Mercurial > hg > truffle
annotate src/share/vm/runtime/synchronizer.cpp @ 3714:b648304ba4ff
Change Graal monitor enter and exit from BasicObjectLock to BasicLock
author | Christian Wimmer <christian.wimmer@oracle.com> |
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date | Tue, 13 Dec 2011 21:17:46 -0800 |
parents | 0654ee04b214 |
children | 04b9a2566eec |
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 | |
0 | 54 |
55 #if defined(__GNUC__) && !defined(IA64) | |
56 // Need to inhibit inlining for older versions of GCC to avoid build-time failures | |
57 #define ATTR __attribute__((noinline)) | |
58 #else | |
59 #define ATTR | |
60 #endif | |
61 | |
62 // The "core" versions of monitor enter and exit reside in this file. | |
63 // The interpreter and compilers contain specialized transliterated | |
64 // variants of the enter-exit fast-path operations. See i486.ad fast_lock(), | |
65 // for instance. If you make changes here, make sure to modify the | |
66 // interpreter, and both C1 and C2 fast-path inline locking code emission. | |
67 // | |
68 // | |
69 // ----------------------------------------------------------------------------- | |
70 | |
71 #ifdef DTRACE_ENABLED | |
72 | |
73 // Only bother with this argument setup if dtrace is available | |
74 // TODO-FIXME: probes should not fire when caller is _blocked. assert() accordingly. | |
75 | |
76 HS_DTRACE_PROBE_DECL5(hotspot, monitor__wait, | |
77 jlong, uintptr_t, char*, int, long); | |
78 HS_DTRACE_PROBE_DECL4(hotspot, monitor__waited, | |
79 jlong, uintptr_t, char*, int); | |
80 | |
81 #define DTRACE_MONITOR_PROBE_COMMON(klassOop, thread) \ | |
82 char* bytes = NULL; \ | |
83 int len = 0; \ | |
84 jlong jtid = SharedRuntime::get_java_tid(thread); \ | |
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85 Symbol* klassname = ((oop)(klassOop))->klass()->klass_part()->name(); \ |
0 | 86 if (klassname != NULL) { \ |
87 bytes = (char*)klassname->bytes(); \ | |
88 len = klassname->utf8_length(); \ | |
89 } | |
90 | |
91 #define DTRACE_MONITOR_WAIT_PROBE(monitor, klassOop, thread, millis) \ | |
92 { \ | |
93 if (DTraceMonitorProbes) { \ | |
94 DTRACE_MONITOR_PROBE_COMMON(klassOop, thread); \ | |
95 HS_DTRACE_PROBE5(hotspot, monitor__wait, jtid, \ | |
96 (monitor), bytes, len, (millis)); \ | |
97 } \ | |
98 } | |
99 | |
100 #define DTRACE_MONITOR_PROBE(probe, monitor, klassOop, thread) \ | |
101 { \ | |
102 if (DTraceMonitorProbes) { \ | |
103 DTRACE_MONITOR_PROBE_COMMON(klassOop, thread); \ | |
104 HS_DTRACE_PROBE4(hotspot, monitor__##probe, jtid, \ | |
105 (uintptr_t)(monitor), bytes, len); \ | |
106 } \ | |
107 } | |
108 | |
109 #else // ndef DTRACE_ENABLED | |
110 | |
111 #define DTRACE_MONITOR_WAIT_PROBE(klassOop, thread, millis, mon) {;} | |
112 #define DTRACE_MONITOR_PROBE(probe, klassOop, thread, mon) {;} | |
113 | |
114 #endif // ndef DTRACE_ENABLED | |
115 | |
1878 | 116 // This exists only as a workaround of dtrace bug 6254741 |
117 int dtrace_waited_probe(ObjectMonitor* monitor, Handle obj, Thread* thr) { | |
118 DTRACE_MONITOR_PROBE(waited, monitor, obj(), thr); | |
119 return 0; | |
120 } | |
121 | |
122 #define NINFLATIONLOCKS 256 | |
123 static volatile intptr_t InflationLocks [NINFLATIONLOCKS] ; | |
124 | |
125 ObjectMonitor * ObjectSynchronizer::gBlockList = NULL ; | |
126 ObjectMonitor * volatile ObjectSynchronizer::gFreeList = NULL ; | |
127 ObjectMonitor * volatile ObjectSynchronizer::gOmInUseList = NULL ; | |
128 int ObjectSynchronizer::gOmInUseCount = 0; | |
129 static volatile intptr_t ListLock = 0 ; // protects global monitor free-list cache | |
130 static volatile int MonitorFreeCount = 0 ; // # on gFreeList | |
131 static volatile int MonitorPopulation = 0 ; // # Extant -- in circulation | |
132 #define CHAINMARKER ((oop)-1) | |
133 | |
134 // ----------------------------------------------------------------------------- | |
135 // Fast Monitor Enter/Exit | |
136 // This the fast monitor enter. The interpreter and compiler use | |
137 // some assembly copies of this code. Make sure update those code | |
138 // if the following function is changed. The implementation is | |
139 // extremely sensitive to race condition. Be careful. | |
140 | |
141 void ObjectSynchronizer::fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias, TRAPS) { | |
142 if (UseBiasedLocking) { | |
143 if (!SafepointSynchronize::is_at_safepoint()) { | |
144 BiasedLocking::Condition cond = BiasedLocking::revoke_and_rebias(obj, attempt_rebias, THREAD); | |
145 if (cond == BiasedLocking::BIAS_REVOKED_AND_REBIASED) { | |
146 return; | |
147 } | |
148 } else { | |
149 assert(!attempt_rebias, "can not rebias toward VM thread"); | |
150 BiasedLocking::revoke_at_safepoint(obj); | |
151 } | |
152 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
153 } | |
154 | |
155 slow_enter (obj, lock, THREAD) ; | |
156 } | |
157 | |
158 void ObjectSynchronizer::fast_exit(oop object, BasicLock* lock, TRAPS) { | |
159 assert(!object->mark()->has_bias_pattern(), "should not see bias pattern here"); | |
160 // if displaced header is null, the previous enter is recursive enter, no-op | |
161 markOop dhw = lock->displaced_header(); | |
162 markOop mark ; | |
163 if (dhw == NULL) { | |
164 // Recursive stack-lock. | |
165 // Diagnostics -- Could be: stack-locked, inflating, inflated. | |
166 mark = object->mark() ; | |
167 assert (!mark->is_neutral(), "invariant") ; | |
168 if (mark->has_locker() && mark != markOopDesc::INFLATING()) { | |
169 assert(THREAD->is_lock_owned((address)mark->locker()), "invariant") ; | |
170 } | |
171 if (mark->has_monitor()) { | |
172 ObjectMonitor * m = mark->monitor() ; | |
173 assert(((oop)(m->object()))->mark() == mark, "invariant") ; | |
174 assert(m->is_entered(THREAD), "invariant") ; | |
175 } | |
176 return ; | |
177 } | |
178 | |
179 mark = object->mark() ; | |
0 | 180 |
1878 | 181 // If the object is stack-locked by the current thread, try to |
182 // swing the displaced header from the box back to the mark. | |
183 if (mark == (markOop) lock) { | |
184 assert (dhw->is_neutral(), "invariant") ; | |
185 if ((markOop) Atomic::cmpxchg_ptr (dhw, object->mark_addr(), mark) == mark) { | |
186 TEVENT (fast_exit: release stacklock) ; | |
187 return; | |
188 } | |
189 } | |
190 | |
191 ObjectSynchronizer::inflate(THREAD, object)->exit (THREAD) ; | |
192 } | |
193 | |
194 // ----------------------------------------------------------------------------- | |
195 // Interpreter/Compiler Slow Case | |
196 // This routine is used to handle interpreter/compiler slow case | |
197 // We don't need to use fast path here, because it must have been | |
198 // failed in the interpreter/compiler code. | |
199 void ObjectSynchronizer::slow_enter(Handle obj, BasicLock* lock, TRAPS) { | |
200 markOop mark = obj->mark(); | |
201 assert(!mark->has_bias_pattern(), "should not see bias pattern here"); | |
202 | |
203 if (mark->is_neutral()) { | |
204 // Anticipate successful CAS -- the ST of the displaced mark must | |
205 // be visible <= the ST performed by the CAS. | |
206 lock->set_displaced_header(mark); | |
207 if (mark == (markOop) Atomic::cmpxchg_ptr(lock, obj()->mark_addr(), mark)) { | |
208 TEVENT (slow_enter: release stacklock) ; | |
209 return ; | |
210 } | |
211 // Fall through to inflate() ... | |
212 } else | |
213 if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { | |
214 assert(lock != mark->locker(), "must not re-lock the same lock"); | |
215 assert(lock != (BasicLock*)obj->mark(), "don't relock with same BasicLock"); | |
216 lock->set_displaced_header(NULL); | |
217 return; | |
218 } | |
219 | |
220 #if 0 | |
221 // The following optimization isn't particularly useful. | |
222 if (mark->has_monitor() && mark->monitor()->is_entered(THREAD)) { | |
223 lock->set_displaced_header (NULL) ; | |
224 return ; | |
225 } | |
226 #endif | |
227 | |
228 // The object header will never be displaced to this lock, | |
229 // so it does not matter what the value is, except that it | |
230 // must be non-zero to avoid looking like a re-entrant lock, | |
231 // and must not look locked either. | |
232 lock->set_displaced_header(markOopDesc::unused_mark()); | |
233 ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD); | |
234 } | |
235 | |
236 // This routine is used to handle interpreter/compiler slow case | |
237 // We don't need to use fast path here, because it must have | |
238 // failed in the interpreter/compiler code. Simply use the heavy | |
239 // weight monitor should be ok, unless someone find otherwise. | |
240 void ObjectSynchronizer::slow_exit(oop object, BasicLock* lock, TRAPS) { | |
241 fast_exit (object, lock, THREAD) ; | |
242 } | |
243 | |
244 // ----------------------------------------------------------------------------- | |
245 // Class Loader support to workaround deadlocks on the class loader lock objects | |
246 // Also used by GC | |
247 // complete_exit()/reenter() are used to wait on a nested lock | |
248 // i.e. to give up an outer lock completely and then re-enter | |
249 // Used when holding nested locks - lock acquisition order: lock1 then lock2 | |
250 // 1) complete_exit lock1 - saving recursion count | |
251 // 2) wait on lock2 | |
252 // 3) when notified on lock2, unlock lock2 | |
253 // 4) reenter lock1 with original recursion count | |
254 // 5) lock lock2 | |
255 // NOTE: must use heavy weight monitor to handle complete_exit/reenter() | |
256 intptr_t ObjectSynchronizer::complete_exit(Handle obj, TRAPS) { | |
257 TEVENT (complete_exit) ; | |
258 if (UseBiasedLocking) { | |
259 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
260 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
0 | 261 } |
262 | |
1878 | 263 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); |
264 | |
265 return monitor->complete_exit(THREAD); | |
266 } | |
267 | |
268 // NOTE: must use heavy weight monitor to handle complete_exit/reenter() | |
269 void ObjectSynchronizer::reenter(Handle obj, intptr_t recursion, TRAPS) { | |
270 TEVENT (reenter) ; | |
271 if (UseBiasedLocking) { | |
272 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
273 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
274 } | |
275 | |
276 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); | |
277 | |
278 monitor->reenter(recursion, THREAD); | |
279 } | |
280 // ----------------------------------------------------------------------------- | |
281 // JNI locks on java objects | |
282 // NOTE: must use heavy weight monitor to handle jni monitor enter | |
283 void ObjectSynchronizer::jni_enter(Handle obj, TRAPS) { // possible entry from jni enter | |
284 // the current locking is from JNI instead of Java code | |
285 TEVENT (jni_enter) ; | |
286 if (UseBiasedLocking) { | |
287 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
288 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
289 } | |
290 THREAD->set_current_pending_monitor_is_from_java(false); | |
291 ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD); | |
292 THREAD->set_current_pending_monitor_is_from_java(true); | |
293 } | |
294 | |
295 // NOTE: must use heavy weight monitor to handle jni monitor enter | |
296 bool ObjectSynchronizer::jni_try_enter(Handle obj, Thread* THREAD) { | |
297 if (UseBiasedLocking) { | |
298 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
299 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
0 | 300 } |
301 | |
1878 | 302 ObjectMonitor* monitor = ObjectSynchronizer::inflate_helper(obj()); |
303 return monitor->try_enter(THREAD); | |
304 } | |
305 | |
306 | |
307 // NOTE: must use heavy weight monitor to handle jni monitor exit | |
308 void ObjectSynchronizer::jni_exit(oop obj, Thread* THREAD) { | |
309 TEVENT (jni_exit) ; | |
310 if (UseBiasedLocking) { | |
311 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
312 } | |
313 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
314 | |
315 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj); | |
316 // If this thread has locked the object, exit the monitor. Note: can't use | |
317 // monitor->check(CHECK); must exit even if an exception is pending. | |
318 if (monitor->check(THREAD)) { | |
319 monitor->exit(THREAD); | |
0 | 320 } |
1878 | 321 } |
322 | |
323 // ----------------------------------------------------------------------------- | |
324 // Internal VM locks on java objects | |
325 // standard constructor, allows locking failures | |
326 ObjectLocker::ObjectLocker(Handle obj, Thread* thread, bool doLock) { | |
327 _dolock = doLock; | |
328 _thread = thread; | |
329 debug_only(if (StrictSafepointChecks) _thread->check_for_valid_safepoint_state(false);) | |
330 _obj = obj; | |
0 | 331 |
1878 | 332 if (_dolock) { |
333 TEVENT (ObjectLocker) ; | |
334 | |
335 ObjectSynchronizer::fast_enter(_obj, &_lock, false, _thread); | |
336 } | |
337 } | |
338 | |
339 ObjectLocker::~ObjectLocker() { | |
340 if (_dolock) { | |
341 ObjectSynchronizer::fast_exit(_obj(), &_lock, _thread); | |
342 } | |
343 } | |
0 | 344 |
345 | |
1878 | 346 // ----------------------------------------------------------------------------- |
347 // Wait/Notify/NotifyAll | |
348 // NOTE: must use heavy weight monitor to handle wait() | |
349 void ObjectSynchronizer::wait(Handle obj, jlong millis, TRAPS) { | |
350 if (UseBiasedLocking) { | |
351 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
352 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
353 } | |
354 if (millis < 0) { | |
355 TEVENT (wait - throw IAX) ; | |
356 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); | |
357 } | |
358 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); | |
359 DTRACE_MONITOR_WAIT_PROBE(monitor, obj(), THREAD, millis); | |
360 monitor->wait(millis, true, THREAD); | |
361 | |
362 /* This dummy call is in place to get around dtrace bug 6254741. Once | |
363 that's fixed we can uncomment the following line and remove the call */ | |
364 // DTRACE_MONITOR_PROBE(waited, monitor, obj(), THREAD); | |
365 dtrace_waited_probe(monitor, obj, THREAD); | |
366 } | |
0 | 367 |
1878 | 368 void ObjectSynchronizer::waitUninterruptibly (Handle obj, jlong millis, TRAPS) { |
369 if (UseBiasedLocking) { | |
370 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
371 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
372 } | |
373 if (millis < 0) { | |
374 TEVENT (wait - throw IAX) ; | |
375 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); | |
376 } | |
377 ObjectSynchronizer::inflate(THREAD, obj()) -> wait(millis, false, THREAD) ; | |
378 } | |
379 | |
380 void ObjectSynchronizer::notify(Handle obj, TRAPS) { | |
381 if (UseBiasedLocking) { | |
382 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
383 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
384 } | |
0 | 385 |
1878 | 386 markOop mark = obj->mark(); |
387 if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { | |
388 return; | |
389 } | |
390 ObjectSynchronizer::inflate(THREAD, obj())->notify(THREAD); | |
391 } | |
0 | 392 |
1878 | 393 // NOTE: see comment of notify() |
394 void ObjectSynchronizer::notifyall(Handle obj, TRAPS) { | |
395 if (UseBiasedLocking) { | |
396 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
397 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
398 } | |
399 | |
400 markOop mark = obj->mark(); | |
401 if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { | |
402 return; | |
403 } | |
404 ObjectSynchronizer::inflate(THREAD, obj())->notifyAll(THREAD); | |
405 } | |
406 | |
407 // ----------------------------------------------------------------------------- | |
408 // Hash Code handling | |
409 // | |
0 | 410 // Performance concern: |
411 // OrderAccess::storestore() calls release() which STs 0 into the global volatile | |
412 // OrderAccess::Dummy variable. This store is unnecessary for correctness. | |
413 // Many threads STing into a common location causes considerable cache migration | |
414 // or "sloshing" on large SMP system. As such, I avoid using OrderAccess::storestore() | |
415 // until it's repaired. In some cases OrderAccess::fence() -- which incurs local | |
416 // latency on the executing processor -- is a better choice as it scales on SMP | |
417 // systems. See http://blogs.sun.com/dave/entry/biased_locking_in_hotspot for a | |
418 // discussion of coherency costs. Note that all our current reference platforms | |
419 // provide strong ST-ST order, so the issue is moot on IA32, x64, and SPARC. | |
420 // | |
421 // As a general policy we use "volatile" to control compiler-based reordering | |
422 // and explicit fences (barriers) to control for architectural reordering performed | |
423 // by the CPU(s) or platform. | |
424 | |
425 static int MBFence (int x) { OrderAccess::fence(); return x; } | |
426 | |
427 struct SharedGlobals { | |
428 // These are highly shared mostly-read variables. | |
429 // To avoid false-sharing they need to be the sole occupants of a $ line. | |
430 double padPrefix [8]; | |
431 volatile int stwRandom ; | |
432 volatile int stwCycle ; | |
433 | |
434 // Hot RW variables -- Sequester to avoid false-sharing | |
435 double padSuffix [16]; | |
436 volatile int hcSequence ; | |
437 double padFinal [8] ; | |
438 } ; | |
439 | |
440 static SharedGlobals GVars ; | |
1587 | 441 static int MonitorScavengeThreshold = 1000000 ; |
442 static volatile int ForceMonitorScavenge = 0 ; // Scavenge required and pending | |
0 | 443 |
1878 | 444 static markOop ReadStableMark (oop obj) { |
445 markOop mark = obj->mark() ; | |
446 if (!mark->is_being_inflated()) { | |
447 return mark ; // normal fast-path return | |
448 } | |
0 | 449 |
1878 | 450 int its = 0 ; |
451 for (;;) { | |
452 markOop mark = obj->mark() ; | |
453 if (!mark->is_being_inflated()) { | |
454 return mark ; // normal fast-path return | |
455 } | |
456 | |
457 // The object is being inflated by some other thread. | |
458 // The caller of ReadStableMark() must wait for inflation to complete. | |
459 // Avoid live-lock | |
460 // TODO: consider calling SafepointSynchronize::do_call_back() while | |
461 // spinning to see if there's a safepoint pending. If so, immediately | |
462 // yielding or blocking would be appropriate. Avoid spinning while | |
463 // there is a safepoint pending. | |
464 // TODO: add inflation contention performance counters. | |
465 // TODO: restrict the aggregate number of spinners. | |
0 | 466 |
1878 | 467 ++its ; |
468 if (its > 10000 || !os::is_MP()) { | |
469 if (its & 1) { | |
470 os::NakedYield() ; | |
471 TEVENT (Inflate: INFLATING - yield) ; | |
472 } else { | |
473 // Note that the following code attenuates the livelock problem but is not | |
474 // a complete remedy. A more complete solution would require that the inflating | |
475 // thread hold the associated inflation lock. The following code simply restricts | |
476 // the number of spinners to at most one. We'll have N-2 threads blocked | |
477 // on the inflationlock, 1 thread holding the inflation lock and using | |
478 // a yield/park strategy, and 1 thread in the midst of inflation. | |
479 // A more refined approach would be to change the encoding of INFLATING | |
480 // to allow encapsulation of a native thread pointer. Threads waiting for | |
481 // inflation to complete would use CAS to push themselves onto a singly linked | |
482 // list rooted at the markword. Once enqueued, they'd loop, checking a per-thread flag | |
483 // and calling park(). When inflation was complete the thread that accomplished inflation | |
484 // would detach the list and set the markword to inflated with a single CAS and | |
485 // then for each thread on the list, set the flag and unpark() the thread. | |
486 // This is conceptually similar to muxAcquire-muxRelease, except that muxRelease | |
487 // wakes at most one thread whereas we need to wake the entire list. | |
488 int ix = (intptr_t(obj) >> 5) & (NINFLATIONLOCKS-1) ; | |
489 int YieldThenBlock = 0 ; | |
490 assert (ix >= 0 && ix < NINFLATIONLOCKS, "invariant") ; | |
491 assert ((NINFLATIONLOCKS & (NINFLATIONLOCKS-1)) == 0, "invariant") ; | |
492 Thread::muxAcquire (InflationLocks + ix, "InflationLock") ; | |
493 while (obj->mark() == markOopDesc::INFLATING()) { | |
494 // Beware: NakedYield() is advisory and has almost no effect on some platforms | |
495 // so we periodically call Self->_ParkEvent->park(1). | |
496 // We use a mixed spin/yield/block mechanism. | |
497 if ((YieldThenBlock++) >= 16) { | |
498 Thread::current()->_ParkEvent->park(1) ; | |
499 } else { | |
500 os::NakedYield() ; | |
501 } | |
502 } | |
503 Thread::muxRelease (InflationLocks + ix ) ; | |
504 TEVENT (Inflate: INFLATING - yield/park) ; | |
505 } | |
506 } else { | |
507 SpinPause() ; // SMP-polite spinning | |
508 } | |
509 } | |
510 } | |
0 | 511 |
512 // hashCode() generation : | |
513 // | |
514 // Possibilities: | |
515 // * MD5Digest of {obj,stwRandom} | |
516 // * CRC32 of {obj,stwRandom} or any linear-feedback shift register function. | |
517 // * A DES- or AES-style SBox[] mechanism | |
518 // * One of the Phi-based schemes, such as: | |
519 // 2654435761 = 2^32 * Phi (golden ratio) | |
520 // HashCodeValue = ((uintptr_t(obj) >> 3) * 2654435761) ^ GVars.stwRandom ; | |
521 // * A variation of Marsaglia's shift-xor RNG scheme. | |
522 // * (obj ^ stwRandom) is appealing, but can result | |
523 // in undesirable regularity in the hashCode values of adjacent objects | |
524 // (objects allocated back-to-back, in particular). This could potentially | |
525 // result in hashtable collisions and reduced hashtable efficiency. | |
526 // There are simple ways to "diffuse" the middle address bits over the | |
527 // generated hashCode values: | |
528 // | |
529 | |
530 static inline intptr_t get_next_hash(Thread * Self, oop obj) { | |
531 intptr_t value = 0 ; | |
532 if (hashCode == 0) { | |
533 // This form uses an unguarded global Park-Miller RNG, | |
534 // so it's possible for two threads to race and generate the same RNG. | |
535 // On MP system we'll have lots of RW access to a global, so the | |
536 // mechanism induces lots of coherency traffic. | |
537 value = os::random() ; | |
538 } else | |
539 if (hashCode == 1) { | |
540 // This variation has the property of being stable (idempotent) | |
541 // between STW operations. This can be useful in some of the 1-0 | |
542 // synchronization schemes. | |
543 intptr_t addrBits = intptr_t(obj) >> 3 ; | |
544 value = addrBits ^ (addrBits >> 5) ^ GVars.stwRandom ; | |
545 } else | |
546 if (hashCode == 2) { | |
547 value = 1 ; // for sensitivity testing | |
548 } else | |
549 if (hashCode == 3) { | |
550 value = ++GVars.hcSequence ; | |
551 } else | |
552 if (hashCode == 4) { | |
553 value = intptr_t(obj) ; | |
554 } else { | |
555 // Marsaglia's xor-shift scheme with thread-specific state | |
556 // This is probably the best overall implementation -- we'll | |
557 // likely make this the default in future releases. | |
558 unsigned t = Self->_hashStateX ; | |
559 t ^= (t << 11) ; | |
560 Self->_hashStateX = Self->_hashStateY ; | |
561 Self->_hashStateY = Self->_hashStateZ ; | |
562 Self->_hashStateZ = Self->_hashStateW ; | |
563 unsigned v = Self->_hashStateW ; | |
564 v = (v ^ (v >> 19)) ^ (t ^ (t >> 8)) ; | |
565 Self->_hashStateW = v ; | |
566 value = v ; | |
567 } | |
568 | |
569 value &= markOopDesc::hash_mask; | |
570 if (value == 0) value = 0xBAD ; | |
571 assert (value != markOopDesc::no_hash, "invariant") ; | |
572 TEVENT (hashCode: GENERATE) ; | |
573 return value; | |
574 } | |
1878 | 575 // |
576 intptr_t ObjectSynchronizer::FastHashCode (Thread * Self, oop obj) { | |
577 if (UseBiasedLocking) { | |
578 // NOTE: many places throughout the JVM do not expect a safepoint | |
579 // to be taken here, in particular most operations on perm gen | |
580 // objects. However, we only ever bias Java instances and all of | |
581 // the call sites of identity_hash that might revoke biases have | |
582 // been checked to make sure they can handle a safepoint. The | |
583 // added check of the bias pattern is to avoid useless calls to | |
584 // thread-local storage. | |
585 if (obj->mark()->has_bias_pattern()) { | |
586 // Box and unbox the raw reference just in case we cause a STW safepoint. | |
587 Handle hobj (Self, obj) ; | |
588 // Relaxing assertion for bug 6320749. | |
589 assert (Universe::verify_in_progress() || | |
590 !SafepointSynchronize::is_at_safepoint(), | |
591 "biases should not be seen by VM thread here"); | |
592 BiasedLocking::revoke_and_rebias(hobj, false, JavaThread::current()); | |
593 obj = hobj() ; | |
594 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
595 } | |
596 } | |
0 | 597 |
1878 | 598 // hashCode() is a heap mutator ... |
599 // Relaxing assertion for bug 6320749. | |
600 assert (Universe::verify_in_progress() || | |
601 !SafepointSynchronize::is_at_safepoint(), "invariant") ; | |
602 assert (Universe::verify_in_progress() || | |
603 Self->is_Java_thread() , "invariant") ; | |
604 assert (Universe::verify_in_progress() || | |
605 ((JavaThread *)Self)->thread_state() != _thread_blocked, "invariant") ; | |
606 | |
607 ObjectMonitor* monitor = NULL; | |
608 markOop temp, test; | |
609 intptr_t hash; | |
610 markOop mark = ReadStableMark (obj); | |
611 | |
612 // object should remain ineligible for biased locking | |
613 assert (!mark->has_bias_pattern(), "invariant") ; | |
614 | |
615 if (mark->is_neutral()) { | |
616 hash = mark->hash(); // this is a normal header | |
617 if (hash) { // if it has hash, just return it | |
618 return hash; | |
619 } | |
620 hash = get_next_hash(Self, obj); // allocate a new hash code | |
621 temp = mark->copy_set_hash(hash); // merge the hash code into header | |
622 // use (machine word version) atomic operation to install the hash | |
623 test = (markOop) Atomic::cmpxchg_ptr(temp, obj->mark_addr(), mark); | |
624 if (test == mark) { | |
625 return hash; | |
626 } | |
627 // If atomic operation failed, we must inflate the header | |
628 // into heavy weight monitor. We could add more code here | |
629 // for fast path, but it does not worth the complexity. | |
630 } else if (mark->has_monitor()) { | |
631 monitor = mark->monitor(); | |
632 temp = monitor->header(); | |
633 assert (temp->is_neutral(), "invariant") ; | |
634 hash = temp->hash(); | |
635 if (hash) { | |
636 return hash; | |
637 } | |
638 // Skip to the following code to reduce code size | |
639 } else if (Self->is_lock_owned((address)mark->locker())) { | |
640 temp = mark->displaced_mark_helper(); // this is a lightweight monitor owned | |
641 assert (temp->is_neutral(), "invariant") ; | |
642 hash = temp->hash(); // by current thread, check if the displaced | |
643 if (hash) { // header contains hash code | |
644 return hash; | |
645 } | |
646 // WARNING: | |
647 // The displaced header is strictly immutable. | |
648 // It can NOT be changed in ANY cases. So we have | |
649 // to inflate the header into heavyweight monitor | |
650 // even the current thread owns the lock. The reason | |
651 // is the BasicLock (stack slot) will be asynchronously | |
652 // read by other threads during the inflate() function. | |
653 // Any change to stack may not propagate to other threads | |
654 // correctly. | |
655 } | |
656 | |
657 // Inflate the monitor to set hash code | |
658 monitor = ObjectSynchronizer::inflate(Self, obj); | |
659 // Load displaced header and check it has hash code | |
660 mark = monitor->header(); | |
661 assert (mark->is_neutral(), "invariant") ; | |
662 hash = mark->hash(); | |
663 if (hash == 0) { | |
664 hash = get_next_hash(Self, obj); | |
665 temp = mark->copy_set_hash(hash); // merge hash code into header | |
666 assert (temp->is_neutral(), "invariant") ; | |
667 test = (markOop) Atomic::cmpxchg_ptr(temp, monitor, mark); | |
668 if (test != mark) { | |
669 // The only update to the header in the monitor (outside GC) | |
670 // is install the hash code. If someone add new usage of | |
671 // displaced header, please update this code | |
672 hash = test->hash(); | |
673 assert (test->is_neutral(), "invariant") ; | |
674 assert (hash != 0, "Trivial unexpected object/monitor header usage."); | |
675 } | |
676 } | |
677 // We finally get the hash | |
678 return hash; | |
0 | 679 } |
680 | |
1878 | 681 // Deprecated -- use FastHashCode() instead. |
0 | 682 |
1878 | 683 intptr_t ObjectSynchronizer::identity_hash_value_for(Handle obj) { |
684 return FastHashCode (Thread::current(), obj()) ; | |
0 | 685 } |
686 | |
687 | |
1878 | 688 bool ObjectSynchronizer::current_thread_holds_lock(JavaThread* thread, |
689 Handle h_obj) { | |
690 if (UseBiasedLocking) { | |
691 BiasedLocking::revoke_and_rebias(h_obj, false, thread); | |
692 assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
693 } | |
694 | |
695 assert(thread == JavaThread::current(), "Can only be called on current thread"); | |
696 oop obj = h_obj(); | |
697 | |
698 markOop mark = ReadStableMark (obj) ; | |
0 | 699 |
1878 | 700 // Uncontended case, header points to stack |
701 if (mark->has_locker()) { | |
702 return thread->is_lock_owned((address)mark->locker()); | |
0 | 703 } |
1878 | 704 // Contended case, header points to ObjectMonitor (tagged pointer) |
705 if (mark->has_monitor()) { | |
706 ObjectMonitor* monitor = mark->monitor(); | |
707 return monitor->is_entered(thread) != 0 ; | |
0 | 708 } |
1878 | 709 // Unlocked case, header in place |
710 assert(mark->is_neutral(), "sanity check"); | |
711 return false; | |
0 | 712 } |
713 | |
1878 | 714 // Be aware of this method could revoke bias of the lock object. |
715 // This method querys the ownership of the lock handle specified by 'h_obj'. | |
716 // If the current thread owns the lock, it returns owner_self. If no | |
717 // thread owns the lock, it returns owner_none. Otherwise, it will return | |
718 // ower_other. | |
719 ObjectSynchronizer::LockOwnership ObjectSynchronizer::query_lock_ownership | |
720 (JavaThread *self, Handle h_obj) { | |
721 // The caller must beware this method can revoke bias, and | |
722 // revocation can result in a safepoint. | |
723 assert (!SafepointSynchronize::is_at_safepoint(), "invariant") ; | |
724 assert (self->thread_state() != _thread_blocked , "invariant") ; | |
0 | 725 |
1878 | 726 // Possible mark states: neutral, biased, stack-locked, inflated |
727 | |
728 if (UseBiasedLocking && h_obj()->mark()->has_bias_pattern()) { | |
729 // CASE: biased | |
730 BiasedLocking::revoke_and_rebias(h_obj, false, self); | |
731 assert(!h_obj->mark()->has_bias_pattern(), | |
732 "biases should be revoked by now"); | |
733 } | |
0 | 734 |
1878 | 735 assert(self == JavaThread::current(), "Can only be called on current thread"); |
736 oop obj = h_obj(); | |
737 markOop mark = ReadStableMark (obj) ; | |
738 | |
739 // CASE: stack-locked. Mark points to a BasicLock on the owner's stack. | |
740 if (mark->has_locker()) { | |
741 return self->is_lock_owned((address)mark->locker()) ? | |
742 owner_self : owner_other; | |
743 } | |
0 | 744 |
1878 | 745 // CASE: inflated. Mark (tagged pointer) points to an objectMonitor. |
746 // The Object:ObjectMonitor relationship is stable as long as we're | |
747 // not at a safepoint. | |
748 if (mark->has_monitor()) { | |
749 void * owner = mark->monitor()->_owner ; | |
750 if (owner == NULL) return owner_none ; | |
751 return (owner == self || | |
752 self->is_lock_owned((address)owner)) ? owner_self : owner_other; | |
753 } | |
754 | |
755 // CASE: neutral | |
756 assert(mark->is_neutral(), "sanity check"); | |
757 return owner_none ; // it's unlocked | |
758 } | |
0 | 759 |
1878 | 760 // FIXME: jvmti should call this |
761 JavaThread* ObjectSynchronizer::get_lock_owner(Handle h_obj, bool doLock) { | |
762 if (UseBiasedLocking) { | |
763 if (SafepointSynchronize::is_at_safepoint()) { | |
764 BiasedLocking::revoke_at_safepoint(h_obj); | |
765 } else { | |
766 BiasedLocking::revoke_and_rebias(h_obj, false, JavaThread::current()); | |
767 } | |
768 assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
769 } | |
770 | |
771 oop obj = h_obj(); | |
772 address owner = NULL; | |
773 | |
774 markOop mark = ReadStableMark (obj) ; | |
775 | |
776 // Uncontended case, header points to stack | |
777 if (mark->has_locker()) { | |
778 owner = (address) mark->locker(); | |
779 } | |
780 | |
781 // Contended case, header points to ObjectMonitor (tagged pointer) | |
782 if (mark->has_monitor()) { | |
783 ObjectMonitor* monitor = mark->monitor(); | |
784 assert(monitor != NULL, "monitor should be non-null"); | |
785 owner = (address) monitor->owner(); | |
786 } | |
787 | |
788 if (owner != NULL) { | |
789 return Threads::owning_thread_from_monitor_owner(owner, doLock); | |
790 } | |
791 | |
792 // Unlocked case, header in place | |
793 // Cannot have assertion since this object may have been | |
794 // locked by another thread when reaching here. | |
795 // assert(mark->is_neutral(), "sanity check"); | |
796 | |
797 return NULL; | |
798 } | |
799 // Visitors ... | |
800 | |
801 void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure) { | |
802 ObjectMonitor* block = gBlockList; | |
803 ObjectMonitor* mid; | |
804 while (block) { | |
805 assert(block->object() == CHAINMARKER, "must be a block header"); | |
806 for (int i = _BLOCKSIZE - 1; i > 0; i--) { | |
807 mid = block + i; | |
808 oop object = (oop) mid->object(); | |
809 if (object != NULL) { | |
810 closure->do_monitor(mid); | |
811 } | |
812 } | |
813 block = (ObjectMonitor*) block->FreeNext; | |
0 | 814 } |
815 } | |
816 | |
1878 | 817 // Get the next block in the block list. |
818 static inline ObjectMonitor* next(ObjectMonitor* block) { | |
819 assert(block->object() == CHAINMARKER, "must be a block header"); | |
820 block = block->FreeNext ; | |
821 assert(block == NULL || block->object() == CHAINMARKER, "must be a block header"); | |
822 return block; | |
0 | 823 } |
824 | |
825 | |
1878 | 826 void ObjectSynchronizer::oops_do(OopClosure* f) { |
827 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); | |
828 for (ObjectMonitor* block = gBlockList; block != NULL; block = next(block)) { | |
829 assert(block->object() == CHAINMARKER, "must be a block header"); | |
830 for (int i = 1; i < _BLOCKSIZE; i++) { | |
831 ObjectMonitor* mid = &block[i]; | |
832 if (mid->object() != NULL) { | |
833 f->do_oop((oop*)mid->object_addr()); | |
0 | 834 } |
835 } | |
836 } | |
837 } | |
838 | |
839 | |
1878 | 840 // ----------------------------------------------------------------------------- |
0 | 841 // ObjectMonitor Lifecycle |
842 // ----------------------- | |
843 // Inflation unlinks monitors from the global gFreeList and | |
844 // associates them with objects. Deflation -- which occurs at | |
845 // STW-time -- disassociates idle monitors from objects. Such | |
846 // scavenged monitors are returned to the gFreeList. | |
847 // | |
848 // The global list is protected by ListLock. All the critical sections | |
849 // are short and operate in constant-time. | |
850 // | |
851 // ObjectMonitors reside in type-stable memory (TSM) and are immortal. | |
852 // | |
853 // Lifecycle: | |
854 // -- unassigned and on the global free list | |
855 // -- unassigned and on a thread's private omFreeList | |
856 // -- assigned to an object. The object is inflated and the mark refers | |
857 // to the objectmonitor. | |
858 // | |
859 | |
860 | |
1587 | 861 // Constraining monitor pool growth via MonitorBound ... |
862 // | |
863 // The monitor pool is grow-only. We scavenge at STW safepoint-time, but the | |
864 // the rate of scavenging is driven primarily by GC. As such, we can find | |
865 // an inordinate number of monitors in circulation. | |
866 // To avoid that scenario we can artificially induce a STW safepoint | |
867 // if the pool appears to be growing past some reasonable bound. | |
868 // Generally we favor time in space-time tradeoffs, but as there's no | |
869 // natural back-pressure on the # of extant monitors we need to impose some | |
870 // type of limit. Beware that if MonitorBound is set to too low a value | |
871 // we could just loop. In addition, if MonitorBound is set to a low value | |
872 // we'll incur more safepoints, which are harmful to performance. | |
873 // See also: GuaranteedSafepointInterval | |
874 // | |
875 // The current implementation uses asynchronous VM operations. | |
876 // | |
877 | |
878 static void InduceScavenge (Thread * Self, const char * Whence) { | |
879 // Induce STW safepoint to trim monitors | |
880 // Ultimately, this results in a call to deflate_idle_monitors() in the near future. | |
881 // More precisely, trigger an asynchronous STW safepoint as the number | |
882 // of active monitors passes the specified threshold. | |
883 // TODO: assert thread state is reasonable | |
884 | |
885 if (ForceMonitorScavenge == 0 && Atomic::xchg (1, &ForceMonitorScavenge) == 0) { | |
1878 | 886 if (ObjectMonitor::Knob_Verbose) { |
1587 | 887 ::printf ("Monitor scavenge - Induced STW @%s (%d)\n", Whence, ForceMonitorScavenge) ; |
888 ::fflush(stdout) ; | |
889 } | |
890 // Induce a 'null' safepoint to scavenge monitors | |
891 // Must VM_Operation instance be heap allocated as the op will be enqueue and posted | |
892 // to the VMthread and have a lifespan longer than that of this activation record. | |
893 // The VMThread will delete the op when completed. | |
894 VMThread::execute (new VM_ForceAsyncSafepoint()) ; | |
895 | |
1878 | 896 if (ObjectMonitor::Knob_Verbose) { |
1587 | 897 ::printf ("Monitor scavenge - STW posted @%s (%d)\n", Whence, ForceMonitorScavenge) ; |
898 ::fflush(stdout) ; | |
899 } | |
900 } | |
901 } | |
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902 /* Too slow for general assert or debug |
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903 void ObjectSynchronizer::verifyInUse (Thread *Self) { |
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904 ObjectMonitor* mid; |
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905 int inusetally = 0; |
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906 for (mid = Self->omInUseList; mid != NULL; mid = mid->FreeNext) { |
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907 inusetally ++; |
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908 } |
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909 assert(inusetally == Self->omInUseCount, "inuse count off"); |
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910 |
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911 int freetally = 0; |
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912 for (mid = Self->omFreeList; mid != NULL; mid = mid->FreeNext) { |
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913 freetally ++; |
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914 } |
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915 assert(freetally == Self->omFreeCount, "free count off"); |
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916 } |
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917 */ |
0 | 918 ObjectMonitor * ATTR ObjectSynchronizer::omAlloc (Thread * Self) { |
919 // A large MAXPRIVATE value reduces both list lock contention | |
920 // and list coherency traffic, but also tends to increase the | |
921 // number of objectMonitors in circulation as well as the STW | |
922 // scavenge costs. As usual, we lean toward time in space-time | |
923 // tradeoffs. | |
924 const int MAXPRIVATE = 1024 ; | |
925 for (;;) { | |
926 ObjectMonitor * m ; | |
927 | |
928 // 1: try to allocate from the thread's local omFreeList. | |
929 // Threads will attempt to allocate first from their local list, then | |
930 // from the global list, and only after those attempts fail will the thread | |
931 // attempt to instantiate new monitors. Thread-local free lists take | |
932 // heat off the ListLock and improve allocation latency, as well as reducing | |
933 // coherency traffic on the shared global list. | |
934 m = Self->omFreeList ; | |
935 if (m != NULL) { | |
936 Self->omFreeList = m->FreeNext ; | |
937 Self->omFreeCount -- ; | |
938 // CONSIDER: set m->FreeNext = BAD -- diagnostic hygiene | |
939 guarantee (m->object() == NULL, "invariant") ; | |
1587 | 940 if (MonitorInUseLists) { |
941 m->FreeNext = Self->omInUseList; | |
942 Self->omInUseList = m; | |
943 Self->omInUseCount ++; | |
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944 // verifyInUse(Self); |
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945 } else { |
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946 m->FreeNext = NULL; |
1587 | 947 } |
0 | 948 return m ; |
949 } | |
950 | |
951 // 2: try to allocate from the global gFreeList | |
952 // CONSIDER: use muxTry() instead of muxAcquire(). | |
953 // If the muxTry() fails then drop immediately into case 3. | |
954 // If we're using thread-local free lists then try | |
955 // to reprovision the caller's free list. | |
956 if (gFreeList != NULL) { | |
957 // Reprovision the thread's omFreeList. | |
958 // Use bulk transfers to reduce the allocation rate and heat | |
959 // on various locks. | |
960 Thread::muxAcquire (&ListLock, "omAlloc") ; | |
961 for (int i = Self->omFreeProvision; --i >= 0 && gFreeList != NULL; ) { | |
1587 | 962 MonitorFreeCount --; |
0 | 963 ObjectMonitor * take = gFreeList ; |
964 gFreeList = take->FreeNext ; | |
965 guarantee (take->object() == NULL, "invariant") ; | |
966 guarantee (!take->is_busy(), "invariant") ; | |
967 take->Recycle() ; | |
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968 omRelease (Self, take, false) ; |
0 | 969 } |
970 Thread::muxRelease (&ListLock) ; | |
971 Self->omFreeProvision += 1 + (Self->omFreeProvision/2) ; | |
972 if (Self->omFreeProvision > MAXPRIVATE ) Self->omFreeProvision = MAXPRIVATE ; | |
973 TEVENT (omFirst - reprovision) ; | |
1587 | 974 |
975 const int mx = MonitorBound ; | |
976 if (mx > 0 && (MonitorPopulation-MonitorFreeCount) > mx) { | |
977 // We can't safely induce a STW safepoint from omAlloc() as our thread | |
978 // state may not be appropriate for such activities and callers may hold | |
979 // naked oops, so instead we defer the action. | |
980 InduceScavenge (Self, "omAlloc") ; | |
981 } | |
982 continue; | |
0 | 983 } |
984 | |
985 // 3: allocate a block of new ObjectMonitors | |
986 // Both the local and global free lists are empty -- resort to malloc(). | |
987 // In the current implementation objectMonitors are TSM - immortal. | |
988 assert (_BLOCKSIZE > 1, "invariant") ; | |
989 ObjectMonitor * temp = new ObjectMonitor[_BLOCKSIZE]; | |
990 | |
991 // NOTE: (almost) no way to recover if allocation failed. | |
992 // We might be able to induce a STW safepoint and scavenge enough | |
993 // objectMonitors to permit progress. | |
994 if (temp == NULL) { | |
995 vm_exit_out_of_memory (sizeof (ObjectMonitor[_BLOCKSIZE]), "Allocate ObjectMonitors") ; | |
996 } | |
997 | |
998 // Format the block. | |
999 // initialize the linked list, each monitor points to its next | |
1000 // forming the single linked free list, the very first monitor | |
1001 // will points to next block, which forms the block list. | |
1002 // The trick of using the 1st element in the block as gBlockList | |
1003 // linkage should be reconsidered. A better implementation would | |
1004 // look like: class Block { Block * next; int N; ObjectMonitor Body [N] ; } | |
1005 | |
1006 for (int i = 1; i < _BLOCKSIZE ; i++) { | |
1007 temp[i].FreeNext = &temp[i+1]; | |
1008 } | |
1009 | |
1010 // terminate the last monitor as the end of list | |
1011 temp[_BLOCKSIZE - 1].FreeNext = NULL ; | |
1012 | |
1013 // Element [0] is reserved for global list linkage | |
1014 temp[0].set_object(CHAINMARKER); | |
1015 | |
1016 // Consider carving out this thread's current request from the | |
1017 // block in hand. This avoids some lock traffic and redundant | |
1018 // list activity. | |
1019 | |
1020 // Acquire the ListLock to manipulate BlockList and FreeList. | |
1021 // An Oyama-Taura-Yonezawa scheme might be more efficient. | |
1022 Thread::muxAcquire (&ListLock, "omAlloc [2]") ; | |
1587 | 1023 MonitorPopulation += _BLOCKSIZE-1; |
1024 MonitorFreeCount += _BLOCKSIZE-1; | |
0 | 1025 |
1026 // Add the new block to the list of extant blocks (gBlockList). | |
1027 // The very first objectMonitor in a block is reserved and dedicated. | |
1028 // It serves as blocklist "next" linkage. | |
1029 temp[0].FreeNext = gBlockList; | |
1030 gBlockList = temp; | |
1031 | |
1032 // Add the new string of objectMonitors to the global free list | |
1033 temp[_BLOCKSIZE - 1].FreeNext = gFreeList ; | |
1034 gFreeList = temp + 1; | |
1035 Thread::muxRelease (&ListLock) ; | |
1036 TEVENT (Allocate block of monitors) ; | |
1037 } | |
1038 } | |
1039 | |
1040 // Place "m" on the caller's private per-thread omFreeList. | |
1041 // In practice there's no need to clamp or limit the number of | |
1042 // monitors on a thread's omFreeList as the only time we'll call | |
1043 // omRelease is to return a monitor to the free list after a CAS | |
1044 // attempt failed. This doesn't allow unbounded #s of monitors to | |
1045 // accumulate on a thread's free list. | |
1046 // | |
1047 | |
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1048 void ObjectSynchronizer::omRelease (Thread * Self, ObjectMonitor * m, bool fromPerThreadAlloc) { |
0 | 1049 guarantee (m->object() == NULL, "invariant") ; |
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1050 |
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1051 // Remove from omInUseList |
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1052 if (MonitorInUseLists && fromPerThreadAlloc) { |
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1053 ObjectMonitor* curmidinuse = NULL; |
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1054 for (ObjectMonitor* mid = Self->omInUseList; mid != NULL; ) { |
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1055 if (m == mid) { |
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1056 // extract from per-thread in-use-list |
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1057 if (mid == Self->omInUseList) { |
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1058 Self->omInUseList = mid->FreeNext; |
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1059 } else if (curmidinuse != NULL) { |
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1060 curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist |
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1061 } |
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1062 Self->omInUseCount --; |
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1063 // verifyInUse(Self); |
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1064 break; |
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1065 } else { |
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1066 curmidinuse = mid; |
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1067 mid = mid->FreeNext; |
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1068 } |
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1069 } |
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1070 } |
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1071 |
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1072 // FreeNext is used for both onInUseList and omFreeList, so clear old before setting new |
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1073 m->FreeNext = Self->omFreeList ; |
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1074 Self->omFreeList = m ; |
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1075 Self->omFreeCount ++ ; |
0 | 1076 } |
1077 | |
1078 // Return the monitors of a moribund thread's local free list to | |
1079 // the global free list. Typically a thread calls omFlush() when | |
1080 // it's dying. We could also consider having the VM thread steal | |
1081 // monitors from threads that have not run java code over a few | |
1082 // consecutive STW safepoints. Relatedly, we might decay | |
1083 // omFreeProvision at STW safepoints. | |
1084 // | |
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1085 // Also return the monitors of a moribund thread"s omInUseList to |
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1086 // a global gOmInUseList under the global list lock so these |
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1087 // will continue to be scanned. |
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1088 // |
0 | 1089 // We currently call omFlush() from the Thread:: dtor _after the thread |
1090 // has been excised from the thread list and is no longer a mutator. | |
1091 // That means that omFlush() can run concurrently with a safepoint and | |
1092 // the scavenge operator. Calling omFlush() from JavaThread::exit() might | |
1093 // be a better choice as we could safely reason that that the JVM is | |
1094 // not at a safepoint at the time of the call, and thus there could | |
1095 // be not inopportune interleavings between omFlush() and the scavenge | |
1096 // operator. | |
1097 | |
1098 void ObjectSynchronizer::omFlush (Thread * Self) { | |
1099 ObjectMonitor * List = Self->omFreeList ; // Null-terminated SLL | |
1100 Self->omFreeList = NULL ; | |
1101 ObjectMonitor * Tail = NULL ; | |
1587 | 1102 int Tally = 0; |
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1103 if (List != NULL) { |
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1104 ObjectMonitor * s ; |
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1105 for (s = List ; s != NULL ; s = s->FreeNext) { |
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1106 Tally ++ ; |
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1107 Tail = s ; |
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1108 guarantee (s->object() == NULL, "invariant") ; |
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1109 guarantee (!s->is_busy(), "invariant") ; |
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1110 s->set_owner (NULL) ; // redundant but good hygiene |
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1111 TEVENT (omFlush - Move one) ; |
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1112 } |
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1113 guarantee (Tail != NULL && List != NULL, "invariant") ; |
0 | 1114 } |
1115 | |
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1116 ObjectMonitor * InUseList = Self->omInUseList; |
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1117 ObjectMonitor * InUseTail = NULL ; |
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1118 int InUseTally = 0; |
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1119 if (InUseList != NULL) { |
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1120 Self->omInUseList = NULL; |
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1121 ObjectMonitor *curom; |
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1122 for (curom = InUseList; curom != NULL; curom = curom->FreeNext) { |
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1123 InUseTail = curom; |
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1124 InUseTally++; |
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1125 } |
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1126 // TODO debug |
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1127 assert(Self->omInUseCount == InUseTally, "inuse count off"); |
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1128 Self->omInUseCount = 0; |
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1129 guarantee (InUseTail != NULL && InUseList != NULL, "invariant"); |
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1130 } |
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1131 |
0 | 1132 Thread::muxAcquire (&ListLock, "omFlush") ; |
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1133 if (Tail != NULL) { |
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1134 Tail->FreeNext = gFreeList ; |
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1135 gFreeList = List ; |
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1136 MonitorFreeCount += Tally; |
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1137 } |
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1138 |
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1139 if (InUseTail != NULL) { |
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1140 InUseTail->FreeNext = gOmInUseList; |
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1141 gOmInUseList = InUseList; |
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1142 gOmInUseCount += InUseTally; |
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1143 } |
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1144 |
0 | 1145 Thread::muxRelease (&ListLock) ; |
1146 TEVENT (omFlush) ; | |
1147 } | |
1148 | |
1149 // Fast path code shared by multiple functions | |
1150 ObjectMonitor* ObjectSynchronizer::inflate_helper(oop obj) { | |
1151 markOop mark = obj->mark(); | |
1152 if (mark->has_monitor()) { | |
1153 assert(ObjectSynchronizer::verify_objmon_isinpool(mark->monitor()), "monitor is invalid"); | |
1154 assert(mark->monitor()->header()->is_neutral(), "monitor must record a good object header"); | |
1155 return mark->monitor(); | |
1156 } | |
1157 return ObjectSynchronizer::inflate(Thread::current(), obj); | |
1158 } | |
1159 | |
1878 | 1160 |
0 | 1161 // Note that we could encounter some performance loss through false-sharing as |
1162 // multiple locks occupy the same $ line. Padding might be appropriate. | |
1163 | |
1164 | |
1165 ObjectMonitor * ATTR ObjectSynchronizer::inflate (Thread * Self, oop object) { | |
1166 // Inflate mutates the heap ... | |
1167 // Relaxing assertion for bug 6320749. | |
1168 assert (Universe::verify_in_progress() || | |
1169 !SafepointSynchronize::is_at_safepoint(), "invariant") ; | |
1170 | |
1171 for (;;) { | |
1172 const markOop mark = object->mark() ; | |
1173 assert (!mark->has_bias_pattern(), "invariant") ; | |
1174 | |
1175 // The mark can be in one of the following states: | |
1176 // * Inflated - just return | |
1177 // * Stack-locked - coerce it to inflated | |
1178 // * INFLATING - busy wait for conversion to complete | |
1179 // * Neutral - aggressively inflate the object. | |
1180 // * BIASED - Illegal. We should never see this | |
1181 | |
1182 // CASE: inflated | |
1183 if (mark->has_monitor()) { | |
1184 ObjectMonitor * inf = mark->monitor() ; | |
1185 assert (inf->header()->is_neutral(), "invariant"); | |
1186 assert (inf->object() == object, "invariant") ; | |
1187 assert (ObjectSynchronizer::verify_objmon_isinpool(inf), "monitor is invalid"); | |
1188 return inf ; | |
1189 } | |
1190 | |
1191 // CASE: inflation in progress - inflating over a stack-lock. | |
1192 // Some other thread is converting from stack-locked to inflated. | |
1193 // Only that thread can complete inflation -- other threads must wait. | |
1194 // The INFLATING value is transient. | |
1195 // Currently, we spin/yield/park and poll the markword, waiting for inflation to finish. | |
1196 // We could always eliminate polling by parking the thread on some auxiliary list. | |
1197 if (mark == markOopDesc::INFLATING()) { | |
1198 TEVENT (Inflate: spin while INFLATING) ; | |
1199 ReadStableMark(object) ; | |
1200 continue ; | |
1201 } | |
1202 | |
1203 // CASE: stack-locked | |
1204 // Could be stack-locked either by this thread or by some other thread. | |
1205 // | |
1206 // Note that we allocate the objectmonitor speculatively, _before_ attempting | |
1207 // to install INFLATING into the mark word. We originally installed INFLATING, | |
1208 // allocated the objectmonitor, and then finally STed the address of the | |
1209 // objectmonitor into the mark. This was correct, but artificially lengthened | |
1210 // the interval in which INFLATED appeared in the mark, thus increasing | |
1211 // the odds of inflation contention. | |
1212 // | |
1213 // We now use per-thread private objectmonitor free lists. | |
1214 // These list are reprovisioned from the global free list outside the | |
1215 // critical INFLATING...ST interval. A thread can transfer | |
1216 // multiple objectmonitors en-mass from the global free list to its local free list. | |
1217 // This reduces coherency traffic and lock contention on the global free list. | |
1218 // Using such local free lists, it doesn't matter if the omAlloc() call appears | |
1219 // before or after the CAS(INFLATING) operation. | |
1220 // See the comments in omAlloc(). | |
1221 | |
1222 if (mark->has_locker()) { | |
1223 ObjectMonitor * m = omAlloc (Self) ; | |
1224 // Optimistically prepare the objectmonitor - anticipate successful CAS | |
1225 // We do this before the CAS in order to minimize the length of time | |
1226 // in which INFLATING appears in the mark. | |
1227 m->Recycle(); | |
1228 m->_Responsible = NULL ; | |
1229 m->OwnerIsThread = 0 ; | |
1230 m->_recursions = 0 ; | |
1878 | 1231 m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ; // Consider: maintain by type/class |
0 | 1232 |
1233 markOop cmp = (markOop) Atomic::cmpxchg_ptr (markOopDesc::INFLATING(), object->mark_addr(), mark) ; | |
1234 if (cmp != mark) { | |
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1235 omRelease (Self, m, true) ; |
0 | 1236 continue ; // Interference -- just retry |
1237 } | |
1238 | |
1239 // We've successfully installed INFLATING (0) into the mark-word. | |
1240 // This is the only case where 0 will appear in a mark-work. | |
1241 // Only the singular thread that successfully swings the mark-word | |
1242 // to 0 can perform (or more precisely, complete) inflation. | |
1243 // | |
1244 // Why do we CAS a 0 into the mark-word instead of just CASing the | |
1245 // mark-word from the stack-locked value directly to the new inflated state? | |
1246 // Consider what happens when a thread unlocks a stack-locked object. | |
1247 // It attempts to use CAS to swing the displaced header value from the | |
1248 // on-stack basiclock back into the object header. Recall also that the | |
1249 // header value (hashcode, etc) can reside in (a) the object header, or | |
1250 // (b) a displaced header associated with the stack-lock, or (c) a displaced | |
1251 // header in an objectMonitor. The inflate() routine must copy the header | |
1252 // value from the basiclock on the owner's stack to the objectMonitor, all | |
1253 // the while preserving the hashCode stability invariants. If the owner | |
1254 // decides to release the lock while the value is 0, the unlock will fail | |
1255 // and control will eventually pass from slow_exit() to inflate. The owner | |
1256 // will then spin, waiting for the 0 value to disappear. Put another way, | |
1257 // the 0 causes the owner to stall if the owner happens to try to | |
1258 // drop the lock (restoring the header from the basiclock to the object) | |
1259 // while inflation is in-progress. This protocol avoids races that might | |
1260 // would otherwise permit hashCode values to change or "flicker" for an object. | |
1261 // Critically, while object->mark is 0 mark->displaced_mark_helper() is stable. | |
1262 // 0 serves as a "BUSY" inflate-in-progress indicator. | |
1263 | |
1264 | |
1265 // fetch the displaced mark from the owner's stack. | |
1266 // The owner can't die or unwind past the lock while our INFLATING | |
1267 // object is in the mark. Furthermore the owner can't complete | |
1268 // an unlock on the object, either. | |
1269 markOop dmw = mark->displaced_mark_helper() ; | |
1270 assert (dmw->is_neutral(), "invariant") ; | |
1271 | |
1272 // Setup monitor fields to proper values -- prepare the monitor | |
1273 m->set_header(dmw) ; | |
1274 | |
1275 // Optimization: if the mark->locker stack address is associated | |
1276 // with this thread we could simply set m->_owner = Self and | |
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1277 // m->OwnerIsThread = 1. Note that a thread can inflate an object |
0 | 1278 // that it has stack-locked -- as might happen in wait() -- directly |
1279 // with CAS. That is, we can avoid the xchg-NULL .... ST idiom. | |
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1280 m->set_owner(mark->locker()); |
0 | 1281 m->set_object(object); |
1282 // TODO-FIXME: assert BasicLock->dhw != 0. | |
1283 | |
1284 // Must preserve store ordering. The monitor state must | |
1285 // be stable at the time of publishing the monitor address. | |
1286 guarantee (object->mark() == markOopDesc::INFLATING(), "invariant") ; | |
1287 object->release_set_mark(markOopDesc::encode(m)); | |
1288 | |
1289 // Hopefully the performance counters are allocated on distinct cache lines | |
1290 // to avoid false sharing on MP systems ... | |
1878 | 1291 if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ; |
0 | 1292 TEVENT(Inflate: overwrite stacklock) ; |
1293 if (TraceMonitorInflation) { | |
1294 if (object->is_instance()) { | |
1295 ResourceMark rm; | |
1296 tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
1297 (intptr_t) object, (intptr_t) object->mark(), | |
1298 Klass::cast(object->klass())->external_name()); | |
1299 } | |
1300 } | |
1301 return m ; | |
1302 } | |
1303 | |
1304 // CASE: neutral | |
1305 // TODO-FIXME: for entry we currently inflate and then try to CAS _owner. | |
1306 // If we know we're inflating for entry it's better to inflate by swinging a | |
1307 // pre-locked objectMonitor pointer into the object header. A successful | |
1308 // CAS inflates the object *and* confers ownership to the inflating thread. | |
1309 // In the current implementation we use a 2-step mechanism where we CAS() | |
1310 // to inflate and then CAS() again to try to swing _owner from NULL to Self. | |
1311 // An inflateTry() method that we could call from fast_enter() and slow_enter() | |
1312 // would be useful. | |
1313 | |
1314 assert (mark->is_neutral(), "invariant"); | |
1315 ObjectMonitor * m = omAlloc (Self) ; | |
1316 // prepare m for installation - set monitor to initial state | |
1317 m->Recycle(); | |
1318 m->set_header(mark); | |
1319 m->set_owner(NULL); | |
1320 m->set_object(object); | |
1321 m->OwnerIsThread = 1 ; | |
1322 m->_recursions = 0 ; | |
1323 m->_Responsible = NULL ; | |
1878 | 1324 m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ; // consider: keep metastats by type/class |
0 | 1325 |
1326 if (Atomic::cmpxchg_ptr (markOopDesc::encode(m), object->mark_addr(), mark) != mark) { | |
1327 m->set_object (NULL) ; | |
1328 m->set_owner (NULL) ; | |
1329 m->OwnerIsThread = 0 ; | |
1330 m->Recycle() ; | |
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1331 omRelease (Self, m, true) ; |
0 | 1332 m = NULL ; |
1333 continue ; | |
1334 // interference - the markword changed - just retry. | |
1335 // The state-transitions are one-way, so there's no chance of | |
1336 // live-lock -- "Inflated" is an absorbing state. | |
1337 } | |
1338 | |
1339 // Hopefully the performance counters are allocated on distinct | |
1340 // cache lines to avoid false sharing on MP systems ... | |
1878 | 1341 if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ; |
0 | 1342 TEVENT(Inflate: overwrite neutral) ; |
1343 if (TraceMonitorInflation) { | |
1344 if (object->is_instance()) { | |
1345 ResourceMark rm; | |
1346 tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
1347 (intptr_t) object, (intptr_t) object->mark(), | |
1348 Klass::cast(object->klass())->external_name()); | |
1349 } | |
1350 } | |
1351 return m ; | |
1352 } | |
1353 } | |
1354 | |
1878 | 1355 // Note that we could encounter some performance loss through false-sharing as |
1356 // multiple locks occupy the same $ line. Padding might be appropriate. | |
0 | 1357 |
1358 | |
1359 // Deflate_idle_monitors() is called at all safepoints, immediately | |
1360 // after all mutators are stopped, but before any objects have moved. | |
1361 // It traverses the list of known monitors, deflating where possible. | |
1362 // The scavenged monitor are returned to the monitor free list. | |
1363 // | |
1364 // Beware that we scavenge at *every* stop-the-world point. | |
1365 // Having a large number of monitors in-circulation negatively | |
1366 // impacts the performance of some applications (e.g., PointBase). | |
1367 // Broadly, we want to minimize the # of monitors in circulation. | |
1587 | 1368 // |
1369 // We have added a flag, MonitorInUseLists, which creates a list | |
1370 // of active monitors for each thread. deflate_idle_monitors() | |
1371 // only scans the per-thread inuse lists. omAlloc() puts all | |
1372 // assigned monitors on the per-thread list. deflate_idle_monitors() | |
1373 // returns the non-busy monitors to the global free list. | |
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1374 // When a thread dies, omFlush() adds the list of active monitors for |
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1375 // that thread to a global gOmInUseList acquiring the |
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1376 // global list lock. deflate_idle_monitors() acquires the global |
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1377 // list lock to scan for non-busy monitors to the global free list. |
1587 | 1378 // An alternative could have used a single global inuse list. The |
1379 // downside would have been the additional cost of acquiring the global list lock | |
1380 // for every omAlloc(). | |
0 | 1381 // |
1382 // Perversely, the heap size -- and thus the STW safepoint rate -- | |
1383 // typically drives the scavenge rate. Large heaps can mean infrequent GC, | |
1384 // which in turn can mean large(r) numbers of objectmonitors in circulation. | |
1385 // This is an unfortunate aspect of this design. | |
1386 // | |
1387 | |
1878 | 1388 enum ManifestConstants { |
1389 ClearResponsibleAtSTW = 0, | |
1390 MaximumRecheckInterval = 1000 | |
1391 } ; | |
1587 | 1392 |
1393 // Deflate a single monitor if not in use | |
1394 // Return true if deflated, false if in use | |
1395 bool ObjectSynchronizer::deflate_monitor(ObjectMonitor* mid, oop obj, | |
1396 ObjectMonitor** FreeHeadp, ObjectMonitor** FreeTailp) { | |
1397 bool deflated; | |
1398 // Normal case ... The monitor is associated with obj. | |
1399 guarantee (obj->mark() == markOopDesc::encode(mid), "invariant") ; | |
1400 guarantee (mid == obj->mark()->monitor(), "invariant"); | |
1401 guarantee (mid->header()->is_neutral(), "invariant"); | |
1402 | |
1403 if (mid->is_busy()) { | |
1404 if (ClearResponsibleAtSTW) mid->_Responsible = NULL ; | |
1405 deflated = false; | |
1406 } else { | |
1407 // Deflate the monitor if it is no longer being used | |
1408 // It's idle - scavenge and return to the global free list | |
1409 // plain old deflation ... | |
1410 TEVENT (deflate_idle_monitors - scavenge1) ; | |
1411 if (TraceMonitorInflation) { | |
1412 if (obj->is_instance()) { | |
1413 ResourceMark rm; | |
1414 tty->print_cr("Deflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
1415 (intptr_t) obj, (intptr_t) obj->mark(), Klass::cast(obj->klass())->external_name()); | |
1416 } | |
1417 } | |
1418 | |
1419 // Restore the header back to obj | |
1420 obj->release_set_mark(mid->header()); | |
1421 mid->clear(); | |
1422 | |
1423 assert (mid->object() == NULL, "invariant") ; | |
1424 | |
1425 // Move the object to the working free list defined by FreeHead,FreeTail. | |
1426 if (*FreeHeadp == NULL) *FreeHeadp = mid; | |
1427 if (*FreeTailp != NULL) { | |
1428 ObjectMonitor * prevtail = *FreeTailp; | |
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1429 assert(prevtail->FreeNext == NULL, "cleaned up deflated?"); // TODO KK |
1587 | 1430 prevtail->FreeNext = mid; |
1431 } | |
1432 *FreeTailp = mid; | |
1433 deflated = true; | |
1434 } | |
1435 return deflated; | |
1436 } | |
1437 | |
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1438 // Caller acquires ListLock |
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1439 int ObjectSynchronizer::walk_monitor_list(ObjectMonitor** listheadp, |
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1440 ObjectMonitor** FreeHeadp, ObjectMonitor** FreeTailp) { |
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1441 ObjectMonitor* mid; |
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1442 ObjectMonitor* next; |
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1443 ObjectMonitor* curmidinuse = NULL; |
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1444 int deflatedcount = 0; |
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1445 |
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1446 for (mid = *listheadp; mid != NULL; ) { |
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1447 oop obj = (oop) mid->object(); |
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1448 bool deflated = false; |
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1449 if (obj != NULL) { |
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1450 deflated = deflate_monitor(mid, obj, FreeHeadp, FreeTailp); |
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1451 } |
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1452 if (deflated) { |
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1453 // extract from per-thread in-use-list |
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1454 if (mid == *listheadp) { |
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1455 *listheadp = mid->FreeNext; |
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1456 } else if (curmidinuse != NULL) { |
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1457 curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist |
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1458 } |
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1459 next = mid->FreeNext; |
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1460 mid->FreeNext = NULL; // This mid is current tail in the FreeHead list |
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1461 mid = next; |
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1462 deflatedcount++; |
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1463 } else { |
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1464 curmidinuse = mid; |
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1465 mid = mid->FreeNext; |
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1466 } |
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1467 } |
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1468 return deflatedcount; |
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1469 } |
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1470 |
0 | 1471 void ObjectSynchronizer::deflate_idle_monitors() { |
1472 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); | |
1473 int nInuse = 0 ; // currently associated with objects | |
1474 int nInCirculation = 0 ; // extant | |
1475 int nScavenged = 0 ; // reclaimed | |
1587 | 1476 bool deflated = false; |
0 | 1477 |
1478 ObjectMonitor * FreeHead = NULL ; // Local SLL of scavenged monitors | |
1479 ObjectMonitor * FreeTail = NULL ; | |
1480 | |
1587 | 1481 TEVENT (deflate_idle_monitors) ; |
1482 // Prevent omFlush from changing mids in Thread dtor's during deflation | |
1483 // And in case the vm thread is acquiring a lock during a safepoint | |
1484 // See e.g. 6320749 | |
1485 Thread::muxAcquire (&ListLock, "scavenge - return") ; | |
1486 | |
1487 if (MonitorInUseLists) { | |
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1488 int inUse = 0; |
1587 | 1489 for (JavaThread* cur = Threads::first(); cur != NULL; cur = cur->next()) { |
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1490 nInCirculation+= cur->omInUseCount; |
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1491 int deflatedcount = walk_monitor_list(cur->omInUseList_addr(), &FreeHead, &FreeTail); |
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1492 cur->omInUseCount-= deflatedcount; |
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1493 // verifyInUse(cur); |
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1494 nScavenged += deflatedcount; |
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1495 nInuse += cur->omInUseCount; |
1587 | 1496 } |
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1497 |
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1498 // For moribund threads, scan gOmInUseList |
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1499 if (gOmInUseList) { |
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1500 nInCirculation += gOmInUseCount; |
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1501 int deflatedcount = walk_monitor_list((ObjectMonitor **)&gOmInUseList, &FreeHead, &FreeTail); |
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1502 gOmInUseCount-= deflatedcount; |
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1503 nScavenged += deflatedcount; |
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1504 nInuse += gOmInUseCount; |
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1505 } |
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1506 |
1587 | 1507 } else for (ObjectMonitor* block = gBlockList; block != NULL; block = next(block)) { |
0 | 1508 // Iterate over all extant monitors - Scavenge all idle monitors. |
1509 assert(block->object() == CHAINMARKER, "must be a block header"); | |
1510 nInCirculation += _BLOCKSIZE ; | |
1511 for (int i = 1 ; i < _BLOCKSIZE; i++) { | |
1512 ObjectMonitor* mid = &block[i]; | |
1513 oop obj = (oop) mid->object(); | |
1514 | |
1515 if (obj == NULL) { | |
1516 // The monitor is not associated with an object. | |
1517 // The monitor should either be a thread-specific private | |
1518 // free list or the global free list. | |
1519 // obj == NULL IMPLIES mid->is_busy() == 0 | |
1520 guarantee (!mid->is_busy(), "invariant") ; | |
1521 continue ; | |
1522 } | |
1587 | 1523 deflated = deflate_monitor(mid, obj, &FreeHead, &FreeTail); |
1524 | |
1525 if (deflated) { | |
1526 mid->FreeNext = NULL ; | |
1527 nScavenged ++ ; | |
0 | 1528 } else { |
1587 | 1529 nInuse ++; |
0 | 1530 } |
1531 } | |
1532 } | |
1533 | |
1587 | 1534 MonitorFreeCount += nScavenged; |
1535 | |
1536 // Consider: audit gFreeList to ensure that MonitorFreeCount and list agree. | |
1537 | |
1878 | 1538 if (ObjectMonitor::Knob_Verbose) { |
1587 | 1539 ::printf ("Deflate: InCirc=%d InUse=%d Scavenged=%d ForceMonitorScavenge=%d : pop=%d free=%d\n", |
1540 nInCirculation, nInuse, nScavenged, ForceMonitorScavenge, | |
1541 MonitorPopulation, MonitorFreeCount) ; | |
1542 ::fflush(stdout) ; | |
1543 } | |
1544 | |
1545 ForceMonitorScavenge = 0; // Reset | |
1546 | |
0 | 1547 // Move the scavenged monitors back to the global free list. |
1548 if (FreeHead != NULL) { | |
1549 guarantee (FreeTail != NULL && nScavenged > 0, "invariant") ; | |
1550 assert (FreeTail->FreeNext == NULL, "invariant") ; | |
1551 // constant-time list splice - prepend scavenged segment to gFreeList | |
1552 FreeTail->FreeNext = gFreeList ; | |
1553 gFreeList = FreeHead ; | |
1554 } | |
1587 | 1555 Thread::muxRelease (&ListLock) ; |
0 | 1556 |
1878 | 1557 if (ObjectMonitor::_sync_Deflations != NULL) ObjectMonitor::_sync_Deflations->inc(nScavenged) ; |
1558 if (ObjectMonitor::_sync_MonExtant != NULL) ObjectMonitor::_sync_MonExtant ->set_value(nInCirculation); | |
0 | 1559 |
1560 // TODO: Add objectMonitor leak detection. | |
1561 // Audit/inventory the objectMonitors -- make sure they're all accounted for. | |
1562 GVars.stwRandom = os::random() ; | |
1563 GVars.stwCycle ++ ; | |
1564 } | |
1565 | |
1878 | 1566 // Monitor cleanup on JavaThread::exit |
0 | 1567 |
1878 | 1568 // Iterate through monitor cache and attempt to release thread's monitors |
1569 // Gives up on a particular monitor if an exception occurs, but continues | |
1570 // the overall iteration, swallowing the exception. | |
1571 class ReleaseJavaMonitorsClosure: public MonitorClosure { | |
1572 private: | |
1573 TRAPS; | |
0 | 1574 |
1878 | 1575 public: |
1576 ReleaseJavaMonitorsClosure(Thread* thread) : THREAD(thread) {} | |
1577 void do_monitor(ObjectMonitor* mid) { | |
1578 if (mid->owner() == THREAD) { | |
1579 (void)mid->complete_exit(CHECK); | |
0 | 1580 } |
1581 } | |
1878 | 1582 }; |
0 | 1583 |
1878 | 1584 // Release all inflated monitors owned by THREAD. Lightweight monitors are |
1585 // ignored. This is meant to be called during JNI thread detach which assumes | |
1586 // all remaining monitors are heavyweight. All exceptions are swallowed. | |
1587 // Scanning the extant monitor list can be time consuming. | |
1588 // A simple optimization is to add a per-thread flag that indicates a thread | |
1589 // called jni_monitorenter() during its lifetime. | |
0 | 1590 // |
1878 | 1591 // Instead of No_Savepoint_Verifier it might be cheaper to |
1592 // use an idiom of the form: | |
1593 // auto int tmp = SafepointSynchronize::_safepoint_counter ; | |
1594 // <code that must not run at safepoint> | |
1595 // guarantee (((tmp ^ _safepoint_counter) | (tmp & 1)) == 0) ; | |
1596 // Since the tests are extremely cheap we could leave them enabled | |
1597 // for normal product builds. | |
0 | 1598 |
1878 | 1599 void ObjectSynchronizer::release_monitors_owned_by_thread(TRAPS) { |
1600 assert(THREAD == JavaThread::current(), "must be current Java thread"); | |
1601 No_Safepoint_Verifier nsv ; | |
1602 ReleaseJavaMonitorsClosure rjmc(THREAD); | |
1603 Thread::muxAcquire(&ListLock, "release_monitors_owned_by_thread"); | |
1604 ObjectSynchronizer::monitors_iterate(&rjmc); | |
1605 Thread::muxRelease(&ListLock); | |
1606 THREAD->clear_pending_exception(); | |
0 | 1607 } |
1608 | |
1609 //------------------------------------------------------------------------------ | |
1610 // Non-product code | |
1611 | |
1612 #ifndef PRODUCT | |
1613 | |
1614 void ObjectSynchronizer::trace_locking(Handle locking_obj, bool is_compiled, | |
1615 bool is_method, bool is_locking) { | |
1616 // Don't know what to do here | |
1617 } | |
1618 | |
1619 // Verify all monitors in the monitor cache, the verification is weak. | |
1620 void ObjectSynchronizer::verify() { | |
1621 ObjectMonitor* block = gBlockList; | |
1622 ObjectMonitor* mid; | |
1623 while (block) { | |
1624 assert(block->object() == CHAINMARKER, "must be a block header"); | |
1625 for (int i = 1; i < _BLOCKSIZE; i++) { | |
1626 mid = block + i; | |
1627 oop object = (oop) mid->object(); | |
1628 if (object != NULL) { | |
1629 mid->verify(); | |
1630 } | |
1631 } | |
1632 block = (ObjectMonitor*) block->FreeNext; | |
1633 } | |
1634 } | |
1635 | |
1636 // Check if monitor belongs to the monitor cache | |
1637 // The list is grow-only so it's *relatively* safe to traverse | |
1638 // the list of extant blocks without taking a lock. | |
1639 | |
1640 int ObjectSynchronizer::verify_objmon_isinpool(ObjectMonitor *monitor) { | |
1641 ObjectMonitor* block = gBlockList; | |
1642 | |
1643 while (block) { | |
1644 assert(block->object() == CHAINMARKER, "must be a block header"); | |
1645 if (monitor > &block[0] && monitor < &block[_BLOCKSIZE]) { | |
1646 address mon = (address) monitor; | |
1647 address blk = (address) block; | |
1648 size_t diff = mon - blk; | |
1649 assert((diff % sizeof(ObjectMonitor)) == 0, "check"); | |
1650 return 1; | |
1651 } | |
1652 block = (ObjectMonitor*) block->FreeNext; | |
1653 } | |
1654 return 0; | |
1655 } | |
1656 | |
1657 #endif |