1 /* 2 * Copyright (c) 1998, 2021, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/vmSymbols.hpp" 27 #include "jfr/jfrEvents.hpp" 28 #include "logging/log.hpp" 29 #include "logging/logStream.hpp" 30 #include "memory/allocation.inline.hpp" 31 #include "memory/padded.hpp" 32 #include "memory/resourceArea.hpp" 33 #include "memory/universe.hpp" 34 #include "oops/markWord.hpp" 35 #include "oops/oop.inline.hpp" 36 #include "runtime/atomic.hpp" 37 #include "runtime/biasedLocking.hpp" 38 #include "runtime/handles.inline.hpp" 39 #include "runtime/handshake.hpp" 40 #include "runtime/interfaceSupport.inline.hpp" 41 #include "runtime/mutexLocker.hpp" 42 #include "runtime/objectMonitor.hpp" 43 #include "runtime/objectMonitor.inline.hpp" 44 #include "runtime/os.inline.hpp" 45 #include "runtime/osThread.hpp" 46 #include "runtime/perfData.hpp" 47 #include "runtime/safepointMechanism.inline.hpp" 48 #include "runtime/safepointVerifiers.hpp" 49 #include "runtime/sharedRuntime.hpp" 50 #include "runtime/stubRoutines.hpp" 51 #include "runtime/synchronizer.hpp" 52 #include "runtime/thread.inline.hpp" 53 #include "runtime/timer.hpp" 54 #include "runtime/vframe.hpp" 55 #include "runtime/vmThread.hpp" 56 #include "utilities/align.hpp" 57 #include "utilities/dtrace.hpp" 58 #include "utilities/events.hpp" 59 #include "utilities/preserveException.hpp" 60 61 void MonitorList::add(ObjectMonitor* m) { 62 ObjectMonitor* head; 63 do { 64 head = Atomic::load(&_head); 65 m->set_next_om(head); 66 } while (Atomic::cmpxchg(&_head, head, m) != head); 67 68 size_t count = Atomic::add(&_count, 1u); 69 if (count > max()) { 70 Atomic::inc(&_max); 71 } 72 } 73 74 size_t MonitorList::count() const { 75 return Atomic::load(&_count); 76 } 77 78 size_t MonitorList::max() const { 79 return Atomic::load(&_max); 80 } 81 82 // Walk the in-use list and unlink (at most MonitorDeflationMax) deflated 83 // ObjectMonitors. Returns the number of unlinked ObjectMonitors. 84 size_t MonitorList::unlink_deflated(Thread* current, LogStream* ls, 85 elapsedTimer* timer_p, 86 GrowableArray<ObjectMonitor*>* unlinked_list) { 87 size_t unlinked_count = 0; 88 ObjectMonitor* prev = NULL; 89 ObjectMonitor* head = Atomic::load_acquire(&_head); 90 ObjectMonitor* m = head; 91 // The in-use list head can be NULL during the final audit. 92 while (m != NULL) { 93 if (m->is_being_async_deflated()) { 94 // Find next live ObjectMonitor. 95 ObjectMonitor* next = m; 96 do { 97 ObjectMonitor* next_next = next->next_om(); 98 unlinked_count++; 99 unlinked_list->append(next); 100 next = next_next; 101 if (unlinked_count >= (size_t)MonitorDeflationMax) { 102 // Reached the max so bail out on the gathering loop. 103 break; 104 } 105 } while (next != NULL && next->is_being_async_deflated()); 106 if (prev == NULL) { 107 ObjectMonitor* prev_head = Atomic::cmpxchg(&_head, head, next); 108 if (prev_head != head) { 109 // Find new prev ObjectMonitor that just got inserted. 110 for (ObjectMonitor* n = prev_head; n != m; n = n->next_om()) { 111 prev = n; 112 } 113 prev->set_next_om(next); 114 } 115 } else { 116 prev->set_next_om(next); 117 } 118 if (unlinked_count >= (size_t)MonitorDeflationMax) { 119 // Reached the max so bail out on the searching loop. 120 break; 121 } 122 m = next; 123 } else { 124 prev = m; 125 m = m->next_om(); 126 } 127 128 if (current->is_Java_thread()) { 129 // A JavaThread must check for a safepoint/handshake and honor it. 130 ObjectSynchronizer::chk_for_block_req(current->as_Java_thread(), "unlinking", 131 "unlinked_count", unlinked_count, 132 ls, timer_p); 133 } 134 } 135 Atomic::sub(&_count, unlinked_count); 136 return unlinked_count; 137 } 138 139 MonitorList::Iterator MonitorList::iterator() const { 140 return Iterator(Atomic::load_acquire(&_head)); 141 } 142 143 ObjectMonitor* MonitorList::Iterator::next() { 144 ObjectMonitor* current = _current; 145 _current = current->next_om(); 146 return current; 147 } 148 149 // The "core" versions of monitor enter and exit reside in this file. 150 // The interpreter and compilers contain specialized transliterated 151 // variants of the enter-exit fast-path operations. See c2_MacroAssembler_x86.cpp 152 // fast_lock(...) for instance. If you make changes here, make sure to modify the 153 // interpreter, and both C1 and C2 fast-path inline locking code emission. 154 // 155 // ----------------------------------------------------------------------------- 156 157 #ifdef DTRACE_ENABLED 158 159 // Only bother with this argument setup if dtrace is available 160 // TODO-FIXME: probes should not fire when caller is _blocked. assert() accordingly. 161 162 #define DTRACE_MONITOR_PROBE_COMMON(obj, thread) \ 163 char* bytes = NULL; \ 164 int len = 0; \ 165 jlong jtid = SharedRuntime::get_java_tid(thread); \ 166 Symbol* klassname = obj->klass()->name(); \ 167 if (klassname != NULL) { \ 168 bytes = (char*)klassname->bytes(); \ 169 len = klassname->utf8_length(); \ 170 } 171 172 #define DTRACE_MONITOR_WAIT_PROBE(monitor, obj, thread, millis) \ 173 { \ 174 if (DTraceMonitorProbes) { \ 175 DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ 176 HOTSPOT_MONITOR_WAIT(jtid, \ 177 (uintptr_t)(monitor), bytes, len, (millis)); \ 178 } \ 179 } 180 181 #define HOTSPOT_MONITOR_PROBE_notify HOTSPOT_MONITOR_NOTIFY 182 #define HOTSPOT_MONITOR_PROBE_notifyAll HOTSPOT_MONITOR_NOTIFYALL 183 #define HOTSPOT_MONITOR_PROBE_waited HOTSPOT_MONITOR_WAITED 184 185 #define DTRACE_MONITOR_PROBE(probe, monitor, obj, thread) \ 186 { \ 187 if (DTraceMonitorProbes) { \ 188 DTRACE_MONITOR_PROBE_COMMON(obj, thread); \ 189 HOTSPOT_MONITOR_PROBE_##probe(jtid, /* probe = waited */ \ 190 (uintptr_t)(monitor), bytes, len); \ 191 } \ 192 } 193 194 #else // ndef DTRACE_ENABLED 195 196 #define DTRACE_MONITOR_WAIT_PROBE(obj, thread, millis, mon) {;} 197 #define DTRACE_MONITOR_PROBE(probe, obj, thread, mon) {;} 198 199 #endif // ndef DTRACE_ENABLED 200 201 // This exists only as a workaround of dtrace bug 6254741 202 int dtrace_waited_probe(ObjectMonitor* monitor, Handle obj, Thread* thr) { 203 DTRACE_MONITOR_PROBE(waited, monitor, obj(), thr); 204 return 0; 205 } 206 207 static const int NINFLATIONLOCKS = 256; 208 static os::PlatformMutex* gInflationLocks[NINFLATIONLOCKS]; 209 210 void ObjectSynchronizer::initialize() { 211 for (int i = 0; i < NINFLATIONLOCKS; i++) { 212 gInflationLocks[i] = new os::PlatformMutex(); 213 } 214 // Start the ceiling with the estimate for one thread. 215 set_in_use_list_ceiling(AvgMonitorsPerThreadEstimate); 216 } 217 218 MonitorList ObjectSynchronizer::_in_use_list; 219 // monitors_used_above_threshold() policy is as follows: 220 // 221 // The ratio of the current _in_use_list count to the ceiling is used 222 // to determine if we are above MonitorUsedDeflationThreshold and need 223 // to do an async monitor deflation cycle. The ceiling is increased by 224 // AvgMonitorsPerThreadEstimate when a thread is added to the system 225 // and is decreased by AvgMonitorsPerThreadEstimate when a thread is 226 // removed from the system. 227 // 228 // Note: If the _in_use_list max exceeds the ceiling, then 229 // monitors_used_above_threshold() will use the in_use_list max instead 230 // of the thread count derived ceiling because we have used more 231 // ObjectMonitors than the estimated average. 232 // 233 // Note: If deflate_idle_monitors() has NoAsyncDeflationProgressMax 234 // no-progress async monitor deflation cycles in a row, then the ceiling 235 // is adjusted upwards by monitors_used_above_threshold(). 236 // 237 // Start the ceiling with the estimate for one thread in initialize() 238 // which is called after cmd line options are processed. 239 static size_t _in_use_list_ceiling = 0; 240 bool volatile ObjectSynchronizer::_is_async_deflation_requested = false; 241 bool volatile ObjectSynchronizer::_is_final_audit = false; 242 jlong ObjectSynchronizer::_last_async_deflation_time_ns = 0; 243 static uintx _no_progress_cnt = 0; 244 245 // =====================> Quick functions 246 247 // The quick_* forms are special fast-path variants used to improve 248 // performance. In the simplest case, a "quick_*" implementation could 249 // simply return false, in which case the caller will perform the necessary 250 // state transitions and call the slow-path form. 251 // The fast-path is designed to handle frequently arising cases in an efficient 252 // manner and is just a degenerate "optimistic" variant of the slow-path. 253 // returns true -- to indicate the call was satisfied. 254 // returns false -- to indicate the call needs the services of the slow-path. 255 // A no-loitering ordinance is in effect for code in the quick_* family 256 // operators: safepoints or indefinite blocking (blocking that might span a 257 // safepoint) are forbidden. Generally the thread_state() is _in_Java upon 258 // entry. 259 // 260 // Consider: An interesting optimization is to have the JIT recognize the 261 // following common idiom: 262 // synchronized (someobj) { .... ; notify(); } 263 // That is, we find a notify() or notifyAll() call that immediately precedes 264 // the monitorexit operation. In that case the JIT could fuse the operations 265 // into a single notifyAndExit() runtime primitive. 266 267 bool ObjectSynchronizer::quick_notify(oopDesc* obj, JavaThread* current, bool all) { 268 assert(current->thread_state() == _thread_in_Java, "invariant"); 269 NoSafepointVerifier nsv; 270 if (obj == NULL) return false; // slow-path for invalid obj 271 const markWord mark = obj->mark(); 272 273 if (mark.has_locker() && current->is_lock_owned((address)mark.locker())) { 274 // Degenerate notify 275 // stack-locked by caller so by definition the implied waitset is empty. 276 return true; 277 } 278 279 if (mark.has_monitor()) { 280 ObjectMonitor* const mon = mark.monitor(); 281 assert(mon->object() == oop(obj), "invariant"); 282 if (mon->owner() != current) return false; // slow-path for IMS exception 283 284 if (mon->first_waiter() != NULL) { 285 // We have one or more waiters. Since this is an inflated monitor 286 // that we own, we can transfer one or more threads from the waitset 287 // to the entrylist here and now, avoiding the slow-path. 288 if (all) { 289 DTRACE_MONITOR_PROBE(notifyAll, mon, obj, current); 290 } else { 291 DTRACE_MONITOR_PROBE(notify, mon, obj, current); 292 } 293 int free_count = 0; 294 do { 295 mon->INotify(current); 296 ++free_count; 297 } while (mon->first_waiter() != NULL && all); 298 OM_PERFDATA_OP(Notifications, inc(free_count)); 299 } 300 return true; 301 } 302 303 // biased locking and any other IMS exception states take the slow-path 304 return false; 305 } 306 307 308 // The LockNode emitted directly at the synchronization site would have 309 // been too big if it were to have included support for the cases of inflated 310 // recursive enter and exit, so they go here instead. 311 // Note that we can't safely call AsyncPrintJavaStack() from within 312 // quick_enter() as our thread state remains _in_Java. 313 314 bool ObjectSynchronizer::quick_enter(oop obj, JavaThread* current, 315 BasicLock * lock) { 316 assert(current->thread_state() == _thread_in_Java, "invariant"); 317 NoSafepointVerifier nsv; 318 if (obj == NULL) return false; // Need to throw NPE 319 320 if (obj->klass()->is_value_based()) { 321 return false; 322 } 323 324 const markWord mark = obj->mark(); 325 326 if (mark.has_monitor()) { 327 ObjectMonitor* const m = mark.monitor(); 328 // An async deflation or GC can race us before we manage to make 329 // the ObjectMonitor busy by setting the owner below. If we detect 330 // that race we just bail out to the slow-path here. 331 if (m->object_peek() == NULL) { 332 return false; 333 } 334 JavaThread* const owner = (JavaThread*) m->owner_raw(); 335 336 // Lock contention and Transactional Lock Elision (TLE) diagnostics 337 // and observability 338 // Case: light contention possibly amenable to TLE 339 // Case: TLE inimical operations such as nested/recursive synchronization 340 341 if (owner == current) { 342 m->_recursions++; 343 return true; 344 } 345 346 // This Java Monitor is inflated so obj's header will never be 347 // displaced to this thread's BasicLock. Make the displaced header 348 // non-NULL so this BasicLock is not seen as recursive nor as 349 // being locked. We do this unconditionally so that this thread's 350 // BasicLock cannot be mis-interpreted by any stack walkers. For 351 // performance reasons, stack walkers generally first check for 352 // Biased Locking in the object's header, the second check is for 353 // stack-locking in the object's header, the third check is for 354 // recursive stack-locking in the displaced header in the BasicLock, 355 // and last are the inflated Java Monitor (ObjectMonitor) checks. 356 lock->set_displaced_header(markWord::unused_mark()); 357 358 if (owner == NULL && m->try_set_owner_from(NULL, current) == NULL) { 359 assert(m->_recursions == 0, "invariant"); 360 return true; 361 } 362 } 363 364 // Note that we could inflate in quick_enter. 365 // This is likely a useful optimization 366 // Critically, in quick_enter() we must not: 367 // -- perform bias revocation, or 368 // -- block indefinitely, or 369 // -- reach a safepoint 370 371 return false; // revert to slow-path 372 } 373 374 // Handle notifications when synchronizing on value based classes 375 void ObjectSynchronizer::handle_sync_on_value_based_class(Handle obj, JavaThread* current) { 376 frame last_frame = current->last_frame(); 377 bool bcp_was_adjusted = false; 378 // Don't decrement bcp if it points to the frame's first instruction. This happens when 379 // handle_sync_on_value_based_class() is called because of a synchronized method. There 380 // is no actual monitorenter instruction in the byte code in this case. 381 if (last_frame.is_interpreted_frame() && 382 (last_frame.interpreter_frame_method()->code_base() < last_frame.interpreter_frame_bcp())) { 383 // adjust bcp to point back to monitorenter so that we print the correct line numbers 384 last_frame.interpreter_frame_set_bcp(last_frame.interpreter_frame_bcp() - 1); 385 bcp_was_adjusted = true; 386 } 387 388 if (DiagnoseSyncOnValueBasedClasses == FATAL_EXIT) { 389 ResourceMark rm(current); 390 stringStream ss; 391 current->print_stack_on(&ss); 392 char* base = (char*)strstr(ss.base(), "at"); 393 char* newline = (char*)strchr(ss.base(), '\n'); 394 if (newline != NULL) { 395 *newline = '\0'; 396 } 397 fatal("Synchronizing on object " INTPTR_FORMAT " of klass %s %s", p2i(obj()), obj->klass()->external_name(), base); 398 } else { 399 assert(DiagnoseSyncOnValueBasedClasses == LOG_WARNING, "invalid value for DiagnoseSyncOnValueBasedClasses"); 400 ResourceMark rm(current); 401 Log(valuebasedclasses) vblog; 402 403 vblog.info("Synchronizing on object " INTPTR_FORMAT " of klass %s", p2i(obj()), obj->klass()->external_name()); 404 if (current->has_last_Java_frame()) { 405 LogStream info_stream(vblog.info()); 406 current->print_stack_on(&info_stream); 407 } else { 408 vblog.info("Cannot find the last Java frame"); 409 } 410 411 EventSyncOnValueBasedClass event; 412 if (event.should_commit()) { 413 event.set_valueBasedClass(obj->klass()); 414 event.commit(); 415 } 416 } 417 418 if (bcp_was_adjusted) { 419 last_frame.interpreter_frame_set_bcp(last_frame.interpreter_frame_bcp() + 1); 420 } 421 } 422 423 // ----------------------------------------------------------------------------- 424 // Monitor Enter/Exit 425 // The interpreter and compiler assembly code tries to lock using the fast path 426 // of this algorithm. Make sure to update that code if the following function is 427 // changed. The implementation is extremely sensitive to race condition. Be careful. 428 429 void ObjectSynchronizer::enter(Handle obj, BasicLock* lock, JavaThread* current) { 430 if (obj->klass()->is_value_based()) { 431 handle_sync_on_value_based_class(obj, current); 432 } 433 434 if (UseBiasedLocking) { 435 BiasedLocking::revoke(current, obj); 436 } 437 438 markWord mark = obj->mark(); 439 assert(!mark.has_bias_pattern(), "should not see bias pattern here"); 440 441 if (mark.is_neutral()) { 442 // Anticipate successful CAS -- the ST of the displaced mark must 443 // be visible <= the ST performed by the CAS. 444 lock->set_displaced_header(mark); 445 if (mark == obj()->cas_set_mark(markWord::from_pointer(lock), mark)) { 446 return; 447 } 448 // Fall through to inflate() ... 449 } else if (mark.has_locker() && 450 current->is_lock_owned((address)mark.locker())) { 451 assert(lock != mark.locker(), "must not re-lock the same lock"); 452 assert(lock != (BasicLock*)obj->mark().value(), "don't relock with same BasicLock"); 453 lock->set_displaced_header(markWord::from_pointer(NULL)); 454 return; 455 } 456 457 // The object header will never be displaced to this lock, 458 // so it does not matter what the value is, except that it 459 // must be non-zero to avoid looking like a re-entrant lock, 460 // and must not look locked either. 461 lock->set_displaced_header(markWord::unused_mark()); 462 // An async deflation can race after the inflate() call and before 463 // enter() can make the ObjectMonitor busy. enter() returns false if 464 // we have lost the race to async deflation and we simply try again. 465 while (true) { 466 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_monitor_enter); 467 if (monitor->enter(current)) { 468 return; 469 } 470 } 471 } 472 473 void ObjectSynchronizer::exit(oop object, BasicLock* lock, JavaThread* current) { 474 markWord mark = object->mark(); 475 // We cannot check for Biased Locking if we are racing an inflation. 476 assert(mark == markWord::INFLATING() || 477 !mark.has_bias_pattern(), "should not see bias pattern here"); 478 479 markWord dhw = lock->displaced_header(); 480 if (dhw.value() == 0) { 481 // If the displaced header is NULL, then this exit matches up with 482 // a recursive enter. No real work to do here except for diagnostics. 483 #ifndef PRODUCT 484 if (mark != markWord::INFLATING()) { 485 // Only do diagnostics if we are not racing an inflation. Simply 486 // exiting a recursive enter of a Java Monitor that is being 487 // inflated is safe; see the has_monitor() comment below. 488 assert(!mark.is_neutral(), "invariant"); 489 assert(!mark.has_locker() || 490 current->is_lock_owned((address)mark.locker()), "invariant"); 491 if (mark.has_monitor()) { 492 // The BasicLock's displaced_header is marked as a recursive 493 // enter and we have an inflated Java Monitor (ObjectMonitor). 494 // This is a special case where the Java Monitor was inflated 495 // after this thread entered the stack-lock recursively. When a 496 // Java Monitor is inflated, we cannot safely walk the Java 497 // Monitor owner's stack and update the BasicLocks because a 498 // Java Monitor can be asynchronously inflated by a thread that 499 // does not own the Java Monitor. 500 ObjectMonitor* m = mark.monitor(); 501 assert(m->object()->mark() == mark, "invariant"); 502 assert(m->is_entered(current), "invariant"); 503 } 504 } 505 #endif 506 return; 507 } 508 509 if (mark == markWord::from_pointer(lock)) { 510 // If the object is stack-locked by the current thread, try to 511 // swing the displaced header from the BasicLock back to the mark. 512 assert(dhw.is_neutral(), "invariant"); 513 if (object->cas_set_mark(dhw, mark) == mark) { 514 return; 515 } 516 } 517 518 // We have to take the slow-path of possible inflation and then exit. 519 // The ObjectMonitor* can't be async deflated until ownership is 520 // dropped inside exit() and the ObjectMonitor* must be !is_busy(). 521 ObjectMonitor* monitor = inflate(current, object, inflate_cause_vm_internal); 522 monitor->exit(current); 523 } 524 525 // ----------------------------------------------------------------------------- 526 // Class Loader support to workaround deadlocks on the class loader lock objects 527 // Also used by GC 528 // complete_exit()/reenter() are used to wait on a nested lock 529 // i.e. to give up an outer lock completely and then re-enter 530 // Used when holding nested locks - lock acquisition order: lock1 then lock2 531 // 1) complete_exit lock1 - saving recursion count 532 // 2) wait on lock2 533 // 3) when notified on lock2, unlock lock2 534 // 4) reenter lock1 with original recursion count 535 // 5) lock lock2 536 // NOTE: must use heavy weight monitor to handle complete_exit/reenter() 537 intx ObjectSynchronizer::complete_exit(Handle obj, JavaThread* current) { 538 if (UseBiasedLocking) { 539 BiasedLocking::revoke(current, obj); 540 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now"); 541 } 542 543 // The ObjectMonitor* can't be async deflated until ownership is 544 // dropped inside exit() and the ObjectMonitor* must be !is_busy(). 545 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_vm_internal); 546 intptr_t ret_code = monitor->complete_exit(current); 547 return ret_code; 548 } 549 550 // NOTE: must use heavy weight monitor to handle complete_exit/reenter() 551 void ObjectSynchronizer::reenter(Handle obj, intx recursions, JavaThread* current) { 552 if (UseBiasedLocking) { 553 BiasedLocking::revoke(current, obj); 554 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now"); 555 } 556 557 // An async deflation can race after the inflate() call and before 558 // reenter() -> enter() can make the ObjectMonitor busy. reenter() -> 559 // enter() returns false if we have lost the race to async deflation 560 // and we simply try again. 561 while (true) { 562 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_vm_internal); 563 if (monitor->reenter(recursions, current)) { 564 return; 565 } 566 } 567 } 568 569 // ----------------------------------------------------------------------------- 570 // JNI locks on java objects 571 // NOTE: must use heavy weight monitor to handle jni monitor enter 572 void ObjectSynchronizer::jni_enter(Handle obj, JavaThread* current) { 573 if (obj->klass()->is_value_based()) { 574 handle_sync_on_value_based_class(obj, current); 575 } 576 577 // the current locking is from JNI instead of Java code 578 if (UseBiasedLocking) { 579 BiasedLocking::revoke(current, obj); 580 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now"); 581 } 582 current->set_current_pending_monitor_is_from_java(false); 583 // An async deflation can race after the inflate() call and before 584 // enter() can make the ObjectMonitor busy. enter() returns false if 585 // we have lost the race to async deflation and we simply try again. 586 while (true) { 587 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_jni_enter); 588 if (monitor->enter(current)) { 589 break; 590 } 591 } 592 current->set_current_pending_monitor_is_from_java(true); 593 } 594 595 // NOTE: must use heavy weight monitor to handle jni monitor exit 596 void ObjectSynchronizer::jni_exit(oop obj, TRAPS) { 597 JavaThread* current = THREAD; 598 if (UseBiasedLocking) { 599 Handle h_obj(current, obj); 600 BiasedLocking::revoke(current, h_obj); 601 obj = h_obj(); 602 } 603 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now"); 604 605 // The ObjectMonitor* can't be async deflated until ownership is 606 // dropped inside exit() and the ObjectMonitor* must be !is_busy(). 607 ObjectMonitor* monitor = inflate(current, obj, inflate_cause_jni_exit); 608 // If this thread has locked the object, exit the monitor. We 609 // intentionally do not use CHECK on check_owner because we must exit the 610 // monitor even if an exception was already pending. 611 if (monitor->check_owner(THREAD)) { 612 monitor->exit(current); 613 } 614 } 615 616 // ----------------------------------------------------------------------------- 617 // Internal VM locks on java objects 618 // standard constructor, allows locking failures 619 ObjectLocker::ObjectLocker(Handle obj, JavaThread* thread) { 620 _thread = thread; 621 _thread->check_for_valid_safepoint_state(); 622 _obj = obj; 623 624 if (_obj() != NULL) { 625 ObjectSynchronizer::enter(_obj, &_lock, _thread); 626 } 627 } 628 629 ObjectLocker::~ObjectLocker() { 630 if (_obj() != NULL) { 631 ObjectSynchronizer::exit(_obj(), &_lock, _thread); 632 } 633 } 634 635 636 // ----------------------------------------------------------------------------- 637 // Wait/Notify/NotifyAll 638 // NOTE: must use heavy weight monitor to handle wait() 639 int ObjectSynchronizer::wait(Handle obj, jlong millis, TRAPS) { 640 JavaThread* current = THREAD; 641 if (UseBiasedLocking) { 642 BiasedLocking::revoke(current, obj); 643 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now"); 644 } 645 if (millis < 0) { 646 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative"); 647 } 648 // The ObjectMonitor* can't be async deflated because the _waiters 649 // field is incremented before ownership is dropped and decremented 650 // after ownership is regained. 651 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_wait); 652 653 DTRACE_MONITOR_WAIT_PROBE(monitor, obj(), current, millis); 654 monitor->wait(millis, true, THREAD); // Not CHECK as we need following code 655 656 // This dummy call is in place to get around dtrace bug 6254741. Once 657 // that's fixed we can uncomment the following line, remove the call 658 // and change this function back into a "void" func. 659 // DTRACE_MONITOR_PROBE(waited, monitor, obj(), THREAD); 660 int ret_code = dtrace_waited_probe(monitor, obj, THREAD); 661 return ret_code; 662 } 663 664 // No exception are possible in this case as we only use this internally when locking is 665 // correct and we have to wait until notified - so no interrupts or timeouts. 666 void ObjectSynchronizer::wait_uninterruptibly(Handle obj, JavaThread* current) { 667 if (UseBiasedLocking) { 668 BiasedLocking::revoke(current, obj); 669 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now"); 670 } 671 // The ObjectMonitor* can't be async deflated because the _waiters 672 // field is incremented before ownership is dropped and decremented 673 // after ownership is regained. 674 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_wait); 675 monitor->wait(0 /* wait-forever */, false /* not interruptible */, current); 676 } 677 678 void ObjectSynchronizer::notify(Handle obj, TRAPS) { 679 JavaThread* current = THREAD; 680 if (UseBiasedLocking) { 681 BiasedLocking::revoke(current, obj); 682 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now"); 683 } 684 685 markWord mark = obj->mark(); 686 if (mark.has_locker() && current->is_lock_owned((address)mark.locker())) { 687 // Not inflated so there can't be any waiters to notify. 688 return; 689 } 690 // The ObjectMonitor* can't be async deflated until ownership is 691 // dropped by the calling thread. 692 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_notify); 693 monitor->notify(CHECK); 694 } 695 696 // NOTE: see comment of notify() 697 void ObjectSynchronizer::notifyall(Handle obj, TRAPS) { 698 JavaThread* current = THREAD; 699 if (UseBiasedLocking) { 700 BiasedLocking::revoke(current, obj); 701 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now"); 702 } 703 704 markWord mark = obj->mark(); 705 if (mark.has_locker() && current->is_lock_owned((address)mark.locker())) { 706 // Not inflated so there can't be any waiters to notify. 707 return; 708 } 709 // The ObjectMonitor* can't be async deflated until ownership is 710 // dropped by the calling thread. 711 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_notify); 712 monitor->notifyAll(CHECK); 713 } 714 715 // ----------------------------------------------------------------------------- 716 // Hash Code handling 717 718 struct SharedGlobals { 719 char _pad_prefix[OM_CACHE_LINE_SIZE]; 720 // This is a highly shared mostly-read variable. 721 // To avoid false-sharing it needs to be the sole occupant of a cache line. 722 volatile int stw_random; 723 DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(volatile int)); 724 // Hot RW variable -- Sequester to avoid false-sharing 725 volatile int hc_sequence; 726 DEFINE_PAD_MINUS_SIZE(2, OM_CACHE_LINE_SIZE, sizeof(volatile int)); 727 }; 728 729 static SharedGlobals GVars; 730 731 static markWord read_stable_mark(oop obj) { 732 markWord mark = obj->mark(); 733 if (!mark.is_being_inflated()) { 734 return mark; // normal fast-path return 735 } 736 737 int its = 0; 738 for (;;) { 739 markWord mark = obj->mark(); 740 if (!mark.is_being_inflated()) { 741 return mark; // normal fast-path return 742 } 743 744 // The object is being inflated by some other thread. 745 // The caller of read_stable_mark() must wait for inflation to complete. 746 // Avoid live-lock. 747 748 ++its; 749 if (its > 10000 || !os::is_MP()) { 750 if (its & 1) { 751 os::naked_yield(); 752 } else { 753 // Note that the following code attenuates the livelock problem but is not 754 // a complete remedy. A more complete solution would require that the inflating 755 // thread hold the associated inflation lock. The following code simply restricts 756 // the number of spinners to at most one. We'll have N-2 threads blocked 757 // on the inflationlock, 1 thread holding the inflation lock and using 758 // a yield/park strategy, and 1 thread in the midst of inflation. 759 // A more refined approach would be to change the encoding of INFLATING 760 // to allow encapsulation of a native thread pointer. Threads waiting for 761 // inflation to complete would use CAS to push themselves onto a singly linked 762 // list rooted at the markword. Once enqueued, they'd loop, checking a per-thread flag 763 // and calling park(). When inflation was complete the thread that accomplished inflation 764 // would detach the list and set the markword to inflated with a single CAS and 765 // then for each thread on the list, set the flag and unpark() the thread. 766 767 // Index into the lock array based on the current object address. 768 static_assert(is_power_of_2(NINFLATIONLOCKS), "must be"); 769 int ix = (cast_from_oop<intptr_t>(obj) >> 5) & (NINFLATIONLOCKS-1); 770 int YieldThenBlock = 0; 771 assert(ix >= 0 && ix < NINFLATIONLOCKS, "invariant"); 772 gInflationLocks[ix]->lock(); 773 while (obj->mark() == markWord::INFLATING()) { 774 // Beware: naked_yield() is advisory and has almost no effect on some platforms 775 // so we periodically call current->_ParkEvent->park(1). 776 // We use a mixed spin/yield/block mechanism. 777 if ((YieldThenBlock++) >= 16) { 778 Thread::current()->_ParkEvent->park(1); 779 } else { 780 os::naked_yield(); 781 } 782 } 783 gInflationLocks[ix]->unlock(); 784 } 785 } else { 786 SpinPause(); // SMP-polite spinning 787 } 788 } 789 } 790 791 // hashCode() generation : 792 // 793 // Possibilities: 794 // * MD5Digest of {obj,stw_random} 795 // * CRC32 of {obj,stw_random} or any linear-feedback shift register function. 796 // * A DES- or AES-style SBox[] mechanism 797 // * One of the Phi-based schemes, such as: 798 // 2654435761 = 2^32 * Phi (golden ratio) 799 // HashCodeValue = ((uintptr_t(obj) >> 3) * 2654435761) ^ GVars.stw_random ; 800 // * A variation of Marsaglia's shift-xor RNG scheme. 801 // * (obj ^ stw_random) is appealing, but can result 802 // in undesirable regularity in the hashCode values of adjacent objects 803 // (objects allocated back-to-back, in particular). This could potentially 804 // result in hashtable collisions and reduced hashtable efficiency. 805 // There are simple ways to "diffuse" the middle address bits over the 806 // generated hashCode values: 807 808 static inline intptr_t get_next_hash(Thread* current, oop obj) { 809 intptr_t value = 0; 810 if (hashCode == 0) { 811 // This form uses global Park-Miller RNG. 812 // On MP system we'll have lots of RW access to a global, so the 813 // mechanism induces lots of coherency traffic. 814 value = os::random(); 815 } else if (hashCode == 1) { 816 // This variation has the property of being stable (idempotent) 817 // between STW operations. This can be useful in some of the 1-0 818 // synchronization schemes. 819 intptr_t addr_bits = cast_from_oop<intptr_t>(obj) >> 3; 820 value = addr_bits ^ (addr_bits >> 5) ^ GVars.stw_random; 821 } else if (hashCode == 2) { 822 value = 1; // for sensitivity testing 823 } else if (hashCode == 3) { 824 value = ++GVars.hc_sequence; 825 } else if (hashCode == 4) { 826 value = cast_from_oop<intptr_t>(obj); 827 } else { 828 // Marsaglia's xor-shift scheme with thread-specific state 829 // This is probably the best overall implementation -- we'll 830 // likely make this the default in future releases. 831 unsigned t = current->_hashStateX; 832 t ^= (t << 11); 833 current->_hashStateX = current->_hashStateY; 834 current->_hashStateY = current->_hashStateZ; 835 current->_hashStateZ = current->_hashStateW; 836 unsigned v = current->_hashStateW; 837 v = (v ^ (v >> 19)) ^ (t ^ (t >> 8)); 838 current->_hashStateW = v; 839 value = v; 840 } 841 842 value &= markWord::hash_mask; 843 if (value == 0) value = 0xBAD; 844 assert(value != markWord::no_hash, "invariant"); 845 return value; 846 } 847 848 intptr_t ObjectSynchronizer::FastHashCode(Thread* current, oop obj) { 849 if (UseBiasedLocking) { 850 // NOTE: many places throughout the JVM do not expect a safepoint 851 // to be taken here. However, we only ever bias Java instances and all 852 // of the call sites of identity_hash that might revoke biases have 853 // been checked to make sure they can handle a safepoint. The 854 // added check of the bias pattern is to avoid useless calls to 855 // thread-local storage. 856 if (obj->mark().has_bias_pattern()) { 857 // Handle for oop obj in case of STW safepoint 858 Handle hobj(current, obj); 859 if (SafepointSynchronize::is_at_safepoint()) { 860 BiasedLocking::revoke_at_safepoint(hobj); 861 } else { 862 BiasedLocking::revoke(current->as_Java_thread(), hobj); 863 } 864 obj = hobj(); 865 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now"); 866 } 867 } 868 869 while (true) { 870 ObjectMonitor* monitor = NULL; 871 markWord temp, test; 872 intptr_t hash; 873 markWord mark = read_stable_mark(obj); 874 875 // object should remain ineligible for biased locking 876 assert(!mark.has_bias_pattern(), "invariant"); 877 878 if (mark.is_neutral()) { // if this is a normal header 879 hash = mark.hash(); 880 if (hash != 0) { // if it has a hash, just return it 881 return hash; 882 } 883 hash = get_next_hash(current, obj); // get a new hash 884 temp = mark.copy_set_hash(hash); // merge the hash into header 885 // try to install the hash 886 test = obj->cas_set_mark(temp, mark); 887 if (test == mark) { // if the hash was installed, return it 888 return hash; 889 } 890 // Failed to install the hash. It could be that another thread 891 // installed the hash just before our attempt or inflation has 892 // occurred or... so we fall thru to inflate the monitor for 893 // stability and then install the hash. 894 } else if (mark.has_monitor()) { 895 monitor = mark.monitor(); 896 temp = monitor->header(); 897 assert(temp.is_neutral(), "invariant: header=" INTPTR_FORMAT, temp.value()); 898 hash = temp.hash(); 899 if (hash != 0) { 900 // It has a hash. 901 902 // Separate load of dmw/header above from the loads in 903 // is_being_async_deflated(). 904 905 // dmw/header and _contentions may get written by different threads. 906 // Make sure to observe them in the same order when having several observers. 907 OrderAccess::loadload_for_IRIW(); 908 909 if (monitor->is_being_async_deflated()) { 910 // But we can't safely use the hash if we detect that async 911 // deflation has occurred. So we attempt to restore the 912 // header/dmw to the object's header so that we only retry 913 // once if the deflater thread happens to be slow. 914 monitor->install_displaced_markword_in_object(obj); 915 continue; 916 } 917 return hash; 918 } 919 // Fall thru so we only have one place that installs the hash in 920 // the ObjectMonitor. 921 } else if (current->is_lock_owned((address)mark.locker())) { 922 // This is a stack lock owned by the calling thread so fetch the 923 // displaced markWord from the BasicLock on the stack. 924 temp = mark.displaced_mark_helper(); 925 assert(temp.is_neutral(), "invariant: header=" INTPTR_FORMAT, temp.value()); 926 hash = temp.hash(); 927 if (hash != 0) { // if it has a hash, just return it 928 return hash; 929 } 930 // WARNING: 931 // The displaced header in the BasicLock on a thread's stack 932 // is strictly immutable. It CANNOT be changed in ANY cases. 933 // So we have to inflate the stack lock into an ObjectMonitor 934 // even if the current thread owns the lock. The BasicLock on 935 // a thread's stack can be asynchronously read by other threads 936 // during an inflate() call so any change to that stack memory 937 // may not propagate to other threads correctly. 938 } 939 940 // Inflate the monitor to set the hash. 941 942 // An async deflation can race after the inflate() call and before we 943 // can update the ObjectMonitor's header with the hash value below. 944 monitor = inflate(current, obj, inflate_cause_hash_code); 945 // Load ObjectMonitor's header/dmw field and see if it has a hash. 946 mark = monitor->header(); 947 assert(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT, mark.value()); 948 hash = mark.hash(); 949 if (hash == 0) { // if it does not have a hash 950 hash = get_next_hash(current, obj); // get a new hash 951 temp = mark.copy_set_hash(hash) ; // merge the hash into header 952 assert(temp.is_neutral(), "invariant: header=" INTPTR_FORMAT, temp.value()); 953 uintptr_t v = Atomic::cmpxchg((volatile uintptr_t*)monitor->header_addr(), mark.value(), temp.value()); 954 test = markWord(v); 955 if (test != mark) { 956 // The attempt to update the ObjectMonitor's header/dmw field 957 // did not work. This can happen if another thread managed to 958 // merge in the hash just before our cmpxchg(). 959 // If we add any new usages of the header/dmw field, this code 960 // will need to be updated. 961 hash = test.hash(); 962 assert(test.is_neutral(), "invariant: header=" INTPTR_FORMAT, test.value()); 963 assert(hash != 0, "should only have lost the race to a thread that set a non-zero hash"); 964 } 965 if (monitor->is_being_async_deflated()) { 966 // If we detect that async deflation has occurred, then we 967 // attempt to restore the header/dmw to the object's header 968 // so that we only retry once if the deflater thread happens 969 // to be slow. 970 monitor->install_displaced_markword_in_object(obj); 971 continue; 972 } 973 } 974 // We finally get the hash. 975 return hash; 976 } 977 } 978 979 // Deprecated -- use FastHashCode() instead. 980 981 intptr_t ObjectSynchronizer::identity_hash_value_for(Handle obj) { 982 return FastHashCode(Thread::current(), obj()); 983 } 984 985 986 bool ObjectSynchronizer::current_thread_holds_lock(JavaThread* current, 987 Handle h_obj) { 988 if (UseBiasedLocking) { 989 BiasedLocking::revoke(current, h_obj); 990 assert(!h_obj->mark().has_bias_pattern(), "biases should be revoked by now"); 991 } 992 993 assert(current == JavaThread::current(), "Can only be called on current thread"); 994 oop obj = h_obj(); 995 996 markWord mark = read_stable_mark(obj); 997 998 // Uncontended case, header points to stack 999 if (mark.has_locker()) { 1000 return current->is_lock_owned((address)mark.locker()); 1001 } 1002 // Contended case, header points to ObjectMonitor (tagged pointer) 1003 if (mark.has_monitor()) { 1004 // The first stage of async deflation does not affect any field 1005 // used by this comparison so the ObjectMonitor* is usable here. 1006 ObjectMonitor* monitor = mark.monitor(); 1007 return monitor->is_entered(current) != 0; 1008 } 1009 // Unlocked case, header in place 1010 assert(mark.is_neutral(), "sanity check"); 1011 return false; 1012 } 1013 1014 // FIXME: jvmti should call this 1015 JavaThread* ObjectSynchronizer::get_lock_owner(ThreadsList * t_list, Handle h_obj) { 1016 if (UseBiasedLocking) { 1017 if (SafepointSynchronize::is_at_safepoint()) { 1018 BiasedLocking::revoke_at_safepoint(h_obj); 1019 } else { 1020 BiasedLocking::revoke(JavaThread::current(), h_obj); 1021 } 1022 assert(!h_obj->mark().has_bias_pattern(), "biases should be revoked by now"); 1023 } 1024 1025 oop obj = h_obj(); 1026 address owner = NULL; 1027 1028 markWord mark = read_stable_mark(obj); 1029 1030 // Uncontended case, header points to stack 1031 if (mark.has_locker()) { 1032 owner = (address) mark.locker(); 1033 } 1034 1035 // Contended case, header points to ObjectMonitor (tagged pointer) 1036 else if (mark.has_monitor()) { 1037 // The first stage of async deflation does not affect any field 1038 // used by this comparison so the ObjectMonitor* is usable here. 1039 ObjectMonitor* monitor = mark.monitor(); 1040 assert(monitor != NULL, "monitor should be non-null"); 1041 owner = (address) monitor->owner(); 1042 } 1043 1044 if (owner != NULL) { 1045 // owning_thread_from_monitor_owner() may also return NULL here 1046 return Threads::owning_thread_from_monitor_owner(t_list, owner); 1047 } 1048 1049 // Unlocked case, header in place 1050 // Cannot have assertion since this object may have been 1051 // locked by another thread when reaching here. 1052 // assert(mark.is_neutral(), "sanity check"); 1053 1054 return NULL; 1055 } 1056 1057 // Visitors ... 1058 1059 void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure, JavaThread* thread) { 1060 MonitorList::Iterator iter = _in_use_list.iterator(); 1061 while (iter.has_next()) { 1062 ObjectMonitor* mid = iter.next(); 1063 if (mid->owner() != thread) { 1064 continue; 1065 } 1066 if (!mid->is_being_async_deflated() && mid->object_peek() != NULL) { 1067 // Only process with closure if the object is set. 1068 1069 // monitors_iterate() is only called at a safepoint or when the 1070 // target thread is suspended or when the target thread is 1071 // operating on itself. The current closures in use today are 1072 // only interested in an owned ObjectMonitor and ownership 1073 // cannot be dropped under the calling contexts so the 1074 // ObjectMonitor cannot be async deflated. 1075 closure->do_monitor(mid); 1076 } 1077 } 1078 } 1079 1080 static bool monitors_used_above_threshold(MonitorList* list) { 1081 if (MonitorUsedDeflationThreshold == 0) { // disabled case is easy 1082 return false; 1083 } 1084 // Start with ceiling based on a per-thread estimate: 1085 size_t ceiling = ObjectSynchronizer::in_use_list_ceiling(); 1086 size_t old_ceiling = ceiling; 1087 if (ceiling < list->max()) { 1088 // The max used by the system has exceeded the ceiling so use that: 1089 ceiling = list->max(); 1090 } 1091 size_t monitors_used = list->count(); 1092 if (monitors_used == 0) { // empty list is easy 1093 return false; 1094 } 1095 if (NoAsyncDeflationProgressMax != 0 && 1096 _no_progress_cnt >= NoAsyncDeflationProgressMax) { 1097 float remainder = (100.0 - MonitorUsedDeflationThreshold) / 100.0; 1098 size_t new_ceiling = ceiling + (ceiling * remainder) + 1; 1099 ObjectSynchronizer::set_in_use_list_ceiling(new_ceiling); 1100 log_info(monitorinflation)("Too many deflations without progress; " 1101 "bumping in_use_list_ceiling from " SIZE_FORMAT 1102 " to " SIZE_FORMAT, old_ceiling, new_ceiling); 1103 _no_progress_cnt = 0; 1104 ceiling = new_ceiling; 1105 } 1106 1107 // Check if our monitor usage is above the threshold: 1108 size_t monitor_usage = (monitors_used * 100LL) / ceiling; 1109 return int(monitor_usage) > MonitorUsedDeflationThreshold; 1110 } 1111 1112 size_t ObjectSynchronizer::in_use_list_ceiling() { 1113 return _in_use_list_ceiling; 1114 } 1115 1116 void ObjectSynchronizer::dec_in_use_list_ceiling() { 1117 Atomic::sub(&_in_use_list_ceiling, AvgMonitorsPerThreadEstimate); 1118 } 1119 1120 void ObjectSynchronizer::inc_in_use_list_ceiling() { 1121 Atomic::add(&_in_use_list_ceiling, AvgMonitorsPerThreadEstimate); 1122 } 1123 1124 void ObjectSynchronizer::set_in_use_list_ceiling(size_t new_value) { 1125 _in_use_list_ceiling = new_value; 1126 } 1127 1128 bool ObjectSynchronizer::is_async_deflation_needed() { 1129 if (is_async_deflation_requested()) { 1130 // Async deflation request. 1131 return true; 1132 } 1133 if (AsyncDeflationInterval > 0 && 1134 time_since_last_async_deflation_ms() > AsyncDeflationInterval && 1135 monitors_used_above_threshold(&_in_use_list)) { 1136 // It's been longer than our specified deflate interval and there 1137 // are too many monitors in use. We don't deflate more frequently 1138 // than AsyncDeflationInterval (unless is_async_deflation_requested) 1139 // in order to not swamp the MonitorDeflationThread. 1140 return true; 1141 } 1142 return false; 1143 } 1144 1145 bool ObjectSynchronizer::request_deflate_idle_monitors() { 1146 JavaThread* current = JavaThread::current(); 1147 bool ret_code = false; 1148 1149 jlong last_time = last_async_deflation_time_ns(); 1150 set_is_async_deflation_requested(true); 1151 { 1152 MonitorLocker ml(MonitorDeflation_lock, Mutex::_no_safepoint_check_flag); 1153 ml.notify_all(); 1154 } 1155 const int N_CHECKS = 5; 1156 for (int i = 0; i < N_CHECKS; i++) { // sleep for at most 5 seconds 1157 if (last_async_deflation_time_ns() > last_time) { 1158 log_info(monitorinflation)("Async Deflation happened after %d check(s).", i); 1159 ret_code = true; 1160 break; 1161 } 1162 { 1163 // JavaThread has to honor the blocking protocol. 1164 ThreadBlockInVM tbivm(current); 1165 os::naked_short_sleep(999); // sleep for almost 1 second 1166 } 1167 } 1168 if (!ret_code) { 1169 log_info(monitorinflation)("Async Deflation DID NOT happen after %d checks.", N_CHECKS); 1170 } 1171 1172 return ret_code; 1173 } 1174 1175 jlong ObjectSynchronizer::time_since_last_async_deflation_ms() { 1176 return (os::javaTimeNanos() - last_async_deflation_time_ns()) / (NANOUNITS / MILLIUNITS); 1177 } 1178 1179 static void post_monitor_inflate_event(EventJavaMonitorInflate* event, 1180 const oop obj, 1181 ObjectSynchronizer::InflateCause cause) { 1182 assert(event != NULL, "invariant"); 1183 assert(event->should_commit(), "invariant"); 1184 event->set_monitorClass(obj->klass()); 1185 event->set_address((uintptr_t)(void*)obj); 1186 event->set_cause((u1)cause); 1187 event->commit(); 1188 } 1189 1190 // Fast path code shared by multiple functions 1191 void ObjectSynchronizer::inflate_helper(oop obj) { 1192 markWord mark = obj->mark(); 1193 if (mark.has_monitor()) { 1194 ObjectMonitor* monitor = mark.monitor(); 1195 markWord dmw = monitor->header(); 1196 assert(dmw.is_neutral(), "sanity check: header=" INTPTR_FORMAT, dmw.value()); 1197 return; 1198 } 1199 (void)inflate(Thread::current(), obj, inflate_cause_vm_internal); 1200 } 1201 1202 ObjectMonitor* ObjectSynchronizer::inflate(Thread* current, oop object, 1203 const InflateCause cause) { 1204 EventJavaMonitorInflate event; 1205 1206 for (;;) { 1207 const markWord mark = object->mark(); 1208 assert(!mark.has_bias_pattern(), "invariant"); 1209 1210 // The mark can be in one of the following states: 1211 // * Inflated - just return 1212 // * Stack-locked - coerce it to inflated 1213 // * INFLATING - busy wait for conversion to complete 1214 // * Neutral - aggressively inflate the object. 1215 // * BIASED - Illegal. We should never see this 1216 1217 // CASE: inflated 1218 if (mark.has_monitor()) { 1219 ObjectMonitor* inf = mark.monitor(); 1220 markWord dmw = inf->header(); 1221 assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value()); 1222 return inf; 1223 } 1224 1225 // CASE: inflation in progress - inflating over a stack-lock. 1226 // Some other thread is converting from stack-locked to inflated. 1227 // Only that thread can complete inflation -- other threads must wait. 1228 // The INFLATING value is transient. 1229 // Currently, we spin/yield/park and poll the markword, waiting for inflation to finish. 1230 // We could always eliminate polling by parking the thread on some auxiliary list. 1231 if (mark == markWord::INFLATING()) { 1232 read_stable_mark(object); 1233 continue; 1234 } 1235 1236 // CASE: stack-locked 1237 // Could be stack-locked either by this thread or by some other thread. 1238 // 1239 // Note that we allocate the ObjectMonitor speculatively, _before_ attempting 1240 // to install INFLATING into the mark word. We originally installed INFLATING, 1241 // allocated the ObjectMonitor, and then finally STed the address of the 1242 // ObjectMonitor into the mark. This was correct, but artificially lengthened 1243 // the interval in which INFLATING appeared in the mark, thus increasing 1244 // the odds of inflation contention. 1245 1246 LogStreamHandle(Trace, monitorinflation) lsh; 1247 1248 if (mark.has_locker()) { 1249 ObjectMonitor* m = new ObjectMonitor(object); 1250 // Optimistically prepare the ObjectMonitor - anticipate successful CAS 1251 // We do this before the CAS in order to minimize the length of time 1252 // in which INFLATING appears in the mark. 1253 1254 markWord cmp = object->cas_set_mark(markWord::INFLATING(), mark); 1255 if (cmp != mark) { 1256 delete m; 1257 continue; // Interference -- just retry 1258 } 1259 1260 // We've successfully installed INFLATING (0) into the mark-word. 1261 // This is the only case where 0 will appear in a mark-word. 1262 // Only the singular thread that successfully swings the mark-word 1263 // to 0 can perform (or more precisely, complete) inflation. 1264 // 1265 // Why do we CAS a 0 into the mark-word instead of just CASing the 1266 // mark-word from the stack-locked value directly to the new inflated state? 1267 // Consider what happens when a thread unlocks a stack-locked object. 1268 // It attempts to use CAS to swing the displaced header value from the 1269 // on-stack BasicLock back into the object header. Recall also that the 1270 // header value (hash code, etc) can reside in (a) the object header, or 1271 // (b) a displaced header associated with the stack-lock, or (c) a displaced 1272 // header in an ObjectMonitor. The inflate() routine must copy the header 1273 // value from the BasicLock on the owner's stack to the ObjectMonitor, all 1274 // the while preserving the hashCode stability invariants. If the owner 1275 // decides to release the lock while the value is 0, the unlock will fail 1276 // and control will eventually pass from slow_exit() to inflate. The owner 1277 // will then spin, waiting for the 0 value to disappear. Put another way, 1278 // the 0 causes the owner to stall if the owner happens to try to 1279 // drop the lock (restoring the header from the BasicLock to the object) 1280 // while inflation is in-progress. This protocol avoids races that might 1281 // would otherwise permit hashCode values to change or "flicker" for an object. 1282 // Critically, while object->mark is 0 mark.displaced_mark_helper() is stable. 1283 // 0 serves as a "BUSY" inflate-in-progress indicator. 1284 1285 1286 // fetch the displaced mark from the owner's stack. 1287 // The owner can't die or unwind past the lock while our INFLATING 1288 // object is in the mark. Furthermore the owner can't complete 1289 // an unlock on the object, either. 1290 markWord dmw = mark.displaced_mark_helper(); 1291 // Catch if the object's header is not neutral (not locked and 1292 // not marked is what we care about here). 1293 assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value()); 1294 1295 // Setup monitor fields to proper values -- prepare the monitor 1296 m->set_header(dmw); 1297 1298 // Optimization: if the mark.locker stack address is associated 1299 // with this thread we could simply set m->_owner = current. 1300 // Note that a thread can inflate an object 1301 // that it has stack-locked -- as might happen in wait() -- directly 1302 // with CAS. That is, we can avoid the xchg-NULL .... ST idiom. 1303 m->set_owner_from(NULL, mark.locker()); 1304 // TODO-FIXME: assert BasicLock->dhw != 0. 1305 1306 // Must preserve store ordering. The monitor state must 1307 // be stable at the time of publishing the monitor address. 1308 guarantee(object->mark() == markWord::INFLATING(), "invariant"); 1309 // Release semantics so that above set_object() is seen first. 1310 object->release_set_mark(markWord::encode(m)); 1311 1312 // Once ObjectMonitor is configured and the object is associated 1313 // with the ObjectMonitor, it is safe to allow async deflation: 1314 _in_use_list.add(m); 1315 1316 // Hopefully the performance counters are allocated on distinct cache lines 1317 // to avoid false sharing on MP systems ... 1318 OM_PERFDATA_OP(Inflations, inc()); 1319 if (log_is_enabled(Trace, monitorinflation)) { 1320 ResourceMark rm(current); 1321 lsh.print_cr("inflate(has_locker): object=" INTPTR_FORMAT ", mark=" 1322 INTPTR_FORMAT ", type='%s'", p2i(object), 1323 object->mark().value(), object->klass()->external_name()); 1324 } 1325 if (event.should_commit()) { 1326 post_monitor_inflate_event(&event, object, cause); 1327 } 1328 return m; 1329 } 1330 1331 // CASE: neutral 1332 // TODO-FIXME: for entry we currently inflate and then try to CAS _owner. 1333 // If we know we're inflating for entry it's better to inflate by swinging a 1334 // pre-locked ObjectMonitor pointer into the object header. A successful 1335 // CAS inflates the object *and* confers ownership to the inflating thread. 1336 // In the current implementation we use a 2-step mechanism where we CAS() 1337 // to inflate and then CAS() again to try to swing _owner from NULL to current. 1338 // An inflateTry() method that we could call from enter() would be useful. 1339 1340 // Catch if the object's header is not neutral (not locked and 1341 // not marked is what we care about here). 1342 assert(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT, mark.value()); 1343 ObjectMonitor* m = new ObjectMonitor(object); 1344 // prepare m for installation - set monitor to initial state 1345 m->set_header(mark); 1346 1347 if (object->cas_set_mark(markWord::encode(m), mark) != mark) { 1348 delete m; 1349 m = NULL; 1350 continue; 1351 // interference - the markword changed - just retry. 1352 // The state-transitions are one-way, so there's no chance of 1353 // live-lock -- "Inflated" is an absorbing state. 1354 } 1355 1356 // Once the ObjectMonitor is configured and object is associated 1357 // with the ObjectMonitor, it is safe to allow async deflation: 1358 _in_use_list.add(m); 1359 1360 // Hopefully the performance counters are allocated on distinct 1361 // cache lines to avoid false sharing on MP systems ... 1362 OM_PERFDATA_OP(Inflations, inc()); 1363 if (log_is_enabled(Trace, monitorinflation)) { 1364 ResourceMark rm(current); 1365 lsh.print_cr("inflate(neutral): object=" INTPTR_FORMAT ", mark=" 1366 INTPTR_FORMAT ", type='%s'", p2i(object), 1367 object->mark().value(), object->klass()->external_name()); 1368 } 1369 if (event.should_commit()) { 1370 post_monitor_inflate_event(&event, object, cause); 1371 } 1372 return m; 1373 } 1374 } 1375 1376 void ObjectSynchronizer::chk_for_block_req(JavaThread* current, const char* op_name, 1377 const char* cnt_name, size_t cnt, 1378 LogStream* ls, elapsedTimer* timer_p) { 1379 if (!SafepointMechanism::should_process(current)) { 1380 return; 1381 } 1382 1383 // A safepoint/handshake has started. 1384 if (ls != NULL) { 1385 timer_p->stop(); 1386 ls->print_cr("pausing %s: %s=" SIZE_FORMAT ", in_use_list stats: ceiling=" 1387 SIZE_FORMAT ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT, 1388 op_name, cnt_name, cnt, in_use_list_ceiling(), 1389 _in_use_list.count(), _in_use_list.max()); 1390 } 1391 1392 { 1393 // Honor block request. 1394 ThreadBlockInVM tbivm(current); 1395 } 1396 1397 if (ls != NULL) { 1398 ls->print_cr("resuming %s: in_use_list stats: ceiling=" SIZE_FORMAT 1399 ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT, op_name, 1400 in_use_list_ceiling(), _in_use_list.count(), _in_use_list.max()); 1401 timer_p->start(); 1402 } 1403 } 1404 1405 // Walk the in-use list and deflate (at most MonitorDeflationMax) idle 1406 // ObjectMonitors. Returns the number of deflated ObjectMonitors. 1407 size_t ObjectSynchronizer::deflate_monitor_list(Thread* current, LogStream* ls, 1408 elapsedTimer* timer_p) { 1409 MonitorList::Iterator iter = _in_use_list.iterator(); 1410 size_t deflated_count = 0; 1411 1412 while (iter.has_next()) { 1413 if (deflated_count >= (size_t)MonitorDeflationMax) { 1414 break; 1415 } 1416 ObjectMonitor* mid = iter.next(); 1417 if (mid->deflate_monitor()) { 1418 deflated_count++; 1419 } 1420 1421 if (current->is_Java_thread()) { 1422 // A JavaThread must check for a safepoint/handshake and honor it. 1423 chk_for_block_req(current->as_Java_thread(), "deflation", "deflated_count", 1424 deflated_count, ls, timer_p); 1425 } 1426 } 1427 1428 return deflated_count; 1429 } 1430 1431 class HandshakeForDeflation : public HandshakeClosure { 1432 public: 1433 HandshakeForDeflation() : HandshakeClosure("HandshakeForDeflation") {} 1434 1435 void do_thread(Thread* thread) { 1436 log_trace(monitorinflation)("HandshakeForDeflation::do_thread: thread=" 1437 INTPTR_FORMAT, p2i(thread)); 1438 } 1439 }; 1440 1441 // This function is called by the MonitorDeflationThread to deflate 1442 // ObjectMonitors. It is also called via do_final_audit_and_print_stats() 1443 // by the VMThread. 1444 size_t ObjectSynchronizer::deflate_idle_monitors() { 1445 Thread* current = Thread::current(); 1446 if (current->is_Java_thread()) { 1447 // The async deflation request has been processed. 1448 _last_async_deflation_time_ns = os::javaTimeNanos(); 1449 set_is_async_deflation_requested(false); 1450 } 1451 1452 LogStreamHandle(Debug, monitorinflation) lsh_debug; 1453 LogStreamHandle(Info, monitorinflation) lsh_info; 1454 LogStream* ls = NULL; 1455 if (log_is_enabled(Debug, monitorinflation)) { 1456 ls = &lsh_debug; 1457 } else if (log_is_enabled(Info, monitorinflation)) { 1458 ls = &lsh_info; 1459 } 1460 1461 elapsedTimer timer; 1462 if (ls != NULL) { 1463 ls->print_cr("begin deflating: in_use_list stats: ceiling=" SIZE_FORMAT ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT, 1464 in_use_list_ceiling(), _in_use_list.count(), _in_use_list.max()); 1465 timer.start(); 1466 } 1467 1468 // Deflate some idle ObjectMonitors. 1469 size_t deflated_count = deflate_monitor_list(current, ls, &timer); 1470 if (deflated_count > 0 || is_final_audit()) { 1471 // There are ObjectMonitors that have been deflated or this is the 1472 // final audit and all the remaining ObjectMonitors have been 1473 // deflated, BUT the MonitorDeflationThread blocked for the final 1474 // safepoint during unlinking. 1475 1476 // Unlink deflated ObjectMonitors from the in-use list. 1477 ResourceMark rm; 1478 GrowableArray<ObjectMonitor*> delete_list((int)deflated_count); 1479 size_t unlinked_count = _in_use_list.unlink_deflated(current, ls, &timer, 1480 &delete_list); 1481 if (current->is_Java_thread()) { 1482 if (ls != NULL) { 1483 timer.stop(); 1484 ls->print_cr("before handshaking: unlinked_count=" SIZE_FORMAT 1485 ", in_use_list stats: ceiling=" SIZE_FORMAT ", count=" 1486 SIZE_FORMAT ", max=" SIZE_FORMAT, 1487 unlinked_count, in_use_list_ceiling(), 1488 _in_use_list.count(), _in_use_list.max()); 1489 } 1490 1491 // A JavaThread needs to handshake in order to safely free the 1492 // ObjectMonitors that were deflated in this cycle. 1493 HandshakeForDeflation hfd_hc; 1494 Handshake::execute(&hfd_hc); 1495 1496 if (ls != NULL) { 1497 ls->print_cr("after handshaking: in_use_list stats: ceiling=" 1498 SIZE_FORMAT ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT, 1499 in_use_list_ceiling(), _in_use_list.count(), _in_use_list.max()); 1500 timer.start(); 1501 } 1502 } 1503 1504 // After the handshake, safely free the ObjectMonitors that were 1505 // deflated in this cycle. 1506 size_t deleted_count = 0; 1507 for (ObjectMonitor* monitor: delete_list) { 1508 delete monitor; 1509 deleted_count++; 1510 1511 if (current->is_Java_thread()) { 1512 // A JavaThread must check for a safepoint/handshake and honor it. 1513 chk_for_block_req(current->as_Java_thread(), "deletion", "deleted_count", 1514 deleted_count, ls, &timer); 1515 } 1516 } 1517 } 1518 1519 if (ls != NULL) { 1520 timer.stop(); 1521 if (deflated_count != 0 || log_is_enabled(Debug, monitorinflation)) { 1522 ls->print_cr("deflated " SIZE_FORMAT " monitors in %3.7f secs", 1523 deflated_count, timer.seconds()); 1524 } 1525 ls->print_cr("end deflating: in_use_list stats: ceiling=" SIZE_FORMAT ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT, 1526 in_use_list_ceiling(), _in_use_list.count(), _in_use_list.max()); 1527 } 1528 1529 OM_PERFDATA_OP(MonExtant, set_value(_in_use_list.count())); 1530 OM_PERFDATA_OP(Deflations, inc(deflated_count)); 1531 1532 GVars.stw_random = os::random(); 1533 1534 if (deflated_count != 0) { 1535 _no_progress_cnt = 0; 1536 } else { 1537 _no_progress_cnt++; 1538 } 1539 1540 return deflated_count; 1541 } 1542 1543 // Monitor cleanup on JavaThread::exit 1544 1545 // Iterate through monitor cache and attempt to release thread's monitors 1546 class ReleaseJavaMonitorsClosure: public MonitorClosure { 1547 private: 1548 JavaThread* _thread; 1549 1550 public: 1551 ReleaseJavaMonitorsClosure(JavaThread* thread) : _thread(thread) {} 1552 void do_monitor(ObjectMonitor* mid) { 1553 (void)mid->complete_exit(_thread); 1554 } 1555 }; 1556 1557 // Release all inflated monitors owned by current thread. Lightweight monitors are 1558 // ignored. This is meant to be called during JNI thread detach which assumes 1559 // all remaining monitors are heavyweight. All exceptions are swallowed. 1560 // Scanning the extant monitor list can be time consuming. 1561 // A simple optimization is to add a per-thread flag that indicates a thread 1562 // called jni_monitorenter() during its lifetime. 1563 // 1564 // Instead of NoSafepointVerifier it might be cheaper to 1565 // use an idiom of the form: 1566 // auto int tmp = SafepointSynchronize::_safepoint_counter ; 1567 // <code that must not run at safepoint> 1568 // guarantee (((tmp ^ _safepoint_counter) | (tmp & 1)) == 0) ; 1569 // Since the tests are extremely cheap we could leave them enabled 1570 // for normal product builds. 1571 1572 void ObjectSynchronizer::release_monitors_owned_by_thread(JavaThread* current) { 1573 assert(current == JavaThread::current(), "must be current Java thread"); 1574 NoSafepointVerifier nsv; 1575 ReleaseJavaMonitorsClosure rjmc(current); 1576 ObjectSynchronizer::monitors_iterate(&rjmc, current); 1577 assert(!current->has_pending_exception(), "Should not be possible"); 1578 current->clear_pending_exception(); 1579 } 1580 1581 const char* ObjectSynchronizer::inflate_cause_name(const InflateCause cause) { 1582 switch (cause) { 1583 case inflate_cause_vm_internal: return "VM Internal"; 1584 case inflate_cause_monitor_enter: return "Monitor Enter"; 1585 case inflate_cause_wait: return "Monitor Wait"; 1586 case inflate_cause_notify: return "Monitor Notify"; 1587 case inflate_cause_hash_code: return "Monitor Hash Code"; 1588 case inflate_cause_jni_enter: return "JNI Monitor Enter"; 1589 case inflate_cause_jni_exit: return "JNI Monitor Exit"; 1590 default: 1591 ShouldNotReachHere(); 1592 } 1593 return "Unknown"; 1594 } 1595 1596 //------------------------------------------------------------------------------ 1597 // Debugging code 1598 1599 u_char* ObjectSynchronizer::get_gvars_addr() { 1600 return (u_char*)&GVars; 1601 } 1602 1603 u_char* ObjectSynchronizer::get_gvars_hc_sequence_addr() { 1604 return (u_char*)&GVars.hc_sequence; 1605 } 1606 1607 size_t ObjectSynchronizer::get_gvars_size() { 1608 return sizeof(SharedGlobals); 1609 } 1610 1611 u_char* ObjectSynchronizer::get_gvars_stw_random_addr() { 1612 return (u_char*)&GVars.stw_random; 1613 } 1614 1615 // Do the final audit and print of ObjectMonitor stats; must be done 1616 // by the VMThread at VM exit time. 1617 void ObjectSynchronizer::do_final_audit_and_print_stats() { 1618 assert(Thread::current()->is_VM_thread(), "sanity check"); 1619 1620 if (is_final_audit()) { // Only do the audit once. 1621 return; 1622 } 1623 set_is_final_audit(); 1624 1625 if (log_is_enabled(Info, monitorinflation)) { 1626 // Do a deflation in order to reduce the in-use monitor population 1627 // that is reported by ObjectSynchronizer::log_in_use_monitor_details() 1628 // which is called by ObjectSynchronizer::audit_and_print_stats(). 1629 while (ObjectSynchronizer::deflate_idle_monitors() != 0) { 1630 ; // empty 1631 } 1632 // The other audit_and_print_stats() call is done at the Debug 1633 // level at a safepoint in ObjectSynchronizer::do_safepoint_work(). 1634 ObjectSynchronizer::audit_and_print_stats(true /* on_exit */); 1635 } 1636 } 1637 1638 // This function can be called at a safepoint or it can be called when 1639 // we are trying to exit the VM. When we are trying to exit the VM, the 1640 // list walker functions can run in parallel with the other list 1641 // operations so spin-locking is used for safety. 1642 // 1643 // Calls to this function can be added in various places as a debugging 1644 // aid; pass 'true' for the 'on_exit' parameter to have in-use monitor 1645 // details logged at the Info level and 'false' for the 'on_exit' 1646 // parameter to have in-use monitor details logged at the Trace level. 1647 // 1648 void ObjectSynchronizer::audit_and_print_stats(bool on_exit) { 1649 assert(on_exit || SafepointSynchronize::is_at_safepoint(), "invariant"); 1650 1651 LogStreamHandle(Debug, monitorinflation) lsh_debug; 1652 LogStreamHandle(Info, monitorinflation) lsh_info; 1653 LogStreamHandle(Trace, monitorinflation) lsh_trace; 1654 LogStream* ls = NULL; 1655 if (log_is_enabled(Trace, monitorinflation)) { 1656 ls = &lsh_trace; 1657 } else if (log_is_enabled(Debug, monitorinflation)) { 1658 ls = &lsh_debug; 1659 } else if (log_is_enabled(Info, monitorinflation)) { 1660 ls = &lsh_info; 1661 } 1662 assert(ls != NULL, "sanity check"); 1663 1664 int error_cnt = 0; 1665 1666 ls->print_cr("Checking in_use_list:"); 1667 chk_in_use_list(ls, &error_cnt); 1668 1669 if (error_cnt == 0) { 1670 ls->print_cr("No errors found in in_use_list checks."); 1671 } else { 1672 log_error(monitorinflation)("found in_use_list errors: error_cnt=%d", error_cnt); 1673 } 1674 1675 if ((on_exit && log_is_enabled(Info, monitorinflation)) || 1676 (!on_exit && log_is_enabled(Trace, monitorinflation))) { 1677 // When exiting this log output is at the Info level. When called 1678 // at a safepoint, this log output is at the Trace level since 1679 // there can be a lot of it. 1680 log_in_use_monitor_details(ls); 1681 } 1682 1683 ls->flush(); 1684 1685 guarantee(error_cnt == 0, "ERROR: found monitor list errors: error_cnt=%d", error_cnt); 1686 } 1687 1688 // Check the in_use_list; log the results of the checks. 1689 void ObjectSynchronizer::chk_in_use_list(outputStream* out, int *error_cnt_p) { 1690 size_t l_in_use_count = _in_use_list.count(); 1691 size_t l_in_use_max = _in_use_list.max(); 1692 out->print_cr("count=" SIZE_FORMAT ", max=" SIZE_FORMAT, l_in_use_count, 1693 l_in_use_max); 1694 1695 size_t ck_in_use_count = 0; 1696 MonitorList::Iterator iter = _in_use_list.iterator(); 1697 while (iter.has_next()) { 1698 ObjectMonitor* mid = iter.next(); 1699 chk_in_use_entry(mid, out, error_cnt_p); 1700 ck_in_use_count++; 1701 } 1702 1703 if (l_in_use_count == ck_in_use_count) { 1704 out->print_cr("in_use_count=" SIZE_FORMAT " equals ck_in_use_count=" 1705 SIZE_FORMAT, l_in_use_count, ck_in_use_count); 1706 } else { 1707 out->print_cr("WARNING: in_use_count=" SIZE_FORMAT " is not equal to " 1708 "ck_in_use_count=" SIZE_FORMAT, l_in_use_count, 1709 ck_in_use_count); 1710 } 1711 1712 size_t ck_in_use_max = _in_use_list.max(); 1713 if (l_in_use_max == ck_in_use_max) { 1714 out->print_cr("in_use_max=" SIZE_FORMAT " equals ck_in_use_max=" 1715 SIZE_FORMAT, l_in_use_max, ck_in_use_max); 1716 } else { 1717 out->print_cr("WARNING: in_use_max=" SIZE_FORMAT " is not equal to " 1718 "ck_in_use_max=" SIZE_FORMAT, l_in_use_max, ck_in_use_max); 1719 } 1720 } 1721 1722 // Check an in-use monitor entry; log any errors. 1723 void ObjectSynchronizer::chk_in_use_entry(ObjectMonitor* n, outputStream* out, 1724 int* error_cnt_p) { 1725 if (n->owner_is_DEFLATER_MARKER()) { 1726 // This should not happen, but if it does, it is not fatal. 1727 out->print_cr("WARNING: monitor=" INTPTR_FORMAT ": in-use monitor is " 1728 "deflated.", p2i(n)); 1729 return; 1730 } 1731 if (n->header().value() == 0) { 1732 out->print_cr("ERROR: monitor=" INTPTR_FORMAT ": in-use monitor must " 1733 "have non-NULL _header field.", p2i(n)); 1734 *error_cnt_p = *error_cnt_p + 1; 1735 } 1736 const oop obj = n->object_peek(); 1737 if (obj != NULL) { 1738 const markWord mark = obj->mark(); 1739 if (!mark.has_monitor()) { 1740 out->print_cr("ERROR: monitor=" INTPTR_FORMAT ": in-use monitor's " 1741 "object does not think it has a monitor: obj=" 1742 INTPTR_FORMAT ", mark=" INTPTR_FORMAT, p2i(n), 1743 p2i(obj), mark.value()); 1744 *error_cnt_p = *error_cnt_p + 1; 1745 } 1746 ObjectMonitor* const obj_mon = mark.monitor(); 1747 if (n != obj_mon) { 1748 out->print_cr("ERROR: monitor=" INTPTR_FORMAT ": in-use monitor's " 1749 "object does not refer to the same monitor: obj=" 1750 INTPTR_FORMAT ", mark=" INTPTR_FORMAT ", obj_mon=" 1751 INTPTR_FORMAT, p2i(n), p2i(obj), mark.value(), p2i(obj_mon)); 1752 *error_cnt_p = *error_cnt_p + 1; 1753 } 1754 } 1755 } 1756 1757 // Log details about ObjectMonitors on the in_use_list. The 'BHL' 1758 // flags indicate why the entry is in-use, 'object' and 'object type' 1759 // indicate the associated object and its type. 1760 void ObjectSynchronizer::log_in_use_monitor_details(outputStream* out) { 1761 stringStream ss; 1762 if (_in_use_list.count() > 0) { 1763 out->print_cr("In-use monitor info:"); 1764 out->print_cr("(B -> is_busy, H -> has hash code, L -> lock status)"); 1765 out->print_cr("%18s %s %18s %18s", 1766 "monitor", "BHL", "object", "object type"); 1767 out->print_cr("================== === ================== =================="); 1768 MonitorList::Iterator iter = _in_use_list.iterator(); 1769 while (iter.has_next()) { 1770 ObjectMonitor* mid = iter.next(); 1771 const oop obj = mid->object_peek(); 1772 const markWord mark = mid->header(); 1773 ResourceMark rm; 1774 out->print(INTPTR_FORMAT " %d%d%d " INTPTR_FORMAT " %s", p2i(mid), 1775 mid->is_busy(), mark.hash() != 0, mid->owner() != NULL, 1776 p2i(obj), obj == NULL ? "" : obj->klass()->external_name()); 1777 if (mid->is_busy()) { 1778 out->print(" (%s)", mid->is_busy_to_string(&ss)); 1779 ss.reset(); 1780 } 1781 out->cr(); 1782 } 1783 } 1784 1785 out->flush(); 1786 }