1 /*
2 * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "code/icBuffer.hpp"
30 #include "code/nmethod.hpp"
31 #include "code/pcDesc.hpp"
32 #include "code/scopeDesc.hpp"
33 #include "gc_interface/collectedHeap.hpp"
34 #include "interpreter/interpreter.hpp"
35 #if INCLUDE_JFR
36 #include "jfr/jfrEvents.hpp"
37 #endif
38 #include "memory/resourceArea.hpp"
39 #include "memory/universe.inline.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "oops/symbol.hpp"
42 #include "runtime/compilationPolicy.hpp"
43 #include "runtime/deoptimization.hpp"
44 #include "runtime/frame.inline.hpp"
45 #include "runtime/interfaceSupport.hpp"
46 #include "runtime/mutexLocker.hpp"
47 #include "runtime/orderAccess.inline.hpp"
48 #include "runtime/osThread.hpp"
49 #include "runtime/safepoint.hpp"
50 #include "runtime/signature.hpp"
51 #include "runtime/stubCodeGenerator.hpp"
52 #include "runtime/stubRoutines.hpp"
53 #include "runtime/sweeper.hpp"
54 #include "runtime/synchronizer.hpp"
55 #include "runtime/thread.inline.hpp"
56 #include "services/runtimeService.hpp"
57 #include "utilities/events.hpp"
58 #include "utilities/macros.hpp"
59 #ifdef TARGET_ARCH_x86
60 # include "nativeInst_x86.hpp"
61 # include "vmreg_x86.inline.hpp"
62 #endif
63 #ifdef TARGET_ARCH_sparc
64 # include "nativeInst_sparc.hpp"
65 # include "vmreg_sparc.inline.hpp"
66 #endif
67 #ifdef TARGET_ARCH_zero
68 # include "nativeInst_zero.hpp"
69 # include "vmreg_zero.inline.hpp"
70 #endif
71 #ifdef TARGET_ARCH_arm
72 # include "nativeInst_arm.hpp"
73 # include "vmreg_arm.inline.hpp"
74 #endif
75 #ifdef TARGET_ARCH_ppc
76 # include "nativeInst_ppc.hpp"
77 # include "vmreg_ppc.inline.hpp"
78 #endif
79 #if INCLUDE_ALL_GCS
80 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
81 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
82 #endif // INCLUDE_ALL_GCS
83 #ifdef COMPILER1
84 #include "c1/c1_globals.hpp"
85 #endif
86
87 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
88
89 template <typename E>
90 static void set_current_safepoint_id(E* event, int adjustment = 0) {
91 assert(event != NULL, "invariant");
92 event->set_safepointId(SafepointSynchronize::safepoint_counter() + adjustment);
93 }
94
95 #if INCLUDE_JFR
96 static void post_safepoint_begin_event(EventSafepointBegin* event,
97 int thread_count,
98 int critical_thread_count) {
99 assert(event != NULL, "invariant");
100 assert(event->should_commit(), "invariant");
101 set_current_safepoint_id(event);
102 event->set_totalThreadCount(thread_count);
103 event->set_jniCriticalThreadCount(critical_thread_count);
104 event->commit();
105 }
106
107 static void post_safepoint_cleanup_event(EventSafepointCleanup* event) {
108 assert(event != NULL, "invariant");
109 assert(event->should_commit(), "invariant");
110 set_current_safepoint_id(event);
111 event->commit();
112 }
113
114 static void post_safepoint_synchronize_event(EventSafepointStateSynchronization* event,
115 int initial_number_of_threads,
116 int threads_waiting_to_block,
117 unsigned int iterations) {
118 assert(event != NULL, "invariant");
119 if (event->should_commit()) {
120 // Group this event together with the ones committed after the counter is increased
121 set_current_safepoint_id(event, 1);
122 event->set_initialThreadCount(initial_number_of_threads);
123 event->set_runningThreadCount(threads_waiting_to_block);
124 event->set_iterations(iterations);
125 event->commit();
126 }
127 }
128
129 static void post_safepoint_wait_blocked_event(EventSafepointWaitBlocked* event,
130 int initial_threads_waiting_to_block) {
131 assert(event != NULL, "invariant");
132 assert(event->should_commit(), "invariant");
133 set_current_safepoint_id(event);
134 event->set_runningThreadCount(initial_threads_waiting_to_block);
135 event->commit();
136 }
137
138 static void post_safepoint_cleanup_task_event(EventSafepointCleanupTask* event,
139 const char* name) {
140 assert(event != NULL, "invariant");
141 if (event->should_commit()) {
142 set_current_safepoint_id(event);
143 event->set_name(name);
144 event->commit();
145 }
146 }
147
148 static void post_safepoint_end_event(EventSafepointEnd* event) {
149 assert(event != NULL, "invariant");
150 if (event->should_commit()) {
151 // Group this event together with the ones committed before the counter increased
152 set_current_safepoint_id(event, -1);
153 event->commit();
154 }
155 }
156 #endif
157
158 // --------------------------------------------------------------------------------------------------
159 // Implementation of Safepoint begin/end
160
161 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
162 volatile int SafepointSynchronize::_waiting_to_block = 0;
163 volatile int SafepointSynchronize::_safepoint_counter = 0;
164 int SafepointSynchronize::_current_jni_active_count = 0;
165 long SafepointSynchronize::_end_of_last_safepoint = 0;
166 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
167 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
168 static bool timeout_error_printed = false;
169
170 // Roll all threads forward to a safepoint and suspend them all
171 void SafepointSynchronize::begin() {
172 #if INCLUDE_JFR
173 EventSafepointBegin begin_event;
174 #endif
175 Thread* myThread = Thread::current();
176 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
177
178 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
179 _safepoint_begin_time = os::javaTimeNanos();
180 _ts_of_current_safepoint = tty->time_stamp().seconds();
181 }
182
183 #if INCLUDE_ALL_GCS
184 if (UseConcMarkSweepGC) {
185 // In the future we should investigate whether CMS can use the
186 // more-general mechanism below. DLD (01/05).
187 ConcurrentMarkSweepThread::synchronize(false);
188 } else if (UseG1GC) {
189 SuspendibleThreadSet::synchronize();
190 }
191 #endif // INCLUDE_ALL_GCS
192
193 // By getting the Threads_lock, we assure that no threads are about to start or
194 // exit. It is released again in SafepointSynchronize::end().
195 Threads_lock->lock();
196
197 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
198
199 int nof_threads = Threads::number_of_threads();
200
201 if (TraceSafepoint) {
202 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
203 }
204
205 RuntimeService::record_safepoint_begin();
206
207 MutexLocker mu(Safepoint_lock);
208
209 // Reset the count of active JNI critical threads
210 _current_jni_active_count = 0;
211
212 // Set number of threads to wait for, before we initiate the callbacks
213 _waiting_to_block = nof_threads;
214 TryingToBlock = 0 ;
215 int still_running = nof_threads;
216
217 // Save the starting time, so that it can be compared to see if this has taken
218 // too long to complete.
219 jlong safepoint_limit_time = 0;
220 timeout_error_printed = false;
221
222 // PrintSafepointStatisticsTimeout can be specified separately. When
223 // specified, PrintSafepointStatistics will be set to true in
224 // deferred_initialize_stat method. The initialization has to be done
225 // early enough to avoid any races. See bug 6880029 for details.
226 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
227 deferred_initialize_stat();
228 }
229
230 // Begin the process of bringing the system to a safepoint.
231 // Java threads can be in several different states and are
232 // stopped by different mechanisms:
233 //
234 // 1. Running interpreted
235 // The interpeter dispatch table is changed to force it to
236 // check for a safepoint condition between bytecodes.
237 // 2. Running in native code
238 // When returning from the native code, a Java thread must check
239 // the safepoint _state to see if we must block. If the
240 // VM thread sees a Java thread in native, it does
241 // not wait for this thread to block. The order of the memory
242 // writes and reads of both the safepoint state and the Java
243 // threads state is critical. In order to guarantee that the
244 // memory writes are serialized with respect to each other,
245 // the VM thread issues a memory barrier instruction
246 // (on MP systems). In order to avoid the overhead of issuing
247 // a memory barrier for each Java thread making native calls, each Java
248 // thread performs a write to a single memory page after changing
249 // the thread state. The VM thread performs a sequence of
250 // mprotect OS calls which forces all previous writes from all
251 // Java threads to be serialized. This is done in the
252 // os::serialize_thread_states() call. This has proven to be
253 // much more efficient than executing a membar instruction
254 // on every call to native code.
255 // 3. Running compiled Code
256 // Compiled code reads a global (Safepoint Polling) page that
257 // is set to fault if we are trying to get to a safepoint.
258 // 4. Blocked
259 // A thread which is blocked will not be allowed to return from the
260 // block condition until the safepoint operation is complete.
261 // 5. In VM or Transitioning between states
262 // If a Java thread is currently running in the VM or transitioning
263 // between states, the safepointing code will wait for the thread to
264 // block itself when it attempts transitions to a new state.
265 //
266 #if INCLUDE_JFR
267 EventSafepointStateSynchronization sync_event;
268 #endif
269 int initial_running = 0;
270
271 _state = _synchronizing;
272 OrderAccess::fence();
273
274 // Flush all thread states to memory
275 if (!UseMembar) {
276 os::serialize_thread_states();
277 }
278
279 // Make interpreter safepoint aware
280 Interpreter::notice_safepoints();
281
282 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
283 // Make polling safepoint aware
284 guarantee (PageArmed == 0, "invariant") ;
285 PageArmed = 1 ;
286 os::make_polling_page_unreadable();
287 }
288
289 // Consider using active_processor_count() ... but that call is expensive.
290 int ncpus = os::processor_count() ;
291
292 #ifdef ASSERT
293 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
294 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
295 // Clear the visited flag to ensure that the critical counts are collected properly.
296 cur->set_visited_for_critical_count(false);
297 }
298 #endif // ASSERT
299
300 if (SafepointTimeout)
301 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
302
303 // Iterate through all threads until it have been determined how to stop them all at a safepoint
304 unsigned int iterations = 0;
305 int steps = 0 ;
306 while(still_running > 0) {
307 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
308 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
309 ThreadSafepointState *cur_state = cur->safepoint_state();
310 if (cur_state->is_running()) {
311 cur_state->examine_state_of_thread();
312 if (!cur_state->is_running()) {
313 still_running--;
314 // consider adjusting steps downward:
315 // steps = 0
316 // steps -= NNN
317 // steps >>= 1
318 // steps = MIN(steps, 2000-100)
319 // if (iterations != 0) steps -= NNN
320 }
321 if (TraceSafepoint && Verbose) cur_state->print();
322 }
323 }
324
325 if (iterations == 0) {
326 initial_running = still_running;
327 if (PrintSafepointStatistics) {
328 begin_statistics(nof_threads, still_running);
329 }
330 }
331
332 if (still_running > 0) {
333 // Check for if it takes to long
334 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
335 print_safepoint_timeout(_spinning_timeout);
336 }
337
338 // Spin to avoid context switching.
339 // There's a tension between allowing the mutators to run (and rendezvous)
340 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
341 // a mutator might otherwise use profitably to reach a safepoint. Excessive
342 // spinning by the VM thread on a saturated system can increase rendezvous latency.
343 // Blocking or yielding incur their own penalties in the form of context switching
344 // and the resultant loss of $ residency.
345 //
346 // Further complicating matters is that yield() does not work as naively expected
347 // on many platforms -- yield() does not guarantee that any other ready threads
348 // will run. As such we revert yield_all() after some number of iterations.
349 // Yield_all() is implemented as a short unconditional sleep on some platforms.
350 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
351 // can actually increase the time it takes the VM thread to detect that a system-wide
352 // stop-the-world safepoint has been reached. In a pathological scenario such as that
353 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
354 // In that case the mutators will be stalled waiting for the safepoint to complete and the
355 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
356 // will eventually wake up and detect that all mutators are safe, at which point
357 // we'll again make progress.
358 //
359 // Beware too that that the VMThread typically runs at elevated priority.
360 // Its default priority is higher than the default mutator priority.
361 // Obviously, this complicates spinning.
362 //
363 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
364 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
365 //
366 // See the comments in synchronizer.cpp for additional remarks on spinning.
367 //
368 // In the future we might:
369 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
370 // This is tricky as the path used by a thread exiting the JVM (say on
371 // on JNI call-out) simply stores into its state field. The burden
372 // is placed on the VM thread, which must poll (spin).
373 // 2. Find something useful to do while spinning. If the safepoint is GC-related
374 // we might aggressively scan the stacks of threads that are already safe.
375 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
376 // If all the mutators are ONPROC there's no reason to sleep or yield.
377 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
378 // 5. Check system saturation. If the system is not fully saturated then
379 // simply spin and avoid sleep/yield.
380 // 6. As still-running mutators rendezvous they could unpark the sleeping
381 // VMthread. This works well for still-running mutators that become
382 // safe. The VMthread must still poll for mutators that call-out.
383 // 7. Drive the policy on time-since-begin instead of iterations.
384 // 8. Consider making the spin duration a function of the # of CPUs:
385 // Spin = (((ncpus-1) * M) + K) + F(still_running)
386 // Alternately, instead of counting iterations of the outer loop
387 // we could count the # of threads visited in the inner loop, above.
388 // 9. On windows consider using the return value from SwitchThreadTo()
389 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
390
391 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
392 guarantee (PageArmed == 0, "invariant") ;
393 PageArmed = 1 ;
394 os::make_polling_page_unreadable();
395 }
396
397 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
398 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
399 ++steps ;
400 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
401 SpinPause() ; // MP-Polite spin
402 } else
403 if (steps < DeferThrSuspendLoopCount) {
404 os::NakedYield() ;
405 } else {
406 os::yield_all(steps) ;
407 // Alternately, the VM thread could transiently depress its scheduling priority or
408 // transiently increase the priority of the tardy mutator(s).
409 }
410
411 iterations ++ ;
412 }
413 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
414 }
415 assert(still_running == 0, "sanity check");
416
417 if (PrintSafepointStatistics) {
418 update_statistics_on_spin_end();
419 }
420
421 #if INCLUDE_JFR
422 if (sync_event.should_commit()) {
423 post_safepoint_synchronize_event(&sync_event, initial_running, _waiting_to_block, iterations);
424 }
425 #endif
426
427 // wait until all threads are stopped
428 {
429 #if INCLUDE_JFR
430 EventSafepointWaitBlocked wait_blocked_event;
431 #endif
432 int initial_waiting_to_block = _waiting_to_block;
433
434 while (_waiting_to_block > 0) {
435 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
436 if (!SafepointTimeout || timeout_error_printed) {
437 Safepoint_lock->wait(true); // true, means with no safepoint checks
438 } else {
439 // Compute remaining time
440 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
441
442 // If there is no remaining time, then there is an error
443 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
444 print_safepoint_timeout(_blocking_timeout);
445 }
446 }
447 }
448 assert(_waiting_to_block == 0, "sanity check");
449
450 #ifndef PRODUCT
451 if (SafepointTimeout) {
452 jlong current_time = os::javaTimeNanos();
453 if (safepoint_limit_time < current_time) {
454 tty->print_cr("# SafepointSynchronize: Finished after "
455 INT64_FORMAT_W(6) " ms",
456 ((current_time - safepoint_limit_time) / MICROUNITS +
457 SafepointTimeoutDelay));
458 }
459 }
460 #endif
461
462 assert((_safepoint_counter & 0x1) == 0, "must be even");
463 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
464 _safepoint_counter ++;
465
466 // Record state
467 _state = _synchronized;
468
469 OrderAccess::fence();
470
471 #if INCLUDE_JFR
472 if (wait_blocked_event.should_commit()) {
473 post_safepoint_wait_blocked_event(&wait_blocked_event, initial_waiting_to_block);
474 }
475 #endif
476 }
477
478 #ifdef ASSERT
479 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
480 // make sure all the threads were visited
481 assert(cur->was_visited_for_critical_count(), "missed a thread");
482 }
483 #endif // ASSERT
484
485 // Update the count of active JNI critical regions
486 GC_locker::set_jni_lock_count(_current_jni_active_count);
487
488 if (TraceSafepoint) {
489 VM_Operation *op = VMThread::vm_operation();
490 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
491 }
492
493 RuntimeService::record_safepoint_synchronized();
494 if (PrintSafepointStatistics) {
495 update_statistics_on_sync_end(os::javaTimeNanos());
496 }
497
498 // Call stuff that needs to be run when a safepoint is just about to be completed
499 {
500 #if INCLUDE_JFR
501 EventSafepointCleanup cleanup_event;
502 #endif
503 do_cleanup_tasks();
504 #if INCLUDE_JFR
505 if (cleanup_event.should_commit()) {
506 post_safepoint_cleanup_event(&cleanup_event);
507 }
508 #endif
509 }
510
511 if (PrintSafepointStatistics) {
512 // Record how much time spend on the above cleanup tasks
513 update_statistics_on_cleanup_end(os::javaTimeNanos());
514 }
515
516 #if INCLUDE_JFR
517 if (begin_event.should_commit()) {
518 post_safepoint_begin_event(&begin_event, nof_threads, _current_jni_active_count);
519 }
520 #endif
521 }
522
523 // Wake up all threads, so they are ready to resume execution after the safepoint
524 // operation has been carried out
525 void SafepointSynchronize::end() {
526
527 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
528 assert((_safepoint_counter & 0x1) == 1, "must be odd");
529 #if INCLUDE_JFR
530 EventSafepointEnd event;
531 #endif
532 _safepoint_counter ++;
533 // memory fence isn't required here since an odd _safepoint_counter
534 // value can do no harm and a fence is issued below anyway.
535
536 DEBUG_ONLY(Thread* myThread = Thread::current();)
537 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
538
539 if (PrintSafepointStatistics) {
540 end_statistics(os::javaTimeNanos());
541 }
542
543 #ifdef ASSERT
544 // A pending_exception cannot be installed during a safepoint. The threads
545 // may install an async exception after they come back from a safepoint into
546 // pending_exception after they unblock. But that should happen later.
547 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
548 assert (!(cur->has_pending_exception() &&
549 cur->safepoint_state()->is_at_poll_safepoint()),
550 "safepoint installed a pending exception");
551 }
552 #endif // ASSERT
553
554 if (PageArmed) {
555 // Make polling safepoint aware
556 os::make_polling_page_readable();
557 PageArmed = 0 ;
558 }
559
560 // Remove safepoint check from interpreter
561 Interpreter::ignore_safepoints();
562
563 {
564 MutexLocker mu(Safepoint_lock);
565
566 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
567
568 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
569 // when they get restarted.
570 _state = _not_synchronized;
571 OrderAccess::fence();
572
573 if (TraceSafepoint) {
574 tty->print_cr("Leaving safepoint region");
575 }
576
577 // Start suspended threads
578 for(JavaThread *current = Threads::first(); current; current = current->next()) {
579 // A problem occurring on Solaris is when attempting to restart threads
580 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
581 // to the next one (since it has been running the longest). We then have
582 // to wait for a cpu to become available before we can continue restarting
583 // threads.
584 // FIXME: This causes the performance of the VM to degrade when active and with
585 // large numbers of threads. Apparently this is due to the synchronous nature
586 // of suspending threads.
587 //
588 // TODO-FIXME: the comments above are vestigial and no longer apply.
589 // Furthermore, using solaris' schedctl in this particular context confers no benefit
590 if (VMThreadHintNoPreempt) {
591 os::hint_no_preempt();
592 }
593 ThreadSafepointState* cur_state = current->safepoint_state();
594 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
595 cur_state->restart();
596 assert(cur_state->is_running(), "safepoint state has not been reset");
597 }
598
599 RuntimeService::record_safepoint_end();
600
601 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
602 // blocked in signal_thread_blocked
603 Threads_lock->unlock();
604
605 }
606 #if INCLUDE_ALL_GCS
607 // If there are any concurrent GC threads resume them.
608 if (UseConcMarkSweepGC) {
609 ConcurrentMarkSweepThread::desynchronize(false);
610 } else if (UseG1GC) {
611 SuspendibleThreadSet::desynchronize();
612 }
613 #endif // INCLUDE_ALL_GCS
614 // record this time so VMThread can keep track how much time has elasped
615 // since last safepoint.
616 _end_of_last_safepoint = os::javaTimeMillis();
617 #if INCLUDE_JFR
618 if (event.should_commit()) {
619 post_safepoint_end_event(&event);
620 }
621 #endif
622 }
623
624 bool SafepointSynchronize::is_cleanup_needed() {
625 // Need a safepoint if some inline cache buffers is non-empty
626 if (!InlineCacheBuffer::is_empty()) return true;
627 return false;
628 }
629
630
631
632 // Various cleaning tasks that should be done periodically at safepoints
633 void SafepointSynchronize::do_cleanup_tasks() {
634 {
635 const char* name = "deflating idle monitors";
636 #if INCLUDE_JFR
637 EventSafepointCleanupTask event;
638 #endif
639 TraceTime t1(name, TraceSafepointCleanupTime);
640 ObjectSynchronizer::deflate_idle_monitors();
641 #if INCLUDE_JFR
642 if (event.should_commit()) {
643 post_safepoint_cleanup_task_event(&event, name);
644 }
645 #endif
646 }
647
648 {
649 const char* name = "updating inline caches";
650 #if INCLUDE_JFR
651 EventSafepointCleanupTask event;
652 #endif
653 TraceTime t2(name, TraceSafepointCleanupTime);
654 InlineCacheBuffer::update_inline_caches();
655 #if INCLUDE_JFR
656 if (event.should_commit()) {
657 post_safepoint_cleanup_task_event(&event, name);
658 }
659 #endif
660 }
661 {
662 const char* name = "compilation policy safepoint handler";
663 #if INCLUDE_JFR
664 EventSafepointCleanupTask event;
665 #endif
666 TraceTime t3(name, TraceSafepointCleanupTime);
667 CompilationPolicy::policy()->do_safepoint_work();
668 #if INCLUDE_JFR
669 if (event.should_commit()) {
670 post_safepoint_cleanup_task_event(&event, name);
671 }
672 #endif
673 }
674
675 {
676 const char* name = "mark nmethods";
677 #if INCLUDE_JFR
678 EventSafepointCleanupTask event;
679 #endif
680 TraceTime t4(name, TraceSafepointCleanupTime);
681 NMethodSweeper::mark_active_nmethods();
682 #if INCLUDE_JFR
683 if (event.should_commit()) {
684 post_safepoint_cleanup_task_event(&event, name);
685 }
686 #endif
687 }
688
689 if (SymbolTable::needs_rehashing()) {
690 const char* name = "rehashing symbol table";
691 #if INCLUDE_JFR
692 EventSafepointCleanupTask event;
693 #endif
694 TraceTime t5(name, TraceSafepointCleanupTime);
695 SymbolTable::rehash_table();
696 #if INCLUDE_JFR
697 if (event.should_commit()) {
698 post_safepoint_cleanup_task_event(&event, name);
699 }
700 #endif
701 }
702
703 if (StringTable::needs_rehashing()) {
704 const char* name = "rehashing string table";
705 #if INCLUDE_JFR
706 EventSafepointCleanupTask event;
707 #endif
708 TraceTime t6(name, TraceSafepointCleanupTime);
709 StringTable::rehash_table();
710 #if INCLUDE_JFR
711 if (event.should_commit()) {
712 post_safepoint_cleanup_task_event(&event, name);
713 }
714 #endif
715 }
716
717 // rotate log files?
718 if (UseGCLogFileRotation) {
719 gclog_or_tty->rotate_log(false);
720 }
721
722 {
723 // CMS delays purging the CLDG until the beginning of the next safepoint and to
724 // make sure concurrent sweep is done
725 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
726 ClassLoaderDataGraph::purge_if_needed();
727 }
728 }
729
730
731 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
732 switch(state) {
733 case _thread_in_native:
734 // native threads are safe if they have no java stack or have walkable stack
735 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
736
737 // blocked threads should have already have walkable stack
738 case _thread_blocked:
739 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
740 return true;
741
742 default:
743 return false;
744 }
745 }
746
747
748 // See if the thread is running inside a lazy critical native and
749 // update the thread critical count if so. Also set a suspend flag to
750 // cause the native wrapper to return into the JVM to do the unlock
751 // once the native finishes.
752 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
753 if (state == _thread_in_native &&
754 thread->has_last_Java_frame() &&
755 thread->frame_anchor()->walkable()) {
756 // This thread might be in a critical native nmethod so look at
757 // the top of the stack and increment the critical count if it
758 // is.
759 frame wrapper_frame = thread->last_frame();
760 CodeBlob* stub_cb = wrapper_frame.cb();
761 if (stub_cb != NULL &&
762 stub_cb->is_nmethod() &&
763 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
764 // A thread could potentially be in a critical native across
765 // more than one safepoint, so only update the critical state on
766 // the first one. When it returns it will perform the unlock.
767 if (!thread->do_critical_native_unlock()) {
768 #ifdef ASSERT
769 if (!thread->in_critical()) {
770 GC_locker::increment_debug_jni_lock_count();
771 }
772 #endif
773 thread->enter_critical();
774 // Make sure the native wrapper calls back on return to
775 // perform the needed critical unlock.
776 thread->set_critical_native_unlock();
777 }
778 }
779 }
780 }
781
782
783
784 // -------------------------------------------------------------------------------------------------------
785 // Implementation of Safepoint callback point
786
787 void SafepointSynchronize::block(JavaThread *thread) {
788 assert(thread != NULL, "thread must be set");
789 assert(thread->is_Java_thread(), "not a Java thread");
790
791 // Threads shouldn't block if they are in the middle of printing, but...
792 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
793
794 // Only bail from the block() call if the thread is gone from the
795 // thread list; starting to exit should still block.
796 if (thread->is_terminated()) {
797 // block current thread if we come here from native code when VM is gone
798 thread->block_if_vm_exited();
799
800 // otherwise do nothing
801 return;
802 }
803
804 JavaThreadState state = thread->thread_state();
805 thread->frame_anchor()->make_walkable(thread);
806
807 // Check that we have a valid thread_state at this point
808 switch(state) {
809 case _thread_in_vm_trans:
810 case _thread_in_Java: // From compiled code
811
812 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
813 // we pretend we are still in the VM.
814 thread->set_thread_state(_thread_in_vm);
815
816 if (is_synchronizing()) {
817 Atomic::inc (&TryingToBlock) ;
818 }
819
820 // We will always be holding the Safepoint_lock when we are examine the state
821 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
822 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
823 Safepoint_lock->lock_without_safepoint_check();
824 if (is_synchronizing()) {
825 // Decrement the number of threads to wait for and signal vm thread
826 assert(_waiting_to_block > 0, "sanity check");
827 _waiting_to_block--;
828 thread->safepoint_state()->set_has_called_back(true);
829
830 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
831 if (thread->in_critical()) {
832 // Notice that this thread is in a critical section
833 increment_jni_active_count();
834 }
835
836 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
837 if (_waiting_to_block == 0) {
838 Safepoint_lock->notify_all();
839 }
840 }
841
842 // We transition the thread to state _thread_blocked here, but
843 // we can't do our usual check for external suspension and then
844 // self-suspend after the lock_without_safepoint_check() call
845 // below because we are often called during transitions while
846 // we hold different locks. That would leave us suspended while
847 // holding a resource which results in deadlocks.
848 thread->set_thread_state(_thread_blocked);
849 Safepoint_lock->unlock();
850
851 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
852 // the entire safepoint, the threads will all line up here during the safepoint.
853 Threads_lock->lock_without_safepoint_check();
854 // restore original state. This is important if the thread comes from compiled code, so it
855 // will continue to execute with the _thread_in_Java state.
856 thread->set_thread_state(state);
857 Threads_lock->unlock();
858 break;
859
860 case _thread_in_native_trans:
861 case _thread_blocked_trans:
862 case _thread_new_trans:
863 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
864 thread->print_thread_state();
865 fatal("Deadlock in safepoint code. "
866 "Should have called back to the VM before blocking.");
867 }
868
869 // We transition the thread to state _thread_blocked here, but
870 // we can't do our usual check for external suspension and then
871 // self-suspend after the lock_without_safepoint_check() call
872 // below because we are often called during transitions while
873 // we hold different locks. That would leave us suspended while
874 // holding a resource which results in deadlocks.
875 thread->set_thread_state(_thread_blocked);
876
877 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
878 // the safepoint code might still be waiting for it to block. We need to change the state here,
879 // so it can see that it is at a safepoint.
880
881 // Block until the safepoint operation is completed.
882 Threads_lock->lock_without_safepoint_check();
883
884 // Restore state
885 thread->set_thread_state(state);
886
887 Threads_lock->unlock();
888 break;
889
890 default:
891 fatal(err_msg("Illegal threadstate encountered: %d", state));
892 }
893
894 // Check for pending. async. exceptions or suspends - except if the
895 // thread was blocked inside the VM. has_special_runtime_exit_condition()
896 // is called last since it grabs a lock and we only want to do that when
897 // we must.
898 //
899 // Note: we never deliver an async exception at a polling point as the
900 // compiler may not have an exception handler for it. The polling
901 // code will notice the async and deoptimize and the exception will
902 // be delivered. (Polling at a return point is ok though). Sure is
903 // a lot of bother for a deprecated feature...
904 //
905 // We don't deliver an async exception if the thread state is
906 // _thread_in_native_trans so JNI functions won't be called with
907 // a surprising pending exception. If the thread state is going back to java,
908 // async exception is checked in check_special_condition_for_native_trans().
909
910 if (state != _thread_blocked_trans &&
911 state != _thread_in_vm_trans &&
912 thread->has_special_runtime_exit_condition()) {
913 thread->handle_special_runtime_exit_condition(
914 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
915 }
916 }
917
918 // ------------------------------------------------------------------------------------------------------
919 // Exception handlers
920
921
922 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
923 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
924 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
925 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
926
927 if (ShowSafepointMsgs) {
928 tty->print("handle_polling_page_exception: ");
929 }
930
931 if (PrintSafepointStatistics) {
932 inc_page_trap_count();
933 }
934
935 ThreadSafepointState* state = thread->safepoint_state();
936
937 state->handle_polling_page_exception();
938 }
939
940
941 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
942 if (!timeout_error_printed) {
943 timeout_error_printed = true;
944 // Print out the thread infor which didn't reach the safepoint for debugging
945 // purposes (useful when there are lots of threads in the debugger).
946 tty->cr();
947 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
948 if (reason == _spinning_timeout) {
949 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
950 } else if (reason == _blocking_timeout) {
951 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
952 }
953
954 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
955 ThreadSafepointState *cur_state;
956 ResourceMark rm;
957 for(JavaThread *cur_thread = Threads::first(); cur_thread;
958 cur_thread = cur_thread->next()) {
959 cur_state = cur_thread->safepoint_state();
960
961 if (cur_thread->thread_state() != _thread_blocked &&
962 ((reason == _spinning_timeout && cur_state->is_running()) ||
963 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
964 tty->print("# ");
965 cur_thread->print();
966 tty->cr();
967 }
968 }
969 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
970 }
971
972 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
973 // ShowMessageBoxOnError.
974 if (AbortVMOnSafepointTimeout) {
975 char msg[1024];
976 VM_Operation *op = VMThread::vm_operation();
977 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
978 SafepointTimeoutDelay,
979 op != NULL ? op->name() : "no vm operation");
980 fatal(msg);
981 }
982 }
983
984
985 // -------------------------------------------------------------------------------------------------------
986 // Implementation of ThreadSafepointState
987
988 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
989 _thread = thread;
990 _type = _running;
991 _has_called_back = false;
992 _at_poll_safepoint = false;
993 }
994
995 void ThreadSafepointState::create(JavaThread *thread) {
996 ThreadSafepointState *state = new ThreadSafepointState(thread);
997 thread->set_safepoint_state(state);
998 }
999
1000 void ThreadSafepointState::destroy(JavaThread *thread) {
1001 if (thread->safepoint_state()) {
1002 delete(thread->safepoint_state());
1003 thread->set_safepoint_state(NULL);
1004 }
1005 }
1006
1007 void ThreadSafepointState::examine_state_of_thread() {
1008 assert(is_running(), "better be running or just have hit safepoint poll");
1009
1010 JavaThreadState state = _thread->thread_state();
1011
1012 // Save the state at the start of safepoint processing.
1013 _orig_thread_state = state;
1014
1015 // Check for a thread that is suspended. Note that thread resume tries
1016 // to grab the Threads_lock which we own here, so a thread cannot be
1017 // resumed during safepoint synchronization.
1018
1019 // We check to see if this thread is suspended without locking to
1020 // avoid deadlocking with a third thread that is waiting for this
1021 // thread to be suspended. The third thread can notice the safepoint
1022 // that we're trying to start at the beginning of its SR_lock->wait()
1023 // call. If that happens, then the third thread will block on the
1024 // safepoint while still holding the underlying SR_lock. We won't be
1025 // able to get the SR_lock and we'll deadlock.
1026 //
1027 // We don't need to grab the SR_lock here for two reasons:
1028 // 1) The suspend flags are both volatile and are set with an
1029 // Atomic::cmpxchg() call so we should see the suspended
1030 // state right away.
1031 // 2) We're being called from the safepoint polling loop; if
1032 // we don't see the suspended state on this iteration, then
1033 // we'll come around again.
1034 //
1035 bool is_suspended = _thread->is_ext_suspended();
1036 if (is_suspended) {
1037 roll_forward(_at_safepoint);
1038 return;
1039 }
1040
1041 // Some JavaThread states have an initial safepoint state of
1042 // running, but are actually at a safepoint. We will happily
1043 // agree and update the safepoint state here.
1044 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
1045 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
1046 roll_forward(_at_safepoint);
1047 return;
1048 }
1049
1050 if (state == _thread_in_vm) {
1051 roll_forward(_call_back);
1052 return;
1053 }
1054
1055 // All other thread states will continue to run until they
1056 // transition and self-block in state _blocked
1057 // Safepoint polling in compiled code causes the Java threads to do the same.
1058 // Note: new threads may require a malloc so they must be allowed to finish
1059
1060 assert(is_running(), "examine_state_of_thread on non-running thread");
1061 return;
1062 }
1063
1064 // Returns true is thread could not be rolled forward at present position.
1065 void ThreadSafepointState::roll_forward(suspend_type type) {
1066 _type = type;
1067
1068 switch(_type) {
1069 case _at_safepoint:
1070 SafepointSynchronize::signal_thread_at_safepoint();
1071 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
1072 if (_thread->in_critical()) {
1073 // Notice that this thread is in a critical section
1074 SafepointSynchronize::increment_jni_active_count();
1075 }
1076 break;
1077
1078 case _call_back:
1079 set_has_called_back(false);
1080 break;
1081
1082 case _running:
1083 default:
1084 ShouldNotReachHere();
1085 }
1086 }
1087
1088 void ThreadSafepointState::restart() {
1089 switch(type()) {
1090 case _at_safepoint:
1091 case _call_back:
1092 break;
1093
1094 case _running:
1095 default:
1096 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
1097 _thread, _type);
1098 _thread->print();
1099 ShouldNotReachHere();
1100 }
1101 _type = _running;
1102 set_has_called_back(false);
1103 }
1104
1105
1106 void ThreadSafepointState::print_on(outputStream *st) const {
1107 const char *s = NULL;
1108
1109 switch(_type) {
1110 case _running : s = "_running"; break;
1111 case _at_safepoint : s = "_at_safepoint"; break;
1112 case _call_back : s = "_call_back"; break;
1113 default:
1114 ShouldNotReachHere();
1115 }
1116
1117 st->print_cr("Thread: " INTPTR_FORMAT
1118 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1119 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1120 _at_poll_safepoint);
1121
1122 _thread->print_thread_state_on(st);
1123 }
1124
1125
1126 // ---------------------------------------------------------------------------------------------------------------------
1127
1128 // Block the thread at the safepoint poll or poll return.
1129 void ThreadSafepointState::handle_polling_page_exception() {
1130
1131 // Check state. block() will set thread state to thread_in_vm which will
1132 // cause the safepoint state _type to become _call_back.
1133 assert(type() == ThreadSafepointState::_running,
1134 "polling page exception on thread not running state");
1135
1136 // Step 1: Find the nmethod from the return address
1137 if (ShowSafepointMsgs && Verbose) {
1138 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1139 }
1140 address real_return_addr = thread()->saved_exception_pc();
1141
1142 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1143 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1144 nmethod* nm = (nmethod*)cb;
1145
1146 // Find frame of caller
1147 frame stub_fr = thread()->last_frame();
1148 CodeBlob* stub_cb = stub_fr.cb();
1149 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1150 RegisterMap map(thread(), true);
1151 frame caller_fr = stub_fr.sender(&map);
1152
1153 // Should only be poll_return or poll
1154 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1155
1156 // This is a poll immediately before a return. The exception handling code
1157 // has already had the effect of causing the return to occur, so the execution
1158 // will continue immediately after the call. In addition, the oopmap at the
1159 // return point does not mark the return value as an oop (if it is), so
1160 // it needs a handle here to be updated.
1161 if( nm->is_at_poll_return(real_return_addr) ) {
1162 // See if return type is an oop.
1163 bool return_oop = nm->method()->is_returning_oop();
1164 Handle return_value;
1165 if (return_oop) {
1166 // The oop result has been saved on the stack together with all
1167 // the other registers. In order to preserve it over GCs we need
1168 // to keep it in a handle.
1169 oop result = caller_fr.saved_oop_result(&map);
1170 assert(result == NULL || result->is_oop(), "must be oop");
1171 return_value = Handle(thread(), result);
1172 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1173 }
1174
1175 // Block the thread
1176 SafepointSynchronize::block(thread());
1177
1178 // restore oop result, if any
1179 if (return_oop) {
1180 caller_fr.set_saved_oop_result(&map, return_value());
1181 }
1182 }
1183
1184 // This is a safepoint poll. Verify the return address and block.
1185 else {
1186 set_at_poll_safepoint(true);
1187
1188 // verify the blob built the "return address" correctly
1189 assert(real_return_addr == caller_fr.pc(), "must match");
1190
1191 // Block the thread
1192 SafepointSynchronize::block(thread());
1193 set_at_poll_safepoint(false);
1194
1195 // If we have a pending async exception deoptimize the frame
1196 // as otherwise we may never deliver it.
1197 if (thread()->has_async_condition()) {
1198 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1199 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1200 }
1201
1202 // If an exception has been installed we must check for a pending deoptimization
1203 // Deoptimize frame if exception has been thrown.
1204
1205 if (thread()->has_pending_exception() ) {
1206 RegisterMap map(thread(), true);
1207 frame caller_fr = stub_fr.sender(&map);
1208 if (caller_fr.is_deoptimized_frame()) {
1209 // The exception patch will destroy registers that are still
1210 // live and will be needed during deoptimization. Defer the
1211 // Async exception should have defered the exception until the
1212 // next safepoint which will be detected when we get into
1213 // the interpreter so if we have an exception now things
1214 // are messed up.
1215
1216 fatal("Exception installed and deoptimization is pending");
1217 }
1218 }
1219 }
1220 }
1221
1222
1223 //
1224 // Statistics & Instrumentations
1225 //
1226 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1227 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1228 int SafepointSynchronize::_cur_stat_index = 0;
1229 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1230 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1231 jlong SafepointSynchronize::_max_sync_time = 0;
1232 jlong SafepointSynchronize::_max_vmop_time = 0;
1233 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1234
1235 static jlong cleanup_end_time = 0;
1236 static bool need_to_track_page_armed_status = false;
1237 static bool init_done = false;
1238
1239 // Helper method to print the header.
1240 static void print_header() {
1241 tty->print(" vmop "
1242 "[threads: total initially_running wait_to_block] ");
1243 tty->print("[time: spin block sync cleanup vmop] ");
1244
1245 // no page armed status printed out if it is always armed.
1246 if (need_to_track_page_armed_status) {
1247 tty->print("page_armed ");
1248 }
1249
1250 tty->print_cr("page_trap_count");
1251 }
1252
1253 void SafepointSynchronize::deferred_initialize_stat() {
1254 if (init_done) return;
1255
1256 if (PrintSafepointStatisticsCount <= 0) {
1257 fatal("Wrong PrintSafepointStatisticsCount");
1258 }
1259
1260 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1261 // be printed right away, in which case, _safepoint_stats will regress to
1262 // a single element array. Otherwise, it is a circular ring buffer with default
1263 // size of PrintSafepointStatisticsCount.
1264 int stats_array_size;
1265 if (PrintSafepointStatisticsTimeout > 0) {
1266 stats_array_size = 1;
1267 PrintSafepointStatistics = true;
1268 } else {
1269 stats_array_size = PrintSafepointStatisticsCount;
1270 }
1271 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1272 * sizeof(SafepointStats), mtInternal);
1273 guarantee(_safepoint_stats != NULL,
1274 "not enough memory for safepoint instrumentation data");
1275
1276 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1277 need_to_track_page_armed_status = true;
1278 }
1279 init_done = true;
1280 }
1281
1282 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1283 assert(init_done, "safepoint statistics array hasn't been initialized");
1284 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1285
1286 spstat->_time_stamp = _ts_of_current_safepoint;
1287
1288 VM_Operation *op = VMThread::vm_operation();
1289 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1290 if (op != NULL) {
1291 _safepoint_reasons[spstat->_vmop_type]++;
1292 }
1293
1294 spstat->_nof_total_threads = nof_threads;
1295 spstat->_nof_initial_running_threads = nof_running;
1296 spstat->_nof_threads_hit_page_trap = 0;
1297
1298 // Records the start time of spinning. The real time spent on spinning
1299 // will be adjusted when spin is done. Same trick is applied for time
1300 // spent on waiting for threads to block.
1301 if (nof_running != 0) {
1302 spstat->_time_to_spin = os::javaTimeNanos();
1303 } else {
1304 spstat->_time_to_spin = 0;
1305 }
1306 }
1307
1308 void SafepointSynchronize::update_statistics_on_spin_end() {
1309 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1310
1311 jlong cur_time = os::javaTimeNanos();
1312
1313 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1314 if (spstat->_nof_initial_running_threads != 0) {
1315 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1316 }
1317
1318 if (need_to_track_page_armed_status) {
1319 spstat->_page_armed = (PageArmed == 1);
1320 }
1321
1322 // Records the start time of waiting for to block. Updated when block is done.
1323 if (_waiting_to_block != 0) {
1324 spstat->_time_to_wait_to_block = cur_time;
1325 } else {
1326 spstat->_time_to_wait_to_block = 0;
1327 }
1328 }
1329
1330 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1331 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1332
1333 if (spstat->_nof_threads_wait_to_block != 0) {
1334 spstat->_time_to_wait_to_block = end_time -
1335 spstat->_time_to_wait_to_block;
1336 }
1337
1338 // Records the end time of sync which will be used to calculate the total
1339 // vm operation time. Again, the real time spending in syncing will be deducted
1340 // from the start of the sync time later when end_statistics is called.
1341 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1342 if (spstat->_time_to_sync > _max_sync_time) {
1343 _max_sync_time = spstat->_time_to_sync;
1344 }
1345
1346 spstat->_time_to_do_cleanups = end_time;
1347 }
1348
1349 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1350 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1351
1352 // Record how long spent in cleanup tasks.
1353 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1354
1355 cleanup_end_time = end_time;
1356 }
1357
1358 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1359 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1360
1361 // Update the vm operation time.
1362 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1363 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1364 _max_vmop_time = spstat->_time_to_exec_vmop;
1365 }
1366 // Only the sync time longer than the specified
1367 // PrintSafepointStatisticsTimeout will be printed out right away.
1368 // By default, it is -1 meaning all samples will be put into the list.
1369 if ( PrintSafepointStatisticsTimeout > 0) {
1370 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1371 print_statistics();
1372 }
1373 } else {
1374 // The safepoint statistics will be printed out when the _safepoin_stats
1375 // array fills up.
1376 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1377 print_statistics();
1378 _cur_stat_index = 0;
1379 } else {
1380 _cur_stat_index++;
1381 }
1382 }
1383 }
1384
1385 void SafepointSynchronize::print_statistics() {
1386 SafepointStats* sstats = _safepoint_stats;
1387
1388 for (int index = 0; index <= _cur_stat_index; index++) {
1389 if (index % 30 == 0) {
1390 print_header();
1391 }
1392 sstats = &_safepoint_stats[index];
1393 tty->print("%.3f: ", sstats->_time_stamp);
1394 tty->print("%-26s ["
1395 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1396 " ] ",
1397 sstats->_vmop_type == -1 ? "no vm operation" :
1398 VM_Operation::name(sstats->_vmop_type),
1399 sstats->_nof_total_threads,
1400 sstats->_nof_initial_running_threads,
1401 sstats->_nof_threads_wait_to_block);
1402 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1403 tty->print(" ["
1404 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1405 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1406 INT64_FORMAT_W(6) " ] ",
1407 sstats->_time_to_spin / MICROUNITS,
1408 sstats->_time_to_wait_to_block / MICROUNITS,
1409 sstats->_time_to_sync / MICROUNITS,
1410 sstats->_time_to_do_cleanups / MICROUNITS,
1411 sstats->_time_to_exec_vmop / MICROUNITS);
1412
1413 if (need_to_track_page_armed_status) {
1414 tty->print(INT32_FORMAT " ", sstats->_page_armed);
1415 }
1416 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
1417 }
1418 }
1419
1420 // This method will be called when VM exits. It will first call
1421 // print_statistics to print out the rest of the sampling. Then
1422 // it tries to summarize the sampling.
1423 void SafepointSynchronize::print_stat_on_exit() {
1424 if (_safepoint_stats == NULL) return;
1425
1426 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1427
1428 // During VM exit, end_statistics may not get called and in that
1429 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1430 // don't print it out.
1431 // Approximate the vm op time.
1432 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1433 os::javaTimeNanos() - cleanup_end_time;
1434
1435 if ( PrintSafepointStatisticsTimeout < 0 ||
1436 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1437 print_statistics();
1438 }
1439 tty->cr();
1440
1441 // Print out polling page sampling status.
1442 if (!need_to_track_page_armed_status) {
1443 if (UseCompilerSafepoints) {
1444 tty->print_cr("Polling page always armed");
1445 }
1446 } else {
1447 tty->print_cr("Defer polling page loop count = %d\n",
1448 DeferPollingPageLoopCount);
1449 }
1450
1451 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1452 if (_safepoint_reasons[index] != 0) {
1453 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1454 _safepoint_reasons[index]);
1455 }
1456 }
1457
1458 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1459 _coalesced_vmop_count);
1460 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1461 _max_sync_time / MICROUNITS);
1462 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1463 INT64_FORMAT_W(5) " ms",
1464 _max_vmop_time / MICROUNITS);
1465 }
1466
1467 // ------------------------------------------------------------------------------------------------
1468 // Non-product code
1469
1470 #ifndef PRODUCT
1471
1472 void SafepointSynchronize::print_state() {
1473 if (_state == _not_synchronized) {
1474 tty->print_cr("not synchronized");
1475 } else if (_state == _synchronizing || _state == _synchronized) {
1476 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1477 "synchronized");
1478
1479 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1480 cur->safepoint_state()->print();
1481 }
1482 }
1483 }
1484
1485 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1486 if (ShowSafepointMsgs) {
1487 va_list ap;
1488 va_start(ap, format);
1489 tty->vprint_cr(format, ap);
1490 va_end(ap);
1491 }
1492 }
1493
1494 #endif // !PRODUCT