1 /*
2 * Copyright (c) 1997, 2017, 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/stringTable.hpp"
27 #include "classfile/symbolTable.hpp"
28 #include "classfile/systemDictionary.hpp"
29 #include "code/codeCache.hpp"
30 #include "code/icBuffer.hpp"
31 #include "code/nmethod.hpp"
32 #include "code/pcDesc.hpp"
33 #include "code/scopeDesc.hpp"
34 #include "gc/shared/collectedHeap.hpp"
35 #include "gc/shared/gcLocker.inline.hpp"
36 #include "gc/shared/strongRootsScope.hpp"
37 #include "gc/shared/workgroup.hpp"
38 #include "interpreter/interpreter.hpp"
39 #include "logging/log.hpp"
40 #include "logging/logStream.hpp"
41 #include "memory/resourceArea.hpp"
42 #include "memory/universe.inline.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "oops/symbol.hpp"
45 #include "runtime/atomic.hpp"
46 #include "runtime/compilationPolicy.hpp"
47 #include "runtime/deoptimization.hpp"
48 #include "runtime/frame.inline.hpp"
49 #include "runtime/interfaceSupport.hpp"
50 #include "runtime/mutexLocker.hpp"
51 #include "runtime/orderAccess.inline.hpp"
52 #include "runtime/osThread.hpp"
53 #include "runtime/safepoint.hpp"
54 #include "runtime/signature.hpp"
55 #include "runtime/stubCodeGenerator.hpp"
56 #include "runtime/stubRoutines.hpp"
57 #include "runtime/sweeper.hpp"
58 #include "runtime/synchronizer.hpp"
59 #include "runtime/thread.inline.hpp"
60 #include "runtime/timerTrace.hpp"
61 #include "services/runtimeService.hpp"
62 #include "trace/tracing.hpp"
63 #include "trace/traceMacros.hpp"
64 #include "utilities/events.hpp"
65 #include "utilities/macros.hpp"
66 #ifdef COMPILER1
67 #include "c1/c1_globals.hpp"
68 #endif
69
70 // --------------------------------------------------------------------------------------------------
71 // Implementation of Safepoint begin/end
72
73 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
74 volatile int SafepointSynchronize::_waiting_to_block = 0;
75 volatile int SafepointSynchronize::_safepoint_counter = 0;
76 int SafepointSynchronize::_current_jni_active_count = 0;
77 long SafepointSynchronize::_end_of_last_safepoint = 0;
78 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
79 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
80 static bool timeout_error_printed = false;
81
82 // Roll all threads forward to a safepoint and suspend them all
83 void SafepointSynchronize::begin() {
84 EventSafepointBegin begin_event;
85 Thread* myThread = Thread::current();
86 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
87
88 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
89 _safepoint_begin_time = os::javaTimeNanos();
90 _ts_of_current_safepoint = tty->time_stamp().seconds();
91 }
92
93 Universe::heap()->safepoint_synchronize_begin();
94
95 // By getting the Threads_lock, we assure that no threads are about to start or
96 // exit. It is released again in SafepointSynchronize::end().
97 Threads_lock->lock();
98
99 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
100
101 int nof_threads = Threads::number_of_threads();
102
103 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
104
105 RuntimeService::record_safepoint_begin();
106
107 MutexLocker mu(Safepoint_lock);
108
109 // Reset the count of active JNI critical threads
110 _current_jni_active_count = 0;
111
112 // Set number of threads to wait for, before we initiate the callbacks
113 _waiting_to_block = nof_threads;
114 TryingToBlock = 0 ;
115 int still_running = nof_threads;
116
117 // Save the starting time, so that it can be compared to see if this has taken
118 // too long to complete.
119 jlong safepoint_limit_time = 0;
120 timeout_error_printed = false;
121
122 // PrintSafepointStatisticsTimeout can be specified separately. When
123 // specified, PrintSafepointStatistics will be set to true in
124 // deferred_initialize_stat method. The initialization has to be done
125 // early enough to avoid any races. See bug 6880029 for details.
126 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
127 deferred_initialize_stat();
128 }
129
130 // Begin the process of bringing the system to a safepoint.
131 // Java threads can be in several different states and are
132 // stopped by different mechanisms:
133 //
134 // 1. Running interpreted
135 // The interpreter dispatch table is changed to force it to
136 // check for a safepoint condition between bytecodes.
137 // 2. Running in native code
138 // When returning from the native code, a Java thread must check
139 // the safepoint _state to see if we must block. If the
140 // VM thread sees a Java thread in native, it does
141 // not wait for this thread to block. The order of the memory
142 // writes and reads of both the safepoint state and the Java
143 // threads state is critical. In order to guarantee that the
144 // memory writes are serialized with respect to each other,
145 // the VM thread issues a memory barrier instruction
146 // (on MP systems). In order to avoid the overhead of issuing
147 // a memory barrier for each Java thread making native calls, each Java
148 // thread performs a write to a single memory page after changing
149 // the thread state. The VM thread performs a sequence of
150 // mprotect OS calls which forces all previous writes from all
151 // Java threads to be serialized. This is done in the
152 // os::serialize_thread_states() call. This has proven to be
153 // much more efficient than executing a membar instruction
154 // on every call to native code.
155 // 3. Running compiled Code
156 // Compiled code reads a global (Safepoint Polling) page that
157 // is set to fault if we are trying to get to a safepoint.
158 // 4. Blocked
159 // A thread which is blocked will not be allowed to return from the
160 // block condition until the safepoint operation is complete.
161 // 5. In VM or Transitioning between states
162 // If a Java thread is currently running in the VM or transitioning
163 // between states, the safepointing code will wait for the thread to
164 // block itself when it attempts transitions to a new state.
165 //
166 {
167 EventSafepointStateSynchronization sync_event;
168 int initial_running = 0;
169
170 _state = _synchronizing;
171 OrderAccess::fence();
172
173 // Flush all thread states to memory
174 if (!UseMembar) {
175 os::serialize_thread_states();
176 }
177
178 // Make interpreter safepoint aware
179 Interpreter::notice_safepoints();
180
181 if (DeferPollingPageLoopCount < 0) {
182 // Make polling safepoint aware
183 guarantee (PageArmed == 0, "invariant") ;
184 PageArmed = 1 ;
185 os::make_polling_page_unreadable();
186 }
187
188 // Consider using active_processor_count() ... but that call is expensive.
189 int ncpus = os::processor_count() ;
190
191 #ifdef ASSERT
192 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
193 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
194 // Clear the visited flag to ensure that the critical counts are collected properly.
195 cur->set_visited_for_critical_count(false);
196 }
197 #endif // ASSERT
198
199 if (SafepointTimeout)
200 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
201
202 // Iterate through all threads until it have been determined how to stop them all at a safepoint
203 unsigned int iterations = 0;
204 int steps = 0 ;
205 while(still_running > 0) {
206 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
207 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
208 ThreadSafepointState *cur_state = cur->safepoint_state();
209 if (cur_state->is_running()) {
210 cur_state->examine_state_of_thread();
211 if (!cur_state->is_running()) {
212 still_running--;
213 // consider adjusting steps downward:
214 // steps = 0
215 // steps -= NNN
216 // steps >>= 1
217 // steps = MIN(steps, 2000-100)
218 // if (iterations != 0) steps -= NNN
219 }
220 LogTarget(Trace, safepoint) lt;
221 if (lt.is_enabled()) {
222 ResourceMark rm;
223 LogStream ls(lt);
224 cur_state->print_on(&ls);
225 }
226 }
227 }
228
229 if (iterations == 0) {
230 initial_running = still_running;
231 if (PrintSafepointStatistics) {
232 begin_statistics(nof_threads, still_running);
233 }
234 }
235
236 if (still_running > 0) {
237 // Check for if it takes to long
238 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
239 print_safepoint_timeout(_spinning_timeout);
240 }
241
242 // Spin to avoid context switching.
243 // There's a tension between allowing the mutators to run (and rendezvous)
244 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
245 // a mutator might otherwise use profitably to reach a safepoint. Excessive
246 // spinning by the VM thread on a saturated system can increase rendezvous latency.
247 // Blocking or yielding incur their own penalties in the form of context switching
248 // and the resultant loss of $ residency.
249 //
250 // Further complicating matters is that yield() does not work as naively expected
251 // on many platforms -- yield() does not guarantee that any other ready threads
252 // will run. As such we revert to naked_short_sleep() after some number of iterations.
253 // nakes_short_sleep() is implemented as a short unconditional sleep.
254 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
255 // can actually increase the time it takes the VM thread to detect that a system-wide
256 // stop-the-world safepoint has been reached. In a pathological scenario such as that
257 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
258 // In that case the mutators will be stalled waiting for the safepoint to complete and the
259 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
260 // will eventually wake up and detect that all mutators are safe, at which point
261 // we'll again make progress.
262 //
263 // Beware too that that the VMThread typically runs at elevated priority.
264 // Its default priority is higher than the default mutator priority.
265 // Obviously, this complicates spinning.
266 //
267 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
268 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
269 //
270 // See the comments in synchronizer.cpp for additional remarks on spinning.
271 //
272 // In the future we might:
273 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
274 // This is tricky as the path used by a thread exiting the JVM (say on
275 // on JNI call-out) simply stores into its state field. The burden
276 // is placed on the VM thread, which must poll (spin).
277 // 2. Find something useful to do while spinning. If the safepoint is GC-related
278 // we might aggressively scan the stacks of threads that are already safe.
279 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
280 // If all the mutators are ONPROC there's no reason to sleep or yield.
281 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
282 // 5. Check system saturation. If the system is not fully saturated then
283 // simply spin and avoid sleep/yield.
284 // 6. As still-running mutators rendezvous they could unpark the sleeping
285 // VMthread. This works well for still-running mutators that become
286 // safe. The VMthread must still poll for mutators that call-out.
287 // 7. Drive the policy on time-since-begin instead of iterations.
288 // 8. Consider making the spin duration a function of the # of CPUs:
289 // Spin = (((ncpus-1) * M) + K) + F(still_running)
290 // Alternately, instead of counting iterations of the outer loop
291 // we could count the # of threads visited in the inner loop, above.
292 // 9. On windows consider using the return value from SwitchThreadTo()
293 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
294
295 if (int(iterations) == DeferPollingPageLoopCount) {
296 guarantee (PageArmed == 0, "invariant") ;
297 PageArmed = 1 ;
298 os::make_polling_page_unreadable();
299 }
300
301 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
302 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
303 ++steps ;
304 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
305 SpinPause() ; // MP-Polite spin
306 } else
307 if (steps < DeferThrSuspendLoopCount) {
308 os::naked_yield() ;
309 } else {
310 os::naked_short_sleep(1);
311 }
312
313 iterations ++ ;
314 }
315 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
316 }
317 assert(still_running == 0, "sanity check");
318
319 if (PrintSafepointStatistics) {
320 update_statistics_on_spin_end();
321 }
322
323 if (sync_event.should_commit()) {
324 // Group this event together with the ones committed after the counter is increased
325 sync_event.set_safepointId(safepoint_counter() + 1);
326 sync_event.set_initialThreadCount(initial_running);
327 sync_event.set_runningThreadCount(_waiting_to_block);
328 sync_event.set_iterations(iterations);
329 sync_event.commit();
330 }
331 } //EventSafepointStateSync
332
333 // wait until all threads are stopped
334 {
335 EventSafepointWaitBlocked wait_blocked_event;
336 int initial_waiting_to_block = _waiting_to_block;
337
338 while (_waiting_to_block > 0) {
339 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
340 if (!SafepointTimeout || timeout_error_printed) {
341 Safepoint_lock->wait(true); // true, means with no safepoint checks
342 } else {
343 // Compute remaining time
344 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
345
346 // If there is no remaining time, then there is an error
347 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
348 print_safepoint_timeout(_blocking_timeout);
349 }
350 }
351 }
352 assert(_waiting_to_block == 0, "sanity check");
353
354 #ifndef PRODUCT
355 if (SafepointTimeout) {
356 jlong current_time = os::javaTimeNanos();
357 if (safepoint_limit_time < current_time) {
358 tty->print_cr("# SafepointSynchronize: Finished after "
359 INT64_FORMAT_W(6) " ms",
360 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
361 (jlong)SafepointTimeoutDelay));
362 }
363 }
364 #endif
365
366 assert((_safepoint_counter & 0x1) == 0, "must be even");
367 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
368 _safepoint_counter ++;
369
370 // Record state
371 _state = _synchronized;
372
373 OrderAccess::fence();
374
375 if (wait_blocked_event.should_commit()) {
376 wait_blocked_event.set_safepointId(safepoint_counter());
377 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
378 wait_blocked_event.commit();
379 }
380 } // EventSafepointWaitBlocked
381
382 #ifdef ASSERT
383 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
384 // make sure all the threads were visited
385 assert(cur->was_visited_for_critical_count(), "missed a thread");
386 }
387 #endif // ASSERT
388
389 // Update the count of active JNI critical regions
390 GCLocker::set_jni_lock_count(_current_jni_active_count);
391
392 if (log_is_enabled(Debug, safepoint)) {
393 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
394 }
395
396 RuntimeService::record_safepoint_synchronized();
397 if (PrintSafepointStatistics) {
398 update_statistics_on_sync_end(os::javaTimeNanos());
399 }
400
401 // Call stuff that needs to be run when a safepoint is just about to be completed
402 {
403 EventSafepointCleanup cleanup_event;
404 do_cleanup_tasks();
405 if (cleanup_event.should_commit()) {
406 cleanup_event.set_safepointId(safepoint_counter());
407 cleanup_event.commit();
408 }
409 }
410
411 if (PrintSafepointStatistics) {
412 // Record how much time spend on the above cleanup tasks
413 update_statistics_on_cleanup_end(os::javaTimeNanos());
414 }
415 if (begin_event.should_commit()) {
416 begin_event.set_safepointId(safepoint_counter());
417 begin_event.set_totalThreadCount(nof_threads);
418 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
419 begin_event.commit();
420 }
421 }
422
423 // Wake up all threads, so they are ready to resume execution after the safepoint
424 // operation has been carried out
425 void SafepointSynchronize::end() {
426 EventSafepointEnd event;
427 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
428
429 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
430 assert((_safepoint_counter & 0x1) == 1, "must be odd");
431 _safepoint_counter ++;
432 // memory fence isn't required here since an odd _safepoint_counter
433 // value can do no harm and a fence is issued below anyway.
434
435 DEBUG_ONLY(Thread* myThread = Thread::current();)
436 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
437
438 if (PrintSafepointStatistics) {
439 end_statistics(os::javaTimeNanos());
440 }
441
442 #ifdef ASSERT
443 // A pending_exception cannot be installed during a safepoint. The threads
444 // may install an async exception after they come back from a safepoint into
445 // pending_exception after they unblock. But that should happen later.
446 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
447 assert (!(cur->has_pending_exception() &&
448 cur->safepoint_state()->is_at_poll_safepoint()),
449 "safepoint installed a pending exception");
450 }
451 #endif // ASSERT
452
453 if (PageArmed) {
454 // Make polling safepoint aware
455 os::make_polling_page_readable();
456 PageArmed = 0 ;
457 }
458
459 // Remove safepoint check from interpreter
460 Interpreter::ignore_safepoints();
461
462 {
463 MutexLocker mu(Safepoint_lock);
464
465 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
466
467 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
468 // when they get restarted.
469 _state = _not_synchronized;
470 OrderAccess::fence();
471
472 log_debug(safepoint)("Leaving safepoint region");
473
474 // Start suspended threads
475 for(JavaThread *current = Threads::first(); current; current = current->next()) {
476 // A problem occurring on Solaris is when attempting to restart threads
477 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
478 // to the next one (since it has been running the longest). We then have
479 // to wait for a cpu to become available before we can continue restarting
480 // threads.
481 // FIXME: This causes the performance of the VM to degrade when active and with
482 // large numbers of threads. Apparently this is due to the synchronous nature
483 // of suspending threads.
484 //
485 // TODO-FIXME: the comments above are vestigial and no longer apply.
486 // Furthermore, using solaris' schedctl in this particular context confers no benefit
487 if (VMThreadHintNoPreempt) {
488 os::hint_no_preempt();
489 }
490 ThreadSafepointState* cur_state = current->safepoint_state();
491 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
492 cur_state->restart();
493 assert(cur_state->is_running(), "safepoint state has not been reset");
494 }
495
496 RuntimeService::record_safepoint_end();
497
498 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
499 // blocked in signal_thread_blocked
500 Threads_lock->unlock();
501
502 }
503 Universe::heap()->safepoint_synchronize_end();
504 // record this time so VMThread can keep track how much time has elapsed
505 // since last safepoint.
506 _end_of_last_safepoint = os::javaTimeMillis();
507
508 if (event.should_commit()) {
509 event.set_safepointId(safepoint_id);
510 event.commit();
511 }
512 }
513
514 bool SafepointSynchronize::is_cleanup_needed() {
515 // Need a safepoint if there are many monitors to deflate.
516 if (ObjectSynchronizer::is_cleanup_needed()) return true;
517 // Need a safepoint if some inline cache buffers is non-empty
518 if (!InlineCacheBuffer::is_empty()) return true;
519 return false;
520 }
521
522 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
523 if (event.should_commit()) {
524 event.set_safepointId(SafepointSynchronize::safepoint_counter());
525 event.set_name(name);
526 event.commit();
527 }
528 }
529
530 class ParallelSPCleanupThreadClosure : public ThreadClosure {
531 private:
532 CodeBlobClosure* _nmethod_cl;
533 DeflateMonitorCounters* _counters;
534
535 public:
536 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
537 _counters(counters),
538 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
539
540 void do_thread(Thread* thread) {
541 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
542 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
543 ! thread->is_Code_cache_sweeper_thread()) {
544 JavaThread* jt = (JavaThread*) thread;
545 jt->nmethods_do(_nmethod_cl);
546 }
547 }
548 };
549
550 class ParallelSPCleanupTask : public AbstractGangTask {
551 private:
552 SubTasksDone _subtasks;
553 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
554 uint _num_workers;
555 DeflateMonitorCounters* _counters;
556 public:
557 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
558 AbstractGangTask("Parallel Safepoint Cleanup"),
559 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
560 _num_workers(num_workers),
561 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
562 _counters(counters) {}
563
564 void work(uint worker_id) {
565 // All threads deflate monitors and mark nmethods (if necessary).
566 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
567
568 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
569 const char* name = "deflating idle monitors";
570 EventSafepointCleanupTask event;
571 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
572 ObjectSynchronizer::deflate_idle_monitors(_counters);
573 event_safepoint_cleanup_task_commit(event, name);
574 }
575
576 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
577 const char* name = "updating inline caches";
578 EventSafepointCleanupTask event;
579 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
580 InlineCacheBuffer::update_inline_caches();
581 event_safepoint_cleanup_task_commit(event, name);
582 }
583
584 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
585 const char* name = "compilation policy safepoint handler";
586 EventSafepointCleanupTask event;
587 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
588 CompilationPolicy::policy()->do_safepoint_work();
589 event_safepoint_cleanup_task_commit(event, name);
590 }
591
592 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
593 if (SymbolTable::needs_rehashing()) {
594 const char* name = "rehashing symbol table";
595 EventSafepointCleanupTask event;
596 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
597 SymbolTable::rehash_table();
598 event_safepoint_cleanup_task_commit(event, name);
599 }
600 }
601
602 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
603 if (StringTable::needs_rehashing()) {
604 const char* name = "rehashing string table";
605 EventSafepointCleanupTask event;
606 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
607 StringTable::rehash_table();
608 event_safepoint_cleanup_task_commit(event, name);
609 }
610 }
611
612 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
613 // CMS delays purging the CLDG until the beginning of the next safepoint and to
614 // make sure concurrent sweep is done
615 const char* name = "purging class loader data graph";
616 EventSafepointCleanupTask event;
617 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
618 ClassLoaderDataGraph::purge_if_needed();
619 event_safepoint_cleanup_task_commit(event, name);
620 }
621 _subtasks.all_tasks_completed(_num_workers);
622 }
623 };
624
625 // Various cleaning tasks that should be done periodically at safepoints.
626 void SafepointSynchronize::do_cleanup_tasks() {
627
628 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
629
630 // Prepare for monitor deflation.
631 DeflateMonitorCounters deflate_counters;
632 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
633
634 CollectedHeap* heap = Universe::heap();
635 assert(heap != NULL, "heap not initialized yet?");
636 WorkGang* cleanup_workers = heap->get_safepoint_workers();
637 if (cleanup_workers != NULL) {
638 // Parallel cleanup using GC provided thread pool.
639 uint num_cleanup_workers = cleanup_workers->active_workers();
640 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
641 StrongRootsScope srs(num_cleanup_workers);
642 cleanup_workers->run_task(&cleanup);
643 } else {
644 // Serial cleanup using VMThread.
645 ParallelSPCleanupTask cleanup(1, &deflate_counters);
646 StrongRootsScope srs(1);
647 cleanup.work(0);
648 }
649
650 // Finish monitor deflation.
651 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
652 }
653
654
655 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
656 switch(state) {
657 case _thread_in_native:
658 // native threads are safe if they have no java stack or have walkable stack
659 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
660
661 // blocked threads should have already have walkable stack
662 case _thread_blocked:
663 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
664 return true;
665
666 default:
667 return false;
668 }
669 }
670
671
672 // See if the thread is running inside a lazy critical native and
673 // update the thread critical count if so. Also set a suspend flag to
674 // cause the native wrapper to return into the JVM to do the unlock
675 // once the native finishes.
676 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
677 if (state == _thread_in_native &&
678 thread->has_last_Java_frame() &&
679 thread->frame_anchor()->walkable()) {
680 // This thread might be in a critical native nmethod so look at
681 // the top of the stack and increment the critical count if it
682 // is.
683 frame wrapper_frame = thread->last_frame();
684 CodeBlob* stub_cb = wrapper_frame.cb();
685 if (stub_cb != NULL &&
686 stub_cb->is_nmethod() &&
687 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
688 // A thread could potentially be in a critical native across
689 // more than one safepoint, so only update the critical state on
690 // the first one. When it returns it will perform the unlock.
691 if (!thread->do_critical_native_unlock()) {
692 #ifdef ASSERT
693 if (!thread->in_critical()) {
694 GCLocker::increment_debug_jni_lock_count();
695 }
696 #endif
697 thread->enter_critical();
698 // Make sure the native wrapper calls back on return to
699 // perform the needed critical unlock.
700 thread->set_critical_native_unlock();
701 }
702 }
703 }
704 }
705
706
707
708 // -------------------------------------------------------------------------------------------------------
709 // Implementation of Safepoint callback point
710
711 void SafepointSynchronize::block(JavaThread *thread) {
712 assert(thread != NULL, "thread must be set");
713 assert(thread->is_Java_thread(), "not a Java thread");
714
715 // Threads shouldn't block if they are in the middle of printing, but...
716 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
717
718 // Only bail from the block() call if the thread is gone from the
719 // thread list; starting to exit should still block.
720 if (thread->is_terminated()) {
721 // block current thread if we come here from native code when VM is gone
722 thread->block_if_vm_exited();
723
724 // otherwise do nothing
725 return;
726 }
727
728 JavaThreadState state = thread->thread_state();
729 thread->frame_anchor()->make_walkable(thread);
730
731 // Check that we have a valid thread_state at this point
732 switch(state) {
733 case _thread_in_vm_trans:
734 case _thread_in_Java: // From compiled code
735
736 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
737 // we pretend we are still in the VM.
738 thread->set_thread_state(_thread_in_vm);
739
740 if (is_synchronizing()) {
741 Atomic::inc (&TryingToBlock) ;
742 }
743
744 // We will always be holding the Safepoint_lock when we are examine the state
745 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
746 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
747 Safepoint_lock->lock_without_safepoint_check();
748 if (is_synchronizing()) {
749 // Decrement the number of threads to wait for and signal vm thread
750 assert(_waiting_to_block > 0, "sanity check");
751 _waiting_to_block--;
752 thread->safepoint_state()->set_has_called_back(true);
753
754 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
755 if (thread->in_critical()) {
756 // Notice that this thread is in a critical section
757 increment_jni_active_count();
758 }
759
760 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
761 if (_waiting_to_block == 0) {
762 Safepoint_lock->notify_all();
763 }
764 }
765
766 // We transition the thread to state _thread_blocked here, but
767 // we can't do our usual check for external suspension and then
768 // self-suspend after the lock_without_safepoint_check() call
769 // below because we are often called during transitions while
770 // we hold different locks. That would leave us suspended while
771 // holding a resource which results in deadlocks.
772 thread->set_thread_state(_thread_blocked);
773 Safepoint_lock->unlock();
774
775 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
776 // the entire safepoint, the threads will all line up here during the safepoint.
777 Threads_lock->lock_without_safepoint_check();
778 // restore original state. This is important if the thread comes from compiled code, so it
779 // will continue to execute with the _thread_in_Java state.
780 thread->set_thread_state(state);
781 Threads_lock->unlock();
782 break;
783
784 case _thread_in_native_trans:
785 case _thread_blocked_trans:
786 case _thread_new_trans:
787 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
788 thread->print_thread_state();
789 fatal("Deadlock in safepoint code. "
790 "Should have called back to the VM before blocking.");
791 }
792
793 // We transition the thread to state _thread_blocked here, but
794 // we can't do our usual check for external suspension and then
795 // self-suspend after the lock_without_safepoint_check() call
796 // below because we are often called during transitions while
797 // we hold different locks. That would leave us suspended while
798 // holding a resource which results in deadlocks.
799 thread->set_thread_state(_thread_blocked);
800
801 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
802 // the safepoint code might still be waiting for it to block. We need to change the state here,
803 // so it can see that it is at a safepoint.
804
805 // Block until the safepoint operation is completed.
806 Threads_lock->lock_without_safepoint_check();
807
808 // Restore state
809 thread->set_thread_state(state);
810
811 Threads_lock->unlock();
812 break;
813
814 default:
815 fatal("Illegal threadstate encountered: %d", state);
816 }
817
818 // Check for pending. async. exceptions or suspends - except if the
819 // thread was blocked inside the VM. has_special_runtime_exit_condition()
820 // is called last since it grabs a lock and we only want to do that when
821 // we must.
822 //
823 // Note: we never deliver an async exception at a polling point as the
824 // compiler may not have an exception handler for it. The polling
825 // code will notice the async and deoptimize and the exception will
826 // be delivered. (Polling at a return point is ok though). Sure is
827 // a lot of bother for a deprecated feature...
828 //
829 // We don't deliver an async exception if the thread state is
830 // _thread_in_native_trans so JNI functions won't be called with
831 // a surprising pending exception. If the thread state is going back to java,
832 // async exception is checked in check_special_condition_for_native_trans().
833
834 if (state != _thread_blocked_trans &&
835 state != _thread_in_vm_trans &&
836 thread->has_special_runtime_exit_condition()) {
837 thread->handle_special_runtime_exit_condition(
838 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
839 }
840 }
841
842 // ------------------------------------------------------------------------------------------------------
843 // Exception handlers
844
845
846 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
847 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
848 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
849 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
850
851 if (ShowSafepointMsgs) {
852 tty->print("handle_polling_page_exception: ");
853 }
854
855 if (PrintSafepointStatistics) {
856 inc_page_trap_count();
857 }
858
859 ThreadSafepointState* state = thread->safepoint_state();
860
861 state->handle_polling_page_exception();
862 }
863
864
865 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
866 if (!timeout_error_printed) {
867 timeout_error_printed = true;
868 // Print out the thread info which didn't reach the safepoint for debugging
869 // purposes (useful when there are lots of threads in the debugger).
870 tty->cr();
871 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
872 if (reason == _spinning_timeout) {
873 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
874 } else if (reason == _blocking_timeout) {
875 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
876 }
877
878 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
879 ThreadSafepointState *cur_state;
880 ResourceMark rm;
881 for(JavaThread *cur_thread = Threads::first(); cur_thread;
882 cur_thread = cur_thread->next()) {
883 cur_state = cur_thread->safepoint_state();
884
885 if (cur_thread->thread_state() != _thread_blocked &&
886 ((reason == _spinning_timeout && cur_state->is_running()) ||
887 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
888 tty->print("# ");
889 cur_thread->print();
890 tty->cr();
891 }
892 }
893 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
894 }
895
896 // To debug the long safepoint, specify both DieOnSafepointTimeout &
897 // ShowMessageBoxOnError.
898 if (DieOnSafepointTimeout) {
899 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
900 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
901 }
902 }
903
904
905 // -------------------------------------------------------------------------------------------------------
906 // Implementation of ThreadSafepointState
907
908 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
909 _thread = thread;
910 _type = _running;
911 _has_called_back = false;
912 _at_poll_safepoint = false;
913 }
914
915 void ThreadSafepointState::create(JavaThread *thread) {
916 ThreadSafepointState *state = new ThreadSafepointState(thread);
917 thread->set_safepoint_state(state);
918 }
919
920 void ThreadSafepointState::destroy(JavaThread *thread) {
921 if (thread->safepoint_state()) {
922 delete(thread->safepoint_state());
923 thread->set_safepoint_state(NULL);
924 }
925 }
926
927 void ThreadSafepointState::examine_state_of_thread() {
928 assert(is_running(), "better be running or just have hit safepoint poll");
929
930 JavaThreadState state = _thread->thread_state();
931
932 // Save the state at the start of safepoint processing.
933 _orig_thread_state = state;
934
935 // Check for a thread that is suspended. Note that thread resume tries
936 // to grab the Threads_lock which we own here, so a thread cannot be
937 // resumed during safepoint synchronization.
938
939 // We check to see if this thread is suspended without locking to
940 // avoid deadlocking with a third thread that is waiting for this
941 // thread to be suspended. The third thread can notice the safepoint
942 // that we're trying to start at the beginning of its SR_lock->wait()
943 // call. If that happens, then the third thread will block on the
944 // safepoint while still holding the underlying SR_lock. We won't be
945 // able to get the SR_lock and we'll deadlock.
946 //
947 // We don't need to grab the SR_lock here for two reasons:
948 // 1) The suspend flags are both volatile and are set with an
949 // Atomic::cmpxchg() call so we should see the suspended
950 // state right away.
951 // 2) We're being called from the safepoint polling loop; if
952 // we don't see the suspended state on this iteration, then
953 // we'll come around again.
954 //
955 bool is_suspended = _thread->is_ext_suspended();
956 if (is_suspended) {
957 roll_forward(_at_safepoint);
958 return;
959 }
960
961 // Some JavaThread states have an initial safepoint state of
962 // running, but are actually at a safepoint. We will happily
963 // agree and update the safepoint state here.
964 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
965 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
966 roll_forward(_at_safepoint);
967 return;
968 }
969
970 if (state == _thread_in_vm) {
971 roll_forward(_call_back);
972 return;
973 }
974
975 // All other thread states will continue to run until they
976 // transition and self-block in state _blocked
977 // Safepoint polling in compiled code causes the Java threads to do the same.
978 // Note: new threads may require a malloc so they must be allowed to finish
979
980 assert(is_running(), "examine_state_of_thread on non-running thread");
981 return;
982 }
983
984 // Returns true is thread could not be rolled forward at present position.
985 void ThreadSafepointState::roll_forward(suspend_type type) {
986 _type = type;
987
988 switch(_type) {
989 case _at_safepoint:
990 SafepointSynchronize::signal_thread_at_safepoint();
991 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
992 if (_thread->in_critical()) {
993 // Notice that this thread is in a critical section
994 SafepointSynchronize::increment_jni_active_count();
995 }
996 break;
997
998 case _call_back:
999 set_has_called_back(false);
1000 break;
1001
1002 case _running:
1003 default:
1004 ShouldNotReachHere();
1005 }
1006 }
1007
1008 void ThreadSafepointState::restart() {
1009 switch(type()) {
1010 case _at_safepoint:
1011 case _call_back:
1012 break;
1013
1014 case _running:
1015 default:
1016 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1017 p2i(_thread), _type);
1018 _thread->print();
1019 ShouldNotReachHere();
1020 }
1021 _type = _running;
1022 set_has_called_back(false);
1023 }
1024
1025
1026 void ThreadSafepointState::print_on(outputStream *st) const {
1027 const char *s = NULL;
1028
1029 switch(_type) {
1030 case _running : s = "_running"; break;
1031 case _at_safepoint : s = "_at_safepoint"; break;
1032 case _call_back : s = "_call_back"; break;
1033 default:
1034 ShouldNotReachHere();
1035 }
1036
1037 st->print_cr("Thread: " INTPTR_FORMAT
1038 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1039 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1040 _at_poll_safepoint);
1041
1042 _thread->print_thread_state_on(st);
1043 }
1044
1045 // ---------------------------------------------------------------------------------------------------------------------
1046
1047 // Block the thread at the safepoint poll or poll return.
1048 void ThreadSafepointState::handle_polling_page_exception() {
1049
1050 // Check state. block() will set thread state to thread_in_vm which will
1051 // cause the safepoint state _type to become _call_back.
1052 assert(type() == ThreadSafepointState::_running,
1053 "polling page exception on thread not running state");
1054
1055 // Step 1: Find the nmethod from the return address
1056 if (ShowSafepointMsgs && Verbose) {
1057 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1058 }
1059 address real_return_addr = thread()->saved_exception_pc();
1060
1061 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1062 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1063 CompiledMethod* nm = (CompiledMethod*)cb;
1064
1065 // Find frame of caller
1066 frame stub_fr = thread()->last_frame();
1067 CodeBlob* stub_cb = stub_fr.cb();
1068 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1069 RegisterMap map(thread(), true);
1070 frame caller_fr = stub_fr.sender(&map);
1071
1072 // Should only be poll_return or poll
1073 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1074
1075 // This is a poll immediately before a return. The exception handling code
1076 // has already had the effect of causing the return to occur, so the execution
1077 // will continue immediately after the call. In addition, the oopmap at the
1078 // return point does not mark the return value as an oop (if it is), so
1079 // it needs a handle here to be updated.
1080 if( nm->is_at_poll_return(real_return_addr) ) {
1081 // See if return type is an oop.
1082 bool return_oop = nm->method()->is_returning_oop();
1083 Handle return_value;
1084 if (return_oop) {
1085 // The oop result has been saved on the stack together with all
1086 // the other registers. In order to preserve it over GCs we need
1087 // to keep it in a handle.
1088 oop result = caller_fr.saved_oop_result(&map);
1089 assert(oopDesc::is_oop_or_null(result), "must be oop");
1090 return_value = Handle(thread(), result);
1091 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1092 }
1093
1094 // Block the thread
1095 SafepointSynchronize::block(thread());
1096
1097 // restore oop result, if any
1098 if (return_oop) {
1099 caller_fr.set_saved_oop_result(&map, return_value());
1100 }
1101 }
1102
1103 // This is a safepoint poll. Verify the return address and block.
1104 else {
1105 set_at_poll_safepoint(true);
1106
1107 // verify the blob built the "return address" correctly
1108 assert(real_return_addr == caller_fr.pc(), "must match");
1109
1110 // Block the thread
1111 SafepointSynchronize::block(thread());
1112 set_at_poll_safepoint(false);
1113
1114 // If we have a pending async exception deoptimize the frame
1115 // as otherwise we may never deliver it.
1116 if (thread()->has_async_condition()) {
1117 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1118 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1119 }
1120
1121 // If an exception has been installed we must check for a pending deoptimization
1122 // Deoptimize frame if exception has been thrown.
1123
1124 if (thread()->has_pending_exception() ) {
1125 RegisterMap map(thread(), true);
1126 frame caller_fr = stub_fr.sender(&map);
1127 if (caller_fr.is_deoptimized_frame()) {
1128 // The exception patch will destroy registers that are still
1129 // live and will be needed during deoptimization. Defer the
1130 // Async exception should have deferred the exception until the
1131 // next safepoint which will be detected when we get into
1132 // the interpreter so if we have an exception now things
1133 // are messed up.
1134
1135 fatal("Exception installed and deoptimization is pending");
1136 }
1137 }
1138 }
1139 }
1140
1141
1142 //
1143 // Statistics & Instrumentations
1144 //
1145 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1146 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1147 int SafepointSynchronize::_cur_stat_index = 0;
1148 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1149 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1150 jlong SafepointSynchronize::_max_sync_time = 0;
1151 jlong SafepointSynchronize::_max_vmop_time = 0;
1152 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1153
1154 static jlong cleanup_end_time = 0;
1155 static bool need_to_track_page_armed_status = false;
1156 static bool init_done = false;
1157
1158 // Helper method to print the header.
1159 static void print_header() {
1160 // The number of spaces is significant here, and should match the format
1161 // specifiers in print_statistics().
1162
1163 tty->print(" vmop "
1164 "[ threads: total initially_running wait_to_block ]"
1165 "[ time: spin block sync cleanup vmop ] ");
1166
1167 // no page armed status printed out if it is always armed.
1168 if (need_to_track_page_armed_status) {
1169 tty->print("page_armed ");
1170 }
1171
1172 tty->print_cr("page_trap_count");
1173 }
1174
1175 void SafepointSynchronize::deferred_initialize_stat() {
1176 if (init_done) return;
1177
1178 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1179 // be printed right away, in which case, _safepoint_stats will regress to
1180 // a single element array. Otherwise, it is a circular ring buffer with default
1181 // size of PrintSafepointStatisticsCount.
1182 int stats_array_size;
1183 if (PrintSafepointStatisticsTimeout > 0) {
1184 stats_array_size = 1;
1185 PrintSafepointStatistics = true;
1186 } else {
1187 stats_array_size = PrintSafepointStatisticsCount;
1188 }
1189 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1190 * sizeof(SafepointStats), mtInternal);
1191 guarantee(_safepoint_stats != NULL,
1192 "not enough memory for safepoint instrumentation data");
1193
1194 if (DeferPollingPageLoopCount >= 0) {
1195 need_to_track_page_armed_status = true;
1196 }
1197 init_done = true;
1198 }
1199
1200 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1201 assert(init_done, "safepoint statistics array hasn't been initialized");
1202 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1203
1204 spstat->_time_stamp = _ts_of_current_safepoint;
1205
1206 VM_Operation *op = VMThread::vm_operation();
1207 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1208 if (op != NULL) {
1209 _safepoint_reasons[spstat->_vmop_type]++;
1210 }
1211
1212 spstat->_nof_total_threads = nof_threads;
1213 spstat->_nof_initial_running_threads = nof_running;
1214 spstat->_nof_threads_hit_page_trap = 0;
1215
1216 // Records the start time of spinning. The real time spent on spinning
1217 // will be adjusted when spin is done. Same trick is applied for time
1218 // spent on waiting for threads to block.
1219 if (nof_running != 0) {
1220 spstat->_time_to_spin = os::javaTimeNanos();
1221 } else {
1222 spstat->_time_to_spin = 0;
1223 }
1224 }
1225
1226 void SafepointSynchronize::update_statistics_on_spin_end() {
1227 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1228
1229 jlong cur_time = os::javaTimeNanos();
1230
1231 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1232 if (spstat->_nof_initial_running_threads != 0) {
1233 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1234 }
1235
1236 if (need_to_track_page_armed_status) {
1237 spstat->_page_armed = (PageArmed == 1);
1238 }
1239
1240 // Records the start time of waiting for to block. Updated when block is done.
1241 if (_waiting_to_block != 0) {
1242 spstat->_time_to_wait_to_block = cur_time;
1243 } else {
1244 spstat->_time_to_wait_to_block = 0;
1245 }
1246 }
1247
1248 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1249 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1250
1251 if (spstat->_nof_threads_wait_to_block != 0) {
1252 spstat->_time_to_wait_to_block = end_time -
1253 spstat->_time_to_wait_to_block;
1254 }
1255
1256 // Records the end time of sync which will be used to calculate the total
1257 // vm operation time. Again, the real time spending in syncing will be deducted
1258 // from the start of the sync time later when end_statistics is called.
1259 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1260 if (spstat->_time_to_sync > _max_sync_time) {
1261 _max_sync_time = spstat->_time_to_sync;
1262 }
1263
1264 spstat->_time_to_do_cleanups = end_time;
1265 }
1266
1267 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1268 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1269
1270 // Record how long spent in cleanup tasks.
1271 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1272
1273 cleanup_end_time = end_time;
1274 }
1275
1276 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1277 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1278
1279 // Update the vm operation time.
1280 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1281 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1282 _max_vmop_time = spstat->_time_to_exec_vmop;
1283 }
1284 // Only the sync time longer than the specified
1285 // PrintSafepointStatisticsTimeout will be printed out right away.
1286 // By default, it is -1 meaning all samples will be put into the list.
1287 if ( PrintSafepointStatisticsTimeout > 0) {
1288 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1289 print_statistics();
1290 }
1291 } else {
1292 // The safepoint statistics will be printed out when the _safepoin_stats
1293 // array fills up.
1294 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1295 print_statistics();
1296 _cur_stat_index = 0;
1297 } else {
1298 _cur_stat_index++;
1299 }
1300 }
1301 }
1302
1303 void SafepointSynchronize::print_statistics() {
1304 for (int index = 0; index <= _cur_stat_index; index++) {
1305 if (index % 30 == 0) {
1306 print_header();
1307 }
1308 SafepointStats* sstats = &_safepoint_stats[index];
1309 tty->print("%8.3f: ", sstats->_time_stamp);
1310 tty->print("%-30s [ "
1311 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1312 "]",
1313 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1314 sstats->_nof_total_threads,
1315 sstats->_nof_initial_running_threads,
1316 sstats->_nof_threads_wait_to_block);
1317 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1318 tty->print("[ "
1319 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1320 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1321 INT64_FORMAT_W(7) " ] ",
1322 (int64_t)(sstats->_time_to_spin / MICROUNITS),
1323 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
1324 (int64_t)(sstats->_time_to_sync / MICROUNITS),
1325 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
1326 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
1327
1328 if (need_to_track_page_armed_status) {
1329 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1330 }
1331 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1332 }
1333 }
1334
1335 // This method will be called when VM exits. It will first call
1336 // print_statistics to print out the rest of the sampling. Then
1337 // it tries to summarize the sampling.
1338 void SafepointSynchronize::print_stat_on_exit() {
1339 if (_safepoint_stats == NULL) return;
1340
1341 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1342
1343 // During VM exit, end_statistics may not get called and in that
1344 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1345 // don't print it out.
1346 // Approximate the vm op time.
1347 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1348 os::javaTimeNanos() - cleanup_end_time;
1349
1350 if ( PrintSafepointStatisticsTimeout < 0 ||
1351 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1352 print_statistics();
1353 }
1354 tty->cr();
1355
1356 // Print out polling page sampling status.
1357 if (!need_to_track_page_armed_status) {
1358 tty->print_cr("Polling page always armed");
1359 } else {
1360 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1361 DeferPollingPageLoopCount);
1362 }
1363
1364 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1365 if (_safepoint_reasons[index] != 0) {
1366 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1367 _safepoint_reasons[index]);
1368 }
1369 }
1370
1371 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1372 _coalesced_vmop_count);
1373 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1374 (int64_t)(_max_sync_time / MICROUNITS));
1375 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1376 INT64_FORMAT_W(5) " ms",
1377 (int64_t)(_max_vmop_time / MICROUNITS));
1378 }
1379
1380 // ------------------------------------------------------------------------------------------------
1381 // Non-product code
1382
1383 #ifndef PRODUCT
1384
1385 void SafepointSynchronize::print_state() {
1386 if (_state == _not_synchronized) {
1387 tty->print_cr("not synchronized");
1388 } else if (_state == _synchronizing || _state == _synchronized) {
1389 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1390 "synchronized");
1391
1392 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1393 cur->safepoint_state()->print();
1394 }
1395 }
1396 }
1397
1398 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1399 if (ShowSafepointMsgs) {
1400 va_list ap;
1401 va_start(ap, format);
1402 tty->vprint_cr(format, ap);
1403 va_end(ap);
1404 }
1405 }
1406
1407 #endif // !PRODUCT