor(ObjectMonitor* mid, oop obj,
 ObjectMonitor** FreeHeadp, ObjectMonitor** FreeTailp) {
 MonitorFreeCount += nScavenged;
 // Consider: audit gFreeList to ensure that MonitorFreeCount and list agree.
-if (Knob_Verbose) {
+if (ObjectMonitor::Knob_Verbose) {
 ::printf ("Deflate: InCirc=%d InUse=%d Scavenged=%d ForceMonitorScavenge=%d : pop=%d free=%d\n",
 nInCirculation, nInuse, nScavenged, ForceMonitorScavenge,
 MonitorPopulation, MonitorFreeCount) ;
 ::fflush(stdout) ;
 }
 FreeTail->FreeNext = gFreeList ;
 gFreeList = FreeHead ;
 }
 Thread::muxRelease (&ListLock) ;
-if (_sync_Deflations != NULL) _sync_Deflations->inc(nScavenged) ;
+if (ObjectMonitor::_sync_Deflations != NULL) ObjectMonitor::_sync_Deflations->inc(nScavenged) ;
-if (_sync_MonExtant  != NULL) _sync_MonExtant ->set_value(nInCirculation);
+if (ObjectMonitor::_sync_MonExtant  != NULL) ObjectMonitor::_sync_MonExtant ->set_value(nInCirculation);
 // TODO: Add objectMonitor leak detection.
 // Audit/inventory the objectMonitors -- make sure they're all accounted for.
 GVars.stwRandom = os::random() ;
 GVars.stwCycle ++ ;
 }
-// A macro is used below because there may already be a pending
+// Monitor cleanup on JavaThread::exit
-// exception which should not abort the execution of the routines
-// which use this (which is why we don't put this into check_slow and
+// Iterate through monitor cache and attempt to release thread's monitors
-// call it with a CHECK argument).
+// Gives up on a particular monitor if an exception occurs, but continues
+// the overall iteration, swallowing the exception.
-#define CHECK_OWNER()                                                             \
+class ReleaseJavaMonitorsClosure: public MonitorClosure {
-do {                                                                            \
+private:
-if (THREAD != _owner) {                                                       \
+TRAPS;
-if (THREAD->is_lock_owned((address) _owner)) {                              \
-_owner = THREAD ;  /* Convert from basiclock addr to Thread addr */       \
+public:
-_recursions = 0;                                                          \
+ReleaseJavaMonitorsClosure(Thread* thread) : THREAD(thread) {}
-OwnerIsThread = 1 ;                                                       \
+void do_monitor(ObjectMonitor* mid) {
-} else {                                                                    \
+if (mid->owner() == THREAD) {
-TEVENT (Throw IMSX) ;                                                     \
+(void)mid->complete_exit(CHECK);
-THROW(vmSymbols::java_lang_IllegalMonitorStateException());               \
+}
-}                                                                           \
+}
-}                                                                             \
+};
-} while (false)
+// Release all inflated monitors owned by THREAD.  Lightweight monitors are
-// TODO-FIXME: eliminate ObjectWaiters.  Replace this visitor/enumerator
+// ignored.  This is meant to be called during JNI thread detach which assumes
-// interface with a simple FirstWaitingThread(), NextWaitingThread() interface.
+// all remaining monitors are heavyweight.  All exceptions are swallowed.
+// Scanning the extant monitor list can be time consuming.
-ObjectWaiter* ObjectMonitor::first_waiter() {
+// A simple optimization is to add a per-thread flag that indicates a thread
-return _WaitSet;
+// called jni_monitorenter() during its lifetime.
-}
+//
+// Instead of No_Savepoint_Verifier it might be cheaper to
-ObjectWaiter* ObjectMonitor::next_waiter(ObjectWaiter* o) {
+// use an idiom of the form:
-return o->_next;
+//   auto int tmp = SafepointSynchronize::_safepoint_counter ;
-}
+//   <code that must not run at safepoint>
+//   guarantee (((tmp ^ _safepoint_counter) | (tmp & 1)) == 0) ;
-Thread* ObjectMonitor::thread_of_waiter(ObjectWaiter* o) {
+// Since the tests are extremely cheap we could leave them enabled
-return o->_thread;
+// for normal product builds.
-}
+void ObjectSynchronizer::release_monitors_owned_by_thread(TRAPS) {
-// initialize the monitor, exception the semaphore, all other fields
+assert(THREAD == JavaThread::current(), "must be current Java thread");
-// are simple integers or pointers
+No_Safepoint_Verifier nsv ;
-ObjectMonitor::ObjectMonitor() {
+ReleaseJavaMonitorsClosure rjmc(THREAD);
-_header       = NULL;
+Thread::muxAcquire(&ListLock, "release_monitors_owned_by_thread");
-_count        = 0;
+ObjectSynchronizer::monitors_iterate(&rjmc);
-_waiters      = 0,
+Thread::muxRelease(&ListLock);
-_recursions   = 0;
+THREAD->clear_pending_exception();
-_object       = NULL;
+}
-_owner        = NULL;
-_WaitSet      = NULL;
-_WaitSetLock  = 0 ;
-_Responsible  = NULL ;
-_succ         = NULL ;
-_cxq          = NULL ;
-FreeNext      = NULL ;
-_EntryList    = NULL ;
-_SpinFreq     = 0 ;
-_SpinClock    = 0 ;
-OwnerIsThread = 0 ;
-}
-ObjectMonitor::~ObjectMonitor() {
-// TODO: Add asserts ...
-// _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
-// _count == 0 _EntryList  == NULL etc
-}
-intptr_t ObjectMonitor::is_busy() const {
-// TODO-FIXME: merge _count and _waiters.
-// TODO-FIXME: assert _owner == null implies _recursions = 0
-// TODO-FIXME: assert _WaitSet != null implies _count > 0
-return _count|_waiters|intptr_t(_owner)|intptr_t(_cxq)|intptr_t(_EntryList ) ;
-}
-void ObjectMonitor::Recycle () {
-// TODO: add stronger asserts ...
-// _cxq == 0 _succ == NULL _owner == NULL _waiters == 0
-// _count == 0 EntryList  == NULL
-// _recursions == 0 _WaitSet == NULL
-// TODO: assert (is_busy()|_recursions) == 0
-_succ          = NULL ;
-_EntryList     = NULL ;
-_cxq           = NULL ;
-_WaitSet       = NULL ;
-_recursions    = 0 ;
-_SpinFreq      = 0 ;
-_SpinClock     = 0 ;
-OwnerIsThread  = 0 ;
-}
-// WaitSet management ...
-inline void ObjectMonitor::AddWaiter(ObjectWaiter* node) {
-assert(node != NULL, "should not dequeue NULL node");
-assert(node->_prev == NULL, "node already in list");
-assert(node->_next == NULL, "node already in list");
-// put node at end of queue (circular doubly linked list)
-if (_WaitSet == NULL) {
-_WaitSet = node;
-node->_prev = node;
-node->_next = node;
-} else {
-ObjectWaiter* head = _WaitSet ;
-ObjectWaiter* tail = head->_prev;
-assert(tail->_next == head, "invariant check");
-tail->_next = node;
-head->_prev = node;
-node->_next = head;
-node->_prev = tail;
-}
-}
-inline ObjectWaiter* ObjectMonitor::DequeueWaiter() {
-// dequeue the very first waiter
-ObjectWaiter* waiter = _WaitSet;
-if (waiter) {
-DequeueSpecificWaiter(waiter);
-}
-return waiter;
-}
-inline void ObjectMonitor::DequeueSpecificWaiter(ObjectWaiter* node) {
-assert(node != NULL, "should not dequeue NULL node");
-assert(node->_prev != NULL, "node already removed from list");
-assert(node->_next != NULL, "node already removed from list");
-// when the waiter has woken up because of interrupt,
-// timeout or other spurious wake-up, dequeue the
-// waiter from waiting list
-ObjectWaiter* next = node->_next;
-if (next == node) {
-assert(node->_prev == node, "invariant check");
-_WaitSet = NULL;
-} else {
-ObjectWaiter* prev = node->_prev;
-assert(prev->_next == node, "invariant check");
-assert(next->_prev == node, "invariant check");
-next->_prev = prev;
-prev->_next = next;
-if (_WaitSet == node) {
-_WaitSet = next;
-}
-}
-node->_next = NULL;
-node->_prev = NULL;
-}
-static char * kvGet (char * kvList, const char * Key) {
-if (kvList == NULL) return NULL ;
-size_t n = strlen (Key) ;
-char * Search ;
-for (Search = kvList ; *Search ; Search += strlen(Search) + 1) {
-if (strncmp (Search, Key, n) == 0) {
-if (Search[n] == '=') return Search + n + 1 ;
-if (Search[n] == 0)   return (char *) "1" ;
-}
-}
-return NULL ;
-}
-static int kvGetInt (char * kvList, const char * Key, int Default) {
-char * v = kvGet (kvList, Key) ;
-int rslt = v ? ::strtol (v, NULL, 0) : Default ;
-if (Knob_ReportSettings && v != NULL) {
-::printf ("  SyncKnob: %s %d(%d)\n", Key, rslt, Default) ;
-::fflush (stdout) ;
-}
-return rslt ;
-}
-// By convention we unlink a contending thread from EntryList|cxq immediately
-// after the thread acquires the lock in ::enter().  Equally, we could defer
-// unlinking the thread until ::exit()-time.
-void ObjectMonitor::UnlinkAfterAcquire (Thread * Self, ObjectWaiter * SelfNode)
-{
-assert (_owner == Self, "invariant") ;
-assert (SelfNode->_thread == Self, "invariant") ;
-if (SelfNode->TState == ObjectWaiter::TS_ENTER) {
-// Normal case: remove Self from the DLL EntryList .
-// This is a constant-time operation.
-ObjectWaiter * nxt = SelfNode->_next ;
-ObjectWaiter * prv = SelfNode->_prev ;
-if (nxt != NULL) nxt->_prev = prv ;
-if (prv != NULL) prv->_next = nxt ;
-if (SelfNode == _EntryList ) _EntryList = nxt ;
-assert (nxt == NULL || nxt->TState == ObjectWaiter::TS_ENTER, "invariant") ;
-assert (prv == NULL || prv->TState == ObjectWaiter::TS_ENTER, "invariant") ;
-TEVENT (Unlink from EntryList) ;
-} else {
-guarantee (SelfNode->TState == ObjectWaiter::TS_CXQ, "invariant") ;
-// Inopportune interleaving -- Self is still on the cxq.
-// This usually means the enqueue of self raced an exiting thread.
-// Normally we'll find Self near the front of the cxq, so
-// dequeueing is typically fast.  If needbe we can accelerate
-// this with some MCS/CHL-like bidirectional list hints and advisory
-// back-links so dequeueing from the interior will normally operate
-// in constant-time.
-// Dequeue Self from either the head (with CAS) or from the interior
-// with a linear-time scan and normal non-atomic memory operations.
-// CONSIDER: if Self is on the cxq then simply drain cxq into EntryList
-// and then unlink Self from EntryList.  We have to drain eventually,
-// so it might as well be now.
-ObjectWaiter * v = _cxq ;
-assert (v != NULL, "invariant") ;
-if (v != SelfNode || Atomic::cmpxchg_ptr (SelfNode->_next, &_cxq, v) != v) {
-// The CAS above can fail from interference IFF a "RAT" arrived.
-// In that case Self must be in the interior and can no longer be
-// at the head of cxq.
-if (v == SelfNode) {
-assert (_cxq != v, "invariant") ;
-v = _cxq ;          // CAS above failed - start scan at head of list
-}
-ObjectWaiter * p ;
-ObjectWaiter * q = NULL ;
-for (p = v ; p != NULL && p != SelfNode; p = p->_next) {
-q = p ;
-assert (p->TState == ObjectWaiter::TS_CXQ, "invariant") ;
-}
-assert (v != SelfNode,  "invariant") ;
-assert (p == SelfNode,  "Node not found on cxq") ;
-assert (p != _cxq,      "invariant") ;
-assert (q != NULL,      "invariant") ;
-assert (q->_next == p,  "invariant") ;
-q->_next = p->_next ;
-}
-TEVENT (Unlink from cxq) ;
-}
-// Diagnostic hygiene ...
-SelfNode->_prev  = (ObjectWaiter *) 0xBAD ;
-SelfNode->_next  = (ObjectWaiter *) 0xBAD ;
-SelfNode->TState = ObjectWaiter::TS_RUN ;
-}
-// Caveat: TryLock() is not necessarily serializing if it returns failure.
-// Callers must compensate as needed.
-int ObjectMonitor::TryLock (Thread * Self) {
-for (;;) {
-void * own = _owner ;
-if (own != NULL) return 0 ;
-if (Atomic::cmpxchg_ptr (Self, &_owner, NULL) == NULL) {
-// Either guarantee _recursions == 0 or set _recursions = 0.
-assert (_recursions == 0, "invariant") ;
-assert (_owner == Self, "invariant") ;
-// CONSIDER: set or assert that OwnerIsThread == 1
-return 1 ;
-}
-// The lock had been free momentarily, but we lost the race to the lock.
-// Interference -- the CAS failed.
-// We can either return -1 or retry.
-// Retry doesn't make as much sense because the lock was just acquired.
-if (true) return -1 ;
-}
-}
-// NotRunnable() -- informed spinning
-//
-// Don't bother spinning if the owner is not eligible to drop the lock.
-// Peek at the owner's schedctl.sc_state and Thread._thread_values and
-// spin only if the owner thread is _thread_in_Java or _thread_in_vm.
-// The thread must be runnable in order to drop the lock in timely fashion.
-// If the _owner is not runnable then spinning will not likely be
-// successful (profitable).
-//
-// Beware -- the thread referenced by _owner could have died
-// so a simply fetch from _owner->_thread_state might trap.
-// Instead, we use SafeFetchXX() to safely LD _owner->_thread_state.
-// Because of the lifecycle issues the schedctl and _thread_state values
-// observed by NotRunnable() might be garbage.  NotRunnable must
-// tolerate this and consider the observed _thread_state value
-// as advisory.
-//
-// Beware too, that _owner is sometimes a BasicLock address and sometimes
-// a thread pointer.  We differentiate the two cases with OwnerIsThread.
-// Alternately, we might tag the type (thread pointer vs basiclock pointer)
-// with the LSB of _owner.  Another option would be to probablistically probe
-// the putative _owner->TypeTag value.
-//
-// Checking _thread_state isn't perfect.  Even if the thread is
-// in_java it might be blocked on a page-fault or have been preempted
-// and sitting on a ready/dispatch queue.  _thread state in conjunction
-// with schedctl.sc_state gives us a good picture of what the
-// thread is doing, however.
-//
-// TODO: check schedctl.sc_state.
-// We'll need to use SafeFetch32() to read from the schedctl block.
-// See RFE #5004247 and http://sac.sfbay.sun.com/Archives/CaseLog/arc/PSARC/2005/351/
-//
-// The return value from NotRunnable() is *advisory* -- the
-// result is based on sampling and is not necessarily coherent.
-// The caller must tolerate false-negative and false-positive errors.
-// Spinning, in general, is probabilistic anyway.
-int ObjectMonitor::NotRunnable (Thread * Self, Thread * ox) {
-// Check either OwnerIsThread or ox->TypeTag == 2BAD.
-if (!OwnerIsThread) return 0 ;
-if (ox == NULL) return 0 ;
-// Avoid transitive spinning ...
-// Say T1 spins or blocks trying to acquire L.  T1._Stalled is set to L.
-// Immediately after T1 acquires L it's possible that T2, also
-// spinning on L, will see L.Owner=T1 and T1._Stalled=L.
-// This occurs transiently after T1 acquired L but before
-// T1 managed to clear T1.Stalled.  T2 does not need to abort
-// its spin in this circumstance.
-intptr_t BlockedOn = SafeFetchN ((intptr_t *) &ox->_Stalled, intptr_t(1)) ;
-if (BlockedOn == 1) return 1 ;
-if (BlockedOn != 0) {
-return BlockedOn != intptr_t(this) && _owner == ox ;
-}
-assert (sizeof(((JavaThread *)ox)->_thread_state == sizeof(int)), "invariant") ;
-int jst = SafeFetch32 ((int *) &((JavaThread *) ox)->_thread_state, -1) ; ;
-// consider also: jst != _thread_in_Java -- but that's overspecific.
-return jst == _thread_blocked || jst == _thread_in_native ;
-}
-// Adaptive spin-then-block - rational spinning
-//
-// Note that we spin "globally" on _owner with a classic SMP-polite TATAS
-// algorithm.  On high order SMP systems it would be better to start with
-// a brief global spin and then revert to spinning locally.  In the spirit of MCS/CLH,
-// a contending thread could enqueue itself on the cxq and then spin locally
-// on a thread-specific variable such as its ParkEvent._Event flag.
-// That's left as an exercise for the reader.  Note that global spinning is
-// not problematic on Niagara, as the L2$ serves the interconnect and has both
-// low latency and massive bandwidth.
-//
-// Broadly, we can fix the spin frequency -- that is, the % of contended lock
-// acquisition attempts where we opt to spin --  at 100% and vary the spin count
-// (duration) or we can fix the count at approximately the duration of
-// a context switch and vary the frequency.   Of course we could also
-// vary both satisfying K == Frequency * Duration, where K is adaptive by monitor.
-// See http://j2se.east/~dice/PERSIST/040824-AdaptiveSpinning.html.
-//
-// This implementation varies the duration "D", where D varies with
-// the success rate of recent spin attempts. (D is capped at approximately
-// length of a round-trip context switch).  The success rate for recent
-// spin attempts is a good predictor of the success rate of future spin
-// attempts.  The mechanism adapts automatically to varying critical
-// section length (lock modality), system load and degree of parallelism.
-// D is maintained per-monitor in _SpinDuration and is initialized
-// optimistically.  Spin frequency is fixed at 100%.
-//
-// Note that _SpinDuration is volatile, but we update it without locks
-// or atomics.  The code is designed so that _SpinDuration stays within
-// a reasonable range even in the presence of races.  The arithmetic
-// operations on _SpinDuration are closed over the domain of legal values,
-// so at worst a race will install and older but still legal value.
-// At the very worst this introduces some apparent non-determinism.
-// We might spin when we shouldn't or vice-versa, but since the spin
-// count are relatively short, even in the worst case, the effect is harmless.
-//
-// Care must be taken that a low "D" value does not become an
-// an absorbing state.  Transient spinning failures -- when spinning
-// is overall profitable -- should not cause the system to converge
-// on low "D" values.  We want spinning to be stable and predictable
-// and fairly responsive to change and at the same time we don't want
-// it to oscillate, become metastable, be "too" non-deterministic,
-// or converge on or enter undesirable stable absorbing states.
-//
-// We implement a feedback-based control system -- using past behavior
-// to predict future behavior.  We face two issues: (a) if the
-// input signal is random then the spin predictor won't provide optimal
-// results, and (b) if the signal frequency is too high then the control
-// system, which has some natural response lag, will "chase" the signal.
-// (b) can arise from multimodal lock hold times.  Transient preemption
-// can also result in apparent bimodal lock hold times.
-// Although sub-optimal, neither condition is particularly harmful, as
-// in the worst-case we'll spin when we shouldn't or vice-versa.
-// The maximum spin duration is rather short so the failure modes aren't bad.
-// To be conservative, I've tuned the gain in system to bias toward
-// _not spinning.  Relatedly, the system can sometimes enter a mode where it
-// "rings" or oscillates between spinning and not spinning.  This happens
-// when spinning is just on the cusp of profitability, however, so the
-// situation is not dire.  The state is benign -- there's no need to add
-// hysteresis control to damp the transition rate between spinning and
-// not spinning.
-//
-// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-//
-// Spin-then-block strategies ...
-//
-// Thoughts on ways to improve spinning :
-//
-// *  Periodically call {psr_}getloadavg() while spinning, and
-//    permit unbounded spinning if the load average is <
-//    the number of processors.  Beware, however, that getloadavg()
-//    is exceptionally fast on solaris (about 1/10 the cost of a full
-//    spin cycle, but quite expensive on linux.  Beware also, that
-//    multiple JVMs could "ring" or oscillate in a feedback loop.
-//    Sufficient damping would solve that problem.
-//
-// *  We currently use spin loops with iteration counters to approximate
-//    spinning for some interval.  Given the availability of high-precision
-//    time sources such as gethrtime(), %TICK, %STICK, RDTSC, etc., we should
-//    someday reimplement the spin loops to duration-based instead of iteration-based.
-//
-// *  Don't spin if there are more than N = (CPUs/2) threads
-//        currently spinning on the monitor (or globally).
-//    That is, limit the number of concurrent spinners.
-//    We might also limit the # of spinners in the JVM, globally.
-//
-// *  If a spinning thread observes _owner change hands it should
-//    abort the spin (and park immediately) or at least debit
-//    the spin counter by a large "penalty".
-//
-// *  Classically, the spin count is either K*(CPUs-1) or is a
-//        simple constant that approximates the length of a context switch.
-//    We currently use a value -- computed by a special utility -- that
-//    approximates round-trip context switch times.
-//
-// *  Normally schedctl_start()/_stop() is used to advise the kernel
-//    to avoid preempting threads that are running in short, bounded
-//    critical sections.  We could use the schedctl hooks in an inverted
-//    sense -- spinners would set the nopreempt flag, but poll the preempt
-//    pending flag.  If a spinner observed a pending preemption it'd immediately
-//    abort the spin and park.   As such, the schedctl service acts as
-//    a preemption warning mechanism.
-//
-// *  In lieu of spinning, if the system is running below saturation
-//    (that is, loadavg() << #cpus), we can instead suppress futile
-//    wakeup throttling, or even wake more than one successor at exit-time.
-//    The net effect is largely equivalent to spinning.  In both cases,
-//    contending threads go ONPROC and opportunistically attempt to acquire
-//    the lock, decreasing lock handover latency at the expense of wasted
-//    cycles and context switching.
-//
-// *  We might to spin less after we've parked as the thread will
-//    have less $ and TLB affinity with the processor.
-//    Likewise, we might spin less if we come ONPROC on a different
-//    processor or after a long period (>> rechose_interval).
-//
-// *  A table-driven state machine similar to Solaris' dispadmin scheduling
-//    tables might be a better design.  Instead of encoding information in
-//    _SpinDuration, _SpinFreq and _SpinClock we'd just use explicit,
-//    discrete states.   Success or failure during a spin would drive
-//    state transitions, and each state node would contain a spin count.
-//
-// *  If the processor is operating in a mode intended to conserve power
-//    (such as Intel's SpeedStep) or to reduce thermal output (thermal
-//    step-down mode) then the Java synchronization subsystem should
-//    forgo spinning.
-//
-// *  The minimum spin duration should be approximately the worst-case
-//    store propagation latency on the platform.  That is, the time
-//    it takes a store on CPU A to become visible on CPU B, where A and
-//    B are "distant".
-//
-// *  We might want to factor a thread's priority in the spin policy.
-//    Threads with a higher priority might spin for slightly longer.
-//    Similarly, if we use back-off in the TATAS loop, lower priority
-//    threads might back-off longer.  We don't currently use a
-//    thread's priority when placing it on the entry queue.  We may
-//    want to consider doing so in future releases.
-//
-// *  We might transiently drop a thread's scheduling priority while it spins.
-//    SCHED_BATCH on linux and FX scheduling class at priority=0 on Solaris
-//    would suffice.  We could even consider letting the thread spin indefinitely at
-//    a depressed or "idle" priority.  This brings up fairness issues, however --
-//    in a saturated system a thread would with a reduced priority could languish
-//    for extended periods on the ready queue.
-//
-// *  While spinning try to use the otherwise wasted time to help the VM make
-//    progress:
-//
-//    -- YieldTo() the owner, if the owner is OFFPROC but ready
-//       Done our remaining quantum directly to the ready thread.
-//       This helps "push" the lock owner through the critical section.
-//       It also tends to improve affinity/locality as the lock
-//       "migrates" less frequently between CPUs.
-//    -- Walk our own stack in anticipation of blocking.  Memoize the roots.
-//    -- Perform strand checking for other thread.  Unpark potential strandees.
-//    -- Help GC: trace or mark -- this would need to be a bounded unit of work.
-//       Unfortunately this will pollute our $ and TLBs.  Recall that we
-//       spin to avoid context switching -- context switching has an
-//       immediate cost in latency, a disruptive cost to other strands on a CMT
-//       processor, and an amortized cost because of the D$ and TLB cache
-//       reload transient when the thread comes back ONPROC and repopulates
-//       $s and TLBs.
-//    -- call getloadavg() to see if the system is saturated.  It'd probably
-//       make sense to call getloadavg() half way through the spin.
-//       If the system isn't at full capacity the we'd simply reset
-//       the spin counter to and extend the spin attempt.
-//    -- Doug points out that we should use the same "helping" policy
-//       in thread.yield().
-//
-// *  Try MONITOR-MWAIT on systems that support those instructions.
-//
-// *  The spin statistics that drive spin decisions & frequency are
-//    maintained in the objectmonitor structure so if we deflate and reinflate
-//    we lose spin state.  In practice this is not usually a concern
-//    as the default spin state after inflation is aggressive (optimistic)
-//    and tends toward spinning.  So in the worst case for a lock where
-//    spinning is not profitable we may spin unnecessarily for a brief
-//    period.  But then again, if a lock is contended it'll tend not to deflate
-//    in the first place.
-intptr_t ObjectMonitor::SpinCallbackArgument = 0 ;
-int (*ObjectMonitor::SpinCallbackFunction)(intptr_t, int) = NULL ;
-// Spinning: Fixed frequency (100%), vary duration
-int ObjectMonitor::TrySpin_VaryDuration (Thread * Self) {
-// Dumb, brutal spin.  Good for comparative measurements against adaptive spinning.
-int ctr = Knob_FixedSpin ;
-if (ctr != 0) {
-while (--ctr >= 0) {
-if (TryLock (Self) > 0) return 1 ;
-SpinPause () ;
-}
-return 0 ;
-}
-for (ctr = Knob_PreSpin + 1; --ctr >= 0 ; ) {
-if (TryLock(Self) > 0) {
-// Increase _SpinDuration ...
-// Note that we don't clamp SpinDuration precisely at SpinLimit.
-// Raising _SpurDuration to the poverty line is key.
-int x = _SpinDuration ;
-if (x < Knob_SpinLimit) {
-if (x < Knob_Poverty) x = Knob_Poverty ;
-_SpinDuration = x + Knob_BonusB ;
-}
-return 1 ;
-}
-SpinPause () ;
-}
-// Admission control - verify preconditions for spinning
-//
-// We always spin a little bit, just to prevent _SpinDuration == 0 from
-// becoming an absorbing state.  Put another way, we spin briefly to
-// sample, just in case the system load, parallelism, contention, or lock
-// modality changed.
-//
-// Consider the following alternative:
-// Periodically set _SpinDuration = _SpinLimit and try a long/full
-// spin attempt.  "Periodically" might mean after a tally of
-// the # of failed spin attempts (or iterations) reaches some threshold.
-// This takes us into the realm of 1-out-of-N spinning, where we
-// hold the duration constant but vary the frequency.
-ctr = _SpinDuration  ;
-if (ctr < Knob_SpinBase) ctr = Knob_SpinBase ;
-if (ctr <= 0) return 0 ;
-if (Knob_SuccRestrict && _succ != NULL) return 0 ;
-if (Knob_OState && NotRunnable (Self, (Thread *) _owner)) {
-TEVENT (Spin abort - notrunnable [TOP]);
-return 0 ;
-}
-int MaxSpin = Knob_MaxSpinners ;
-if (MaxSpin >= 0) {
-if (_Spinner > MaxSpin) {
-TEVENT (Spin abort -- too many spinners) ;
-return 0 ;
-}
-// Slighty racy, but benign ...
-Adjust (&_Spinner, 1) ;
-}
-// We're good to spin ... spin ingress.
-// CONSIDER: use Prefetch::write() to avoid RTS->RTO upgrades
-// when preparing to LD...CAS _owner, etc and the CAS is likely
-// to succeed.
-int hits    = 0 ;
-int msk     = 0 ;
-int caspty  = Knob_CASPenalty ;
-int oxpty   = Knob_OXPenalty ;
-int sss     = Knob_SpinSetSucc ;
-if (sss && _succ == NULL ) _succ = Self ;
-Thread * prv = NULL ;
-// There are three ways to exit the following loop:
-// 1.  A successful spin where this thread has acquired the lock.
-// 2.  Spin failure with prejudice
-// 3.  Spin failure without prejudice
-while (--ctr >= 0) {
-// Periodic polling -- Check for pending GC
-// Threads may spin while they're unsafe.
-// We don't want spinning threads to delay the JVM from reaching
-// a stop-the-world safepoint or to steal cycles from GC.
-// If we detect a pending safepoint we abort in order that
-// (a) this thread, if unsafe, doesn't delay the safepoint, and (b)
-// this thread, if safe, doesn't steal cycles from GC.
-// This is in keeping with the "no loitering in runtime" rule.
-// We periodically check to see if there's a safepoint pending.
-if ((ctr & 0xFF) == 0) {
-if (SafepointSynchronize::do_call_back()) {
-TEVENT (Spin: safepoint) ;
-goto Abort ;           // abrupt spin egress
-}
-if (Knob_UsePause & 1) SpinPause () ;
-int (*scb)(intptr_t,int) = SpinCallbackFunction ;
-if (hits > 50 && scb != NULL) {
-int abend = (*scb)(SpinCallbackArgument, 0) ;
-}
-}
-if (Knob_UsePause & 2) SpinPause() ;
-// Exponential back-off ...  Stay off the bus to reduce coherency traffic.
-// This is useful on classic SMP systems, but is of less utility on
-// N1-style CMT platforms.
-//
-// Trade-off: lock acquisition latency vs coherency bandwidth.
-// Lock hold times are typically short.  A histogram
-// of successful spin attempts shows that we usually acquire
-// the lock early in the spin.  That suggests we want to
-// sample _owner frequently in the early phase of the spin,
-// but then back-off and sample less frequently as the spin
-// progresses.  The back-off makes a good citizen on SMP big
-// SMP systems.  Oversampling _owner can consume excessive
-// coherency bandwidth.  Relatedly, if we _oversample _owner we
-// can inadvertently interfere with the the ST m->owner=null.
-// executed by the lock owner.
-if (ctr & msk) continue ;
-++hits ;
-if ((hits & 0xF) == 0) {
-// The 0xF, above, corresponds to the exponent.
-// Consider: (msk+1)|msk
-msk = ((msk << 2)|3) & BackOffMask ;
-}
-// Probe _owner with TATAS
-// If this thread observes the monitor transition or flicker
-// from locked to unlocked to locked, then the odds that this
-// thread will acquire the lock in this spin attempt go down
-// considerably.  The same argument applies if the CAS fails
-// or if we observe _owner change from one non-null value to
-// another non-null value.   In such cases we might abort
-// the spin without prejudice or apply a "penalty" to the
-// spin count-down variable "ctr", reducing it by 100, say.
-Thread * ox = (Thread *) _owner ;
-if (ox == NULL) {
-ox = (Thread *) Atomic::cmpxchg_ptr (Self, &_owner, NULL) ;
-if (ox == NULL) {
-// The CAS succeeded -- this thread acquired ownership
-// Take care of some bookkeeping to exit spin state.
-if (sss && _succ == Self) {
-_succ = NULL ;
-}
-if (MaxSpin > 0) Adjust (&_Spinner, -1) ;
-// Increase _SpinDuration :
-// The spin was successful (profitable) so we tend toward
-// longer spin attempts in the future.
-// CONSIDER: factor "ctr" into the _SpinDuration adjustment.
-// If we acquired the lock early in the spin cycle it
-// makes sense to increase _SpinDuration proportionally.
-// Note that we don't clamp SpinDuration precisely at SpinLimit.
-int x = _SpinDuration ;
-if (x < Knob_SpinLimit) {
-if (x < Knob_Poverty) x = Knob_Poverty ;
-_SpinDuration = x + Knob_Bonus ;
-}
-return 1 ;
-}
-// The CAS failed ... we can take any of the following actions:
-// * penalize: ctr -= Knob_CASPenalty
-// * exit spin with prejudice -- goto Abort;
-// * exit spin without prejudice.
-// * Since CAS is high-latency, retry again immediately.
-prv = ox ;
-TEVENT (Spin: cas failed) ;
-if (caspty == -2) break ;
-if (caspty == -1) goto Abort ;
-ctr -= caspty ;
-continue ;
-}
-// Did lock ownership change hands ?
-if (ox != prv && prv != NULL ) {
-TEVENT (spin: Owner changed)
-if (oxpty == -2) break ;
-if (oxpty == -1) goto Abort ;
-ctr -= oxpty ;
-}
-prv = ox ;
-// Abort the spin if the owner is not executing.
-// The owner must be executing in order to drop the lock.
-// Spinning while the owner is OFFPROC is idiocy.
-// Consider: ctr -= RunnablePenalty ;
-if (Knob_OState && NotRunnable (Self, ox)) {
-TEVENT (Spin abort - notrunnable);
-goto Abort ;
-}
-if (sss && _succ == NULL ) _succ = Self ;
-}
-// Spin failed with prejudice -- reduce _SpinDuration.
-// TODO: Use an AIMD-like policy to adjust _SpinDuration.
-// AIMD is globally stable.
-TEVENT (Spin failure) ;
-{
-int x = _SpinDuration ;
-if (x > 0) {
-// Consider an AIMD scheme like: x -= (x >> 3) + 100
-// This is globally sample and tends to damp the response.
-x -= Knob_Penalty ;
-if (x < 0) x = 0 ;
-_SpinDuration = x ;
-}
-}
-Abort:
-if (MaxSpin >= 0) Adjust (&_Spinner, -1) ;
-if (sss && _succ == Self) {
-_succ = NULL ;
-// Invariant: after setting succ=null a contending thread
-// must recheck-retry _owner before parking.  This usually happens
-// in the normal usage of TrySpin(), but it's safest
-// to make TrySpin() as foolproof as possible.
-OrderAccess::fence() ;
-if (TryLock(Self) > 0) return 1 ;
-}
-return 0 ;
-}
-#define TrySpin TrySpin_VaryDuration
-static void DeferredInitialize () {
-if (InitDone > 0) return ;
-if (Atomic::cmpxchg (-1, &InitDone, 0) != 0) {
-while (InitDone != 1) ;
-return ;
-}
-// One-shot global initialization ...
-// The initialization is idempotent, so we don't need locks.
-// In the future consider doing this via os::init_2().
-// SyncKnobs consist of <Key>=<Value> pairs in the style
-// of environment variables.  Start by converting ':' to NUL.
-if (SyncKnobs == NULL) SyncKnobs = "" ;
-size_t sz = strlen (SyncKnobs) ;
-char * knobs = (char *) malloc (sz + 2) ;
-if (knobs == NULL) {
-vm_exit_out_of_memory (sz + 2, "Parse SyncKnobs") ;
-guarantee (0, "invariant") ;
-}
-strcpy (knobs, SyncKnobs) ;
-knobs[sz+1] = 0 ;
-for (char * p = knobs ; *p ; p++) {
-if (*p == ':') *p = 0 ;
-}
-#define SETKNOB(x) { Knob_##x = kvGetInt (knobs, #x, Knob_##x); }
-SETKNOB(ReportSettings) ;
-SETKNOB(Verbose) ;
-SETKNOB(FixedSpin) ;
-SETKNOB(SpinLimit) ;
-SETKNOB(SpinBase) ;
-SETKNOB(SpinBackOff);
-SETKNOB(CASPenalty) ;
-SETKNOB(OXPenalty) ;
-SETKNOB(LogSpins) ;
-SETKNOB(SpinSetSucc) ;
-SETKNOB(SuccEnabled) ;
-SETKNOB(SuccRestrict) ;
-SETKNOB(Penalty) ;
-SETKNOB(Bonus) ;
-SETKNOB(BonusB) ;
-SETKNOB(Poverty) ;
-SETKNOB(SpinAfterFutile) ;
-SETKNOB(UsePause) ;
-SETKNOB(SpinEarly) ;
-SETKNOB(OState) ;
-SETKNOB(MaxSpinners) ;
-SETKNOB(PreSpin) ;
-SETKNOB(ExitPolicy) ;
-SETKNOB(QMode);
-SETKNOB(ResetEvent) ;
-SETKNOB(MoveNotifyee) ;
-SETKNOB(FastHSSEC) ;
-#undef SETKNOB
-if (os::is_MP()) {
-BackOffMask = (1 << Knob_SpinBackOff) - 1 ;
-if (Knob_ReportSettings) ::printf ("BackOffMask=%X\n", BackOffMask) ;
-// CONSIDER: BackOffMask = ROUNDUP_NEXT_POWER2 (ncpus-1)
-} else {
-Knob_SpinLimit = 0 ;
-Knob_SpinBase  = 0 ;
-Knob_PreSpin   = 0 ;
-Knob_FixedSpin = -1 ;
-}
-if (Knob_LogSpins == 0) {
-ObjectSynchronizer::_sync_FailedSpins = NULL ;
-}
-free (knobs) ;
-OrderAccess::fence() ;
-InitDone = 1 ;
-}
-// Theory of operations -- Monitors lists, thread residency, etc:
-//
-// * A thread acquires ownership of a monitor by successfully
-//   CAS()ing the _owner field from null to non-null.
-//
-// * Invariant: A thread appears on at most one monitor list --
-//   cxq, EntryList or WaitSet -- at any one time.
-//
-// * Contending threads "push" themselves onto the cxq with CAS
-//   and then spin/park.
-//
-// * After a contending thread eventually acquires the lock it must
-//   dequeue itself from either the EntryList or the cxq.
-//
-// * The exiting thread identifies and unparks an "heir presumptive"
-//   tentative successor thread on the EntryList.  Critically, the
-//   exiting thread doesn't unlink the successor thread from the EntryList.
-//   After having been unparked, the wakee will recontend for ownership of
-//   the monitor.   The successor (wakee) will either acquire the lock or
-//   re-park itself.
-//
-//   Succession is provided for by a policy of competitive handoff.
-//   The exiting thread does _not_ grant or pass ownership to the
-//   successor thread.  (This is also referred to as "handoff" succession").
-//   Instead the exiting thread releases ownership and possibly wakes
-//   a successor, so the successor can (re)compete for ownership of the lock.
-//   If the EntryList is empty but the cxq is populated the exiting
-//   thread will drain the cxq into the EntryList.  It does so by
-//   by detaching the cxq (installing null with CAS) and folding
-//   the threads from the cxq into the EntryList.  The EntryList is
-//   doubly linked, while the cxq is singly linked because of the
-//   CAS-based "push" used to enqueue recently arrived threads (RATs).
-//
-// * Concurrency invariants:
-//
-//   -- only the monitor owner may access or mutate the EntryList.
-//      The mutex property of the monitor itself protects the EntryList
-//      from concurrent interference.
-//   -- Only the monitor owner may detach the cxq.
-//
-// * The monitor entry list operations avoid locks, but strictly speaking
-//   they're not lock-free.  Enter is lock-free, exit is not.
-//   See http://j2se.east/~dice/PERSIST/040825-LockFreeQueues.html
-//
-// * The cxq can have multiple concurrent "pushers" but only one concurrent
-//   detaching thread.  This mechanism is immune from the ABA corruption.
-//   More precisely, the CAS-based "push" onto cxq is ABA-oblivious.
-//
-// * Taken together, the cxq and the EntryList constitute or form a
-//   single logical queue of threads stalled trying to acquire the lock.
-//   We use two distinct lists to improve the odds of a constant-time
-//   dequeue operation after acquisition (in the ::enter() epilog) and
-//   to reduce heat on the list ends.  (c.f. Michael Scott's "2Q" algorithm).
-//   A key desideratum is to minimize queue & monitor metadata manipulation
-//   that occurs while holding the monitor lock -- that is, we want to
-//   minimize monitor lock holds times.  Note that even a small amount of
-//   fixed spinning will greatly reduce the # of enqueue-dequeue operations
-//   on EntryList|cxq.  That is, spinning relieves contention on the "inner"
-//   locks and monitor metadata.
-//
-//   Cxq points to the the set of Recently Arrived Threads attempting entry.
-//   Because we push threads onto _cxq with CAS, the RATs must take the form of
-//   a singly-linked LIFO.  We drain _cxq into EntryList  at unlock-time when
-//   the unlocking thread notices that EntryList is null but _cxq is != null.
-//
-//   The EntryList is ordered by the prevailing queue discipline and
-//   can be organized in any convenient fashion, such as a doubly-linked list or
-//   a circular doubly-linked list.  Critically, we want insert and delete operations
-//   to operate in constant-time.  If we need a priority queue then something akin
-//   to Solaris' sleepq would work nicely.  Viz.,
-//   http://agg.eng/ws/on10_nightly/source/usr/src/uts/common/os/sleepq.c.
-//   Queue discipline is enforced at ::exit() time, when the unlocking thread
-//   drains the cxq into the EntryList, and orders or reorders the threads on the
-//   EntryList accordingly.
-//
-//   Barring "lock barging", this mechanism provides fair cyclic ordering,
-//   somewhat similar to an elevator-scan.
-//
-// * The monitor synchronization subsystem avoids the use of native
-//   synchronization primitives except for the narrow platform-specific
-//   park-unpark abstraction.  See the comments in os_solaris.cpp regarding
-//   the semantics of park-unpark.  Put another way, this monitor implementation
-//   depends only on atomic operations and park-unpark.  The monitor subsystem
-//   manages all RUNNING->BLOCKED and BLOCKED->READY transitions while the
-//   underlying OS manages the READY<->RUN transitions.
-//
-// * Waiting threads reside on the WaitSet list -- wait() puts
-//   the caller onto the WaitSet.
-//
-// * notify() or notifyAll() simply transfers threads from the WaitSet to
-//   either the EntryList or cxq.  Subsequent exit() operations will
-//   unpark the notifyee.  Unparking a notifee in notify() is inefficient -
-//   it's likely the notifyee would simply impale itself on the lock held
-//   by the notifier.
-//
-// * An interesting alternative is to encode cxq as (List,LockByte) where
-//   the LockByte is 0 iff the monitor is owned.  _owner is simply an auxiliary
-//   variable, like _recursions, in the scheme.  The threads or Events that form
-//   the list would have to be aligned in 256-byte addresses.  A thread would
-//   try to acquire the lock or enqueue itself with CAS, but exiting threads
-//   could use a 1-0 protocol and simply STB to set the LockByte to 0.
-//   Note that is is *not* word-tearing, but it does presume that full-word
-//   CAS operations are coherent with intermix with STB operations.  That's true
-//   on most common processors.
-//
-// * See also http://blogs.sun.com/dave
-void ATTR ObjectMonitor::EnterI (TRAPS) {
-Thread * Self = THREAD ;
-assert (Self->is_Java_thread(), "invariant") ;
-assert (((JavaThread *) Self)->thread_state() == _thread_blocked   , "invariant") ;
-// Try the lock - TATAS
-if (TryLock (Self) > 0) {
-assert (_succ != Self              , "invariant") ;
-assert (_owner == Self             , "invariant") ;
-assert (_Responsible != Self       , "invariant") ;
-return ;
-}
-DeferredInitialize () ;
-// We try one round of spinning *before* enqueueing Self.
-//
-// If the _owner is ready but OFFPROC we could use a YieldTo()
-// operation to donate the remainder of this thread's quantum
-// to the owner.  This has subtle but beneficial affinity
-// effects.
-if (TrySpin (Self) > 0) {
-assert (_owner == Self        , "invariant") ;
-assert (_succ != Self         , "invariant") ;
-assert (_Responsible != Self  , "invariant") ;
-return ;
-}
-// The Spin failed -- Enqueue and park the thread ...
-assert (_succ  != Self            , "invariant") ;
-assert (_owner != Self            , "invariant") ;
-assert (_Responsible != Self      , "invariant") ;
-// Enqueue "Self" on ObjectMonitor's _cxq.
-//
-// Node acts as a proxy for Self.
-// As an aside, if were to ever rewrite the synchronization code mostly
-// in Java, WaitNodes, ObjectMonitors, and Events would become 1st-class
-// Java objects.  This would avoid awkward lifecycle and liveness issues,
-// as well as eliminate a subset of ABA issues.
-// TODO: eliminate ObjectWaiter and enqueue either Threads or Events.
-//
-ObjectWaiter node(Self) ;
-Self->_ParkEvent->reset() ;
-node._prev   = (ObjectWaiter *) 0xBAD ;
-node.TState  = ObjectWaiter::TS_CXQ ;
-// Push "Self" onto the front of the _cxq.
-// Once on cxq/EntryList, Self stays on-queue until it acquires the lock.
-// Note that spinning tends to reduce the rate at which threads
-// enqueue and dequeue on EntryList|cxq.
-ObjectWaiter * nxt ;
-for (;;) {
-node._next = nxt = _cxq ;
-if (Atomic::cmpxchg_ptr (&node, &_cxq, nxt) == nxt) break ;
-// Interference - the CAS failed because _cxq changed.  Just retry.
-// As an optional optimization we retry the lock.
-if (TryLock (Self) > 0) {
-assert (_succ != Self         , "invariant") ;
-assert (_owner == Self        , "invariant") ;
-assert (_Responsible != Self  , "invariant") ;
-return ;
-}
-}
-// Check for cxq|EntryList edge transition to non-null.  This indicates
-// the onset of contention.  While contention persists exiting threads
-// will use a ST:MEMBAR:LD 1-1 exit protocol.  When contention abates exit
-// operations revert to the faster 1-0 mode.  This enter operation may interleave
-// (race) a concurrent 1-0 exit operation, resulting in stranding, so we
-// arrange for one of the contending thread to use a timed park() operations
-// to detect and recover from the race.  (Stranding is form of progress failure
-// where the monitor is unlocked but all the contending threads remain parked).
-// That is, at least one of the contended threads will periodically poll _owner.
-// One of the contending threads will become the designated "Responsible" thread.
-// The Responsible thread uses a timed park instead of a normal indefinite park
-// operation -- it periodically wakes and checks for and recovers from potential
-// strandings admitted by 1-0 exit operations.   We need at most one Responsible
-// thread per-monitor at any given moment.  Only threads on cxq|EntryList may
-// be responsible for a monitor.
-//
-// Currently, one of the contended threads takes on the added role of "Responsible".
-// A viable alternative would be to use a dedicated "stranding checker" thread
-// that periodically iterated over all the threads (or active monitors) and unparked
-// successors where there was risk of stranding.  This would help eliminate the
-// timer scalability issues we see on some platforms as we'd only have one thread
-// -- the checker -- parked on a timer.
-if ((SyncFlags & 16) == 0 && nxt == NULL && _EntryList == NULL) {
-// Try to assume the role of responsible thread for the monitor.
-// CONSIDER:  ST vs CAS vs { if (Responsible==null) Responsible=Self }
-Atomic::cmpxchg_ptr (Self, &_Responsible, NULL) ;
-}
-// The lock have been released while this thread was occupied queueing
-// itself onto _cxq.  To close the race and avoid "stranding" and
-// progress-liveness failure we must resample-retry _owner before parking.
-// Note the Dekker/Lamport duality: ST cxq; MEMBAR; LD Owner.
-// In this case the ST-MEMBAR is accomplished with CAS().
-//
-// TODO: Defer all thread state transitions until park-time.
-// Since state transitions are heavy and inefficient we'd like
-// to defer the state transitions until absolutely necessary,
-// and in doing so avoid some transitions ...
-TEVENT (Inflated enter - Contention) ;
-int nWakeups = 0 ;
-int RecheckInterval = 1 ;
-for (;;) {
-if (TryLock (Self) > 0) break ;
-assert (_owner != Self, "invariant") ;
-if ((SyncFlags & 2) && _Responsible == NULL) {
-Atomic::cmpxchg_ptr (Self, &_Responsible, NULL) ;
-}
-// park self
-if (_Responsible == Self || (SyncFlags & 1)) {
-TEVENT (Inflated enter - park TIMED) ;
-Self->_ParkEvent->park ((jlong) RecheckInterval) ;
-// Increase the RecheckInterval, but clamp the value.
-RecheckInterval *= 8 ;
-if (RecheckInterval > 1000) RecheckInterval = 1000 ;
-} else {
-TEVENT (Inflated enter - park UNTIMED) ;
-Self->_ParkEvent->park() ;
-}
-if (TryLock(Self) > 0) break ;
-// The lock is still contested.
-// Keep a tally of the # of futile wakeups.
-// Note that the counter is not protected by a lock or updated by atomics.
-// That is by design - we trade "lossy" counters which are exposed to
-// races during updates for a lower probe effect.
-TEVENT (Inflated enter - Futile wakeup) ;
-if (ObjectSynchronizer::_sync_FutileWakeups != NULL) {
-ObjectSynchronizer::_sync_FutileWakeups->inc() ;
-}
-++ nWakeups ;
-// Assuming this is not a spurious wakeup we'll normally find _succ == Self.
-// We can defer clearing _succ until after the spin completes
-// TrySpin() must tolerate being called with _succ == Self.
-// Try yet another round of adaptive spinning.
-if ((Knob_SpinAfterFutile & 1) && TrySpin (Self) > 0) break ;
-// We can find that we were unpark()ed and redesignated _succ while
-// we were spinning.  That's harmless.  If we iterate and call park(),
-// park() will consume the event and return immediately and we'll
-// just spin again.  This pattern can repeat, leaving _succ to simply
-// spin on a CPU.  Enable Knob_ResetEvent to clear pending unparks().
-// Alternately, we can sample fired() here, and if set, forgo spinning
-// in the next iteration.
-if ((Knob_ResetEvent & 1) && Self->_ParkEvent->fired()) {
-Self->_ParkEvent->reset() ;
-OrderAccess::fence() ;
-}
-if (_succ == Self) _succ = NULL ;
-// Invariant: after clearing _succ a thread *must* retry _owner before parking.
-OrderAccess::fence() ;
-}
-// Egress :
-// Self has acquired the lock -- Unlink Self from the cxq or EntryList.
-// Normally we'll find Self on the EntryList .
-// From the perspective of the lock owner (this thread), the
-// EntryList is stable and cxq is prepend-only.
-// The head of cxq is volatile but the interior is stable.
-// In addition, Self.TState is stable.
-assert (_owner == Self      , "invariant") ;
-assert (object() != NULL    , "invariant") ;
-// I'd like to write:
-//   guarantee (((oop)(object()))->mark() == markOopDesc::encode(this), "invariant") ;
-// but as we're at a safepoint that's not safe.
-UnlinkAfterAcquire (Self, &node) ;
-if (_succ == Self) _succ = NULL ;
-assert (_succ != Self, "invariant") ;
-if (_Responsible == Self) {
-_Responsible = NULL ;
-// Dekker pivot-point.
-// Consider OrderAccess::storeload() here
-// We may leave threads on cxq|EntryList without a designated
-// "Responsible" thread.  This is benign.  When this thread subsequently
-// exits the monitor it can "see" such preexisting "old" threads --
-// threads that arrived on the cxq|EntryList before the fence, above --
-// by LDing cxq|EntryList.  Newly arrived threads -- that is, threads
-// that arrive on cxq after the ST:MEMBAR, above -- will set Responsible
-// non-null and elect a new "Responsible" timer thread.
-//
-// This thread executes:
-//    ST Responsible=null; MEMBAR    (in enter epilog - here)
-//    LD cxq|EntryList               (in subsequent exit)
-//
-// Entering threads in the slow/contended path execute:
-//    ST cxq=nonnull; MEMBAR; LD Responsible (in enter prolog)
-//    The (ST cxq; MEMBAR) is accomplished with CAS().
-//
-// The MEMBAR, above, prevents the LD of cxq|EntryList in the subsequent
-// exit operation from floating above the ST Responsible=null.
-//
-// In *practice* however, EnterI() is always followed by some atomic
-// operation such as the decrement of _count in ::enter().  Those atomics
-// obviate the need for the explicit MEMBAR, above.
-}
-// We've acquired ownership with CAS().
-// CAS is serializing -- it has MEMBAR/FENCE-equivalent semantics.
-// But since the CAS() this thread may have also stored into _succ,
-// EntryList, cxq or Responsible.  These meta-data updates must be
-// visible __before this thread subsequently drops the lock.
-// Consider what could occur if we didn't enforce this constraint --
-// STs to monitor meta-data and user-data could reorder with (become
-// visible after) the ST in exit that drops ownership of the lock.
-// Some other thread could then acquire the lock, but observe inconsistent
-// or old monitor meta-data and heap data.  That violates the JMM.
-// To that end, the 1-0 exit() operation must have at least STST|LDST
-// "release" barrier semantics.  Specifically, there must be at least a
-// STST|LDST barrier in exit() before the ST of null into _owner that drops
-// the lock.   The barrier ensures that changes to monitor meta-data and data
-// protected by the lock will be visible before we release the lock, and
-// therefore before some other thread (CPU) has a chance to acquire the lock.
-// See also: http://gee.cs.oswego.edu/dl/jmm/cookbook.html.
-//
-// Critically, any prior STs to _succ or EntryList must be visible before
-// the ST of null into _owner in the *subsequent* (following) corresponding
-// monitorexit.  Recall too, that in 1-0 mode monitorexit does not necessarily
-// execute a serializing instruction.
-if (SyncFlags & 8) {
-OrderAccess::fence() ;
-}
-return ;
-}
-// ExitSuspendEquivalent:
-// A faster alternate to handle_special_suspend_equivalent_condition()
-//
-// handle_special_suspend_equivalent_condition() unconditionally
-// acquires the SR_lock.  On some platforms uncontended MutexLocker()
-// operations have high latency.  Note that in ::enter() we call HSSEC
-// while holding the monitor, so we effectively lengthen the critical sections.
-//
-// There are a number of possible solutions:
-//
-// A.  To ameliorate the problem we might also defer state transitions
-//     to as late as possible -- just prior to parking.
-//     Given that, we'd call HSSEC after having returned from park(),
-//     but before attempting to acquire the monitor.  This is only a
-//     partial solution.  It avoids calling HSSEC while holding the
-//     monitor (good), but it still increases successor reacquisition latency --
-//     the interval between unparking a successor and the time the successor
-//     resumes and retries the lock.  See ReenterI(), which defers state transitions.
-//     If we use this technique we can also avoid EnterI()-exit() loop
-//     in ::enter() where we iteratively drop the lock and then attempt
-//     to reacquire it after suspending.
-//
-// B.  In the future we might fold all the suspend bits into a
-//     composite per-thread suspend flag and then update it with CAS().
-//     Alternately, a Dekker-like mechanism with multiple variables
-//     would suffice:
-//       ST Self->_suspend_equivalent = false
-//       MEMBAR
-//       LD Self_>_suspend_flags
-//
-bool ObjectMonitor::ExitSuspendEquivalent (JavaThread * jSelf) {
-int Mode = Knob_FastHSSEC ;
-if (Mode && !jSelf->is_external_suspend()) {
-assert (jSelf->is_suspend_equivalent(), "invariant") ;
-jSelf->clear_suspend_equivalent() ;
-if (2 == Mode) OrderAccess::storeload() ;
-if (!jSelf->is_external_suspend()) return false ;
-// We raced a suspension -- fall thru into the slow path
-TEVENT (ExitSuspendEquivalent - raced) ;
-jSelf->set_suspend_equivalent() ;
-}
-return jSelf->handle_special_suspend_equivalent_condition() ;
-}
-// ReenterI() is a specialized inline form of the latter half of the
-// contended slow-path from EnterI().  We use ReenterI() only for
-// monitor reentry in wait().
-//
-// In the future we should reconcile EnterI() and ReenterI(), adding
-// Knob_Reset and Knob_SpinAfterFutile support and restructuring the
-// loop accordingly.
-void ATTR ObjectMonitor::ReenterI (Thread * Self, ObjectWaiter * SelfNode) {
-assert (Self != NULL                , "invariant") ;
-assert (SelfNode != NULL            , "invariant") ;
-assert (SelfNode->_thread == Self   , "invariant") ;
-assert (_waiters > 0                , "invariant") ;
-assert (((oop)(object()))->mark() == markOopDesc::encode(this) , "invariant") ;
-assert (((JavaThread *)Self)->thread_state() != _thread_blocked, "invariant") ;
-JavaThread * jt = (JavaThread *) Self ;
-int nWakeups = 0 ;
-for (;;) {
-ObjectWaiter::TStates v = SelfNode->TState ;
-guarantee (v == ObjectWaiter::TS_ENTER || v == ObjectWaiter::TS_CXQ, "invariant") ;
-assert    (_owner != Self, "invariant") ;
-if (TryLock (Self) > 0) break ;
-if (TrySpin (Self) > 0) break ;
-TEVENT (Wait Reentry - parking) ;
-// State transition wrappers around park() ...
-// ReenterI() wisely defers state transitions until
-// it's clear we must park the thread.
-{
-OSThreadContendState osts(Self->osthread());
-ThreadBlockInVM tbivm(jt);
-// cleared by handle_special_suspend_equivalent_condition()
-// or java_suspend_self()
-jt->set_suspend_equivalent();
-if (SyncFlags & 1) {
-Self->_ParkEvent->park ((jlong)1000) ;
-} else {
-Self->_ParkEvent->park () ;
-}
-// were we externally suspended while we were waiting?
-for (;;) {
-if (!ExitSuspendEquivalent (jt)) break ;
-if (_succ == Self) { _succ = NULL; OrderAccess::fence(); }
-jt->java_suspend_self();
-jt->set_suspend_equivalent();
-}
-}
-// Try again, but just so we distinguish between futile wakeups and
-// successful wakeups.  The following test isn't algorithmically
-// necessary, but it helps us maintain sensible statistics.
-if (TryLock(Self) > 0) break ;
-// The lock is still contested.
-// Keep a tally of the # of futile wakeups.
-// Note that the counter is not protected by a lock or updated by atomics.
-// That is by design - we trade "lossy" counters which are exposed to
-// races during updates for a lower probe effect.
-TEVENT (Wait Reentry - futile wakeup) ;
-++ nWakeups ;
-// Assuming this is not a spurious wakeup we'll normally
-// find that _succ == Self.
-if (_succ == Self) _succ = NULL ;
-// Invariant: after clearing _succ a contending thread
-// *must* retry  _owner before parking.
-OrderAccess::fence() ;
-if (ObjectSynchronizer::_sync_FutileWakeups != NULL) {
-ObjectSynchronizer::_sync_FutileWakeups->inc() ;
-}
-}
-// Self has acquired the lock -- Unlink Self from the cxq or EntryList .
-// Normally we'll find Self on the EntryList.
-// Unlinking from the EntryList is constant-time and atomic-free.
-// From the perspective of the lock owner (this thread), the
-// EntryList is stable and cxq is prepend-only.
-// The head of cxq is volatile but the interior is stable.
-// In addition, Self.TState is stable.
-assert (_owner == Self, "invariant") ;
-assert (((oop)(object()))->mark() == markOopDesc::encode(this), "invariant") ;
-UnlinkAfterAcquire (Self, SelfNode) ;
-if (_succ == Self) _succ = NULL ;
-assert (_succ != Self, "invariant") ;
-SelfNode->TState = ObjectWaiter::TS_RUN ;
-OrderAccess::fence() ;      // see comments at the end of EnterI()
-}
-bool ObjectMonitor::try_enter(Thread* THREAD) {
-if (THREAD != _owner) {
-if (THREAD->is_lock_owned ((address)_owner)) {
-assert(_recursions == 0, "internal state error");
-_owner = THREAD ;
-_recursions = 1 ;
-OwnerIsThread = 1 ;
-return true;
-}
-if (Atomic::cmpxchg_ptr (THREAD, &_owner, NULL) != NULL) {
-return false;
-}
-return true;
-} else {
-_recursions++;
-return true;
-}
-}
-void ATTR ObjectMonitor::enter(TRAPS) {
-// The following code is ordered to check the most common cases first
-// and to reduce RTS->RTO cache line upgrades on SPARC and IA32 processors.
-Thread * const Self = THREAD ;
-void * cur ;
-cur = Atomic::cmpxchg_ptr (Self, &_owner, NULL) ;
-if (cur == NULL) {
-// Either ASSERT _recursions == 0 or explicitly set _recursions = 0.
-assert (_recursions == 0   , "invariant") ;
-assert (_owner      == Self, "invariant") ;
-// CONSIDER: set or assert OwnerIsThread == 1
-return ;
-}
-if (cur == Self) {
-// TODO-FIXME: check for integer overflow!  BUGID 6557169.
-_recursions ++ ;
-return ;
-}
-if (Self->is_lock_owned ((address)cur)) {
-assert (_recursions == 0, "internal state error");
-_recursions = 1 ;
-// Commute owner from a thread-specific on-stack BasicLockObject address to
-// a full-fledged "Thread *".
-_owner = Self ;
-OwnerIsThread = 1 ;
-return ;
-}
-// We've encountered genuine contention.
-assert (Self->_Stalled == 0, "invariant") ;
-Self->_Stalled = intptr_t(this) ;
-// Try one round of spinning *before* enqueueing Self
-// and before going through the awkward and expensive state
-// transitions.  The following spin is strictly optional ...
-// Note that if we acquire the monitor from an initial spin
-// we forgo posting JVMTI events and firing DTRACE probes.
-if (Knob_SpinEarly && TrySpin (Self) > 0) {
-assert (_owner == Self      , "invariant") ;
-assert (_recursions == 0    , "invariant") ;
-assert (((oop)(object()))->mark() == markOopDesc::encode(this), "invariant") ;
-Self->_Stalled = 0 ;
-return ;
-}
-assert (_owner != Self          , "invariant") ;
-assert (_succ  != Self          , "invariant") ;
-assert (Self->is_Java_thread()  , "invariant") ;
-JavaThread * jt = (JavaThread *) Self ;
-assert (!SafepointSynchronize::is_at_safepoint(), "invariant") ;
-assert (jt->thread_state() != _thread_blocked   , "invariant") ;
-assert (this->object() != NULL  , "invariant") ;
-assert (_count >= 0, "invariant") ;
-// Prevent deflation at STW-time.  See deflate_idle_monitors() and is_busy().
-// Ensure the object-monitor relationship remains stable while there's contention.
-Atomic::inc_ptr(&_count);
-{ // Change java thread status to indicate blocked on monitor enter.
-JavaThreadBlockedOnMonitorEnterState jtbmes(jt, this);
-DTRACE_MONITOR_PROBE(contended__enter, this, object(), jt);
-if (JvmtiExport::should_post_monitor_contended_enter()) {
-JvmtiExport::post_monitor_contended_enter(jt, this);
-}
-OSThreadContendState osts(Self->osthread());
-ThreadBlockInVM tbivm(jt);
-Self->set_current_pending_monitor(this);
-// TODO-FIXME: change the following for(;;) loop to straight-line code.
-for (;;) {
-jt->set_suspend_equivalent();
-// cleared by handle_special_suspend_equivalent_condition()
-// or java_suspend_self()
-EnterI (THREAD) ;
-if (!ExitSuspendEquivalent(jt)) break ;
-//
-// We have acquired the contended monitor, but while we were
-// waiting another thread suspended us. We don't want to enter
-// the monitor while suspended because that would surprise the
-// thread that suspended us.
-//
-_recursions = 0 ;
-_succ = NULL ;
-exit (Self) ;
-jt->java_suspend_self();
-}
-Self->set_current_pending_monitor(NULL);
-}
-Atomic::dec_ptr(&_count);
-assert (_count >= 0, "invariant") ;
-Self->_Stalled = 0 ;
-// Must either set _recursions = 0 or ASSERT _recursions == 0.
-assert (_recursions == 0     , "invariant") ;
-assert (_owner == Self       , "invariant") ;
-assert (_succ  != Self       , "invariant") ;
-assert (((oop)(object()))->mark() == markOopDesc::encode(this), "invariant") ;
-// The thread -- now the owner -- is back in vm mode.
-// Report the glorious news via TI,DTrace and jvmstat.
-// The probe effect is non-trivial.  All the reportage occurs
-// while we hold the monitor, increasing the length of the critical
-// section.  Amdahl's parallel speedup law comes vividly into play.
-//
-// Another option might be to aggregate the events (thread local or
-// per-monitor aggregation) and defer reporting until a more opportune
-// time -- such as next time some thread encounters contention but has
-// yet to acquire the lock.  While spinning that thread could
-// spinning we could increment JVMStat counters, etc.
-DTRACE_MONITOR_PROBE(contended__entered, this, object(), jt);
-if (JvmtiExport::should_post_monitor_contended_entered()) {
-JvmtiExport::post_monitor_contended_entered(jt, this);
-}
-if (ObjectSynchronizer::_sync_ContendedLockAttempts != NULL) {
-ObjectSynchronizer::_sync_ContendedLockAttempts->inc() ;
-}
-}
-void ObjectMonitor::ExitEpilog (Thread * Self, ObjectWaiter * Wakee) {
-assert (_owner == Self, "invariant") ;
-// Exit protocol:
-// 1. ST _succ = wakee
-// 2. membar #loadstore|#storestore;
-// 2. ST _owner = NULL
-// 3. unpark(wakee)
-_succ = Knob_SuccEnabled ? Wakee->_thread : NULL ;
-ParkEvent * Trigger = Wakee->_event ;
-// Hygiene -- once we've set _owner = NULL we can't safely dereference Wakee again.
-// The thread associated with Wakee may have grabbed the lock and "Wakee" may be
-// out-of-scope (non-extant).
-Wakee  = NULL ;
-// Drop the lock
-OrderAccess::release_store_ptr (&_owner, NULL) ;
-OrderAccess::fence() ;                               // ST _owner vs LD in unpark()
-// TODO-FIXME:
-// If there's a safepoint pending the best policy would be to
-// get _this thread to a safepoint and only wake the successor
-// after the safepoint completed.  monitorexit uses a "leaf"
-// state transition, however, so this thread can't become
-// safe at this point in time.  (Its stack isn't walkable).
-// The next best thing is to defer waking the successor by
-// adding to a list of thread to be unparked after at the
-// end of the forthcoming STW).
-if (SafepointSynchronize::do_call_back()) {
-TEVENT (unpark before SAFEPOINT) ;
-}
-// Possible optimizations ...
-//
-// * Consider: set Wakee->UnparkTime = timeNow()
-//   When the thread wakes up it'll compute (timeNow() - Self->UnparkTime()).
-//   By measuring recent ONPROC latency we can approximate the
-//   system load.  In turn, we can feed that information back
-//   into the spinning & succession policies.
-//   (ONPROC latency correlates strongly with load).
-//
-// * Pull affinity:
-//   If the wakee is cold then transiently setting it's affinity
-//   to the current CPU is a good idea.
-//   See http://j2se.east/~dice/PERSIST/050624-PullAffinity.txt
-DTRACE_MONITOR_PROBE(contended__exit, this, object(), Self);
-Trigger->unpark() ;
-// Maintain stats and report events to JVMTI
-if (ObjectSynchronizer::_sync_Parks != NULL) {
-ObjectSynchronizer::_sync_Parks->inc() ;
-}
-}
-// exit()
-// ~~~~~~
-// Note that the collector can't reclaim the objectMonitor or deflate
-// the object out from underneath the thread calling ::exit() as the
-// thread calling ::exit() never transitions to a stable state.
-// This inhibits GC, which in turn inhibits asynchronous (and
-// inopportune) reclamation of "this".
-//
-// We'd like to assert that: (THREAD->thread_state() != _thread_blocked) ;
-// There's one exception to the claim above, however.  EnterI() can call
-// exit() to drop a lock if the acquirer has been externally suspended.
-// In that case exit() is called with _thread_state as _thread_blocked,
-// but the monitor's _count field is > 0, which inhibits reclamation.
-//
-// 1-0 exit
-// ~~~~~~~~
-// ::exit() uses a canonical 1-1 idiom with a MEMBAR although some of
-// the fast-path operators have been optimized so the common ::exit()
-// operation is 1-0.  See i486.ad fast_unlock(), for instance.
-// The code emitted by fast_unlock() elides the usual MEMBAR.  This
-// greatly improves latency -- MEMBAR and CAS having considerable local
-// latency on modern processors -- but at the cost of "stranding".  Absent the
-// MEMBAR, a thread in fast_unlock() can race a thread in the slow
-// ::enter() path, resulting in the entering thread being stranding
-// and a progress-liveness failure.   Stranding is extremely rare.
-// We use timers (timed park operations) & periodic polling to detect
-// and recover from stranding.  Potentially stranded threads periodically
-// wake up and poll the lock.  See the usage of the _Responsible variable.
-//
-// The CAS() in enter provides for safety and exclusion, while the CAS or
-// MEMBAR in exit provides for progress and avoids stranding.  1-0 locking
-// eliminates the CAS/MEMBAR from the exist path, but it admits stranding.
-// We detect and recover from stranding with timers.
-//
-// If a thread transiently strands it'll park until (a) another
-// thread acquires the lock and then drops the lock, at which time the
-// exiting thread will notice and unpark the stranded thread, or, (b)
-// the timer expires.  If the lock is high traffic then the stranding latency
-// will be low due to (a).  If the lock is low traffic then the odds of
-// stranding are lower, although the worst-case stranding latency
-// is longer.  Critically, we don't want to put excessive load in the
-// platform's timer subsystem.  We want to minimize both the timer injection
-// rate (timers created/sec) as well as the number of timers active at
-// any one time.  (more precisely, we want to minimize timer-seconds, which is
-// the integral of the # of active timers at any instant over time).
-// Both impinge on OS scalability.  Given that, at most one thread parked on
-// a monitor will use a timer.
-void ATTR ObjectMonitor::exit(TRAPS) {
-Thread * Self = THREAD ;
-if (THREAD != _owner) {
-if (THREAD->is_lock_owned((address) _owner)) {
-// Transmute _owner from a BasicLock pointer to a Thread address.
-// We don't need to hold _mutex for this transition.
-// Non-null to Non-null is safe as long as all readers can
-// tolerate either flavor.
-assert (_recursions == 0, "invariant") ;
-_owner = THREAD ;
-_recursions = 0 ;
-OwnerIsThread = 1 ;
-} else {
-// NOTE: we need to handle unbalanced monitor enter/exit
-// in native code by throwing an exception.
-// TODO: Throw an IllegalMonitorStateException ?
-TEVENT (Exit - Throw IMSX) ;
-assert(false, "Non-balanced monitor enter/exit!");
-if (false) {
-THROW(vmSymbols::java_lang_IllegalMonitorStateException());
-}
-return;
-}
-}
-if (_recursions != 0) {
-_recursions--;        // this is simple recursive enter
-TEVENT (Inflated exit - recursive) ;
-return ;
-}
-// Invariant: after setting Responsible=null an thread must execute
-// a MEMBAR or other serializing instruction before fetching EntryList|cxq.
-if ((SyncFlags & 4) == 0) {
-_Responsible = NULL ;
-}
-for (;;) {
-assert (THREAD == _owner, "invariant") ;
-// Fast-path monitor exit:
-//
-// Observe the Dekker/Lamport duality:
-// A thread in ::exit() executes:
-//   ST Owner=null; MEMBAR; LD EntryList|cxq.
-// A thread in the contended ::enter() path executes the complementary:
-//   ST EntryList|cxq = nonnull; MEMBAR; LD Owner.
-//
-// Note that there's a benign race in the exit path.  We can drop the
-// lock, another thread can reacquire the lock immediately, and we can
-// then wake a thread unnecessarily (yet another flavor of futile wakeup).
-// This is benign, and we've structured the code so the windows are short
-// and the frequency of such futile wakeups is low.
-//
-// We could eliminate the race by encoding both the "LOCKED" state and
-// the queue head in a single word.  Exit would then use either CAS to
-// clear the LOCKED bit/byte.  This precludes the desirable 1-0 optimization,
-// however.
-//
-// Possible fast-path ::exit() optimization:
-// The current fast-path exit implementation fetches both cxq and EntryList.
-// See also i486.ad fast_unlock().  Testing has shown that two LDs
-// isn't measurably slower than a single LD on any platforms.
-// Still, we could reduce the 2 LDs to one or zero by one of the following:
-//
-// - Use _count instead of cxq|EntryList
-//   We intend to eliminate _count, however, when we switch
-//   to on-the-fly deflation in ::exit() as is used in
-//   Metalocks and RelaxedLocks.
-//
-// - Establish the invariant that cxq == null implies EntryList == null.
-//   set cxq == EMPTY (1) to encode the state where cxq is empty
-//   by EntryList != null.  EMPTY is a distinguished value.
-//   The fast-path exit() would fetch cxq but not EntryList.
-//
-// - Encode succ as follows:
-//   succ = t :  Thread t is the successor -- t is ready or is spinning.
-//               Exiting thread does not need to wake a successor.
-//   succ = 0 :  No successor required -> (EntryList|cxq) == null
-//               Exiting thread does not need to wake a successor
-//   succ = 1 :  Successor required    -> (EntryList|cxq) != null and
-//               logically succ == null.
-//               Exiting thread must wake a successor.
-//
-//   The 1-1 fast-exit path would appear as :
-//     _owner = null ; membar ;
-//     if (_succ == 1 && CAS (&_owner, null, Self) == null) goto SlowPath
-//     goto FastPathDone ;
-//
-//   and the 1-0 fast-exit path would appear as:
-//      if (_succ == 1) goto SlowPath
-//      Owner = null ;
-//      goto FastPathDone
-//
-// - Encode the LSB of _owner as 1 to indicate that exit()
-//   must use the slow-path and make a successor ready.
-//   (_owner & 1) == 0 IFF succ != null || (EntryList|cxq) == null
-//   (_owner & 1) == 0 IFF succ == null && (EntryList|cxq) != null (obviously)
-//   The 1-0 fast exit path would read:
-//      if (_owner != Self) goto SlowPath
-//      _owner = null
-//      goto FastPathDone
-if (Knob_ExitPolicy == 0) {
-// release semantics: prior loads and stores from within the critical section
-// must not float (reorder) past the following store that drops the lock.
-// On SPARC that requires MEMBAR #loadstore|#storestore.
-// But of course in TSO #loadstore|#storestore is not required.
-// I'd like to write one of the following:
-// A.  OrderAccess::release() ; _owner = NULL
-// B.  OrderAccess::loadstore(); OrderAccess::storestore(); _owner = NULL;
-// Unfortunately OrderAccess::release() and OrderAccess::loadstore() both
-// store into a _dummy variable.  That store is not needed, but can result
-// in massive wasteful coherency traffic on classic SMP systems.
-// Instead, I use release_store(), which is implemented as just a simple
-// ST on x64, x86 and SPARC.
-OrderAccess::release_store_ptr (&_owner, NULL) ;   // drop the lock
-OrderAccess::storeload() ;                         // See if we need to wake a successor
-if ((intptr_t(_EntryList)|intptr_t(_cxq)) == 0 || _succ != NULL) {
-TEVENT (Inflated exit - simple egress) ;
-return ;
-}
-TEVENT (Inflated exit - complex egress) ;
-// Normally the exiting thread is responsible for ensuring succession,
-// but if other successors are ready or other entering threads are spinning
-// then this thread can simply store NULL into _owner and exit without
-// waking a successor.  The existence of spinners or ready successors
-// guarantees proper succession (liveness).  Responsibility passes to the
-// ready or running successors.  The exiting thread delegates the duty.
-// More precisely, if a successor already exists this thread is absolved
-// of the responsibility of waking (unparking) one.
-//
-// The _succ variable is critical to reducing futile wakeup frequency.
-// _succ identifies the "heir presumptive" thread that has been made
-// ready (unparked) but that has not yet run.  We need only one such
-// successor thread to guarantee progress.
-// See http://www.usenix.org/events/jvm01/full_papers/dice/dice.pdf
-// section 3.3 "Futile Wakeup Throttling" for details.
-//
-// Note that spinners in Enter() also set _succ non-null.
-// In the current implementation spinners opportunistically set
-// _succ so that exiting threads might avoid waking a successor.
-// Another less appealing alternative would be for the exiting thread
-// to drop the lock and then spin briefly to see if a spinner managed
-// to acquire the lock.  If so, the exiting thread could exit
-// immediately without waking a successor, otherwise the exiting
-// thread would need to dequeue and wake a successor.
-// (Note that we'd need to make the post-drop spin short, but no
-// shorter than the worst-case round-trip cache-line migration time.
-// The dropped lock needs to become visible to the spinner, and then
-// the acquisition of the lock by the spinner must become visible to
-// the exiting thread).
-//
-// It appears that an heir-presumptive (successor) must be made ready.
-// Only the current lock owner can manipulate the EntryList or
-// drain _cxq, so we need to reacquire the lock.  If we fail
-// to reacquire the lock the responsibility for ensuring succession
-// falls to the new owner.
-//
-if (Atomic::cmpxchg_ptr (THREAD, &_owner, NULL) != NULL) {
-return ;
-}
-TEVENT (Exit - Reacquired) ;
-} else {
-if ((intptr_t(_EntryList)|intptr_t(_cxq)) == 0 || _succ != NULL) {
-OrderAccess::release_store_ptr (&_owner, NULL) ;   // drop the lock
-OrderAccess::storeload() ;
-// Ratify the previously observed values.
-if (_cxq == NULL || _succ != NULL) {
-TEVENT (Inflated exit - simple egress) ;
-return ;
-}
-// inopportune interleaving -- the exiting thread (this thread)
-// in the fast-exit path raced an entering thread in the slow-enter
-// path.
-// We have two choices:
-// A.  Try to reacquire the lock.
-//     If the CAS() fails return immediately, otherwise
-//     we either restart/rerun the exit operation, or simply
-//     fall-through into the code below which wakes a successor.
-// B.  If the elements forming the EntryList|cxq are TSM
-//     we could simply unpark() the lead thread and return
-//     without having set _succ.
-if (Atomic::cmpxchg_ptr (THREAD, &_owner, NULL) != NULL) {
-TEVENT (Inflated exit - reacquired succeeded) ;
-return ;
-}
-TEVENT (Inflated exit - reacquired failed) ;
-} else {
-TEVENT (Inflated exit - complex egress) ;
-}
-}
-guarantee (_owner == THREAD, "invariant") ;
-// Select an appropriate successor ("heir presumptive") from the EntryList
-// and make it ready.  Generally we just wake the head of EntryList .
-// There's no algorithmic constraint that we use the head - it's just
-// a policy decision.   Note that the thread at head of the EntryList
-// remains at the head until it acquires the lock.  This means we'll
-// repeatedly wake the same thread until it manages to grab the lock.
-// This is generally a good policy - if we're seeing lots of futile wakeups
-// at least we're waking/rewaking a thread that's like to be hot or warm
-// (have residual D$ and TLB affinity).
-//
-// "Wakeup locality" optimization:
-// http://j2se.east/~dice/PERSIST/040825-WakeLocality.txt
-// In the future we'll try to bias the selection mechanism
-// to preferentially pick a thread that recently ran on
-// a processor element that shares cache with the CPU on which
-// the exiting thread is running.   We need access to Solaris'
-// schedctl.sc_cpu to make that work.
-//
-ObjectWaiter * w = NULL ;
-int QMode = Knob_QMode ;
-if (QMode == 2 && _cxq != NULL) {
-// QMode == 2 : cxq has precedence over EntryList.
-// Try to directly wake a successor from the cxq.
-// If successful, the successor will need to unlink itself from cxq.
-w = _cxq ;
-assert (w != NULL, "invariant") ;
-assert (w->TState == ObjectWaiter::TS_CXQ, "Invariant") ;
-ExitEpilog (Self, w) ;
-return ;
-}
-if (QMode == 3 && _cxq != NULL) {
-// Aggressively drain cxq into EntryList at the first opportunity.
-// This policy ensure that recently-run threads live at the head of EntryList.
-// Drain _cxq into EntryList - bulk transfer.
-// First, detach _cxq.
-// The following loop is tantamount to: w = swap (&cxq, NULL)
-w = _cxq ;
-for (;;) {
-assert (w != NULL, "Invariant") ;
-ObjectWaiter * u = (ObjectWaiter *) Atomic::cmpxchg_ptr (NULL, &_cxq, w) ;
-if (u == w) break ;
-w = u ;
-}
-assert (w != NULL              , "invariant") ;
-ObjectWaiter * q = NULL ;
-ObjectWaiter * p ;
-for (p = w ; p != NULL ; p = p->_next) {
-guarantee (p->TState == ObjectWaiter::TS_CXQ, "Invariant") ;
-p->TState = ObjectWaiter::TS_ENTER ;
-p->_prev = q ;
-q = p ;
-}
-// Append the RATs to the EntryList
-// TODO: organize EntryList as a CDLL so we can locate the tail in constant-time.
-ObjectWaiter * Tail ;
-for (Tail = _EntryList ; Tail != NULL && Tail->_next != NULL ; Tail = Tail->_next) ;
-if (Tail == NULL) {
-_EntryList = w ;
-} else {
-Tail->_next = w ;
-w->_prev = Tail ;
-}
-// Fall thru into code that tries to wake a successor from EntryList
-}
-if (QMode == 4 && _cxq != NULL) {
-// Aggressively drain cxq into EntryList at the first opportunity.
-// This policy ensure that recently-run threads live at the head of EntryList.
-// Drain _cxq into EntryList - bulk transfer.
-// First, detach _cxq.
-// The following loop is tantamount to: w = swap (&cxq, NULL)
-w = _cxq ;
-for (;;) {
-assert (w != NULL, "Invariant") ;
-ObjectWaiter * u = (ObjectWaiter *) Atomic::cmpxchg_ptr (NULL, &_cxq, w) ;
-if (u == w) break ;
-w = u ;
-}
-assert (w != NULL              , "invariant") ;
-ObjectWaiter * q = NULL ;
-ObjectWaiter * p ;
-for (p = w ; p != NULL ; p = p->_next) {
-guarantee (p->TState == ObjectWaiter::TS_CXQ, "Invariant") ;
-p->TState = ObjectWaiter::TS_ENTER ;
-p->_prev = q ;
-q = p ;
-}
-// Prepend the RATs to the EntryList
-if (_EntryList != NULL) {
-q->_next = _EntryList ;
-_EntryList->_prev = q ;
-}
-_EntryList = w ;
-// Fall thru into code that tries to wake a successor from EntryList
-}
-w = _EntryList  ;
-if (w != NULL) {
-// I'd like to write: guarantee (w->_thread != Self).
-// But in practice an exiting thread may find itself on the EntryList.
-// Lets say thread T1 calls O.wait().  Wait() enqueues T1 on O's waitset and
-// then calls exit().  Exit release the lock by setting O._owner to NULL.
-// Lets say T1 then stalls.  T2 acquires O and calls O.notify().  The
-// notify() operation moves T1 from O's waitset to O's EntryList. T2 then
-// release the lock "O".  T2 resumes immediately after the ST of null into
-// _owner, above.  T2 notices that the EntryList is populated, so it
-// reacquires the lock and then finds itself on the EntryList.
-// Given all that, we have to tolerate the circumstance where "w" is
-// associated with Self.
-assert (w->TState == ObjectWaiter::TS_ENTER, "invariant") ;
-ExitEpilog (Self, w) ;
-return ;
-}
-// If we find that both _cxq and EntryList are null then just
-// re-run the exit protocol from the top.
-w = _cxq ;
-if (w == NULL) continue ;
-// Drain _cxq into EntryList - bulk transfer.
-// First, detach _cxq.
-// The following loop is tantamount to: w = swap (&cxq, NULL)
-for (;;) {
-assert (w != NULL, "Invariant") ;
-ObjectWaiter * u = (ObjectWaiter *) Atomic::cmpxchg_ptr (NULL, &_cxq, w) ;
-if (u == w) break ;
-w = u ;
-}
-TEVENT (Inflated exit - drain cxq into EntryList) ;
-assert (w != NULL              , "invariant") ;
-assert (_EntryList  == NULL    , "invariant") ;
-// Convert the LIFO SLL anchored by _cxq into a DLL.
-// The list reorganization step operates in O(LENGTH(w)) time.
-// It's critical that this step operate quickly as
-// "Self" still holds the outer-lock, restricting parallelism
-// and effectively lengthening the critical section.
-// Invariant: s chases t chases u.
-// TODO-FIXME: consider changing EntryList from a DLL to a CDLL so
-// we have faster access to the tail.
-if (QMode == 1) {
-// QMode == 1 : drain cxq to EntryList, reversing order
-// We also reverse the order of the list.
-ObjectWaiter * s = NULL ;
-ObjectWaiter * t = w ;
-ObjectWaiter * u = NULL ;
-while (t != NULL) {
-guarantee (t->TState == ObjectWaiter::TS_CXQ, "invariant") ;
-t->TState = ObjectWaiter::TS_ENTER ;
-u = t->_next ;
-t->_prev = u ;
-t->_next = s ;
-s = t;
-t = u ;
-}
-_EntryList  = s ;
-assert (s != NULL, "invariant") ;
-} else {
-// QMode == 0 or QMode == 2
-_EntryList = w ;
-ObjectWaiter * q = NULL ;
-ObjectWaiter * p ;
-for (p = w ; p != NULL ; p = p->_next) {
-guarantee (p->TState == ObjectWaiter::TS_CXQ, "Invariant") ;
-p->TState = ObjectWaiter::TS_ENTER ;
-p->_prev = q ;
-q = p ;
-}
-}
-// In 1-0 mode we need: ST EntryList; MEMBAR #storestore; ST _owner = NULL
-// The MEMBAR is satisfied by the release_store() operation in ExitEpilog().
-// See if we can abdicate to a spinner instead of waking a thread.
-// A primary goal of the implementation is to reduce the
-// context-switch rate.
-if (_succ != NULL) continue;
-w = _EntryList  ;
-if (w != NULL) {
-guarantee (w->TState == ObjectWaiter::TS_ENTER, "invariant") ;
-ExitEpilog (Self, w) ;
-return ;
-}
-}
-}
-// complete_exit exits a lock returning recursion count
-// complete_exit/reenter operate as a wait without waiting
-// complete_exit requires an inflated monitor
-// The _owner field is not always the Thread addr even with an
-// inflated monitor, e.g. the monitor can be inflated by a non-owning
-// thread due to contention.
-intptr_t ObjectMonitor::complete_exit(TRAPS) {
-Thread * const Self = THREAD;
-assert(Self->is_Java_thread(), "Must be Java thread!");
-JavaThread *jt = (JavaThread *)THREAD;
-DeferredInitialize();
-if (THREAD != _owner) {
-if (THREAD->is_lock_owned ((address)_owner)) {
-assert(_recursions == 0, "internal state error");
-_owner = THREAD ;   /* Convert from basiclock addr to Thread addr */
-_recursions = 0 ;
-OwnerIsThread = 1 ;
-}
-}
-guarantee(Self == _owner, "complete_exit not owner");
-intptr_t save = _recursions; // record the old recursion count
-_recursions = 0;        // set the recursion level to be 0
-exit (Self) ;           // exit the monitor
-guarantee (_owner != Self, "invariant");
-return save;
-}
-// reenter() enters a lock and sets recursion count
-// complete_exit/reenter operate as a wait without waiting
-void ObjectMonitor::reenter(intptr_t recursions, TRAPS) {
-Thread * const Self = THREAD;
-assert(Self->is_Java_thread(), "Must be Java thread!");
-JavaThread *jt = (JavaThread *)THREAD;
-guarantee(_owner != Self, "reenter already owner");
-enter (THREAD);       // enter the monitor
-guarantee (_recursions == 0, "reenter recursion");
-_recursions = recursions;
-return;
-}
-// Note: a subset of changes to ObjectMonitor::wait()
-// will need to be replicated in complete_exit above
-void ObjectMonitor::wait(jlong millis, bool interruptible, TRAPS) {
-Thread * const Self = THREAD ;
-assert(Self->is_Java_thread(), "Must be Java thread!");
-JavaThread *jt = (JavaThread *)THREAD;
-DeferredInitialize () ;
-// Throw IMSX or IEX.
-CHECK_OWNER();
-// check for a pending interrupt
-if (interruptible && Thread::is_interrupted(Self, true) && !HAS_PENDING_EXCEPTION) {
-// post monitor waited event.  Note that this is past-tense, we are done waiting.
-if (JvmtiExport::should_post_monitor_waited()) {
-// Note: 'false' parameter is passed here because the
-// wait was not timed out due to thread interrupt.
-JvmtiExport::post_monitor_waited(jt, this, false);
-}
-TEVENT (Wait - Throw IEX) ;
-THROW(vmSymbols::java_lang_InterruptedException());
-return ;
-}
-TEVENT (Wait) ;
-assert (Self->_Stalled == 0, "invariant") ;
-Self->_Stalled = intptr_t(this) ;
-jt->set_current_waiting_monitor(this);
-// create a node to be put into the queue
-// Critically, after we reset() the event but prior to park(), we must check
-// for a pending interrupt.
-ObjectWaiter node(Self);
-node.TState = ObjectWaiter::TS_WAIT ;
-Self->_ParkEvent->reset() ;
-OrderAccess::fence();          // ST into Event; membar ; LD interrupted-flag
-// Enter the waiting queue, which is a circular doubly linked list in this case
-// but it could be a priority queue or any data structure.
-// _WaitSetLock protects the wait queue.  Normally the wait queue is accessed only
-// by the the owner of the monitor *except* in the case where park()
-// returns because of a timeout of interrupt.  Contention is exceptionally rare
-// so we use a simple spin-lock instead of a heavier-weight blocking lock.
-Thread::SpinAcquire (&_WaitSetLock, "WaitSet - add") ;
-AddWaiter (&node) ;
-Thread::SpinRelease (&_WaitSetLock) ;
-if ((SyncFlags & 4) == 0) {
-_Responsible = NULL ;
-}
-intptr_t save = _recursions; // record the old recursion count
-_waiters++;                  // increment the number of waiters
-_recursions = 0;             // set the recursion level to be 1
-exit (Self) ;                    // exit the monitor
-guarantee (_owner != Self, "invariant") ;
-// As soon as the ObjectMonitor's ownership is dropped in the exit()
-// call above, another thread can enter() the ObjectMonitor, do the
-// notify(), and exit() the ObjectMonitor. If the other thread's
-// exit() call chooses this thread as the successor and the unpark()
-// call happens to occur while this thread is posting a
-// MONITOR_CONTENDED_EXIT event, then we run the risk of the event
-// handler using RawMonitors and consuming the unpark().
-//
-// To avoid the problem, we re-post the event. This does no harm
-// even if the original unpark() was not consumed because we are the
-// chosen successor for this monitor.
-if (node._notified != 0 && _succ == Self) {
-node._event->unpark();
-}
-// The thread is on the WaitSet list - now park() it.
-// On MP systems it's conceivable that a brief spin before we park
-// could be profitable.
-//
-// TODO-FIXME: change the following logic to a loop of the form
-//   while (!timeout && !interrupted && _notified == 0) park()
-int ret = OS_OK ;
-int WasNotified = 0 ;
-{ // State transition wrappers
-OSThread* osthread = Self->osthread();
-OSThreadWaitState osts(osthread, true);
-{
-ThreadBlockInVM tbivm(jt);
-// Thread is in thread_blocked state and oop access is unsafe.
-jt->set_suspend_equivalent();
-if (interruptible && (Thread::is_interrupted(THREAD, false) || HAS_PENDING_EXCEPTION)) {
-// Intentionally empty
-} else
-if (node._notified == 0) {
-if (millis <= 0) {
-Self->_ParkEvent->park () ;
-} else {
-ret = Self->_ParkEvent->park (millis) ;
-}
-}
-// were we externally suspended while we were waiting?
-if (ExitSuspendEquivalent (jt)) {
-// TODO-FIXME: add -- if succ == Self then succ = null.
-jt->java_suspend_self();
-}
-} // Exit thread safepoint: transition _thread_blocked -> _thread_in_vm
-// Node may be on the WaitSet, the EntryList (or cxq), or in transition
-// from the WaitSet to the EntryList.
-// See if we need to remove Node from the WaitSet.
-// We use double-checked locking to avoid grabbing _WaitSetLock
-// if the thread is not on the wait queue.
-//
-// Note that we don't need a fence before the fetch of TState.
-// In the worst case we'll fetch a old-stale value of TS_WAIT previously
-// written by the is thread. (perhaps the fetch might even be satisfied
-// by a look-aside into the processor's own store buffer, although given
-// the length of the code path between the prior ST and this load that's
-// highly unlikely).  If the following LD fetches a stale TS_WAIT value
-// then we'll acquire the lock and then re-fetch a fresh TState value.
-// That is, we fail toward safety.
-if (node.TState == ObjectWaiter::TS_WAIT) {
-Thread::SpinAcquire (&_WaitSetLock, "WaitSet - unlink") ;
-if (node.TState == ObjectWaiter::TS_WAIT) {
-DequeueSpecificWaiter (&node) ;       // unlink from WaitSet
-assert(node._notified == 0, "invariant");
-node.TState = ObjectWaiter::TS_RUN ;
-}
-Thread::SpinRelease (&_WaitSetLock) ;
-}
-// The thread is now either on off-list (TS_RUN),
-// on the EntryList (TS_ENTER), or on the cxq (TS_CXQ).
-// The Node's TState variable is stable from the perspective of this thread.
-// No other threads will asynchronously modify TState.
-guarantee (node.TState != ObjectWaiter::TS_WAIT, "invariant") ;
-OrderAccess::loadload() ;
-if (_succ == Self) _succ = NULL ;
-WasNotified = node._notified ;
-// Reentry phase -- reacquire the monitor.
-// re-enter contended monitor after object.wait().
-// retain OBJECT_WAIT state until re-enter successfully completes
-// Thread state is thread_in_vm and oop access is again safe,
-// although the raw address of the object may have changed.
-// (Don't cache naked oops over safepoints, of course).
-// post monitor waited event. Note that this is past-tense, we are done waiting.
-if (JvmtiExport::should_post_monitor_waited()) {
-JvmtiExport::post_monitor_waited(jt, this, ret == OS_TIMEOUT);
-}
-OrderAccess::fence() ;
-assert (Self->_Stalled != 0, "invariant") ;
-Self->_Stalled = 0 ;
-assert (_owner != Self, "invariant") ;
-ObjectWaiter::TStates v = node.TState ;
-if (v == ObjectWaiter::TS_RUN) {
-enter (Self) ;
-} else {
-guarantee (v == ObjectWaiter::TS_ENTER || v == ObjectWaiter::TS_CXQ, "invariant") ;
-ReenterI (Self, &node) ;
-node.wait_reenter_end(this);
-}
-// Self has reacquired the lock.
-// Lifecycle - the node representing Self must not appear on any queues.
-// Node is about to go out-of-scope, but even if it were immortal we wouldn't
-// want residual elements associated with this thread left on any lists.
-guarantee (node.TState == ObjectWaiter::TS_RUN, "invariant") ;
-assert    (_owner == Self, "invariant") ;
-assert    (_succ != Self , "invariant") ;
-} // OSThreadWaitState()
-jt->set_current_waiting_monitor(NULL);
-guarantee (_recursions == 0, "invariant") ;
-_recursions = save;     // restore the old recursion count
-_waiters--;             // decrement the number of waiters
-// Verify a few postconditions
-assert (_owner == Self       , "invariant") ;
-assert (_succ  != Self       , "invariant") ;
-assert (((oop)(object()))->mark() == markOopDesc::encode(this), "invariant") ;
-if (SyncFlags & 32) {
-OrderAccess::fence() ;
-}
-// check if the notification happened
-if (!WasNotified) {
-// no, it could be timeout or Thread.interrupt() or both
-// check for interrupt event, otherwise it is timeout
-if (interruptible && Thread::is_interrupted(Self, true) && !HAS_PENDING_EXCEPTION) {
-TEVENT (Wait - throw IEX from epilog) ;
-THROW(vmSymbols::java_lang_InterruptedException());
-}
-}
-// NOTE: Spurious wake up will be consider as timeout.
-// Monitor notify has precedence over thread interrupt.
-}
-// Consider:
-// If the lock is cool (cxq == null && succ == null) and we're on an MP system
-// then instead of transferring a thread from the WaitSet to the EntryList
-// we might just dequeue a thread from the WaitSet and directly unpark() it.
-void ObjectMonitor::notify(TRAPS) {
-CHECK_OWNER();
-if (_WaitSet == NULL) {
-TEVENT (Empty-Notify) ;
-return ;
-}
-DTRACE_MONITOR_PROBE(notify, this, object(), THREAD);
-int Policy = Knob_MoveNotifyee ;
-Thread::SpinAcquire (&_WaitSetLock, "WaitSet - notify") ;
-ObjectWaiter * iterator = DequeueWaiter() ;
-if (iterator != NULL) {
-TEVENT (Notify1 - Transfer) ;
-guarantee (iterator->TState == ObjectWaiter::TS_WAIT, "invariant") ;
-guarantee (iterator->_notified == 0, "invariant") ;
-// Disposition - what might we do with iterator ?
-// a.  add it directly to the EntryList - either tail or head.
-// b.  push it onto the front of the _cxq.
-// For now we use (a).
-if (Policy != 4) {
-iterator->TState = ObjectWaiter::TS_ENTER ;
-}
-iterator->_notified = 1 ;
-ObjectWaiter * List = _EntryList ;
-if (List != NULL) {
-assert (List->_prev == NULL, "invariant") ;
-assert (List->TState == ObjectWaiter::TS_ENTER, "invariant") ;
-assert (List != iterator, "invariant") ;
-}
-if (Policy == 0) {       // prepend to EntryList
-if (List == NULL) {
-iterator->_next = iterator->_prev = NULL ;
-_EntryList = iterator ;
-} else {
-List->_prev = iterator ;
-iterator->_next = List ;
-iterator->_prev = NULL ;
-_EntryList = iterator ;
-}
-} else
-if (Policy == 1) {      // append to EntryList
-if (List == NULL) {
-iterator->_next = iterator->_prev = NULL ;
-_EntryList = iterator ;
-} else {
-// CONSIDER:  finding the tail currently requires a linear-time walk of
-// the EntryList.  We can make tail access constant-time by converting to
-// a CDLL instead of using our current DLL.
-ObjectWaiter * Tail ;
-for (Tail = List ; Tail->_next != NULL ; Tail = Tail->_next) ;
-assert (Tail != NULL && Tail->_next == NULL, "invariant") ;
-Tail->_next = iterator ;
-iterator->_prev = Tail ;
-iterator->_next = NULL ;
-}
-} else
-if (Policy == 2) {      // prepend to cxq
-// prepend to cxq
-if (List == NULL) {
-iterator->_next = iterator->_prev = NULL ;
-_EntryList = iterator ;
-} else {
-iterator->TState = ObjectWaiter::TS_CXQ ;
-for (;;) {
-ObjectWaiter * Front = _cxq ;
-iterator->_next = Front ;
-if (Atomic::cmpxchg_ptr (iterator, &_cxq, Front) == Front) {
-break ;
-}
-}
-}
-} else
-if (Policy == 3) {      // append to cxq
-iterator->TState = ObjectWaiter::TS_CXQ ;
-for (;;) {
-ObjectWaiter * Tail ;
-Tail = _cxq ;
-if (Tail == NULL) {
-iterator->_next = NULL ;
-if (Atomic::cmpxchg_ptr (iterator, &_cxq, NULL) == NULL) {
-break ;
-}
-} else {
-while (Tail->_next != NULL) Tail = Tail->_next ;
-Tail->_next = iterator ;
-iterator->_prev = Tail ;
-iterator->_next = NULL ;
-break ;
-}
-}
-} else {
-ParkEvent * ev = iterator->_event ;
-iterator->TState = ObjectWaiter::TS_RUN ;
-OrderAccess::fence() ;
-ev->unpark() ;
-}
-if (Policy < 4) {
-iterator->wait_reenter_begin(this);
-}
-// _WaitSetLock protects the wait queue, not the EntryList.  We could
-// move the add-to-EntryList operation, above, outside the critical section
-// protected by _WaitSetLock.  In practice that's not useful.  With the
-// exception of  wait() timeouts and interrupts the monitor owner
-// is the only thread that grabs _WaitSetLock.  There's almost no contention
-// on _WaitSetLock so it's not profitable to reduce the length of the
-// critical section.
-}
-Thread::SpinRelease (&_WaitSetLock) ;
-if (iterator != NULL && ObjectSynchronizer::_sync_Notifications != NULL) {
-ObjectSynchronizer::_sync_Notifications->inc() ;
-}
-}
-void ObjectMonitor::notifyAll(TRAPS) {
-CHECK_OWNER();
-ObjectWaiter* iterator;
-if (_WaitSet == NULL) {
-TEVENT (Empty-NotifyAll) ;
-return ;
-}
-DTRACE_MONITOR_PROBE(notifyAll, this, object(), THREAD);
-int Policy = Knob_MoveNotifyee ;
-int Tally = 0 ;
-Thread::SpinAcquire (&_WaitSetLock, "WaitSet - notifyall") ;
-for (;;) {
-iterator = DequeueWaiter () ;
-if (iterator == NULL) break ;
-TEVENT (NotifyAll - Transfer1) ;
-++Tally ;
-// Disposition - what might we do with iterator ?
-// a.  add it directly to the EntryList - either tail or head.
-// b.  push it onto the front of the _cxq.
-// For now we use (a).
-//
-// TODO-FIXME: currently notifyAll() transfers the waiters one-at-a-time from the waitset
-// to the EntryList.  This could be done more efficiently with a single bulk transfer,
-// but in practice it's not time-critical.  Beware too, that in prepend-mode we invert the
-// order of the waiters.  Lets say that the waitset is "ABCD" and the EntryList is "XYZ".
-// After a notifyAll() in prepend mode the waitset will be empty and the EntryList will
-// be "DCBAXYZ".
-guarantee (iterator->TState == ObjectWaiter::TS_WAIT, "invariant") ;
-guarantee (iterator->_notified == 0, "invariant") ;
-iterator->_notified = 1 ;
-if (Policy != 4) {
-iterator->TState = ObjectWaiter::TS_ENTER ;
-}
-ObjectWaiter * List = _EntryList ;
-if (List != NULL) {
-assert (List->_prev == NULL, "invariant") ;
-assert (List->TState == ObjectWaiter::TS_ENTER, "invariant") ;
-assert (List != iterator, "invariant") ;
-}
-if (Policy == 0) {       // prepend to EntryList
-if (List == NULL) {
-iterator->_next = iterator->_prev = NULL ;
-_EntryList = iterator ;
-} else {
-List->_prev = iterator ;
-iterator->_next = List ;
-iterator->_prev = NULL ;
-_EntryList = iterator ;
-}
-} else
-if (Policy == 1) {      // append to EntryList
-if (List == NULL) {
-iterator->_next = iterator->_prev = NULL ;
-_EntryList = iterator ;
-} else {
-// CONSIDER:  finding the tail currently requires a linear-time walk of
-// the EntryList.  We can make tail access constant-time by converting to
-// a CDLL instead of using our current DLL.
-ObjectWaiter * Tail ;
-for (Tail = List ; Tail->_next != NULL ; Tail = Tail->_next) ;
-assert (Tail != NULL && Tail->_next == NULL, "invariant") ;
-Tail->_next = iterator ;
-iterator->_prev = Tail ;
-iterator->_next = NULL ;
-}
-} else
-if (Policy == 2) {      // prepend to cxq
-// prepend to cxq
-iterator->TState = ObjectWaiter::TS_CXQ ;
-for (;;) {
-ObjectWaiter * Front = _cxq ;
-iterator->_next = Front ;
-if (Atomic::cmpxchg_ptr (iterator, &_cxq, Front) == Front) {
-break ;
-}
-}
-} else
-if (Policy == 3) {      // append to cxq
-iterator->TState = ObjectWaiter::TS_CXQ ;
-for (;;) {
-ObjectWaiter * Tail ;
-Tail = _cxq ;
-if (Tail == NULL) {
-iterator->_next = NULL ;
-if (Atomic::cmpxchg_ptr (iterator, &_cxq, NULL) == NULL) {
-break ;
-}
-} else {
-while (Tail->_next != NULL) Tail = Tail->_next ;
-Tail->_next = iterator ;
-iterator->_prev = Tail ;
-iterator->_next = NULL ;
-break ;
-}
-}
-} else {
-ParkEvent * ev = iterator->_event ;
-iterator->TState = ObjectWaiter::TS_RUN ;
-OrderAccess::fence() ;
-ev->unpark() ;
-}
-if (Policy < 4) {
-iterator->wait_reenter_begin(this);
-}
-// _WaitSetLock protects the wait queue, not the EntryList.  We could
-// move the add-to-EntryList operation, above, outside the critical section
-// protected by _WaitSetLock.  In practice that's not useful.  With the
-// exception of  wait() timeouts and interrupts the monitor owner
-// is the only thread that grabs _WaitSetLock.  There's almost no contention
-// on _WaitSetLock so it's not profitable to reduce the length of the
-// critical section.
-}
-Thread::SpinRelease (&_WaitSetLock) ;
-if (Tally != 0 && ObjectSynchronizer::_sync_Notifications != NULL) {
-ObjectSynchronizer::_sync_Notifications->inc(Tally) ;
-}
-}
-// check_slow() is a misnomer.  It's called to simply to throw an IMSX exception.
-// TODO-FIXME: remove check_slow() -- it's likely dead.
-void ObjectMonitor::check_slow(TRAPS) {
-TEVENT (check_slow - throw IMSX) ;
-assert(THREAD != _owner && !THREAD->is_lock_owned((address) _owner), "must not be owner");
-THROW_MSG(vmSymbols::java_lang_IllegalMonitorStateException(), "current thread not owner");
-}
-// -------------------------------------------------------------------------
-// The raw monitor subsystem is entirely distinct from normal
-// java-synchronization or jni-synchronization.  raw monitors are not
-// associated with objects.  They can be implemented in any manner
-// that makes sense.  The original implementors decided to piggy-back
-// the raw-monitor implementation on the existing Java objectMonitor mechanism.
-// This flaw needs to fixed.  We should reimplement raw monitors as sui-generis.
-// Specifically, we should not implement raw monitors via java monitors.
-// Time permitting, we should disentangle and deconvolve the two implementations
-// and move the resulting raw monitor implementation over to the JVMTI directories.
-// Ideally, the raw monitor implementation would be built on top of
-// park-unpark and nothing else.
-//
-// raw monitors are used mainly by JVMTI
-// The raw monitor implementation borrows the ObjectMonitor structure,
-// but the operators are degenerate and extremely simple.
-//
-// Mixed use of a single objectMonitor instance -- as both a raw monitor
-// and a normal java monitor -- is not permissible.
-//
-// Note that we use the single RawMonitor_lock to protect queue operations for
-// _all_ raw monitors.  This is a scalability impediment, but since raw monitor usage
-// is deprecated and rare, this is not of concern.  The RawMonitor_lock can not
-// be held indefinitely.  The critical sections must be short and bounded.
-//
-// -------------------------------------------------------------------------
-int ObjectMonitor::SimpleEnter (Thread * Self) {
-for (;;) {
-if (Atomic::cmpxchg_ptr (Self, &_owner, NULL) == NULL) {
-return OS_OK ;
-}
-ObjectWaiter Node (Self) ;
-Self->_ParkEvent->reset() ;     // strictly optional
-Node.TState = ObjectWaiter::TS_ENTER ;
-RawMonitor_lock->lock_without_safepoint_check() ;
-Node._next  = _EntryList ;
-_EntryList  = &Node ;
-OrderAccess::fence() ;
-if (_owner == NULL && Atomic::cmpxchg_ptr (Self, &_owner, NULL) == NULL) {
-_EntryList = Node._next ;
-RawMonitor_lock->unlock() ;
-return OS_OK ;
-}
-RawMonitor_lock->unlock() ;
-while (Node.TState == ObjectWaiter::TS_ENTER) {
-Self->_ParkEvent->park() ;
-}
-}
-}
-int ObjectMonitor::SimpleExit (Thread * Self) {
-guarantee (_owner == Self, "invariant") ;
-OrderAccess::release_store_ptr (&_owner, NULL) ;
-OrderAccess::fence() ;
-if (_EntryList == NULL) return OS_OK ;
-ObjectWaiter * w ;
-RawMonitor_lock->lock_without_safepoint_check() ;
-w = _EntryList ;
-if (w != NULL) {
-_EntryList = w->_next ;
-}
-RawMonitor_lock->unlock() ;
-if (w != NULL) {
-guarantee (w ->TState == ObjectWaiter::TS_ENTER, "invariant") ;
-ParkEvent * ev = w->_event ;
-w->TState = ObjectWaiter::TS_RUN ;
-OrderAccess::fence() ;
-ev->unpark() ;
-}
-return OS_OK ;
-}
-int ObjectMonitor::SimpleWait (Thread * Self, jlong millis) {
-guarantee (_owner == Self  , "invariant") ;
-guarantee (_recursions == 0, "invariant") ;
-ObjectWaiter Node (Self) ;
-Node._notified = 0 ;
-Node.TState    = ObjectWaiter::TS_WAIT ;
-RawMonitor_lock->lock_without_safepoint_check() ;
-Node._next     = _WaitSet ;
-_WaitSet       = &Node ;
-RawMonitor_lock->unlock() ;
-SimpleExit (Self) ;
-guarantee (_owner != Self, "invariant") ;
-int ret = OS_OK ;
-if (millis <= 0) {
-Self->_ParkEvent->park();
-} else {
-ret = Self->_ParkEvent->park(millis);
-}
-// If thread still resides on the waitset then unlink it.
-// Double-checked locking -- the usage is safe in this context
-// as we TState is volatile and the lock-unlock operators are
-// serializing (barrier-equivalent).
-if (Node.TState == ObjectWaiter::TS_WAIT) {
-RawMonitor_lock->lock_without_safepoint_check() ;
-if (Node.TState == ObjectWaiter::TS_WAIT) {
-// Simple O(n) unlink, but performance isn't critical here.
-ObjectWaiter * p ;
-ObjectWaiter * q = NULL ;
-for (p = _WaitSet ; p != &Node; p = p->_next) {
-q = p ;
-}
-guarantee (p == &Node, "invariant") ;
-if (q == NULL) {
-guarantee (p == _WaitSet, "invariant") ;
-_WaitSet = p->_next ;
-} else {
-guarantee (p == q->_next, "invariant") ;
-q->_next = p->_next ;
-}
-Node.TState = ObjectWaiter::TS_RUN ;
-}
-RawMonitor_lock->unlock() ;
-}
-guarantee (Node.TState == ObjectWaiter::TS_RUN, "invariant") ;
-SimpleEnter (Self) ;
-guarantee (_owner == Self, "invariant") ;
-guarantee (_recursions == 0, "invariant") ;
-return ret ;
-}
-int ObjectMonitor::SimpleNotify (Thread * Self, bool All) {
-guarantee (_owner == Self, "invariant") ;
-if (_WaitSet == NULL) return OS_OK ;
-// We have two options:
-// A. Transfer the threads from the WaitSet to the EntryList
-// B. Remove the thread from the WaitSet and unpark() it.
-//
-// We use (B), which is crude and results in lots of futile
-// context switching.  In particular (B) induces lots of contention.
-ParkEvent * ev = NULL ;       // consider using a small auto array ...
-RawMonitor_lock->lock_without_safepoint_check() ;
-for (;;) {
-ObjectWaiter * w = _WaitSet ;
-if (w == NULL) break ;
-_WaitSet = w->_next ;
-if (ev != NULL) { ev->unpark(); ev = NULL; }
-ev = w->_event ;
-OrderAccess::loadstore() ;
-w->TState = ObjectWaiter::TS_RUN ;
-OrderAccess::storeload();
-if (!All) break ;
-}
-RawMonitor_lock->unlock() ;
-if (ev != NULL) ev->unpark();
-return OS_OK ;
-}
-// Any JavaThread will enter here with state _thread_blocked
-int ObjectMonitor::raw_enter(TRAPS) {
-TEVENT (raw_enter) ;
-void * Contended ;
-// don't enter raw monitor if thread is being externally suspended, it will
-// surprise the suspender if a "suspended" thread can still enter monitor
-JavaThread * jt = (JavaThread *)THREAD;
-if (THREAD->is_Java_thread()) {
-jt->SR_lock()->lock_without_safepoint_check();
-while (jt->is_external_suspend()) {
-jt->SR_lock()->unlock();
-jt->java_suspend_self();
-jt->SR_lock()->lock_without_safepoint_check();
-}
-// guarded by SR_lock to avoid racing with new external suspend requests.
-Contended = Atomic::cmpxchg_ptr (THREAD, &_owner, NULL) ;
-jt->SR_lock()->unlock();
-} else {
-Contended = Atomic::cmpxchg_ptr (THREAD, &_owner, NULL) ;
-}
-if (Contended == THREAD) {
-_recursions ++ ;
-return OM_OK ;
-}
-if (Contended == NULL) {
-guarantee (_owner == THREAD, "invariant") ;
-guarantee (_recursions == 0, "invariant") ;
-return OM_OK ;
-}
-THREAD->set_current_pending_monitor(this);
-if (!THREAD->is_Java_thread()) {
-// No other non-Java threads besides VM thread would acquire
-// a raw monitor.
-assert(THREAD->is_VM_thread(), "must be VM thread");
-SimpleEnter (THREAD) ;
-} else {
-guarantee (jt->thread_state() == _thread_blocked, "invariant") ;
-for (;;) {
-jt->set_suspend_equivalent();
-// cleared by handle_special_suspend_equivalent_condition() or
-// java_suspend_self()
-SimpleEnter (THREAD) ;
-// were we externally suspended while we were waiting?
-if (!jt->handle_special_suspend_equivalent_condition()) break ;
-// This thread was externally suspended
-//
-// This logic isn't needed for JVMTI raw monitors,
-// but doesn't hurt just in case the suspend rules change. This
-// logic is needed for the ObjectMonitor.wait() reentry phase.
-// We have reentered the contended monitor, but while we were
-// waiting another thread suspended us. We don't want to reenter
-// the monitor while suspended because that would surprise the
-// thread that suspended us.
-//
-// Drop the lock -
-SimpleExit (THREAD) ;
-jt->java_suspend_self();
-}
-assert(_owner == THREAD, "Fatal error with monitor owner!");
-assert(_recursions == 0, "Fatal error with monitor recursions!");
-}
-THREAD->set_current_pending_monitor(NULL);
-guarantee (_recursions == 0, "invariant") ;
-return OM_OK;
-}
-// Used mainly for JVMTI raw monitor implementation
-// Also used for ObjectMonitor::wait().
-int ObjectMonitor::raw_exit(TRAPS) {
-TEVENT (raw_exit) ;
-if (THREAD != _owner) {
-return OM_ILLEGAL_MONITOR_STATE;
-}
-if (_recursions > 0) {
---_recursions ;
-return OM_OK ;
-}
-void * List = _EntryList ;
-SimpleExit (THREAD) ;
-return OM_OK;
-}
-// Used for JVMTI raw monitor implementation.
-// All JavaThreads will enter here with state _thread_blocked
-int ObjectMonitor::raw_wait(jlong millis, bool interruptible, TRAPS) {
-TEVENT (raw_wait) ;
-if (THREAD != _owner) {
-return OM_ILLEGAL_MONITOR_STATE;
-}
-// To avoid spurious wakeups we reset the parkevent -- This is strictly optional.
-// The caller must be able to tolerate spurious returns from raw_wait().
-THREAD->_ParkEvent->reset() ;
-OrderAccess::fence() ;
-// check interrupt event
-if (interruptible && Thread::is_interrupted(THREAD, true)) {
-return OM_INTERRUPTED;
-}
-intptr_t save = _recursions ;
-_recursions = 0 ;
-_waiters ++ ;
-if (THREAD->is_Java_thread()) {
-guarantee (((JavaThread *) THREAD)->thread_state() == _thread_blocked, "invariant") ;
-((JavaThread *)THREAD)->set_suspend_equivalent();
-}
-int rv = SimpleWait (THREAD, millis) ;
-_recursions = save ;
-_waiters -- ;
-guarantee (THREAD == _owner, "invariant") ;
-if (THREAD->is_Java_thread()) {
-JavaThread * jSelf = (JavaThread *) THREAD ;
-for (;;) {
-if (!jSelf->handle_special_suspend_equivalent_condition()) break ;
-SimpleExit (THREAD) ;
-jSelf->java_suspend_self();
-SimpleEnter (THREAD) ;
-jSelf->set_suspend_equivalent() ;
-}
-}
-guarantee (THREAD == _owner, "invariant") ;
-if (interruptible && Thread::is_interrupted(THREAD, true)) {
-return OM_INTERRUPTED;
-}
-return OM_OK ;
-}
-int ObjectMonitor::raw_notify(TRAPS) {
-TEVENT (raw_notify) ;
-if (THREAD != _owner) {
-return OM_ILLEGAL_MONITOR_STATE;
-}
-SimpleNotify (THREAD, false) ;
-return OM_OK;
-}
-int ObjectMonitor::raw_notifyAll(TRAPS) {
-TEVENT (raw_notifyAll) ;
-if (THREAD != _owner) {
-return OM_ILLEGAL_MONITOR_STATE;
-}
-SimpleNotify (THREAD, true) ;
-return OM_OK;
-}
-#ifndef PRODUCT
-void ObjectMonitor::verify() {
-}
-void ObjectMonitor::print() {
-}
-#endif
 //------------------------------------------------------------------------------
 // Non-product code
 #ifndef PRODUCT

changeset 6975	dc9b63952682
parent 5920	8fdbb85e62d3
child 7397	5b173b4ca846