Mercurial > hg > graal-compiler
annotate src/share/vm/runtime/synchronizer.cpp @ 18096:ca6d25be853b jdk8u25-b13
8044269: Analysis of archive files.
Summary: Add checksum verification.
Reviewed-by: iklam, dholmes, mschoene
| author | jiangli |
|---|---|
| date | Tue, 12 Aug 2014 17:46:16 -0400 |
| parents | 78bbf4d43a14 |
| children | 52b4284cb496 |
| rev | line source |
|---|---|
| 0 | 1 /* |
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2 * Copyright (c) 1998, 2014, 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" | |
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39 #include "runtime/thread.inline.hpp" |
| 1972 | 40 #include "utilities/dtrace.hpp" |
| 41 #include "utilities/events.hpp" | |
| 42 #include "utilities/preserveException.hpp" | |
| 43 #ifdef TARGET_OS_FAMILY_linux | |
| 44 # include "os_linux.inline.hpp" | |
| 45 #endif | |
| 46 #ifdef TARGET_OS_FAMILY_solaris | |
| 47 # include "os_solaris.inline.hpp" | |
| 48 #endif | |
| 49 #ifdef TARGET_OS_FAMILY_windows | |
| 50 # include "os_windows.inline.hpp" | |
| 51 #endif | |
| 3960 | 52 #ifdef TARGET_OS_FAMILY_bsd |
| 53 # include "os_bsd.inline.hpp" | |
| 54 #endif | |
| 0 | 55 |
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56 #if defined(__GNUC__) && !defined(PPC64) |
| 0 | 57 // Need to inhibit inlining for older versions of GCC to avoid build-time failures |
| 58 #define ATTR __attribute__((noinline)) | |
| 59 #else | |
| 60 #define ATTR | |
| 61 #endif | |
| 62 | |
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63 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC |
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64 |
| 0 | 65 // The "core" versions of monitor enter and exit reside in this file. |
| 66 // The interpreter and compilers contain specialized transliterated | |
| 67 // variants of the enter-exit fast-path operations. See i486.ad fast_lock(), | |
| 68 // for instance. If you make changes here, make sure to modify the | |
| 69 // interpreter, and both C1 and C2 fast-path inline locking code emission. | |
| 70 // | |
| 71 // | |
| 72 // ----------------------------------------------------------------------------- | |
| 73 | |
| 74 #ifdef DTRACE_ENABLED | |
| 75 | |
| 76 // Only bother with this argument setup if dtrace is available | |
| 77 // TODO-FIXME: probes should not fire when caller is _blocked. assert() accordingly. | |
| 78 | |
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79 #define DTRACE_MONITOR_PROBE_COMMON(obj, thread) \ |
| 0 | 80 char* bytes = NULL; \ |
| 81 int len = 0; \ | |
| 82 jlong jtid = SharedRuntime::get_java_tid(thread); \ | |
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83 Symbol* klassname = ((oop)(obj))->klass()->name(); \ |
| 0 | 84 if (klassname != NULL) { \ |
| 85 bytes = (char*)klassname->bytes(); \ | |
| 86 len = klassname->utf8_length(); \ | |
| 87 } | |
| 88 | |
| 4006 | 89 #ifndef USDT2 |
| 90 HS_DTRACE_PROBE_DECL5(hotspot, monitor__wait, | |
| 91 jlong, uintptr_t, char*, int, long); | |
| 92 HS_DTRACE_PROBE_DECL4(hotspot, monitor__waited, | |
| 93 jlong, uintptr_t, char*, int); | |
| 94 | |
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95 #define DTRACE_MONITOR_WAIT_PROBE(monitor, obj, thread, millis) \ |
| 0 | 96 { \ |
| 97 if (DTraceMonitorProbes) { \ | |
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98 DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ |
| 0 | 99 HS_DTRACE_PROBE5(hotspot, monitor__wait, jtid, \ |
| 100 (monitor), bytes, len, (millis)); \ | |
| 101 } \ | |
| 102 } | |
| 103 | |
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104 #define DTRACE_MONITOR_PROBE(probe, monitor, obj, thread) \ |
| 0 | 105 { \ |
| 106 if (DTraceMonitorProbes) { \ | |
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107 DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ |
| 0 | 108 HS_DTRACE_PROBE4(hotspot, monitor__##probe, jtid, \ |
| 109 (uintptr_t)(monitor), bytes, len); \ | |
| 110 } \ | |
| 111 } | |
| 112 | |
| 4006 | 113 #else /* USDT2 */ |
| 114 | |
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115 #define DTRACE_MONITOR_WAIT_PROBE(monitor, obj, thread, millis) \ |
| 4006 | 116 { \ |
| 117 if (DTraceMonitorProbes) { \ | |
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118 DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ |
| 4006 | 119 HOTSPOT_MONITOR_WAIT(jtid, \ |
| 120 (uintptr_t)(monitor), bytes, len, (millis)); \ | |
| 121 } \ | |
| 122 } | |
| 123 | |
| 124 #define HOTSPOT_MONITOR_PROBE_waited HOTSPOT_MONITOR_PROBE_WAITED | |
| 125 | |
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126 #define DTRACE_MONITOR_PROBE(probe, monitor, obj, thread) \ |
| 4006 | 127 { \ |
| 128 if (DTraceMonitorProbes) { \ | |
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129 DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ |
| 4006 | 130 HOTSPOT_MONITOR_PROBE_##probe(jtid, /* probe = waited */ \ |
| 131 (uintptr_t)(monitor), bytes, len); \ | |
| 132 } \ | |
| 133 } | |
| 134 | |
| 135 #endif /* USDT2 */ | |
| 0 | 136 #else // ndef DTRACE_ENABLED |
| 137 | |
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138 #define DTRACE_MONITOR_WAIT_PROBE(obj, thread, millis, mon) {;} |
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139 #define DTRACE_MONITOR_PROBE(probe, obj, thread, mon) {;} |
| 0 | 140 |
| 141 #endif // ndef DTRACE_ENABLED | |
| 142 | |
| 1878 | 143 // This exists only as a workaround of dtrace bug 6254741 |
| 144 int dtrace_waited_probe(ObjectMonitor* monitor, Handle obj, Thread* thr) { | |
| 145 DTRACE_MONITOR_PROBE(waited, monitor, obj(), thr); | |
| 146 return 0; | |
| 147 } | |
| 148 | |
| 149 #define NINFLATIONLOCKS 256 | |
| 150 static volatile intptr_t InflationLocks [NINFLATIONLOCKS] ; | |
| 151 | |
| 152 ObjectMonitor * ObjectSynchronizer::gBlockList = NULL ; | |
| 153 ObjectMonitor * volatile ObjectSynchronizer::gFreeList = NULL ; | |
| 154 ObjectMonitor * volatile ObjectSynchronizer::gOmInUseList = NULL ; | |
| 155 int ObjectSynchronizer::gOmInUseCount = 0; | |
| 156 static volatile intptr_t ListLock = 0 ; // protects global monitor free-list cache | |
| 157 static volatile int MonitorFreeCount = 0 ; // # on gFreeList | |
| 158 static volatile int MonitorPopulation = 0 ; // # Extant -- in circulation | |
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159 #define CHAINMARKER (cast_to_oop<intptr_t>(-1)) |
| 1878 | 160 |
| 161 // ----------------------------------------------------------------------------- | |
| 162 // Fast Monitor Enter/Exit | |
| 163 // This the fast monitor enter. The interpreter and compiler use | |
| 164 // some assembly copies of this code. Make sure update those code | |
| 165 // if the following function is changed. The implementation is | |
| 166 // extremely sensitive to race condition. Be careful. | |
| 167 | |
| 168 void ObjectSynchronizer::fast_enter(Handle obj, BasicLock* lock, bool attempt_rebias, TRAPS) { | |
| 169 if (UseBiasedLocking) { | |
| 170 if (!SafepointSynchronize::is_at_safepoint()) { | |
| 171 BiasedLocking::Condition cond = BiasedLocking::revoke_and_rebias(obj, attempt_rebias, THREAD); | |
| 172 if (cond == BiasedLocking::BIAS_REVOKED_AND_REBIASED) { | |
| 173 return; | |
| 174 } | |
| 175 } else { | |
| 176 assert(!attempt_rebias, "can not rebias toward VM thread"); | |
| 177 BiasedLocking::revoke_at_safepoint(obj); | |
| 178 } | |
| 179 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 180 } | |
| 181 | |
| 182 slow_enter (obj, lock, THREAD) ; | |
| 183 } | |
| 184 | |
| 185 void ObjectSynchronizer::fast_exit(oop object, BasicLock* lock, TRAPS) { | |
| 186 assert(!object->mark()->has_bias_pattern(), "should not see bias pattern here"); | |
| 187 // if displaced header is null, the previous enter is recursive enter, no-op | |
| 188 markOop dhw = lock->displaced_header(); | |
| 189 markOop mark ; | |
| 190 if (dhw == NULL) { | |
| 191 // Recursive stack-lock. | |
| 192 // Diagnostics -- Could be: stack-locked, inflating, inflated. | |
| 193 mark = object->mark() ; | |
| 194 assert (!mark->is_neutral(), "invariant") ; | |
| 195 if (mark->has_locker() && mark != markOopDesc::INFLATING()) { | |
| 196 assert(THREAD->is_lock_owned((address)mark->locker()), "invariant") ; | |
| 197 } | |
| 198 if (mark->has_monitor()) { | |
| 199 ObjectMonitor * m = mark->monitor() ; | |
| 200 assert(((oop)(m->object()))->mark() == mark, "invariant") ; | |
| 201 assert(m->is_entered(THREAD), "invariant") ; | |
| 202 } | |
| 203 return ; | |
| 204 } | |
| 205 | |
| 206 mark = object->mark() ; | |
| 0 | 207 |
| 1878 | 208 // If the object is stack-locked by the current thread, try to |
| 209 // swing the displaced header from the box back to the mark. | |
| 210 if (mark == (markOop) lock) { | |
| 211 assert (dhw->is_neutral(), "invariant") ; | |
| 212 if ((markOop) Atomic::cmpxchg_ptr (dhw, object->mark_addr(), mark) == mark) { | |
| 213 TEVENT (fast_exit: release stacklock) ; | |
| 214 return; | |
| 215 } | |
| 216 } | |
| 217 | |
| 10405 | 218 ObjectSynchronizer::inflate(THREAD, object)->exit (true, THREAD) ; |
| 1878 | 219 } |
| 220 | |
| 221 // ----------------------------------------------------------------------------- | |
| 222 // Interpreter/Compiler Slow Case | |
| 223 // This routine is used to handle interpreter/compiler slow case | |
| 224 // We don't need to use fast path here, because it must have been | |
| 225 // failed in the interpreter/compiler code. | |
| 226 void ObjectSynchronizer::slow_enter(Handle obj, BasicLock* lock, TRAPS) { | |
| 227 markOop mark = obj->mark(); | |
| 228 assert(!mark->has_bias_pattern(), "should not see bias pattern here"); | |
| 229 | |
| 230 if (mark->is_neutral()) { | |
| 231 // Anticipate successful CAS -- the ST of the displaced mark must | |
| 232 // be visible <= the ST performed by the CAS. | |
| 233 lock->set_displaced_header(mark); | |
| 234 if (mark == (markOop) Atomic::cmpxchg_ptr(lock, obj()->mark_addr(), mark)) { | |
| 235 TEVENT (slow_enter: release stacklock) ; | |
| 236 return ; | |
| 237 } | |
| 238 // Fall through to inflate() ... | |
| 239 } else | |
| 240 if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { | |
| 241 assert(lock != mark->locker(), "must not re-lock the same lock"); | |
| 242 assert(lock != (BasicLock*)obj->mark(), "don't relock with same BasicLock"); | |
| 243 lock->set_displaced_header(NULL); | |
| 244 return; | |
| 245 } | |
| 246 | |
| 247 #if 0 | |
| 248 // The following optimization isn't particularly useful. | |
| 249 if (mark->has_monitor() && mark->monitor()->is_entered(THREAD)) { | |
| 250 lock->set_displaced_header (NULL) ; | |
| 251 return ; | |
| 252 } | |
| 253 #endif | |
| 254 | |
| 255 // The object header will never be displaced to this lock, | |
| 256 // so it does not matter what the value is, except that it | |
| 257 // must be non-zero to avoid looking like a re-entrant lock, | |
| 258 // and must not look locked either. | |
| 259 lock->set_displaced_header(markOopDesc::unused_mark()); | |
| 260 ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD); | |
| 261 } | |
| 262 | |
| 263 // This routine is used to handle interpreter/compiler slow case | |
| 264 // We don't need to use fast path here, because it must have | |
| 265 // failed in the interpreter/compiler code. Simply use the heavy | |
| 266 // weight monitor should be ok, unless someone find otherwise. | |
| 267 void ObjectSynchronizer::slow_exit(oop object, BasicLock* lock, TRAPS) { | |
| 268 fast_exit (object, lock, THREAD) ; | |
| 269 } | |
| 270 | |
| 271 // ----------------------------------------------------------------------------- | |
| 272 // Class Loader support to workaround deadlocks on the class loader lock objects | |
| 273 // Also used by GC | |
| 274 // complete_exit()/reenter() are used to wait on a nested lock | |
| 275 // i.e. to give up an outer lock completely and then re-enter | |
| 276 // Used when holding nested locks - lock acquisition order: lock1 then lock2 | |
| 277 // 1) complete_exit lock1 - saving recursion count | |
| 278 // 2) wait on lock2 | |
| 279 // 3) when notified on lock2, unlock lock2 | |
| 280 // 4) reenter lock1 with original recursion count | |
| 281 // 5) lock lock2 | |
| 282 // NOTE: must use heavy weight monitor to handle complete_exit/reenter() | |
| 283 intptr_t ObjectSynchronizer::complete_exit(Handle obj, TRAPS) { | |
| 284 TEVENT (complete_exit) ; | |
| 285 if (UseBiasedLocking) { | |
| 286 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
| 287 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 0 | 288 } |
| 289 | |
| 1878 | 290 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); |
| 291 | |
| 292 return monitor->complete_exit(THREAD); | |
| 293 } | |
| 294 | |
| 295 // NOTE: must use heavy weight monitor to handle complete_exit/reenter() | |
| 296 void ObjectSynchronizer::reenter(Handle obj, intptr_t recursion, TRAPS) { | |
| 297 TEVENT (reenter) ; | |
| 298 if (UseBiasedLocking) { | |
| 299 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
| 300 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 301 } | |
| 302 | |
| 303 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); | |
| 304 | |
| 305 monitor->reenter(recursion, THREAD); | |
| 306 } | |
| 307 // ----------------------------------------------------------------------------- | |
| 308 // JNI locks on java objects | |
| 309 // NOTE: must use heavy weight monitor to handle jni monitor enter | |
| 310 void ObjectSynchronizer::jni_enter(Handle obj, TRAPS) { // possible entry from jni enter | |
| 311 // the current locking is from JNI instead of Java code | |
| 312 TEVENT (jni_enter) ; | |
| 313 if (UseBiasedLocking) { | |
| 314 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
| 315 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 316 } | |
| 317 THREAD->set_current_pending_monitor_is_from_java(false); | |
| 318 ObjectSynchronizer::inflate(THREAD, obj())->enter(THREAD); | |
| 319 THREAD->set_current_pending_monitor_is_from_java(true); | |
| 320 } | |
| 321 | |
| 322 // NOTE: must use heavy weight monitor to handle jni monitor enter | |
| 323 bool ObjectSynchronizer::jni_try_enter(Handle obj, Thread* THREAD) { | |
| 324 if (UseBiasedLocking) { | |
| 325 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
| 326 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 0 | 327 } |
| 328 | |
| 1878 | 329 ObjectMonitor* monitor = ObjectSynchronizer::inflate_helper(obj()); |
| 330 return monitor->try_enter(THREAD); | |
| 331 } | |
| 332 | |
| 333 | |
| 334 // NOTE: must use heavy weight monitor to handle jni monitor exit | |
| 335 void ObjectSynchronizer::jni_exit(oop obj, Thread* THREAD) { | |
| 336 TEVENT (jni_exit) ; | |
| 337 if (UseBiasedLocking) { | |
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338 Handle h_obj(THREAD, obj); |
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339 BiasedLocking::revoke_and_rebias(h_obj, false, THREAD); |
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340 obj = h_obj(); |
| 1878 | 341 } |
| 342 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 343 | |
| 344 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj); | |
| 345 // If this thread has locked the object, exit the monitor. Note: can't use | |
| 346 // monitor->check(CHECK); must exit even if an exception is pending. | |
| 347 if (monitor->check(THREAD)) { | |
| 10405 | 348 monitor->exit(true, THREAD); |
| 0 | 349 } |
| 1878 | 350 } |
| 351 | |
| 352 // ----------------------------------------------------------------------------- | |
| 353 // Internal VM locks on java objects | |
| 354 // standard constructor, allows locking failures | |
| 355 ObjectLocker::ObjectLocker(Handle obj, Thread* thread, bool doLock) { | |
| 356 _dolock = doLock; | |
| 357 _thread = thread; | |
| 358 debug_only(if (StrictSafepointChecks) _thread->check_for_valid_safepoint_state(false);) | |
| 359 _obj = obj; | |
| 0 | 360 |
| 1878 | 361 if (_dolock) { |
| 362 TEVENT (ObjectLocker) ; | |
| 363 | |
| 364 ObjectSynchronizer::fast_enter(_obj, &_lock, false, _thread); | |
| 365 } | |
| 366 } | |
| 367 | |
| 368 ObjectLocker::~ObjectLocker() { | |
| 369 if (_dolock) { | |
| 370 ObjectSynchronizer::fast_exit(_obj(), &_lock, _thread); | |
| 371 } | |
| 372 } | |
| 0 | 373 |
| 374 | |
| 1878 | 375 // ----------------------------------------------------------------------------- |
| 376 // Wait/Notify/NotifyAll | |
| 377 // NOTE: must use heavy weight monitor to handle wait() | |
| 378 void ObjectSynchronizer::wait(Handle obj, jlong millis, TRAPS) { | |
| 379 if (UseBiasedLocking) { | |
| 380 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
| 381 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 382 } | |
| 383 if (millis < 0) { | |
| 384 TEVENT (wait - throw IAX) ; | |
| 385 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); | |
| 386 } | |
| 387 ObjectMonitor* monitor = ObjectSynchronizer::inflate(THREAD, obj()); | |
| 388 DTRACE_MONITOR_WAIT_PROBE(monitor, obj(), THREAD, millis); | |
| 389 monitor->wait(millis, true, THREAD); | |
| 390 | |
| 391 /* This dummy call is in place to get around dtrace bug 6254741. Once | |
| 392 that's fixed we can uncomment the following line and remove the call */ | |
| 393 // DTRACE_MONITOR_PROBE(waited, monitor, obj(), THREAD); | |
| 394 dtrace_waited_probe(monitor, obj, THREAD); | |
| 395 } | |
| 0 | 396 |
| 1878 | 397 void ObjectSynchronizer::waitUninterruptibly (Handle obj, jlong millis, TRAPS) { |
| 398 if (UseBiasedLocking) { | |
| 399 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
| 400 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 401 } | |
| 402 if (millis < 0) { | |
| 403 TEVENT (wait - throw IAX) ; | |
| 404 THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); | |
| 405 } | |
| 406 ObjectSynchronizer::inflate(THREAD, obj()) -> wait(millis, false, THREAD) ; | |
| 407 } | |
| 408 | |
| 409 void ObjectSynchronizer::notify(Handle obj, TRAPS) { | |
| 410 if (UseBiasedLocking) { | |
| 411 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
| 412 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 413 } | |
| 0 | 414 |
| 1878 | 415 markOop mark = obj->mark(); |
| 416 if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { | |
| 417 return; | |
| 418 } | |
| 419 ObjectSynchronizer::inflate(THREAD, obj())->notify(THREAD); | |
| 420 } | |
| 0 | 421 |
| 1878 | 422 // NOTE: see comment of notify() |
| 423 void ObjectSynchronizer::notifyall(Handle obj, TRAPS) { | |
| 424 if (UseBiasedLocking) { | |
| 425 BiasedLocking::revoke_and_rebias(obj, false, THREAD); | |
| 426 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 427 } | |
| 428 | |
| 429 markOop mark = obj->mark(); | |
| 430 if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) { | |
| 431 return; | |
| 432 } | |
| 433 ObjectSynchronizer::inflate(THREAD, obj())->notifyAll(THREAD); | |
| 434 } | |
| 435 | |
| 436 // ----------------------------------------------------------------------------- | |
| 437 // Hash Code handling | |
| 438 // | |
| 0 | 439 // Performance concern: |
| 440 // OrderAccess::storestore() calls release() which STs 0 into the global volatile | |
| 441 // OrderAccess::Dummy variable. This store is unnecessary for correctness. | |
| 442 // Many threads STing into a common location causes considerable cache migration | |
| 443 // or "sloshing" on large SMP system. As such, I avoid using OrderAccess::storestore() | |
| 444 // until it's repaired. In some cases OrderAccess::fence() -- which incurs local | |
| 445 // latency on the executing processor -- is a better choice as it scales on SMP | |
| 446 // systems. See http://blogs.sun.com/dave/entry/biased_locking_in_hotspot for a | |
| 447 // discussion of coherency costs. Note that all our current reference platforms | |
| 448 // provide strong ST-ST order, so the issue is moot on IA32, x64, and SPARC. | |
| 449 // | |
| 450 // As a general policy we use "volatile" to control compiler-based reordering | |
| 451 // and explicit fences (barriers) to control for architectural reordering performed | |
| 452 // by the CPU(s) or platform. | |
| 453 | |
| 454 struct SharedGlobals { | |
| 455 // These are highly shared mostly-read variables. | |
| 456 // To avoid false-sharing they need to be the sole occupants of a $ line. | |
| 457 double padPrefix [8]; | |
| 458 volatile int stwRandom ; | |
| 459 volatile int stwCycle ; | |
| 460 | |
| 461 // Hot RW variables -- Sequester to avoid false-sharing | |
| 462 double padSuffix [16]; | |
| 463 volatile int hcSequence ; | |
| 464 double padFinal [8] ; | |
| 465 } ; | |
| 466 | |
| 467 static SharedGlobals GVars ; | |
| 1587 | 468 static int MonitorScavengeThreshold = 1000000 ; |
| 469 static volatile int ForceMonitorScavenge = 0 ; // Scavenge required and pending | |
| 0 | 470 |
| 1878 | 471 static markOop ReadStableMark (oop obj) { |
| 472 markOop mark = obj->mark() ; | |
| 473 if (!mark->is_being_inflated()) { | |
| 474 return mark ; // normal fast-path return | |
| 475 } | |
| 0 | 476 |
| 1878 | 477 int its = 0 ; |
| 478 for (;;) { | |
| 479 markOop mark = obj->mark() ; | |
| 480 if (!mark->is_being_inflated()) { | |
| 481 return mark ; // normal fast-path return | |
| 482 } | |
| 483 | |
| 484 // The object is being inflated by some other thread. | |
| 485 // The caller of ReadStableMark() must wait for inflation to complete. | |
| 486 // Avoid live-lock | |
| 487 // TODO: consider calling SafepointSynchronize::do_call_back() while | |
| 488 // spinning to see if there's a safepoint pending. If so, immediately | |
| 489 // yielding or blocking would be appropriate. Avoid spinning while | |
| 490 // there is a safepoint pending. | |
| 491 // TODO: add inflation contention performance counters. | |
| 492 // TODO: restrict the aggregate number of spinners. | |
| 0 | 493 |
| 1878 | 494 ++its ; |
| 495 if (its > 10000 || !os::is_MP()) { | |
| 496 if (its & 1) { | |
| 497 os::NakedYield() ; | |
| 498 TEVENT (Inflate: INFLATING - yield) ; | |
| 499 } else { | |
| 500 // Note that the following code attenuates the livelock problem but is not | |
| 501 // a complete remedy. A more complete solution would require that the inflating | |
| 502 // thread hold the associated inflation lock. The following code simply restricts | |
| 503 // the number of spinners to at most one. We'll have N-2 threads blocked | |
| 504 // on the inflationlock, 1 thread holding the inflation lock and using | |
| 505 // a yield/park strategy, and 1 thread in the midst of inflation. | |
| 506 // A more refined approach would be to change the encoding of INFLATING | |
| 507 // to allow encapsulation of a native thread pointer. Threads waiting for | |
| 508 // inflation to complete would use CAS to push themselves onto a singly linked | |
| 509 // list rooted at the markword. Once enqueued, they'd loop, checking a per-thread flag | |
| 510 // and calling park(). When inflation was complete the thread that accomplished inflation | |
| 511 // would detach the list and set the markword to inflated with a single CAS and | |
| 512 // then for each thread on the list, set the flag and unpark() the thread. | |
| 513 // This is conceptually similar to muxAcquire-muxRelease, except that muxRelease | |
| 514 // wakes at most one thread whereas we need to wake the entire list. | |
|
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515 int ix = (cast_from_oop<intptr_t>(obj) >> 5) & (NINFLATIONLOCKS-1) ; |
| 1878 | 516 int YieldThenBlock = 0 ; |
| 517 assert (ix >= 0 && ix < NINFLATIONLOCKS, "invariant") ; | |
| 518 assert ((NINFLATIONLOCKS & (NINFLATIONLOCKS-1)) == 0, "invariant") ; | |
| 519 Thread::muxAcquire (InflationLocks + ix, "InflationLock") ; | |
| 520 while (obj->mark() == markOopDesc::INFLATING()) { | |
| 521 // Beware: NakedYield() is advisory and has almost no effect on some platforms | |
| 522 // so we periodically call Self->_ParkEvent->park(1). | |
| 523 // We use a mixed spin/yield/block mechanism. | |
| 524 if ((YieldThenBlock++) >= 16) { | |
| 525 Thread::current()->_ParkEvent->park(1) ; | |
| 526 } else { | |
| 527 os::NakedYield() ; | |
| 528 } | |
| 529 } | |
| 530 Thread::muxRelease (InflationLocks + ix ) ; | |
| 531 TEVENT (Inflate: INFLATING - yield/park) ; | |
| 532 } | |
| 533 } else { | |
| 534 SpinPause() ; // SMP-polite spinning | |
| 535 } | |
| 536 } | |
| 537 } | |
| 0 | 538 |
| 539 // hashCode() generation : | |
| 540 // | |
| 541 // Possibilities: | |
| 542 // * MD5Digest of {obj,stwRandom} | |
| 543 // * CRC32 of {obj,stwRandom} or any linear-feedback shift register function. | |
| 544 // * A DES- or AES-style SBox[] mechanism | |
| 545 // * One of the Phi-based schemes, such as: | |
| 546 // 2654435761 = 2^32 * Phi (golden ratio) | |
| 547 // HashCodeValue = ((uintptr_t(obj) >> 3) * 2654435761) ^ GVars.stwRandom ; | |
| 548 // * A variation of Marsaglia's shift-xor RNG scheme. | |
| 549 // * (obj ^ stwRandom) is appealing, but can result | |
| 550 // in undesirable regularity in the hashCode values of adjacent objects | |
| 551 // (objects allocated back-to-back, in particular). This could potentially | |
| 552 // result in hashtable collisions and reduced hashtable efficiency. | |
| 553 // There are simple ways to "diffuse" the middle address bits over the | |
| 554 // generated hashCode values: | |
| 555 // | |
| 556 | |
| 557 static inline intptr_t get_next_hash(Thread * Self, oop obj) { | |
| 558 intptr_t value = 0 ; | |
| 559 if (hashCode == 0) { | |
| 560 // This form uses an unguarded global Park-Miller RNG, | |
| 561 // so it's possible for two threads to race and generate the same RNG. | |
| 562 // On MP system we'll have lots of RW access to a global, so the | |
| 563 // mechanism induces lots of coherency traffic. | |
| 564 value = os::random() ; | |
| 565 } else | |
| 566 if (hashCode == 1) { | |
| 567 // This variation has the property of being stable (idempotent) | |
| 568 // between STW operations. This can be useful in some of the 1-0 | |
| 569 // synchronization schemes. | |
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570 intptr_t addrBits = cast_from_oop<intptr_t>(obj) >> 3 ; |
| 0 | 571 value = addrBits ^ (addrBits >> 5) ^ GVars.stwRandom ; |
| 572 } else | |
| 573 if (hashCode == 2) { | |
| 574 value = 1 ; // for sensitivity testing | |
| 575 } else | |
| 576 if (hashCode == 3) { | |
| 577 value = ++GVars.hcSequence ; | |
| 578 } else | |
| 579 if (hashCode == 4) { | |
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580 value = cast_from_oop<intptr_t>(obj) ; |
| 0 | 581 } else { |
| 582 // Marsaglia's xor-shift scheme with thread-specific state | |
| 583 // This is probably the best overall implementation -- we'll | |
| 584 // likely make this the default in future releases. | |
| 585 unsigned t = Self->_hashStateX ; | |
| 586 t ^= (t << 11) ; | |
| 587 Self->_hashStateX = Self->_hashStateY ; | |
| 588 Self->_hashStateY = Self->_hashStateZ ; | |
| 589 Self->_hashStateZ = Self->_hashStateW ; | |
| 590 unsigned v = Self->_hashStateW ; | |
| 591 v = (v ^ (v >> 19)) ^ (t ^ (t >> 8)) ; | |
| 592 Self->_hashStateW = v ; | |
| 593 value = v ; | |
| 594 } | |
| 595 | |
| 596 value &= markOopDesc::hash_mask; | |
| 597 if (value == 0) value = 0xBAD ; | |
| 598 assert (value != markOopDesc::no_hash, "invariant") ; | |
| 599 TEVENT (hashCode: GENERATE) ; | |
| 600 return value; | |
| 601 } | |
| 1878 | 602 // |
| 603 intptr_t ObjectSynchronizer::FastHashCode (Thread * Self, oop obj) { | |
| 604 if (UseBiasedLocking) { | |
| 605 // NOTE: many places throughout the JVM do not expect a safepoint | |
| 606 // to be taken here, in particular most operations on perm gen | |
| 607 // objects. However, we only ever bias Java instances and all of | |
| 608 // the call sites of identity_hash that might revoke biases have | |
| 609 // been checked to make sure they can handle a safepoint. The | |
| 610 // added check of the bias pattern is to avoid useless calls to | |
| 611 // thread-local storage. | |
| 612 if (obj->mark()->has_bias_pattern()) { | |
| 613 // Box and unbox the raw reference just in case we cause a STW safepoint. | |
| 614 Handle hobj (Self, obj) ; | |
| 615 // Relaxing assertion for bug 6320749. | |
| 616 assert (Universe::verify_in_progress() || | |
| 617 !SafepointSynchronize::is_at_safepoint(), | |
| 618 "biases should not be seen by VM thread here"); | |
| 619 BiasedLocking::revoke_and_rebias(hobj, false, JavaThread::current()); | |
| 620 obj = hobj() ; | |
| 621 assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 622 } | |
| 623 } | |
| 0 | 624 |
| 1878 | 625 // hashCode() is a heap mutator ... |
| 626 // Relaxing assertion for bug 6320749. | |
| 627 assert (Universe::verify_in_progress() || | |
| 628 !SafepointSynchronize::is_at_safepoint(), "invariant") ; | |
| 629 assert (Universe::verify_in_progress() || | |
| 630 Self->is_Java_thread() , "invariant") ; | |
| 631 assert (Universe::verify_in_progress() || | |
| 632 ((JavaThread *)Self)->thread_state() != _thread_blocked, "invariant") ; | |
| 633 | |
| 634 ObjectMonitor* monitor = NULL; | |
| 635 markOop temp, test; | |
| 636 intptr_t hash; | |
| 637 markOop mark = ReadStableMark (obj); | |
| 638 | |
| 639 // object should remain ineligible for biased locking | |
| 640 assert (!mark->has_bias_pattern(), "invariant") ; | |
| 641 | |
| 642 if (mark->is_neutral()) { | |
| 643 hash = mark->hash(); // this is a normal header | |
| 644 if (hash) { // if it has hash, just return it | |
| 645 return hash; | |
| 646 } | |
| 647 hash = get_next_hash(Self, obj); // allocate a new hash code | |
| 648 temp = mark->copy_set_hash(hash); // merge the hash code into header | |
| 649 // use (machine word version) atomic operation to install the hash | |
| 650 test = (markOop) Atomic::cmpxchg_ptr(temp, obj->mark_addr(), mark); | |
| 651 if (test == mark) { | |
| 652 return hash; | |
| 653 } | |
| 654 // If atomic operation failed, we must inflate the header | |
| 655 // into heavy weight monitor. We could add more code here | |
| 656 // for fast path, but it does not worth the complexity. | |
| 657 } else if (mark->has_monitor()) { | |
| 658 monitor = mark->monitor(); | |
| 659 temp = monitor->header(); | |
| 660 assert (temp->is_neutral(), "invariant") ; | |
| 661 hash = temp->hash(); | |
| 662 if (hash) { | |
| 663 return hash; | |
| 664 } | |
| 665 // Skip to the following code to reduce code size | |
| 666 } else if (Self->is_lock_owned((address)mark->locker())) { | |
| 667 temp = mark->displaced_mark_helper(); // this is a lightweight monitor owned | |
| 668 assert (temp->is_neutral(), "invariant") ; | |
| 669 hash = temp->hash(); // by current thread, check if the displaced | |
| 670 if (hash) { // header contains hash code | |
| 671 return hash; | |
| 672 } | |
| 673 // WARNING: | |
| 674 // The displaced header is strictly immutable. | |
| 675 // It can NOT be changed in ANY cases. So we have | |
| 676 // to inflate the header into heavyweight monitor | |
| 677 // even the current thread owns the lock. The reason | |
| 678 // is the BasicLock (stack slot) will be asynchronously | |
| 679 // read by other threads during the inflate() function. | |
| 680 // Any change to stack may not propagate to other threads | |
| 681 // correctly. | |
| 682 } | |
| 683 | |
| 684 // Inflate the monitor to set hash code | |
| 685 monitor = ObjectSynchronizer::inflate(Self, obj); | |
| 686 // Load displaced header and check it has hash code | |
| 687 mark = monitor->header(); | |
| 688 assert (mark->is_neutral(), "invariant") ; | |
| 689 hash = mark->hash(); | |
| 690 if (hash == 0) { | |
| 691 hash = get_next_hash(Self, obj); | |
| 692 temp = mark->copy_set_hash(hash); // merge hash code into header | |
| 693 assert (temp->is_neutral(), "invariant") ; | |
| 694 test = (markOop) Atomic::cmpxchg_ptr(temp, monitor, mark); | |
| 695 if (test != mark) { | |
| 696 // The only update to the header in the monitor (outside GC) | |
| 697 // is install the hash code. If someone add new usage of | |
| 698 // displaced header, please update this code | |
| 699 hash = test->hash(); | |
| 700 assert (test->is_neutral(), "invariant") ; | |
| 701 assert (hash != 0, "Trivial unexpected object/monitor header usage."); | |
| 702 } | |
| 703 } | |
| 704 // We finally get the hash | |
| 705 return hash; | |
| 0 | 706 } |
| 707 | |
| 1878 | 708 // Deprecated -- use FastHashCode() instead. |
| 0 | 709 |
| 1878 | 710 intptr_t ObjectSynchronizer::identity_hash_value_for(Handle obj) { |
| 711 return FastHashCode (Thread::current(), obj()) ; | |
| 0 | 712 } |
| 713 | |
| 714 | |
| 1878 | 715 bool ObjectSynchronizer::current_thread_holds_lock(JavaThread* thread, |
| 716 Handle h_obj) { | |
| 717 if (UseBiasedLocking) { | |
| 718 BiasedLocking::revoke_and_rebias(h_obj, false, thread); | |
| 719 assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 720 } | |
| 721 | |
| 722 assert(thread == JavaThread::current(), "Can only be called on current thread"); | |
| 723 oop obj = h_obj(); | |
| 724 | |
| 725 markOop mark = ReadStableMark (obj) ; | |
| 0 | 726 |
| 1878 | 727 // Uncontended case, header points to stack |
| 728 if (mark->has_locker()) { | |
| 729 return thread->is_lock_owned((address)mark->locker()); | |
| 0 | 730 } |
| 1878 | 731 // Contended case, header points to ObjectMonitor (tagged pointer) |
| 732 if (mark->has_monitor()) { | |
| 733 ObjectMonitor* monitor = mark->monitor(); | |
| 734 return monitor->is_entered(thread) != 0 ; | |
| 0 | 735 } |
| 1878 | 736 // Unlocked case, header in place |
| 737 assert(mark->is_neutral(), "sanity check"); | |
| 738 return false; | |
| 0 | 739 } |
| 740 | |
| 1878 | 741 // Be aware of this method could revoke bias of the lock object. |
| 742 // This method querys the ownership of the lock handle specified by 'h_obj'. | |
| 743 // If the current thread owns the lock, it returns owner_self. If no | |
| 744 // thread owns the lock, it returns owner_none. Otherwise, it will return | |
| 745 // ower_other. | |
| 746 ObjectSynchronizer::LockOwnership ObjectSynchronizer::query_lock_ownership | |
| 747 (JavaThread *self, Handle h_obj) { | |
| 748 // The caller must beware this method can revoke bias, and | |
| 749 // revocation can result in a safepoint. | |
| 750 assert (!SafepointSynchronize::is_at_safepoint(), "invariant") ; | |
| 751 assert (self->thread_state() != _thread_blocked , "invariant") ; | |
| 0 | 752 |
| 1878 | 753 // Possible mark states: neutral, biased, stack-locked, inflated |
| 754 | |
| 755 if (UseBiasedLocking && h_obj()->mark()->has_bias_pattern()) { | |
| 756 // CASE: biased | |
| 757 BiasedLocking::revoke_and_rebias(h_obj, false, self); | |
| 758 assert(!h_obj->mark()->has_bias_pattern(), | |
| 759 "biases should be revoked by now"); | |
| 760 } | |
| 0 | 761 |
| 1878 | 762 assert(self == JavaThread::current(), "Can only be called on current thread"); |
| 763 oop obj = h_obj(); | |
| 764 markOop mark = ReadStableMark (obj) ; | |
| 765 | |
| 766 // CASE: stack-locked. Mark points to a BasicLock on the owner's stack. | |
| 767 if (mark->has_locker()) { | |
| 768 return self->is_lock_owned((address)mark->locker()) ? | |
| 769 owner_self : owner_other; | |
| 770 } | |
| 0 | 771 |
| 1878 | 772 // CASE: inflated. Mark (tagged pointer) points to an objectMonitor. |
| 773 // The Object:ObjectMonitor relationship is stable as long as we're | |
| 774 // not at a safepoint. | |
| 775 if (mark->has_monitor()) { | |
| 776 void * owner = mark->monitor()->_owner ; | |
| 777 if (owner == NULL) return owner_none ; | |
| 778 return (owner == self || | |
| 779 self->is_lock_owned((address)owner)) ? owner_self : owner_other; | |
| 780 } | |
| 781 | |
| 782 // CASE: neutral | |
| 783 assert(mark->is_neutral(), "sanity check"); | |
| 784 return owner_none ; // it's unlocked | |
| 785 } | |
| 0 | 786 |
| 1878 | 787 // FIXME: jvmti should call this |
| 788 JavaThread* ObjectSynchronizer::get_lock_owner(Handle h_obj, bool doLock) { | |
| 789 if (UseBiasedLocking) { | |
| 790 if (SafepointSynchronize::is_at_safepoint()) { | |
| 791 BiasedLocking::revoke_at_safepoint(h_obj); | |
| 792 } else { | |
| 793 BiasedLocking::revoke_and_rebias(h_obj, false, JavaThread::current()); | |
| 794 } | |
| 795 assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now"); | |
| 796 } | |
| 797 | |
| 798 oop obj = h_obj(); | |
| 799 address owner = NULL; | |
| 800 | |
| 801 markOop mark = ReadStableMark (obj) ; | |
| 802 | |
| 803 // Uncontended case, header points to stack | |
| 804 if (mark->has_locker()) { | |
| 805 owner = (address) mark->locker(); | |
| 806 } | |
| 807 | |
| 808 // Contended case, header points to ObjectMonitor (tagged pointer) | |
| 809 if (mark->has_monitor()) { | |
| 810 ObjectMonitor* monitor = mark->monitor(); | |
| 811 assert(monitor != NULL, "monitor should be non-null"); | |
| 812 owner = (address) monitor->owner(); | |
| 813 } | |
| 814 | |
| 815 if (owner != NULL) { | |
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816 // owning_thread_from_monitor_owner() may also return NULL here |
| 1878 | 817 return Threads::owning_thread_from_monitor_owner(owner, doLock); |
| 818 } | |
| 819 | |
| 820 // Unlocked case, header in place | |
| 821 // Cannot have assertion since this object may have been | |
| 822 // locked by another thread when reaching here. | |
| 823 // assert(mark->is_neutral(), "sanity check"); | |
| 824 | |
| 825 return NULL; | |
| 826 } | |
| 827 // Visitors ... | |
| 828 | |
| 829 void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure) { | |
| 830 ObjectMonitor* block = gBlockList; | |
| 831 ObjectMonitor* mid; | |
| 832 while (block) { | |
| 833 assert(block->object() == CHAINMARKER, "must be a block header"); | |
| 834 for (int i = _BLOCKSIZE - 1; i > 0; i--) { | |
| 835 mid = block + i; | |
| 836 oop object = (oop) mid->object(); | |
| 837 if (object != NULL) { | |
| 838 closure->do_monitor(mid); | |
| 839 } | |
| 840 } | |
| 841 block = (ObjectMonitor*) block->FreeNext; | |
| 0 | 842 } |
| 843 } | |
| 844 | |
| 1878 | 845 // Get the next block in the block list. |
| 846 static inline ObjectMonitor* next(ObjectMonitor* block) { | |
| 847 assert(block->object() == CHAINMARKER, "must be a block header"); | |
| 848 block = block->FreeNext ; | |
| 849 assert(block == NULL || block->object() == CHAINMARKER, "must be a block header"); | |
| 850 return block; | |
| 0 | 851 } |
| 852 | |
| 853 | |
| 1878 | 854 void ObjectSynchronizer::oops_do(OopClosure* f) { |
| 855 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); | |
| 856 for (ObjectMonitor* block = gBlockList; block != NULL; block = next(block)) { | |
| 857 assert(block->object() == CHAINMARKER, "must be a block header"); | |
| 858 for (int i = 1; i < _BLOCKSIZE; i++) { | |
| 859 ObjectMonitor* mid = &block[i]; | |
| 860 if (mid->object() != NULL) { | |
| 861 f->do_oop((oop*)mid->object_addr()); | |
| 0 | 862 } |
| 863 } | |
| 864 } | |
| 865 } | |
| 866 | |
| 867 | |
| 1878 | 868 // ----------------------------------------------------------------------------- |
| 0 | 869 // ObjectMonitor Lifecycle |
| 870 // ----------------------- | |
| 871 // Inflation unlinks monitors from the global gFreeList and | |
| 872 // associates them with objects. Deflation -- which occurs at | |
| 873 // STW-time -- disassociates idle monitors from objects. Such | |
| 874 // scavenged monitors are returned to the gFreeList. | |
| 875 // | |
| 876 // The global list is protected by ListLock. All the critical sections | |
| 877 // are short and operate in constant-time. | |
| 878 // | |
| 879 // ObjectMonitors reside in type-stable memory (TSM) and are immortal. | |
| 880 // | |
| 881 // Lifecycle: | |
| 882 // -- unassigned and on the global free list | |
| 883 // -- unassigned and on a thread's private omFreeList | |
| 884 // -- assigned to an object. The object is inflated and the mark refers | |
| 885 // to the objectmonitor. | |
| 886 // | |
| 887 | |
| 888 | |
| 1587 | 889 // Constraining monitor pool growth via MonitorBound ... |
| 890 // | |
| 891 // The monitor pool is grow-only. We scavenge at STW safepoint-time, but the | |
| 892 // the rate of scavenging is driven primarily by GC. As such, we can find | |
| 893 // an inordinate number of monitors in circulation. | |
| 894 // To avoid that scenario we can artificially induce a STW safepoint | |
| 895 // if the pool appears to be growing past some reasonable bound. | |
| 896 // Generally we favor time in space-time tradeoffs, but as there's no | |
| 897 // natural back-pressure on the # of extant monitors we need to impose some | |
| 898 // type of limit. Beware that if MonitorBound is set to too low a value | |
| 899 // we could just loop. In addition, if MonitorBound is set to a low value | |
| 900 // we'll incur more safepoints, which are harmful to performance. | |
| 901 // See also: GuaranteedSafepointInterval | |
| 902 // | |
| 903 // The current implementation uses asynchronous VM operations. | |
| 904 // | |
| 905 | |
| 906 static void InduceScavenge (Thread * Self, const char * Whence) { | |
| 907 // Induce STW safepoint to trim monitors | |
| 908 // Ultimately, this results in a call to deflate_idle_monitors() in the near future. | |
| 909 // More precisely, trigger an asynchronous STW safepoint as the number | |
| 910 // of active monitors passes the specified threshold. | |
| 911 // TODO: assert thread state is reasonable | |
| 912 | |
| 913 if (ForceMonitorScavenge == 0 && Atomic::xchg (1, &ForceMonitorScavenge) == 0) { | |
| 1878 | 914 if (ObjectMonitor::Knob_Verbose) { |
| 1587 | 915 ::printf ("Monitor scavenge - Induced STW @%s (%d)\n", Whence, ForceMonitorScavenge) ; |
| 916 ::fflush(stdout) ; | |
| 917 } | |
| 918 // Induce a 'null' safepoint to scavenge monitors | |
| 919 // Must VM_Operation instance be heap allocated as the op will be enqueue and posted | |
| 920 // to the VMthread and have a lifespan longer than that of this activation record. | |
| 921 // The VMThread will delete the op when completed. | |
| 922 VMThread::execute (new VM_ForceAsyncSafepoint()) ; | |
| 923 | |
| 1878 | 924 if (ObjectMonitor::Knob_Verbose) { |
| 1587 | 925 ::printf ("Monitor scavenge - STW posted @%s (%d)\n", Whence, ForceMonitorScavenge) ; |
| 926 ::fflush(stdout) ; | |
| 927 } | |
| 928 } | |
| 929 } | |
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930 /* Too slow for general assert or debug |
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931 void ObjectSynchronizer::verifyInUse (Thread *Self) { |
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932 ObjectMonitor* mid; |
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933 int inusetally = 0; |
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934 for (mid = Self->omInUseList; mid != NULL; mid = mid->FreeNext) { |
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935 inusetally ++; |
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936 } |
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937 assert(inusetally == Self->omInUseCount, "inuse count off"); |
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938 |
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939 int freetally = 0; |
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940 for (mid = Self->omFreeList; mid != NULL; mid = mid->FreeNext) { |
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941 freetally ++; |
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942 } |
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943 assert(freetally == Self->omFreeCount, "free count off"); |
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944 } |
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945 */ |
| 0 | 946 ObjectMonitor * ATTR ObjectSynchronizer::omAlloc (Thread * Self) { |
| 947 // A large MAXPRIVATE value reduces both list lock contention | |
| 948 // and list coherency traffic, but also tends to increase the | |
| 949 // number of objectMonitors in circulation as well as the STW | |
| 950 // scavenge costs. As usual, we lean toward time in space-time | |
| 951 // tradeoffs. | |
| 952 const int MAXPRIVATE = 1024 ; | |
| 953 for (;;) { | |
| 954 ObjectMonitor * m ; | |
| 955 | |
| 956 // 1: try to allocate from the thread's local omFreeList. | |
| 957 // Threads will attempt to allocate first from their local list, then | |
| 958 // from the global list, and only after those attempts fail will the thread | |
| 959 // attempt to instantiate new monitors. Thread-local free lists take | |
| 960 // heat off the ListLock and improve allocation latency, as well as reducing | |
| 961 // coherency traffic on the shared global list. | |
| 962 m = Self->omFreeList ; | |
| 963 if (m != NULL) { | |
| 964 Self->omFreeList = m->FreeNext ; | |
| 965 Self->omFreeCount -- ; | |
| 966 // CONSIDER: set m->FreeNext = BAD -- diagnostic hygiene | |
| 967 guarantee (m->object() == NULL, "invariant") ; | |
| 1587 | 968 if (MonitorInUseLists) { |
| 969 m->FreeNext = Self->omInUseList; | |
| 970 Self->omInUseList = m; | |
| 971 Self->omInUseCount ++; | |
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972 // verifyInUse(Self); |
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973 } else { |
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974 m->FreeNext = NULL; |
| 1587 | 975 } |
| 0 | 976 return m ; |
| 977 } | |
| 978 | |
| 979 // 2: try to allocate from the global gFreeList | |
| 980 // CONSIDER: use muxTry() instead of muxAcquire(). | |
| 981 // If the muxTry() fails then drop immediately into case 3. | |
| 982 // If we're using thread-local free lists then try | |
| 983 // to reprovision the caller's free list. | |
| 984 if (gFreeList != NULL) { | |
| 985 // Reprovision the thread's omFreeList. | |
| 986 // Use bulk transfers to reduce the allocation rate and heat | |
| 987 // on various locks. | |
| 988 Thread::muxAcquire (&ListLock, "omAlloc") ; | |
| 989 for (int i = Self->omFreeProvision; --i >= 0 && gFreeList != NULL; ) { | |
| 1587 | 990 MonitorFreeCount --; |
| 0 | 991 ObjectMonitor * take = gFreeList ; |
| 992 gFreeList = take->FreeNext ; | |
| 993 guarantee (take->object() == NULL, "invariant") ; | |
| 994 guarantee (!take->is_busy(), "invariant") ; | |
| 995 take->Recycle() ; | |
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996 omRelease (Self, take, false) ; |
| 0 | 997 } |
| 998 Thread::muxRelease (&ListLock) ; | |
| 999 Self->omFreeProvision += 1 + (Self->omFreeProvision/2) ; | |
| 1000 if (Self->omFreeProvision > MAXPRIVATE ) Self->omFreeProvision = MAXPRIVATE ; | |
| 1001 TEVENT (omFirst - reprovision) ; | |
| 1587 | 1002 |
| 1003 const int mx = MonitorBound ; | |
| 1004 if (mx > 0 && (MonitorPopulation-MonitorFreeCount) > mx) { | |
| 1005 // We can't safely induce a STW safepoint from omAlloc() as our thread | |
| 1006 // state may not be appropriate for such activities and callers may hold | |
| 1007 // naked oops, so instead we defer the action. | |
| 1008 InduceScavenge (Self, "omAlloc") ; | |
| 1009 } | |
| 1010 continue; | |
| 0 | 1011 } |
| 1012 | |
| 1013 // 3: allocate a block of new ObjectMonitors | |
| 1014 // Both the local and global free lists are empty -- resort to malloc(). | |
| 1015 // In the current implementation objectMonitors are TSM - immortal. | |
| 1016 assert (_BLOCKSIZE > 1, "invariant") ; | |
| 10135 | 1017 ObjectMonitor * temp = new ObjectMonitor[_BLOCKSIZE]; |
| 0 | 1018 |
| 1019 // NOTE: (almost) no way to recover if allocation failed. | |
| 1020 // We might be able to induce a STW safepoint and scavenge enough | |
| 1021 // objectMonitors to permit progress. | |
| 1022 if (temp == NULL) { | |
|
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1023 vm_exit_out_of_memory (sizeof (ObjectMonitor[_BLOCKSIZE]), OOM_MALLOC_ERROR, |
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1024 "Allocate ObjectMonitors"); |
| 0 | 1025 } |
| 1026 | |
| 1027 // Format the block. | |
| 1028 // initialize the linked list, each monitor points to its next | |
| 1029 // forming the single linked free list, the very first monitor | |
| 1030 // will points to next block, which forms the block list. | |
| 1031 // The trick of using the 1st element in the block as gBlockList | |
| 1032 // linkage should be reconsidered. A better implementation would | |
| 1033 // look like: class Block { Block * next; int N; ObjectMonitor Body [N] ; } | |
| 1034 | |
| 1035 for (int i = 1; i < _BLOCKSIZE ; i++) { | |
| 1036 temp[i].FreeNext = &temp[i+1]; | |
| 1037 } | |
| 1038 | |
| 1039 // terminate the last monitor as the end of list | |
| 1040 temp[_BLOCKSIZE - 1].FreeNext = NULL ; | |
| 1041 | |
| 1042 // Element [0] is reserved for global list linkage | |
| 1043 temp[0].set_object(CHAINMARKER); | |
| 1044 | |
| 1045 // Consider carving out this thread's current request from the | |
| 1046 // block in hand. This avoids some lock traffic and redundant | |
| 1047 // list activity. | |
| 1048 | |
| 1049 // Acquire the ListLock to manipulate BlockList and FreeList. | |
| 1050 // An Oyama-Taura-Yonezawa scheme might be more efficient. | |
| 1051 Thread::muxAcquire (&ListLock, "omAlloc [2]") ; | |
| 1587 | 1052 MonitorPopulation += _BLOCKSIZE-1; |
| 1053 MonitorFreeCount += _BLOCKSIZE-1; | |
| 0 | 1054 |
| 1055 // Add the new block to the list of extant blocks (gBlockList). | |
| 1056 // The very first objectMonitor in a block is reserved and dedicated. | |
| 1057 // It serves as blocklist "next" linkage. | |
| 1058 temp[0].FreeNext = gBlockList; | |
| 1059 gBlockList = temp; | |
| 1060 | |
| 1061 // Add the new string of objectMonitors to the global free list | |
| 1062 temp[_BLOCKSIZE - 1].FreeNext = gFreeList ; | |
| 1063 gFreeList = temp + 1; | |
| 1064 Thread::muxRelease (&ListLock) ; | |
| 1065 TEVENT (Allocate block of monitors) ; | |
| 1066 } | |
| 1067 } | |
| 1068 | |
| 1069 // Place "m" on the caller's private per-thread omFreeList. | |
| 1070 // In practice there's no need to clamp or limit the number of | |
| 1071 // monitors on a thread's omFreeList as the only time we'll call | |
| 1072 // omRelease is to return a monitor to the free list after a CAS | |
| 1073 // attempt failed. This doesn't allow unbounded #s of monitors to | |
| 1074 // accumulate on a thread's free list. | |
| 1075 // | |
| 1076 | |
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1077 void ObjectSynchronizer::omRelease (Thread * Self, ObjectMonitor * m, bool fromPerThreadAlloc) { |
| 0 | 1078 guarantee (m->object() == NULL, "invariant") ; |
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1079 |
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1080 // Remove from omInUseList |
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1081 if (MonitorInUseLists && fromPerThreadAlloc) { |
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1082 ObjectMonitor* curmidinuse = NULL; |
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1083 for (ObjectMonitor* mid = Self->omInUseList; mid != NULL; ) { |
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1084 if (m == mid) { |
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1085 // extract from per-thread in-use-list |
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1086 if (mid == Self->omInUseList) { |
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1087 Self->omInUseList = mid->FreeNext; |
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1088 } else if (curmidinuse != NULL) { |
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1089 curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist |
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1090 } |
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1091 Self->omInUseCount --; |
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1092 // verifyInUse(Self); |
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1093 break; |
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1094 } else { |
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1095 curmidinuse = mid; |
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1096 mid = mid->FreeNext; |
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1097 } |
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1098 } |
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1099 } |
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1100 |
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1101 // FreeNext is used for both onInUseList and omFreeList, so clear old before setting new |
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1102 m->FreeNext = Self->omFreeList ; |
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1103 Self->omFreeList = m ; |
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1104 Self->omFreeCount ++ ; |
| 0 | 1105 } |
| 1106 | |
| 1107 // Return the monitors of a moribund thread's local free list to | |
| 1108 // the global free list. Typically a thread calls omFlush() when | |
| 1109 // it's dying. We could also consider having the VM thread steal | |
| 1110 // monitors from threads that have not run java code over a few | |
| 1111 // consecutive STW safepoints. Relatedly, we might decay | |
| 1112 // omFreeProvision at STW safepoints. | |
| 1113 // | |
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1114 // Also return the monitors of a moribund thread"s omInUseList to |
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1115 // a global gOmInUseList under the global list lock so these |
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1116 // will continue to be scanned. |
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1117 // |
| 0 | 1118 // We currently call omFlush() from the Thread:: dtor _after the thread |
| 1119 // has been excised from the thread list and is no longer a mutator. | |
| 1120 // That means that omFlush() can run concurrently with a safepoint and | |
| 1121 // the scavenge operator. Calling omFlush() from JavaThread::exit() might | |
| 1122 // be a better choice as we could safely reason that that the JVM is | |
| 1123 // not at a safepoint at the time of the call, and thus there could | |
| 1124 // be not inopportune interleavings between omFlush() and the scavenge | |
| 1125 // operator. | |
| 1126 | |
| 1127 void ObjectSynchronizer::omFlush (Thread * Self) { | |
| 1128 ObjectMonitor * List = Self->omFreeList ; // Null-terminated SLL | |
| 1129 Self->omFreeList = NULL ; | |
| 1130 ObjectMonitor * Tail = NULL ; | |
| 1587 | 1131 int Tally = 0; |
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1132 if (List != NULL) { |
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1133 ObjectMonitor * s ; |
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1134 for (s = List ; s != NULL ; s = s->FreeNext) { |
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1135 Tally ++ ; |
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1136 Tail = s ; |
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1137 guarantee (s->object() == NULL, "invariant") ; |
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1138 guarantee (!s->is_busy(), "invariant") ; |
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1139 s->set_owner (NULL) ; // redundant but good hygiene |
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1140 TEVENT (omFlush - Move one) ; |
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1141 } |
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1142 guarantee (Tail != NULL && List != NULL, "invariant") ; |
| 0 | 1143 } |
| 1144 | |
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1145 ObjectMonitor * InUseList = Self->omInUseList; |
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1146 ObjectMonitor * InUseTail = NULL ; |
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1147 int InUseTally = 0; |
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1148 if (InUseList != NULL) { |
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1149 Self->omInUseList = NULL; |
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1150 ObjectMonitor *curom; |
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1151 for (curom = InUseList; curom != NULL; curom = curom->FreeNext) { |
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1152 InUseTail = curom; |
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1153 InUseTally++; |
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1154 } |
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1155 // TODO debug |
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1156 assert(Self->omInUseCount == InUseTally, "inuse count off"); |
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1157 Self->omInUseCount = 0; |
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1158 guarantee (InUseTail != NULL && InUseList != NULL, "invariant"); |
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1159 } |
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1160 |
| 0 | 1161 Thread::muxAcquire (&ListLock, "omFlush") ; |
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1162 if (Tail != NULL) { |
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1163 Tail->FreeNext = gFreeList ; |
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1164 gFreeList = List ; |
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1165 MonitorFreeCount += Tally; |
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1166 } |
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1167 |
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1168 if (InUseTail != NULL) { |
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1169 InUseTail->FreeNext = gOmInUseList; |
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1170 gOmInUseList = InUseList; |
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1171 gOmInUseCount += InUseTally; |
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1172 } |
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1173 |
| 0 | 1174 Thread::muxRelease (&ListLock) ; |
| 1175 TEVENT (omFlush) ; | |
| 1176 } | |
| 1177 | |
| 1178 // Fast path code shared by multiple functions | |
| 1179 ObjectMonitor* ObjectSynchronizer::inflate_helper(oop obj) { | |
| 1180 markOop mark = obj->mark(); | |
| 1181 if (mark->has_monitor()) { | |
| 1182 assert(ObjectSynchronizer::verify_objmon_isinpool(mark->monitor()), "monitor is invalid"); | |
| 1183 assert(mark->monitor()->header()->is_neutral(), "monitor must record a good object header"); | |
| 1184 return mark->monitor(); | |
| 1185 } | |
| 1186 return ObjectSynchronizer::inflate(Thread::current(), obj); | |
| 1187 } | |
| 1188 | |
| 1878 | 1189 |
| 0 | 1190 // Note that we could encounter some performance loss through false-sharing as |
| 1191 // multiple locks occupy the same $ line. Padding might be appropriate. | |
| 1192 | |
| 1193 | |
| 1194 ObjectMonitor * ATTR ObjectSynchronizer::inflate (Thread * Self, oop object) { | |
| 1195 // Inflate mutates the heap ... | |
| 1196 // Relaxing assertion for bug 6320749. | |
| 1197 assert (Universe::verify_in_progress() || | |
| 1198 !SafepointSynchronize::is_at_safepoint(), "invariant") ; | |
| 1199 | |
| 1200 for (;;) { | |
| 1201 const markOop mark = object->mark() ; | |
| 1202 assert (!mark->has_bias_pattern(), "invariant") ; | |
| 1203 | |
| 1204 // The mark can be in one of the following states: | |
| 1205 // * Inflated - just return | |
| 1206 // * Stack-locked - coerce it to inflated | |
| 1207 // * INFLATING - busy wait for conversion to complete | |
| 1208 // * Neutral - aggressively inflate the object. | |
| 1209 // * BIASED - Illegal. We should never see this | |
| 1210 | |
| 1211 // CASE: inflated | |
| 1212 if (mark->has_monitor()) { | |
| 1213 ObjectMonitor * inf = mark->monitor() ; | |
| 1214 assert (inf->header()->is_neutral(), "invariant"); | |
| 1215 assert (inf->object() == object, "invariant") ; | |
| 1216 assert (ObjectSynchronizer::verify_objmon_isinpool(inf), "monitor is invalid"); | |
| 1217 return inf ; | |
| 1218 } | |
| 1219 | |
| 1220 // CASE: inflation in progress - inflating over a stack-lock. | |
| 1221 // Some other thread is converting from stack-locked to inflated. | |
| 1222 // Only that thread can complete inflation -- other threads must wait. | |
| 1223 // The INFLATING value is transient. | |
| 1224 // Currently, we spin/yield/park and poll the markword, waiting for inflation to finish. | |
| 1225 // We could always eliminate polling by parking the thread on some auxiliary list. | |
| 1226 if (mark == markOopDesc::INFLATING()) { | |
| 1227 TEVENT (Inflate: spin while INFLATING) ; | |
| 1228 ReadStableMark(object) ; | |
| 1229 continue ; | |
| 1230 } | |
| 1231 | |
| 1232 // CASE: stack-locked | |
| 1233 // Could be stack-locked either by this thread or by some other thread. | |
| 1234 // | |
| 1235 // Note that we allocate the objectmonitor speculatively, _before_ attempting | |
| 1236 // to install INFLATING into the mark word. We originally installed INFLATING, | |
| 1237 // allocated the objectmonitor, and then finally STed the address of the | |
| 1238 // objectmonitor into the mark. This was correct, but artificially lengthened | |
| 1239 // the interval in which INFLATED appeared in the mark, thus increasing | |
| 1240 // the odds of inflation contention. | |
| 1241 // | |
| 1242 // We now use per-thread private objectmonitor free lists. | |
| 1243 // These list are reprovisioned from the global free list outside the | |
| 1244 // critical INFLATING...ST interval. A thread can transfer | |
| 1245 // multiple objectmonitors en-mass from the global free list to its local free list. | |
| 1246 // This reduces coherency traffic and lock contention on the global free list. | |
| 1247 // Using such local free lists, it doesn't matter if the omAlloc() call appears | |
| 1248 // before or after the CAS(INFLATING) operation. | |
| 1249 // See the comments in omAlloc(). | |
| 1250 | |
| 1251 if (mark->has_locker()) { | |
| 1252 ObjectMonitor * m = omAlloc (Self) ; | |
| 1253 // Optimistically prepare the objectmonitor - anticipate successful CAS | |
| 1254 // We do this before the CAS in order to minimize the length of time | |
| 1255 // in which INFLATING appears in the mark. | |
| 1256 m->Recycle(); | |
| 1257 m->_Responsible = NULL ; | |
| 1258 m->OwnerIsThread = 0 ; | |
| 1259 m->_recursions = 0 ; | |
| 1878 | 1260 m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ; // Consider: maintain by type/class |
| 0 | 1261 |
| 1262 markOop cmp = (markOop) Atomic::cmpxchg_ptr (markOopDesc::INFLATING(), object->mark_addr(), mark) ; | |
| 1263 if (cmp != mark) { | |
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1264 omRelease (Self, m, true) ; |
| 0 | 1265 continue ; // Interference -- just retry |
| 1266 } | |
| 1267 | |
| 1268 // We've successfully installed INFLATING (0) into the mark-word. | |
| 1269 // This is the only case where 0 will appear in a mark-work. | |
| 1270 // Only the singular thread that successfully swings the mark-word | |
| 1271 // to 0 can perform (or more precisely, complete) inflation. | |
| 1272 // | |
| 1273 // Why do we CAS a 0 into the mark-word instead of just CASing the | |
| 1274 // mark-word from the stack-locked value directly to the new inflated state? | |
| 1275 // Consider what happens when a thread unlocks a stack-locked object. | |
| 1276 // It attempts to use CAS to swing the displaced header value from the | |
| 1277 // on-stack basiclock back into the object header. Recall also that the | |
| 1278 // header value (hashcode, etc) can reside in (a) the object header, or | |
| 1279 // (b) a displaced header associated with the stack-lock, or (c) a displaced | |
| 1280 // header in an objectMonitor. The inflate() routine must copy the header | |
| 1281 // value from the basiclock on the owner's stack to the objectMonitor, all | |
| 1282 // the while preserving the hashCode stability invariants. If the owner | |
| 1283 // decides to release the lock while the value is 0, the unlock will fail | |
| 1284 // and control will eventually pass from slow_exit() to inflate. The owner | |
| 1285 // will then spin, waiting for the 0 value to disappear. Put another way, | |
| 1286 // the 0 causes the owner to stall if the owner happens to try to | |
| 1287 // drop the lock (restoring the header from the basiclock to the object) | |
| 1288 // while inflation is in-progress. This protocol avoids races that might | |
| 1289 // would otherwise permit hashCode values to change or "flicker" for an object. | |
| 1290 // Critically, while object->mark is 0 mark->displaced_mark_helper() is stable. | |
| 1291 // 0 serves as a "BUSY" inflate-in-progress indicator. | |
| 1292 | |
| 1293 | |
| 1294 // fetch the displaced mark from the owner's stack. | |
| 1295 // The owner can't die or unwind past the lock while our INFLATING | |
| 1296 // object is in the mark. Furthermore the owner can't complete | |
| 1297 // an unlock on the object, either. | |
| 1298 markOop dmw = mark->displaced_mark_helper() ; | |
| 1299 assert (dmw->is_neutral(), "invariant") ; | |
| 1300 | |
| 1301 // Setup monitor fields to proper values -- prepare the monitor | |
| 1302 m->set_header(dmw) ; | |
| 1303 | |
| 1304 // Optimization: if the mark->locker stack address is associated | |
| 1305 // with this thread we could simply set m->_owner = Self and | |
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1306 // m->OwnerIsThread = 1. Note that a thread can inflate an object |
| 0 | 1307 // that it has stack-locked -- as might happen in wait() -- directly |
| 1308 // with CAS. That is, we can avoid the xchg-NULL .... ST idiom. | |
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1309 m->set_owner(mark->locker()); |
| 0 | 1310 m->set_object(object); |
| 1311 // TODO-FIXME: assert BasicLock->dhw != 0. | |
| 1312 | |
| 1313 // Must preserve store ordering. The monitor state must | |
| 1314 // be stable at the time of publishing the monitor address. | |
| 1315 guarantee (object->mark() == markOopDesc::INFLATING(), "invariant") ; | |
| 1316 object->release_set_mark(markOopDesc::encode(m)); | |
| 1317 | |
| 1318 // Hopefully the performance counters are allocated on distinct cache lines | |
| 1319 // to avoid false sharing on MP systems ... | |
| 1878 | 1320 if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ; |
| 0 | 1321 TEVENT(Inflate: overwrite stacklock) ; |
| 1322 if (TraceMonitorInflation) { | |
| 1323 if (object->is_instance()) { | |
| 1324 ResourceMark rm; | |
| 1325 tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
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1326 (void *) object, (intptr_t) object->mark(), |
| 6983 | 1327 object->klass()->external_name()); |
| 0 | 1328 } |
| 1329 } | |
| 1330 return m ; | |
| 1331 } | |
| 1332 | |
| 1333 // CASE: neutral | |
| 1334 // TODO-FIXME: for entry we currently inflate and then try to CAS _owner. | |
| 1335 // If we know we're inflating for entry it's better to inflate by swinging a | |
| 1336 // pre-locked objectMonitor pointer into the object header. A successful | |
| 1337 // CAS inflates the object *and* confers ownership to the inflating thread. | |
| 1338 // In the current implementation we use a 2-step mechanism where we CAS() | |
| 1339 // to inflate and then CAS() again to try to swing _owner from NULL to Self. | |
| 1340 // An inflateTry() method that we could call from fast_enter() and slow_enter() | |
| 1341 // would be useful. | |
| 1342 | |
| 1343 assert (mark->is_neutral(), "invariant"); | |
| 1344 ObjectMonitor * m = omAlloc (Self) ; | |
| 1345 // prepare m for installation - set monitor to initial state | |
| 1346 m->Recycle(); | |
| 1347 m->set_header(mark); | |
| 1348 m->set_owner(NULL); | |
| 1349 m->set_object(object); | |
| 1350 m->OwnerIsThread = 1 ; | |
| 1351 m->_recursions = 0 ; | |
| 1352 m->_Responsible = NULL ; | |
| 1878 | 1353 m->_SpinDuration = ObjectMonitor::Knob_SpinLimit ; // consider: keep metastats by type/class |
| 0 | 1354 |
| 1355 if (Atomic::cmpxchg_ptr (markOopDesc::encode(m), object->mark_addr(), mark) != mark) { | |
| 1356 m->set_object (NULL) ; | |
| 1357 m->set_owner (NULL) ; | |
| 1358 m->OwnerIsThread = 0 ; | |
| 1359 m->Recycle() ; | |
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1360 omRelease (Self, m, true) ; |
| 0 | 1361 m = NULL ; |
| 1362 continue ; | |
| 1363 // interference - the markword changed - just retry. | |
| 1364 // The state-transitions are one-way, so there's no chance of | |
| 1365 // live-lock -- "Inflated" is an absorbing state. | |
| 1366 } | |
| 1367 | |
| 1368 // Hopefully the performance counters are allocated on distinct | |
| 1369 // cache lines to avoid false sharing on MP systems ... | |
| 1878 | 1370 if (ObjectMonitor::_sync_Inflations != NULL) ObjectMonitor::_sync_Inflations->inc() ; |
| 0 | 1371 TEVENT(Inflate: overwrite neutral) ; |
| 1372 if (TraceMonitorInflation) { | |
| 1373 if (object->is_instance()) { | |
| 1374 ResourceMark rm; | |
| 1375 tty->print_cr("Inflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
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1376 (void *) object, (intptr_t) object->mark(), |
| 6983 | 1377 object->klass()->external_name()); |
| 0 | 1378 } |
| 1379 } | |
| 1380 return m ; | |
| 1381 } | |
| 1382 } | |
| 1383 | |
| 1878 | 1384 // Note that we could encounter some performance loss through false-sharing as |
| 1385 // multiple locks occupy the same $ line. Padding might be appropriate. | |
| 0 | 1386 |
| 1387 | |
| 1388 // Deflate_idle_monitors() is called at all safepoints, immediately | |
| 1389 // after all mutators are stopped, but before any objects have moved. | |
| 1390 // It traverses the list of known monitors, deflating where possible. | |
| 1391 // The scavenged monitor are returned to the monitor free list. | |
| 1392 // | |
| 1393 // Beware that we scavenge at *every* stop-the-world point. | |
| 1394 // Having a large number of monitors in-circulation negatively | |
| 1395 // impacts the performance of some applications (e.g., PointBase). | |
| 1396 // Broadly, we want to minimize the # of monitors in circulation. | |
| 1587 | 1397 // |
| 1398 // We have added a flag, MonitorInUseLists, which creates a list | |
| 1399 // of active monitors for each thread. deflate_idle_monitors() | |
| 1400 // only scans the per-thread inuse lists. omAlloc() puts all | |
| 1401 // assigned monitors on the per-thread list. deflate_idle_monitors() | |
| 1402 // returns the non-busy monitors to the global free list. | |
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1403 // When a thread dies, omFlush() adds the list of active monitors for |
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1404 // that thread to a global gOmInUseList acquiring the |
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1405 // global list lock. deflate_idle_monitors() acquires the global |
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1406 // list lock to scan for non-busy monitors to the global free list. |
| 1587 | 1407 // An alternative could have used a single global inuse list. The |
| 1408 // downside would have been the additional cost of acquiring the global list lock | |
| 1409 // for every omAlloc(). | |
| 0 | 1410 // |
| 1411 // Perversely, the heap size -- and thus the STW safepoint rate -- | |
| 1412 // typically drives the scavenge rate. Large heaps can mean infrequent GC, | |
| 1413 // which in turn can mean large(r) numbers of objectmonitors in circulation. | |
| 1414 // This is an unfortunate aspect of this design. | |
| 1415 // | |
| 1416 | |
| 1878 | 1417 enum ManifestConstants { |
| 1418 ClearResponsibleAtSTW = 0, | |
| 1419 MaximumRecheckInterval = 1000 | |
| 1420 } ; | |
| 1587 | 1421 |
| 1422 // Deflate a single monitor if not in use | |
| 1423 // Return true if deflated, false if in use | |
| 1424 bool ObjectSynchronizer::deflate_monitor(ObjectMonitor* mid, oop obj, | |
| 1425 ObjectMonitor** FreeHeadp, ObjectMonitor** FreeTailp) { | |
| 1426 bool deflated; | |
| 1427 // Normal case ... The monitor is associated with obj. | |
| 1428 guarantee (obj->mark() == markOopDesc::encode(mid), "invariant") ; | |
| 1429 guarantee (mid == obj->mark()->monitor(), "invariant"); | |
| 1430 guarantee (mid->header()->is_neutral(), "invariant"); | |
| 1431 | |
| 1432 if (mid->is_busy()) { | |
| 1433 if (ClearResponsibleAtSTW) mid->_Responsible = NULL ; | |
| 1434 deflated = false; | |
| 1435 } else { | |
| 1436 // Deflate the monitor if it is no longer being used | |
| 1437 // It's idle - scavenge and return to the global free list | |
| 1438 // plain old deflation ... | |
| 1439 TEVENT (deflate_idle_monitors - scavenge1) ; | |
| 1440 if (TraceMonitorInflation) { | |
| 1441 if (obj->is_instance()) { | |
| 1442 ResourceMark rm; | |
| 1443 tty->print_cr("Deflating object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
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1444 (void *) obj, (intptr_t) obj->mark(), obj->klass()->external_name()); |
| 1587 | 1445 } |
| 1446 } | |
| 1447 | |
| 1448 // Restore the header back to obj | |
| 1449 obj->release_set_mark(mid->header()); | |
| 1450 mid->clear(); | |
| 1451 | |
| 1452 assert (mid->object() == NULL, "invariant") ; | |
| 1453 | |
| 1454 // Move the object to the working free list defined by FreeHead,FreeTail. | |
| 1455 if (*FreeHeadp == NULL) *FreeHeadp = mid; | |
| 1456 if (*FreeTailp != NULL) { | |
| 1457 ObjectMonitor * prevtail = *FreeTailp; | |
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1458 assert(prevtail->FreeNext == NULL, "cleaned up deflated?"); // TODO KK |
| 1587 | 1459 prevtail->FreeNext = mid; |
| 1460 } | |
| 1461 *FreeTailp = mid; | |
| 1462 deflated = true; | |
| 1463 } | |
| 1464 return deflated; | |
| 1465 } | |
| 1466 | |
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1467 // Caller acquires ListLock |
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1468 int ObjectSynchronizer::walk_monitor_list(ObjectMonitor** listheadp, |
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1469 ObjectMonitor** FreeHeadp, ObjectMonitor** FreeTailp) { |
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1470 ObjectMonitor* mid; |
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1471 ObjectMonitor* next; |
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1472 ObjectMonitor* curmidinuse = NULL; |
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1473 int deflatedcount = 0; |
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1474 |
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1475 for (mid = *listheadp; mid != NULL; ) { |
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1476 oop obj = (oop) mid->object(); |
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1477 bool deflated = false; |
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1478 if (obj != NULL) { |
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1479 deflated = deflate_monitor(mid, obj, FreeHeadp, FreeTailp); |
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1480 } |
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1481 if (deflated) { |
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1482 // extract from per-thread in-use-list |
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1483 if (mid == *listheadp) { |
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1484 *listheadp = mid->FreeNext; |
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1485 } else if (curmidinuse != NULL) { |
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1486 curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist |
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1487 } |
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1488 next = mid->FreeNext; |
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1489 mid->FreeNext = NULL; // This mid is current tail in the FreeHead list |
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1490 mid = next; |
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1491 deflatedcount++; |
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1492 } else { |
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1493 curmidinuse = mid; |
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1494 mid = mid->FreeNext; |
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1495 } |
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1496 } |
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1497 return deflatedcount; |
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1498 } |
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1499 |
| 0 | 1500 void ObjectSynchronizer::deflate_idle_monitors() { |
| 1501 assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint"); | |
| 1502 int nInuse = 0 ; // currently associated with objects | |
| 1503 int nInCirculation = 0 ; // extant | |
| 1504 int nScavenged = 0 ; // reclaimed | |
| 1587 | 1505 bool deflated = false; |
| 0 | 1506 |
| 1507 ObjectMonitor * FreeHead = NULL ; // Local SLL of scavenged monitors | |
| 1508 ObjectMonitor * FreeTail = NULL ; | |
| 1509 | |
| 1587 | 1510 TEVENT (deflate_idle_monitors) ; |
| 1511 // Prevent omFlush from changing mids in Thread dtor's during deflation | |
| 1512 // And in case the vm thread is acquiring a lock during a safepoint | |
| 1513 // See e.g. 6320749 | |
| 1514 Thread::muxAcquire (&ListLock, "scavenge - return") ; | |
| 1515 | |
| 1516 if (MonitorInUseLists) { | |
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1517 int inUse = 0; |
| 1587 | 1518 for (JavaThread* cur = Threads::first(); cur != NULL; cur = cur->next()) { |
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1519 nInCirculation+= cur->omInUseCount; |
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1520 int deflatedcount = walk_monitor_list(cur->omInUseList_addr(), &FreeHead, &FreeTail); |
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1521 cur->omInUseCount-= deflatedcount; |
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1522 // verifyInUse(cur); |
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1523 nScavenged += deflatedcount; |
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1524 nInuse += cur->omInUseCount; |
| 1587 | 1525 } |
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1526 |
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1527 // For moribund threads, scan gOmInUseList |
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1528 if (gOmInUseList) { |
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1529 nInCirculation += gOmInUseCount; |
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1530 int deflatedcount = walk_monitor_list((ObjectMonitor **)&gOmInUseList, &FreeHead, &FreeTail); |
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1531 gOmInUseCount-= deflatedcount; |
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1532 nScavenged += deflatedcount; |
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1533 nInuse += gOmInUseCount; |
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1534 } |
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1535 |
| 1587 | 1536 } else for (ObjectMonitor* block = gBlockList; block != NULL; block = next(block)) { |
| 0 | 1537 // Iterate over all extant monitors - Scavenge all idle monitors. |
| 1538 assert(block->object() == CHAINMARKER, "must be a block header"); | |
| 1539 nInCirculation += _BLOCKSIZE ; | |
| 1540 for (int i = 1 ; i < _BLOCKSIZE; i++) { | |
| 1541 ObjectMonitor* mid = &block[i]; | |
| 1542 oop obj = (oop) mid->object(); | |
| 1543 | |
| 1544 if (obj == NULL) { | |
| 1545 // The monitor is not associated with an object. | |
| 1546 // The monitor should either be a thread-specific private | |
| 1547 // free list or the global free list. | |
| 1548 // obj == NULL IMPLIES mid->is_busy() == 0 | |
| 1549 guarantee (!mid->is_busy(), "invariant") ; | |
| 1550 continue ; | |
| 1551 } | |
| 1587 | 1552 deflated = deflate_monitor(mid, obj, &FreeHead, &FreeTail); |
| 1553 | |
| 1554 if (deflated) { | |
| 1555 mid->FreeNext = NULL ; | |
| 1556 nScavenged ++ ; | |
| 0 | 1557 } else { |
| 1587 | 1558 nInuse ++; |
| 0 | 1559 } |
| 1560 } | |
| 1561 } | |
| 1562 | |
| 1587 | 1563 MonitorFreeCount += nScavenged; |
| 1564 | |
| 1565 // Consider: audit gFreeList to ensure that MonitorFreeCount and list agree. | |
| 1566 | |
| 1878 | 1567 if (ObjectMonitor::Knob_Verbose) { |
| 1587 | 1568 ::printf ("Deflate: InCirc=%d InUse=%d Scavenged=%d ForceMonitorScavenge=%d : pop=%d free=%d\n", |
| 1569 nInCirculation, nInuse, nScavenged, ForceMonitorScavenge, | |
| 1570 MonitorPopulation, MonitorFreeCount) ; | |
| 1571 ::fflush(stdout) ; | |
| 1572 } | |
| 1573 | |
| 1574 ForceMonitorScavenge = 0; // Reset | |
| 1575 | |
| 0 | 1576 // Move the scavenged monitors back to the global free list. |
| 1577 if (FreeHead != NULL) { | |
| 1578 guarantee (FreeTail != NULL && nScavenged > 0, "invariant") ; | |
| 1579 assert (FreeTail->FreeNext == NULL, "invariant") ; | |
| 1580 // constant-time list splice - prepend scavenged segment to gFreeList | |
| 1581 FreeTail->FreeNext = gFreeList ; | |
| 1582 gFreeList = FreeHead ; | |
| 1583 } | |
| 1587 | 1584 Thread::muxRelease (&ListLock) ; |
| 0 | 1585 |
| 1878 | 1586 if (ObjectMonitor::_sync_Deflations != NULL) ObjectMonitor::_sync_Deflations->inc(nScavenged) ; |
| 1587 if (ObjectMonitor::_sync_MonExtant != NULL) ObjectMonitor::_sync_MonExtant ->set_value(nInCirculation); | |
| 0 | 1588 |
| 1589 // TODO: Add objectMonitor leak detection. | |
| 1590 // Audit/inventory the objectMonitors -- make sure they're all accounted for. | |
| 1591 GVars.stwRandom = os::random() ; | |
| 1592 GVars.stwCycle ++ ; | |
| 1593 } | |
| 1594 | |
| 1878 | 1595 // Monitor cleanup on JavaThread::exit |
| 0 | 1596 |
| 1878 | 1597 // Iterate through monitor cache and attempt to release thread's monitors |
| 1598 // Gives up on a particular monitor if an exception occurs, but continues | |
| 1599 // the overall iteration, swallowing the exception. | |
| 1600 class ReleaseJavaMonitorsClosure: public MonitorClosure { | |
| 1601 private: | |
| 1602 TRAPS; | |
| 0 | 1603 |
| 1878 | 1604 public: |
| 1605 ReleaseJavaMonitorsClosure(Thread* thread) : THREAD(thread) {} | |
| 1606 void do_monitor(ObjectMonitor* mid) { | |
| 1607 if (mid->owner() == THREAD) { | |
| 1608 (void)mid->complete_exit(CHECK); | |
| 0 | 1609 } |
| 1610 } | |
| 1878 | 1611 }; |
| 0 | 1612 |
| 1878 | 1613 // Release all inflated monitors owned by THREAD. Lightweight monitors are |
| 1614 // ignored. This is meant to be called during JNI thread detach which assumes | |
| 1615 // all remaining monitors are heavyweight. All exceptions are swallowed. | |
| 1616 // Scanning the extant monitor list can be time consuming. | |
| 1617 // A simple optimization is to add a per-thread flag that indicates a thread | |
| 1618 // called jni_monitorenter() during its lifetime. | |
| 0 | 1619 // |
| 1878 | 1620 // Instead of No_Savepoint_Verifier it might be cheaper to |
| 1621 // use an idiom of the form: | |
| 1622 // auto int tmp = SafepointSynchronize::_safepoint_counter ; | |
| 1623 // <code that must not run at safepoint> | |
| 1624 // guarantee (((tmp ^ _safepoint_counter) | (tmp & 1)) == 0) ; | |
| 1625 // Since the tests are extremely cheap we could leave them enabled | |
| 1626 // for normal product builds. | |
| 0 | 1627 |
| 1878 | 1628 void ObjectSynchronizer::release_monitors_owned_by_thread(TRAPS) { |
| 1629 assert(THREAD == JavaThread::current(), "must be current Java thread"); | |
| 1630 No_Safepoint_Verifier nsv ; | |
| 1631 ReleaseJavaMonitorsClosure rjmc(THREAD); | |
| 1632 Thread::muxAcquire(&ListLock, "release_monitors_owned_by_thread"); | |
| 1633 ObjectSynchronizer::monitors_iterate(&rjmc); | |
| 1634 Thread::muxRelease(&ListLock); | |
| 1635 THREAD->clear_pending_exception(); | |
| 0 | 1636 } |
| 1637 | |
| 1638 //------------------------------------------------------------------------------ | |
| 1639 // Non-product code | |
| 1640 | |
| 1641 #ifndef PRODUCT | |
| 1642 | |
| 1643 // Verify all monitors in the monitor cache, the verification is weak. | |
| 1644 void ObjectSynchronizer::verify() { | |
| 1645 ObjectMonitor* block = gBlockList; | |
| 1646 ObjectMonitor* mid; | |
| 1647 while (block) { | |
| 1648 assert(block->object() == CHAINMARKER, "must be a block header"); | |
| 1649 for (int i = 1; i < _BLOCKSIZE; i++) { | |
| 1650 mid = block + i; | |
| 1651 oop object = (oop) mid->object(); | |
| 1652 if (object != NULL) { | |
| 1653 mid->verify(); | |
| 1654 } | |
| 1655 } | |
| 1656 block = (ObjectMonitor*) block->FreeNext; | |
| 1657 } | |
| 1658 } | |
| 1659 | |
| 1660 // Check if monitor belongs to the monitor cache | |
| 1661 // The list is grow-only so it's *relatively* safe to traverse | |
| 1662 // the list of extant blocks without taking a lock. | |
| 1663 | |
| 1664 int ObjectSynchronizer::verify_objmon_isinpool(ObjectMonitor *monitor) { | |
| 1665 ObjectMonitor* block = gBlockList; | |
| 1666 | |
| 1667 while (block) { | |
| 1668 assert(block->object() == CHAINMARKER, "must be a block header"); | |
| 1669 if (monitor > &block[0] && monitor < &block[_BLOCKSIZE]) { | |
| 1670 address mon = (address) monitor; | |
| 1671 address blk = (address) block; | |
| 1672 size_t diff = mon - blk; | |
| 1673 assert((diff % sizeof(ObjectMonitor)) == 0, "check"); | |
| 1674 return 1; | |
| 1675 } | |
| 1676 block = (ObjectMonitor*) block->FreeNext; | |
| 1677 } | |
| 1678 return 0; | |
| 1679 } | |
| 1680 | |
| 1681 #endif |