Mercurial > hg > graal-jvmci-8
annotate src/share/vm/runtime/synchronizer.cpp @ 3960:f08d439fab8c
7089790: integrate bsd-port changes
Reviewed-by: kvn, twisti, jrose
Contributed-by: Kurt Miller <kurt@intricatesoftware.com>, Greg Lewis <glewis@eyesbeyond.com>, Jung-uk Kim <jkim@freebsd.org>, Christos Zoulas <christos@zoulas.com>, Landon Fuller <landonf@plausible.coop>, The FreeBSD Foundation <board@freebsdfoundation.org>, Michael Franz <mvfranz@gmail.com>, Roger Hoover <rhoover@apple.com>, Alexander Strange <astrange@apple.com>
author | never |
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date | Sun, 25 Sep 2011 16:03:29 -0700 |
parents | 1d1603768966 |
children | 436b4a3231bf |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 1998, 2011, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #include "precompiled.hpp" |
26 #include "classfile/vmSymbols.hpp" | |
27 #include "memory/resourceArea.hpp" | |
28 #include "oops/markOop.hpp" | |
29 #include "oops/oop.inline.hpp" | |
30 #include "runtime/biasedLocking.hpp" | |
31 #include "runtime/handles.inline.hpp" | |
32 #include "runtime/interfaceSupport.hpp" | |
33 #include "runtime/mutexLocker.hpp" | |
34 #include "runtime/objectMonitor.hpp" | |
35 #include "runtime/objectMonitor.inline.hpp" | |
36 #include "runtime/osThread.hpp" | |
37 #include "runtime/stubRoutines.hpp" | |
38 #include "runtime/synchronizer.hpp" | |
39 #include "utilities/dtrace.hpp" | |
40 #include "utilities/events.hpp" | |
41 #include "utilities/preserveException.hpp" | |
42 #ifdef TARGET_OS_FAMILY_linux | |
43 # include "os_linux.inline.hpp" | |
44 # include "thread_linux.inline.hpp" | |
45 #endif | |
46 #ifdef TARGET_OS_FAMILY_solaris | |
47 # include "os_solaris.inline.hpp" | |
48 # include "thread_solaris.inline.hpp" | |
49 #endif | |
50 #ifdef TARGET_OS_FAMILY_windows | |
51 # include "os_windows.inline.hpp" | |
52 # include "thread_windows.inline.hpp" | |
53 #endif | |
3960 | 54 #ifdef TARGET_OS_FAMILY_bsd |
55 # include "os_bsd.inline.hpp" | |
56 # include "thread_bsd.inline.hpp" | |
57 #endif | |
0 | 58 |
59 #if defined(__GNUC__) && !defined(IA64) | |
60 // Need to inhibit inlining for older versions of GCC to avoid build-time failures | |
61 #define ATTR __attribute__((noinline)) | |
62 #else | |
63 #define ATTR | |
64 #endif | |
65 | |
66 // The "core" versions of monitor enter and exit reside in this file. | |
67 // The interpreter and compilers contain specialized transliterated | |
68 // variants of the enter-exit fast-path operations. See i486.ad fast_lock(), | |
69 // for instance. If you make changes here, make sure to modify the | |
70 // interpreter, and both C1 and C2 fast-path inline locking code emission. | |
71 // | |
72 // | |
73 // ----------------------------------------------------------------------------- | |
74 | |
75 #ifdef DTRACE_ENABLED | |
76 | |
77 // Only bother with this argument setup if dtrace is available | |
78 // TODO-FIXME: probes should not fire when caller is _blocked. assert() accordingly. | |
79 | |
80 HS_DTRACE_PROBE_DECL5(hotspot, monitor__wait, | |
81 jlong, uintptr_t, char*, int, long); | |
82 HS_DTRACE_PROBE_DECL4(hotspot, monitor__waited, | |
83 jlong, uintptr_t, char*, int); | |
84 | |
85 #define DTRACE_MONITOR_PROBE_COMMON(klassOop, thread) \ | |
86 char* bytes = NULL; \ | |
87 int len = 0; \ | |
88 jlong jtid = SharedRuntime::get_java_tid(thread); \ | |
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89 Symbol* klassname = ((oop)(klassOop))->klass()->klass_part()->name(); \ |
0 | 90 if (klassname != NULL) { \ |
91 bytes = (char*)klassname->bytes(); \ | |
92 len = klassname->utf8_length(); \ | |
93 } | |
94 | |
95 #define DTRACE_MONITOR_WAIT_PROBE(monitor, klassOop, thread, millis) \ | |
96 { \ | |
97 if (DTraceMonitorProbes) { \ | |
98 DTRACE_MONITOR_PROBE_COMMON(klassOop, thread); \ | |
99 HS_DTRACE_PROBE5(hotspot, monitor__wait, jtid, \ | |
100 (monitor), bytes, len, (millis)); \ | |
101 } \ | |
102 } | |
103 | |
104 #define DTRACE_MONITOR_PROBE(probe, monitor, klassOop, thread) \ | |
105 { \ | |
106 if (DTraceMonitorProbes) { \ | |
107 DTRACE_MONITOR_PROBE_COMMON(klassOop, thread); \ | |
108 HS_DTRACE_PROBE4(hotspot, monitor__##probe, jtid, \ | |
109 (uintptr_t)(monitor), bytes, len); \ | |
110 } \ | |
111 } | |
112 | |
113 #else // ndef DTRACE_ENABLED | |
114 | |
115 #define DTRACE_MONITOR_WAIT_PROBE(klassOop, thread, millis, mon) {;} | |
116 #define DTRACE_MONITOR_PROBE(probe, klassOop, thread, mon) {;} | |
117 | |
118 #endif // ndef DTRACE_ENABLED | |
119 | |
1878 | 120 // This exists only as a workaround of dtrace bug 6254741 |
121 int dtrace_waited_probe(ObjectMonitor* monitor, Handle obj, Thread* thr) { | |
122 DTRACE_MONITOR_PROBE(waited, monitor, obj(), thr); | |
123 return 0; | |
124 } | |
125 | |
126 #define NINFLATIONLOCKS 256 | |
127 static volatile intptr_t InflationLocks [NINFLATIONLOCKS] ; | |
128 | |
129 ObjectMonitor * ObjectSynchronizer::gBlockList = NULL ; | |
130 ObjectMonitor * volatile ObjectSynchronizer::gFreeList = NULL ; | |
131 ObjectMonitor * volatile ObjectSynchronizer::gOmInUseList = NULL ; | |
132 int ObjectSynchronizer::gOmInUseCount = 0; | |
133 static volatile intptr_t ListLock = 0 ; // protects global monitor free-list cache | |
134 static volatile int MonitorFreeCount = 0 ; // # on gFreeList | |
135 static volatile int MonitorPopulation = 0 ; // # Extant -- in circulation | |
136 #define CHAINMARKER ((oop)-1) | |
137 | |
138 // ----------------------------------------------------------------------------- | |
139 // Fast Monitor Enter/Exit | |
140 // This the fast monitor enter. The interpreter and compiler use | |
141 // some assembly copies of this code. Make sure update those code | |
142 // if the following function is changed. The implementation is | |
143 // extremely sensitive to race condition. Be careful. | |
144 | |
145 void ObjectSynchronizer::fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias, TRAPS) { | |
146 if (UseBiasedLocking) { | |
147 if (!SafepointSynchronize::is_at_safepoint()) { | |
148 BiasedLocking::Condition cond = BiasedLocking::revoke_and_rebias(obj, attempt_rebias, THREAD); | |
149 if (cond == BiasedLocking::BIAS_REVOKED_AND_REBIASED) { | |
150 return; | |
151 } | |
152 } else { | |
153 assert(!attempt_rebias, "can not rebias toward VM thread"); | |
154 BiasedLocking::revoke_at_safepoint(obj); | |
155 } | |
156 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
157 } | |
158 | |
159 slow_enter (obj, lock, THREAD) ; | |
160 } | |
161 | |
162 void ObjectSynchronizer::fast_exit(oop object, BasicLock* lock, TRAPS) { | |
163 assert(!object->mark()->has_bias_pattern(), "should not see bias pattern here"); | |
164 // if displaced header is null, the previous enter is recursive enter, no-op | |
165 markOop dhw = lock->displaced_header(); | |
166 markOop mark ; | |
167 if (dhw == NULL) { | |
168 // Recursive stack-lock. | |
169 // Diagnostics -- Could be: stack-locked, inflating, inflated. | |
170 mark = object->mark() ; | |
171 assert (!mark->is_neutral(), "invariant") ; | |
172 if (mark->has_locker() && mark != markOopDesc::INFLATING()) { | |
173 assert(THREAD->is_lock_owned((address)mark->locker()), "invariant") ; | |
174 } | |
175 if (mark->has_monitor()) { | |
176 ObjectMonitor * m = mark->monitor() ; | |
177 assert(((oop)(m->object()))->mark() == mark, "invariant") ; | |
178 assert(m->is_entered(THREAD), "invariant") ; | |
179 } | |
180 return ; | |
181 } | |
182 | |
183 mark = object->mark() ; | |
0 | 184 |
1878 | 185 // If the object is stack-locked by the current thread, try to |
186 // swing the displaced header from the box back to the mark. | |
187 if (mark == (markOop) lock) { | |
188 assert (dhw->is_neutral(), "invariant") ; | |
189 if ((markOop) Atomic::cmpxchg_ptr (dhw, object->mark_addr(), mark) == mark) { | |
190 TEVENT (fast_exit: release stacklock) ; | |
191 return; | |
192 } | |
193 } | |
194 | |
195 ObjectSynchronizer::inflate(THREAD, object)->exit (THREAD) ; | |
196 } | |
197 | |
198 // ----------------------------------------------------------------------------- | |
199 // Interpreter/Compiler Slow Case | |
200 // This routine is used to handle interpreter/compiler slow case | |
201 // We don't need to use fast path here, because it must have been | |
202 // failed in the interpreter/compiler code. | |
203 void ObjectSynchronizer::slow_enter(Handle obj, BasicLock* lock, TRAPS) { | |
204 markOop mark = obj->mark(); | |
205 assert(!mark->has_bias_pattern(), "should not see bias pattern here"); | |
206 | |
207 if (mark->is_neutral()) { | |
208 // Anticipate successful CAS -- the ST of the displaced mark must | |
209 // be visible <= the ST performed by the CAS. | |
210 lock->set_displaced_header(mark); | |
211 if (mark == (markOop) Atomic::cmpxchg_ptr(lock, obj()->mark_addr(), mark)) { | |
212 TEVENT (slow_enter: release stacklock) ; | |
213 return ; | |
214 } | |
215 // Fall through to inflate() ... | |
216 } else | |
217 if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { | |
218 assert(lock != mark->locker(), "must not re-lock the same lock"); | |
219 assert(lock != (BasicLock*)obj->mark(), "don't relock with same BasicLock"); | |
220 lock->set_displaced_header(NULL); | |
221 return; | |
222 } | |
223 | |
224 #if 0 | |
225 // The following optimization isn't particularly useful. | |
226 if (mark->has_monitor() && mark->monitor()->is_entered(THREAD)) { | |
227 lock->set_displaced_header (NULL) ; | |
228 return ; | |
229 } | |
230 #endif | |
231 | |
232 // The object header will never be displaced to this lock, | |
233 // so it does not matter what the value is, except that it | |
234 // must be non-zero to avoid looking like a re-entrant lock, | |
235 // and must not look locked either. | |
236 lock->set_displaced_header(markOopDesc::unused_mark()); | |
237 ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD); | |
238 } | |
239 | |
240 // This routine is used to handle interpreter/compiler slow case | |
241 // We don't need to use fast path here, because it must have | |
242 // failed in the interpreter/compiler code. Simply use the heavy | |
243 // weight monitor should be ok, unless someone find otherwise. | |
244 void ObjectSynchronizer::slow_exit(oop object, BasicLock* lock, TRAPS) { | |
245 fast_exit (object, lock, THREAD) ; | |
246 } | |
247 | |
248 // ----------------------------------------------------------------------------- | |
249 // Class Loader support to workaround deadlocks on the class loader lock objects | |
250 // Also used by GC | |
251 // complete_exit()/reenter() are used to wait on a nested lock | |
252 // i.e. to give up an outer lock completely and then re-enter | |
253 // Used when holding nested locks - lock acquisition order: lock1 then lock2 | |
254 // 1) complete_exit lock1 - saving recursion count | |
255 // 2) wait on lock2 | |
256 // 3) when notified on lock2, unlock lock2 | |
257 // 4) reenter lock1 with original recursion count | |
258 // 5) lock lock2 | |
259 // NOTE: must use heavy weight monitor to handle complete_exit/reenter() | |
260 intptr_t ObjectSynchronizer::complete_exit(Handle obj, TRAPS) { | |
261 TEVENT (complete_exit) ; | |
262 if (UseBiasedLocking) { | |
263 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
264 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
0 | 265 } |
266 | |
1878 | 267 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); |
268 | |
269 return monitor->complete_exit(THREAD); | |
270 } | |
271 | |
272 // NOTE: must use heavy weight monitor to handle complete_exit/reenter() | |
273 void ObjectSynchronizer::reenter(Handle obj, intptr_t recursion, TRAPS) { | |
274 TEVENT (reenter) ; | |
275 if (UseBiasedLocking) { | |
276 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
277 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
278 } | |
279 | |
280 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); | |
281 | |
282 monitor->reenter(recursion, THREAD); | |
283 } | |
284 // ----------------------------------------------------------------------------- | |
285 // JNI locks on java objects | |
286 // NOTE: must use heavy weight monitor to handle jni monitor enter | |
287 void ObjectSynchronizer::jni_enter(Handle obj, TRAPS) { // possible entry from jni enter | |
288 // the current locking is from JNI instead of Java code | |
289 TEVENT (jni_enter) ; | |
290 if (UseBiasedLocking) { | |
291 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
292 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
293 } | |
294 THREAD->set_current_pending_monitor_is_from_java(false); | |
295 ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD); | |
296 THREAD->set_current_pending_monitor_is_from_java(true); | |
297 } | |
298 | |
299 // NOTE: must use heavy weight monitor to handle jni monitor enter | |
300 bool ObjectSynchronizer::jni_try_enter(Handle obj, Thread* THREAD) { | |
301 if (UseBiasedLocking) { | |
302 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
303 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
0 | 304 } |
305 | |
1878 | 306 ObjectMonitor* monitor = ObjectSynchronizer::inflate_helper(obj()); |
307 return monitor->try_enter(THREAD); | |
308 } | |
309 | |
310 | |
311 // NOTE: must use heavy weight monitor to handle jni monitor exit | |
312 void ObjectSynchronizer::jni_exit(oop obj, Thread* THREAD) { | |
313 TEVENT (jni_exit) ; | |
314 if (UseBiasedLocking) { | |
315 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
316 } | |
317 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
318 | |
319 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj); | |
320 // If this thread has locked the object, exit the monitor. Note: can't use | |
321 // monitor->check(CHECK); must exit even if an exception is pending. | |
322 if (monitor->check(THREAD)) { | |
323 monitor->exit(THREAD); | |
0 | 324 } |
1878 | 325 } |
326 | |
327 // ----------------------------------------------------------------------------- | |
328 // Internal VM locks on java objects | |
329 // standard constructor, allows locking failures | |
330 ObjectLocker::ObjectLocker(Handle obj, Thread* thread, bool doLock) { | |
331 _dolock = doLock; | |
332 _thread = thread; | |
333 debug_only(if (StrictSafepointChecks) _thread->check_for_valid_safepoint_state(false);) | |
334 _obj = obj; | |
0 | 335 |
1878 | 336 if (_dolock) { |
337 TEVENT (ObjectLocker) ; | |
338 | |
339 ObjectSynchronizer::fast_enter(_obj, &_lock, false, _thread); | |
340 } | |
341 } | |
342 | |
343 ObjectLocker::~ObjectLocker() { | |
344 if (_dolock) { | |
345 ObjectSynchronizer::fast_exit(_obj(), &_lock, _thread); | |
346 } | |
347 } | |
0 | 348 |
349 | |
1878 | 350 // ----------------------------------------------------------------------------- |
351 // Wait/Notify/NotifyAll | |
352 // NOTE: must use heavy weight monitor to handle wait() | |
353 void ObjectSynchronizer::wait(Handle obj, jlong millis, TRAPS) { | |
354 if (UseBiasedLocking) { | |
355 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
356 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
357 } | |
358 if (millis < 0) { | |
359 TEVENT (wait - throw IAX) ; | |
360 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); | |
361 } | |
362 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); | |
363 DTRACE_MONITOR_WAIT_PROBE(monitor, obj(), THREAD, millis); | |
364 monitor->wait(millis, true, THREAD); | |
365 | |
366 /* This dummy call is in place to get around dtrace bug 6254741. Once | |
367 that's fixed we can uncomment the following line and remove the call */ | |
368 // DTRACE_MONITOR_PROBE(waited, monitor, obj(), THREAD); | |
369 dtrace_waited_probe(monitor, obj, THREAD); | |
370 } | |
0 | 371 |
1878 | 372 void ObjectSynchronizer::waitUninterruptibly (Handle obj, jlong millis, TRAPS) { |
373 if (UseBiasedLocking) { | |
374 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
375 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
376 } | |
377 if (millis < 0) { | |
378 TEVENT (wait - throw IAX) ; | |
379 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); | |
380 } | |
381 ObjectSynchronizer::inflate(THREAD, obj()) -> wait(millis, false, THREAD) ; | |
382 } | |
383 | |
384 void ObjectSynchronizer::notify(Handle obj, TRAPS) { | |
385 if (UseBiasedLocking) { | |
386 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
387 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
388 } | |
0 | 389 |
1878 | 390 markOop mark = obj->mark(); |
391 if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { | |
392 return; | |
393 } | |
394 ObjectSynchronizer::inflate(THREAD, obj())->notify(THREAD); | |
395 } | |
0 | 396 |
1878 | 397 // NOTE: see comment of notify() |
398 void ObjectSynchronizer::notifyall(Handle obj, TRAPS) { | |
399 if (UseBiasedLocking) { | |
400 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
401 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
402 } | |
403 | |
404 markOop mark = obj->mark(); | |
405 if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { | |
406 return; | |
407 } | |
408 ObjectSynchronizer::inflate(THREAD, obj())->notifyAll(THREAD); | |
409 } | |
410 | |
411 // ----------------------------------------------------------------------------- | |
412 // Hash Code handling | |
413 // | |
0 | 414 // Performance concern: |
415 // OrderAccess::storestore() calls release() which STs 0 into the global volatile | |
416 // OrderAccess::Dummy variable. This store is unnecessary for correctness. | |
417 // Many threads STing into a common location causes considerable cache migration | |
418 // or "sloshing" on large SMP system. As such, I avoid using OrderAccess::storestore() | |
419 // until it's repaired. In some cases OrderAccess::fence() -- which incurs local | |
420 // latency on the executing processor -- is a better choice as it scales on SMP | |
421 // systems. See http://blogs.sun.com/dave/entry/biased_locking_in_hotspot for a | |
422 // discussion of coherency costs. Note that all our current reference platforms | |
423 // provide strong ST-ST order, so the issue is moot on IA32, x64, and SPARC. | |
424 // | |
425 // As a general policy we use "volatile" to control compiler-based reordering | |
426 // and explicit fences (barriers) to control for architectural reordering performed | |
427 // by the CPU(s) or platform. | |
428 | |
429 static int MBFence (int x) { OrderAccess::fence(); return x; } | |
430 | |
431 struct SharedGlobals { | |
432 // These are highly shared mostly-read variables. | |
433 // To avoid false-sharing they need to be the sole occupants of a $ line. | |
434 double padPrefix [8]; | |
435 volatile int stwRandom ; | |
436 volatile int stwCycle ; | |
437 | |
438 // Hot RW variables -- Sequester to avoid false-sharing | |
439 double padSuffix [16]; | |
440 volatile int hcSequence ; | |
441 double padFinal [8] ; | |
442 } ; | |
443 | |
444 static SharedGlobals GVars ; | |
1587 | 445 static int MonitorScavengeThreshold = 1000000 ; |
446 static volatile int ForceMonitorScavenge = 0 ; // Scavenge required and pending | |
0 | 447 |
1878 | 448 static markOop ReadStableMark (oop obj) { |
449 markOop mark = obj->mark() ; | |
450 if (!mark->is_being_inflated()) { | |
451 return mark ; // normal fast-path return | |
452 } | |
0 | 453 |
1878 | 454 int its = 0 ; |
455 for (;;) { | |
456 markOop mark = obj->mark() ; | |
457 if (!mark->is_being_inflated()) { | |
458 return mark ; // normal fast-path return | |
459 } | |
460 | |
461 // The object is being inflated by some other thread. | |
462 // The caller of ReadStableMark() must wait for inflation to complete. | |
463 // Avoid live-lock | |
464 // TODO: consider calling SafepointSynchronize::do_call_back() while | |
465 // spinning to see if there's a safepoint pending. If so, immediately | |
466 // yielding or blocking would be appropriate. Avoid spinning while | |
467 // there is a safepoint pending. | |
468 // TODO: add inflation contention performance counters. | |
469 // TODO: restrict the aggregate number of spinners. | |
0 | 470 |
1878 | 471 ++its ; |
472 if (its > 10000 || !os::is_MP()) { | |
473 if (its & 1) { | |
474 os::NakedYield() ; | |
475 TEVENT (Inflate: INFLATING - yield) ; | |
476 } else { | |
477 // Note that the following code attenuates the livelock problem but is not | |
478 // a complete remedy. A more complete solution would require that the inflating | |
479 // thread hold the associated inflation lock. The following code simply restricts | |
480 // the number of spinners to at most one. We'll have N-2 threads blocked | |
481 // on the inflationlock, 1 thread holding the inflation lock and using | |
482 // a yield/park strategy, and 1 thread in the midst of inflation. | |
483 // A more refined approach would be to change the encoding of INFLATING | |
484 // to allow encapsulation of a native thread pointer. Threads waiting for | |
485 // inflation to complete would use CAS to push themselves onto a singly linked | |
486 // list rooted at the markword. Once enqueued, they'd loop, checking a per-thread flag | |
487 // and calling park(). When inflation was complete the thread that accomplished inflation | |
488 // would detach the list and set the markword to inflated with a single CAS and | |
489 // then for each thread on the list, set the flag and unpark() the thread. | |
490 // This is conceptually similar to muxAcquire-muxRelease, except that muxRelease | |
491 // wakes at most one thread whereas we need to wake the entire list. | |
492 int ix = (intptr_t(obj) >> 5) & (NINFLATIONLOCKS-1) ; | |
493 int YieldThenBlock = 0 ; | |
494 assert (ix >= 0 && ix < NINFLATIONLOCKS, "invariant") ; | |
495 assert ((NINFLATIONLOCKS & (NINFLATIONLOCKS-1)) == 0, "invariant") ; | |
496 Thread::muxAcquire (InflationLocks + ix, "InflationLock") ; | |
497 while (obj->mark() == markOopDesc::INFLATING()) { | |
498 // Beware: NakedYield() is advisory and has almost no effect on some platforms | |
499 // so we periodically call Self->_ParkEvent->park(1). | |
500 // We use a mixed spin/yield/block mechanism. | |
501 if ((YieldThenBlock++) >= 16) { | |
502 Thread::current()->_ParkEvent->park(1) ; | |
503 } else { | |
504 os::NakedYield() ; | |
505 } | |
506 } | |
507 Thread::muxRelease (InflationLocks + ix ) ; | |
508 TEVENT (Inflate: INFLATING - yield/park) ; | |
509 } | |
510 } else { | |
511 SpinPause() ; // SMP-polite spinning | |
512 } | |
513 } | |
514 } | |
0 | 515 |
516 // hashCode() generation : | |
517 // | |
518 // Possibilities: | |
519 // * MD5Digest of {obj,stwRandom} | |
520 // * CRC32 of {obj,stwRandom} or any linear-feedback shift register function. | |
521 // * A DES- or AES-style SBox[] mechanism | |
522 // * One of the Phi-based schemes, such as: | |
523 // 2654435761 = 2^32 * Phi (golden ratio) | |
524 // HashCodeValue = ((uintptr_t(obj) >> 3) * 2654435761) ^ GVars.stwRandom ; | |
525 // * A variation of Marsaglia's shift-xor RNG scheme. | |
526 // * (obj ^ stwRandom) is appealing, but can result | |
527 // in undesirable regularity in the hashCode values of adjacent objects | |
528 // (objects allocated back-to-back, in particular). This could potentially | |
529 // result in hashtable collisions and reduced hashtable efficiency. | |
530 // There are simple ways to "diffuse" the middle address bits over the | |
531 // generated hashCode values: | |
532 // | |
533 | |
534 static inline intptr_t get_next_hash(Thread * Self, oop obj) { | |
535 intptr_t value = 0 ; | |
536 if (hashCode == 0) { | |
537 // This form uses an unguarded global Park-Miller RNG, | |
538 // so it's possible for two threads to race and generate the same RNG. | |
539 // On MP system we'll have lots of RW access to a global, so the | |
540 // mechanism induces lots of coherency traffic. | |
541 value = os::random() ; | |
542 } else | |
543 if (hashCode == 1) { | |
544 // This variation has the property of being stable (idempotent) | |
545 // between STW operations. This can be useful in some of the 1-0 | |
546 // synchronization schemes. | |
547 intptr_t addrBits = intptr_t(obj) >> 3 ; | |
548 value = addrBits ^ (addrBits >> 5) ^ GVars.stwRandom ; | |
549 } else | |
550 if (hashCode == 2) { | |
551 value = 1 ; // for sensitivity testing | |
552 } else | |
553 if (hashCode == 3) { | |
554 value = ++GVars.hcSequence ; | |
555 } else | |
556 if (hashCode == 4) { | |
557 value = intptr_t(obj) ; | |
558 } else { | |
559 // Marsaglia's xor-shift scheme with thread-specific state | |
560 // This is probably the best overall implementation -- we'll | |
561 // likely make this the default in future releases. | |
562 unsigned t = Self->_hashStateX ; | |
563 t ^= (t << 11) ; | |
564 Self->_hashStateX = Self->_hashStateY ; | |
565 Self->_hashStateY = Self->_hashStateZ ; | |
566 Self->_hashStateZ = Self->_hashStateW ; | |
567 unsigned v = Self->_hashStateW ; | |
568 v = (v ^ (v >> 19)) ^ (t ^ (t >> 8)) ; | |
569 Self->_hashStateW = v ; | |
570 value = v ; | |
571 } | |
572 | |
573 value &= markOopDesc::hash_mask; | |
574 if (value == 0) value = 0xBAD ; | |
575 assert (value != markOopDesc::no_hash, "invariant") ; | |
576 TEVENT (hashCode: GENERATE) ; | |
577 return value; | |
578 } | |
1878 | 579 // |
580 intptr_t ObjectSynchronizer::FastHashCode (Thread * Self, oop obj) { | |
581 if (UseBiasedLocking) { | |
582 // NOTE: many places throughout the JVM do not expect a safepoint | |
583 // to be taken here, in particular most operations on perm gen | |
584 // objects. However, we only ever bias Java instances and all of | |
585 // the call sites of identity_hash that might revoke biases have | |
586 // been checked to make sure they can handle a safepoint. The | |
587 // added check of the bias pattern is to avoid useless calls to | |
588 // thread-local storage. | |
589 if (obj->mark()->has_bias_pattern()) { | |
590 // Box and unbox the raw reference just in case we cause a STW safepoint. | |
591 Handle hobj (Self, obj) ; | |
592 // Relaxing assertion for bug 6320749. | |
593 assert (Universe::verify_in_progress() || | |
594 !SafepointSynchronize::is_at_safepoint(), | |
595 "biases should not be seen by VM thread here"); | |
596 BiasedLocking::revoke_and_rebias(hobj, false, JavaThread::current()); | |
597 obj = hobj() ; | |
598 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
599 } | |
600 } | |
0 | 601 |
1878 | 602 // hashCode() is a heap mutator ... |
603 // Relaxing assertion for bug 6320749. | |
604 assert (Universe::verify_in_progress() || | |
605 !SafepointSynchronize::is_at_safepoint(), "invariant") ; | |
606 assert (Universe::verify_in_progress() || | |
607 Self->is_Java_thread() , "invariant") ; | |
608 assert (Universe::verify_in_progress() || | |
609 ((JavaThread *)Self)->thread_state() != _thread_blocked, "invariant") ; | |
610 | |
611 ObjectMonitor* monitor = NULL; | |
612 markOop temp, test; | |
613 intptr_t hash; | |
614 markOop mark = ReadStableMark (obj); | |
615 | |
616 // object should remain ineligible for biased locking | |
617 assert (!mark->has_bias_pattern(), "invariant") ; | |
618 | |
619 if (mark->is_neutral()) { | |
620 hash = mark->hash(); // this is a normal header | |
621 if (hash) { // if it has hash, just return it | |
622 return hash; | |
623 } | |
624 hash = get_next_hash(Self, obj); // allocate a new hash code | |
625 temp = mark->copy_set_hash(hash); // merge the hash code into header | |
626 // use (machine word version) atomic operation to install the hash | |
627 test = (markOop) Atomic::cmpxchg_ptr(temp, obj->mark_addr(), mark); | |
628 if (test == mark) { | |
629 return hash; | |
630 } | |
631 // If atomic operation failed, we must inflate the header | |
632 // into heavy weight monitor. We could add more code here | |
633 // for fast path, but it does not worth the complexity. | |
634 } else if (mark->has_monitor()) { | |
635 monitor = mark->monitor(); | |
636 temp = monitor->header(); | |
637 assert (temp->is_neutral(), "invariant") ; | |
638 hash = temp->hash(); | |
639 if (hash) { | |
640 return hash; | |
641 } | |
642 // Skip to the following code to reduce code size | |
643 } else if (Self->is_lock_owned((address)mark->locker())) { | |
644 temp = mark->displaced_mark_helper(); // this is a lightweight monitor owned | |
645 assert (temp->is_neutral(), "invariant") ; | |
646 hash = temp->hash(); // by current thread, check if the displaced | |
647 if (hash) { // header contains hash code | |
648 return hash; | |
649 } | |
650 // WARNING: | |
651 // The displaced header is strictly immutable. | |
652 // It can NOT be changed in ANY cases. So we have | |
653 // to inflate the header into heavyweight monitor | |
654 // even the current thread owns the lock. The reason | |
655 // is the BasicLock (stack slot) will be asynchronously | |
656 // read by other threads during the inflate() function. | |
657 // Any change to stack may not propagate to other threads | |
658 // correctly. | |
659 } | |
660 | |
661 // Inflate the monitor to set hash code | |
662 monitor = ObjectSynchronizer::inflate(Self, obj); | |
663 // Load displaced header and check it has hash code | |
664 mark = monitor->header(); | |
665 assert (mark->is_neutral(), "invariant") ; | |
666 hash = mark->hash(); | |
667 if (hash == 0) { | |
668 hash = get_next_hash(Self, obj); | |
669 temp = mark->copy_set_hash(hash); // merge hash code into header | |
670 assert (temp->is_neutral(), "invariant") ; | |
671 test = (markOop) Atomic::cmpxchg_ptr(temp, monitor, mark); | |
672 if (test != mark) { | |
673 // The only update to the header in the monitor (outside GC) | |
674 // is install the hash code. If someone add new usage of | |
675 // displaced header, please update this code | |
676 hash = test->hash(); | |
677 assert (test->is_neutral(), "invariant") ; | |
678 assert (hash != 0, "Trivial unexpected object/monitor header usage."); | |
679 } | |
680 } | |
681 // We finally get the hash | |
682 return hash; | |
0 | 683 } |
684 | |
1878 | 685 // Deprecated -- use FastHashCode() instead. |
0 | 686 |
1878 | 687 intptr_t ObjectSynchronizer::identity_hash_value_for(Handle obj) { |
688 return FastHashCode (Thread::current(), obj()) ; | |
0 | 689 } |
690 | |
691 | |
1878 | 692 bool ObjectSynchronizer::current_thread_holds_lock(JavaThread* thread, |
693 Handle h_obj) { | |
694 if (UseBiasedLocking) { | |
695 BiasedLocking::revoke_and_rebias(h_obj, false, thread); | |
696 assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
697 } | |
698 | |
699 assert(thread == JavaThread::current(), "Can only be called on current thread"); | |
700 oop obj = h_obj(); | |
701 | |
702 markOop mark = ReadStableMark (obj) ; | |
0 | 703 |
1878 | 704 // Uncontended case, header points to stack |
705 if (mark->has_locker()) { | |
706 return thread->is_lock_owned((address)mark->locker()); | |
0 | 707 } |
1878 | 708 // Contended case, header points to ObjectMonitor (tagged pointer) |
709 if (mark->has_monitor()) { | |
710 ObjectMonitor* monitor = mark->monitor(); | |
711 return monitor->is_entered(thread) != 0 ; | |
0 | 712 } |
1878 | 713 // Unlocked case, header in place |
714 assert(mark->is_neutral(), "sanity check"); | |
715 return false; | |
0 | 716 } |
717 | |
1878 | 718 // Be aware of this method could revoke bias of the lock object. |
719 // This method querys the ownership of the lock handle specified by 'h_obj'. | |
720 // If the current thread owns the lock, it returns owner_self. If no | |
721 // thread owns the lock, it returns owner_none. Otherwise, it will return | |
722 // ower_other. | |
723 ObjectSynchronizer::LockOwnership ObjectSynchronizer::query_lock_ownership | |
724 (JavaThread *self, Handle h_obj) { | |
725 // The caller must beware this method can revoke bias, and | |
726 // revocation can result in a safepoint. | |
727 assert (!SafepointSynchronize::is_at_safepoint(), "invariant") ; | |
728 assert (self->thread_state() != _thread_blocked , "invariant") ; | |
0 | 729 |
1878 | 730 // Possible mark states: neutral, biased, stack-locked, inflated |
731 | |
732 if (UseBiasedLocking && h_obj()->mark()->has_bias_pattern()) { | |
733 // CASE: biased | |
734 BiasedLocking::revoke_and_rebias(h_obj, false, self); | |
735 assert(!h_obj->mark()->has_bias_pattern(), | |
736 "biases should be revoked by now"); | |
737 } | |
0 | 738 |
1878 | 739 assert(self == JavaThread::current(), "Can only be called on current thread"); |
740 oop obj = h_obj(); | |
741 markOop mark = ReadStableMark (obj) ; | |
742 | |
743 // CASE: stack-locked. Mark points to a BasicLock on the owner's stack. | |
744 if (mark->has_locker()) { | |
745 return self->is_lock_owned((address)mark->locker()) ? | |
746 owner_self : owner_other; | |
747 } | |
0 | 748 |
1878 | 749 // CASE: inflated. Mark (tagged pointer) points to an objectMonitor. |
750 // The Object:ObjectMonitor relationship is stable as long as we're | |
751 // not at a safepoint. | |
752 if (mark->has_monitor()) { | |
753 void * owner = mark->monitor()->_owner ; | |
754 if (owner == NULL) return owner_none ; | |
755 return (owner == self || | |
756 self->is_lock_owned((address)owner)) ? owner_self : owner_other; | |
757 } | |
758 | |
759 // CASE: neutral | |
760 assert(mark->is_neutral(), "sanity check"); | |
761 return owner_none ; // it's unlocked | |
762 } | |
0 | 763 |
1878 | 764 // FIXME: jvmti should call this |
765 JavaThread* ObjectSynchronizer::get_lock_owner(Handle h_obj, bool doLock) { | |
766 if (UseBiasedLocking) { | |
767 if (SafepointSynchronize::is_at_safepoint()) { | |
768 BiasedLocking::revoke_at_safepoint(h_obj); | |
769 } else { | |
770 BiasedLocking::revoke_and_rebias(h_obj, false, JavaThread::current()); | |
771 } | |
772 assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
773 } | |
774 | |
775 oop obj = h_obj(); | |
776 address owner = NULL; | |
777 | |
778 markOop mark = ReadStableMark (obj) ; | |
779 | |
780 // Uncontended case, header points to stack | |
781 if (mark->has_locker()) { | |
782 owner = (address) mark->locker(); | |
783 } | |
784 | |
785 // Contended case, header points to ObjectMonitor (tagged pointer) | |
786 if (mark->has_monitor()) { | |
787 ObjectMonitor* monitor = mark->monitor(); | |
788 assert(monitor != NULL, "monitor should be non-null"); | |
789 owner = (address) monitor->owner(); | |
790 } | |
791 | |
792 if (owner != NULL) { | |
793 return Threads::owning_thread_from_monitor_owner(owner, doLock); | |
794 } | |
795 | |
796 // Unlocked case, header in place | |
797 // Cannot have assertion since this object may have been | |
798 // locked by another thread when reaching here. | |
799 // assert(mark->is_neutral(), "sanity check"); | |
800 | |
801 return NULL; | |
802 } | |
803 // Visitors ... | |
804 | |
805 void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure) { | |
806 ObjectMonitor* block = gBlockList; | |
807 ObjectMonitor* mid; | |
808 while (block) { | |
809 assert(block->object() == CHAINMARKER, "must be a block header"); | |
810 for (int i = _BLOCKSIZE - 1; i > 0; i--) { | |
811 mid = block + i; | |
812 oop object = (oop) mid->object(); | |
813 if (object != NULL) { | |
814 closure->do_monitor(mid); | |
815 } | |
816 } | |
817 block = (ObjectMonitor*) block->FreeNext; | |
0 | 818 } |
819 } | |
820 | |
1878 | 821 // Get the next block in the block list. |
822 static inline ObjectMonitor* next(ObjectMonitor* block) { | |
823 assert(block->object() == CHAINMARKER, "must be a block header"); | |
824 block = block->FreeNext ; | |
825 assert(block == NULL || block->object() == CHAINMARKER, "must be a block header"); | |
826 return block; | |
0 | 827 } |
828 | |
829 | |
1878 | 830 void ObjectSynchronizer::oops_do(OopClosure* f) { |
831 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); | |
832 for (ObjectMonitor* block = gBlockList; block != NULL; block = next(block)) { | |
833 assert(block->object() == CHAINMARKER, "must be a block header"); | |
834 for (int i = 1; i < _BLOCKSIZE; i++) { | |
835 ObjectMonitor* mid = &block[i]; | |
836 if (mid->object() != NULL) { | |
837 f->do_oop((oop*)mid->object_addr()); | |
0 | 838 } |
839 } | |
840 } | |
841 } | |
842 | |
843 | |
1878 | 844 // ----------------------------------------------------------------------------- |
0 | 845 // ObjectMonitor Lifecycle |
846 // ----------------------- | |
847 // Inflation unlinks monitors from the global gFreeList and | |
848 // associates them with objects. Deflation -- which occurs at | |
849 // STW-time -- disassociates idle monitors from objects. Such | |
850 // scavenged monitors are returned to the gFreeList. | |
851 // | |
852 // The global list is protected by ListLock. All the critical sections | |
853 // are short and operate in constant-time. | |
854 // | |
855 // ObjectMonitors reside in type-stable memory (TSM) and are immortal. | |
856 // | |
857 // Lifecycle: | |
858 // -- unassigned and on the global free list | |
859 // -- unassigned and on a thread's private omFreeList | |
860 // -- assigned to an object. The object is inflated and the mark refers | |
861 // to the objectmonitor. | |
862 // | |
863 | |
864 | |
1587 | 865 // Constraining monitor pool growth via MonitorBound ... |
866 // | |
867 // The monitor pool is grow-only. We scavenge at STW safepoint-time, but the | |
868 // the rate of scavenging is driven primarily by GC. As such, we can find | |
869 // an inordinate number of monitors in circulation. | |
870 // To avoid that scenario we can artificially induce a STW safepoint | |
871 // if the pool appears to be growing past some reasonable bound. | |
872 // Generally we favor time in space-time tradeoffs, but as there's no | |
873 // natural back-pressure on the # of extant monitors we need to impose some | |
874 // type of limit. Beware that if MonitorBound is set to too low a value | |
875 // we could just loop. In addition, if MonitorBound is set to a low value | |
876 // we'll incur more safepoints, which are harmful to performance. | |
877 // See also: GuaranteedSafepointInterval | |
878 // | |
879 // The current implementation uses asynchronous VM operations. | |
880 // | |
881 | |
882 static void InduceScavenge (Thread * Self, const char * Whence) { | |
883 // Induce STW safepoint to trim monitors | |
884 // Ultimately, this results in a call to deflate_idle_monitors() in the near future. | |
885 // More precisely, trigger an asynchronous STW safepoint as the number | |
886 // of active monitors passes the specified threshold. | |
887 // TODO: assert thread state is reasonable | |
888 | |
889 if (ForceMonitorScavenge == 0 && Atomic::xchg (1, &ForceMonitorScavenge) == 0) { | |
1878 | 890 if (ObjectMonitor::Knob_Verbose) { |
1587 | 891 ::printf ("Monitor scavenge - Induced STW @%s (%d)\n", Whence, ForceMonitorScavenge) ; |
892 ::fflush(stdout) ; | |
893 } | |
894 // Induce a 'null' safepoint to scavenge monitors | |
895 // Must VM_Operation instance be heap allocated as the op will be enqueue and posted | |
896 // to the VMthread and have a lifespan longer than that of this activation record. | |
897 // The VMThread will delete the op when completed. | |
898 VMThread::execute (new VM_ForceAsyncSafepoint()) ; | |
899 | |
1878 | 900 if (ObjectMonitor::Knob_Verbose) { |
1587 | 901 ::printf ("Monitor scavenge - STW posted @%s (%d)\n", Whence, ForceMonitorScavenge) ; |
902 ::fflush(stdout) ; | |
903 } | |
904 } | |
905 } | |
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906 /* Too slow for general assert or debug |
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907 void ObjectSynchronizer::verifyInUse (Thread *Self) { |
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908 ObjectMonitor* mid; |
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909 int inusetally = 0; |
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910 for (mid = Self->omInUseList; mid != NULL; mid = mid->FreeNext) { |
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911 inusetally ++; |
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912 } |
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913 assert(inusetally == Self->omInUseCount, "inuse count off"); |
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914 |
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915 int freetally = 0; |
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916 for (mid = Self->omFreeList; mid != NULL; mid = mid->FreeNext) { |
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917 freetally ++; |
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918 } |
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919 assert(freetally == Self->omFreeCount, "free count off"); |
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920 } |
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921 */ |
0 | 922 ObjectMonitor * ATTR ObjectSynchronizer::omAlloc (Thread * Self) { |
923 // A large MAXPRIVATE value reduces both list lock contention | |
924 // and list coherency traffic, but also tends to increase the | |
925 // number of objectMonitors in circulation as well as the STW | |
926 // scavenge costs. As usual, we lean toward time in space-time | |
927 // tradeoffs. | |
928 const int MAXPRIVATE = 1024 ; | |
929 for (;;) { | |
930 ObjectMonitor * m ; | |
931 | |
932 // 1: try to allocate from the thread's local omFreeList. | |
933 // Threads will attempt to allocate first from their local list, then | |
934 // from the global list, and only after those attempts fail will the thread | |
935 // attempt to instantiate new monitors. Thread-local free lists take | |
936 // heat off the ListLock and improve allocation latency, as well as reducing | |
937 // coherency traffic on the shared global list. | |
938 m = Self->omFreeList ; | |
939 if (m != NULL) { | |
940 Self->omFreeList = m->FreeNext ; | |
941 Self->omFreeCount -- ; | |
942 // CONSIDER: set m->FreeNext = BAD -- diagnostic hygiene | |
943 guarantee (m->object() == NULL, "invariant") ; | |
1587 | 944 if (MonitorInUseLists) { |
945 m->FreeNext = Self->omInUseList; | |
946 Self->omInUseList = m; | |
947 Self->omInUseCount ++; | |
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948 // verifyInUse(Self); |
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949 } else { |
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950 m->FreeNext = NULL; |
1587 | 951 } |
0 | 952 return m ; |
953 } | |
954 | |
955 // 2: try to allocate from the global gFreeList | |
956 // CONSIDER: use muxTry() instead of muxAcquire(). | |
957 // If the muxTry() fails then drop immediately into case 3. | |
958 // If we're using thread-local free lists then try | |
959 // to reprovision the caller's free list. | |
960 if (gFreeList != NULL) { | |
961 // Reprovision the thread's omFreeList. | |
962 // Use bulk transfers to reduce the allocation rate and heat | |
963 // on various locks. | |
964 Thread::muxAcquire (&ListLock, "omAlloc") ; | |
965 for (int i = Self->omFreeProvision; --i >= 0 && gFreeList != NULL; ) { | |
1587 | 966 MonitorFreeCount --; |
0 | 967 ObjectMonitor * take = gFreeList ; |
968 gFreeList = take->FreeNext ; | |
969 guarantee (take->object() == NULL, "invariant") ; | |
970 guarantee (!take->is_busy(), "invariant") ; | |
971 take->Recycle() ; | |
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972 omRelease (Self, take, false) ; |
0 | 973 } |
974 Thread::muxRelease (&ListLock) ; | |
975 Self->omFreeProvision += 1 + (Self->omFreeProvision/2) ; | |
976 if (Self->omFreeProvision > MAXPRIVATE ) Self->omFreeProvision = MAXPRIVATE ; | |
977 TEVENT (omFirst - reprovision) ; | |
1587 | 978 |
979 const int mx = MonitorBound ; | |
980 if (mx > 0 && (MonitorPopulation-MonitorFreeCount) > mx) { | |
981 // We can't safely induce a STW safepoint from omAlloc() as our thread | |
982 // state may not be appropriate for such activities and callers may hold | |
983 // naked oops, so instead we defer the action. | |
984 InduceScavenge (Self, "omAlloc") ; | |
985 } | |
986 continue; | |
0 | 987 } |
988 | |
989 // 3: allocate a block of new ObjectMonitors | |
990 // Both the local and global free lists are empty -- resort to malloc(). | |
991 // In the current implementation objectMonitors are TSM - immortal. | |
992 assert (_BLOCKSIZE > 1, "invariant") ; | |
993 ObjectMonitor * temp = new ObjectMonitor[_BLOCKSIZE]; | |
994 | |
995 // NOTE: (almost) no way to recover if allocation failed. | |
996 // We might be able to induce a STW safepoint and scavenge enough | |
997 // objectMonitors to permit progress. | |
998 if (temp == NULL) { | |
999 vm_exit_out_of_memory (sizeof (ObjectMonitor[_BLOCKSIZE]), "Allocate ObjectMonitors") ; | |
1000 } | |
1001 | |
1002 // Format the block. | |
1003 // initialize the linked list, each monitor points to its next | |
1004 // forming the single linked free list, the very first monitor | |
1005 // will points to next block, which forms the block list. | |
1006 // The trick of using the 1st element in the block as gBlockList | |
1007 // linkage should be reconsidered. A better implementation would | |
1008 // look like: class Block { Block * next; int N; ObjectMonitor Body [N] ; } | |
1009 | |
1010 for (int i = 1; i < _BLOCKSIZE ; i++) { | |
1011 temp[i].FreeNext = &temp[i+1]; | |
1012 } | |
1013 | |
1014 // terminate the last monitor as the end of list | |
1015 temp[_BLOCKSIZE - 1].FreeNext = NULL ; | |
1016 | |
1017 // Element [0] is reserved for global list linkage | |
1018 temp[0].set_object(CHAINMARKER); | |
1019 | |
1020 // Consider carving out this thread's current request from the | |
1021 // block in hand. This avoids some lock traffic and redundant | |
1022 // list activity. | |
1023 | |
1024 // Acquire the ListLock to manipulate BlockList and FreeList. | |
1025 // An Oyama-Taura-Yonezawa scheme might be more efficient. | |
1026 Thread::muxAcquire (&ListLock, "omAlloc [2]") ; | |
1587 | 1027 MonitorPopulation += _BLOCKSIZE-1; |
1028 MonitorFreeCount += _BLOCKSIZE-1; | |
0 | 1029 |
1030 // Add the new block to the list of extant blocks (gBlockList). | |
1031 // The very first objectMonitor in a block is reserved and dedicated. | |
1032 // It serves as blocklist "next" linkage. | |
1033 temp[0].FreeNext = gBlockList; | |
1034 gBlockList = temp; | |
1035 | |
1036 // Add the new string of objectMonitors to the global free list | |
1037 temp[_BLOCKSIZE - 1].FreeNext = gFreeList ; | |
1038 gFreeList = temp + 1; | |
1039 Thread::muxRelease (&ListLock) ; | |
1040 TEVENT (Allocate block of monitors) ; | |
1041 } | |
1042 } | |
1043 | |
1044 // Place "m" on the caller's private per-thread omFreeList. | |
1045 // In practice there's no need to clamp or limit the number of | |
1046 // monitors on a thread's omFreeList as the only time we'll call | |
1047 // omRelease is to return a monitor to the free list after a CAS | |
1048 // attempt failed. This doesn't allow unbounded #s of monitors to | |
1049 // accumulate on a thread's free list. | |
1050 // | |
1051 | |
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1052 void ObjectSynchronizer::omRelease (Thread * Self, ObjectMonitor * m, bool fromPerThreadAlloc) { |
0 | 1053 guarantee (m->object() == NULL, "invariant") ; |
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1054 |
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1055 // Remove from omInUseList |
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1056 if (MonitorInUseLists && fromPerThreadAlloc) { |
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1057 ObjectMonitor* curmidinuse = NULL; |
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1058 for (ObjectMonitor* mid = Self->omInUseList; mid != NULL; ) { |
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1059 if (m == mid) { |
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1060 // extract from per-thread in-use-list |
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1061 if (mid == Self->omInUseList) { |
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1062 Self->omInUseList = mid->FreeNext; |
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1063 } else if (curmidinuse != NULL) { |
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1064 curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist |
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1065 } |
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1066 Self->omInUseCount --; |
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1067 // verifyInUse(Self); |
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1068 break; |
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1069 } else { |
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1070 curmidinuse = mid; |
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1071 mid = mid->FreeNext; |
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1072 } |
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1073 } |
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1074 } |
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1075 |
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1076 // FreeNext is used for both onInUseList and omFreeList, so clear old before setting new |
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1077 m->FreeNext = Self->omFreeList ; |
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1078 Self->omFreeList = m ; |
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1079 Self->omFreeCount ++ ; |
0 | 1080 } |
1081 | |
1082 // Return the monitors of a moribund thread's local free list to | |
1083 // the global free list. Typically a thread calls omFlush() when | |
1084 // it's dying. We could also consider having the VM thread steal | |
1085 // monitors from threads that have not run java code over a few | |
1086 // consecutive STW safepoints. Relatedly, we might decay | |
1087 // omFreeProvision at STW safepoints. | |
1088 // | |
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1089 // Also return the monitors of a moribund thread"s omInUseList to |
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1090 // a global gOmInUseList under the global list lock so these |
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1091 // will continue to be scanned. |
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1092 // |
0 | 1093 // We currently call omFlush() from the Thread:: dtor _after the thread |
1094 // has been excised from the thread list and is no longer a mutator. | |
1095 // That means that omFlush() can run concurrently with a safepoint and | |
1096 // the scavenge operator. Calling omFlush() from JavaThread::exit() might | |
1097 // be a better choice as we could safely reason that that the JVM is | |
1098 // not at a safepoint at the time of the call, and thus there could | |
1099 // be not inopportune interleavings between omFlush() and the scavenge | |
1100 // operator. | |
1101 | |
1102 void ObjectSynchronizer::omFlush (Thread * Self) { | |
1103 ObjectMonitor * List = Self->omFreeList ; // Null-terminated SLL | |
1104 Self->omFreeList = NULL ; | |
1105 ObjectMonitor * Tail = NULL ; | |
1587 | 1106 int Tally = 0; |
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1107 if (List != NULL) { |
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1108 ObjectMonitor * s ; |
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1109 for (s = List ; s != NULL ; s = s->FreeNext) { |
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1110 Tally ++ ; |
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1111 Tail = s ; |
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1112 guarantee (s->object() == NULL, "invariant") ; |
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1113 guarantee (!s->is_busy(), "invariant") ; |
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1114 s->set_owner (NULL) ; // redundant but good hygiene |
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1115 TEVENT (omFlush - Move one) ; |
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1116 } |
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1117 guarantee (Tail != NULL && List != NULL, "invariant") ; |
0 | 1118 } |
1119 | |
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1120 ObjectMonitor * InUseList = Self->omInUseList; |
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1121 ObjectMonitor * InUseTail = NULL ; |
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1122 int InUseTally = 0; |
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1123 if (InUseList != NULL) { |
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1124 Self->omInUseList = NULL; |
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1125 ObjectMonitor *curom; |
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1126 for (curom = InUseList; curom != NULL; curom = curom->FreeNext) { |
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1127 InUseTail = curom; |
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1128 InUseTally++; |
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1129 } |
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1130 // TODO debug |
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1131 assert(Self->omInUseCount == InUseTally, "inuse count off"); |
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1132 Self->omInUseCount = 0; |
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1133 guarantee (InUseTail != NULL && InUseList != NULL, "invariant"); |
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1134 } |
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1135 |
0 | 1136 Thread::muxAcquire (&ListLock, "omFlush") ; |
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1137 if (Tail != NULL) { |
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1138 Tail->FreeNext = gFreeList ; |
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1139 gFreeList = List ; |
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1140 MonitorFreeCount += Tally; |
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1141 } |
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1142 |
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1143 if (InUseTail != NULL) { |
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1144 InUseTail->FreeNext = gOmInUseList; |
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1145 gOmInUseList = InUseList; |
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1146 gOmInUseCount += InUseTally; |
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1147 } |
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1148 |
0 | 1149 Thread::muxRelease (&ListLock) ; |
1150 TEVENT (omFlush) ; | |
1151 } | |
1152 | |
1153 // Fast path code shared by multiple functions | |
1154 ObjectMonitor* ObjectSynchronizer::inflate_helper(oop obj) { | |
1155 markOop mark = obj->mark(); | |
1156 if (mark->has_monitor()) { | |
1157 assert(ObjectSynchronizer::verify_objmon_isinpool(mark->monitor()), "monitor is invalid"); | |
1158 assert(mark->monitor()->header()->is_neutral(), "monitor must record a good object header"); | |
1159 return mark->monitor(); | |
1160 } | |
1161 return ObjectSynchronizer::inflate(Thread::current(), obj); | |
1162 } | |
1163 | |
1878 | 1164 |
0 | 1165 // Note that we could encounter some performance loss through false-sharing as |
1166 // multiple locks occupy the same $ line. Padding might be appropriate. | |
1167 | |
1168 | |
1169 ObjectMonitor * ATTR ObjectSynchronizer::inflate (Thread * Self, oop object) { | |
1170 // Inflate mutates the heap ... | |
1171 // Relaxing assertion for bug 6320749. | |
1172 assert (Universe::verify_in_progress() || | |
1173 !SafepointSynchronize::is_at_safepoint(), "invariant") ; | |
1174 | |
1175 for (;;) { | |
1176 const markOop mark = object->mark() ; | |
1177 assert (!mark->has_bias_pattern(), "invariant") ; | |
1178 | |
1179 // The mark can be in one of the following states: | |
1180 // * Inflated - just return | |
1181 // * Stack-locked - coerce it to inflated | |
1182 // * INFLATING - busy wait for conversion to complete | |
1183 // * Neutral - aggressively inflate the object. | |
1184 // * BIASED - Illegal. We should never see this | |
1185 | |
1186 // CASE: inflated | |
1187 if (mark->has_monitor()) { | |
1188 ObjectMonitor * inf = mark->monitor() ; | |
1189 assert (inf->header()->is_neutral(), "invariant"); | |
1190 assert (inf->object() == object, "invariant") ; | |
1191 assert (ObjectSynchronizer::verify_objmon_isinpool(inf), "monitor is invalid"); | |
1192 return inf ; | |
1193 } | |
1194 | |
1195 // CASE: inflation in progress - inflating over a stack-lock. | |
1196 // Some other thread is converting from stack-locked to inflated. | |
1197 // Only that thread can complete inflation -- other threads must wait. | |
1198 // The INFLATING value is transient. | |
1199 // Currently, we spin/yield/park and poll the markword, waiting for inflation to finish. | |
1200 // We could always eliminate polling by parking the thread on some auxiliary list. | |
1201 if (mark == markOopDesc::INFLATING()) { | |
1202 TEVENT (Inflate: spin while INFLATING) ; | |
1203 ReadStableMark(object) ; | |
1204 continue ; | |
1205 } | |
1206 | |
1207 // CASE: stack-locked | |
1208 // Could be stack-locked either by this thread or by some other thread. | |
1209 // | |
1210 // Note that we allocate the objectmonitor speculatively, _before_ attempting | |
1211 // to install INFLATING into the mark word. We originally installed INFLATING, | |
1212 // allocated the objectmonitor, and then finally STed the address of the | |
1213 // objectmonitor into the mark. This was correct, but artificially lengthened | |
1214 // the interval in which INFLATED appeared in the mark, thus increasing | |
1215 // the odds of inflation contention. | |
1216 // | |
1217 // We now use per-thread private objectmonitor free lists. | |
1218 // These list are reprovisioned from the global free list outside the | |
1219 // critical INFLATING...ST interval. A thread can transfer | |
1220 // multiple objectmonitors en-mass from the global free list to its local free list. | |
1221 // This reduces coherency traffic and lock contention on the global free list. | |
1222 // Using such local free lists, it doesn't matter if the omAlloc() call appears | |
1223 // before or after the CAS(INFLATING) operation. | |
1224 // See the comments in omAlloc(). | |
1225 | |
1226 if (mark->has_locker()) { | |
1227 ObjectMonitor * m = omAlloc (Self) ; | |
1228 // Optimistically prepare the objectmonitor - anticipate successful CAS | |
1229 // We do this before the CAS in order to minimize the length of time | |
1230 // in which INFLATING appears in the mark. | |
1231 m->Recycle(); | |
1232 m->_Responsible = NULL ; | |
1233 m->OwnerIsThread = 0 ; | |
1234 m->_recursions = 0 ; | |
1878 | 1235 m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ; // Consider: maintain by type/class |
0 | 1236 |
1237 markOop cmp = (markOop) Atomic::cmpxchg_ptr (markOopDesc::INFLATING(), object->mark_addr(), mark) ; | |
1238 if (cmp != mark) { | |
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1239 omRelease (Self, m, true) ; |
0 | 1240 continue ; // Interference -- just retry |
1241 } | |
1242 | |
1243 // We've successfully installed INFLATING (0) into the mark-word. | |
1244 // This is the only case where 0 will appear in a mark-work. | |
1245 // Only the singular thread that successfully swings the mark-word | |
1246 // to 0 can perform (or more precisely, complete) inflation. | |
1247 // | |
1248 // Why do we CAS a 0 into the mark-word instead of just CASing the | |
1249 // mark-word from the stack-locked value directly to the new inflated state? | |
1250 // Consider what happens when a thread unlocks a stack-locked object. | |
1251 // It attempts to use CAS to swing the displaced header value from the | |
1252 // on-stack basiclock back into the object header. Recall also that the | |
1253 // header value (hashcode, etc) can reside in (a) the object header, or | |
1254 // (b) a displaced header associated with the stack-lock, or (c) a displaced | |
1255 // header in an objectMonitor. The inflate() routine must copy the header | |
1256 // value from the basiclock on the owner's stack to the objectMonitor, all | |
1257 // the while preserving the hashCode stability invariants. If the owner | |
1258 // decides to release the lock while the value is 0, the unlock will fail | |
1259 // and control will eventually pass from slow_exit() to inflate. The owner | |
1260 // will then spin, waiting for the 0 value to disappear. Put another way, | |
1261 // the 0 causes the owner to stall if the owner happens to try to | |
1262 // drop the lock (restoring the header from the basiclock to the object) | |
1263 // while inflation is in-progress. This protocol avoids races that might | |
1264 // would otherwise permit hashCode values to change or "flicker" for an object. | |
1265 // Critically, while object->mark is 0 mark->displaced_mark_helper() is stable. | |
1266 // 0 serves as a "BUSY" inflate-in-progress indicator. | |
1267 | |
1268 | |
1269 // fetch the displaced mark from the owner's stack. | |
1270 // The owner can't die or unwind past the lock while our INFLATING | |
1271 // object is in the mark. Furthermore the owner can't complete | |
1272 // an unlock on the object, either. | |
1273 markOop dmw = mark->displaced_mark_helper() ; | |
1274 assert (dmw->is_neutral(), "invariant") ; | |
1275 | |
1276 // Setup monitor fields to proper values -- prepare the monitor | |
1277 m->set_header(dmw) ; | |
1278 | |
1279 // Optimization: if the mark->locker stack address is associated | |
1280 // with this thread we could simply set m->_owner = Self and | |
702
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1281 // m->OwnerIsThread = 1. Note that a thread can inflate an object |
0 | 1282 // that it has stack-locked -- as might happen in wait() -- directly |
1283 // with CAS. That is, we can avoid the xchg-NULL .... ST idiom. | |
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1284 m->set_owner(mark->locker()); |
0 | 1285 m->set_object(object); |
1286 // TODO-FIXME: assert BasicLock->dhw != 0. | |
1287 | |
1288 // Must preserve store ordering. The monitor state must | |
1289 // be stable at the time of publishing the monitor address. | |
1290 guarantee (object->mark() == markOopDesc::INFLATING(), "invariant") ; | |
1291 object->release_set_mark(markOopDesc::encode(m)); | |
1292 | |
1293 // Hopefully the performance counters are allocated on distinct cache lines | |
1294 // to avoid false sharing on MP systems ... | |
1878 | 1295 if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ; |
0 | 1296 TEVENT(Inflate: overwrite stacklock) ; |
1297 if (TraceMonitorInflation) { | |
1298 if (object->is_instance()) { | |
1299 ResourceMark rm; | |
1300 tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
1301 (intptr_t) object, (intptr_t) object->mark(), | |
1302 Klass::cast(object->klass())->external_name()); | |
1303 } | |
1304 } | |
1305 return m ; | |
1306 } | |
1307 | |
1308 // CASE: neutral | |
1309 // TODO-FIXME: for entry we currently inflate and then try to CAS _owner. | |
1310 // If we know we're inflating for entry it's better to inflate by swinging a | |
1311 // pre-locked objectMonitor pointer into the object header. A successful | |
1312 // CAS inflates the object *and* confers ownership to the inflating thread. | |
1313 // In the current implementation we use a 2-step mechanism where we CAS() | |
1314 // to inflate and then CAS() again to try to swing _owner from NULL to Self. | |
1315 // An inflateTry() method that we could call from fast_enter() and slow_enter() | |
1316 // would be useful. | |
1317 | |
1318 assert (mark->is_neutral(), "invariant"); | |
1319 ObjectMonitor * m = omAlloc (Self) ; | |
1320 // prepare m for installation - set monitor to initial state | |
1321 m->Recycle(); | |
1322 m->set_header(mark); | |
1323 m->set_owner(NULL); | |
1324 m->set_object(object); | |
1325 m->OwnerIsThread = 1 ; | |
1326 m->_recursions = 0 ; | |
1327 m->_Responsible = NULL ; | |
1878 | 1328 m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ; // consider: keep metastats by type/class |
0 | 1329 |
1330 if (Atomic::cmpxchg_ptr (markOopDesc::encode(m), object->mark_addr(), mark) != mark) { | |
1331 m->set_object (NULL) ; | |
1332 m->set_owner (NULL) ; | |
1333 m->OwnerIsThread = 0 ; | |
1334 m->Recycle() ; | |
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1335 omRelease (Self, m, true) ; |
0 | 1336 m = NULL ; |
1337 continue ; | |
1338 // interference - the markword changed - just retry. | |
1339 // The state-transitions are one-way, so there's no chance of | |
1340 // live-lock -- "Inflated" is an absorbing state. | |
1341 } | |
1342 | |
1343 // Hopefully the performance counters are allocated on distinct | |
1344 // cache lines to avoid false sharing on MP systems ... | |
1878 | 1345 if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ; |
0 | 1346 TEVENT(Inflate: overwrite neutral) ; |
1347 if (TraceMonitorInflation) { | |
1348 if (object->is_instance()) { | |
1349 ResourceMark rm; | |
1350 tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
1351 (intptr_t) object, (intptr_t) object->mark(), | |
1352 Klass::cast(object->klass())->external_name()); | |
1353 } | |
1354 } | |
1355 return m ; | |
1356 } | |
1357 } | |
1358 | |
1878 | 1359 // Note that we could encounter some performance loss through false-sharing as |
1360 // multiple locks occupy the same $ line. Padding might be appropriate. | |
0 | 1361 |
1362 | |
1363 // Deflate_idle_monitors() is called at all safepoints, immediately | |
1364 // after all mutators are stopped, but before any objects have moved. | |
1365 // It traverses the list of known monitors, deflating where possible. | |
1366 // The scavenged monitor are returned to the monitor free list. | |
1367 // | |
1368 // Beware that we scavenge at *every* stop-the-world point. | |
1369 // Having a large number of monitors in-circulation negatively | |
1370 // impacts the performance of some applications (e.g., PointBase). | |
1371 // Broadly, we want to minimize the # of monitors in circulation. | |
1587 | 1372 // |
1373 // We have added a flag, MonitorInUseLists, which creates a list | |
1374 // of active monitors for each thread. deflate_idle_monitors() | |
1375 // only scans the per-thread inuse lists. omAlloc() puts all | |
1376 // assigned monitors on the per-thread list. deflate_idle_monitors() | |
1377 // returns the non-busy monitors to the global free list. | |
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1378 // When a thread dies, omFlush() adds the list of active monitors for |
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1379 // that thread to a global gOmInUseList acquiring the |
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1380 // global list lock. deflate_idle_monitors() acquires the global |
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1381 // list lock to scan for non-busy monitors to the global free list. |
1587 | 1382 // An alternative could have used a single global inuse list. The |
1383 // downside would have been the additional cost of acquiring the global list lock | |
1384 // for every omAlloc(). | |
0 | 1385 // |
1386 // Perversely, the heap size -- and thus the STW safepoint rate -- | |
1387 // typically drives the scavenge rate. Large heaps can mean infrequent GC, | |
1388 // which in turn can mean large(r) numbers of objectmonitors in circulation. | |
1389 // This is an unfortunate aspect of this design. | |
1390 // | |
1391 | |
1878 | 1392 enum ManifestConstants { |
1393 ClearResponsibleAtSTW = 0, | |
1394 MaximumRecheckInterval = 1000 | |
1395 } ; | |
1587 | 1396 |
1397 // Deflate a single monitor if not in use | |
1398 // Return true if deflated, false if in use | |
1399 bool ObjectSynchronizer::deflate_monitor(ObjectMonitor* mid, oop obj, | |
1400 ObjectMonitor** FreeHeadp, ObjectMonitor** FreeTailp) { | |
1401 bool deflated; | |
1402 // Normal case ... The monitor is associated with obj. | |
1403 guarantee (obj->mark() == markOopDesc::encode(mid), "invariant") ; | |
1404 guarantee (mid == obj->mark()->monitor(), "invariant"); | |
1405 guarantee (mid->header()->is_neutral(), "invariant"); | |
1406 | |
1407 if (mid->is_busy()) { | |
1408 if (ClearResponsibleAtSTW) mid->_Responsible = NULL ; | |
1409 deflated = false; | |
1410 } else { | |
1411 // Deflate the monitor if it is no longer being used | |
1412 // It's idle - scavenge and return to the global free list | |
1413 // plain old deflation ... | |
1414 TEVENT (deflate_idle_monitors - scavenge1) ; | |
1415 if (TraceMonitorInflation) { | |
1416 if (obj->is_instance()) { | |
1417 ResourceMark rm; | |
1418 tty->print_cr("Deflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
1419 (intptr_t) obj, (intptr_t) obj->mark(), Klass::cast(obj->klass())->external_name()); | |
1420 } | |
1421 } | |
1422 | |
1423 // Restore the header back to obj | |
1424 obj->release_set_mark(mid->header()); | |
1425 mid->clear(); | |
1426 | |
1427 assert (mid->object() == NULL, "invariant") ; | |
1428 | |
1429 // Move the object to the working free list defined by FreeHead,FreeTail. | |
1430 if (*FreeHeadp == NULL) *FreeHeadp = mid; | |
1431 if (*FreeTailp != NULL) { | |
1432 ObjectMonitor * prevtail = *FreeTailp; | |
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1433 assert(prevtail->FreeNext == NULL, "cleaned up deflated?"); // TODO KK |
1587 | 1434 prevtail->FreeNext = mid; |
1435 } | |
1436 *FreeTailp = mid; | |
1437 deflated = true; | |
1438 } | |
1439 return deflated; | |
1440 } | |
1441 | |
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1442 // Caller acquires ListLock |
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1443 int ObjectSynchronizer::walk_monitor_list(ObjectMonitor** listheadp, |
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1444 ObjectMonitor** FreeHeadp, ObjectMonitor** FreeTailp) { |
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1445 ObjectMonitor* mid; |
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1446 ObjectMonitor* next; |
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1447 ObjectMonitor* curmidinuse = NULL; |
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1448 int deflatedcount = 0; |
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1449 |
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1450 for (mid = *listheadp; mid != NULL; ) { |
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1451 oop obj = (oop) mid->object(); |
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1452 bool deflated = false; |
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1453 if (obj != NULL) { |
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1454 deflated = deflate_monitor(mid, obj, FreeHeadp, FreeTailp); |
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1455 } |
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1456 if (deflated) { |
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1457 // extract from per-thread in-use-list |
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1458 if (mid == *listheadp) { |
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1459 *listheadp = mid->FreeNext; |
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1460 } else if (curmidinuse != NULL) { |
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1461 curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist |
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1462 } |
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1463 next = mid->FreeNext; |
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1464 mid->FreeNext = NULL; // This mid is current tail in the FreeHead list |
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1465 mid = next; |
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1466 deflatedcount++; |
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1467 } else { |
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1468 curmidinuse = mid; |
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1469 mid = mid->FreeNext; |
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1470 } |
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1471 } |
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1472 return deflatedcount; |
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1473 } |
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1474 |
0 | 1475 void ObjectSynchronizer::deflate_idle_monitors() { |
1476 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); | |
1477 int nInuse = 0 ; // currently associated with objects | |
1478 int nInCirculation = 0 ; // extant | |
1479 int nScavenged = 0 ; // reclaimed | |
1587 | 1480 bool deflated = false; |
0 | 1481 |
1482 ObjectMonitor * FreeHead = NULL ; // Local SLL of scavenged monitors | |
1483 ObjectMonitor * FreeTail = NULL ; | |
1484 | |
1587 | 1485 TEVENT (deflate_idle_monitors) ; |
1486 // Prevent omFlush from changing mids in Thread dtor's during deflation | |
1487 // And in case the vm thread is acquiring a lock during a safepoint | |
1488 // See e.g. 6320749 | |
1489 Thread::muxAcquire (&ListLock, "scavenge - return") ; | |
1490 | |
1491 if (MonitorInUseLists) { | |
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1492 int inUse = 0; |
1587 | 1493 for (JavaThread* cur = Threads::first(); cur != NULL; cur = cur->next()) { |
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1494 nInCirculation+= cur->omInUseCount; |
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1495 int deflatedcount = walk_monitor_list(cur->omInUseList_addr(), &FreeHead, &FreeTail); |
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1496 cur->omInUseCount-= deflatedcount; |
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1497 // verifyInUse(cur); |
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1498 nScavenged += deflatedcount; |
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1499 nInuse += cur->omInUseCount; |
1587 | 1500 } |
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1501 |
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1502 // For moribund threads, scan gOmInUseList |
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1503 if (gOmInUseList) { |
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1504 nInCirculation += gOmInUseCount; |
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1505 int deflatedcount = walk_monitor_list((ObjectMonitor **)&gOmInUseList, &FreeHead, &FreeTail); |
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1506 gOmInUseCount-= deflatedcount; |
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1507 nScavenged += deflatedcount; |
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1508 nInuse += gOmInUseCount; |
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1509 } |
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1510 |
1587 | 1511 } else for (ObjectMonitor* block = gBlockList; block != NULL; block = next(block)) { |
0 | 1512 // Iterate over all extant monitors - Scavenge all idle monitors. |
1513 assert(block->object() == CHAINMARKER, "must be a block header"); | |
1514 nInCirculation += _BLOCKSIZE ; | |
1515 for (int i = 1 ; i < _BLOCKSIZE; i++) { | |
1516 ObjectMonitor* mid = &block[i]; | |
1517 oop obj = (oop) mid->object(); | |
1518 | |
1519 if (obj == NULL) { | |
1520 // The monitor is not associated with an object. | |
1521 // The monitor should either be a thread-specific private | |
1522 // free list or the global free list. | |
1523 // obj == NULL IMPLIES mid->is_busy() == 0 | |
1524 guarantee (!mid->is_busy(), "invariant") ; | |
1525 continue ; | |
1526 } | |
1587 | 1527 deflated = deflate_monitor(mid, obj, &FreeHead, &FreeTail); |
1528 | |
1529 if (deflated) { | |
1530 mid->FreeNext = NULL ; | |
1531 nScavenged ++ ; | |
0 | 1532 } else { |
1587 | 1533 nInuse ++; |
0 | 1534 } |
1535 } | |
1536 } | |
1537 | |
1587 | 1538 MonitorFreeCount += nScavenged; |
1539 | |
1540 // Consider: audit gFreeList to ensure that MonitorFreeCount and list agree. | |
1541 | |
1878 | 1542 if (ObjectMonitor::Knob_Verbose) { |
1587 | 1543 ::printf ("Deflate: InCirc=%d InUse=%d Scavenged=%d ForceMonitorScavenge=%d : pop=%d free=%d\n", |
1544 nInCirculation, nInuse, nScavenged, ForceMonitorScavenge, | |
1545 MonitorPopulation, MonitorFreeCount) ; | |
1546 ::fflush(stdout) ; | |
1547 } | |
1548 | |
1549 ForceMonitorScavenge = 0; // Reset | |
1550 | |
0 | 1551 // Move the scavenged monitors back to the global free list. |
1552 if (FreeHead != NULL) { | |
1553 guarantee (FreeTail != NULL && nScavenged > 0, "invariant") ; | |
1554 assert (FreeTail->FreeNext == NULL, "invariant") ; | |
1555 // constant-time list splice - prepend scavenged segment to gFreeList | |
1556 FreeTail->FreeNext = gFreeList ; | |
1557 gFreeList = FreeHead ; | |
1558 } | |
1587 | 1559 Thread::muxRelease (&ListLock) ; |
0 | 1560 |
1878 | 1561 if (ObjectMonitor::_sync_Deflations != NULL) ObjectMonitor::_sync_Deflations->inc(nScavenged) ; |
1562 if (ObjectMonitor::_sync_MonExtant != NULL) ObjectMonitor::_sync_MonExtant ->set_value(nInCirculation); | |
0 | 1563 |
1564 // TODO: Add objectMonitor leak detection. | |
1565 // Audit/inventory the objectMonitors -- make sure they're all accounted for. | |
1566 GVars.stwRandom = os::random() ; | |
1567 GVars.stwCycle ++ ; | |
1568 } | |
1569 | |
1878 | 1570 // Monitor cleanup on JavaThread::exit |
0 | 1571 |
1878 | 1572 // Iterate through monitor cache and attempt to release thread's monitors |
1573 // Gives up on a particular monitor if an exception occurs, but continues | |
1574 // the overall iteration, swallowing the exception. | |
1575 class ReleaseJavaMonitorsClosure: public MonitorClosure { | |
1576 private: | |
1577 TRAPS; | |
0 | 1578 |
1878 | 1579 public: |
1580 ReleaseJavaMonitorsClosure(Thread* thread) : THREAD(thread) {} | |
1581 void do_monitor(ObjectMonitor* mid) { | |
1582 if (mid->owner() == THREAD) { | |
1583 (void)mid->complete_exit(CHECK); | |
0 | 1584 } |
1585 } | |
1878 | 1586 }; |
0 | 1587 |
1878 | 1588 // Release all inflated monitors owned by THREAD. Lightweight monitors are |
1589 // ignored. This is meant to be called during JNI thread detach which assumes | |
1590 // all remaining monitors are heavyweight. All exceptions are swallowed. | |
1591 // Scanning the extant monitor list can be time consuming. | |
1592 // A simple optimization is to add a per-thread flag that indicates a thread | |
1593 // called jni_monitorenter() during its lifetime. | |
0 | 1594 // |
1878 | 1595 // Instead of No_Savepoint_Verifier it might be cheaper to |
1596 // use an idiom of the form: | |
1597 // auto int tmp = SafepointSynchronize::_safepoint_counter ; | |
1598 // <code that must not run at safepoint> | |
1599 // guarantee (((tmp ^ _safepoint_counter) | (tmp & 1)) == 0) ; | |
1600 // Since the tests are extremely cheap we could leave them enabled | |
1601 // for normal product builds. | |
0 | 1602 |
1878 | 1603 void ObjectSynchronizer::release_monitors_owned_by_thread(TRAPS) { |
1604 assert(THREAD == JavaThread::current(), "must be current Java thread"); | |
1605 No_Safepoint_Verifier nsv ; | |
1606 ReleaseJavaMonitorsClosure rjmc(THREAD); | |
1607 Thread::muxAcquire(&ListLock, "release_monitors_owned_by_thread"); | |
1608 ObjectSynchronizer::monitors_iterate(&rjmc); | |
1609 Thread::muxRelease(&ListLock); | |
1610 THREAD->clear_pending_exception(); | |
0 | 1611 } |
1612 | |
1613 //------------------------------------------------------------------------------ | |
1614 // Non-product code | |
1615 | |
1616 #ifndef PRODUCT | |
1617 | |
1618 void ObjectSynchronizer::trace_locking(Handle locking_obj, bool is_compiled, | |
1619 bool is_method, bool is_locking) { | |
1620 // Don't know what to do here | |
1621 } | |
1622 | |
1623 // Verify all monitors in the monitor cache, the verification is weak. | |
1624 void ObjectSynchronizer::verify() { | |
1625 ObjectMonitor* block = gBlockList; | |
1626 ObjectMonitor* mid; | |
1627 while (block) { | |
1628 assert(block->object() == CHAINMARKER, "must be a block header"); | |
1629 for (int i = 1; i < _BLOCKSIZE; i++) { | |
1630 mid = block + i; | |
1631 oop object = (oop) mid->object(); | |
1632 if (object != NULL) { | |
1633 mid->verify(); | |
1634 } | |
1635 } | |
1636 block = (ObjectMonitor*) block->FreeNext; | |
1637 } | |
1638 } | |
1639 | |
1640 // Check if monitor belongs to the monitor cache | |
1641 // The list is grow-only so it's *relatively* safe to traverse | |
1642 // the list of extant blocks without taking a lock. | |
1643 | |
1644 int ObjectSynchronizer::verify_objmon_isinpool(ObjectMonitor *monitor) { | |
1645 ObjectMonitor* block = gBlockList; | |
1646 | |
1647 while (block) { | |
1648 assert(block->object() == CHAINMARKER, "must be a block header"); | |
1649 if (monitor > &block[0] && monitor < &block[_BLOCKSIZE]) { | |
1650 address mon = (address) monitor; | |
1651 address blk = (address) block; | |
1652 size_t diff = mon - blk; | |
1653 assert((diff % sizeof(ObjectMonitor)) == 0, "check"); | |
1654 return 1; | |
1655 } | |
1656 block = (ObjectMonitor*) block->FreeNext; | |
1657 } | |
1658 return 0; | |
1659 } | |
1660 | |
1661 #endif |