--- a/src/hotspot/share/prims/jvmtiRawMonitor.cpp Thu Oct 17 20:27:44 2019 +0100
+++ b/src/hotspot/share/prims/jvmtiRawMonitor.cpp Thu Oct 17 20:53:35 2019 +0100
@@ -30,21 +30,23 @@
#include "runtime/orderAccess.hpp"
#include "runtime/thread.inline.hpp"
-GrowableArray<JvmtiRawMonitor*> *JvmtiPendingMonitors::_monitors = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<JvmtiRawMonitor*>(1,true);
+JvmtiRawMonitor::QNode::QNode(Thread* thread) : _next(NULL), _prev(NULL),
+ _event(thread->_ParkEvent),
+ _notified(0), _t_state(TS_RUN) {
+}
+
+GrowableArray<JvmtiRawMonitor*>* JvmtiPendingMonitors::_monitors =
+ new (ResourceObj::C_HEAP, mtInternal) GrowableArray<JvmtiRawMonitor*>(1, true);
void JvmtiPendingMonitors::transition_raw_monitors() {
assert((Threads::number_of_threads()==1),
- "Java thread has not created yet or more than one java thread \
-is running. Raw monitor transition will not work");
- JavaThread *current_java_thread = JavaThread::current();
+ "Java thread has not been created yet or more than one java thread "
+ "is running. Raw monitor transition will not work");
+ JavaThread* current_java_thread = JavaThread::current();
assert(current_java_thread->thread_state() == _thread_in_vm, "Must be in vm");
- {
- ThreadBlockInVM __tbivm(current_java_thread);
- for(int i=0; i< count(); i++) {
- JvmtiRawMonitor *rmonitor = monitors()->at(i);
- int r = rmonitor->raw_enter(current_java_thread);
- assert(r == ObjectMonitor::OM_OK, "raw_enter should have worked");
- }
+ for (int i = 0; i < count(); i++) {
+ JvmtiRawMonitor* rmonitor = monitors()->at(i);
+ rmonitor->raw_enter(current_java_thread);
}
// pending monitors are converted to real monitor so delete them all.
dispose();
@@ -54,13 +56,16 @@
// class JvmtiRawMonitor
//
-JvmtiRawMonitor::JvmtiRawMonitor(const char *name) {
+JvmtiRawMonitor::JvmtiRawMonitor(const char* name) : _owner(NULL),
+ _recursions(0),
+ _entry_list(NULL),
+ _wait_set(NULL),
+ _waiters(0),
+ _magic(JVMTI_RM_MAGIC),
+ _name(NULL) {
#ifdef ASSERT
_name = strcpy(NEW_C_HEAP_ARRAY(char, strlen(name) + 1, mtInternal), name);
-#else
- _name = NULL;
#endif
- _magic = JVMTI_RM_MAGIC;
}
JvmtiRawMonitor::~JvmtiRawMonitor() {
@@ -100,181 +105,179 @@
}
// -------------------------------------------------------------------------
-// The raw monitor subsystem is entirely distinct from normal
-// java-synchronization or jni-synchronization. raw monitors are not
+// The JVMTI raw monitor subsystem is entirely distinct from normal
+// java-synchronization or jni-synchronization. JVMTI 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.
+// the raw-monitor implementation on the existing Java ObjectMonitor mechanism.
+// Now we just use a simplified form of that ObjectMonitor code.
//
// 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
+// is fairly rare, this is not of concern. The RawMonitor_lock can not
// be held indefinitely. The critical sections must be short and bounded.
//
// -------------------------------------------------------------------------
-int JvmtiRawMonitor::SimpleEnter (Thread * Self) {
+void JvmtiRawMonitor::simple_enter(Thread* self) {
for (;;) {
- if (Atomic::replace_if_null(Self, &_owner)) {
- return OS_OK ;
+ if (Atomic::replace_if_null(self, &_owner)) {
+ return;
}
- ObjectWaiter Node (Self) ;
- Self->_ParkEvent->reset() ; // strictly optional
- Node.TState = ObjectWaiter::TS_ENTER ;
+ QNode node(self);
+ self->_ParkEvent->reset(); // strictly optional
+ node._t_state = QNode::TS_ENTER;
- RawMonitor_lock->lock_without_safepoint_check() ;
- Node._next = _EntryList ;
- _EntryList = &Node ;
- OrderAccess::fence() ;
- if (_owner == NULL && Atomic::replace_if_null(Self, &_owner)) {
- _EntryList = Node._next ;
- RawMonitor_lock->unlock() ;
- return OS_OK ;
+ RawMonitor_lock->lock_without_safepoint_check();
+ node._next = _entry_list;
+ _entry_list = &node;
+ OrderAccess::fence();
+ if (_owner == NULL && Atomic::replace_if_null(self, &_owner)) {
+ _entry_list = node._next;
+ RawMonitor_lock->unlock();
+ return;
}
- RawMonitor_lock->unlock() ;
- while (Node.TState == ObjectWaiter::TS_ENTER) {
- Self->_ParkEvent->park() ;
+ RawMonitor_lock->unlock();
+ while (node._t_state == QNode::TS_ENTER) {
+ self->_ParkEvent->park();
}
}
}
-int JvmtiRawMonitor::SimpleExit (Thread * Self) {
- guarantee (_owner == Self, "invariant") ;
- OrderAccess::release_store(&_owner, (void*)NULL) ;
- OrderAccess::fence() ;
- if (_EntryList == NULL) return OS_OK ;
- ObjectWaiter * w ;
+void JvmtiRawMonitor::simple_exit(Thread* self) {
+ guarantee(_owner == self, "invariant");
+ OrderAccess::release_store(&_owner, (Thread*)NULL);
+ OrderAccess::fence();
+ if (_entry_list == NULL) {
+ return;
+ }
- RawMonitor_lock->lock_without_safepoint_check() ;
- w = _EntryList ;
+ RawMonitor_lock->lock_without_safepoint_check();
+ QNode* w = _entry_list;
if (w != NULL) {
- _EntryList = w->_next ;
+ _entry_list = w->_next;
}
- RawMonitor_lock->unlock() ;
+ RawMonitor_lock->unlock();
if (w != NULL) {
- guarantee (w ->TState == ObjectWaiter::TS_ENTER, "invariant") ;
- // Once we set TState to TS_RUN the waiting thread can complete
- // SimpleEnter and 'w' is pointing into random stack space. So we have
- // to ensure we extract the ParkEvent (which is in type-stable memory)
- // before we set the state, and then don't access 'w'.
- ParkEvent * ev = w->_event ;
- OrderAccess::loadstore();
- w->TState = ObjectWaiter::TS_RUN ;
- OrderAccess::fence() ;
- ev->unpark() ;
+ guarantee(w ->_t_state == QNode::TS_ENTER, "invariant");
+ // Once we set _t_state to TS_RUN the waiting thread can complete
+ // simple_enter and 'w' is pointing into random stack space. So we have
+ // to ensure we extract the ParkEvent (which is in type-stable memory)
+ // before we set the state, and then don't access 'w'.
+ ParkEvent* ev = w->_event;
+ OrderAccess::loadstore();
+ w->_t_state = QNode::TS_RUN;
+ OrderAccess::fence();
+ ev->unpark();
}
- return OS_OK ;
+ return;
}
-int JvmtiRawMonitor::SimpleWait (Thread * Self, jlong millis) {
- guarantee (_owner == Self , "invariant") ;
- guarantee (_recursions == 0, "invariant") ;
+int JvmtiRawMonitor::simple_wait(Thread* self, jlong millis) {
+ guarantee(_owner == self , "invariant");
+ guarantee(_recursions == 0, "invariant");
- ObjectWaiter Node (Self) ;
- Node._notified = 0 ;
- Node.TState = ObjectWaiter::TS_WAIT ;
+ QNode node(self);
+ node._notified = 0;
+ node._t_state = QNode::TS_WAIT;
- RawMonitor_lock->lock_without_safepoint_check() ;
- Node._next = _WaitSet ;
- _WaitSet = &Node ;
- RawMonitor_lock->unlock() ;
+ RawMonitor_lock->lock_without_safepoint_check();
+ node._next = _wait_set;
+ _wait_set = &node;
+ RawMonitor_lock->unlock();
- SimpleExit (Self) ;
- guarantee (_owner != Self, "invariant") ;
+ simple_exit(self);
+ guarantee(_owner != self, "invariant");
- int ret = OS_OK ;
+ int ret = OS_OK;
if (millis <= 0) {
- Self->_ParkEvent->park();
+ self->_ParkEvent->park();
} else {
- ret = Self->_ParkEvent->park(millis);
+ 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 TState is volatile and the lock-unlock operators are
+ // as _t_state 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) {
+ if (node._t_state == QNode::TS_WAIT) {
+ RawMonitor_lock->lock_without_safepoint_check();
+ if (node._t_state == QNode::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 ;
+ QNode* p;
+ QNode* q = NULL;
+ for (p = _wait_set; p != &node; p = p->_next) {
+ q = p;
}
- guarantee (p == &Node, "invariant") ;
+ guarantee(p == &node, "invariant");
if (q == NULL) {
- guarantee (p == _WaitSet, "invariant") ;
- _WaitSet = p->_next ;
+ guarantee (p == _wait_set, "invariant");
+ _wait_set = p->_next;
} else {
- guarantee (p == q->_next, "invariant") ;
- q->_next = p->_next ;
+ guarantee(p == q->_next, "invariant");
+ q->_next = p->_next;
}
- Node.TState = ObjectWaiter::TS_RUN ;
+ node._t_state = QNode::TS_RUN;
}
- RawMonitor_lock->unlock() ;
+ RawMonitor_lock->unlock();
}
- guarantee (Node.TState == ObjectWaiter::TS_RUN, "invariant") ;
- SimpleEnter (Self) ;
+ guarantee(node._t_state == QNode::TS_RUN, "invariant");
+ simple_enter(self);
- guarantee (_owner == Self, "invariant") ;
- guarantee (_recursions == 0, "invariant") ;
- return ret ;
+ guarantee(_owner == self, "invariant");
+ guarantee(_recursions == 0, "invariant");
+ return ret;
}
-int JvmtiRawMonitor::SimpleNotify (Thread * Self, bool All) {
- guarantee (_owner == Self, "invariant") ;
- if (_WaitSet == NULL) return OS_OK ;
+void JvmtiRawMonitor::simple_notify(Thread* self, bool all) {
+ guarantee(_owner == self, "invariant");
+ if (_wait_set == NULL) {
+ return;
+ }
// We have two options:
- // A. Transfer the threads from the WaitSet to the EntryList
- // B. Remove the thread from the WaitSet and unpark() it.
+ // A. Transfer the threads from the _wait_set to the _entry_list
+ // B. Remove the thread from the _wait_set 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() ;
+ 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 ;
+ QNode* w = _wait_set;
+ if (w == NULL) break;
+ _wait_set = w->_next;
+ if (ev != NULL) {
+ ev->unpark();
+ ev = NULL;
+ }
+ ev = w->_event;
+ OrderAccess::loadstore();
+ w->_t_state = QNode::TS_RUN;
+ OrderAccess::storeload();
+ if (!all) {
+ break;
+ }
}
- RawMonitor_lock->unlock() ;
- if (ev != NULL) ev->unpark();
- return OS_OK ;
+ RawMonitor_lock->unlock();
+ if (ev != NULL) {
+ ev->unpark();
+ }
+ return;
}
// Any JavaThread will enter here with state _thread_blocked
-int JvmtiRawMonitor::raw_enter(TRAPS) {
- void * Contended ;
-
+void JvmtiRawMonitor::raw_enter(Thread* self) {
+ void* contended;
+ JavaThread* jt = NULL;
// 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()) {
+ if (self->is_Java_thread()) {
+ jt = (JavaThread*)self;
jt->SR_lock()->lock_without_safepoint_check();
while (jt->is_external_suspend()) {
jt->SR_lock()->unlock();
@@ -282,143 +285,140 @@
jt->SR_lock()->lock_without_safepoint_check();
}
// guarded by SR_lock to avoid racing with new external suspend requests.
- Contended = Atomic::cmpxchg(THREAD, &_owner, (void*)NULL);
+ contended = Atomic::cmpxchg(jt, &_owner, (Thread*)NULL);
jt->SR_lock()->unlock();
} else {
- Contended = Atomic::cmpxchg(THREAD, &_owner, (void*)NULL);
+ contended = Atomic::cmpxchg(self, &_owner, (Thread*)NULL);
}
- if (Contended == THREAD) {
- _recursions ++ ;
- return OM_OK ;
+ if (contended == self) {
+ _recursions++;
+ return;
}
- if (Contended == NULL) {
- guarantee (_owner == THREAD, "invariant") ;
- guarantee (_recursions == 0, "invariant") ;
- return OM_OK ;
+ if (contended == NULL) {
+ guarantee(_owner == self, "invariant");
+ guarantee(_recursions == 0, "invariant");
+ return;
}
- THREAD->set_current_pending_monitor(this);
+ self->set_current_pending_raw_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 ;
+ if (!self->is_Java_thread()) {
+ simple_enter(self);
+ } else {
+ guarantee(jt->thread_state() == _thread_blocked, "invariant");
+ for (;;) {
+ jt->set_suspend_equivalent();
+ // cleared by handle_special_suspend_equivalent_condition() or
+ // java_suspend_self()
+ simple_enter(jt);
- // 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 JvmtiRawMonitor.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) ;
+ // were we externally suspended while we were waiting?
+ if (!jt->handle_special_suspend_equivalent_condition()) {
+ break;
+ }
- jt->java_suspend_self();
- }
+ // This thread was externally suspended
+ // 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
+ simple_exit(jt);
- assert(_owner == THREAD, "Fatal error with monitor owner!");
- assert(_recursions == 0, "Fatal error with monitor recursions!");
+ jt->java_suspend_self();
+ }
}
- THREAD->set_current_pending_monitor(NULL);
- guarantee (_recursions == 0, "invariant") ;
- return OM_OK;
+ self->set_current_pending_raw_monitor(NULL);
+
+ guarantee(_owner == self, "invariant");
+ guarantee(_recursions == 0, "invariant");
}
-// Used mainly for JVMTI raw monitor implementation
-// Also used for JvmtiRawMonitor::wait().
-int JvmtiRawMonitor::raw_exit(TRAPS) {
- if (THREAD != _owner) {
- return OM_ILLEGAL_MONITOR_STATE;
+int JvmtiRawMonitor::raw_exit(Thread* self) {
+ if (self != _owner) {
+ return M_ILLEGAL_MONITOR_STATE;
}
if (_recursions > 0) {
- --_recursions ;
- return OM_OK ;
+ _recursions--;
+ } else {
+ simple_exit(self);
}
- void * List = _EntryList ;
- SimpleExit (THREAD) ;
-
- return OM_OK;
+ return M_OK;
}
-// Used for JVMTI raw monitor implementation.
// All JavaThreads will enter here with state _thread_blocked
-int JvmtiRawMonitor::raw_wait(jlong millis, bool interruptible, TRAPS) {
- if (THREAD != _owner) {
- return OM_ILLEGAL_MONITOR_STATE;
+int JvmtiRawMonitor::raw_wait(jlong millis, bool interruptible, Thread* self) {
+ if (self != _owner) {
+ return M_ILLEGAL_MONITOR_STATE;
}
- // To avoid spurious wakeups we reset the parkevent -- This is strictly optional.
+ // 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() ;
+ self->_ParkEvent->reset();
+ OrderAccess::fence();
+ JavaThread* jt = NULL;
// check interrupt event
- if (interruptible && Thread::is_interrupted(THREAD, true)) {
- return OM_INTERRUPTED;
+ if (interruptible) {
+ assert(self->is_Java_thread(), "Only JavaThreads can be interruptible");
+ jt = (JavaThread*)self;
+ if (jt->is_interrupted(true)) {
+ return M_INTERRUPTED;
+ }
+ } else {
+ assert(!self->is_Java_thread(), "JavaThreads must be interuptible");
}
- 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();
+ intptr_t save = _recursions;
+ _recursions = 0;
+ _waiters++;
+ if (self->is_Java_thread()) {
+ guarantee(jt->thread_state() == _thread_blocked, "invariant");
+ jt->set_suspend_equivalent();
}
- int rv = SimpleWait (THREAD, millis) ;
- _recursions = save ;
- _waiters -- ;
+ int rv = simple_wait(self, 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(self == _owner, "invariant");
+ if (self->is_Java_thread()) {
+ for (;;) {
+ if (!jt->handle_special_suspend_equivalent_condition()) {
+ break;
+ }
+ simple_exit(jt);
+ jt->java_suspend_self();
+ simple_enter(jt);
+ jt->set_suspend_equivalent();
+ }
+ guarantee(jt == _owner, "invariant");
}
- guarantee (THREAD == _owner, "invariant") ;
- if (interruptible && Thread::is_interrupted(THREAD, true)) {
- return OM_INTERRUPTED;
+ if (interruptible && jt->is_interrupted(true)) {
+ return M_INTERRUPTED;
}
- return OM_OK ;
+
+ return M_OK;
}
-int JvmtiRawMonitor::raw_notify(TRAPS) {
- if (THREAD != _owner) {
- return OM_ILLEGAL_MONITOR_STATE;
+int JvmtiRawMonitor::raw_notify(Thread* self) {
+ if (self != _owner) {
+ return M_ILLEGAL_MONITOR_STATE;
}
- SimpleNotify (THREAD, false) ;
- return OM_OK;
+ simple_notify(self, false);
+ return M_OK;
}
-int JvmtiRawMonitor::raw_notifyAll(TRAPS) {
- if (THREAD != _owner) {
- return OM_ILLEGAL_MONITOR_STATE;
+int JvmtiRawMonitor::raw_notifyAll(Thread* self) {
+ if (self != _owner) {
+ return M_ILLEGAL_MONITOR_STATE;
}
- SimpleNotify (THREAD, true) ;
- return OM_OK;
+ simple_notify(self, true);
+ return M_OK;
}