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/classLoaderData.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/icBuffer.hpp"
32 #include "code/nmethod.hpp"
33 #include "code/pcDesc.hpp"
34 #include "code/scopeDesc.hpp"
35 #include "gc/shared/collectedHeap.hpp"
36 #include "gc/shared/gcLocker.inline.hpp"
37 #include "gc/shared/strongRootsScope.hpp"
38 #include "gc/shared/workgroup.hpp"
39 #include "interpreter/interpreter.hpp"
40 #include "logging/log.hpp"
41 #include "logging/logStream.hpp"
42 #include "memory/resourceArea.hpp"
43 #include "memory/universe.inline.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "oops/symbol.hpp"
46 #include "runtime/atomic.hpp"
47 #include "runtime/compilationPolicy.hpp"
48 #include "runtime/deoptimization.hpp"
49 #include "runtime/frame.inline.hpp"
50 #include "runtime/interfaceSupport.hpp"
51 #include "runtime/mutexLocker.hpp"
52 #include "runtime/orderAccess.inline.hpp"
53 #include "runtime/osThread.hpp"
54 #include "runtime/safepoint.hpp"
55 #include "runtime/signature.hpp"
56 #include "runtime/stubCodeGenerator.hpp"
57 #include "runtime/stubRoutines.hpp"
58 #include "runtime/sweeper.hpp"
59 #include "runtime/synchronizer.hpp"
60 #include "runtime/thread.inline.hpp"
61 #include "runtime/timerTrace.hpp"
62 #include "services/runtimeService.hpp"
63 #include "trace/tracing.hpp"
64 #include "trace/traceMacros.hpp"
65 #include "utilities/events.hpp"
66 #include "utilities/macros.hpp"
67 #ifdef COMPILER1
68 #include "c1/c1_globals.hpp"
69 #endif
70
71 // --------------------------------------------------------------------------------------------------
72 // Implementation of Safepoint begin/end
73
74 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
75 volatile int SafepointSynchronize::_waiting_to_block = 0;
76 volatile int SafepointSynchronize::_safepoint_counter = 0;
77 int SafepointSynchronize::_current_jni_active_count = 0;
78 long SafepointSynchronize::_end_of_last_safepoint = 0;
79 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
80 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
81 static bool timeout_error_printed = false;
82
83 // Roll all threads forward to a safepoint and suspend them all
84 void SafepointSynchronize::begin() {
85 EventSafepointBegin begin_event;
86 Thread* myThread = Thread::current();
87 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
88
89 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
90 _safepoint_begin_time = os::javaTimeNanos();
91 _ts_of_current_safepoint = tty->time_stamp().seconds();
92 }
93
94 Universe::heap()->safepoint_synchronize_begin();
95
96 // By getting the Threads_lock, we assure that no threads are about to start or
97 // exit. It is released again in SafepointSynchronize::end().
98 Threads_lock->lock();
99
100 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
101
102 int nof_threads = Threads::number_of_threads();
103
104 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
105
106 RuntimeService::record_safepoint_begin();
107
108 MutexLocker mu(Safepoint_lock);
109
110 // Reset the count of active JNI critical threads
111 _current_jni_active_count = 0;
112
113 // Set number of threads to wait for, before we initiate the callbacks
114 _waiting_to_block = nof_threads;
115 TryingToBlock = 0 ;
116 int still_running = nof_threads;
117
118 // Save the starting time, so that it can be compared to see if this has taken
119 // too long to complete.
120 jlong safepoint_limit_time = 0;
121 timeout_error_printed = false;
122
123 // PrintSafepointStatisticsTimeout can be specified separately. When
124 // specified, PrintSafepointStatistics will be set to true in
125 // deferred_initialize_stat method. The initialization has to be done
126 // early enough to avoid any races. See bug 6880029 for details.
127 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
128 deferred_initialize_stat();
129 }
130
131 // Begin the process of bringing the system to a safepoint.
132 // Java threads can be in several different states and are
133 // stopped by different mechanisms:
134 //
135 // 1. Running interpreted
136 // The interpreter dispatch table is changed to force it to
137 // check for a safepoint condition between bytecodes.
138 // 2. Running in native code
139 // When returning from the native code, a Java thread must check
140 // the safepoint _state to see if we must block. If the
141 // VM thread sees a Java thread in native, it does
142 // not wait for this thread to block. The order of the memory
143 // writes and reads of both the safepoint state and the Java
144 // threads state is critical. In order to guarantee that the
145 // memory writes are serialized with respect to each other,
146 // the VM thread issues a memory barrier instruction
147 // (on MP systems). In order to avoid the overhead of issuing
148 // a memory barrier for each Java thread making native calls, each Java
149 // thread performs a write to a single memory page after changing
150 // the thread state. The VM thread performs a sequence of
151 // mprotect OS calls which forces all previous writes from all
152 // Java threads to be serialized. This is done in the
153 // os::serialize_thread_states() call. This has proven to be
154 // much more efficient than executing a membar instruction
155 // on every call to native code.
156 // 3. Running compiled Code
157 // Compiled code reads a global (Safepoint Polling) page that
158 // is set to fault if we are trying to get to a safepoint.
159 // 4. Blocked
160 // A thread which is blocked will not be allowed to return from the
161 // block condition until the safepoint operation is complete.
162 // 5. In VM or Transitioning between states
163 // If a Java thread is currently running in the VM or transitioning
164 // between states, the safepointing code will wait for the thread to
165 // block itself when it attempts transitions to a new state.
166 //
167 {
168 EventSafepointStateSynchronization sync_event;
169 int initial_running = 0;
170
171 _state = _synchronizing;
172 OrderAccess::fence();
173
174 // Flush all thread states to memory
175 if (!UseMembar) {
176 os::serialize_thread_states();
177 }
178
179 // Make interpreter safepoint aware
180 Interpreter::notice_safepoints();
181
182 if (DeferPollingPageLoopCount < 0) {
183 // Make polling safepoint aware
184 guarantee (PageArmed == 0, "invariant") ;
185 PageArmed = 1 ;
186 os::make_polling_page_unreadable();
187 }
188
189 // Consider using active_processor_count() ... but that call is expensive.
190 int ncpus = os::processor_count() ;
191
192 #ifdef ASSERT
193 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
194 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
195 // Clear the visited flag to ensure that the critical counts are collected properly.
196 cur->set_visited_for_critical_count(false);
197 }
198 #endif // ASSERT
199
200 if (SafepointTimeout)
201 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
202
203 // Iterate through all threads until it have been determined how to stop them all at a safepoint
204 unsigned int iterations = 0;
205 int steps = 0 ;
206 while(still_running > 0) {
207 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
208 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
209 ThreadSafepointState *cur_state = cur->safepoint_state();
210 if (cur_state->is_running()) {
211 cur_state->examine_state_of_thread();
212 if (!cur_state->is_running()) {
213 still_running--;
214 // consider adjusting steps downward:
215 // steps = 0
216 // steps -= NNN
217 // steps >>= 1
218 // steps = MIN(steps, 2000-100)
219 // if (iterations != 0) steps -= NNN
220 }
221 LogTarget(Trace, safepoint) lt;
222 if (lt.is_enabled()) {
223 ResourceMark rm;
224 LogStream ls(lt);
225 cur_state->print_on(&ls);
226 }
227 }
228 }
229
230 if (iterations == 0) {
231 initial_running = still_running;
232 if (PrintSafepointStatistics) {
233 begin_statistics(nof_threads, still_running);
234 }
235 }
236
237 if (still_running > 0) {
238 // Check for if it takes to long
239 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
240 print_safepoint_timeout(_spinning_timeout);
241 }
242
243 // Spin to avoid context switching.
244 // There's a tension between allowing the mutators to run (and rendezvous)
245 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
246 // a mutator might otherwise use profitably to reach a safepoint. Excessive
247 // spinning by the VM thread on a saturated system can increase rendezvous latency.
248 // Blocking or yielding incur their own penalties in the form of context switching
249 // and the resultant loss of $ residency.
250 //
251 // Further complicating matters is that yield() does not work as naively expected
252 // on many platforms -- yield() does not guarantee that any other ready threads
253 // will run. As such we revert to naked_short_sleep() after some number of iterations.
254 // nakes_short_sleep() is implemented as a short unconditional sleep.
255 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
256 // can actually increase the time it takes the VM thread to detect that a system-wide
257 // stop-the-world safepoint has been reached. In a pathological scenario such as that
258 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
259 // In that case the mutators will be stalled waiting for the safepoint to complete and the
260 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
261 // will eventually wake up and detect that all mutators are safe, at which point
262 // we'll again make progress.
263 //
264 // Beware too that that the VMThread typically runs at elevated priority.
265 // Its default priority is higher than the default mutator priority.
266 // Obviously, this complicates spinning.
267 //
268 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
269 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
270 //
271 // See the comments in synchronizer.cpp for additional remarks on spinning.
272 //
273 // In the future we might:
274 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
275 // This is tricky as the path used by a thread exiting the JVM (say on
276 // on JNI call-out) simply stores into its state field. The burden
277 // is placed on the VM thread, which must poll (spin).
278 // 2. Find something useful to do while spinning. If the safepoint is GC-related
279 // we might aggressively scan the stacks of threads that are already safe.
280 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
281 // If all the mutators are ONPROC there's no reason to sleep or yield.
282 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
283 // 5. Check system saturation. If the system is not fully saturated then
284 // simply spin and avoid sleep/yield.
285 // 6. As still-running mutators rendezvous they could unpark the sleeping
286 // VMthread. This works well for still-running mutators that become
287 // safe. The VMthread must still poll for mutators that call-out.
288 // 7. Drive the policy on time-since-begin instead of iterations.
289 // 8. Consider making the spin duration a function of the # of CPUs:
290 // Spin = (((ncpus-1) * M) + K) + F(still_running)
291 // Alternately, instead of counting iterations of the outer loop
292 // we could count the # of threads visited in the inner loop, above.
293 // 9. On windows consider using the return value from SwitchThreadTo()
294 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
295
296 if (int(iterations) == DeferPollingPageLoopCount) {
297 guarantee (PageArmed == 0, "invariant") ;
298 PageArmed = 1 ;
299 os::make_polling_page_unreadable();
300 }
301
302 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
303 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
304 ++steps ;
305 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
306 SpinPause() ; // MP-Polite spin
307 } else
308 if (steps < DeferThrSuspendLoopCount) {
309 os::naked_yield() ;
310 } else {
311 os::naked_short_sleep(1);
312 }
313
314 iterations ++ ;
315 }
316 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
317 }
318 assert(still_running == 0, "sanity check");
319
320 if (PrintSafepointStatistics) {
321 update_statistics_on_spin_end();
322 }
323
324 if (sync_event.should_commit()) {
325 // Group this event together with the ones committed after the counter is increased
326 sync_event.set_safepointId(safepoint_counter() + 1);
327 sync_event.set_initialThreadCount(initial_running);
328 sync_event.set_runningThreadCount(_waiting_to_block);
329 sync_event.set_iterations(iterations);
330 sync_event.commit();
331 }
332 } //EventSafepointStateSync
333
334 // wait until all threads are stopped
335 {
336 EventSafepointWaitBlocked wait_blocked_event;
337 int initial_waiting_to_block = _waiting_to_block;
338
339 while (_waiting_to_block > 0) {
340 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
341 if (!SafepointTimeout || timeout_error_printed) {
342 Safepoint_lock->wait(true); // true, means with no safepoint checks
343 } else {
344 // Compute remaining time
345 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
346
347 // If there is no remaining time, then there is an error
348 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
349 print_safepoint_timeout(_blocking_timeout);
350 }
351 }
352 }
353 assert(_waiting_to_block == 0, "sanity check");
354
355 #ifndef PRODUCT
356 if (SafepointTimeout) {
357 jlong current_time = os::javaTimeNanos();
358 if (safepoint_limit_time < current_time) {
359 tty->print_cr("# SafepointSynchronize: Finished after "
360 INT64_FORMAT_W(6) " ms",
361 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
362 (jlong)SafepointTimeoutDelay));
363 }
364 }
365 #endif
366
367 assert((_safepoint_counter & 0x1) == 0, "must be even");
368 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
369 _safepoint_counter ++;
370
371 // Record state
372 _state = _synchronized;
373
374 OrderAccess::fence();
375
376 if (wait_blocked_event.should_commit()) {
377 wait_blocked_event.set_safepointId(safepoint_counter());
378 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
379 wait_blocked_event.commit();
380 }
381 } // EventSafepointWaitBlocked
382
383 #ifdef ASSERT
384 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
385 // make sure all the threads were visited
386 assert(cur->was_visited_for_critical_count(), "missed a thread");
387 }
388 #endif // ASSERT
389
390 // Update the count of active JNI critical regions
391 GCLocker::set_jni_lock_count(_current_jni_active_count);
392
393 if (log_is_enabled(Debug, safepoint)) {
394 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
395 }
396
397 RuntimeService::record_safepoint_synchronized();
398 if (PrintSafepointStatistics) {
399 update_statistics_on_sync_end(os::javaTimeNanos());
400 }
401
402 // Call stuff that needs to be run when a safepoint is just about to be completed
403 {
404 EventSafepointCleanup cleanup_event;
405 do_cleanup_tasks();
406 if (cleanup_event.should_commit()) {
407 cleanup_event.set_safepointId(safepoint_counter());
408 cleanup_event.commit();
409 }
410 }
411
412 if (PrintSafepointStatistics) {
413 // Record how much time spend on the above cleanup tasks
414 update_statistics_on_cleanup_end(os::javaTimeNanos());
415 }
416 if (begin_event.should_commit()) {
417 begin_event.set_safepointId(safepoint_counter());
418 begin_event.set_totalThreadCount(nof_threads);
419 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
420 begin_event.commit();
421 }
422 }
423
424 // Wake up all threads, so they are ready to resume execution after the safepoint
425 // operation has been carried out
426 void SafepointSynchronize::end() {
427 EventSafepointEnd event;
428 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
429
430 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
431 assert((_safepoint_counter & 0x1) == 1, "must be odd");
432 _safepoint_counter ++;
433 // memory fence isn't required here since an odd _safepoint_counter
434 // value can do no harm and a fence is issued below anyway.
435
436 DEBUG_ONLY(Thread* myThread = Thread::current();)
437 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
438
439 if (PrintSafepointStatistics) {
440 end_statistics(os::javaTimeNanos());
441 }
442
443 #ifdef ASSERT
444 // A pending_exception cannot be installed during a safepoint. The threads
445 // may install an async exception after they come back from a safepoint into
446 // pending_exception after they unblock. But that should happen later.
447 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
448 assert (!(cur->has_pending_exception() &&
449 cur->safepoint_state()->is_at_poll_safepoint()),
450 "safepoint installed a pending exception");
451 }
452 #endif // ASSERT
453
454 if (PageArmed) {
455 // Make polling safepoint aware
456 os::make_polling_page_readable();
457 PageArmed = 0 ;
458 }
459
460 // Remove safepoint check from interpreter
461 Interpreter::ignore_safepoints();
462
463 {
464 MutexLocker mu(Safepoint_lock);
465
466 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
467
468 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
469 // when they get restarted.
470 _state = _not_synchronized;
471 OrderAccess::fence();
472
473 log_debug(safepoint)("Leaving safepoint region");
474
475 // Start suspended threads
476 for(JavaThread *current = Threads::first(); current; current = current->next()) {
477 // A problem occurring on Solaris is when attempting to restart threads
478 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
479 // to the next one (since it has been running the longest). We then have
480 // to wait for a cpu to become available before we can continue restarting
481 // threads.
482 // FIXME: This causes the performance of the VM to degrade when active and with
483 // large numbers of threads. Apparently this is due to the synchronous nature
484 // of suspending threads.
485 //
486 // TODO-FIXME: the comments above are vestigial and no longer apply.
487 // Furthermore, using solaris' schedctl in this particular context confers no benefit
488 if (VMThreadHintNoPreempt) {
489 os::hint_no_preempt();
490 }
491 ThreadSafepointState* cur_state = current->safepoint_state();
492 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
493 cur_state->restart();
494 assert(cur_state->is_running(), "safepoint state has not been reset");
495 }
496
497 RuntimeService::record_safepoint_end();
498
499 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
500 // blocked in signal_thread_blocked
501 Threads_lock->unlock();
502
503 }
504 Universe::heap()->safepoint_synchronize_end();
505 // record this time so VMThread can keep track how much time has elapsed
506 // since last safepoint.
507 _end_of_last_safepoint = os::javaTimeMillis();
508
509 if (event.should_commit()) {
510 event.set_safepointId(safepoint_id);
511 event.commit();
512 }
513 }
514
515 bool SafepointSynchronize::is_cleanup_needed() {
516 // Need a safepoint if there are many monitors to deflate.
517 if (ObjectSynchronizer::is_cleanup_needed()) return true;
518 // Need a safepoint if some inline cache buffers is non-empty
519 if (!InlineCacheBuffer::is_empty()) return true;
520 return false;
521 }
522
523 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
524 if (event.should_commit()) {
525 event.set_safepointId(SafepointSynchronize::safepoint_counter());
526 event.set_name(name);
527 event.commit();
528 }
529 }
530
531 class ParallelSPCleanupThreadClosure : public ThreadClosure {
532 private:
533 CodeBlobClosure* _nmethod_cl;
534 DeflateMonitorCounters* _counters;
535
536 public:
537 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
538 _counters(counters),
539 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
540
541 void do_thread(Thread* thread) {
542 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
543 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
544 ! thread->is_Code_cache_sweeper_thread()) {
545 JavaThread* jt = (JavaThread*) thread;
546 jt->nmethods_do(_nmethod_cl);
547 }
548 }
549 };
550
551 class ParallelSPCleanupTask : public AbstractGangTask {
552 private:
553 SubTasksDone _subtasks;
554 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
555 uint _num_workers;
556 DeflateMonitorCounters* _counters;
557 public:
558 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
559 AbstractGangTask("Parallel Safepoint Cleanup"),
560 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
561 _num_workers(num_workers),
562 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
563 _counters(counters) {}
564
565 void work(uint worker_id) {
566 // All threads deflate monitors and mark nmethods (if necessary).
567 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
568
569 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
570 const char* name = "deflating idle monitors";
571 EventSafepointCleanupTask event;
572 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
573 ObjectSynchronizer::deflate_idle_monitors(_counters);
574 event_safepoint_cleanup_task_commit(event, name);
575 }
576
577 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
578 const char* name = "updating inline caches";
579 EventSafepointCleanupTask event;
580 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
581 InlineCacheBuffer::update_inline_caches();
582 event_safepoint_cleanup_task_commit(event, name);
583 }
584
585 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
586 const char* name = "compilation policy safepoint handler";
587 EventSafepointCleanupTask event;
588 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
589 CompilationPolicy::policy()->do_safepoint_work();
590 event_safepoint_cleanup_task_commit(event, name);
591 }
592
593 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
594 if (SymbolTable::needs_rehashing()) {
595 const char* name = "rehashing symbol table";
596 EventSafepointCleanupTask event;
597 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
598 SymbolTable::rehash_table();
599 event_safepoint_cleanup_task_commit(event, name);
600 }
601 }
602
603 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
604 if (StringTable::needs_rehashing()) {
605 const char* name = "rehashing string table";
606 EventSafepointCleanupTask event;
607 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
608 StringTable::rehash_table();
609 event_safepoint_cleanup_task_commit(event, name);
610 }
611 }
612
613 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
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 timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
619 ClassLoaderDataGraph::purge_if_needed();
620 event_safepoint_cleanup_task_commit(event, name);
621 }
622
623 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
624 const char* name = "resizing system dictionaries";
625 EventSafepointCleanupTask event;
626 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
627 ClassLoaderDataGraph::resize_if_needed();
628 event_safepoint_cleanup_task_commit(event, name);
629 }
630 _subtasks.all_tasks_completed(_num_workers);
631 }
632 };
633
634 // Various cleaning tasks that should be done periodically at safepoints.
635 void SafepointSynchronize::do_cleanup_tasks() {
636
637 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
638
639 // Prepare for monitor deflation.
640 DeflateMonitorCounters deflate_counters;
641 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
642
643 CollectedHeap* heap = Universe::heap();
644 assert(heap != NULL, "heap not initialized yet?");
645 WorkGang* cleanup_workers = heap->get_safepoint_workers();
646 if (cleanup_workers != NULL) {
647 // Parallel cleanup using GC provided thread pool.
648 uint num_cleanup_workers = cleanup_workers->active_workers();
649 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
650 StrongRootsScope srs(num_cleanup_workers);
651 cleanup_workers->run_task(&cleanup);
652 } else {
653 // Serial cleanup using VMThread.
654 ParallelSPCleanupTask cleanup(1, &deflate_counters);
655 StrongRootsScope srs(1);
656 cleanup.work(0);
657 }
658
659 // Finish monitor deflation.
660 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
661 }
662
663
664 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
665 switch(state) {
666 case _thread_in_native:
667 // native threads are safe if they have no java stack or have walkable stack
668 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
669
670 // blocked threads should have already have walkable stack
671 case _thread_blocked:
672 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
673 return true;
674
675 default:
676 return false;
677 }
678 }
679
680
681 // See if the thread is running inside a lazy critical native and
682 // update the thread critical count if so. Also set a suspend flag to
683 // cause the native wrapper to return into the JVM to do the unlock
684 // once the native finishes.
685 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
686 if (state == _thread_in_native &&
687 thread->has_last_Java_frame() &&
688 thread->frame_anchor()->walkable()) {
689 // This thread might be in a critical native nmethod so look at
690 // the top of the stack and increment the critical count if it
691 // is.
692 frame wrapper_frame = thread->last_frame();
693 CodeBlob* stub_cb = wrapper_frame.cb();
694 if (stub_cb != NULL &&
695 stub_cb->is_nmethod() &&
696 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
697 // A thread could potentially be in a critical native across
698 // more than one safepoint, so only update the critical state on
699 // the first one. When it returns it will perform the unlock.
700 if (!thread->do_critical_native_unlock()) {
701 #ifdef ASSERT
702 if (!thread->in_critical()) {
703 GCLocker::increment_debug_jni_lock_count();
704 }
705 #endif
706 thread->enter_critical();
707 // Make sure the native wrapper calls back on return to
708 // perform the needed critical unlock.
709 thread->set_critical_native_unlock();
710 }
711 }
712 }
713 }
714
715
716
717 // -------------------------------------------------------------------------------------------------------
718 // Implementation of Safepoint callback point
719
720 void SafepointSynchronize::block(JavaThread *thread) {
721 assert(thread != NULL, "thread must be set");
722 assert(thread->is_Java_thread(), "not a Java thread");
723
724 // Threads shouldn't block if they are in the middle of printing, but...
725 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
726
727 // Only bail from the block() call if the thread is gone from the
728 // thread list; starting to exit should still block.
729 if (thread->is_terminated()) {
730 // block current thread if we come here from native code when VM is gone
731 thread->block_if_vm_exited();
732
733 // otherwise do nothing
734 return;
735 }
736
737 JavaThreadState state = thread->thread_state();
738 thread->frame_anchor()->make_walkable(thread);
739
740 // Check that we have a valid thread_state at this point
741 switch(state) {
742 case _thread_in_vm_trans:
743 case _thread_in_Java: // From compiled code
744
745 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
746 // we pretend we are still in the VM.
747 thread->set_thread_state(_thread_in_vm);
748
749 if (is_synchronizing()) {
750 Atomic::inc (&TryingToBlock) ;
751 }
752
753 // We will always be holding the Safepoint_lock when we are examine the state
754 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
755 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
756 Safepoint_lock->lock_without_safepoint_check();
757 if (is_synchronizing()) {
758 // Decrement the number of threads to wait for and signal vm thread
759 assert(_waiting_to_block > 0, "sanity check");
760 _waiting_to_block--;
761 thread->safepoint_state()->set_has_called_back(true);
762
763 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
764 if (thread->in_critical()) {
765 // Notice that this thread is in a critical section
766 increment_jni_active_count();
767 }
768
769 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
770 if (_waiting_to_block == 0) {
771 Safepoint_lock->notify_all();
772 }
773 }
774
775 // We transition the thread to state _thread_blocked here, but
776 // we can't do our usual check for external suspension and then
777 // self-suspend after the lock_without_safepoint_check() call
778 // below because we are often called during transitions while
779 // we hold different locks. That would leave us suspended while
780 // holding a resource which results in deadlocks.
781 thread->set_thread_state(_thread_blocked);
782 Safepoint_lock->unlock();
783
784 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
785 // the entire safepoint, the threads will all line up here during the safepoint.
786 Threads_lock->lock_without_safepoint_check();
787 // restore original state. This is important if the thread comes from compiled code, so it
788 // will continue to execute with the _thread_in_Java state.
789 thread->set_thread_state(state);
790 Threads_lock->unlock();
791 break;
792
793 case _thread_in_native_trans:
794 case _thread_blocked_trans:
795 case _thread_new_trans:
796 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
797 thread->print_thread_state();
798 fatal("Deadlock in safepoint code. "
799 "Should have called back to the VM before blocking.");
800 }
801
802 // We transition the thread to state _thread_blocked here, but
803 // we can't do our usual check for external suspension and then
804 // self-suspend after the lock_without_safepoint_check() call
805 // below because we are often called during transitions while
806 // we hold different locks. That would leave us suspended while
807 // holding a resource which results in deadlocks.
808 thread->set_thread_state(_thread_blocked);
809
810 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
811 // the safepoint code might still be waiting for it to block. We need to change the state here,
812 // so it can see that it is at a safepoint.
813
814 // Block until the safepoint operation is completed.
815 Threads_lock->lock_without_safepoint_check();
816
817 // Restore state
818 thread->set_thread_state(state);
819
820 Threads_lock->unlock();
821 break;
822
823 default:
824 fatal("Illegal threadstate encountered: %d", state);
825 }
826
827 // Check for pending. async. exceptions or suspends - except if the
828 // thread was blocked inside the VM. has_special_runtime_exit_condition()
829 // is called last since it grabs a lock and we only want to do that when
830 // we must.
831 //
832 // Note: we never deliver an async exception at a polling point as the
833 // compiler may not have an exception handler for it. The polling
834 // code will notice the async and deoptimize and the exception will
835 // be delivered. (Polling at a return point is ok though). Sure is
836 // a lot of bother for a deprecated feature...
837 //
838 // We don't deliver an async exception if the thread state is
839 // _thread_in_native_trans so JNI functions won't be called with
840 // a surprising pending exception. If the thread state is going back to java,
841 // async exception is checked in check_special_condition_for_native_trans().
842
843 if (state != _thread_blocked_trans &&
844 state != _thread_in_vm_trans &&
845 thread->has_special_runtime_exit_condition()) {
846 thread->handle_special_runtime_exit_condition(
847 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
848 }
849 }
850
851 // ------------------------------------------------------------------------------------------------------
852 // Exception handlers
853
854
855 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
856 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
857 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
858 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
859
860 if (ShowSafepointMsgs) {
861 tty->print("handle_polling_page_exception: ");
862 }
863
864 if (PrintSafepointStatistics) {
865 inc_page_trap_count();
866 }
867
868 ThreadSafepointState* state = thread->safepoint_state();
869
870 state->handle_polling_page_exception();
871 }
872
873
874 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
875 if (!timeout_error_printed) {
876 timeout_error_printed = true;
877 // Print out the thread info which didn't reach the safepoint for debugging
878 // purposes (useful when there are lots of threads in the debugger).
879 tty->cr();
880 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
881 if (reason == _spinning_timeout) {
882 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
883 } else if (reason == _blocking_timeout) {
884 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
885 }
886
887 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
888 ThreadSafepointState *cur_state;
889 ResourceMark rm;
890 for(JavaThread *cur_thread = Threads::first(); cur_thread;
891 cur_thread = cur_thread->next()) {
892 cur_state = cur_thread->safepoint_state();
893
894 if (cur_thread->thread_state() != _thread_blocked &&
895 ((reason == _spinning_timeout && cur_state->is_running()) ||
896 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
897 tty->print("# ");
898 cur_thread->print();
899 tty->cr();
900 }
901 }
902 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
903 }
904
905 // To debug the long safepoint, specify both DieOnSafepointTimeout &
906 // ShowMessageBoxOnError.
907 if (DieOnSafepointTimeout) {
908 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
909 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
910 }
911 }
912
913
914 // -------------------------------------------------------------------------------------------------------
915 // Implementation of ThreadSafepointState
916
917 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
918 _thread = thread;
919 _type = _running;
920 _has_called_back = false;
921 _at_poll_safepoint = false;
922 }
923
924 void ThreadSafepointState::create(JavaThread *thread) {
925 ThreadSafepointState *state = new ThreadSafepointState(thread);
926 thread->set_safepoint_state(state);
927 }
928
929 void ThreadSafepointState::destroy(JavaThread *thread) {
930 if (thread->safepoint_state()) {
931 delete(thread->safepoint_state());
932 thread->set_safepoint_state(NULL);
933 }
934 }
935
936 void ThreadSafepointState::examine_state_of_thread() {
937 assert(is_running(), "better be running or just have hit safepoint poll");
938
939 JavaThreadState state = _thread->thread_state();
940
941 // Save the state at the start of safepoint processing.
942 _orig_thread_state = state;
943
944 // Check for a thread that is suspended. Note that thread resume tries
945 // to grab the Threads_lock which we own here, so a thread cannot be
946 // resumed during safepoint synchronization.
947
948 // We check to see if this thread is suspended without locking to
949 // avoid deadlocking with a third thread that is waiting for this
950 // thread to be suspended. The third thread can notice the safepoint
951 // that we're trying to start at the beginning of its SR_lock->wait()
952 // call. If that happens, then the third thread will block on the
953 // safepoint while still holding the underlying SR_lock. We won't be
954 // able to get the SR_lock and we'll deadlock.
955 //
956 // We don't need to grab the SR_lock here for two reasons:
957 // 1) The suspend flags are both volatile and are set with an
958 // Atomic::cmpxchg() call so we should see the suspended
959 // state right away.
960 // 2) We're being called from the safepoint polling loop; if
961 // we don't see the suspended state on this iteration, then
962 // we'll come around again.
963 //
964 bool is_suspended = _thread->is_ext_suspended();
965 if (is_suspended) {
966 roll_forward(_at_safepoint);
967 return;
968 }
969
970 // Some JavaThread states have an initial safepoint state of
971 // running, but are actually at a safepoint. We will happily
972 // agree and update the safepoint state here.
973 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
974 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
975 roll_forward(_at_safepoint);
976 return;
977 }
978
979 if (state == _thread_in_vm) {
980 roll_forward(_call_back);
981 return;
982 }
983
984 // All other thread states will continue to run until they
985 // transition and self-block in state _blocked
986 // Safepoint polling in compiled code causes the Java threads to do the same.
987 // Note: new threads may require a malloc so they must be allowed to finish
988
989 assert(is_running(), "examine_state_of_thread on non-running thread");
990 return;
991 }
992
993 // Returns true is thread could not be rolled forward at present position.
994 void ThreadSafepointState::roll_forward(suspend_type type) {
995 _type = type;
996
997 switch(_type) {
998 case _at_safepoint:
999 SafepointSynchronize::signal_thread_at_safepoint();
1000 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1001 if (_thread->in_critical()) {
1002 // Notice that this thread is in a critical section
1003 SafepointSynchronize::increment_jni_active_count();
1004 }
1005 break;
1006
1007 case _call_back:
1008 set_has_called_back(false);
1009 break;
1010
1011 case _running:
1012 default:
1013 ShouldNotReachHere();
1014 }
1015 }
1016
1017 void ThreadSafepointState::restart() {
1018 switch(type()) {
1019 case _at_safepoint:
1020 case _call_back:
1021 break;
1022
1023 case _running:
1024 default:
1025 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1026 p2i(_thread), _type);
1027 _thread->print();
1028 ShouldNotReachHere();
1029 }
1030 _type = _running;
1031 set_has_called_back(false);
1032 }
1033
1034
1035 void ThreadSafepointState::print_on(outputStream *st) const {
1036 const char *s = NULL;
1037
1038 switch(_type) {
1039 case _running : s = "_running"; break;
1040 case _at_safepoint : s = "_at_safepoint"; break;
1041 case _call_back : s = "_call_back"; break;
1042 default:
1043 ShouldNotReachHere();
1044 }
1045
1046 st->print_cr("Thread: " INTPTR_FORMAT
1047 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1048 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
1049 _at_poll_safepoint);
1050
1051 _thread->print_thread_state_on(st);
1052 }
1053
1054 // ---------------------------------------------------------------------------------------------------------------------
1055
1056 // Block the thread at the safepoint poll or poll return.
1057 void ThreadSafepointState::handle_polling_page_exception() {
1058
1059 // Check state. block() will set thread state to thread_in_vm which will
1060 // cause the safepoint state _type to become _call_back.
1061 assert(type() == ThreadSafepointState::_running,
1062 "polling page exception on thread not running state");
1063
1064 // Step 1: Find the nmethod from the return address
1065 if (ShowSafepointMsgs && Verbose) {
1066 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
1067 }
1068 address real_return_addr = thread()->saved_exception_pc();
1069
1070 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1071 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
1072 CompiledMethod* nm = (CompiledMethod*)cb;
1073
1074 // Find frame of caller
1075 frame stub_fr = thread()->last_frame();
1076 CodeBlob* stub_cb = stub_fr.cb();
1077 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1078 RegisterMap map(thread(), true);
1079 frame caller_fr = stub_fr.sender(&map);
1080
1081 // Should only be poll_return or poll
1082 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1083
1084 // This is a poll immediately before a return. The exception handling code
1085 // has already had the effect of causing the return to occur, so the execution
1086 // will continue immediately after the call. In addition, the oopmap at the
1087 // return point does not mark the return value as an oop (if it is), so
1088 // it needs a handle here to be updated.
1089 if( nm->is_at_poll_return(real_return_addr) ) {
1090 // See if return type is an oop.
1091 bool return_oop = nm->method()->is_returning_oop();
1092 Handle return_value;
1093 if (return_oop) {
1094 // The oop result has been saved on the stack together with all
1095 // the other registers. In order to preserve it over GCs we need
1096 // to keep it in a handle.
1097 oop result = caller_fr.saved_oop_result(&map);
1098 assert(oopDesc::is_oop_or_null(result), "must be oop");
1099 return_value = Handle(thread(), result);
1100 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1101 }
1102
1103 // Block the thread
1104 SafepointSynchronize::block(thread());
1105
1106 // restore oop result, if any
1107 if (return_oop) {
1108 caller_fr.set_saved_oop_result(&map, return_value());
1109 }
1110 }
1111
1112 // This is a safepoint poll. Verify the return address and block.
1113 else {
1114 set_at_poll_safepoint(true);
1115
1116 // verify the blob built the "return address" correctly
1117 assert(real_return_addr == caller_fr.pc(), "must match");
1118
1119 // Block the thread
1120 SafepointSynchronize::block(thread());
1121 set_at_poll_safepoint(false);
1122
1123 // If we have a pending async exception deoptimize the frame
1124 // as otherwise we may never deliver it.
1125 if (thread()->has_async_condition()) {
1126 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1127 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1128 }
1129
1130 // If an exception has been installed we must check for a pending deoptimization
1131 // Deoptimize frame if exception has been thrown.
1132
1133 if (thread()->has_pending_exception() ) {
1134 RegisterMap map(thread(), true);
1135 frame caller_fr = stub_fr.sender(&map);
1136 if (caller_fr.is_deoptimized_frame()) {
1137 // The exception patch will destroy registers that are still
1138 // live and will be needed during deoptimization. Defer the
1139 // Async exception should have deferred the exception until the
1140 // next safepoint which will be detected when we get into
1141 // the interpreter so if we have an exception now things
1142 // are messed up.
1143
1144 fatal("Exception installed and deoptimization is pending");
1145 }
1146 }
1147 }
1148 }
1149
1150
1151 //
1152 // Statistics & Instrumentations
1153 //
1154 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1155 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1156 int SafepointSynchronize::_cur_stat_index = 0;
1157 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1158 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1159 jlong SafepointSynchronize::_max_sync_time = 0;
1160 jlong SafepointSynchronize::_max_vmop_time = 0;
1161 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1162
1163 static jlong cleanup_end_time = 0;
1164 static bool need_to_track_page_armed_status = false;
1165 static bool init_done = false;
1166
1167 // Helper method to print the header.
1168 static void print_header() {
1169 // The number of spaces is significant here, and should match the format
1170 // specifiers in print_statistics().
1171
1172 tty->print(" vmop "
1173 "[ threads: total initially_running wait_to_block ]"
1174 "[ time: spin block sync cleanup vmop ] ");
1175
1176 // no page armed status printed out if it is always armed.
1177 if (need_to_track_page_armed_status) {
1178 tty->print("page_armed ");
1179 }
1180
1181 tty->print_cr("page_trap_count");
1182 }
1183
1184 void SafepointSynchronize::deferred_initialize_stat() {
1185 if (init_done) return;
1186
1187 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1188 // be printed right away, in which case, _safepoint_stats will regress to
1189 // a single element array. Otherwise, it is a circular ring buffer with default
1190 // size of PrintSafepointStatisticsCount.
1191 int stats_array_size;
1192 if (PrintSafepointStatisticsTimeout > 0) {
1193 stats_array_size = 1;
1194 PrintSafepointStatistics = true;
1195 } else {
1196 stats_array_size = PrintSafepointStatisticsCount;
1197 }
1198 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1199 * sizeof(SafepointStats), mtInternal);
1200 guarantee(_safepoint_stats != NULL,
1201 "not enough memory for safepoint instrumentation data");
1202
1203 if (DeferPollingPageLoopCount >= 0) {
1204 need_to_track_page_armed_status = true;
1205 }
1206 init_done = true;
1207 }
1208
1209 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1210 assert(init_done, "safepoint statistics array hasn't been initialized");
1211 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1212
1213 spstat->_time_stamp = _ts_of_current_safepoint;
1214
1215 VM_Operation *op = VMThread::vm_operation();
1216 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1217 if (op != NULL) {
1218 _safepoint_reasons[spstat->_vmop_type]++;
1219 }
1220
1221 spstat->_nof_total_threads = nof_threads;
1222 spstat->_nof_initial_running_threads = nof_running;
1223 spstat->_nof_threads_hit_page_trap = 0;
1224
1225 // Records the start time of spinning. The real time spent on spinning
1226 // will be adjusted when spin is done. Same trick is applied for time
1227 // spent on waiting for threads to block.
1228 if (nof_running != 0) {
1229 spstat->_time_to_spin = os::javaTimeNanos();
1230 } else {
1231 spstat->_time_to_spin = 0;
1232 }
1233 }
1234
1235 void SafepointSynchronize::update_statistics_on_spin_end() {
1236 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1237
1238 jlong cur_time = os::javaTimeNanos();
1239
1240 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1241 if (spstat->_nof_initial_running_threads != 0) {
1242 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1243 }
1244
1245 if (need_to_track_page_armed_status) {
1246 spstat->_page_armed = (PageArmed == 1);
1247 }
1248
1249 // Records the start time of waiting for to block. Updated when block is done.
1250 if (_waiting_to_block != 0) {
1251 spstat->_time_to_wait_to_block = cur_time;
1252 } else {
1253 spstat->_time_to_wait_to_block = 0;
1254 }
1255 }
1256
1257 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1258 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1259
1260 if (spstat->_nof_threads_wait_to_block != 0) {
1261 spstat->_time_to_wait_to_block = end_time -
1262 spstat->_time_to_wait_to_block;
1263 }
1264
1265 // Records the end time of sync which will be used to calculate the total
1266 // vm operation time. Again, the real time spending in syncing will be deducted
1267 // from the start of the sync time later when end_statistics is called.
1268 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1269 if (spstat->_time_to_sync > _max_sync_time) {
1270 _max_sync_time = spstat->_time_to_sync;
1271 }
1272
1273 spstat->_time_to_do_cleanups = end_time;
1274 }
1275
1276 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1277 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1278
1279 // Record how long spent in cleanup tasks.
1280 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1281
1282 cleanup_end_time = end_time;
1283 }
1284
1285 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1286 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1287
1288 // Update the vm operation time.
1289 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1290 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1291 _max_vmop_time = spstat->_time_to_exec_vmop;
1292 }
1293 // Only the sync time longer than the specified
1294 // PrintSafepointStatisticsTimeout will be printed out right away.
1295 // By default, it is -1 meaning all samples will be put into the list.
1296 if ( PrintSafepointStatisticsTimeout > 0) {
1297 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1298 print_statistics();
1299 }
1300 } else {
1301 // The safepoint statistics will be printed out when the _safepoin_stats
1302 // array fills up.
1303 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1304 print_statistics();
1305 _cur_stat_index = 0;
1306 } else {
1307 _cur_stat_index++;
1308 }
1309 }
1310 }
1311
1312 void SafepointSynchronize::print_statistics() {
1313 for (int index = 0; index <= _cur_stat_index; index++) {
1314 if (index % 30 == 0) {
1315 print_header();
1316 }
1317 SafepointStats* sstats = &_safepoint_stats[index];
1318 tty->print("%8.3f: ", sstats->_time_stamp);
1319 tty->print("%-30s [ "
1320 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
1321 "]",
1322 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
1323 sstats->_nof_total_threads,
1324 sstats->_nof_initial_running_threads,
1325 sstats->_nof_threads_wait_to_block);
1326 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1327 tty->print("[ "
1328 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1329 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
1330 INT64_FORMAT_W(7) " ] ",
1331 (int64_t)(sstats->_time_to_spin / MICROUNITS),
1332 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
1333 (int64_t)(sstats->_time_to_sync / MICROUNITS),
1334 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
1335 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
1336
1337 if (need_to_track_page_armed_status) {
1338 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
1339 }
1340 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
1341 }
1342 }
1343
1344 // This method will be called when VM exits. It will first call
1345 // print_statistics to print out the rest of the sampling. Then
1346 // it tries to summarize the sampling.
1347 void SafepointSynchronize::print_stat_on_exit() {
1348 if (_safepoint_stats == NULL) return;
1349
1350 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1351
1352 // During VM exit, end_statistics may not get called and in that
1353 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1354 // don't print it out.
1355 // Approximate the vm op time.
1356 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1357 os::javaTimeNanos() - cleanup_end_time;
1358
1359 if ( PrintSafepointStatisticsTimeout < 0 ||
1360 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
1361 print_statistics();
1362 }
1363 tty->cr();
1364
1365 // Print out polling page sampling status.
1366 if (!need_to_track_page_armed_status) {
1367 tty->print_cr("Polling page always armed");
1368 } else {
1369 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1370 DeferPollingPageLoopCount);
1371 }
1372
1373 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1374 if (_safepoint_reasons[index] != 0) {
1375 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1376 _safepoint_reasons[index]);
1377 }
1378 }
1379
1380 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1381 _coalesced_vmop_count);
1382 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1383 (int64_t)(_max_sync_time / MICROUNITS));
1384 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1385 INT64_FORMAT_W(5) " ms",
1386 (int64_t)(_max_vmop_time / MICROUNITS));
1387 }
1388
1389 // ------------------------------------------------------------------------------------------------
1390 // Non-product code
1391
1392 #ifndef PRODUCT
1393
1394 void SafepointSynchronize::print_state() {
1395 if (_state == _not_synchronized) {
1396 tty->print_cr("not synchronized");
1397 } else if (_state == _synchronizing || _state == _synchronized) {
1398 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1399 "synchronized");
1400
1401 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1402 cur->safepoint_state()->print();
1403 }
1404 }
1405 }
1406
1407 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1408 if (ShowSafepointMsgs) {
1409 va_list ap;
1410 va_start(ap, format);
1411 tty->vprint_cr(format, ap);
1412 va_end(ap);
1413 }
1414 }
1415
1416 #endif // !PRODUCT