Mercurial > hg > truffle
comparison src/share/vm/prims/jvmtiRawMonitor.cpp @ 1878:fa83ab460c54
6988353: refactor contended sync subsystem
Summary: reduce complexity by factoring synchronizer.cpp
Reviewed-by: dholmes, never, coleenp
author | acorn |
---|---|
date | Fri, 22 Oct 2010 15:59:34 -0400 |
parents | |
children | f95d63e2154a |
comparison
equal
deleted
inserted
replaced
1874:75ab0162aa84 | 1878:fa83ab460c54 |
---|---|
1 /* | |
2 * Copyright (c) 2003, 2007, Oracle and/or its affiliates. All rights reserved. | |
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
4 * | |
5 * This code is free software; you can redistribute it and/or modify it | |
6 * under the terms of the GNU General Public License version 2 only, as | |
7 * published by the Free Software Foundation. | |
8 * | |
9 * This code is distributed in the hope that it will be useful, but WITHOUT | |
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
12 * version 2 for more details (a copy is included in the LICENSE file that | |
13 * accompanied this code). | |
14 * | |
15 * You should have received a copy of the GNU General Public License version | |
16 * 2 along with this work; if not, write to the Free Software Foundation, | |
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
18 * | |
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
20 * or visit www.oracle.com if you need additional information or have any | |
21 * questions. | |
22 * | |
23 */ | |
24 | |
25 # include "incls/_precompiled.incl" | |
26 # include "incls/_jvmtiRawMonitor.cpp.incl" | |
27 | |
28 GrowableArray<JvmtiRawMonitor*> *JvmtiPendingMonitors::_monitors = new (ResourceObj::C_HEAP) GrowableArray<JvmtiRawMonitor*>(1,true); | |
29 | |
30 void JvmtiPendingMonitors::transition_raw_monitors() { | |
31 assert((Threads::number_of_threads()==1), | |
32 "Java thread has not created yet or more than one java thread \ | |
33 is running. Raw monitor transition will not work"); | |
34 JavaThread *current_java_thread = JavaThread::current(); | |
35 assert(current_java_thread->thread_state() == _thread_in_vm, "Must be in vm"); | |
36 { | |
37 ThreadBlockInVM __tbivm(current_java_thread); | |
38 for(int i=0; i< count(); i++) { | |
39 JvmtiRawMonitor *rmonitor = monitors()->at(i); | |
40 int r = rmonitor->raw_enter(current_java_thread); | |
41 assert(r == ObjectMonitor::OM_OK, "raw_enter should have worked"); | |
42 } | |
43 } | |
44 // pending monitors are converted to real monitor so delete them all. | |
45 dispose(); | |
46 } | |
47 | |
48 // | |
49 // class JvmtiRawMonitor | |
50 // | |
51 | |
52 JvmtiRawMonitor::JvmtiRawMonitor(const char *name) { | |
53 #ifdef ASSERT | |
54 _name = strcpy(NEW_C_HEAP_ARRAY(char, strlen(name) + 1), name); | |
55 #else | |
56 _name = NULL; | |
57 #endif | |
58 _magic = JVMTI_RM_MAGIC; | |
59 } | |
60 | |
61 JvmtiRawMonitor::~JvmtiRawMonitor() { | |
62 #ifdef ASSERT | |
63 FreeHeap(_name); | |
64 #endif | |
65 _magic = 0; | |
66 } | |
67 | |
68 | |
69 bool | |
70 JvmtiRawMonitor::is_valid() { | |
71 int value = 0; | |
72 | |
73 // This object might not be a JvmtiRawMonitor so we can't assume | |
74 // the _magic field is properly aligned. Get the value in a safe | |
75 // way and then check against JVMTI_RM_MAGIC. | |
76 | |
77 switch (sizeof(_magic)) { | |
78 case 2: | |
79 value = Bytes::get_native_u2((address)&_magic); | |
80 break; | |
81 | |
82 case 4: | |
83 value = Bytes::get_native_u4((address)&_magic); | |
84 break; | |
85 | |
86 case 8: | |
87 value = Bytes::get_native_u8((address)&_magic); | |
88 break; | |
89 | |
90 default: | |
91 guarantee(false, "_magic field is an unexpected size"); | |
92 } | |
93 | |
94 return value == JVMTI_RM_MAGIC; | |
95 } | |
96 | |
97 // ------------------------------------------------------------------------- | |
98 // The raw monitor subsystem is entirely distinct from normal | |
99 // java-synchronization or jni-synchronization. raw monitors are not | |
100 // associated with objects. They can be implemented in any manner | |
101 // that makes sense. The original implementors decided to piggy-back | |
102 // the raw-monitor implementation on the existing Java objectMonitor mechanism. | |
103 // This flaw needs to fixed. We should reimplement raw monitors as sui-generis. | |
104 // Specifically, we should not implement raw monitors via java monitors. | |
105 // Time permitting, we should disentangle and deconvolve the two implementations | |
106 // and move the resulting raw monitor implementation over to the JVMTI directories. | |
107 // Ideally, the raw monitor implementation would be built on top of | |
108 // park-unpark and nothing else. | |
109 // | |
110 // raw monitors are used mainly by JVMTI | |
111 // The raw monitor implementation borrows the ObjectMonitor structure, | |
112 // but the operators are degenerate and extremely simple. | |
113 // | |
114 // Mixed use of a single objectMonitor instance -- as both a raw monitor | |
115 // and a normal java monitor -- is not permissible. | |
116 // | |
117 // Note that we use the single RawMonitor_lock to protect queue operations for | |
118 // _all_ raw monitors. This is a scalability impediment, but since raw monitor usage | |
119 // is deprecated and rare, this is not of concern. The RawMonitor_lock can not | |
120 // be held indefinitely. The critical sections must be short and bounded. | |
121 // | |
122 // ------------------------------------------------------------------------- | |
123 | |
124 int JvmtiRawMonitor::SimpleEnter (Thread * Self) { | |
125 for (;;) { | |
126 if (Atomic::cmpxchg_ptr (Self, &_owner, NULL) == NULL) { | |
127 return OS_OK ; | |
128 } | |
129 | |
130 ObjectWaiter Node (Self) ; | |
131 Self->_ParkEvent->reset() ; // strictly optional | |
132 Node.TState = ObjectWaiter::TS_ENTER ; | |
133 | |
134 RawMonitor_lock->lock_without_safepoint_check() ; | |
135 Node._next = _EntryList ; | |
136 _EntryList = &Node ; | |
137 OrderAccess::fence() ; | |
138 if (_owner == NULL && Atomic::cmpxchg_ptr (Self, &_owner, NULL) == NULL) { | |
139 _EntryList = Node._next ; | |
140 RawMonitor_lock->unlock() ; | |
141 return OS_OK ; | |
142 } | |
143 RawMonitor_lock->unlock() ; | |
144 while (Node.TState == ObjectWaiter::TS_ENTER) { | |
145 Self->_ParkEvent->park() ; | |
146 } | |
147 } | |
148 } | |
149 | |
150 int JvmtiRawMonitor::SimpleExit (Thread * Self) { | |
151 guarantee (_owner == Self, "invariant") ; | |
152 OrderAccess::release_store_ptr (&_owner, NULL) ; | |
153 OrderAccess::fence() ; | |
154 if (_EntryList == NULL) return OS_OK ; | |
155 ObjectWaiter * w ; | |
156 | |
157 RawMonitor_lock->lock_without_safepoint_check() ; | |
158 w = _EntryList ; | |
159 if (w != NULL) { | |
160 _EntryList = w->_next ; | |
161 } | |
162 RawMonitor_lock->unlock() ; | |
163 if (w != NULL) { | |
164 guarantee (w ->TState == ObjectWaiter::TS_ENTER, "invariant") ; | |
165 ParkEvent * ev = w->_event ; | |
166 w->TState = ObjectWaiter::TS_RUN ; | |
167 OrderAccess::fence() ; | |
168 ev->unpark() ; | |
169 } | |
170 return OS_OK ; | |
171 } | |
172 | |
173 int JvmtiRawMonitor::SimpleWait (Thread * Self, jlong millis) { | |
174 guarantee (_owner == Self , "invariant") ; | |
175 guarantee (_recursions == 0, "invariant") ; | |
176 | |
177 ObjectWaiter Node (Self) ; | |
178 Node._notified = 0 ; | |
179 Node.TState = ObjectWaiter::TS_WAIT ; | |
180 | |
181 RawMonitor_lock->lock_without_safepoint_check() ; | |
182 Node._next = _WaitSet ; | |
183 _WaitSet = &Node ; | |
184 RawMonitor_lock->unlock() ; | |
185 | |
186 SimpleExit (Self) ; | |
187 guarantee (_owner != Self, "invariant") ; | |
188 | |
189 int ret = OS_OK ; | |
190 if (millis <= 0) { | |
191 Self->_ParkEvent->park(); | |
192 } else { | |
193 ret = Self->_ParkEvent->park(millis); | |
194 } | |
195 | |
196 // If thread still resides on the waitset then unlink it. | |
197 // Double-checked locking -- the usage is safe in this context | |
198 // as we TState is volatile and the lock-unlock operators are | |
199 // serializing (barrier-equivalent). | |
200 | |
201 if (Node.TState == ObjectWaiter::TS_WAIT) { | |
202 RawMonitor_lock->lock_without_safepoint_check() ; | |
203 if (Node.TState == ObjectWaiter::TS_WAIT) { | |
204 // Simple O(n) unlink, but performance isn't critical here. | |
205 ObjectWaiter * p ; | |
206 ObjectWaiter * q = NULL ; | |
207 for (p = _WaitSet ; p != &Node; p = p->_next) { | |
208 q = p ; | |
209 } | |
210 guarantee (p == &Node, "invariant") ; | |
211 if (q == NULL) { | |
212 guarantee (p == _WaitSet, "invariant") ; | |
213 _WaitSet = p->_next ; | |
214 } else { | |
215 guarantee (p == q->_next, "invariant") ; | |
216 q->_next = p->_next ; | |
217 } | |
218 Node.TState = ObjectWaiter::TS_RUN ; | |
219 } | |
220 RawMonitor_lock->unlock() ; | |
221 } | |
222 | |
223 guarantee (Node.TState == ObjectWaiter::TS_RUN, "invariant") ; | |
224 SimpleEnter (Self) ; | |
225 | |
226 guarantee (_owner == Self, "invariant") ; | |
227 guarantee (_recursions == 0, "invariant") ; | |
228 return ret ; | |
229 } | |
230 | |
231 int JvmtiRawMonitor::SimpleNotify (Thread * Self, bool All) { | |
232 guarantee (_owner == Self, "invariant") ; | |
233 if (_WaitSet == NULL) return OS_OK ; | |
234 | |
235 // We have two options: | |
236 // A. Transfer the threads from the WaitSet to the EntryList | |
237 // B. Remove the thread from the WaitSet and unpark() it. | |
238 // | |
239 // We use (B), which is crude and results in lots of futile | |
240 // context switching. In particular (B) induces lots of contention. | |
241 | |
242 ParkEvent * ev = NULL ; // consider using a small auto array ... | |
243 RawMonitor_lock->lock_without_safepoint_check() ; | |
244 for (;;) { | |
245 ObjectWaiter * w = _WaitSet ; | |
246 if (w == NULL) break ; | |
247 _WaitSet = w->_next ; | |
248 if (ev != NULL) { ev->unpark(); ev = NULL; } | |
249 ev = w->_event ; | |
250 OrderAccess::loadstore() ; | |
251 w->TState = ObjectWaiter::TS_RUN ; | |
252 OrderAccess::storeload(); | |
253 if (!All) break ; | |
254 } | |
255 RawMonitor_lock->unlock() ; | |
256 if (ev != NULL) ev->unpark(); | |
257 return OS_OK ; | |
258 } | |
259 | |
260 // Any JavaThread will enter here with state _thread_blocked | |
261 int JvmtiRawMonitor::raw_enter(TRAPS) { | |
262 TEVENT (raw_enter) ; | |
263 void * Contended ; | |
264 | |
265 // don't enter raw monitor if thread is being externally suspended, it will | |
266 // surprise the suspender if a "suspended" thread can still enter monitor | |
267 JavaThread * jt = (JavaThread *)THREAD; | |
268 if (THREAD->is_Java_thread()) { | |
269 jt->SR_lock()->lock_without_safepoint_check(); | |
270 while (jt->is_external_suspend()) { | |
271 jt->SR_lock()->unlock(); | |
272 jt->java_suspend_self(); | |
273 jt->SR_lock()->lock_without_safepoint_check(); | |
274 } | |
275 // guarded by SR_lock to avoid racing with new external suspend requests. | |
276 Contended = Atomic::cmpxchg_ptr (THREAD, &_owner, NULL) ; | |
277 jt->SR_lock()->unlock(); | |
278 } else { | |
279 Contended = Atomic::cmpxchg_ptr (THREAD, &_owner, NULL) ; | |
280 } | |
281 | |
282 if (Contended == THREAD) { | |
283 _recursions ++ ; | |
284 return OM_OK ; | |
285 } | |
286 | |
287 if (Contended == NULL) { | |
288 guarantee (_owner == THREAD, "invariant") ; | |
289 guarantee (_recursions == 0, "invariant") ; | |
290 return OM_OK ; | |
291 } | |
292 | |
293 THREAD->set_current_pending_monitor(this); | |
294 | |
295 if (!THREAD->is_Java_thread()) { | |
296 // No other non-Java threads besides VM thread would acquire | |
297 // a raw monitor. | |
298 assert(THREAD->is_VM_thread(), "must be VM thread"); | |
299 SimpleEnter (THREAD) ; | |
300 } else { | |
301 guarantee (jt->thread_state() == _thread_blocked, "invariant") ; | |
302 for (;;) { | |
303 jt->set_suspend_equivalent(); | |
304 // cleared by handle_special_suspend_equivalent_condition() or | |
305 // java_suspend_self() | |
306 SimpleEnter (THREAD) ; | |
307 | |
308 // were we externally suspended while we were waiting? | |
309 if (!jt->handle_special_suspend_equivalent_condition()) break ; | |
310 | |
311 // This thread was externally suspended | |
312 // | |
313 // This logic isn't needed for JVMTI raw monitors, | |
314 // but doesn't hurt just in case the suspend rules change. This | |
315 // logic is needed for the JvmtiRawMonitor.wait() reentry phase. | |
316 // We have reentered the contended monitor, but while we were | |
317 // waiting another thread suspended us. We don't want to reenter | |
318 // the monitor while suspended because that would surprise the | |
319 // thread that suspended us. | |
320 // | |
321 // Drop the lock - | |
322 SimpleExit (THREAD) ; | |
323 | |
324 jt->java_suspend_self(); | |
325 } | |
326 | |
327 assert(_owner == THREAD, "Fatal error with monitor owner!"); | |
328 assert(_recursions == 0, "Fatal error with monitor recursions!"); | |
329 } | |
330 | |
331 THREAD->set_current_pending_monitor(NULL); | |
332 guarantee (_recursions == 0, "invariant") ; | |
333 return OM_OK; | |
334 } | |
335 | |
336 // Used mainly for JVMTI raw monitor implementation | |
337 // Also used for JvmtiRawMonitor::wait(). | |
338 int JvmtiRawMonitor::raw_exit(TRAPS) { | |
339 TEVENT (raw_exit) ; | |
340 if (THREAD != _owner) { | |
341 return OM_ILLEGAL_MONITOR_STATE; | |
342 } | |
343 if (_recursions > 0) { | |
344 --_recursions ; | |
345 return OM_OK ; | |
346 } | |
347 | |
348 void * List = _EntryList ; | |
349 SimpleExit (THREAD) ; | |
350 | |
351 return OM_OK; | |
352 } | |
353 | |
354 // Used for JVMTI raw monitor implementation. | |
355 // All JavaThreads will enter here with state _thread_blocked | |
356 | |
357 int JvmtiRawMonitor::raw_wait(jlong millis, bool interruptible, TRAPS) { | |
358 TEVENT (raw_wait) ; | |
359 if (THREAD != _owner) { | |
360 return OM_ILLEGAL_MONITOR_STATE; | |
361 } | |
362 | |
363 // To avoid spurious wakeups we reset the parkevent -- This is strictly optional. | |
364 // The caller must be able to tolerate spurious returns from raw_wait(). | |
365 THREAD->_ParkEvent->reset() ; | |
366 OrderAccess::fence() ; | |
367 | |
368 // check interrupt event | |
369 if (interruptible && Thread::is_interrupted(THREAD, true)) { | |
370 return OM_INTERRUPTED; | |
371 } | |
372 | |
373 intptr_t save = _recursions ; | |
374 _recursions = 0 ; | |
375 _waiters ++ ; | |
376 if (THREAD->is_Java_thread()) { | |
377 guarantee (((JavaThread *) THREAD)->thread_state() == _thread_blocked, "invariant") ; | |
378 ((JavaThread *)THREAD)->set_suspend_equivalent(); | |
379 } | |
380 int rv = SimpleWait (THREAD, millis) ; | |
381 _recursions = save ; | |
382 _waiters -- ; | |
383 | |
384 guarantee (THREAD == _owner, "invariant") ; | |
385 if (THREAD->is_Java_thread()) { | |
386 JavaThread * jSelf = (JavaThread *) THREAD ; | |
387 for (;;) { | |
388 if (!jSelf->handle_special_suspend_equivalent_condition()) break ; | |
389 SimpleExit (THREAD) ; | |
390 jSelf->java_suspend_self(); | |
391 SimpleEnter (THREAD) ; | |
392 jSelf->set_suspend_equivalent() ; | |
393 } | |
394 } | |
395 guarantee (THREAD == _owner, "invariant") ; | |
396 | |
397 if (interruptible && Thread::is_interrupted(THREAD, true)) { | |
398 return OM_INTERRUPTED; | |
399 } | |
400 return OM_OK ; | |
401 } | |
402 | |
403 int JvmtiRawMonitor::raw_notify(TRAPS) { | |
404 TEVENT (raw_notify) ; | |
405 if (THREAD != _owner) { | |
406 return OM_ILLEGAL_MONITOR_STATE; | |
407 } | |
408 SimpleNotify (THREAD, false) ; | |
409 return OM_OK; | |
410 } | |
411 | |
412 int JvmtiRawMonitor::raw_notifyAll(TRAPS) { | |
413 TEVENT (raw_notifyAll) ; | |
414 if (THREAD != _owner) { | |
415 return OM_ILLEGAL_MONITOR_STATE; | |
416 } | |
417 SimpleNotify (THREAD, true) ; | |
418 return OM_OK; | |
419 } | |
420 |