1 /*
2 * Copyright (c) 1997, 2019, 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/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "code/icBuffer.hpp"
30 #include "code/nmethod.hpp"
31 #include "code/pcDesc.hpp"
32 #include "code/scopeDesc.hpp"
33 #include "gc_interface/collectedHeap.hpp"
34 #include "interpreter/interpreter.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "memory/universe.inline.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "oops/symbol.hpp"
39 #include "runtime/compilationPolicy.hpp"
40 #include "runtime/deoptimization.hpp"
41 #include "runtime/frame.inline.hpp"
42 #include "runtime/interfaceSupport.hpp"
43 #include "runtime/mutexLocker.hpp"
44 #include "runtime/orderAccess.inline.hpp"
45 #include "runtime/osThread.hpp"
46 #include "runtime/safepoint.hpp"
47 #include "runtime/signature.hpp"
48 #include "runtime/stubCodeGenerator.hpp"
49 #include "runtime/stubRoutines.hpp"
50 #include "runtime/sweeper.hpp"
51 #include "runtime/synchronizer.hpp"
52 #include "runtime/thread.inline.hpp"
53 #include "services/runtimeService.hpp"
54 #include "utilities/events.hpp"
55 #include "utilities/macros.hpp"
56 #ifdef TARGET_ARCH_x86
57 # include "nativeInst_x86.hpp"
58 # include "vmreg_x86.inline.hpp"
59 #endif
60 #ifdef TARGET_ARCH_sparc
61 # include "nativeInst_sparc.hpp"
62 # include "vmreg_sparc.inline.hpp"
63 #endif
64 #ifdef TARGET_ARCH_zero
65 # include "nativeInst_zero.hpp"
66 # include "vmreg_zero.inline.hpp"
67 #endif
68 #ifdef TARGET_ARCH_arm
69 # include "nativeInst_arm.hpp"
70 # include "vmreg_arm.inline.hpp"
71 #endif
72 #ifdef TARGET_ARCH_ppc
73 # include "nativeInst_ppc.hpp"
74 # include "vmreg_ppc.inline.hpp"
75 #endif
76 #if INCLUDE_ALL_GCS
77 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
78 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
79 #endif // INCLUDE_ALL_GCS
80 #ifdef COMPILER1
81 #include "c1/c1_globals.hpp"
82 #endif
83
84 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
85
86 // --------------------------------------------------------------------------------------------------
87 // Implementation of Safepoint begin/end
88
89 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
90 volatile int SafepointSynchronize::_waiting_to_block = 0;
91 volatile int SafepointSynchronize::_safepoint_counter = 0;
92 int SafepointSynchronize::_current_jni_active_count = 0;
93 long SafepointSynchronize::_end_of_last_safepoint = 0;
94 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
95 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
96 static bool timeout_error_printed = false;
97
98 // Roll all threads forward to a safepoint and suspend them all
99 void SafepointSynchronize::begin() {
100 EventSafepointBegin begin_event;
101
102 Thread* myThread = Thread::current();
103 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
104
105 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
106 _safepoint_begin_time = os::javaTimeNanos();
107 _ts_of_current_safepoint = tty->time_stamp().seconds();
108 }
109
110 #if INCLUDE_ALL_GCS
111 if (UseConcMarkSweepGC) {
112 // In the future we should investigate whether CMS can use the
113 // more-general mechanism below. DLD (01/05).
114 ConcurrentMarkSweepThread::synchronize(false);
115 } else if (UseG1GC) {
116 SuspendibleThreadSet::synchronize();
117 }
118 #endif // INCLUDE_ALL_GCS
119
120 // By getting the Threads_lock, we assure that no threads are about to start or
121 // exit. It is released again in SafepointSynchronize::end().
122 Threads_lock->lock();
123
124 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
125
126 int nof_threads = Threads::number_of_threads();
127
128 if (TraceSafepoint) {
129 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
130 }
131
132 RuntimeService::record_safepoint_begin();
133
134 MutexLocker mu(Safepoint_lock);
135
136 // Reset the count of active JNI critical threads
137 _current_jni_active_count = 0;
138
139 // Set number of threads to wait for, before we initiate the callbacks
140 _waiting_to_block = nof_threads;
141 TryingToBlock = 0 ;
142 int still_running = nof_threads;
143
144 // Save the starting time, so that it can be compared to see if this has taken
145 // too long to complete.
146 jlong safepoint_limit_time = 0;
147 timeout_error_printed = false;
148
149 // PrintSafepointStatisticsTimeout can be specified separately. When
150 // specified, PrintSafepointStatistics will be set to true in
151 // deferred_initialize_stat method. The initialization has to be done
152 // early enough to avoid any races. See bug 6880029 for details.
153 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
154 deferred_initialize_stat();
155 }
156
157 // Begin the process of bringing the system to a safepoint.
158 // Java threads can be in several different states and are
159 // stopped by different mechanisms:
160 //
161 // 1. Running interpreted
162 // The interpeter dispatch table is changed to force it to
163 // check for a safepoint condition between bytecodes.
164 // 2. Running in native code
165 // When returning from the native code, a Java thread must check
166 // the safepoint _state to see if we must block. If the
167 // VM thread sees a Java thread in native, it does
168 // not wait for this thread to block. The order of the memory
169 // writes and reads of both the safepoint state and the Java
170 // threads state is critical. In order to guarantee that the
171 // memory writes are serialized with respect to each other,
172 // the VM thread issues a memory barrier instruction
173 // (on MP systems). In order to avoid the overhead of issuing
174 // a memory barrier for each Java thread making native calls, each Java
175 // thread performs a write to a single memory page after changing
176 // the thread state. The VM thread performs a sequence of
177 // mprotect OS calls which forces all previous writes from all
178 // Java threads to be serialized. This is done in the
179 // os::serialize_thread_states() call. This has proven to be
180 // much more efficient than executing a membar instruction
181 // on every call to native code.
182 // 3. Running compiled Code
183 // Compiled code reads a global (Safepoint Polling) page that
184 // is set to fault if we are trying to get to a safepoint.
185 // 4. Blocked
186 // A thread which is blocked will not be allowed to return from the
187 // block condition until the safepoint operation is complete.
188 // 5. In VM or Transitioning between states
189 // If a Java thread is currently running in the VM or transitioning
190 // between states, the safepointing code will wait for the thread to
191 // block itself when it attempts transitions to a new state.
192 //
193 EventSafepointStateSynchronization sync_event;
194 int initial_running = 0;
195 _state = _synchronizing;
196 OrderAccess::fence();
197
198 // Flush all thread states to memory
199 if (!UseMembar) {
200 os::serialize_thread_states();
201 }
202
203 // Make interpreter safepoint aware
204 Interpreter::notice_safepoints();
205
206 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
207 // Make polling safepoint aware
208 guarantee (PageArmed == 0, "invariant") ;
209 PageArmed = 1 ;
210 os::make_polling_page_unreadable();
211 }
212
213 // Consider using active_processor_count() ... but that call is expensive.
214 int ncpus = os::processor_count() ;
215
216 #ifdef ASSERT
217 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
218 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
219 // Clear the visited flag to ensure that the critical counts are collected properly.
220 cur->set_visited_for_critical_count(false);
221 }
222 #endif // ASSERT
223
224 if (SafepointTimeout)
225 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
226
227 // Iterate through all threads until it have been determined how to stop them all at a safepoint
228 unsigned int iterations = 0;
229 int steps = 0 ;
230 while(still_running > 0) {
231 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
232 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
233 ThreadSafepointState *cur_state = cur->safepoint_state();
234 if (cur_state->is_running()) {
235 cur_state->examine_state_of_thread();
236 if (!cur_state->is_running()) {
237 still_running--;
238 // consider adjusting steps downward:
239 // steps = 0
240 // steps -= NNN
241 // steps >>= 1
242 // steps = MIN(steps, 2000-100)
243 // if (iterations != 0) steps -= NNN
244 }
245 if (TraceSafepoint && Verbose) cur_state->print();
246 }
247 }
248
249 if (iterations == 0) {
250 initial_running = still_running;
251 if (PrintSafepointStatistics) {
252 begin_statistics(nof_threads, still_running);
253 }
254 }
255
256 if (still_running > 0) {
257 // Check for if it takes to long
258 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
259 print_safepoint_timeout(_spinning_timeout);
260 }
261
262 // Spin to avoid context switching.
263 // There's a tension between allowing the mutators to run (and rendezvous)
264 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
265 // a mutator might otherwise use profitably to reach a safepoint. Excessive
266 // spinning by the VM thread on a saturated system can increase rendezvous latency.
267 // Blocking or yielding incur their own penalties in the form of context switching
268 // and the resultant loss of $ residency.
269 //
270 // Further complicating matters is that yield() does not work as naively expected
271 // on many platforms -- yield() does not guarantee that any other ready threads
272 // will run. As such we revert yield_all() after some number of iterations.
273 // Yield_all() is implemented as a short unconditional sleep on some platforms.
274 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
275 // can actually increase the time it takes the VM thread to detect that a system-wide
276 // stop-the-world safepoint has been reached. In a pathological scenario such as that
277 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
278 // In that case the mutators will be stalled waiting for the safepoint to complete and the
279 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
280 // will eventually wake up and detect that all mutators are safe, at which point
281 // we'll again make progress.
282 //
283 // Beware too that that the VMThread typically runs at elevated priority.
284 // Its default priority is higher than the default mutator priority.
285 // Obviously, this complicates spinning.
286 //
287 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
288 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
289 //
290 // See the comments in synchronizer.cpp for additional remarks on spinning.
291 //
292 // In the future we might:
293 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
294 // This is tricky as the path used by a thread exiting the JVM (say on
295 // on JNI call-out) simply stores into its state field. The burden
296 // is placed on the VM thread, which must poll (spin).
297 // 2. Find something useful to do while spinning. If the safepoint is GC-related
298 // we might aggressively scan the stacks of threads that are already safe.
299 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
300 // If all the mutators are ONPROC there's no reason to sleep or yield.
301 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
302 // 5. Check system saturation. If the system is not fully saturated then
303 // simply spin and avoid sleep/yield.
304 // 6. As still-running mutators rendezvous they could unpark the sleeping
305 // VMthread. This works well for still-running mutators that become
306 // safe. The VMthread must still poll for mutators that call-out.
307 // 7. Drive the policy on time-since-begin instead of iterations.
308 // 8. Consider making the spin duration a function of the # of CPUs:
309 // Spin = (((ncpus-1) * M) + K) + F(still_running)
310 // Alternately, instead of counting iterations of the outer loop
311 // we could count the # of threads visited in the inner loop, above.
312 // 9. On windows consider using the return value from SwitchThreadTo()
313 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
314
315 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
316 guarantee (PageArmed == 0, "invariant") ;
317 PageArmed = 1 ;
318 os::make_polling_page_unreadable();
319 }
320
321 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
322 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
323 ++steps ;
324 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
325 SpinPause() ; // MP-Polite spin
326 } else
327 if (steps < DeferThrSuspendLoopCount) {
328 os::NakedYield() ;
329 } else {
330 os::yield_all(steps) ;
331 // Alternately, the VM thread could transiently depress its scheduling priority or
332 // transiently increase the priority of the tardy mutator(s).
333 }
334
335 iterations ++ ;
336 }
337 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
338 }
339 assert(still_running == 0, "sanity check");
340
341 if (PrintSafepointStatistics) {
342 update_statistics_on_spin_end();
343 }
344
345 if (sync_event.should_commit()) {
346 // Group this event together with the ones committed after the counter is increased
347 sync_event.set_safepointId(safepoint_counter() + 1);
348 sync_event.set_initialThreadCount(initial_running);
349 sync_event.set_runningThreadCount(_waiting_to_block);
350 sync_event.set_iterations(iterations);
351 sync_event.commit();
352 }
353
354 EventSafepointWaitBlocked wait_blocked_event;
355 int initial_waiting_to_block = _waiting_to_block;
356 // wait until all threads are stopped
357 while (_waiting_to_block > 0) {
358 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
359 if (!SafepointTimeout || timeout_error_printed) {
360 Safepoint_lock->wait(true); // true, means with no safepoint checks
361 } else {
362 // Compute remaining time
363 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
364
365 // If there is no remaining time, then there is an error
366 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
367 print_safepoint_timeout(_blocking_timeout);
368 }
369 }
370 }
371 assert(_waiting_to_block == 0, "sanity check");
372
373 #ifndef PRODUCT
374 if (SafepointTimeout) {
375 jlong current_time = os::javaTimeNanos();
376 if (safepoint_limit_time < current_time) {
377 tty->print_cr("# SafepointSynchronize: Finished after "
378 INT64_FORMAT_W(6) " ms",
379 ((current_time - safepoint_limit_time) / MICROUNITS +
380 SafepointTimeoutDelay));
381 }
382 }
383 #endif
384
385 assert((_safepoint_counter & 0x1) == 0, "must be even");
386 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
387 _safepoint_counter ++;
388
389 // Record state
390 _state = _synchronized;
391
392 OrderAccess::fence();
393
394 if (wait_blocked_event.should_commit()) {
395 wait_blocked_event.set_safepointId(safepoint_counter());
396 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
397 wait_blocked_event.commit();
398 }
399
400 #ifdef ASSERT
401 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
402 // make sure all the threads were visited
403 assert(cur->was_visited_for_critical_count(), "missed a thread");
404 }
405 #endif // ASSERT
406
407 // Update the count of active JNI critical regions
408 GC_locker::set_jni_lock_count(_current_jni_active_count);
409
410 if (TraceSafepoint) {
411 VM_Operation *op = VMThread::vm_operation();
412 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
413 }
414
415 RuntimeService::record_safepoint_synchronized();
416 if (PrintSafepointStatistics) {
417 update_statistics_on_sync_end(os::javaTimeNanos());
418 }
419
420 // Call stuff that needs to be run when a safepoint is just about to be completed
421 EventSafepointCleanup cleanup_event;
422 do_cleanup_tasks();
423
424 if (cleanup_event.should_commit()) {
425 cleanup_event.set_safepointId(safepoint_counter());
426 cleanup_event.commit();
427 }
428
429 if (PrintSafepointStatistics) {
430 // Record how much time spend on the above cleanup tasks
431 update_statistics_on_cleanup_end(os::javaTimeNanos());
432 }
433
434 if (begin_event.should_commit()) {
435 begin_event.set_safepointId(safepoint_counter());
436 begin_event.set_totalThreadCount(nof_threads);
437 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
438 begin_event.commit();
439 }
440 }
441
442 // Wake up all threads, so they are ready to resume execution after the safepoint
443 // operation has been carried out
444 void SafepointSynchronize::end() {
445 EventSafepointEnd event;
446 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
447
448 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
449 assert((_safepoint_counter & 0x1) == 1, "must be odd");
450 _safepoint_counter ++;
451 // memory fence isn't required here since an odd _safepoint_counter
452 // value can do no harm and a fence is issued below anyway.
453
454 DEBUG_ONLY(Thread* myThread = Thread::current();)
455 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
456
457 if (PrintSafepointStatistics) {
458 end_statistics(os::javaTimeNanos());
459 }
460
461 #ifdef ASSERT
462 // A pending_exception cannot be installed during a safepoint. The threads
463 // may install an async exception after they come back from a safepoint into
464 // pending_exception after they unblock. But that should happen later.
465 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
466 assert (!(cur->has_pending_exception() &&
467 cur->safepoint_state()->is_at_poll_safepoint()),
468 "safepoint installed a pending exception");
469 }
470 #endif // ASSERT
471
472 if (PageArmed) {
473 // Make polling safepoint aware
474 os::make_polling_page_readable();
475 PageArmed = 0 ;
476 }
477
478 // Remove safepoint check from interpreter
479 Interpreter::ignore_safepoints();
480
481 {
482 MutexLocker mu(Safepoint_lock);
483
484 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
485
486 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
487 // when they get restarted.
488 _state = _not_synchronized;
489 OrderAccess::fence();
490
491 if (TraceSafepoint) {
492 tty->print_cr("Leaving safepoint region");
493 }
494
495 // Start suspended threads
496 for(JavaThread *current = Threads::first(); current; current = current->next()) {
497 // A problem occurring on Solaris is when attempting to restart threads
498 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
499 // to the next one (since it has been running the longest). We then have
500 // to wait for a cpu to become available before we can continue restarting
501 // threads.
502 // FIXME: This causes the performance of the VM to degrade when active and with
503 // large numbers of threads. Apparently this is due to the synchronous nature
504 // of suspending threads.
505 //
506 // TODO-FIXME: the comments above are vestigial and no longer apply.
507 // Furthermore, using solaris' schedctl in this particular context confers no benefit
508 if (VMThreadHintNoPreempt) {
509 os::hint_no_preempt();
510 }
511 ThreadSafepointState* cur_state = current->safepoint_state();
512 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
513 cur_state->restart();
514 assert(cur_state->is_running(), "safepoint state has not been reset");
515 }
516
517 RuntimeService::record_safepoint_end();
518
519 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
520 // blocked in signal_thread_blocked
521 Threads_lock->unlock();
522
523 }
524 #if INCLUDE_ALL_GCS
525 // If there are any concurrent GC threads resume them.
526 if (UseConcMarkSweepGC) {
527 ConcurrentMarkSweepThread::desynchronize(false);
528 } else if (UseG1GC) {
529 SuspendibleThreadSet::desynchronize();
530 }
531 #endif // INCLUDE_ALL_GCS
532 // record this time so VMThread can keep track how much time has elasped
533 // since last safepoint.
534 _end_of_last_safepoint = os::javaTimeMillis();
535
536 if (event.should_commit()) {
537 event.set_safepointId(safepoint_id);
538 event.commit();
539 }
540 }
541
542 bool SafepointSynchronize::is_cleanup_needed() {
543 // Need a safepoint if some inline cache buffers is non-empty
544 if (!InlineCacheBuffer::is_empty()) return true;
545 return false;
546 }
547
548 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
549 if (event.should_commit()) {
550 event.set_safepointId(SafepointSynchronize::safepoint_counter());
551 event.set_name(name);
552 event.commit();
553 }
554 }
555
556 // Various cleaning tasks that should be done periodically at safepoints
557 void SafepointSynchronize::do_cleanup_tasks() {
558 {
559 const char* name = "deflating idle monitors";
560 EventSafepointCleanupTask event;
561 TraceTime t1(name, TraceSafepointCleanupTime);
562 ObjectSynchronizer::deflate_idle_monitors();
563 event_safepoint_cleanup_task_commit(event, name);
564 }
565
566 {
567 const char* name = "updating inline caches";
568 EventSafepointCleanupTask event;
569 TraceTime t2(name, TraceSafepointCleanupTime);
570 InlineCacheBuffer::update_inline_caches();
571 event_safepoint_cleanup_task_commit(event, name);
572 }
573 {
574 const char* name = "compilation policy safepoint handler";
575 EventSafepointCleanupTask event;
576 TraceTime t3(name, TraceSafepointCleanupTime);
577 CompilationPolicy::policy()->do_safepoint_work();
578 event_safepoint_cleanup_task_commit(event, name);
579 }
580
581 {
582 const char* name = "mark nmethods";
583 EventSafepointCleanupTask event;
584 TraceTime t4(name, TraceSafepointCleanupTime);
585 NMethodSweeper::mark_active_nmethods();
586 event_safepoint_cleanup_task_commit(event, name);
587 }
588
589 if (SymbolTable::needs_rehashing()) {
590 const char* name = "rehashing symbol table";
591 EventSafepointCleanupTask event;
592 TraceTime t5(name, TraceSafepointCleanupTime);
593 SymbolTable::rehash_table();
594 event_safepoint_cleanup_task_commit(event, name);
595 }
596
597 if (StringTable::needs_rehashing()) {
598 const char* name = "rehashing string table";
599 EventSafepointCleanupTask event;
600 TraceTime t6(name, TraceSafepointCleanupTime);
601 StringTable::rehash_table();
602 event_safepoint_cleanup_task_commit(event, name);
603 }
604
605 // rotate log files?
606 if (UseGCLogFileRotation) {
607 const char* name = "rotate gc log";
608 EventSafepointCleanupTask event;
609 gclog_or_tty->rotate_log(false);
610 event_safepoint_cleanup_task_commit(event, name);
611 }
612
613 {
614 // CMS delays purging the CLDG until the beginning of the next safepoint and to
615 // make sure concurrent sweep is done
616 const char* name = "purging class loader data graph";
617 EventSafepointCleanupTask event;
618 TraceTime t7(name, TraceSafepointCleanupTime);
619 ClassLoaderDataGraph::purge_if_needed();
620 event_safepoint_cleanup_task_commit(event, name);
621 }
622 }
623
624
625 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
626 switch(state) {
627 case _thread_in_native:
628 // native threads are safe if they have no java stack or have walkable stack
629 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
630
631 // blocked threads should have already have walkable stack
632 case _thread_blocked:
633 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
634 return true;
635
636 default:
637 return false;
638 }
639 }
640
641
642 // See if the thread is running inside a lazy critical native and
643 // update the thread critical count if so. Also set a suspend flag to
644 // cause the native wrapper to return into the JVM to do the unlock
645 // once the native finishes.
646 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
647 if (state == _thread_in_native &&
648 thread->has_last_Java_frame() &&
649 thread->frame_anchor()->walkable()) {
650 // This thread might be in a critical native nmethod so look at
651 // the top of the stack and increment the critical count if it
652 // is.
653 frame wrapper_frame = thread->last_frame();
654 CodeBlob* stub_cb = wrapper_frame.cb();
655 if (stub_cb != NULL &&
656 stub_cb->is_nmethod() &&
657 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
658 // A thread could potentially be in a critical native across
659 // more than one safepoint, so only update the critical state on
660 // the first one. When it returns it will perform the unlock.
661 if (!thread->do_critical_native_unlock()) {
662 #ifdef ASSERT
663 if (!thread->in_critical()) {
664 GC_locker::increment_debug_jni_lock_count();
665 }
666 #endif
667 thread->enter_critical();
668 // Make sure the native wrapper calls back on return to
669 // perform the needed critical unlock.
670 thread->set_critical_native_unlock();
671 }
672 }
673 }
674 }
675
676
677
678 // -------------------------------------------------------------------------------------------------------
679 // Implementation of Safepoint callback point
680
681 void SafepointSynchronize::block(JavaThread *thread) {
682 assert(thread != NULL, "thread must be set");
683 assert(thread->is_Java_thread(), "not a Java thread");
684
685 // Threads shouldn't block if they are in the middle of printing, but...
686 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
687
688 // Only bail from the block() call if the thread is gone from the
689 // thread list; starting to exit should still block.
690 if (thread->is_terminated()) {
691 // block current thread if we come here from native code when VM is gone
692 thread->block_if_vm_exited();
693
694 // otherwise do nothing
695 return;
696 }
697
698 JavaThreadState state = thread->thread_state();
699 thread->frame_anchor()->make_walkable(thread);
700
701 // Check that we have a valid thread_state at this point
702 switch(state) {
703 case _thread_in_vm_trans:
704 case _thread_in_Java: // From compiled code
705
706 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
707 // we pretend we are still in the VM.
708 thread->set_thread_state(_thread_in_vm);
709
710 if (is_synchronizing()) {
711 Atomic::inc (&TryingToBlock) ;
712 }
713
714 // We will always be holding the Safepoint_lock when we are examine the state
715 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
716 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
717 Safepoint_lock->lock_without_safepoint_check();
718 if (is_synchronizing()) {
719 // Decrement the number of threads to wait for and signal vm thread
720 assert(_waiting_to_block > 0, "sanity check");
721 _waiting_to_block--;
722 thread->safepoint_state()->set_has_called_back(true);
723
724 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
725 if (thread->in_critical()) {
726 // Notice that this thread is in a critical section
727 increment_jni_active_count();
728 }
729
730 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
731 if (_waiting_to_block == 0) {
732 Safepoint_lock->notify_all();
733 }
734 }
735
736 // We transition the thread to state _thread_blocked here, but
737 // we can't do our usual check for external suspension and then
738 // self-suspend after the lock_without_safepoint_check() call
739 // below because we are often called during transitions while
740 // we hold different locks. That would leave us suspended while
741 // holding a resource which results in deadlocks.
742 thread->set_thread_state(_thread_blocked);
743 Safepoint_lock->unlock();
744
745 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
746 // the entire safepoint, the threads will all line up here during the safepoint.
747 Threads_lock->lock_without_safepoint_check();
748 // restore original state. This is important if the thread comes from compiled code, so it
749 // will continue to execute with the _thread_in_Java state.
750 thread->set_thread_state(state);
751 Threads_lock->unlock();
752 break;
753
754 case _thread_in_native_trans:
755 case _thread_blocked_trans:
756 case _thread_new_trans:
757 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
758 thread->print_thread_state();
759 fatal("Deadlock in safepoint code. "
760 "Should have called back to the VM before blocking.");
761 }
762
763 // We transition the thread to state _thread_blocked here, but
764 // we can't do our usual check for external suspension and then
765 // self-suspend after the lock_without_safepoint_check() call
766 // below because we are often called during transitions while
767 // we hold different locks. That would leave us suspended while
768 // holding a resource which results in deadlocks.
769 thread->set_thread_state(_thread_blocked);
770
771 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
772 // the safepoint code might still be waiting for it to block. We need to change the state here,
773 // so it can see that it is at a safepoint.
774
775 // Block until the safepoint operation is completed.
776 Threads_lock->lock_without_safepoint_check();
777
778 // Restore state
779 thread->set_thread_state(state);
780
781 Threads_lock->unlock();
782 break;
783
784 default:
785 fatal(err_msg("Illegal threadstate encountered: %d", state));
786 }
787
788 // Check for pending. async. exceptions or suspends - except if the
789 // thread was blocked inside the VM. has_special_runtime_exit_condition()
790 // is called last since it grabs a lock and we only want to do that when
791 // we must.
792 //
793 // Note: we never deliver an async exception at a polling point as the
794 // compiler may not have an exception handler for it. The polling
795 // code will notice the async and deoptimize and the exception will
796 // be delivered. (Polling at a return point is ok though). Sure is
797 // a lot of bother for a deprecated feature...
798 //
799 // We don't deliver an async exception if the thread state is
800 // _thread_in_native_trans so JNI functions won't be called with
801 // a surprising pending exception. If the thread state is going back to java,
802 // async exception is checked in check_special_condition_for_native_trans().
803
804 if (state != _thread_blocked_trans &&
805 state != _thread_in_vm_trans &&
806 thread->has_special_runtime_exit_condition()) {
807 thread->handle_special_runtime_exit_condition(
808 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
809 }
810 }
811
812 // ------------------------------------------------------------------------------------------------------
813 // Exception handlers
814
815
816 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
817 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
818 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
819 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
820
821 if (ShowSafepointMsgs) {
822 tty->print("handle_polling_page_exception: ");
823 }
824
825 if (PrintSafepointStatistics) {
826 inc_page_trap_count();
827 }
828
829 ThreadSafepointState* state = thread->safepoint_state();
830
831 state->handle_polling_page_exception();
832 }
833
834
835 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
836 if (!timeout_error_printed) {
837 timeout_error_printed = true;
838 // Print out the thread infor which didn't reach the safepoint for debugging
839 // purposes (useful when there are lots of threads in the debugger).
840 tty->cr();
841 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
842 if (reason == _spinning_timeout) {
843 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
844 } else if (reason == _blocking_timeout) {
845 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
846 }
847
848 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
849 ThreadSafepointState *cur_state;
850 ResourceMark rm;
851 for(JavaThread *cur_thread = Threads::first(); cur_thread;
852 cur_thread = cur_thread->next()) {
853 cur_state = cur_thread->safepoint_state();
854
855 if (cur_thread->thread_state() != _thread_blocked &&
856 ((reason == _spinning_timeout && cur_state->is_running()) ||
857 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
858 tty->print("# ");
859 cur_thread->print();
860 tty->cr();
861 }
862 }
863 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
864 }
865
866 // To debug the long safepoint, specify both DieOnSafepointTimeout &
867 // ShowMessageBoxOnError.
868 if (DieOnSafepointTimeout) {
869 char msg[1024];
870 VM_Operation *op = VMThread::vm_operation();
871 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
872 SafepointTimeoutDelay,
873 op != NULL ? op->name() : "no vm operation");
874 fatal(msg);
875 }
876 }
877
878
879 // -------------------------------------------------------------------------------------------------------
880 // Implementation of ThreadSafepointState
881
882 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
883 _thread = thread;
884 _type = _running;
885 _has_called_back = false;
886 _at_poll_safepoint = false;
887 }
888
889 void ThreadSafepointState::create(JavaThread *thread) {
890 ThreadSafepointState *state = new ThreadSafepointState(thread);
891 thread->set_safepoint_state(state);
892 }
893
894 void ThreadSafepointState::destroy(JavaThread *thread) {
895 if (thread->safepoint_state()) {
896 delete(thread->safepoint_state());
897 thread->set_safepoint_state(NULL);
898 }
899 }
900
901 void ThreadSafepointState::examine_state_of_thread() {
902 assert(is_running(), "better be running or just have hit safepoint poll");
903
904 JavaThreadState state = _thread->thread_state();
905
906 // Save the state at the start of safepoint processing.
907 _orig_thread_state = state;
908
909 // Check for a thread that is suspended. Note that thread resume tries
910 // to grab the Threads_lock which we own here, so a thread cannot be
911 // resumed during safepoint synchronization.
912
913 // We check to see if this thread is suspended without locking to
914 // avoid deadlocking with a third thread that is waiting for this
915 // thread to be suspended. The third thread can notice the safepoint
916 // that we're trying to start at the beginning of its SR_lock->wait()
917 // call. If that happens, then the third thread will block on the
918 // safepoint while still holding the underlying SR_lock. We won't be
919 // able to get the SR_lock and we'll deadlock.
920 //
921 // We don't need to grab the SR_lock here for two reasons:
922 // 1) The suspend flags are both volatile and are set with an
923 // Atomic::cmpxchg() call so we should see the suspended
924 // state right away.
925 // 2) We're being called from the safepoint polling loop; if
926 // we don't see the suspended state on this iteration, then
927 // we'll come around again.
928 //
929 bool is_suspended = _thread->is_ext_suspended();
930 if (is_suspended) {
931 roll_forward(_at_safepoint);
932 return;
933 }
934
935 // Some JavaThread states have an initial safepoint state of
936 // running, but are actually at a safepoint. We will happily
937 // agree and update the safepoint state here.
938 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
939 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
940 roll_forward(_at_safepoint);
941 return;
942 }
943
944 if (state == _thread_in_vm) {
945 roll_forward(_call_back);
946 return;
947 }
948
949 // All other thread states will continue to run until they
950 // transition and self-block in state _blocked
951 // Safepoint polling in compiled code causes the Java threads to do the same.
952 // Note: new threads may require a malloc so they must be allowed to finish
953
954 assert(is_running(), "examine_state_of_thread on non-running thread");
955 return;
956 }
957
958 // Returns true is thread could not be rolled forward at present position.
959 void ThreadSafepointState::roll_forward(suspend_type type) {
960 _type = type;
961
962 switch(_type) {
963 case _at_safepoint:
964 SafepointSynchronize::signal_thread_at_safepoint();
965 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
966 if (_thread->in_critical()) {
967 // Notice that this thread is in a critical section
968 SafepointSynchronize::increment_jni_active_count();
969 }
970 break;
971
972 case _call_back:
973 set_has_called_back(false);
974 break;
975
976 case _running:
977 default:
978 ShouldNotReachHere();
979 }
980 }
981
982 void ThreadSafepointState::restart() {
983 switch(type()) {
984 case _at_safepoint:
985 case _call_back:
986 break;
987
988 case _running:
989 default:
990 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
991 _thread, _type);
992 _thread->print();
993 ShouldNotReachHere();
994 }
995 _type = _running;
996 set_has_called_back(false);
997 }
998
999
1000 void ThreadSafepointState::print_on(outputStream *st) const {
1001 const char *s = NULL;
1002
1003 switch(_type) {
1004 case _running : s = "_running"; break;
1005 case _at_safepoint : s = "_at_safepoint"; break;
1006 case _call_back : s = "_call_back"; break;
1007 default:
1008 ShouldNotReachHere();
1009 }
1010
1011 st->print_cr("Thread: " INTPTR_FORMAT
1012 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1013 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1014 _at_poll_safepoint);
1015
1016 _thread->print_thread_state_on(st);
1017 }
1018
1019
1020 // ---------------------------------------------------------------------------------------------------------------------
1021
1022 // Block the thread at the safepoint poll or poll return.
1023 void ThreadSafepointState::handle_polling_page_exception() {
1024
1025 // Check state. block() will set thread state to thread_in_vm which will
1026 // cause the safepoint state _type to become _call_back.
1027 assert(type() == ThreadSafepointState::_running,
1028 "polling page exception on thread not running state");
1029
1030 // Step 1: Find the nmethod from the return address
1031 if (ShowSafepointMsgs && Verbose) {
1032 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1033 }
1034 address real_return_addr = thread()->saved_exception_pc();
1035
1036 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1037 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1038 nmethod* nm = (nmethod*)cb;
1039
1040 // Find frame of caller
1041 frame stub_fr = thread()->last_frame();
1042 CodeBlob* stub_cb = stub_fr.cb();
1043 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1044 RegisterMap map(thread(), true);
1045 frame caller_fr = stub_fr.sender(&map);
1046
1047 // Should only be poll_return or poll
1048 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1049
1050 // This is a poll immediately before a return. The exception handling code
1051 // has already had the effect of causing the return to occur, so the execution
1052 // will continue immediately after the call. In addition, the oopmap at the
1053 // return point does not mark the return value as an oop (if it is), so
1054 // it needs a handle here to be updated.
1055 if( nm->is_at_poll_return(real_return_addr) ) {
1056 // See if return type is an oop.
1057 bool return_oop = nm->method()->is_returning_oop();
1058 Handle return_value;
1059 if (return_oop) {
1060 // The oop result has been saved on the stack together with all
1061 // the other registers. In order to preserve it over GCs we need
1062 // to keep it in a handle.
1063 oop result = caller_fr.saved_oop_result(&map);
1064 assert(result == NULL || result->is_oop(), "must be oop");
1065 return_value = Handle(thread(), result);
1066 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1067 }
1068
1069 // Block the thread
1070 SafepointSynchronize::block(thread());
1071
1072 // restore oop result, if any
1073 if (return_oop) {
1074 caller_fr.set_saved_oop_result(&map, return_value());
1075 }
1076 }
1077
1078 // This is a safepoint poll. Verify the return address and block.
1079 else {
1080 set_at_poll_safepoint(true);
1081
1082 // verify the blob built the "return address" correctly
1083 assert(real_return_addr == caller_fr.pc(), "must match");
1084
1085 // Block the thread
1086 SafepointSynchronize::block(thread());
1087 set_at_poll_safepoint(false);
1088
1089 // If we have a pending async exception deoptimize the frame
1090 // as otherwise we may never deliver it.
1091 if (thread()->has_async_condition()) {
1092 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1093 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1094 }
1095
1096 // If an exception has been installed we must check for a pending deoptimization
1097 // Deoptimize frame if exception has been thrown.
1098
1099 if (thread()->has_pending_exception() ) {
1100 RegisterMap map(thread(), true);
1101 frame caller_fr = stub_fr.sender(&map);
1102 if (caller_fr.is_deoptimized_frame()) {
1103 // The exception patch will destroy registers that are still
1104 // live and will be needed during deoptimization. Defer the
1105 // Async exception should have defered the exception until the
1106 // next safepoint which will be detected when we get into
1107 // the interpreter so if we have an exception now things
1108 // are messed up.
1109
1110 fatal("Exception installed and deoptimization is pending");
1111 }
1112 }
1113 }
1114 }
1115
1116
1117 //
1118 // Statistics & Instrumentations
1119 //
1120 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1121 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1122 int SafepointSynchronize::_cur_stat_index = 0;
1123 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1124 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1125 jlong SafepointSynchronize::_max_sync_time = 0;
1126 jlong SafepointSynchronize::_max_vmop_time = 0;
1127 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1128
1129 static jlong cleanup_end_time = 0;
1130 static bool need_to_track_page_armed_status = false;
1131 static bool init_done = false;
1132
1133 // Helper method to print the header.
1134 static void print_header() {
1135 tty->print(" vmop "
1136 "[threads: total initially_running wait_to_block] ");
1137 tty->print("[time: spin block sync cleanup vmop] ");
1138
1139 // no page armed status printed out if it is always armed.
1140 if (need_to_track_page_armed_status) {
1141 tty->print("page_armed ");
1142 }
1143
1144 tty->print_cr("page_trap_count");
1145 }
1146
1147 void SafepointSynchronize::deferred_initialize_stat() {
1148 if (init_done) return;
1149
1150 if (PrintSafepointStatisticsCount <= 0) {
1151 fatal("Wrong PrintSafepointStatisticsCount");
1152 }
1153
1154 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1155 // be printed right away, in which case, _safepoint_stats will regress to
1156 // a single element array. Otherwise, it is a circular ring buffer with default
1157 // size of PrintSafepointStatisticsCount.
1158 int stats_array_size;
1159 if (PrintSafepointStatisticsTimeout > 0) {
1160 stats_array_size = 1;
1161 PrintSafepointStatistics = true;
1162 } else {
1163 stats_array_size = PrintSafepointStatisticsCount;
1164 }
1165 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1166 * sizeof(SafepointStats), mtInternal);
1167 guarantee(_safepoint_stats != NULL,
1168 "not enough memory for safepoint instrumentation data");
1169
1170 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1171 need_to_track_page_armed_status = true;
1172 }
1173 init_done = true;
1174 }
1175
1176 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1177 assert(init_done, "safepoint statistics array hasn't been initialized");
1178 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1179
1180 spstat->_time_stamp = _ts_of_current_safepoint;
1181
1182 VM_Operation *op = VMThread::vm_operation();
1183 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1184 if (op != NULL) {
1185 _safepoint_reasons[spstat->_vmop_type]++;
1186 }
1187
1188 spstat->_nof_total_threads = nof_threads;
1189 spstat->_nof_initial_running_threads = nof_running;
1190 spstat->_nof_threads_hit_page_trap = 0;
1191
1192 // Records the start time of spinning. The real time spent on spinning
1193 // will be adjusted when spin is done. Same trick is applied for time
1194 // spent on waiting for threads to block.
1195 if (nof_running != 0) {
1196 spstat->_time_to_spin = os::javaTimeNanos();
1197 } else {
1198 spstat->_time_to_spin = 0;
1199 }
1200 }
1201
1202 void SafepointSynchronize::update_statistics_on_spin_end() {
1203 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1204
1205 jlong cur_time = os::javaTimeNanos();
1206
1207 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1208 if (spstat->_nof_initial_running_threads != 0) {
1209 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1210 }
1211
1212 if (need_to_track_page_armed_status) {
1213 spstat->_page_armed = (PageArmed == 1);
1214 }
1215
1216 // Records the start time of waiting for to block. Updated when block is done.
1217 if (_waiting_to_block != 0) {
1218 spstat->_time_to_wait_to_block = cur_time;
1219 } else {
1220 spstat->_time_to_wait_to_block = 0;
1221 }
1222 }
1223
1224 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1225 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1226
1227 if (spstat->_nof_threads_wait_to_block != 0) {
1228 spstat->_time_to_wait_to_block = end_time -
1229 spstat->_time_to_wait_to_block;
1230 }
1231
1232 // Records the end time of sync which will be used to calculate the total
1233 // vm operation time. Again, the real time spending in syncing will be deducted
1234 // from the start of the sync time later when end_statistics is called.
1235 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1236 if (spstat->_time_to_sync > _max_sync_time) {
1237 _max_sync_time = spstat->_time_to_sync;
1238 }
1239
1240 spstat->_time_to_do_cleanups = end_time;
1241 }
1242
1243 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1244 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1245
1246 // Record how long spent in cleanup tasks.
1247 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1248
1249 cleanup_end_time = end_time;
1250 }
1251
1252 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1253 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1254
1255 // Update the vm operation time.
1256 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1257 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1258 _max_vmop_time = spstat->_time_to_exec_vmop;
1259 }
1260 // Only the sync time longer than the specified
1261 // PrintSafepointStatisticsTimeout will be printed out right away.
1262 // By default, it is -1 meaning all samples will be put into the list.
1263 if ( PrintSafepointStatisticsTimeout > 0) {
1264 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1265 print_statistics();
1266 }
1267 } else {
1268 // The safepoint statistics will be printed out when the _safepoin_stats
1269 // array fills up.
1270 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1271 print_statistics();
1272 _cur_stat_index = 0;
1273 } else {
1274 _cur_stat_index++;
1275 }
1276 }
1277 }
1278
1279 void SafepointSynchronize::print_statistics() {
1280 SafepointStats* sstats = _safepoint_stats;
1281
1282 for (int index = 0; index <= _cur_stat_index; index++) {
1283 if (index % 30 == 0) {
1284 print_header();
1285 }
1286 sstats = &_safepoint_stats[index];
1287 tty->print("%.3f: ", sstats->_time_stamp);
1288 tty->print("%-26s ["
1289 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1290 " ] ",
1291 sstats->_vmop_type == -1 ? "no vm operation" :
1292 VM_Operation::name(sstats->_vmop_type),
1293 sstats->_nof_total_threads,
1294 sstats->_nof_initial_running_threads,
1295 sstats->_nof_threads_wait_to_block);
1296 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1297 tty->print(" ["
1298 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1299 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1300 INT64_FORMAT_W(6) " ] ",
1301 sstats->_time_to_spin / MICROUNITS,
1302 sstats->_time_to_wait_to_block / MICROUNITS,
1303 sstats->_time_to_sync / MICROUNITS,
1304 sstats->_time_to_do_cleanups / MICROUNITS,
1305 sstats->_time_to_exec_vmop / MICROUNITS);
1306
1307 if (need_to_track_page_armed_status) {
1308 tty->print(INT32_FORMAT " ", sstats->_page_armed);
1309 }
1310 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
1311 }
1312 }
1313
1314 // This method will be called when VM exits. It will first call
1315 // print_statistics to print out the rest of the sampling. Then
1316 // it tries to summarize the sampling.
1317 void SafepointSynchronize::print_stat_on_exit() {
1318 if (_safepoint_stats == NULL) return;
1319
1320 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1321
1322 // During VM exit, end_statistics may not get called and in that
1323 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1324 // don't print it out.
1325 // Approximate the vm op time.
1326 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1327 os::javaTimeNanos() - cleanup_end_time;
1328
1329 if ( PrintSafepointStatisticsTimeout < 0 ||
1330 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1331 print_statistics();
1332 }
1333 tty->cr();
1334
1335 // Print out polling page sampling status.
1336 if (!need_to_track_page_armed_status) {
1337 if (UseCompilerSafepoints) {
1338 tty->print_cr("Polling page always armed");
1339 }
1340 } else {
1341 tty->print_cr("Defer polling page loop count = %d\n",
1342 DeferPollingPageLoopCount);
1343 }
1344
1345 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1346 if (_safepoint_reasons[index] != 0) {
1347 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1348 _safepoint_reasons[index]);
1349 }
1350 }
1351
1352 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1353 _coalesced_vmop_count);
1354 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1355 _max_sync_time / MICROUNITS);
1356 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1357 INT64_FORMAT_W(5) " ms",
1358 _max_vmop_time / MICROUNITS);
1359 }
1360
1361 // ------------------------------------------------------------------------------------------------
1362 // Non-product code
1363
1364 #ifndef PRODUCT
1365
1366 void SafepointSynchronize::print_state() {
1367 if (_state == _not_synchronized) {
1368 tty->print_cr("not synchronized");
1369 } else if (_state == _synchronizing || _state == _synchronized) {
1370 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1371 "synchronized");
1372
1373 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1374 cur->safepoint_state()->print();
1375 }
1376 }
1377 }
1378
1379 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1380 if (ShowSafepointMsgs) {
1381 va_list ap;
1382 va_start(ap, format);
1383 tty->vprint_cr(format, ap);
1384 va_end(ap);
1385 }
1386 }
1387
1388 #endif // !PRODUCT