Mercurial > hg > truffle
annotate src/share/vm/runtime/synchronizer.cpp @ 1972:f95d63e2154a
6989984: Use standard include model for Hospot
Summary: Replaced MakeDeps and the includeDB files with more standardized solutions.
Reviewed-by: coleenp, kvn, kamg
| author | stefank |
|---|---|
| date | Tue, 23 Nov 2010 13:22:55 -0800 |
| parents | fa83ab460c54 |
| children | 06f017f7daa7 3582bf76420e |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 1972 | 2 * Copyright (c) 1998, 2010, 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 * | |
|
1552
c18cbe5936b8
6941466: Oracle rebranding changes for Hotspot repositories
trims
parents:
702
diff
changeset
|
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
|
c18cbe5936b8
6941466: Oracle rebranding changes for Hotspot repositories
trims
parents:
702
diff
changeset
|
20 * or visit www.oracle.com if you need additional information or have any |
|
c18cbe5936b8
6941466: Oracle rebranding changes for Hotspot repositories
trims
parents:
702
diff
changeset
|
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); \ | |
| 85 symbolOop klassname = ((oop)(klassOop))->klass()->klass_part()->name(); \ | |
| 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 } | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
902 /* Too slow for general assert or debug |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
903 void ObjectSynchronizer::verifyInUse (Thread *Self) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
904 ObjectMonitor* mid; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
905 int inusetally = 0; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
906 for (mid = Self->omInUseList; mid != NULL; mid = mid->FreeNext) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
907 inusetally ++; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
908 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
909 assert(inusetally == Self->omInUseCount, "inuse count off"); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
910 |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
911 int freetally = 0; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
912 for (mid = Self->omFreeList; mid != NULL; mid = mid->FreeNext) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
913 freetally ++; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
914 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
915 assert(freetally == Self->omFreeCount, "free count off"); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
916 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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 ++; | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
944 // verifyInUse(Self); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
945 } else { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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() ; | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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 | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1048 void ObjectSynchronizer::omRelease (Thread * Self, ObjectMonitor * m, bool fromPerThreadAlloc) { |
| 0 | 1049 guarantee (m->object() == NULL, "invariant") ; |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1050 |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1051 // Remove from omInUseList |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1052 if (MonitorInUseLists && fromPerThreadAlloc) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1053 ObjectMonitor* curmidinuse = NULL; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1054 for (ObjectMonitor* mid = Self->omInUseList; mid != NULL; ) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1055 if (m == mid) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1056 // extract from per-thread in-use-list |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1057 if (mid == Self->omInUseList) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1058 Self->omInUseList = mid->FreeNext; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1059 } else if (curmidinuse != NULL) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1060 curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1061 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1062 Self->omInUseCount --; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1063 // verifyInUse(Self); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1064 break; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1065 } else { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1066 curmidinuse = mid; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1067 mid = mid->FreeNext; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1068 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1069 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1070 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1071 |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1072 // FreeNext is used for both onInUseList and omFreeList, so clear old before setting new |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1073 m->FreeNext = Self->omFreeList ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1074 Self->omFreeList = m ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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 // | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1085 // Also return the monitors of a moribund thread"s omInUseList to |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1086 // a global gOmInUseList under the global list lock so these |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1087 // will continue to be scanned. |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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; |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1103 if (List != NULL) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1104 ObjectMonitor * s ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1105 for (s = List ; s != NULL ; s = s->FreeNext) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1106 Tally ++ ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1107 Tail = s ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1108 guarantee (s->object() == NULL, "invariant") ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1109 guarantee (!s->is_busy(), "invariant") ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1110 s->set_owner (NULL) ; // redundant but good hygiene |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1111 TEVENT (omFlush - Move one) ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1112 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1113 guarantee (Tail != NULL && List != NULL, "invariant") ; |
| 0 | 1114 } |
| 1115 | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1116 ObjectMonitor * InUseList = Self->omInUseList; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1117 ObjectMonitor * InUseTail = NULL ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1118 int InUseTally = 0; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1119 if (InUseList != NULL) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1120 Self->omInUseList = NULL; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1121 ObjectMonitor *curom; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1122 for (curom = InUseList; curom != NULL; curom = curom->FreeNext) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1123 InUseTail = curom; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1124 InUseTally++; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1125 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1126 // TODO debug |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1127 assert(Self->omInUseCount == InUseTally, "inuse count off"); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1128 Self->omInUseCount = 0; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1129 guarantee (InUseTail != NULL && InUseList != NULL, "invariant"); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1130 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1131 |
| 0 | 1132 Thread::muxAcquire (&ListLock, "omFlush") ; |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1133 if (Tail != NULL) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1134 Tail->FreeNext = gFreeList ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1135 gFreeList = List ; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1136 MonitorFreeCount += Tally; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1137 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1138 |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1139 if (InUseTail != NULL) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1140 InUseTail->FreeNext = gOmInUseList; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1141 gOmInUseList = InUseList; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1142 gOmInUseCount += InUseTally; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1143 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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) { | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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 | |
|
702
b9fba36710f2
6699669: Hotspot server leaves synchronized block with monitor in bad state
xlu
parents:
579
diff
changeset
|
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. | |
|
702
b9fba36710f2
6699669: Hotspot server leaves synchronized block with monitor in bad state
xlu
parents:
579
diff
changeset
|
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() ; | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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. | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1374 // When a thread dies, omFlush() adds the list of active monitors for |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1375 // that thread to a global gOmInUseList acquiring the |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1376 // global list lock. deflate_idle_monitors() acquires the global |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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; | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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 | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1438 // Caller acquires ListLock |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1439 int ObjectSynchronizer::walk_monitor_list(ObjectMonitor** listheadp, |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1440 ObjectMonitor** FreeHeadp, ObjectMonitor** FreeTailp) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1441 ObjectMonitor* mid; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1442 ObjectMonitor* next; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1443 ObjectMonitor* curmidinuse = NULL; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1444 int deflatedcount = 0; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1445 |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1446 for (mid = *listheadp; mid != NULL; ) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1447 oop obj = (oop) mid->object(); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1448 bool deflated = false; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1449 if (obj != NULL) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1450 deflated = deflate_monitor(mid, obj, FreeHeadp, FreeTailp); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1451 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1452 if (deflated) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1453 // extract from per-thread in-use-list |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1454 if (mid == *listheadp) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1455 *listheadp = mid->FreeNext; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1456 } else if (curmidinuse != NULL) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1457 curmidinuse->FreeNext = mid->FreeNext; // maintain the current thread inuselist |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1458 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1459 next = mid->FreeNext; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1460 mid->FreeNext = NULL; // This mid is current tail in the FreeHead list |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1461 mid = next; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1462 deflatedcount++; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1463 } else { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1464 curmidinuse = mid; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1465 mid = mid->FreeNext; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1466 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1467 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1468 return deflatedcount; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1469 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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) { | |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1488 int inUse = 0; |
| 1587 | 1489 for (JavaThread* cur = Threads::first(); cur != NULL; cur = cur->next()) { |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1490 nInCirculation+= cur->omInUseCount; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1491 int deflatedcount = walk_monitor_list(cur->omInUseList_addr(), &FreeHead, &FreeTail); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1492 cur->omInUseCount-= deflatedcount; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1493 // verifyInUse(cur); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1494 nScavenged += deflatedcount; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1495 nInuse += cur->omInUseCount; |
| 1587 | 1496 } |
|
1640
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1497 |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1498 // For moribund threads, scan gOmInUseList |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1499 if (gOmInUseList) { |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1500 nInCirculation += gOmInUseCount; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1501 int deflatedcount = walk_monitor_list((ObjectMonitor **)&gOmInUseList, &FreeHead, &FreeTail); |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1502 gOmInUseCount-= deflatedcount; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1503 nScavenged += deflatedcount; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1504 nInuse += gOmInUseCount; |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
1505 } |
|
bfc89697cccb
6964164: MonitorInUseLists leak of contended objects
acorn
parents:
1589
diff
changeset
|
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 |