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 // Start the timer for deflations, so it does not trigger immediately.
218 _last_async_deflation_time_ns = os::javaTimeNanos();
219 }
220
221 MonitorList ObjectSynchronizer::_in_use_list;
222 // monitors_used_above_threshold() policy is as follows:
223 //
224 // The ratio of the current _in_use_list count to the ceiling is used
225 // to determine if we are above MonitorUsedDeflationThreshold and need
226 // to do an async monitor deflation cycle. The ceiling is increased by
227 // AvgMonitorsPerThreadEstimate when a thread is added to the system
228 // and is decreased by AvgMonitorsPerThreadEstimate when a thread is
229 // removed from the system.
230 //
231 // Note: If the _in_use_list max exceeds the ceiling, then
232 // monitors_used_above_threshold() will use the in_use_list max instead
233 // of the thread count derived ceiling because we have used more
234 // ObjectMonitors than the estimated average.
235 //
236 // Note: If deflate_idle_monitors() has NoAsyncDeflationProgressMax
237 // no-progress async monitor deflation cycles in a row, then the ceiling
238 // is adjusted upwards by monitors_used_above_threshold().
239 //
240 // Start the ceiling with the estimate for one thread in initialize()
241 // which is called after cmd line options are processed.
242 static size_t _in_use_list_ceiling = 0;
243 bool volatile ObjectSynchronizer::_is_async_deflation_requested = false;
244 bool volatile ObjectSynchronizer::_is_final_audit = false;
245 jlong ObjectSynchronizer::_last_async_deflation_time_ns = 0;
246 static uintx _no_progress_cnt = 0;
247 static bool _no_progress_skip_increment = false;
248
249 // =====================> Quick functions
250
251 // The quick_* forms are special fast-path variants used to improve
252 // performance. In the simplest case, a "quick_*" implementation could
253 // simply return false, in which case the caller will perform the necessary
254 // state transitions and call the slow-path form.
255 // The fast-path is designed to handle frequently arising cases in an efficient
256 // manner and is just a degenerate "optimistic" variant of the slow-path.
257 // returns true -- to indicate the call was satisfied.
258 // returns false -- to indicate the call needs the services of the slow-path.
259 // A no-loitering ordinance is in effect for code in the quick_* family
260 // operators: safepoints or indefinite blocking (blocking that might span a
261 // safepoint) are forbidden. Generally the thread_state() is _in_Java upon
262 // entry.
263 //
264 // Consider: An interesting optimization is to have the JIT recognize the
265 // following common idiom:
266 // synchronized (someobj) { .... ; notify(); }
267 // That is, we find a notify() or notifyAll() call that immediately precedes
268 // the monitorexit operation. In that case the JIT could fuse the operations
269 // into a single notifyAndExit() runtime primitive.
270
271 bool ObjectSynchronizer::quick_notify(oopDesc* obj, JavaThread* current, bool all) {
272 assert(current->thread_state() == _thread_in_Java, "invariant");
273 NoSafepointVerifier nsv;
274 if (obj == NULL) return false; // slow-path for invalid obj
275 const markWord mark = obj->mark();
276
277 if (mark.has_locker() && current->is_lock_owned((address)mark.locker())) { 278 // Degenerate notify 279 // stack-locked by caller so by definition the implied waitset is empty. 280 return true;
281 }
282
283 if (mark.has_monitor()) {
284 ObjectMonitor* const mon = mark.monitor();
285 assert(mon->object() == oop(obj), "invariant");
286 if (mon->owner() != current) return false; // slow-path for IMS exception
287
288 if (mon->first_waiter() != NULL) {
289 // We have one or more waiters. Since this is an inflated monitor
290 // that we own, we can transfer one or more threads from the waitset
291 // to the entrylist here and now, avoiding the slow-path.
292 if (all) {
293 DTRACE_MONITOR_PROBE(notifyAll, mon, obj, current);
294 } else {
295 DTRACE_MONITOR_PROBE(notify, mon, obj, current);
296 }
297 int free_count = 0;
298 do {
299 mon->INotify(current);
300 ++free_count;
301 } while (mon->first_waiter() != NULL && all);
302 OM_PERFDATA_OP(Notifications, inc(free_count));
303 }
304 return true;
305 }
306
307 // biased locking and any other IMS exception states take the slow-path
308 return false;
309 }
310
311
312 // The LockNode emitted directly at the synchronization site would have
313 // been too big if it were to have included support for the cases of inflated
314 // recursive enter and exit, so they go here instead.
315 // Note that we can't safely call AsyncPrintJavaStack() from within
316 // quick_enter() as our thread state remains _in_Java.
317
318 bool ObjectSynchronizer::quick_enter(oop obj, JavaThread* current,
319 BasicLock * lock) {
320 assert(current->thread_state() == _thread_in_Java, "invariant");
321 NoSafepointVerifier nsv;
322 if (obj == NULL) return false; // Need to throw NPE
323
324 if (obj->klass()->is_value_based()) {
325 return false;
326 }
327
328 const markWord mark = obj->mark();
329
330 if (mark.has_monitor()) {
331 ObjectMonitor* const m = mark.monitor();
332 // An async deflation or GC can race us before we manage to make
333 // the ObjectMonitor busy by setting the owner below. If we detect
334 // that race we just bail out to the slow-path here.
335 if (m->object_peek() == NULL) {
336 return false;
337 }
338 JavaThread* const owner = (JavaThread*) m->owner_raw();
339
340 // Lock contention and Transactional Lock Elision (TLE) diagnostics
341 // and observability
342 // Case: light contention possibly amenable to TLE
343 // Case: TLE inimical operations such as nested/recursive synchronization
344
345 if (owner == current) {
346 m->_recursions++;
347 return true;
348 }
349
350 // This Java Monitor is inflated so obj's header will never be 351 // displaced to this thread's BasicLock. Make the displaced header 352 // non-NULL so this BasicLock is not seen as recursive nor as 353 // being locked. We do this unconditionally so that this thread's 354 // BasicLock cannot be mis-interpreted by any stack walkers. For 355 // performance reasons, stack walkers generally first check for 356 // Biased Locking in the object's header, the second check is for 357 // stack-locking in the object's header, the third check is for 358 // recursive stack-locking in the displaced header in the BasicLock, 359 // and last are the inflated Java Monitor (ObjectMonitor) checks. 360 lock->set_displaced_header(markWord::unused_mark());
361
362 if (owner == NULL && m->try_set_owner_from(NULL, current) == NULL) {
363 assert(m->_recursions == 0, "invariant");
364 return true;
365 }
366 }
367
368 // Note that we could inflate in quick_enter.
369 // This is likely a useful optimization
370 // Critically, in quick_enter() we must not:
371 // -- perform bias revocation, or
372 // -- block indefinitely, or
373 // -- reach a safepoint
374
375 return false; // revert to slow-path
376 }
377
378 // Handle notifications when synchronizing on value based classes
379 void ObjectSynchronizer::handle_sync_on_value_based_class(Handle obj, JavaThread* current) {
380 frame last_frame = current->last_frame();
381 bool bcp_was_adjusted = false;
382 // Don't decrement bcp if it points to the frame's first instruction. This happens when
383 // handle_sync_on_value_based_class() is called because of a synchronized method. There
384 // is no actual monitorenter instruction in the byte code in this case.
385 if (last_frame.is_interpreted_frame() &&
386 (last_frame.interpreter_frame_method()->code_base() < last_frame.interpreter_frame_bcp())) {
387 // adjust bcp to point back to monitorenter so that we print the correct line numbers
388 last_frame.interpreter_frame_set_bcp(last_frame.interpreter_frame_bcp() - 1);
389 bcp_was_adjusted = true;
390 }
391
392 if (DiagnoseSyncOnValueBasedClasses == FATAL_EXIT) {
393 ResourceMark rm(current);
394 stringStream ss;
395 current->print_stack_on(&ss);
396 char* base = (char*)strstr(ss.base(), "at");
397 char* newline = (char*)strchr(ss.base(), '\n');
398 if (newline != NULL) {
399 *newline = '\0';
400 }
401 fatal("Synchronizing on object " INTPTR_FORMAT " of klass %s %s", p2i(obj()), obj->klass()->external_name(), base);
402 } else {
403 assert(DiagnoseSyncOnValueBasedClasses == LOG_WARNING, "invalid value for DiagnoseSyncOnValueBasedClasses");
404 ResourceMark rm(current);
405 Log(valuebasedclasses) vblog;
406
407 vblog.info("Synchronizing on object " INTPTR_FORMAT " of klass %s", p2i(obj()), obj->klass()->external_name());
408 if (current->has_last_Java_frame()) {
409 LogStream info_stream(vblog.info());
410 current->print_stack_on(&info_stream);
411 } else {
412 vblog.info("Cannot find the last Java frame");
413 }
414
415 EventSyncOnValueBasedClass event;
416 if (event.should_commit()) {
417 event.set_valueBasedClass(obj->klass());
418 event.commit();
419 }
420 }
421
422 if (bcp_was_adjusted) {
423 last_frame.interpreter_frame_set_bcp(last_frame.interpreter_frame_bcp() + 1);
424 }
425 }
426
427 // -----------------------------------------------------------------------------
428 // Monitor Enter/Exit
429 // The interpreter and compiler assembly code tries to lock using the fast path
430 // of this algorithm. Make sure to update that code if the following function is
431 // changed. The implementation is extremely sensitive to race condition. Be careful.
432
433 void ObjectSynchronizer::enter(Handle obj, BasicLock* lock, JavaThread* current) {
434 if (obj->klass()->is_value_based()) {
435 handle_sync_on_value_based_class(obj, current);
436 }
437
438 if (UseBiasedLocking) { 439 BiasedLocking::revoke(current, obj); 440 }
441
442 markWord mark = obj->mark(); 443 assert(!mark.has_bias_pattern(), "should not see bias pattern here");
444
445 if (mark.is_neutral()) { 446 // Anticipate successful CAS -- the ST of the displaced mark must 447 // be visible <= the ST performed by the CAS. 448 lock->set_displaced_header(mark); 449 if (mark == obj()->cas_set_mark(markWord::from_pointer(lock), mark)) { 450 return;
451 }
452 // Fall through to inflate() ... 453 } else if (mark.has_locker() && 454 current->is_lock_owned((address)mark.locker())) { 455 assert(lock != mark.locker(), "must not re-lock the same lock"); 456 assert(lock != (BasicLock*)obj->mark().value(), "don't relock with same BasicLock"); 457 lock->set_displaced_header(markWord::from_pointer(NULL)); 458 return;
459 }
460
461 // The object header will never be displaced to this lock, 462 // so it does not matter what the value is, except that it 463 // must be non-zero to avoid looking like a re-entrant lock, 464 // and must not look locked either. 465 lock->set_displaced_header(markWord::unused_mark());
466 // An async deflation can race after the inflate() call and before
467 // enter() can make the ObjectMonitor busy. enter() returns false if
468 // we have lost the race to async deflation and we simply try again.
469 while (true) {
470 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_monitor_enter);
471 if (monitor->enter(current)) {
472 return;
473 }
474 }
475 }
476
477 void ObjectSynchronizer::exit(oop object, BasicLock* lock, JavaThread* current) {
478 markWord mark = object->mark(); 479 // We cannot check for Biased Locking if we are racing an inflation. 480 assert(mark == markWord::INFLATING() || 481 !mark.has_bias_pattern(), "should not see bias pattern here"); 482 483 markWord dhw = lock->displaced_header(); 484 if (dhw.value() == 0) { 485 // If the displaced header is NULL, then this exit matches up with 486 // a recursive enter. No real work to do here except for diagnostics. 487 #ifndef PRODUCT 488 if (mark != markWord::INFLATING()) { 489 // Only do diagnostics if we are not racing an inflation. Simply 490 // exiting a recursive enter of a Java Monitor that is being 491 // inflated is safe; see the has_monitor() comment below. 492 assert(!mark.is_neutral(), "invariant"); 493 assert(!mark.has_locker() || 494 current->is_lock_owned((address)mark.locker()), "invariant"); 495 if (mark.has_monitor()) { 496 // The BasicLock's displaced_header is marked as a recursive 497 // enter and we have an inflated Java Monitor (ObjectMonitor). 498 // This is a special case where the Java Monitor was inflated 499 // after this thread entered the stack-lock recursively. When a 500 // Java Monitor is inflated, we cannot safely walk the Java 501 // Monitor owner's stack and update the BasicLocks because a 502 // Java Monitor can be asynchronously inflated by a thread that 503 // does not own the Java Monitor. 504 ObjectMonitor* m = mark.monitor(); 505 assert(m->object()->mark() == mark, "invariant"); 506 assert(m->is_entered(current), "invariant");
507 }
508 }
509 #endif
510 return; 511 }
512
513 if (mark == markWord::from_pointer(lock)) { 514 // If the object is stack-locked by the current thread, try to 515 // swing the displaced header from the BasicLock back to the mark. 516 assert(dhw.is_neutral(), "invariant"); 517 if (object->cas_set_mark(dhw, mark) == mark) { 518 return;
519 }
520 }
521
522 // We have to take the slow-path of possible inflation and then exit.
523 // The ObjectMonitor* can't be async deflated until ownership is
524 // dropped inside exit() and the ObjectMonitor* must be !is_busy().
525 ObjectMonitor* monitor = inflate(current, object, inflate_cause_vm_internal);
526 monitor->exit(current);
527 }
528
529 // -----------------------------------------------------------------------------
530 // Class Loader support to workaround deadlocks on the class loader lock objects
531 // Also used by GC
532 // complete_exit()/reenter() are used to wait on a nested lock
533 // i.e. to give up an outer lock completely and then re-enter
534 // Used when holding nested locks - lock acquisition order: lock1 then lock2
535 // 1) complete_exit lock1 - saving recursion count
536 // 2) wait on lock2
537 // 3) when notified on lock2, unlock lock2
538 // 4) reenter lock1 with original recursion count
539 // 5) lock lock2
540 // NOTE: must use heavy weight monitor to handle complete_exit/reenter()
541 intx ObjectSynchronizer::complete_exit(Handle obj, JavaThread* current) {
542 if (UseBiasedLocking) {
543 BiasedLocking::revoke(current, obj);
544 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now");
545 }
546
547 // The ObjectMonitor* can't be async deflated until ownership is
548 // dropped inside exit() and the ObjectMonitor* must be !is_busy().
549 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_vm_internal);
550 intptr_t ret_code = monitor->complete_exit(current);
551 return ret_code;
552 }
553
554 // NOTE: must use heavy weight monitor to handle complete_exit/reenter()
555 void ObjectSynchronizer::reenter(Handle obj, intx recursions, JavaThread* current) {
556 if (UseBiasedLocking) {
557 BiasedLocking::revoke(current, obj);
558 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now");
559 }
560
561 // An async deflation can race after the inflate() call and before
562 // reenter() -> enter() can make the ObjectMonitor busy. reenter() ->
563 // enter() returns false if we have lost the race to async deflation
564 // and we simply try again.
565 while (true) {
566 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_vm_internal);
567 if (monitor->reenter(recursions, current)) {
568 return;
569 }
570 }
571 }
572
573 // -----------------------------------------------------------------------------
574 // JNI locks on java objects
575 // NOTE: must use heavy weight monitor to handle jni monitor enter
576 void ObjectSynchronizer::jni_enter(Handle obj, JavaThread* current) {
577 if (obj->klass()->is_value_based()) {
578 handle_sync_on_value_based_class(obj, current);
579 }
580
581 // the current locking is from JNI instead of Java code
582 if (UseBiasedLocking) {
583 BiasedLocking::revoke(current, obj);
584 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now");
585 }
586 current->set_current_pending_monitor_is_from_java(false);
587 // An async deflation can race after the inflate() call and before
588 // enter() can make the ObjectMonitor busy. enter() returns false if
589 // we have lost the race to async deflation and we simply try again.
590 while (true) {
591 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_jni_enter);
592 if (monitor->enter(current)) {
593 break;
594 }
595 }
596 current->set_current_pending_monitor_is_from_java(true);
597 }
598
599 // NOTE: must use heavy weight monitor to handle jni monitor exit
600 void ObjectSynchronizer::jni_exit(oop obj, TRAPS) {
601 JavaThread* current = THREAD;
602 if (UseBiasedLocking) {
603 Handle h_obj(current, obj);
604 BiasedLocking::revoke(current, h_obj);
605 obj = h_obj();
606 }
607 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now");
608
609 // The ObjectMonitor* can't be async deflated until ownership is
610 // dropped inside exit() and the ObjectMonitor* must be !is_busy().
611 ObjectMonitor* monitor = inflate(current, obj, inflate_cause_jni_exit);
612 // If this thread has locked the object, exit the monitor. We
613 // intentionally do not use CHECK on check_owner because we must exit the
614 // monitor even if an exception was already pending.
615 if (monitor->check_owner(THREAD)) {
616 monitor->exit(current);
617 }
618 }
619
620 // -----------------------------------------------------------------------------
621 // Internal VM locks on java objects
622 // standard constructor, allows locking failures
623 ObjectLocker::ObjectLocker(Handle obj, JavaThread* thread) {
624 _thread = thread;
625 _thread->check_for_valid_safepoint_state();
626 _obj = obj;
627
628 if (_obj() != NULL) {
629 ObjectSynchronizer::enter(_obj, &_lock, _thread);
630 }
631 }
632
633 ObjectLocker::~ObjectLocker() {
634 if (_obj() != NULL) {
635 ObjectSynchronizer::exit(_obj(), &_lock, _thread);
636 }
637 }
638
639
640 // -----------------------------------------------------------------------------
641 // Wait/Notify/NotifyAll
642 // NOTE: must use heavy weight monitor to handle wait()
643 int ObjectSynchronizer::wait(Handle obj, jlong millis, TRAPS) {
644 JavaThread* current = THREAD;
645 if (UseBiasedLocking) {
646 BiasedLocking::revoke(current, obj);
647 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now");
648 }
649 if (millis < 0) {
650 THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative");
651 }
652 // The ObjectMonitor* can't be async deflated because the _waiters
653 // field is incremented before ownership is dropped and decremented
654 // after ownership is regained.
655 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_wait);
656
657 DTRACE_MONITOR_WAIT_PROBE(monitor, obj(), current, millis);
658 monitor->wait(millis, true, THREAD); // Not CHECK as we need following code
659
660 // This dummy call is in place to get around dtrace bug 6254741. Once
661 // that's fixed we can uncomment the following line, remove the call
662 // and change this function back into a "void" func.
663 // DTRACE_MONITOR_PROBE(waited, monitor, obj(), THREAD);
664 int ret_code = dtrace_waited_probe(monitor, obj, THREAD);
665 return ret_code;
666 }
667
668 // No exception are possible in this case as we only use this internally when locking is
669 // correct and we have to wait until notified - so no interrupts or timeouts.
670 void ObjectSynchronizer::wait_uninterruptibly(Handle obj, JavaThread* current) {
671 if (UseBiasedLocking) {
672 BiasedLocking::revoke(current, obj);
673 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now");
674 }
675 // The ObjectMonitor* can't be async deflated because the _waiters
676 // field is incremented before ownership is dropped and decremented
677 // after ownership is regained.
678 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_wait);
679 monitor->wait(0 /* wait-forever */, false /* not interruptible */, current);
680 }
681
682 void ObjectSynchronizer::notify(Handle obj, TRAPS) {
683 JavaThread* current = THREAD;
684 if (UseBiasedLocking) {
685 BiasedLocking::revoke(current, obj);
686 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now");
687 }
688
689 markWord mark = obj->mark();
690 if (mark.has_locker() && current->is_lock_owned((address)mark.locker())) { 691 // Not inflated so there can't be any waiters to notify. 692 return;
693 }
694 // The ObjectMonitor* can't be async deflated until ownership is
695 // dropped by the calling thread.
696 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_notify);
697 monitor->notify(CHECK);
698 }
699
700 // NOTE: see comment of notify()
701 void ObjectSynchronizer::notifyall(Handle obj, TRAPS) {
702 JavaThread* current = THREAD;
703 if (UseBiasedLocking) {
704 BiasedLocking::revoke(current, obj);
705 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now");
706 }
707
708 markWord mark = obj->mark();
709 if (mark.has_locker() && current->is_lock_owned((address)mark.locker())) { 710 // Not inflated so there can't be any waiters to notify. 711 return;
712 }
713 // The ObjectMonitor* can't be async deflated until ownership is
714 // dropped by the calling thread.
715 ObjectMonitor* monitor = inflate(current, obj(), inflate_cause_notify);
716 monitor->notifyAll(CHECK);
717 }
718
719 // -----------------------------------------------------------------------------
720 // Hash Code handling
721
722 struct SharedGlobals {
723 char _pad_prefix[OM_CACHE_LINE_SIZE];
724 // This is a highly shared mostly-read variable.
725 // To avoid false-sharing it needs to be the sole occupant of a cache line.
726 volatile int stw_random;
727 DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(volatile int));
728 // Hot RW variable -- Sequester to avoid false-sharing
729 volatile int hc_sequence;
730 DEFINE_PAD_MINUS_SIZE(2, OM_CACHE_LINE_SIZE, sizeof(volatile int));
731 };
732
733 static SharedGlobals GVars;
734
735 static markWord read_stable_mark(oop obj) {
736 markWord mark = obj->mark();
737 if (!mark.is_being_inflated()) {
738 return mark; // normal fast-path return
739 }
740
741 int its = 0;
742 for (;;) {
743 markWord mark = obj->mark();
744 if (!mark.is_being_inflated()) {
745 return mark; // normal fast-path return
746 }
747
748 // The object is being inflated by some other thread.
749 // The caller of read_stable_mark() must wait for inflation to complete.
750 // Avoid live-lock.
751
752 ++its;
753 if (its > 10000 || !os::is_MP()) {
754 if (its & 1) {
755 os::naked_yield();
756 } else {
757 // Note that the following code attenuates the livelock problem but is not
758 // a complete remedy. A more complete solution would require that the inflating
759 // thread hold the associated inflation lock. The following code simply restricts
760 // the number of spinners to at most one. We'll have N-2 threads blocked
761 // on the inflationlock, 1 thread holding the inflation lock and using
762 // a yield/park strategy, and 1 thread in the midst of inflation.
763 // A more refined approach would be to change the encoding of INFLATING
764 // to allow encapsulation of a native thread pointer. Threads waiting for
765 // inflation to complete would use CAS to push themselves onto a singly linked
766 // list rooted at the markword. Once enqueued, they'd loop, checking a per-thread flag
767 // and calling park(). When inflation was complete the thread that accomplished inflation
768 // would detach the list and set the markword to inflated with a single CAS and
769 // then for each thread on the list, set the flag and unpark() the thread.
770
771 // Index into the lock array based on the current object address.
772 static_assert(is_power_of_2(NINFLATIONLOCKS), "must be");
773 int ix = (cast_from_oop<intptr_t>(obj) >> 5) & (NINFLATIONLOCKS-1);
774 int YieldThenBlock = 0;
775 assert(ix >= 0 && ix < NINFLATIONLOCKS, "invariant");
776 gInflationLocks[ix]->lock();
777 while (obj->mark() == markWord::INFLATING()) {
778 // Beware: naked_yield() is advisory and has almost no effect on some platforms
779 // so we periodically call current->_ParkEvent->park(1).
780 // We use a mixed spin/yield/block mechanism.
781 if ((YieldThenBlock++) >= 16) {
782 Thread::current()->_ParkEvent->park(1);
783 } else {
784 os::naked_yield();
785 }
786 }
787 gInflationLocks[ix]->unlock();
788 }
789 } else {
790 SpinPause(); // SMP-polite spinning
791 }
792 }
793 }
794
795 // hashCode() generation :
796 //
797 // Possibilities:
798 // * MD5Digest of {obj,stw_random}
799 // * CRC32 of {obj,stw_random} or any linear-feedback shift register function.
800 // * A DES- or AES-style SBox[] mechanism
801 // * One of the Phi-based schemes, such as:
802 // 2654435761 = 2^32 * Phi (golden ratio)
803 // HashCodeValue = ((uintptr_t(obj) >> 3) * 2654435761) ^ GVars.stw_random ;
804 // * A variation of Marsaglia's shift-xor RNG scheme.
805 // * (obj ^ stw_random) is appealing, but can result
806 // in undesirable regularity in the hashCode values of adjacent objects
807 // (objects allocated back-to-back, in particular). This could potentially
808 // result in hashtable collisions and reduced hashtable efficiency.
809 // There are simple ways to "diffuse" the middle address bits over the
810 // generated hashCode values:
811
812 static inline intptr_t get_next_hash(Thread* current, oop obj) {
813 intptr_t value = 0;
814 if (hashCode == 0) {
815 // This form uses global Park-Miller RNG.
816 // On MP system we'll have lots of RW access to a global, so the
817 // mechanism induces lots of coherency traffic.
818 value = os::random();
819 } else if (hashCode == 1) {
820 // This variation has the property of being stable (idempotent)
821 // between STW operations. This can be useful in some of the 1-0
822 // synchronization schemes.
823 intptr_t addr_bits = cast_from_oop<intptr_t>(obj) >> 3;
824 value = addr_bits ^ (addr_bits >> 5) ^ GVars.stw_random;
825 } else if (hashCode == 2) {
826 value = 1; // for sensitivity testing
827 } else if (hashCode == 3) {
828 value = ++GVars.hc_sequence;
829 } else if (hashCode == 4) {
830 value = cast_from_oop<intptr_t>(obj);
831 } else {
832 // Marsaglia's xor-shift scheme with thread-specific state
833 // This is probably the best overall implementation -- we'll
834 // likely make this the default in future releases.
835 unsigned t = current->_hashStateX;
836 t ^= (t << 11);
837 current->_hashStateX = current->_hashStateY;
838 current->_hashStateY = current->_hashStateZ;
839 current->_hashStateZ = current->_hashStateW;
840 unsigned v = current->_hashStateW;
841 v = (v ^ (v >> 19)) ^ (t ^ (t >> 8));
842 current->_hashStateW = v;
843 value = v;
844 }
845
846 value &= markWord::hash_mask;
847 if (value == 0) value = 0xBAD;
848 assert(value != markWord::no_hash, "invariant");
849 return value;
850 }
851
852 intptr_t ObjectSynchronizer::FastHashCode(Thread* current, oop obj) {
853 if (UseBiasedLocking) {
854 // NOTE: many places throughout the JVM do not expect a safepoint
855 // to be taken here. However, we only ever bias Java instances and all
856 // of the call sites of identity_hash that might revoke biases have
857 // been checked to make sure they can handle a safepoint. The
858 // added check of the bias pattern is to avoid useless calls to
859 // thread-local storage.
860 if (obj->mark().has_bias_pattern()) {
861 // Handle for oop obj in case of STW safepoint
862 Handle hobj(current, obj);
863 if (SafepointSynchronize::is_at_safepoint()) {
864 BiasedLocking::revoke_at_safepoint(hobj);
865 } else {
866 BiasedLocking::revoke(current->as_Java_thread(), hobj);
867 }
868 obj = hobj();
869 assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now");
870 }
871 }
872
873 while (true) {
874 ObjectMonitor* monitor = NULL;
875 markWord temp, test;
876 intptr_t hash;
877 markWord mark = read_stable_mark(obj);
878
879 // object should remain ineligible for biased locking
880 assert(!mark.has_bias_pattern(), "invariant");
881
882 if (mark.is_neutral()) { // if this is a normal header
883 hash = mark.hash();
884 if (hash != 0) { // if it has a hash, just return it
885 return hash;
886 }
887 hash = get_next_hash(current, obj); // get a new hash
888 temp = mark.copy_set_hash(hash); // merge the hash into header
889 // try to install the hash
890 test = obj->cas_set_mark(temp, mark);
891 if (test == mark) { // if the hash was installed, return it
892 return hash;
893 }
894 // Failed to install the hash. It could be that another thread
895 // installed the hash just before our attempt or inflation has
896 // occurred or... so we fall thru to inflate the monitor for
897 // stability and then install the hash.
898 } else if (mark.has_monitor()) {
899 monitor = mark.monitor();
900 temp = monitor->header();
901 assert(temp.is_neutral(), "invariant: header=" INTPTR_FORMAT, temp.value());
902 hash = temp.hash();
903 if (hash != 0) {
904 // It has a hash.
905
906 // Separate load of dmw/header above from the loads in
907 // is_being_async_deflated().
908
909 // dmw/header and _contentions may get written by different threads.
910 // Make sure to observe them in the same order when having several observers.
911 OrderAccess::loadload_for_IRIW();
912
913 if (monitor->is_being_async_deflated()) {
914 // But we can't safely use the hash if we detect that async
915 // deflation has occurred. So we attempt to restore the
916 // header/dmw to the object's header so that we only retry
917 // once if the deflater thread happens to be slow.
918 monitor->install_displaced_markword_in_object(obj);
919 continue;
920 }
921 return hash;
922 }
923 // Fall thru so we only have one place that installs the hash in
924 // the ObjectMonitor.
925 } else if (current->is_lock_owned((address)mark.locker())) {
926 // This is a stack lock owned by the calling thread so fetch the
927 // displaced markWord from the BasicLock on the stack.
928 temp = mark.displaced_mark_helper();
929 assert(temp.is_neutral(), "invariant: header=" INTPTR_FORMAT, temp.value());
930 hash = temp.hash();
931 if (hash != 0) { // if it has a hash, just return it
932 return hash;
933 }
934 // WARNING:
935 // The displaced header in the BasicLock on a thread's stack
936 // is strictly immutable. It CANNOT be changed in ANY cases.
937 // So we have to inflate the stack lock into an ObjectMonitor
938 // even if the current thread owns the lock. The BasicLock on
939 // a thread's stack can be asynchronously read by other threads
940 // during an inflate() call so any change to that stack memory
941 // may not propagate to other threads correctly.
942 }
943
944 // Inflate the monitor to set the hash.
945
946 // An async deflation can race after the inflate() call and before we
947 // can update the ObjectMonitor's header with the hash value below.
948 monitor = inflate(current, obj, inflate_cause_hash_code);
949 // Load ObjectMonitor's header/dmw field and see if it has a hash.
950 mark = monitor->header();
951 assert(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT, mark.value());
952 hash = mark.hash();
953 if (hash == 0) { // if it does not have a hash
954 hash = get_next_hash(current, obj); // get a new hash
955 temp = mark.copy_set_hash(hash) ; // merge the hash into header
956 assert(temp.is_neutral(), "invariant: header=" INTPTR_FORMAT, temp.value());
957 uintptr_t v = Atomic::cmpxchg((volatile uintptr_t*)monitor->header_addr(), mark.value(), temp.value());
958 test = markWord(v);
959 if (test != mark) {
960 // The attempt to update the ObjectMonitor's header/dmw field
961 // did not work. This can happen if another thread managed to
962 // merge in the hash just before our cmpxchg().
963 // If we add any new usages of the header/dmw field, this code
964 // will need to be updated.
965 hash = test.hash();
966 assert(test.is_neutral(), "invariant: header=" INTPTR_FORMAT, test.value());
967 assert(hash != 0, "should only have lost the race to a thread that set a non-zero hash");
968 }
969 if (monitor->is_being_async_deflated()) {
970 // If we detect that async deflation has occurred, then we
971 // attempt to restore the header/dmw to the object's header
972 // so that we only retry once if the deflater thread happens
973 // to be slow.
974 monitor->install_displaced_markword_in_object(obj);
975 continue;
976 }
977 }
978 // We finally get the hash.
979 return hash;
980 }
981 }
982
983 // Deprecated -- use FastHashCode() instead.
984
985 intptr_t ObjectSynchronizer::identity_hash_value_for(Handle obj) {
986 return FastHashCode(Thread::current(), obj());
987 }
988
989
990 bool ObjectSynchronizer::current_thread_holds_lock(JavaThread* current,
991 Handle h_obj) {
992 if (UseBiasedLocking) {
993 BiasedLocking::revoke(current, h_obj);
994 assert(!h_obj->mark().has_bias_pattern(), "biases should be revoked by now");
995 }
996
997 assert(current == JavaThread::current(), "Can only be called on current thread");
998 oop obj = h_obj();
999
1000 markWord mark = read_stable_mark(obj);
1001
1002 // Uncontended case, header points to stack1003 if (mark.has_locker()) {
1004 return current->is_lock_owned((address)mark.locker());
1005 }
1006 // Contended case, header points to ObjectMonitor (tagged pointer)
1007 if (mark.has_monitor()) {
1008 // The first stage of async deflation does not affect any field
1009 // used by this comparison so the ObjectMonitor* is usable here.
1010 ObjectMonitor* monitor = mark.monitor();
1011 return monitor->is_entered(current) != 0;
1012 }
1013 // Unlocked case, header in place
1014 assert(mark.is_neutral(), "sanity check");
1015 return false;
1016 }
1017
1018 // FIXME: jvmti should call this
1019 JavaThread* ObjectSynchronizer::get_lock_owner(ThreadsList * t_list, Handle h_obj) {
1020 if (UseBiasedLocking) {
1021 if (SafepointSynchronize::is_at_safepoint()) {
1022 BiasedLocking::revoke_at_safepoint(h_obj);
1023 } else {
1024 BiasedLocking::revoke(JavaThread::current(), h_obj);
1025 }
1026 assert(!h_obj->mark().has_bias_pattern(), "biases should be revoked by now");
1027 }
1028
1029 oop obj = h_obj();
1030 address owner = NULL;1031
1032 markWord mark = read_stable_mark(obj);
1033
1034 // Uncontended case, header points to stack1035 if (mark.has_locker()) {1036 owner = (address) mark.locker();
1037 }
1038
1039 // Contended case, header points to ObjectMonitor (tagged pointer)
1040 else if (mark.has_monitor()) {
1041 // The first stage of async deflation does not affect any field
1042 // used by this comparison so the ObjectMonitor* is usable here.
1043 ObjectMonitor* monitor = mark.monitor();
1044 assert(monitor != NULL, "monitor should be non-null");
1045 owner = (address) monitor->owner();1046 }1047 1048 if (owner != NULL) {1049 // owning_thread_from_monitor_owner() may also return NULL here1050 return Threads::owning_thread_from_monitor_owner(t_list, owner);
1051 }
1052
1053 // Unlocked case, header in place
1054 // Cannot have assertion since this object may have been
1055 // locked by another thread when reaching here.
1056 // assert(mark.is_neutral(), "sanity check");
1057
1058 return NULL;
1059 }
1060
1061 // Visitors ...
1062
1063 void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure, JavaThread* thread) {
1064 MonitorList::Iterator iter = _in_use_list.iterator();
1065 while (iter.has_next()) {
1066 ObjectMonitor* mid = iter.next();
1067 if (mid->owner() != thread) {
1068 continue;
1069 }
1070 if (!mid->is_being_async_deflated() && mid->object_peek() != NULL) {
1071 // Only process with closure if the object is set.
1072
1073 // monitors_iterate() is only called at a safepoint or when the
1074 // target thread is suspended or when the target thread is
1075 // operating on itself. The current closures in use today are
1076 // only interested in an owned ObjectMonitor and ownership
1077 // cannot be dropped under the calling contexts so the
1078 // ObjectMonitor cannot be async deflated.
1079 closure->do_monitor(mid);
1080 }
1081 }
1082 }
1083
1084 static bool monitors_used_above_threshold(MonitorList* list) {
1085 if (MonitorUsedDeflationThreshold == 0) { // disabled case is easy
1086 return false;
1087 }
1088 // Start with ceiling based on a per-thread estimate:
1089 size_t ceiling = ObjectSynchronizer::in_use_list_ceiling();
1090 size_t old_ceiling = ceiling;
1091 if (ceiling < list->max()) {
1092 // The max used by the system has exceeded the ceiling so use that:
1093 ceiling = list->max();
1094 }
1095 size_t monitors_used = list->count();
1096 if (monitors_used == 0) { // empty list is easy
1097 return false;
1098 }
1099 if (NoAsyncDeflationProgressMax != 0 &&
1100 _no_progress_cnt >= NoAsyncDeflationProgressMax) {
1101 float remainder = (100.0 - MonitorUsedDeflationThreshold) / 100.0;
1102 size_t new_ceiling = ceiling + (ceiling * remainder) + 1;
1103 ObjectSynchronizer::set_in_use_list_ceiling(new_ceiling);
1104 log_info(monitorinflation)("Too many deflations without progress; "
1105 "bumping in_use_list_ceiling from " SIZE_FORMAT
1106 " to " SIZE_FORMAT, old_ceiling, new_ceiling);
1107 _no_progress_cnt = 0;
1108 ceiling = new_ceiling;
1109 }
1110
1111 // Check if our monitor usage is above the threshold:
1112 size_t monitor_usage = (monitors_used * 100LL) / ceiling;
1113 if (int(monitor_usage) > MonitorUsedDeflationThreshold) {
1114 log_info(monitorinflation)("monitors_used=" SIZE_FORMAT ", ceiling=" SIZE_FORMAT
1115 ", monitor_usage=" SIZE_FORMAT ", threshold=" INTX_FORMAT,
1116 monitors_used, ceiling, monitor_usage, MonitorUsedDeflationThreshold);
1117 return true;
1118 }
1119
1120 return false;
1121 }
1122
1123 size_t ObjectSynchronizer::in_use_list_ceiling() {
1124 return _in_use_list_ceiling;
1125 }
1126
1127 void ObjectSynchronizer::dec_in_use_list_ceiling() {
1128 Atomic::sub(&_in_use_list_ceiling, AvgMonitorsPerThreadEstimate);
1129 }
1130
1131 void ObjectSynchronizer::inc_in_use_list_ceiling() {
1132 Atomic::add(&_in_use_list_ceiling, AvgMonitorsPerThreadEstimate);
1133 }
1134
1135 void ObjectSynchronizer::set_in_use_list_ceiling(size_t new_value) {
1136 _in_use_list_ceiling = new_value;
1137 }
1138
1139 bool ObjectSynchronizer::is_async_deflation_needed() {
1140 if (is_async_deflation_requested()) {
1141 // Async deflation request.
1142 log_info(monitorinflation)("Async deflation needed: explicit request");
1143 return true;
1144 }
1145
1146 jlong time_since_last = time_since_last_async_deflation_ms();
1147
1148 if (AsyncDeflationInterval > 0 &&
1149 time_since_last > AsyncDeflationInterval &&
1150 monitors_used_above_threshold(&_in_use_list)) {
1151 // It's been longer than our specified deflate interval and there
1152 // are too many monitors in use. We don't deflate more frequently
1153 // than AsyncDeflationInterval (unless is_async_deflation_requested)
1154 // in order to not swamp the MonitorDeflationThread.
1155 log_info(monitorinflation)("Async deflation needed: monitors used are above the threshold");
1156 return true;
1157 }
1158
1159 if (GuaranteedAsyncDeflationInterval > 0 &&
1160 time_since_last > GuaranteedAsyncDeflationInterval) {
1161 // It's been longer than our specified guaranteed deflate interval.
1162 // We need to clean up the used monitors even if the threshold is
1163 // not reached, to keep the memory utilization at bay when many threads
1164 // touched many monitors.
1165 log_info(monitorinflation)("Async deflation needed: guaranteed interval (" INTX_FORMAT " ms) "
1166 "is greater than time since last deflation (" JLONG_FORMAT " ms)",
1167 GuaranteedAsyncDeflationInterval, time_since_last);
1168
1169 // If this deflation has no progress, then it should not affect the no-progress
1170 // tracking, otherwise threshold heuristics would think it was triggered, experienced
1171 // no progress, and needs to backoff more aggressively. In this "no progress" case,
1172 // the generic code would bump the no-progress counter, and we compensate for that
1173 // by telling it to skip the update.
1174 //
1175 // If this deflation has progress, then it should let non-progress tracking
1176 // know about this, otherwise the threshold heuristics would kick in, potentially
1177 // experience no-progress due to aggressive cleanup by this deflation, and think
1178 // it is still in no-progress stride. In this "progress" case, the generic code would
1179 // zero the counter, and we allow it to happen.
1180 _no_progress_skip_increment = true;
1181
1182 return true;
1183 }
1184
1185 return false;
1186 }
1187
1188 bool ObjectSynchronizer::request_deflate_idle_monitors() {
1189 JavaThread* current = JavaThread::current();
1190 bool ret_code = false;
1191
1192 jlong last_time = last_async_deflation_time_ns();
1193 set_is_async_deflation_requested(true);
1194 {
1195 MonitorLocker ml(MonitorDeflation_lock, Mutex::_no_safepoint_check_flag);
1196 ml.notify_all();
1197 }
1198 const int N_CHECKS = 5;
1199 for (int i = 0; i < N_CHECKS; i++) { // sleep for at most 5 seconds
1200 if (last_async_deflation_time_ns() > last_time) {
1201 log_info(monitorinflation)("Async Deflation happened after %d check(s).", i);
1202 ret_code = true;
1203 break;
1204 }
1205 {
1206 // JavaThread has to honor the blocking protocol.
1207 ThreadBlockInVM tbivm(current);
1208 os::naked_short_sleep(999); // sleep for almost 1 second
1209 }
1210 }
1211 if (!ret_code) {
1212 log_info(monitorinflation)("Async Deflation DID NOT happen after %d checks.", N_CHECKS);
1213 }
1214
1215 return ret_code;
1216 }
1217
1218 jlong ObjectSynchronizer::time_since_last_async_deflation_ms() {
1219 return (os::javaTimeNanos() - last_async_deflation_time_ns()) / (NANOUNITS / MILLIUNITS);
1220 }
1221
1222 static void post_monitor_inflate_event(EventJavaMonitorInflate* event,
1223 const oop obj,
1224 ObjectSynchronizer::InflateCause cause) {
1225 assert(event != NULL, "invariant");
1226 assert(event->should_commit(), "invariant");
1227 event->set_monitorClass(obj->klass());
1228 event->set_address((uintptr_t)(void*)obj);
1229 event->set_cause((u1)cause);
1230 event->commit();
1231 }
1232
1233 // Fast path code shared by multiple functions
1234 void ObjectSynchronizer::inflate_helper(oop obj) {
1235 markWord mark = obj->mark();
1236 if (mark.has_monitor()) {
1237 ObjectMonitor* monitor = mark.monitor();
1238 markWord dmw = monitor->header();
1239 assert(dmw.is_neutral(), "sanity check: header=" INTPTR_FORMAT, dmw.value());
1240 return;
1241 }
1242 (void)inflate(Thread::current(), obj, inflate_cause_vm_internal);
1243 }
1244
1245 ObjectMonitor* ObjectSynchronizer::inflate(Thread* current, oop object,
1246 const InflateCause cause) {
1247 EventJavaMonitorInflate event;
1248
1249 for (;;) {
1250 const markWord mark = object->mark();
1251 assert(!mark.has_bias_pattern(), "invariant");
1252
1253 // The mark can be in one of the following states:
1254 // * Inflated - just return1255 // * Stack-locked - coerce it to inflated
1256 // * INFLATING - busy wait for conversion to complete
1257 // * Neutral - aggressively inflate the object.
1258 // * BIASED - Illegal. We should never see this
1259
1260 // CASE: inflated
1261 if (mark.has_monitor()) {
1262 ObjectMonitor* inf = mark.monitor();
1263 markWord dmw = inf->header();
1264 assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
1265 return inf;
1266 }
1267
1268 // CASE: inflation in progress - inflating over a stack-lock.
1269 // Some other thread is converting from stack-locked to inflated.
1270 // Only that thread can complete inflation -- other threads must wait.
1271 // The INFLATING value is transient.
1272 // Currently, we spin/yield/park and poll the markword, waiting for inflation to finish.
1273 // We could always eliminate polling by parking the thread on some auxiliary list.
1274 if (mark == markWord::INFLATING()) {1275 read_stable_mark(object);1276 continue;
1277 }
1278
1279 // CASE: stack-locked
1280 // Could be stack-locked either by this thread or by some other thread.
1281 //
1282 // Note that we allocate the ObjectMonitor speculatively, _before_ attempting
1283 // to install INFLATING into the mark word. We originally installed INFLATING,
1284 // allocated the ObjectMonitor, and then finally STed the address of the
1285 // ObjectMonitor into the mark. This was correct, but artificially lengthened
1286 // the interval in which INFLATING appeared in the mark, thus increasing
1287 // the odds of inflation contention.
1288
1289 LogStreamHandle(Trace, monitorinflation) lsh;1290 1291 if (mark.has_locker()) {
1292 ObjectMonitor* m = new ObjectMonitor(object);
1293 // Optimistically prepare the ObjectMonitor - anticipate successful CAS
1294 // We do this before the CAS in order to minimize the length of time
1295 // in which INFLATING appears in the mark.
1296
1297 markWord cmp = object->cas_set_mark(markWord::INFLATING(), mark);
1298 if (cmp != mark) {
1299 delete m;
1300 continue; // Interference -- just retry
1301 }
1302
1303 // We've successfully installed INFLATING (0) into the mark-word.
1304 // This is the only case where 0 will appear in a mark-word.
1305 // Only the singular thread that successfully swings the mark-word
1306 // to 0 can perform (or more precisely, complete) inflation.
1307 //
1308 // Why do we CAS a 0 into the mark-word instead of just CASing the
1309 // mark-word from the stack-locked value directly to the new inflated state?
1310 // Consider what happens when a thread unlocks a stack-locked object.
1311 // It attempts to use CAS to swing the displaced header value from the
1312 // on-stack BasicLock back into the object header. Recall also that the
1313 // header value (hash code, etc) can reside in (a) the object header, or
1314 // (b) a displaced header associated with the stack-lock, or (c) a displaced
1315 // header in an ObjectMonitor. The inflate() routine must copy the header
1316 // value from the BasicLock on the owner's stack to the ObjectMonitor, all
1317 // the while preserving the hashCode stability invariants. If the owner
1318 // decides to release the lock while the value is 0, the unlock will fail
1319 // and control will eventually pass from slow_exit() to inflate. The owner
1320 // will then spin, waiting for the 0 value to disappear. Put another way,
1321 // the 0 causes the owner to stall if the owner happens to try to
1322 // drop the lock (restoring the header from the BasicLock to the object)
1323 // while inflation is in-progress. This protocol avoids races that might
1324 // would otherwise permit hashCode values to change or "flicker" for an object.
1325 // Critically, while object->mark is 0 mark.displaced_mark_helper() is stable.
1326 // 0 serves as a "BUSY" inflate-in-progress indicator.
1327
1328
1329 // fetch the displaced mark from the owner's stack.
1330 // The owner can't die or unwind past the lock while our INFLATING
1331 // object is in the mark. Furthermore the owner can't complete
1332 // an unlock on the object, either.
1333 markWord dmw = mark.displaced_mark_helper();
1334 // Catch if the object's header is not neutral (not locked and
1335 // not marked is what we care about here).
1336 assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
1337
1338 // Setup monitor fields to proper values -- prepare the monitor
1339 m->set_header(dmw);
1340
1341 // Optimization: if the mark.locker stack address is associated
1342 // with this thread we could simply set m->_owner = current.
1343 // Note that a thread can inflate an object
1344 // that it has stack-locked -- as might happen in wait() -- directly
1345 // with CAS. That is, we can avoid the xchg-NULL .... ST idiom.
1346 m->set_owner_from(NULL, mark.locker());
1347 // TODO-FIXME: assert BasicLock->dhw != 0.
1348
1349 // Must preserve store ordering. The monitor state must
1350 // be stable at the time of publishing the monitor address.
1351 guarantee(object->mark() == markWord::INFLATING(), "invariant");
1352 // Release semantics so that above set_object() is seen first.
1353 object->release_set_mark(markWord::encode(m));
1354
1355 // Once ObjectMonitor is configured and the object is associated
1356 // with the ObjectMonitor, it is safe to allow async deflation:
1357 _in_use_list.add(m);
1358
1359 // Hopefully the performance counters are allocated on distinct cache lines
1360 // to avoid false sharing on MP systems ...
1361 OM_PERFDATA_OP(Inflations, inc());
1362 if (log_is_enabled(Trace, monitorinflation)) {
1363 ResourceMark rm(current);
1364 lsh.print_cr("inflate(has_locker): object=" INTPTR_FORMAT ", mark="
1365 INTPTR_FORMAT ", type='%s'", p2i(object),
1366 object->mark().value(), object->klass()->external_name());
1367 }
1368 if (event.should_commit()) {
1369 post_monitor_inflate_event(&event, object, cause);
1370 }
1371 return m;
1372 }
1373
1374 // CASE: neutral
1375 // TODO-FIXME: for entry we currently inflate and then try to CAS _owner.
1376 // If we know we're inflating for entry it's better to inflate by swinging a
1377 // pre-locked ObjectMonitor pointer into the object header. A successful
1378 // CAS inflates the object *and* confers ownership to the inflating thread.
1379 // In the current implementation we use a 2-step mechanism where we CAS()
1380 // to inflate and then CAS() again to try to swing _owner from NULL to current.
1381 // An inflateTry() method that we could call from enter() would be useful.
1382
1383 // Catch if the object's header is not neutral (not locked and
1384 // not marked is what we care about here).
1385 assert(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT, mark.value());
1386 ObjectMonitor* m = new ObjectMonitor(object);
1387 // prepare m for installation - set monitor to initial state
1388 m->set_header(mark);
1389
1390 if (object->cas_set_mark(markWord::encode(m), mark) != mark) {
1391 delete m;
1392 m = NULL;
1393 continue;
1394 // interference - the markword changed - just retry.
1395 // The state-transitions are one-way, so there's no chance of
1396 // live-lock -- "Inflated" is an absorbing state.
1397 }
1398
1399 // Once the ObjectMonitor is configured and object is associated
1400 // with the ObjectMonitor, it is safe to allow async deflation:
1401 _in_use_list.add(m);
1402
1403 // Hopefully the performance counters are allocated on distinct
1404 // cache lines to avoid false sharing on MP systems ...
1405 OM_PERFDATA_OP(Inflations, inc());
1406 if (log_is_enabled(Trace, monitorinflation)) {
1407 ResourceMark rm(current);
1408 lsh.print_cr("inflate(neutral): object=" INTPTR_FORMAT ", mark="
1409 INTPTR_FORMAT ", type='%s'", p2i(object),
1410 object->mark().value(), object->klass()->external_name());
1411 }
1412 if (event.should_commit()) {
1413 post_monitor_inflate_event(&event, object, cause);
1414 }
1415 return m;
1416 }
1417 }
1418
1419 void ObjectSynchronizer::chk_for_block_req(JavaThread* current, const char* op_name,
1420 const char* cnt_name, size_t cnt,
1421 LogStream* ls, elapsedTimer* timer_p) {
1422 if (!SafepointMechanism::should_process(current)) {
1423 return;
1424 }
1425
1426 // A safepoint/handshake has started.
1427 if (ls != NULL) {
1428 timer_p->stop();
1429 ls->print_cr("pausing %s: %s=" SIZE_FORMAT ", in_use_list stats: ceiling="
1430 SIZE_FORMAT ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT,
1431 op_name, cnt_name, cnt, in_use_list_ceiling(),
1432 _in_use_list.count(), _in_use_list.max());
1433 }
1434
1435 {
1436 // Honor block request.
1437 ThreadBlockInVM tbivm(current);
1438 }
1439
1440 if (ls != NULL) {
1441 ls->print_cr("resuming %s: in_use_list stats: ceiling=" SIZE_FORMAT
1442 ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT, op_name,
1443 in_use_list_ceiling(), _in_use_list.count(), _in_use_list.max());
1444 timer_p->start();
1445 }
1446 }
1447
1448 // Walk the in-use list and deflate (at most MonitorDeflationMax) idle
1449 // ObjectMonitors. Returns the number of deflated ObjectMonitors.
1450 size_t ObjectSynchronizer::deflate_monitor_list(Thread* current, LogStream* ls,
1451 elapsedTimer* timer_p) {
1452 MonitorList::Iterator iter = _in_use_list.iterator();
1453 size_t deflated_count = 0;
1454
1455 while (iter.has_next()) {
1456 if (deflated_count >= (size_t)MonitorDeflationMax) {
1457 break;
1458 }
1459 ObjectMonitor* mid = iter.next();
1460 if (mid->deflate_monitor()) {
1461 deflated_count++;
1462 }
1463
1464 if (current->is_Java_thread()) {
1465 // A JavaThread must check for a safepoint/handshake and honor it.
1466 chk_for_block_req(current->as_Java_thread(), "deflation", "deflated_count",
1467 deflated_count, ls, timer_p);
1468 }
1469 }
1470
1471 return deflated_count;
1472 }
1473
1474 class HandshakeForDeflation : public HandshakeClosure {
1475 public:
1476 HandshakeForDeflation() : HandshakeClosure("HandshakeForDeflation") {}
1477
1478 void do_thread(Thread* thread) {
1479 log_trace(monitorinflation)("HandshakeForDeflation::do_thread: thread="
1480 INTPTR_FORMAT, p2i(thread));
1481 }
1482 };
1483
1484 // This function is called by the MonitorDeflationThread to deflate
1485 // ObjectMonitors. It is also called via do_final_audit_and_print_stats()
1486 // by the VMThread.
1487 size_t ObjectSynchronizer::deflate_idle_monitors() {
1488 Thread* current = Thread::current();
1489 if (current->is_Java_thread()) {
1490 // The async deflation request has been processed.
1491 _last_async_deflation_time_ns = os::javaTimeNanos();
1492 set_is_async_deflation_requested(false);
1493 }
1494
1495 LogStreamHandle(Debug, monitorinflation) lsh_debug;
1496 LogStreamHandle(Info, monitorinflation) lsh_info;
1497 LogStream* ls = NULL;
1498 if (log_is_enabled(Debug, monitorinflation)) {
1499 ls = &lsh_debug;
1500 } else if (log_is_enabled(Info, monitorinflation)) {
1501 ls = &lsh_info;
1502 }
1503
1504 elapsedTimer timer;
1505 if (ls != NULL) {
1506 ls->print_cr("begin deflating: in_use_list stats: ceiling=" SIZE_FORMAT ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT,
1507 in_use_list_ceiling(), _in_use_list.count(), _in_use_list.max());
1508 timer.start();
1509 }
1510
1511 // Deflate some idle ObjectMonitors.
1512 size_t deflated_count = deflate_monitor_list(current, ls, &timer);
1513 if (deflated_count > 0 || is_final_audit()) {
1514 // There are ObjectMonitors that have been deflated or this is the
1515 // final audit and all the remaining ObjectMonitors have been
1516 // deflated, BUT the MonitorDeflationThread blocked for the final
1517 // safepoint during unlinking.
1518
1519 // Unlink deflated ObjectMonitors from the in-use list.
1520 ResourceMark rm;
1521 GrowableArray<ObjectMonitor*> delete_list((int)deflated_count);
1522 size_t unlinked_count = _in_use_list.unlink_deflated(current, ls, &timer,
1523 &delete_list);
1524 if (current->is_Java_thread()) {
1525 if (ls != NULL) {
1526 timer.stop();
1527 ls->print_cr("before handshaking: unlinked_count=" SIZE_FORMAT
1528 ", in_use_list stats: ceiling=" SIZE_FORMAT ", count="
1529 SIZE_FORMAT ", max=" SIZE_FORMAT,
1530 unlinked_count, in_use_list_ceiling(),
1531 _in_use_list.count(), _in_use_list.max());
1532 }
1533
1534 // A JavaThread needs to handshake in order to safely free the
1535 // ObjectMonitors that were deflated in this cycle.
1536 HandshakeForDeflation hfd_hc;
1537 Handshake::execute(&hfd_hc);
1538
1539 if (ls != NULL) {
1540 ls->print_cr("after handshaking: in_use_list stats: ceiling="
1541 SIZE_FORMAT ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT,
1542 in_use_list_ceiling(), _in_use_list.count(), _in_use_list.max());
1543 timer.start();
1544 }
1545 }
1546
1547 // After the handshake, safely free the ObjectMonitors that were
1548 // deflated in this cycle.
1549 size_t deleted_count = 0;
1550 for (ObjectMonitor* monitor: delete_list) {
1551 delete monitor;
1552 deleted_count++;
1553
1554 if (current->is_Java_thread()) {
1555 // A JavaThread must check for a safepoint/handshake and honor it.
1556 chk_for_block_req(current->as_Java_thread(), "deletion", "deleted_count",
1557 deleted_count, ls, &timer);
1558 }
1559 }
1560 }
1561
1562 if (ls != NULL) {
1563 timer.stop();
1564 if (deflated_count != 0 || log_is_enabled(Debug, monitorinflation)) {
1565 ls->print_cr("deflated " SIZE_FORMAT " monitors in %3.7f secs",
1566 deflated_count, timer.seconds());
1567 }
1568 ls->print_cr("end deflating: in_use_list stats: ceiling=" SIZE_FORMAT ", count=" SIZE_FORMAT ", max=" SIZE_FORMAT,
1569 in_use_list_ceiling(), _in_use_list.count(), _in_use_list.max());
1570 }
1571
1572 OM_PERFDATA_OP(MonExtant, set_value(_in_use_list.count()));
1573 OM_PERFDATA_OP(Deflations, inc(deflated_count));
1574
1575 GVars.stw_random = os::random();
1576
1577 if (deflated_count != 0) {
1578 _no_progress_cnt = 0;
1579 } else if (_no_progress_skip_increment) {
1580 _no_progress_skip_increment = false;
1581 } else {
1582 _no_progress_cnt++;
1583 }
1584
1585 return deflated_count;
1586 }
1587
1588 // Monitor cleanup on JavaThread::exit
1589
1590 // Iterate through monitor cache and attempt to release thread's monitors
1591 class ReleaseJavaMonitorsClosure: public MonitorClosure {
1592 private:
1593 JavaThread* _thread;
1594
1595 public:
1596 ReleaseJavaMonitorsClosure(JavaThread* thread) : _thread(thread) {}
1597 void do_monitor(ObjectMonitor* mid) {
1598 (void)mid->complete_exit(_thread);
1599 }
1600 };
1601
1602 // Release all inflated monitors owned by current thread. Lightweight monitors are
1603 // ignored. This is meant to be called during JNI thread detach which assumes
1604 // all remaining monitors are heavyweight. All exceptions are swallowed.
1605 // Scanning the extant monitor list can be time consuming.
1606 // A simple optimization is to add a per-thread flag that indicates a thread
1607 // called jni_monitorenter() during its lifetime.
1608 //
1609 // Instead of NoSafepointVerifier it might be cheaper to
1610 // use an idiom of the form:
1611 // auto int tmp = SafepointSynchronize::_safepoint_counter ;
1612 // <code that must not run at safepoint>
1613 // guarantee (((tmp ^ _safepoint_counter) | (tmp & 1)) == 0) ;
1614 // Since the tests are extremely cheap we could leave them enabled
1615 // for normal product builds.
1616
1617 void ObjectSynchronizer::release_monitors_owned_by_thread(JavaThread* current) {
1618 assert(current == JavaThread::current(), "must be current Java thread");
1619 NoSafepointVerifier nsv;
1620 ReleaseJavaMonitorsClosure rjmc(current);
1621 ObjectSynchronizer::monitors_iterate(&rjmc, current);
1622 assert(!current->has_pending_exception(), "Should not be possible");
1623 current->clear_pending_exception();
1624 }
1625
1626 const char* ObjectSynchronizer::inflate_cause_name(const InflateCause cause) {
1627 switch (cause) {
1628 case inflate_cause_vm_internal: return "VM Internal";
1629 case inflate_cause_monitor_enter: return "Monitor Enter";
1630 case inflate_cause_wait: return "Monitor Wait";
1631 case inflate_cause_notify: return "Monitor Notify";
1632 case inflate_cause_hash_code: return "Monitor Hash Code";
1633 case inflate_cause_jni_enter: return "JNI Monitor Enter";
1634 case inflate_cause_jni_exit: return "JNI Monitor Exit";
1635 default:
1636 ShouldNotReachHere();
1637 }
1638 return "Unknown";
1639 }
1640
1641 //------------------------------------------------------------------------------
1642 // Debugging code
1643
1644 u_char* ObjectSynchronizer::get_gvars_addr() {
1645 return (u_char*)&GVars;
1646 }
1647
1648 u_char* ObjectSynchronizer::get_gvars_hc_sequence_addr() {
1649 return (u_char*)&GVars.hc_sequence;
1650 }
1651
1652 size_t ObjectSynchronizer::get_gvars_size() {
1653 return sizeof(SharedGlobals);
1654 }
1655
1656 u_char* ObjectSynchronizer::get_gvars_stw_random_addr() {
1657 return (u_char*)&GVars.stw_random;
1658 }
1659
1660 // Do the final audit and print of ObjectMonitor stats; must be done
1661 // by the VMThread at VM exit time.
1662 void ObjectSynchronizer::do_final_audit_and_print_stats() {
1663 assert(Thread::current()->is_VM_thread(), "sanity check");
1664
1665 if (is_final_audit()) { // Only do the audit once.
1666 return;
1667 }
1668 set_is_final_audit();
1669 log_info(monitorinflation)("Starting the final audit.");
1670
1671 if (log_is_enabled(Info, monitorinflation)) {
1672 // Do a deflation in order to reduce the in-use monitor population
1673 // that is reported by ObjectSynchronizer::log_in_use_monitor_details()
1674 // which is called by ObjectSynchronizer::audit_and_print_stats().
1675 while (ObjectSynchronizer::deflate_idle_monitors() != 0) {
1676 ; // empty
1677 }
1678 // The other audit_and_print_stats() call is done at the Debug
1679 // level at a safepoint in ObjectSynchronizer::do_safepoint_work().
1680 ObjectSynchronizer::audit_and_print_stats(true /* on_exit */);
1681 }
1682 }
1683
1684 // This function can be called at a safepoint or it can be called when
1685 // we are trying to exit the VM. When we are trying to exit the VM, the
1686 // list walker functions can run in parallel with the other list
1687 // operations so spin-locking is used for safety.
1688 //
1689 // Calls to this function can be added in various places as a debugging
1690 // aid; pass 'true' for the 'on_exit' parameter to have in-use monitor
1691 // details logged at the Info level and 'false' for the 'on_exit'
1692 // parameter to have in-use monitor details logged at the Trace level.
1693 //
1694 void ObjectSynchronizer::audit_and_print_stats(bool on_exit) {
1695 assert(on_exit || SafepointSynchronize::is_at_safepoint(), "invariant");
1696
1697 LogStreamHandle(Debug, monitorinflation) lsh_debug;
1698 LogStreamHandle(Info, monitorinflation) lsh_info;
1699 LogStreamHandle(Trace, monitorinflation) lsh_trace;
1700 LogStream* ls = NULL;
1701 if (log_is_enabled(Trace, monitorinflation)) {
1702 ls = &lsh_trace;
1703 } else if (log_is_enabled(Debug, monitorinflation)) {
1704 ls = &lsh_debug;
1705 } else if (log_is_enabled(Info, monitorinflation)) {
1706 ls = &lsh_info;
1707 }
1708 assert(ls != NULL, "sanity check");
1709
1710 int error_cnt = 0;
1711
1712 ls->print_cr("Checking in_use_list:");
1713 chk_in_use_list(ls, &error_cnt);
1714
1715 if (error_cnt == 0) {
1716 ls->print_cr("No errors found in in_use_list checks.");
1717 } else {
1718 log_error(monitorinflation)("found in_use_list errors: error_cnt=%d", error_cnt);
1719 }
1720
1721 if ((on_exit && log_is_enabled(Info, monitorinflation)) ||
1722 (!on_exit && log_is_enabled(Trace, monitorinflation))) {
1723 // When exiting this log output is at the Info level. When called
1724 // at a safepoint, this log output is at the Trace level since
1725 // there can be a lot of it.
1726 log_in_use_monitor_details(ls);
1727 }
1728
1729 ls->flush();
1730
1731 guarantee(error_cnt == 0, "ERROR: found monitor list errors: error_cnt=%d", error_cnt);
1732 }
1733
1734 // Check the in_use_list; log the results of the checks.
1735 void ObjectSynchronizer::chk_in_use_list(outputStream* out, int *error_cnt_p) {
1736 size_t l_in_use_count = _in_use_list.count();
1737 size_t l_in_use_max = _in_use_list.max();
1738 out->print_cr("count=" SIZE_FORMAT ", max=" SIZE_FORMAT, l_in_use_count,
1739 l_in_use_max);
1740
1741 size_t ck_in_use_count = 0;
1742 MonitorList::Iterator iter = _in_use_list.iterator();
1743 while (iter.has_next()) {
1744 ObjectMonitor* mid = iter.next();
1745 chk_in_use_entry(mid, out, error_cnt_p);
1746 ck_in_use_count++;
1747 }
1748
1749 if (l_in_use_count == ck_in_use_count) {
1750 out->print_cr("in_use_count=" SIZE_FORMAT " equals ck_in_use_count="
1751 SIZE_FORMAT, l_in_use_count, ck_in_use_count);
1752 } else {
1753 out->print_cr("WARNING: in_use_count=" SIZE_FORMAT " is not equal to "
1754 "ck_in_use_count=" SIZE_FORMAT, l_in_use_count,
1755 ck_in_use_count);
1756 }
1757
1758 size_t ck_in_use_max = _in_use_list.max();
1759 if (l_in_use_max == ck_in_use_max) {
1760 out->print_cr("in_use_max=" SIZE_FORMAT " equals ck_in_use_max="
1761 SIZE_FORMAT, l_in_use_max, ck_in_use_max);
1762 } else {
1763 out->print_cr("WARNING: in_use_max=" SIZE_FORMAT " is not equal to "
1764 "ck_in_use_max=" SIZE_FORMAT, l_in_use_max, ck_in_use_max);
1765 }
1766 }
1767
1768 // Check an in-use monitor entry; log any errors.
1769 void ObjectSynchronizer::chk_in_use_entry(ObjectMonitor* n, outputStream* out,
1770 int* error_cnt_p) {
1771 if (n->owner_is_DEFLATER_MARKER()) {
1772 // This should not happen, but if it does, it is not fatal.
1773 out->print_cr("WARNING: monitor=" INTPTR_FORMAT ": in-use monitor is "
1774 "deflated.", p2i(n));
1775 return;
1776 }
1777 if (n->header().value() == 0) {
1778 out->print_cr("ERROR: monitor=" INTPTR_FORMAT ": in-use monitor must "
1779 "have non-NULL _header field.", p2i(n));
1780 *error_cnt_p = *error_cnt_p + 1;
1781 }
1782 const oop obj = n->object_peek();
1783 if (obj != NULL) {
1784 const markWord mark = obj->mark();
1785 if (!mark.has_monitor()) {
1786 out->print_cr("ERROR: monitor=" INTPTR_FORMAT ": in-use monitor's "
1787 "object does not think it has a monitor: obj="
1788 INTPTR_FORMAT ", mark=" INTPTR_FORMAT, p2i(n),
1789 p2i(obj), mark.value());
1790 *error_cnt_p = *error_cnt_p + 1;
1791 }
1792 ObjectMonitor* const obj_mon = mark.monitor();
1793 if (n != obj_mon) {
1794 out->print_cr("ERROR: monitor=" INTPTR_FORMAT ": in-use monitor's "
1795 "object does not refer to the same monitor: obj="
1796 INTPTR_FORMAT ", mark=" INTPTR_FORMAT ", obj_mon="
1797 INTPTR_FORMAT, p2i(n), p2i(obj), mark.value(), p2i(obj_mon));
1798 *error_cnt_p = *error_cnt_p + 1;
1799 }
1800 }
1801 }
1802
1803 // Log details about ObjectMonitors on the in_use_list. The 'BHL'
1804 // flags indicate why the entry is in-use, 'object' and 'object type'
1805 // indicate the associated object and its type.
1806 void ObjectSynchronizer::log_in_use_monitor_details(outputStream* out) {
1807 stringStream ss;
1808 if (_in_use_list.count() > 0) {
1809 out->print_cr("In-use monitor info:");
1810 out->print_cr("(B -> is_busy, H -> has hash code, L -> lock status)");
1811 out->print_cr("%18s %s %18s %18s",
1812 "monitor", "BHL", "object", "object type");
1813 out->print_cr("================== === ================== ==================");
1814 MonitorList::Iterator iter = _in_use_list.iterator();
1815 while (iter.has_next()) {
1816 ObjectMonitor* mid = iter.next();
1817 const oop obj = mid->object_peek();
1818 const markWord mark = mid->header();
1819 ResourceMark rm;
1820 out->print(INTPTR_FORMAT " %d%d%d " INTPTR_FORMAT " %s", p2i(mid),
1821 mid->is_busy(), mark.hash() != 0, mid->owner() != NULL,
1822 p2i(obj), obj == NULL ? "" : obj->klass()->external_name());
1823 if (mid->is_busy()) {
1824 out->print(" (%s)", mid->is_busy_to_string(&ss));
1825 ss.reset();
1826 }
1827 out->cr();
1828 }
1829 }
1830
1831 out->flush();
1832 }
--- EOF ---