110 // and move the resulting raw monitor implementation over to the JVMTI directories.
111 // Ideally, the raw monitor implementation would be built on top of
112 // park-unpark and nothing else.
113 //
114 // raw monitors are used mainly by JVMTI
115 // The raw monitor implementation borrows the ObjectMonitor structure,
116 // but the operators are degenerate and extremely simple.
117 //
118 // Mixed use of a single objectMonitor instance -- as both a raw monitor
119 // and a normal java monitor -- is not permissible.
120 //
121 // Note that we use the single RawMonitor_lock to protect queue operations for
122 // _all_ raw monitors. This is a scalability impediment, but since raw monitor usage
123 // is deprecated and rare, this is not of concern. The RawMonitor_lock can not
124 // be held indefinitely. The critical sections must be short and bounded.
125 //
126 // -------------------------------------------------------------------------
127
128 int JvmtiRawMonitor::SimpleEnter (Thread * Self) {
129 for (;;) {
130 if (Atomic::cmpxchg((void*)Self, &_owner, (void*)NULL) == NULL) {
131 return OS_OK ;
132 }
133
134 ObjectWaiter Node (Self) ;
135 Self->_ParkEvent->reset() ; // strictly optional
136 Node.TState = ObjectWaiter::TS_ENTER ;
137
138 RawMonitor_lock->lock_without_safepoint_check() ;
139 Node._next = _EntryList ;
140 _EntryList = &Node ;
141 OrderAccess::fence() ;
142 if (_owner == NULL && Atomic::cmpxchg((void*)Self, &_owner, (void*)NULL) == NULL) {
143 _EntryList = Node._next ;
144 RawMonitor_lock->unlock() ;
145 return OS_OK ;
146 }
147 RawMonitor_lock->unlock() ;
148 while (Node.TState == ObjectWaiter::TS_ENTER) {
149 Self->_ParkEvent->park() ;
150 }
151 }
152 }
153
154 int JvmtiRawMonitor::SimpleExit (Thread * Self) {
155 guarantee (_owner == Self, "invariant") ;
156 OrderAccess::release_store(&_owner, (void*)NULL) ;
157 OrderAccess::fence() ;
158 if (_EntryList == NULL) return OS_OK ;
159 ObjectWaiter * w ;
160
161 RawMonitor_lock->lock_without_safepoint_check() ;
162 w = _EntryList ;
260 if (ev != NULL) ev->unpark();
261 return OS_OK ;
262 }
263
264 // Any JavaThread will enter here with state _thread_blocked
265 int JvmtiRawMonitor::raw_enter(TRAPS) {
266 TEVENT (raw_enter) ;
267 void * Contended ;
268
269 // don't enter raw monitor if thread is being externally suspended, it will
270 // surprise the suspender if a "suspended" thread can still enter monitor
271 JavaThread * jt = (JavaThread *)THREAD;
272 if (THREAD->is_Java_thread()) {
273 jt->SR_lock()->lock_without_safepoint_check();
274 while (jt->is_external_suspend()) {
275 jt->SR_lock()->unlock();
276 jt->java_suspend_self();
277 jt->SR_lock()->lock_without_safepoint_check();
278 }
279 // guarded by SR_lock to avoid racing with new external suspend requests.
280 Contended = Atomic::cmpxchg((void*)THREAD, &_owner, (void*)NULL);
281 jt->SR_lock()->unlock();
282 } else {
283 Contended = Atomic::cmpxchg((void*)THREAD, &_owner, (void*)NULL);
284 }
285
286 if (Contended == THREAD) {
287 _recursions ++ ;
288 return OM_OK ;
289 }
290
291 if (Contended == NULL) {
292 guarantee (_owner == THREAD, "invariant") ;
293 guarantee (_recursions == 0, "invariant") ;
294 return OM_OK ;
295 }
296
297 THREAD->set_current_pending_monitor(this);
298
299 if (!THREAD->is_Java_thread()) {
300 // No other non-Java threads besides VM thread would acquire
301 // a raw monitor.
302 assert(THREAD->is_VM_thread(), "must be VM thread");
303 SimpleEnter (THREAD) ;
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110 // and move the resulting raw monitor implementation over to the JVMTI directories.
111 // Ideally, the raw monitor implementation would be built on top of
112 // park-unpark and nothing else.
113 //
114 // raw monitors are used mainly by JVMTI
115 // The raw monitor implementation borrows the ObjectMonitor structure,
116 // but the operators are degenerate and extremely simple.
117 //
118 // Mixed use of a single objectMonitor instance -- as both a raw monitor
119 // and a normal java monitor -- is not permissible.
120 //
121 // Note that we use the single RawMonitor_lock to protect queue operations for
122 // _all_ raw monitors. This is a scalability impediment, but since raw monitor usage
123 // is deprecated and rare, this is not of concern. The RawMonitor_lock can not
124 // be held indefinitely. The critical sections must be short and bounded.
125 //
126 // -------------------------------------------------------------------------
127
128 int JvmtiRawMonitor::SimpleEnter (Thread * Self) {
129 for (;;) {
130 if (Atomic::cmpxchg(Self, &_owner, (void*)NULL) == NULL) {
131 return OS_OK ;
132 }
133
134 ObjectWaiter Node (Self) ;
135 Self->_ParkEvent->reset() ; // strictly optional
136 Node.TState = ObjectWaiter::TS_ENTER ;
137
138 RawMonitor_lock->lock_without_safepoint_check() ;
139 Node._next = _EntryList ;
140 _EntryList = &Node ;
141 OrderAccess::fence() ;
142 if (_owner == NULL && Atomic::cmpxchg(Self, &_owner, (void*)NULL) == NULL) {
143 _EntryList = Node._next ;
144 RawMonitor_lock->unlock() ;
145 return OS_OK ;
146 }
147 RawMonitor_lock->unlock() ;
148 while (Node.TState == ObjectWaiter::TS_ENTER) {
149 Self->_ParkEvent->park() ;
150 }
151 }
152 }
153
154 int JvmtiRawMonitor::SimpleExit (Thread * Self) {
155 guarantee (_owner == Self, "invariant") ;
156 OrderAccess::release_store(&_owner, (void*)NULL) ;
157 OrderAccess::fence() ;
158 if (_EntryList == NULL) return OS_OK ;
159 ObjectWaiter * w ;
160
161 RawMonitor_lock->lock_without_safepoint_check() ;
162 w = _EntryList ;
260 if (ev != NULL) ev->unpark();
261 return OS_OK ;
262 }
263
264 // Any JavaThread will enter here with state _thread_blocked
265 int JvmtiRawMonitor::raw_enter(TRAPS) {
266 TEVENT (raw_enter) ;
267 void * Contended ;
268
269 // don't enter raw monitor if thread is being externally suspended, it will
270 // surprise the suspender if a "suspended" thread can still enter monitor
271 JavaThread * jt = (JavaThread *)THREAD;
272 if (THREAD->is_Java_thread()) {
273 jt->SR_lock()->lock_without_safepoint_check();
274 while (jt->is_external_suspend()) {
275 jt->SR_lock()->unlock();
276 jt->java_suspend_self();
277 jt->SR_lock()->lock_without_safepoint_check();
278 }
279 // guarded by SR_lock to avoid racing with new external suspend requests.
280 Contended = Atomic::cmpxchg(THREAD, &_owner, (void*)NULL);
281 jt->SR_lock()->unlock();
282 } else {
283 Contended = Atomic::cmpxchg(THREAD, &_owner, (void*)NULL);
284 }
285
286 if (Contended == THREAD) {
287 _recursions ++ ;
288 return OM_OK ;
289 }
290
291 if (Contended == NULL) {
292 guarantee (_owner == THREAD, "invariant") ;
293 guarantee (_recursions == 0, "invariant") ;
294 return OM_OK ;
295 }
296
297 THREAD->set_current_pending_monitor(this);
298
299 if (!THREAD->is_Java_thread()) {
300 // No other non-Java threads besides VM thread would acquire
301 // a raw monitor.
302 assert(THREAD->is_VM_thread(), "must be VM thread");
303 SimpleEnter (THREAD) ;
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