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

equal deleted inserted replaced

-:513e0b467a92
+:8d15b1369c7a
 #include "runtime/init.hpp"
 #include "runtime/interfaceSupport.hpp"
 #include "runtime/java.hpp"
 #include "runtime/javaCalls.hpp"
 #include "runtime/jniPeriodicChecker.hpp"
-#include "runtime/timerTrace.hpp"
 #include "runtime/memprofiler.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "runtime/objectMonitor.hpp"
 #include "runtime/orderAccess.inline.hpp"
 #include "runtime/osThread.hpp"
+#include "runtime/prefetch.inline.hpp"
 #include "runtime/safepoint.hpp"
 #include "runtime/safepointMechanism.inline.hpp"
 #include "runtime/sharedRuntime.hpp"
 #include "runtime/statSampler.hpp"
 #include "runtime/stubRoutines.hpp"
 #include "runtime/sweeper.hpp"
 #include "runtime/task.hpp"
 #include "runtime/thread.inline.hpp"
 #include "runtime/threadCritical.hpp"
+#include "runtime/threadSMR.inline.hpp"
+#include "runtime/timer.hpp"
+#include "runtime/timerTrace.hpp"
 #include "runtime/vframe.hpp"
 #include "runtime/vframeArray.hpp"
 #include "runtime/vframe_hp.hpp"
 #include "runtime/vmThread.hpp"
 #include "runtime/vm_operations.hpp"
 #include "utilities/defaultStream.hpp"
 #include "utilities/dtrace.hpp"
 #include "utilities/events.hpp"
 #include "utilities/macros.hpp"
 #include "utilities/preserveException.hpp"
+#include "utilities/resourceHash.hpp"
 #include "utilities/vmError.hpp"
 #if INCLUDE_ALL_GCS
 #include "gc/cms/concurrentMarkSweepThread.hpp"
 #include "gc/g1/concurrentMarkThread.inline.hpp"
 #include "gc/parallel/pcTasks.hpp"
 }
 }
 void Thread::operator delete(void* p) {
 if (UseBiasedLocking) {
-void* real_malloc_addr = ((Thread*) p)->_real_malloc_address;
+FreeHeap(((Thread*) p)->_real_malloc_address);
-FreeHeap(real_malloc_addr);
 } else {
 FreeHeap(p);
 }
 }
+void JavaThread::smr_delete() {
+if (_on_thread_list) {
+Threads::smr_delete(this);
+} else {
+delete this;
+}
+}
 // Base class for all threads: VMThread, WatcherThread, ConcurrentMarkSweepThread,
 // JavaThread
 set_free_handle_block(NULL);
 set_last_handle_mark(NULL);
 // This initial value ==> never claimed.
 _oops_do_parity = 0;
+_threads_hazard_ptr = NULL;
+_nested_threads_hazard_ptr = NULL;
+_nested_threads_hazard_ptr_cnt = 0;
 // the handle mark links itself to last_handle_mark
 new HandleMark(this);
 // plain initialization
 void Thread::run() {
 ShouldNotReachHere();
 }
 #ifdef ASSERT
-// Private method to check for dangling thread pointer
+// A JavaThread is considered "dangling" if it is not the current
-void check_for_dangling_thread_pointer(Thread *thread) {
+// thread, has been added the Threads list, the system is not at a
-assert(!thread->is_Java_thread() || Thread::current() == thread || Threads_lock->owned_by_self(),
+// safepoint and the Thread is not "protected".
+//
+void Thread::check_for_dangling_thread_pointer(Thread *thread) {
+assert(!thread->is_Java_thread() || Thread::current() == thread ||
+!((JavaThread *) thread)->on_thread_list() ||
+SafepointSynchronize::is_at_safepoint() ||
+Threads::is_a_protected_JavaThread_with_lock((JavaThread *) thread),
 "possibility of dangling Thread pointer");
 }
 #endif
 ThreadPriority Thread::get_priority(const Thread* const thread) {
 // thread did not suspend after all our retries
 *bits |= 0x00200000;
 return false;
 }
+// Called from API entry points which perform stack walking. If the
+// associated JavaThread is the current thread, then wait_for_suspend
+// is not used. Otherwise, it determines if we should wait for the
+// "other" thread to complete external suspension. (NOTE: in future
+// releases the suspension mechanism should be reimplemented so this
+// is not necessary.)
+//
+bool
+JavaThread::is_thread_fully_suspended(bool wait_for_suspend, uint32_t *bits) {
+if (this != JavaThread::current()) {
+// "other" threads require special handling.
+if (wait_for_suspend) {
+// We are allowed to wait for the external suspend to complete
+// so give the other thread a chance to get suspended.
+if (!wait_for_ext_suspend_completion(SuspendRetryCount,
+SuspendRetryDelay, bits)) {
+// Didn't make it so let the caller know.
+return false;
+}
+}
+// We aren't allowed to wait for the external suspend to complete
+// so if the other thread isn't externally suspended we need to
+// let the caller know.
+else if (!is_ext_suspend_completed_with_lock(bits)) {
+return false;
+}
+}
+return true;
+}
 #ifndef PRODUCT
 void JavaThread::record_jump(address target, address instr, const char* file,
 int line) {
 // This should not need to be atomic as the only way for simultaneous
 }
 st->print("tid=" INTPTR_FORMAT " ", p2i(this));
 ext().print_on(st);
 osthread()->print_on(st);
 }
+if (_threads_hazard_ptr != NULL) {
+st->print("_threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr));
+}
+if (_nested_threads_hazard_ptr != NULL) {
+print_nested_threads_hazard_ptrs_on(st);
+}
+st->print(" ");
 debug_only(if (WizardMode) print_owned_locks_on(st);)
+}
+void Thread::print_nested_threads_hazard_ptrs_on(outputStream* st) const {
+assert(_nested_threads_hazard_ptr != NULL, "must be set to print");
+if (EnableThreadSMRStatistics) {
+st->print(", _nested_threads_hazard_ptr_cnt=%u", _nested_threads_hazard_ptr_cnt);
+}
+st->print(", _nested_threads_hazard_ptrs=");
+for (NestedThreadsList* node = _nested_threads_hazard_ptr; node != NULL;
+node = node->next()) {
+if (node != _nested_threads_hazard_ptr) {
+// First node does not need a comma-space separator.
+st->print(", ");
+}
+st->print(INTPTR_FORMAT, p2i(node->t_list()));
+}
 }
 // Thread::print_on_error() is called by fatal error handler. Don't use
 // any lock or allocate memory.
 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
 st->print(" [stack: " PTR_FORMAT "," PTR_FORMAT "]",
 p2i(stack_end()), p2i(stack_base()));
 if (osthread()) {
 st->print(" [id=%d]", osthread()->thread_id());
+}
+if (_threads_hazard_ptr != NULL) {
+st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr));
+}
+if (_nested_threads_hazard_ptr != NULL) {
+print_nested_threads_hazard_ptrs_on(st);
 }
 }
 void Thread::print_value_on(outputStream* st) const {
 if (is_Named_thread()) {
 #endif
 #ifndef PRODUCT
-// The flag: potential_vm_operation notifies if this particular safepoint state could potential
+// The flag: potential_vm_operation notifies if this particular safepoint state could potentially
-// invoke the vm-thread (i.e., and oop allocation). In that case, we also have to make sure that
+// invoke the vm-thread (e.g., an oop allocation). In that case, we also have to make sure that
 // no threads which allow_vm_block's are held
 void Thread::check_for_valid_safepoint_state(bool potential_vm_operation) {
 // Check if current thread is allowed to block at a safepoint
 if (!(_allow_safepoint_count == 0)) {
 fatal("Possible safepoint reached by thread that does not allow it");
 }
 void JavaThread::collect_counters(typeArrayOop array) {
 if (JVMCICounterSize > 0) {
 MutexLocker tl(Threads_lock);
+JavaThreadIteratorWithHandle jtiwh;
 for (int i = 0; i < array->length(); i++) {
 array->long_at_put(i, _jvmci_old_thread_counters[i]);
 }
-for (JavaThread* tp = Threads::first(); tp != NULL; tp = tp->next()) {
+for (; JavaThread *tp = jtiwh.next(); ) {
 if (jvmci_counters_include(tp)) {
 for (int i = 0; i < array->length(); i++) {
 array->long_at_put(i, array->long_at(i) + tp->_jvmci_counters[i]);
 }
 }
 set_deopt_mark(NULL);
 set_deopt_compiled_method(NULL);
 clear_must_deopt_id();
 set_monitor_chunks(NULL);
 set_next(NULL);
+_on_thread_list = false;
 set_thread_state(_thread_new);
 _terminated = _not_terminated;
 _privileged_stack_top = NULL;
 _array_for_gc = NULL;
 _suspend_equivalent = false;
 }
 DTRACE_THREAD_PROBE(stop, this);
 this->exit(false);
-delete this;
+this->smr_delete();
 }
 static void ensure_join(JavaThread* thread) {
-// We do not need to grap the Threads_lock, since we are operating on ourself.
+// We do not need to grab the Threads_lock, since we are operating on ourself.
 Handle threadObj(thread, thread->threadObj());
 assert(threadObj.not_null(), "java thread object must exist");
 ObjectLocker lock(threadObj, thread);
 // Ignore pending exception (ThreadDeath), since we are exiting anyway
 thread->clear_pending_exception();
 // For any new cleanup additions, please check to see if they need to be applied to
 // cleanup_failed_attach_current_thread as well.
 void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
 assert(this == JavaThread::current(), "thread consistency check");
+elapsedTimer _timer_exit_phase1;
+elapsedTimer _timer_exit_phase2;
+elapsedTimer _timer_exit_phase3;
+elapsedTimer _timer_exit_phase4;
+if (log_is_enabled(Debug, os, thread, timer)) {
+_timer_exit_phase1.start();
+}
 HandleMark hm(this);
 Handle uncaught_exception(this, this->pending_exception());
 this->clear_pending_exception();
 Handle threadObj(this, this->threadObj());
 // no more external suspends are allowed at this point
 } else {
 // before_exit() has already posted JVMTI THREAD_END events
 }
+if (log_is_enabled(Debug, os, thread, timer)) {
+_timer_exit_phase1.stop();
+_timer_exit_phase2.start();
+}
 // Notify waiters on thread object. This has to be done after exit() is called
 // on the thread (if the thread is the last thread in a daemon ThreadGroup the
 // group should have the destroyed bit set before waiters are notified).
 ensure_join(this);
 assert(!this->has_pending_exception(), "ensure_join should have cleared");
+if (log_is_enabled(Debug, os, thread, timer)) {
+_timer_exit_phase2.stop();
+_timer_exit_phase3.start();
+}
 // 6282335 JNI DetachCurrentThread spec states that all Java monitors
 // held by this thread must be released. The spec does not distinguish
 // between JNI-acquired and regular Java monitors. We can only see
 // regular Java monitors here if monitor enter-exit matching is broken.
 //
 log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
 exit_type == JavaThread::normal_exit ? "exiting" : "detaching",
 os::current_thread_id());
+if (log_is_enabled(Debug, os, thread, timer)) {
+_timer_exit_phase3.stop();
+_timer_exit_phase4.start();
+}
 // Remove from list of active threads list, and notify VM thread if we are the last non-daemon thread
 Threads::remove(this);
-// If someone set a handshake on us just as we entered exit path, we simple cancel it.
+if (log_is_enabled(Debug, os, thread, timer)) {
-if (ThreadLocalHandshakes) {
+_timer_exit_phase4.stop();
-cancel_handshake();
+ResourceMark rm(this);
+log_debug(os, thread, timer)("name='%s'"
+", exit-phase1=" JLONG_FORMAT
+", exit-phase2=" JLONG_FORMAT
+", exit-phase3=" JLONG_FORMAT
+", exit-phase4=" JLONG_FORMAT,
+get_thread_name(),
+_timer_exit_phase1.milliseconds(),
+_timer_exit_phase2.milliseconds(),
+_timer_exit_phase3.milliseconds(),
+_timer_exit_phase4.milliseconds());
 }
 }
 #if INCLUDE_ALL_GCS
 // Flush G1-related queues.
 flush_barrier_queues();
 }
 #endif // INCLUDE_ALL_GCS
 Threads::remove(this);
-delete this;
+this->smr_delete();
 }
 //   + Target thread will not execute any new bytecode (that's why we need to
 //     force a safepoint)
 //   + Target thread will not enter any new monitors
 //
 void JavaThread::java_suspend() {
-{ MutexLocker mu(Threads_lock);
+ThreadsListHandle tlh;
-if (!Threads::includes(this) || is_exiting() || this->threadObj() == NULL) {
+if (!tlh.includes(this) || threadObj() == NULL || is_exiting()) {
 return;
-}
 }
 { MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 if (!is_external_suspend()) {
 // a racing resume has cancelled us; bail out now
 #ifdef ASSERT
 // verify the JavaThread has not yet been published in the Threads::list, and
 // hence doesn't need protection from concurrent access at this stage
 void JavaThread::verify_not_published() {
-if (!Threads_lock->owned_by_self()) {
+ThreadsListHandle tlh;
-MutexLockerEx ml(Threads_lock,  Mutex::_no_safepoint_check_flag);
+assert(!tlh.includes(this), "JavaThread shouldn't have been published yet!");
-assert(!Threads::includes(this),
-"java thread shouldn't have been published yet!");
-} else {
-assert(!Threads::includes(this),
-"java thread shouldn't have been published yet!");
-}
 }
 #endif
 // Slow path when the native==>VM/Java barriers detect a safepoint is in
 // progress or when _suspend_flags is non-zero.
 void JavaThread::java_resume() {
 assert_locked_or_safepoint(Threads_lock);
 // Sanity check: thread is gone, has started exiting or the thread
 // was not externally suspended.
-if (!Threads::includes(this) || is_exiting() || !is_external_suspend()) {
+ThreadsListHandle tlh;
+if (!tlh.includes(this) || is_exiting() || !is_external_suspend()) {
 return;
 }
 MutexLockerEx ml(SR_lock(), Mutex::_no_safepoint_check_flag);
 st->print(", id=%d", osthread()->thread_id());
 }
 st->print(", stack(" PTR_FORMAT "," PTR_FORMAT ")",
 p2i(stack_end()), p2i(stack_base()));
 st->print("]");
+if (_threads_hazard_ptr != NULL) {
+st->print(" _threads_hazard_ptr=" INTPTR_FORMAT, p2i(_threads_hazard_ptr));
+}
+if (_nested_threads_hazard_ptr != NULL) {
+print_nested_threads_hazard_ptrs_on(st);
+}
 return;
 }
 // Verification
 // ======= Threads ========
 // The Threads class links together all active threads, and provides
-// operations over all threads.  It is protected by its own Mutex
+// operations over all threads. It is protected by the Threads_lock,
-// lock, which is also used in other contexts to protect thread
+// which is also used in other global contexts like safepointing.
-// operations from having the thread being operated on from exiting
+// ThreadsListHandles are used to safely perform operations on one
-// and going away unexpectedly (e.g., safepoint synchronization)
+// or more threads without the risk of the thread exiting during the
+// operation.
-JavaThread* Threads::_thread_list = NULL;
+//
-int         Threads::_number_of_threads = 0;
+// Note: The Threads_lock is currently more widely used than we
-int         Threads::_number_of_non_daemon_threads = 0;
+// would like. We are actively migrating Threads_lock uses to other
-int         Threads::_return_code = 0;
+// mechanisms in order to reduce Threads_lock contention.
-int         Threads::_thread_claim_parity = 0;
-size_t      JavaThread::_stack_size_at_create = 0;
+JavaThread*           Threads::_thread_list = NULL;
+int                   Threads::_number_of_threads = 0;
+int                   Threads::_number_of_non_daemon_threads = 0;
+int                   Threads::_return_code = 0;
+int                   Threads::_thread_claim_parity = 0;
+size_t                JavaThread::_stack_size_at_create = 0;
+// Safe Memory Reclamation (SMR) support:
+Monitor*              Threads::_smr_delete_lock =
+new Monitor(Monitor::special, "smr_delete_lock",
+false /* allow_vm_block */,
+Monitor::_safepoint_check_never);
+// The '_cnt', '_max' and '_times" fields are enabled via
+// -XX:+EnableThreadSMRStatistics:
+// # of parallel threads in _smr_delete_lock->wait().
+// Impl note: Hard to imagine > 64K waiting threads so this could be 16-bit,
+// but there is no nice 16-bit _FORMAT support.
+uint                  Threads::_smr_delete_lock_wait_cnt = 0;
+// Max # of parallel threads in _smr_delete_lock->wait().
+// Impl note: See _smr_delete_lock_wait_cnt note.
+uint                  Threads::_smr_delete_lock_wait_max = 0;
+// Flag to indicate when an _smr_delete_lock->notify() is needed.
+// Impl note: See _smr_delete_lock_wait_cnt note.
+volatile uint         Threads::_smr_delete_notify = 0;
+// # of threads deleted over VM lifetime.
+// Impl note: Atomically incremented over VM lifetime so use unsigned for more
+// range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc
+// isn't available everywhere (or is it?).
+volatile uint         Threads::_smr_deleted_thread_cnt = 0;
+// Max time in millis to delete a thread.
+// Impl note: 16-bit might be too small on an overloaded machine. Use
+// unsigned since this is a time value. Set via Atomic::cmpxchg() in a
+// loop for correctness.
+volatile uint         Threads::_smr_deleted_thread_time_max = 0;
+// Cumulative time in millis to delete threads.
+// Impl note: Atomically added to over VM lifetime so use unsigned for more
+// range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc
+// isn't available everywhere (or is it?).
+volatile uint         Threads::_smr_deleted_thread_times = 0;
+ThreadsList* volatile Threads::_smr_java_thread_list = new ThreadsList(0);
+// # of ThreadsLists allocated over VM lifetime.
+// Impl note: We allocate a new ThreadsList for every thread create and
+// every thread delete so we need a bigger type than the
+// _smr_deleted_thread_cnt field.
+uint64_t              Threads::_smr_java_thread_list_alloc_cnt = 1;
+// # of ThreadsLists freed over VM lifetime.
+// Impl note: See _smr_java_thread_list_alloc_cnt note.
+uint64_t              Threads::_smr_java_thread_list_free_cnt = 0;
+// Max size ThreadsList allocated.
+// Impl note: Max # of threads alive at one time should fit in unsigned 32-bit.
+uint                  Threads::_smr_java_thread_list_max = 0;
+// Max # of nested ThreadsLists for a thread.
+// Impl note: Hard to imagine > 64K nested ThreadsLists so this could be
+// 16-bit, but there is no nice 16-bit _FORMAT support.
+uint                  Threads::_smr_nested_thread_list_max = 0;
+// # of ThreadsListHandles deleted over VM lifetime.
+// Impl note: Atomically incremented over VM lifetime so use unsigned for
+// more range. There will be fewer ThreadsListHandles than threads so
+// unsigned 32-bit should be fine.
+volatile uint         Threads::_smr_tlh_cnt = 0;
+// Max time in millis to delete a ThreadsListHandle.
+// Impl note: 16-bit might be too small on an overloaded machine. Use
+// unsigned since this is a time value. Set via Atomic::cmpxchg() in a
+// loop for correctness.
+volatile uint         Threads::_smr_tlh_time_max = 0;
+// Cumulative time in millis to delete ThreadsListHandles.
+// Impl note: Atomically added to over VM lifetime so use unsigned for more
+// range. Unsigned 64-bit would be more future proof, but 64-bit atomic inc
+// isn't available everywhere (or is it?).
+volatile uint         Threads::_smr_tlh_times = 0;
+ThreadsList*          Threads::_smr_to_delete_list = NULL;
+// # of parallel ThreadsLists on the to-delete list.
+// Impl note: Hard to imagine > 64K ThreadsLists needing to be deleted so
+// this could be 16-bit, but there is no nice 16-bit _FORMAT support.
+uint                  Threads::_smr_to_delete_list_cnt = 0;
+// Max # of parallel ThreadsLists on the to-delete list.
+// Impl note: See _smr_to_delete_list_cnt note.
+uint                  Threads::_smr_to_delete_list_max = 0;
 #ifdef ASSERT
-bool        Threads::_vm_complete = false;
+bool                  Threads::_vm_complete = false;
 #endif
+static inline void *prefetch_and_load_ptr(void **addr, intx prefetch_interval) {
+Prefetch::read((void*)addr, prefetch_interval);
+return *addr;
+}
+// Possibly the ugliest for loop the world has seen. C++ does not allow
+// multiple types in the declaration section of the for loop. In this case
+// we are only dealing with pointers and hence can cast them. It looks ugly
+// but macros are ugly and therefore it's fine to make things absurdly ugly.
+#define DO_JAVA_THREADS(LIST, X)                                                                                          \
+for (JavaThread *MACRO_scan_interval = (JavaThread*)(uintptr_t)PrefetchScanIntervalInBytes,                           \
+*MACRO_list = (JavaThread*)(LIST),                                                                           \
+**MACRO_end = ((JavaThread**)((ThreadsList*)MACRO_list)->threads()) + ((ThreadsList*)MACRO_list)->length(),  \
+**MACRO_current_p = (JavaThread**)((ThreadsList*)MACRO_list)->threads(),                                     \
+*X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval);                 \
+MACRO_current_p != MACRO_end;                                                                                    \
+MACRO_current_p++,                                                                                               \
+X = (JavaThread*)prefetch_and_load_ptr((void**)MACRO_current_p, (intx)MACRO_scan_interval))
 // All JavaThreads
-#define ALL_JAVA_THREADS(X) for (JavaThread* X = _thread_list; X; X = X->next())
+#define ALL_JAVA_THREADS(X) DO_JAVA_THREADS(get_smr_java_thread_list(), X)
 // All JavaThreads + all non-JavaThreads (i.e., every thread in the system)
 void Threads::threads_do(ThreadClosure* tc) {
 assert_locked_or_safepoint(Threads_lock);
 // ALL_JAVA_THREADS iterates through all JavaThreads
 JavaValue result(T_VOID);
 JavaCalls::call_static(&result, klass, vmSymbols::initPhase3_name(),
 vmSymbols::void_method_signature(), CHECK);
 }
+// Safe Memory Reclamation (SMR) support:
+//
+// Acquire a stable ThreadsList.
+//
+ThreadsList *Threads::acquire_stable_list(Thread *self, bool is_ThreadsListSetter) {
+assert(self != NULL, "sanity check");
+// acquire_stable_list_nested_path() will grab the Threads_lock
+// so let's make sure the ThreadsListHandle is in a safe place.
+// ThreadsListSetter cannot make this check on this code path.
+debug_only(if (!is_ThreadsListSetter && StrictSafepointChecks) self->check_for_valid_safepoint_state(/* potential_vm_operation */ false);)
+if (self->get_threads_hazard_ptr() == NULL) {
+// The typical case is first.
+return acquire_stable_list_fast_path(self);
+}
+// The nested case is rare.
+return acquire_stable_list_nested_path(self);
+}
+// Fast path (and lock free) way to acquire a stable ThreadsList.
+//
+ThreadsList *Threads::acquire_stable_list_fast_path(Thread *self) {
+assert(self != NULL, "sanity check");
+assert(self->get_threads_hazard_ptr() == NULL, "sanity check");
+assert(self->get_nested_threads_hazard_ptr() == NULL,
+"cannot have a nested hazard ptr with a NULL regular hazard ptr");
+ThreadsList* threads;
+// Stable recording of a hazard ptr for SMR. This code does not use
+// locks so its use of the _smr_java_thread_list & _threads_hazard_ptr
+// fields is racy relative to code that uses those fields with locks.
+// OrderAccess and Atomic functions are used to deal with those races.
+//
+while (true) {
+threads = get_smr_java_thread_list();
+// Publish a tagged hazard ptr to denote that the hazard ptr is not
+// yet verified as being stable. Due to the fence after the hazard
+// ptr write, it will be sequentially consistent w.r.t. the
+// sequentially consistent writes of the ThreadsList, even on
+// non-multiple copy atomic machines where stores can be observed
+// in different order from different observer threads.
+ThreadsList* unverified_threads = Thread::tag_hazard_ptr(threads);
+self->set_threads_hazard_ptr(unverified_threads);
+// If _smr_java_thread_list has changed, we have lost a race with
+// Threads::add() or Threads::remove() and have to try again.
+if (get_smr_java_thread_list() != threads) {
+continue;
+}
+// We try to remove the tag which will verify the hazard ptr as
+// being stable. This exchange can race with a scanning thread
+// which might invalidate the tagged hazard ptr to keep it from
+// being followed to access JavaThread ptrs. If we lose the race,
+// we simply retry. If we win the race, then the stable hazard
+// ptr is officially published.
+if (self->cmpxchg_threads_hazard_ptr(threads, unverified_threads) == unverified_threads) {
+break;
+}
+}
+// A stable hazard ptr has been published letting other threads know
+// that the ThreadsList and the JavaThreads reachable from this list
+// are protected and hence they should not be deleted until everyone
+// agrees it is safe to do so.
+return threads;
+}
+// Acquire a nested stable ThreadsList; this is rare so it uses
+// Threads_lock.
+//
+ThreadsList *Threads::acquire_stable_list_nested_path(Thread *self) {
+assert(self != NULL, "sanity check");
+assert(self->get_threads_hazard_ptr() != NULL,
+"cannot have a NULL regular hazard ptr when acquiring a nested hazard ptr");
+// The thread already has a hazard ptr (ThreadsList ref) so we need
+// to create a nested ThreadsListHandle with the current ThreadsList
+// since it might be different than our current hazard ptr. The need
+// for a nested ThreadsListHandle is rare so we do this while holding
+// the Threads_lock so we don't race with the scanning code; the code
+// is so much simpler this way.
+NestedThreadsList* node;
+{
+// Only grab the Threads_lock if we don't already own it.
+MutexLockerEx ml(Threads_lock->owned_by_self() ? NULL : Threads_lock);
+node = new NestedThreadsList(get_smr_java_thread_list());
+// We insert at the front of the list to match up with the delete
+// in release_stable_list().
+node->set_next(self->get_nested_threads_hazard_ptr());
+self->set_nested_threads_hazard_ptr(node);
+if (EnableThreadSMRStatistics) {
+self->inc_nested_threads_hazard_ptr_cnt();
+if (self->nested_threads_hazard_ptr_cnt() > _smr_nested_thread_list_max) {
+_smr_nested_thread_list_max = self->nested_threads_hazard_ptr_cnt();
+}
+}
+}
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::acquire_stable_list: add NestedThreadsList node containing ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(node->t_list()));
+return node->t_list();
+}
+// Release a stable ThreadsList.
+//
+void Threads::release_stable_list(Thread *self) {
+assert(self != NULL, "sanity check");
+// release_stable_list_nested_path() will grab the Threads_lock
+// so let's make sure the ThreadsListHandle is in a safe place.
+debug_only(if (StrictSafepointChecks) self->check_for_valid_safepoint_state(/* potential_vm_operation */ false);)
+if (self->get_nested_threads_hazard_ptr() == NULL) {
+// The typical case is first.
+release_stable_list_fast_path(self);
+return;
+}
+// The nested case is rare.
+release_stable_list_nested_path(self);
+}
+// Fast path way to release a stable ThreadsList. The release portion
+// is lock-free, but the wake up portion is not.
+//
+void Threads::release_stable_list_fast_path(Thread *self) {
+assert(self != NULL, "sanity check");
+assert(self->get_threads_hazard_ptr() != NULL, "sanity check");
+assert(self->get_nested_threads_hazard_ptr() == NULL,
+"cannot have a nested hazard ptr when releasing a regular hazard ptr");
+// After releasing the hazard ptr, other threads may go ahead and
+// free up some memory temporarily used by a ThreadsList snapshot.
+self->set_threads_hazard_ptr(NULL);
+// We use double-check locking to reduce traffic on the system
+// wide smr_delete_lock.
+if (Threads::smr_delete_notify()) {
+// An exiting thread might be waiting in smr_delete(); we need to
+// check with smr_delete_lock to be sure.
+release_stable_list_wake_up((char *) "regular hazard ptr");
+}
+}
+// Release a nested stable ThreadsList; this is rare so it uses
+// Threads_lock.
+//
+void Threads::release_stable_list_nested_path(Thread *self) {
+assert(self != NULL, "sanity check");
+assert(self->get_nested_threads_hazard_ptr() != NULL, "sanity check");
+assert(self->get_threads_hazard_ptr() != NULL,
+"must have a regular hazard ptr to have nested hazard ptrs");
+// We have a nested ThreadsListHandle so we have to release it first.
+// The need for a nested ThreadsListHandle is rare so we do this while
+// holding the Threads_lock so we don't race with the scanning code;
+// the code is so much simpler this way.
+NestedThreadsList *node;
+{
+// Only grab the Threads_lock if we don't already own it.
+MutexLockerEx ml(Threads_lock->owned_by_self() ? NULL : Threads_lock);
+// We remove from the front of the list to match up with the insert
+// in acquire_stable_list().
+node = self->get_nested_threads_hazard_ptr();
+self->set_nested_threads_hazard_ptr(node->next());
+if (EnableThreadSMRStatistics) {
+self->dec_nested_threads_hazard_ptr_cnt();
+}
+}
+// An exiting thread might be waiting in smr_delete(); we need to
+// check with smr_delete_lock to be sure.
+release_stable_list_wake_up((char *) "nested hazard ptr");
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::release_stable_list: delete NestedThreadsList node containing ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(node->t_list()));
+delete node;
+}
+// Wake up portion of the release stable ThreadsList protocol;
+// uses the smr_delete_lock().
+//
+void Threads::release_stable_list_wake_up(char *log_str) {
+assert(log_str != NULL, "sanity check");
+// Note: smr_delete_lock is held in smr_delete() for the entire
+// hazard ptr search so that we do not lose this notify() if
+// the exiting thread has to wait. That code path also holds
+// Threads_lock (which was grabbed before smr_delete_lock) so that
+// threads_do() can be called. This means the system can't start a
+// safepoint which means this thread can't take too long to get to
+// a safepoint because of being blocked on smr_delete_lock.
+//
+MonitorLockerEx ml(Threads::smr_delete_lock(), Monitor::_no_safepoint_check_flag);
+if (Threads::smr_delete_notify()) {
+// Notify any exiting JavaThreads that are waiting in smr_delete()
+// that we've released a ThreadsList.
+ml.notify_all();
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::release_stable_list notified %s", os::current_thread_id(), log_str);
+}
+}
 void Threads::initialize_java_lang_classes(JavaThread* main_thread, TRAPS) {
 TraceTime timer("Initialize java.lang classes", TRACETIME_LOG(Info, startuptime));
 if (EagerXrunInit && Arguments::init_libraries_at_startup()) {
 create_vm_init_libraries();
 main_thread->set_active_handles(JNIHandleBlock::allocate_block());
 if (!main_thread->set_as_starting_thread()) {
 vm_shutdown_during_initialization(
 "Failed necessary internal allocation. Out of swap space");
-delete main_thread;
+main_thread->smr_delete();
 *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
 return JNI_ENOMEM;
 }
 // Enable guard page *after* os::create_main_thread(), otherwise it would
 ObjectMonitor::Initialize();
 // Initialize global modules
 jint status = init_globals();
 if (status != JNI_OK) {
-delete main_thread;
+main_thread->smr_delete();
 *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
 return status;
 }
 if (TRACE_INITIALIZE() != JNI_OK) {
 vm_exit_during_initialization("Could not find JVM_OnLoad function in -Xrun library", agent->name());
 }
 }
 }
-JavaThread* Threads::find_java_thread_from_java_tid(jlong java_tid) {
-assert(Threads_lock->owned_by_self(), "Must hold Threads_lock");
-JavaThread* java_thread = NULL;
-// Sequential search for now.  Need to do better optimization later.
-for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
-oop tobj = thread->threadObj();
-if (!thread->is_exiting() &&
-tobj != NULL &&
-java_tid == java_lang_Thread::thread_id(tobj)) {
-java_thread = thread;
-break;
-}
-}
-return java_thread;
-}
 // Last thread running calls java.lang.Shutdown.shutdown()
 void JavaThread::invoke_shutdown_hooks() {
 HandleMark hm(this);
 VM_Exit::set_vm_exited();
 notify_vm_shutdown();
+// We are after VM_Exit::set_vm_exited() so we can't call
+// thread->smr_delete() or we will block on the Threads_lock.
+// Deleting the shutdown thread here is safe because another
+// JavaThread cannot have an active ThreadsListHandle for
+// this JavaThread.
 delete thread;
 #if INCLUDE_JVMCI
 if (JVMCICounterSize > 0) {
 FREE_C_HEAP_ARRAY(jlong, JavaThread::_jvmci_old_thread_counters);
 if (version == JNI_VERSION_9) return JNI_TRUE;
 if (version == JNI_VERSION_10) return JNI_TRUE;
 return JNI_FALSE;
 }
+// Hash table of pointers found by a scan. Used for collecting hazard
+// pointers (ThreadsList references). Also used for collecting JavaThreads
+// that are indirectly referenced by hazard ptrs. An instance of this
+// class only contains one type of pointer.
+//
+class ThreadScanHashtable : public CHeapObj<mtThread> {
+private:
+static bool ptr_equals(void * const& s1, void * const& s2) {
+return s1 == s2;
+}
+static unsigned int ptr_hash(void * const& s1) {
+// 2654435761 = 2^32 * Phi (golden ratio)
+return (unsigned int)(((uint32_t)(uintptr_t)s1) * 2654435761u);
+}
+int _table_size;
+// ResourceHashtable SIZE is specified at compile time so our
+// dynamic _table_size is unused for now; 1031 is the first prime
+// after 1024.
+typedef ResourceHashtable<void *, int, &ThreadScanHashtable::ptr_hash,
+&ThreadScanHashtable::ptr_equals, 1031,
+ResourceObj::C_HEAP, mtThread> PtrTable;
+PtrTable * _ptrs;
+public:
+// ResourceHashtable is passed to various functions and populated in
+// different places so we allocate it using C_HEAP to make it immune
+// from any ResourceMarks that happen to be in the code paths.
+ThreadScanHashtable(int table_size) : _table_size(table_size), _ptrs(new (ResourceObj::C_HEAP, mtThread) PtrTable()) {}
+~ThreadScanHashtable() { delete _ptrs; }
+bool has_entry(void *pointer) {
+int *val_ptr = _ptrs->get(pointer);
+return val_ptr != NULL && *val_ptr == 1;
+}
+void add_entry(void *pointer) {
+_ptrs->put(pointer, 1);
+}
+};
+// Closure to gather JavaThreads indirectly referenced by hazard ptrs
+// (ThreadsList references) into a hash table. This closure handles part 2
+// of the dance - adding all the JavaThreads referenced by the hazard
+// pointer (ThreadsList reference) to the hash table.
+//
+class AddThreadHazardPointerThreadClosure : public ThreadClosure {
+private:
+ThreadScanHashtable *_table;
+public:
+AddThreadHazardPointerThreadClosure(ThreadScanHashtable *table) : _table(table) {}
+virtual void do_thread(Thread *thread) {
+if (!_table->has_entry((void*)thread)) {
+// The same JavaThread might be on more than one ThreadsList or
+// more than one thread might be using the same ThreadsList. In
+// either case, we only need a single entry for a JavaThread.
+_table->add_entry((void*)thread);
+}
+}
+};
+// Closure to gather JavaThreads indirectly referenced by hazard ptrs
+// (ThreadsList references) into a hash table. This closure handles part 1
+// of the dance - hazard ptr chain walking and dispatch to another
+// closure.
+//
+class ScanHazardPtrGatherProtectedThreadsClosure : public ThreadClosure {
+private:
+ThreadScanHashtable *_table;
+public:
+ScanHazardPtrGatherProtectedThreadsClosure(ThreadScanHashtable *table) : _table(table) {}
+virtual void do_thread(Thread *thread) {
+assert_locked_or_safepoint(Threads_lock);
+if (thread == NULL) return;
+// This code races with Threads::acquire_stable_list() which is
+// lock-free so we have to handle some special situations.
+//
+ThreadsList *current_list = NULL;
+while (true) {
+current_list = thread->get_threads_hazard_ptr();
+// No hazard ptr so nothing more to do.
+if (current_list == NULL) {
+assert(thread->get_nested_threads_hazard_ptr() == NULL,
+"cannot have a nested hazard ptr with a NULL regular hazard ptr");
+return;
+}
+// If the hazard ptr is verified as stable (since it is not tagged),
+// then it is safe to use.
+if (!Thread::is_hazard_ptr_tagged(current_list)) break;
+// The hazard ptr is tagged as not yet verified as being stable
+// so we are racing with acquire_stable_list(). This exchange
+// attempts to invalidate the hazard ptr. If we win the race,
+// then we can ignore this unstable hazard ptr and the other
+// thread will retry the attempt to publish a stable hazard ptr.
+// If we lose the race, then we retry our attempt to look at the
+// hazard ptr.
+if (thread->cmpxchg_threads_hazard_ptr(NULL, current_list) == current_list) return;
+}
+// The current JavaThread has a hazard ptr (ThreadsList reference)
+// which might be _smr_java_thread_list or it might be an older
+// ThreadsList that has been removed but not freed. In either case,
+// the hazard ptr is protecting all the JavaThreads on that
+// ThreadsList.
+AddThreadHazardPointerThreadClosure add_cl(_table);
+current_list->threads_do(&add_cl);
+// Any NestedThreadsLists are also protecting JavaThreads so
+// gather those also; the ThreadsLists may be different.
+for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr();
+node != NULL; node = node->next()) {
+node->t_list()->threads_do(&add_cl);
+}
+}
+};
+// Closure to print JavaThreads that have a hazard ptr (ThreadsList
+// reference) that contains an indirect reference to a specific JavaThread.
+//
+class ScanHazardPtrPrintMatchingThreadsClosure : public ThreadClosure {
+private:
+JavaThread *_thread;
+public:
+ScanHazardPtrPrintMatchingThreadsClosure(JavaThread *thread) : _thread(thread) {}
+virtual void do_thread(Thread *thread) {
+assert_locked_or_safepoint(Threads_lock);
+if (thread == NULL) return;
+ThreadsList *current_list = thread->get_threads_hazard_ptr();
+if (current_list == NULL) {
+assert(thread->get_nested_threads_hazard_ptr() == NULL,
+"cannot have a nested hazard ptr with a NULL regular hazard ptr");
+return;
+}
+// If the hazard ptr is unverified, then ignore it.
+if (Thread::is_hazard_ptr_tagged(current_list)) return;
+// The current JavaThread has a hazard ptr (ThreadsList reference)
+// which might be _smr_java_thread_list or it might be an older
+// ThreadsList that has been removed but not freed. In either case,
+// the hazard ptr is protecting all the JavaThreads on that
+// ThreadsList, but we only care about matching a specific JavaThread.
+DO_JAVA_THREADS(current_list, p) {
+if (p == _thread) {
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread1=" INTPTR_FORMAT " has a hazard pointer for thread2=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread), p2i(_thread));
+break;
+}
+}
+// Any NestedThreadsLists are also protecting JavaThreads so
+// check those also; the ThreadsLists may be different.
+for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr();
+node != NULL; node = node->next()) {
+DO_JAVA_THREADS(node->t_list(), p) {
+if (p == _thread) {
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread1=" INTPTR_FORMAT " has a nested hazard pointer for thread2=" INTPTR_FORMAT, os::current_thread_id(), p2i(thread), p2i(_thread));
+return;
+}
+}
+}
+}
+};
+// Return true if the specified JavaThread is protected by a hazard
+// pointer (ThreadsList reference). Otherwise, returns false.
+//
+bool Threads::is_a_protected_JavaThread(JavaThread *thread) {
+assert_locked_or_safepoint(Threads_lock);
+// Hash table size should be first power of two higher than twice
+// the length of the Threads list.
+int hash_table_size = MIN2(_number_of_threads, 32) << 1;
+hash_table_size--;
+hash_table_size |= hash_table_size >> 1;
+hash_table_size |= hash_table_size >> 2;
+hash_table_size |= hash_table_size >> 4;
+hash_table_size |= hash_table_size >> 8;
+hash_table_size |= hash_table_size >> 16;
+hash_table_size++;
+// Gather a hash table of the JavaThreads indirectly referenced by
+// hazard ptrs.
+ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size);
+ScanHazardPtrGatherProtectedThreadsClosure scan_cl(scan_table);
+Threads::threads_do(&scan_cl);
+bool thread_is_protected = false;
+if (scan_table->has_entry((void*)thread)) {
+thread_is_protected = true;
+}
+delete scan_table;
+return thread_is_protected;
+}
+// Safely delete a JavaThread when it is no longer in use by a
+// ThreadsListHandle.
+//
+void Threads::smr_delete(JavaThread *thread) {
+assert(!Threads_lock->owned_by_self(), "sanity");
+bool has_logged_once = false;
+elapsedTimer timer;
+if (EnableThreadSMRStatistics) {
+timer.start();
+}
+while (true) {
+{
+// No safepoint check because this JavaThread is not on the
+// Threads list.
+MutexLockerEx ml(Threads_lock, Mutex::_no_safepoint_check_flag);
+// Cannot use a MonitorLockerEx helper here because we have
+// to drop the Threads_lock first if we wait.
+Threads::smr_delete_lock()->lock_without_safepoint_check();
+// Set the smr_delete_notify flag after we grab smr_delete_lock
+// and before we scan hazard ptrs because we're doing
+// double-check locking in release_stable_list().
+Threads::set_smr_delete_notify();
+if (!is_a_protected_JavaThread(thread)) {
+// This is the common case.
+Threads::clear_smr_delete_notify();
+Threads::smr_delete_lock()->unlock();
+break;
+}
+if (!has_logged_once) {
+has_logged_once = true;
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread=" INTPTR_FORMAT " is not deleted.", os::current_thread_id(), p2i(thread));
+if (log_is_enabled(Debug, os, thread)) {
+ScanHazardPtrPrintMatchingThreadsClosure scan_cl(thread);
+Threads::threads_do(&scan_cl);
+}
+}
+} // We have to drop the Threads_lock to wait or delete the thread
+if (EnableThreadSMRStatistics) {
+_smr_delete_lock_wait_cnt++;
+if (_smr_delete_lock_wait_cnt > _smr_delete_lock_wait_max) {
+_smr_delete_lock_wait_max = _smr_delete_lock_wait_cnt;
+}
+}
+// Wait for a release_stable_list() call before we check again. No
+// safepoint check, no timeout, and not as suspend equivalent flag
+// because this JavaThread is not on the Threads list.
+Threads::smr_delete_lock()->wait(Mutex::_no_safepoint_check_flag, 0,
+!Mutex::_as_suspend_equivalent_flag);
+if (EnableThreadSMRStatistics) {
+_smr_delete_lock_wait_cnt--;
+}
+Threads::clear_smr_delete_notify();
+Threads::smr_delete_lock()->unlock();
+// Retry the whole scenario.
+}
+if (ThreadLocalHandshakes) {
+// The thread is about to be deleted so cancel any handshake.
+thread->cancel_handshake();
+}
+delete thread;
+if (EnableThreadSMRStatistics) {
+timer.stop();
+uint millis = (uint)timer.milliseconds();
+Threads::inc_smr_deleted_thread_cnt();
+Threads::add_smr_deleted_thread_times(millis);
+Threads::update_smr_deleted_thread_time_max(millis);
+}
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_delete: thread=" INTPTR_FORMAT " is deleted.", os::current_thread_id(), p2i(thread));
+}
+bool Threads::smr_delete_notify() {
+// Use load_acquire() in order to see any updates to _smr_delete_notify
+// earlier than when smr_delete_lock is grabbed.
+return (OrderAccess::load_acquire(&_smr_delete_notify) != 0);
+}
+// set_smr_delete_notify() and clear_smr_delete_notify() are called
+// under the protection of the smr_delete_lock, but we also use an
+// Atomic operation to ensure the memory update is seen earlier than
+// when the smr_delete_lock is dropped.
+//
+void Threads::set_smr_delete_notify() {
+Atomic::inc(&_smr_delete_notify);
+}
+void Threads::clear_smr_delete_notify() {
+Atomic::dec(&_smr_delete_notify);
+}
+// Closure to gather hazard ptrs (ThreadsList references) into a hash table.
+//
+class ScanHazardPtrGatherThreadsListClosure : public ThreadClosure {
+private:
+ThreadScanHashtable *_table;
+public:
+ScanHazardPtrGatherThreadsListClosure(ThreadScanHashtable *table) : _table(table) {}
+virtual void do_thread(Thread* thread) {
+assert_locked_or_safepoint(Threads_lock);
+if (thread == NULL) return;
+ThreadsList *threads = thread->get_threads_hazard_ptr();
+if (threads == NULL) {
+assert(thread->get_nested_threads_hazard_ptr() == NULL,
+"cannot have a nested hazard ptr with a NULL regular hazard ptr");
+return;
+}
+// In this closure we always ignore the tag that might mark this
+// hazard ptr as not yet verified. If we happen to catch an
+// unverified hazard ptr that is subsequently discarded (not
+// published), then the only side effect is that we might keep a
+// to-be-deleted ThreadsList alive a little longer.
+threads = Thread::untag_hazard_ptr(threads);
+if (!_table->has_entry((void*)threads)) {
+_table->add_entry((void*)threads);
+}
+// Any NestedThreadsLists are also protecting JavaThreads so
+// gather those also; the ThreadsLists may be different.
+for (NestedThreadsList* node = thread->get_nested_threads_hazard_ptr();
+node != NULL; node = node->next()) {
+threads = node->t_list();
+if (!_table->has_entry((void*)threads)) {
+_table->add_entry((void*)threads);
+}
+}
+}
+};
+// Safely free a ThreadsList after a Threads::add() or Threads::remove().
+// The specified ThreadsList may not get deleted during this call if it
+// is still in-use (referenced by a hazard ptr). Other ThreadsLists
+// in the chain may get deleted by this call if they are no longer in-use.
+void Threads::smr_free_list(ThreadsList* threads) {
+assert_locked_or_safepoint(Threads_lock);
+threads->set_next_list(_smr_to_delete_list);
+_smr_to_delete_list = threads;
+if (EnableThreadSMRStatistics) {
+_smr_to_delete_list_cnt++;
+if (_smr_to_delete_list_cnt > _smr_to_delete_list_max) {
+_smr_to_delete_list_max = _smr_to_delete_list_cnt;
+}
+}
+// Hash table size should be first power of two higher than twice the length of the ThreadsList
+int hash_table_size = MIN2(_number_of_threads, 32) << 1;
+hash_table_size--;
+hash_table_size |= hash_table_size >> 1;
+hash_table_size |= hash_table_size >> 2;
+hash_table_size |= hash_table_size >> 4;
+hash_table_size |= hash_table_size >> 8;
+hash_table_size |= hash_table_size >> 16;
+hash_table_size++;
+// Gather a hash table of the current hazard ptrs:
+ThreadScanHashtable *scan_table = new ThreadScanHashtable(hash_table_size);
+ScanHazardPtrGatherThreadsListClosure scan_cl(scan_table);
+Threads::threads_do(&scan_cl);
+// Walk through the linked list of pending freeable ThreadsLists
+// and free the ones that are not referenced from hazard ptrs.
+ThreadsList* current = _smr_to_delete_list;
+ThreadsList* prev = NULL;
+ThreadsList* next = NULL;
+bool threads_is_freed = false;
+while (current != NULL) {
+next = current->next_list();
+if (!scan_table->has_entry((void*)current)) {
+// This ThreadsList is not referenced by a hazard ptr.
+if (prev != NULL) {
+prev->set_next_list(next);
+}
+if (_smr_to_delete_list == current) {
+_smr_to_delete_list = next;
+}
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_free_list: threads=" INTPTR_FORMAT " is freed.", os::current_thread_id(), p2i(current));
+if (current == threads) threads_is_freed = true;
+delete current;
+if (EnableThreadSMRStatistics) {
+_smr_java_thread_list_free_cnt++;
+_smr_to_delete_list_cnt--;
+}
+} else {
+prev = current;
+}
+current = next;
+}
+if (!threads_is_freed) {
+// Only report "is not freed" on the original call to
+// smr_free_list() for this ThreadsList.
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::smr_free_list: threads=" INTPTR_FORMAT " is not freed.", os::current_thread_id(), p2i(threads));
+}
+delete scan_table;
+}
+// Remove a JavaThread from a ThreadsList. The returned ThreadsList is a
+// new copy of the specified ThreadsList with the specified JavaThread
+// removed.
+ThreadsList *ThreadsList::remove_thread(ThreadsList* list, JavaThread* java_thread) {
+assert(list->_length > 0, "sanity");
+uint i = 0;
+DO_JAVA_THREADS(list, current) {
+if (current == java_thread) {
+break;
+}
+i++;
+}
+assert(i < list->_length, "did not find JavaThread on the list");
+const uint index = i;
+const uint new_length = list->_length - 1;
+const uint head_length = index;
+const uint tail_length = (new_length >= index) ? (new_length - index) : 0;
+ThreadsList *const new_list = new ThreadsList(new_length);
+if (head_length > 0) {
+Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length);
+}
+if (tail_length > 0) {
+Copy::disjoint_words((HeapWord*)list->_threads + index + 1, (HeapWord*)new_list->_threads + index, tail_length);
+}
+return new_list;
+}
+// Add a JavaThread to a ThreadsList. The returned ThreadsList is a
+// new copy of the specified ThreadsList with the specified JavaThread
+// appended to the end.
+ThreadsList *ThreadsList::add_thread(ThreadsList *list, JavaThread *java_thread) {
+const uint index = list->_length;
+const uint new_length = index + 1;
+const uint head_length = index;
+ThreadsList *const new_list = new ThreadsList(new_length);
+if (head_length > 0) {
+Copy::disjoint_words((HeapWord*)list->_threads, (HeapWord*)new_list->_threads, head_length);
+}
+*(JavaThread**)(new_list->_threads + index) = java_thread;
+return new_list;
+}
+int ThreadsList::find_index_of_JavaThread(JavaThread *target) {
+if (target == NULL) {
+return -1;
+}
+for (uint i = 0; i < length(); i++) {
+if (target == thread_at(i)) {
+return (int)i;
+}
+}
+return -1;
+}
+JavaThread* ThreadsList::find_JavaThread_from_java_tid(jlong java_tid) const {
+DO_JAVA_THREADS(this, thread) {
+oop tobj = thread->threadObj();
+// Ignore the thread if it hasn't run yet, has exited
+// or is starting to exit.
+if (tobj != NULL && !thread->is_exiting() &&
+java_tid == java_lang_Thread::thread_id(tobj)) {
+// found a match
+return thread;
+}
+}
+return NULL;
+}
+bool ThreadsList::includes(const JavaThread * const p) const {
+if (p == NULL) {
+return false;
+}
+DO_JAVA_THREADS(this, q) {
+if (q == p) {
+return true;
+}
+}
+return false;
+}
 void Threads::add(JavaThread* p, bool force_daemon) {
 // The threads lock must be owned at this point
 assert_locked_or_safepoint(Threads_lock);
 // See the comment for this method in thread.hpp for its purpose and
 // why it is called here.
 p->initialize_queues();
 p->set_next(_thread_list);
 _thread_list = p;
+// Once a JavaThread is added to the Threads list, smr_delete() has
+// to be used to delete it. Otherwise we can just delete it directly.
+p->set_on_thread_list();
 _number_of_threads++;
 oop threadObj = p->threadObj();
 bool daemon = true;
 // Bootstrapping problem: threadObj can be null for initial
 // JavaThread (or for threads attached via JNI)
 daemon = false;
 }
 ThreadService::add_thread(p, daemon);
+// Maintain fast thread list
+ThreadsList *new_list = ThreadsList::add_thread(get_smr_java_thread_list(), p);
+if (EnableThreadSMRStatistics) {
+_smr_java_thread_list_alloc_cnt++;
+if (new_list->length() > _smr_java_thread_list_max) {
+_smr_java_thread_list_max = new_list->length();
+}
+}
+// Initial _smr_java_thread_list will not generate a "Threads::add" mesg.
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::add: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list));
+ThreadsList *old_list = xchg_smr_java_thread_list(new_list);
+smr_free_list(old_list);
 // Possible GC point.
 Events::log(p, "Thread added: " INTPTR_FORMAT, p2i(p));
 }
 void Threads::remove(JavaThread* p) {
 // Extra scope needed for Thread_lock, so we can check
 // that we do not remove thread without safepoint code notice
 { MutexLocker ml(Threads_lock);
-assert(includes(p), "p must be present");
+assert(get_smr_java_thread_list()->includes(p), "p must be present");
+// Maintain fast thread list
+ThreadsList *new_list = ThreadsList::remove_thread(get_smr_java_thread_list(), p);
+if (EnableThreadSMRStatistics) {
+_smr_java_thread_list_alloc_cnt++;
+// This list is smaller so no need to check for a "longest" update.
+}
+// Final _smr_java_thread_list will not generate a "Threads::remove" mesg.
+log_debug(thread, smr)("tid=" UINTX_FORMAT ": Threads::remove: new ThreadsList=" INTPTR_FORMAT, os::current_thread_id(), p2i(new_list));
+ThreadsList *old_list = xchg_smr_java_thread_list(new_list);
+smr_free_list(old_list);
 JavaThread* current = _thread_list;
 JavaThread* prev    = NULL;
 while (current != p) {
 if (prev) {
 prev->set_next(current->next());
 } else {
 _thread_list = p->next();
 }
 _number_of_threads--;
 oop threadObj = p->threadObj();
 bool daemon = true;
 if (threadObj == NULL || !java_lang_Thread::is_daemon(threadObj)) {
 _number_of_non_daemon_threads--;
 p->set_terminated_value();
 } // unlock Threads_lock
 // Since Events::log uses a lock, we grab it outside the Threads_lock
 Events::log(p, "Thread exited: " INTPTR_FORMAT, p2i(p));
-}
-// Threads_lock must be held when this is called (or must be called during a safepoint)
-bool Threads::includes(JavaThread* p) {
-assert(Threads_lock->is_locked(), "sanity check");
-ALL_JAVA_THREADS(q) {
-if (q == p) {
-return true;
-}
-}
-return false;
 }
 // Operations on the Threads list for GC.  These are not explicitly locked,
 // but the garbage collector must provide a safe context for them to run.
 // In particular, these things should never be called when the Threads_lock
 }
 }
 // Get count Java threads that are waiting to enter the specified monitor.
-GrowableArray<JavaThread*>* Threads::get_pending_threads(int count,
+GrowableArray<JavaThread*>* Threads::get_pending_threads(ThreadsList * t_list,
-address monitor,
+int count,
-bool doLock) {
+address monitor) {
-assert(doLock || SafepointSynchronize::is_at_safepoint(),
-"must grab Threads_lock or be at safepoint");
 GrowableArray<JavaThread*>* result = new GrowableArray<JavaThread*>(count);
 int i = 0;
-{
+DO_JAVA_THREADS(t_list, p) {
-MutexLockerEx ml(doLock ? Threads_lock : NULL);
+if (!p->can_call_java()) continue;
-ALL_JAVA_THREADS(p) {
-if (!p->can_call_java()) continue;
+address pending = (address)p->current_pending_monitor();
+if (pending == monitor) {             // found a match
-address pending = (address)p->current_pending_monitor();
+if (i < count) result->append(p);   // save the first count matches
-if (pending == monitor) {             // found a match
+i++;
-if (i < count) result->append(p);   // save the first count matches
+}
-i++;
+}
-}
-}
-}
 return result;
 }
-JavaThread *Threads::owning_thread_from_monitor_owner(address owner,
+JavaThread *Threads::owning_thread_from_monitor_owner(ThreadsList * t_list,
-bool doLock) {
+address owner) {
-assert(doLock ||
-Threads_lock->owned_by_self() ||
-SafepointSynchronize::is_at_safepoint(),
-"must grab Threads_lock or be at safepoint");
 // NULL owner means not locked so we can skip the search
 if (owner == NULL) return NULL;
-{
+DO_JAVA_THREADS(t_list, p) {
-MutexLockerEx ml(doLock ? Threads_lock : NULL);
+// first, see if owner is the address of a Java thread
-ALL_JAVA_THREADS(p) {
+if (owner == (address)p) return p;
-// first, see if owner is the address of a Java thread
+}
-if (owner == (address)p) return p;
-}
-}
 // Cannot assert on lack of success here since this function may be
 // used by code that is trying to report useful problem information
 // like deadlock detection.
 if (UseHeavyMonitors) return NULL;
 // If we didn't find a matching Java thread and we didn't force use of
 // heavyweight monitors, then the owner is the stack address of the
 // Lock Word in the owning Java thread's stack.
 //
 JavaThread* the_owner = NULL;
-{
+DO_JAVA_THREADS(t_list, q) {
-MutexLockerEx ml(doLock ? Threads_lock : NULL);
+if (q->is_lock_owned(owner)) {
-ALL_JAVA_THREADS(q) {
+the_owner = q;
-if (q->is_lock_owned(owner)) {
+break;
-the_owner = q;
+}
-break;
+}
-}
-}
-}
 // cannot assert on lack of success here; see above comment
 return the_owner;
 }
 // Threads::print_on() is called at safepoint by VM_PrintThreads operation.
 ConcurrentLocksDump concurrent_locks;
 if (print_concurrent_locks) {
 concurrent_locks.dump_at_safepoint();
 }
 #endif // INCLUDE_SERVICES
+print_smr_info_on(st);
+st->cr();
 ALL_JAVA_THREADS(p) {
 ResourceMark rm;
 p->print_on(st);
 if (print_stacks) {
 WatcherThread* wt = WatcherThread::watcher_thread();
 if (wt != NULL) {
 wt->print_on(st);
 st->cr();
 }
 st->flush();
+}
+// Log Threads class SMR info.
+void Threads::log_smr_statistics() {
+LogTarget(Info, thread, smr) log;
+if (log.is_enabled()) {
+LogStream out(log);
+print_smr_info_on(&out);
+}
+}
+// Print Threads class SMR info.
+void Threads::print_smr_info_on(outputStream* st) {
+// Only grab the Threads_lock if we don't already own it
+// and if we are not reporting an error.
+MutexLockerEx ml((Threads_lock->owned_by_self() || VMError::is_error_reported()) ? NULL : Threads_lock);
+st->print_cr("Threads class SMR info:");
+st->print_cr("_smr_java_thread_list=" INTPTR_FORMAT ", length=%u, "
+"elements={", p2i(_smr_java_thread_list),
+_smr_java_thread_list->length());
+print_smr_info_elements_on(st, _smr_java_thread_list);
+st->print_cr("}");
+if (_smr_to_delete_list != NULL) {
+st->print_cr("_smr_to_delete_list=" INTPTR_FORMAT ", length=%u, "
+"elements={", p2i(_smr_to_delete_list),
+_smr_to_delete_list->length());
+print_smr_info_elements_on(st, _smr_to_delete_list);
+st->print_cr("}");
+for (ThreadsList *t_list = _smr_to_delete_list->next_list();
+t_list != NULL; t_list = t_list->next_list()) {
+st->print("next-> " INTPTR_FORMAT ", length=%u, "
+"elements={", p2i(t_list), t_list->length());
+print_smr_info_elements_on(st, t_list);
+st->print_cr("}");
+}
+}
+if (!EnableThreadSMRStatistics) {
+return;
+}
+st->print_cr("_smr_java_thread_list_alloc_cnt=" UINT64_FORMAT ","
+"_smr_java_thread_list_free_cnt=" UINT64_FORMAT ","
+"_smr_java_thread_list_max=%u, "
+"_smr_nested_thread_list_max=%u",
+_smr_java_thread_list_alloc_cnt,
+_smr_java_thread_list_free_cnt,
+_smr_java_thread_list_max,
+_smr_nested_thread_list_max);
+if (_smr_tlh_cnt > 0) {
+st->print_cr("_smr_tlh_cnt=%u"
+", _smr_tlh_times=%u"
+", avg_smr_tlh_time=%0.2f"
+", _smr_tlh_time_max=%u",
+_smr_tlh_cnt, _smr_tlh_times,
+((double) _smr_tlh_times / _smr_tlh_cnt),
+_smr_tlh_time_max);
+}
+if (_smr_deleted_thread_cnt > 0) {
+st->print_cr("_smr_deleted_thread_cnt=%u"
+", _smr_deleted_thread_times=%u"
+", avg_smr_deleted_thread_time=%0.2f"
+", _smr_deleted_thread_time_max=%u",
+_smr_deleted_thread_cnt, _smr_deleted_thread_times,
+((double) _smr_deleted_thread_times / _smr_deleted_thread_cnt),
+_smr_deleted_thread_time_max);
+}
+st->print_cr("_smr_delete_lock_wait_cnt=%u, _smr_delete_lock_wait_max=%u",
+_smr_delete_lock_wait_cnt, _smr_delete_lock_wait_max);
+st->print_cr("_smr_to_delete_list_cnt=%u, _smr_to_delete_list_max=%u",
+_smr_to_delete_list_cnt, _smr_to_delete_list_max);
+}
+// Print ThreadsList elements (4 per line).
+void Threads::print_smr_info_elements_on(outputStream* st,
+ThreadsList* t_list) {
+uint cnt = 0;
+JavaThreadIterator jti(t_list);
+for (JavaThread *jt = jti.first(); jt != NULL; jt = jti.next()) {
+st->print(INTPTR_FORMAT, p2i(jt));
+if (cnt < t_list->length() - 1) {
+// Separate with comma or comma-space except for the last one.
+if (((cnt + 1) % 4) == 0) {
+// Four INTPTR_FORMAT fit on an 80 column line so end the
+// current line with just a comma.
+st->print_cr(",");
+} else {
+// Not the last one on the current line so use comma-space:
+st->print(", ");
+}
+} else {
+// Last one so just end the current line.
+st->cr();
+}
+cnt++;
+}
 }
 void Threads::print_on_error(Thread* this_thread, outputStream* st, Thread* current, char* buf,
 int buflen, bool* found_current) {
 if (this_thread != NULL) {
 // that VM is not at safepoint and/or current thread is inside signal handler.
 // Don't print stack trace, as the stack may not be walkable. Don't allocate
 // memory (even in resource area), it might deadlock the error handler.
 void Threads::print_on_error(outputStream* st, Thread* current, char* buf,
 int buflen) {
+print_smr_info_on(st);
+st->cr();
 bool found_current = false;
 st->print_cr("Java Threads: ( => current thread )");
 ALL_JAVA_THREADS(thread) {
 print_on_error(thread, st, current, buf, buflen, &found_current);
 }
 st->print("=>" PTR_FORMAT " (exited) ", p2i(current));
 current->print_on_error(st, buf, buflen);
 st->cr();
 }
 st->cr();
 st->print_cr("Threads with active compile tasks:");
 print_threads_compiling(st, buf, buflen);
 }
 void Threads::print_threads_compiling(outputStream* st, char* buf, int buflen) {

changeset 48105	8d15b1369c7a
parent 48005	9fd89aabb6cd
child 48173	cb63f08dad03