Thu, 31 Oct 2019 19:36:58 +0100
8231398: Add time tracing for gc log rotation at safepoint cleanup
Reviewed-by: phh, andrew
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.
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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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).
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23 */
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "code/icBuffer.hpp"
30 #include "code/nmethod.hpp"
31 #include "code/pcDesc.hpp"
32 #include "code/scopeDesc.hpp"
33 #include "gc_interface/collectedHeap.hpp"
34 #include "interpreter/interpreter.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "memory/universe.inline.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "oops/symbol.hpp"
39 #include "runtime/compilationPolicy.hpp"
40 #include "runtime/deoptimization.hpp"
41 #include "runtime/frame.inline.hpp"
42 #include "runtime/interfaceSupport.hpp"
43 #include "runtime/mutexLocker.hpp"
44 #include "runtime/orderAccess.inline.hpp"
45 #include "runtime/osThread.hpp"
46 #include "runtime/safepoint.hpp"
47 #include "runtime/signature.hpp"
48 #include "runtime/stubCodeGenerator.hpp"
49 #include "runtime/stubRoutines.hpp"
50 #include "runtime/sweeper.hpp"
51 #include "runtime/synchronizer.hpp"
52 #include "runtime/thread.inline.hpp"
53 #include "services/runtimeService.hpp"
54 #include "utilities/events.hpp"
55 #include "utilities/macros.hpp"
56 #ifdef TARGET_ARCH_x86
57 # include "nativeInst_x86.hpp"
58 # include "vmreg_x86.inline.hpp"
59 #endif
60 #ifdef TARGET_ARCH_sparc
61 # include "nativeInst_sparc.hpp"
62 # include "vmreg_sparc.inline.hpp"
63 #endif
64 #ifdef TARGET_ARCH_zero
65 # include "nativeInst_zero.hpp"
66 # include "vmreg_zero.inline.hpp"
67 #endif
68 #ifdef TARGET_ARCH_arm
69 # include "nativeInst_arm.hpp"
70 # include "vmreg_arm.inline.hpp"
71 #endif
72 #ifdef TARGET_ARCH_ppc
73 # include "nativeInst_ppc.hpp"
74 # include "vmreg_ppc.inline.hpp"
75 #endif
76 #if INCLUDE_ALL_GCS
77 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
78 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
79 #endif // INCLUDE_ALL_GCS
80 #ifdef COMPILER1
81 #include "c1/c1_globals.hpp"
82 #endif
84 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
86 // --------------------------------------------------------------------------------------------------
87 // Implementation of Safepoint begin/end
89 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
90 volatile int SafepointSynchronize::_waiting_to_block = 0;
91 volatile int SafepointSynchronize::_safepoint_counter = 0;
92 int SafepointSynchronize::_current_jni_active_count = 0;
93 long SafepointSynchronize::_end_of_last_safepoint = 0;
94 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
95 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
96 static bool timeout_error_printed = false;
98 // Roll all threads forward to a safepoint and suspend them all
99 void SafepointSynchronize::begin() {
101 Thread* myThread = Thread::current();
102 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
104 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
105 _safepoint_begin_time = os::javaTimeNanos();
106 _ts_of_current_safepoint = tty->time_stamp().seconds();
107 }
109 #if INCLUDE_ALL_GCS
110 if (UseConcMarkSweepGC) {
111 // In the future we should investigate whether CMS can use the
112 // more-general mechanism below. DLD (01/05).
113 ConcurrentMarkSweepThread::synchronize(false);
114 } else if (UseG1GC) {
115 SuspendibleThreadSet::synchronize();
116 }
117 #endif // INCLUDE_ALL_GCS
119 // By getting the Threads_lock, we assure that no threads are about to start or
120 // exit. It is released again in SafepointSynchronize::end().
121 Threads_lock->lock();
123 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
125 int nof_threads = Threads::number_of_threads();
127 if (TraceSafepoint) {
128 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
129 }
131 RuntimeService::record_safepoint_begin();
133 MutexLocker mu(Safepoint_lock);
135 // Reset the count of active JNI critical threads
136 _current_jni_active_count = 0;
138 // Set number of threads to wait for, before we initiate the callbacks
139 _waiting_to_block = nof_threads;
140 TryingToBlock = 0 ;
141 int still_running = nof_threads;
143 // Save the starting time, so that it can be compared to see if this has taken
144 // too long to complete.
145 jlong safepoint_limit_time = 0;
146 timeout_error_printed = false;
148 // PrintSafepointStatisticsTimeout can be specified separately. When
149 // specified, PrintSafepointStatistics will be set to true in
150 // deferred_initialize_stat method. The initialization has to be done
151 // early enough to avoid any races. See bug 6880029 for details.
152 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
153 deferred_initialize_stat();
154 }
156 // Begin the process of bringing the system to a safepoint.
157 // Java threads can be in several different states and are
158 // stopped by different mechanisms:
159 //
160 // 1. Running interpreted
161 // The interpeter dispatch table is changed to force it to
162 // check for a safepoint condition between bytecodes.
163 // 2. Running in native code
164 // When returning from the native code, a Java thread must check
165 // the safepoint _state to see if we must block. If the
166 // VM thread sees a Java thread in native, it does
167 // not wait for this thread to block. The order of the memory
168 // writes and reads of both the safepoint state and the Java
169 // threads state is critical. In order to guarantee that the
170 // memory writes are serialized with respect to each other,
171 // the VM thread issues a memory barrier instruction
172 // (on MP systems). In order to avoid the overhead of issuing
173 // a memory barrier for each Java thread making native calls, each Java
174 // thread performs a write to a single memory page after changing
175 // the thread state. The VM thread performs a sequence of
176 // mprotect OS calls which forces all previous writes from all
177 // Java threads to be serialized. This is done in the
178 // os::serialize_thread_states() call. This has proven to be
179 // much more efficient than executing a membar instruction
180 // on every call to native code.
181 // 3. Running compiled Code
182 // Compiled code reads a global (Safepoint Polling) page that
183 // is set to fault if we are trying to get to a safepoint.
184 // 4. Blocked
185 // A thread which is blocked will not be allowed to return from the
186 // block condition until the safepoint operation is complete.
187 // 5. In VM or Transitioning between states
188 // If a Java thread is currently running in the VM or transitioning
189 // between states, the safepointing code will wait for the thread to
190 // block itself when it attempts transitions to a new state.
191 //
192 _state = _synchronizing;
193 OrderAccess::fence();
195 // Flush all thread states to memory
196 if (!UseMembar) {
197 os::serialize_thread_states();
198 }
200 // Make interpreter safepoint aware
201 Interpreter::notice_safepoints();
203 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
204 // Make polling safepoint aware
205 guarantee (PageArmed == 0, "invariant") ;
206 PageArmed = 1 ;
207 os::make_polling_page_unreadable();
208 }
210 // Consider using active_processor_count() ... but that call is expensive.
211 int ncpus = os::processor_count() ;
213 #ifdef ASSERT
214 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
215 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
216 // Clear the visited flag to ensure that the critical counts are collected properly.
217 cur->set_visited_for_critical_count(false);
218 }
219 #endif // ASSERT
221 if (SafepointTimeout)
222 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
224 // Iterate through all threads until it have been determined how to stop them all at a safepoint
225 unsigned int iterations = 0;
226 int steps = 0 ;
227 while(still_running > 0) {
228 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
229 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
230 ThreadSafepointState *cur_state = cur->safepoint_state();
231 if (cur_state->is_running()) {
232 cur_state->examine_state_of_thread();
233 if (!cur_state->is_running()) {
234 still_running--;
235 // consider adjusting steps downward:
236 // steps = 0
237 // steps -= NNN
238 // steps >>= 1
239 // steps = MIN(steps, 2000-100)
240 // if (iterations != 0) steps -= NNN
241 }
242 if (TraceSafepoint && Verbose) cur_state->print();
243 }
244 }
246 if (PrintSafepointStatistics && iterations == 0) {
247 begin_statistics(nof_threads, still_running);
248 }
250 if (still_running > 0) {
251 // Check for if it takes to long
252 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
253 print_safepoint_timeout(_spinning_timeout);
254 }
256 // Spin to avoid context switching.
257 // There's a tension between allowing the mutators to run (and rendezvous)
258 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
259 // a mutator might otherwise use profitably to reach a safepoint. Excessive
260 // spinning by the VM thread on a saturated system can increase rendezvous latency.
261 // Blocking or yielding incur their own penalties in the form of context switching
262 // and the resultant loss of $ residency.
263 //
264 // Further complicating matters is that yield() does not work as naively expected
265 // on many platforms -- yield() does not guarantee that any other ready threads
266 // will run. As such we revert yield_all() after some number of iterations.
267 // Yield_all() is implemented as a short unconditional sleep on some platforms.
268 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
269 // can actually increase the time it takes the VM thread to detect that a system-wide
270 // stop-the-world safepoint has been reached. In a pathological scenario such as that
271 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
272 // In that case the mutators will be stalled waiting for the safepoint to complete and the
273 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
274 // will eventually wake up and detect that all mutators are safe, at which point
275 // we'll again make progress.
276 //
277 // Beware too that that the VMThread typically runs at elevated priority.
278 // Its default priority is higher than the default mutator priority.
279 // Obviously, this complicates spinning.
280 //
281 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
282 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
283 //
284 // See the comments in synchronizer.cpp for additional remarks on spinning.
285 //
286 // In the future we might:
287 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
288 // This is tricky as the path used by a thread exiting the JVM (say on
289 // on JNI call-out) simply stores into its state field. The burden
290 // is placed on the VM thread, which must poll (spin).
291 // 2. Find something useful to do while spinning. If the safepoint is GC-related
292 // we might aggressively scan the stacks of threads that are already safe.
293 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
294 // If all the mutators are ONPROC there's no reason to sleep or yield.
295 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
296 // 5. Check system saturation. If the system is not fully saturated then
297 // simply spin and avoid sleep/yield.
298 // 6. As still-running mutators rendezvous they could unpark the sleeping
299 // VMthread. This works well for still-running mutators that become
300 // safe. The VMthread must still poll for mutators that call-out.
301 // 7. Drive the policy on time-since-begin instead of iterations.
302 // 8. Consider making the spin duration a function of the # of CPUs:
303 // Spin = (((ncpus-1) * M) + K) + F(still_running)
304 // Alternately, instead of counting iterations of the outer loop
305 // we could count the # of threads visited in the inner loop, above.
306 // 9. On windows consider using the return value from SwitchThreadTo()
307 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
309 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
310 guarantee (PageArmed == 0, "invariant") ;
311 PageArmed = 1 ;
312 os::make_polling_page_unreadable();
313 }
315 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
316 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
317 ++steps ;
318 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
319 SpinPause() ; // MP-Polite spin
320 } else
321 if (steps < DeferThrSuspendLoopCount) {
322 os::NakedYield() ;
323 } else {
324 os::yield_all(steps) ;
325 // Alternately, the VM thread could transiently depress its scheduling priority or
326 // transiently increase the priority of the tardy mutator(s).
327 }
329 iterations ++ ;
330 }
331 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
332 }
333 assert(still_running == 0, "sanity check");
335 if (PrintSafepointStatistics) {
336 update_statistics_on_spin_end();
337 }
339 // wait until all threads are stopped
340 while (_waiting_to_block > 0) {
341 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
342 if (!SafepointTimeout || timeout_error_printed) {
343 Safepoint_lock->wait(true); // true, means with no safepoint checks
344 } else {
345 // Compute remaining time
346 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
348 // If there is no remaining time, then there is an error
349 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
350 print_safepoint_timeout(_blocking_timeout);
351 }
352 }
353 }
354 assert(_waiting_to_block == 0, "sanity check");
356 #ifndef PRODUCT
357 if (SafepointTimeout) {
358 jlong current_time = os::javaTimeNanos();
359 if (safepoint_limit_time < current_time) {
360 tty->print_cr("# SafepointSynchronize: Finished after "
361 INT64_FORMAT_W(6) " ms",
362 ((current_time - safepoint_limit_time) / MICROUNITS +
363 SafepointTimeoutDelay));
364 }
365 }
366 #endif
368 assert((_safepoint_counter & 0x1) == 0, "must be even");
369 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
370 _safepoint_counter ++;
372 // Record state
373 _state = _synchronized;
375 OrderAccess::fence();
377 #ifdef ASSERT
378 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
379 // make sure all the threads were visited
380 assert(cur->was_visited_for_critical_count(), "missed a thread");
381 }
382 #endif // ASSERT
384 // Update the count of active JNI critical regions
385 GC_locker::set_jni_lock_count(_current_jni_active_count);
387 if (TraceSafepoint) {
388 VM_Operation *op = VMThread::vm_operation();
389 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
390 }
392 RuntimeService::record_safepoint_synchronized();
393 if (PrintSafepointStatistics) {
394 update_statistics_on_sync_end(os::javaTimeNanos());
395 }
397 // Call stuff that needs to be run when a safepoint is just about to be completed
398 do_cleanup_tasks();
400 if (PrintSafepointStatistics) {
401 // Record how much time spend on the above cleanup tasks
402 update_statistics_on_cleanup_end(os::javaTimeNanos());
403 }
404 }
406 // Wake up all threads, so they are ready to resume execution after the safepoint
407 // operation has been carried out
408 void SafepointSynchronize::end() {
410 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
411 assert((_safepoint_counter & 0x1) == 1, "must be odd");
412 _safepoint_counter ++;
413 // memory fence isn't required here since an odd _safepoint_counter
414 // value can do no harm and a fence is issued below anyway.
416 DEBUG_ONLY(Thread* myThread = Thread::current();)
417 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
419 if (PrintSafepointStatistics) {
420 end_statistics(os::javaTimeNanos());
421 }
423 #ifdef ASSERT
424 // A pending_exception cannot be installed during a safepoint. The threads
425 // may install an async exception after they come back from a safepoint into
426 // pending_exception after they unblock. But that should happen later.
427 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
428 assert (!(cur->has_pending_exception() &&
429 cur->safepoint_state()->is_at_poll_safepoint()),
430 "safepoint installed a pending exception");
431 }
432 #endif // ASSERT
434 if (PageArmed) {
435 // Make polling safepoint aware
436 os::make_polling_page_readable();
437 PageArmed = 0 ;
438 }
440 // Remove safepoint check from interpreter
441 Interpreter::ignore_safepoints();
443 {
444 MutexLocker mu(Safepoint_lock);
446 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
448 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
449 // when they get restarted.
450 _state = _not_synchronized;
451 OrderAccess::fence();
453 if (TraceSafepoint) {
454 tty->print_cr("Leaving safepoint region");
455 }
457 // Start suspended threads
458 for(JavaThread *current = Threads::first(); current; current = current->next()) {
459 // A problem occurring on Solaris is when attempting to restart threads
460 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
461 // to the next one (since it has been running the longest). We then have
462 // to wait for a cpu to become available before we can continue restarting
463 // threads.
464 // FIXME: This causes the performance of the VM to degrade when active and with
465 // large numbers of threads. Apparently this is due to the synchronous nature
466 // of suspending threads.
467 //
468 // TODO-FIXME: the comments above are vestigial and no longer apply.
469 // Furthermore, using solaris' schedctl in this particular context confers no benefit
470 if (VMThreadHintNoPreempt) {
471 os::hint_no_preempt();
472 }
473 ThreadSafepointState* cur_state = current->safepoint_state();
474 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
475 cur_state->restart();
476 assert(cur_state->is_running(), "safepoint state has not been reset");
477 }
479 RuntimeService::record_safepoint_end();
481 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
482 // blocked in signal_thread_blocked
483 Threads_lock->unlock();
485 }
486 #if INCLUDE_ALL_GCS
487 // If there are any concurrent GC threads resume them.
488 if (UseConcMarkSweepGC) {
489 ConcurrentMarkSweepThread::desynchronize(false);
490 } else if (UseG1GC) {
491 SuspendibleThreadSet::desynchronize();
492 }
493 #endif // INCLUDE_ALL_GCS
494 // record this time so VMThread can keep track how much time has elasped
495 // since last safepoint.
496 _end_of_last_safepoint = os::javaTimeMillis();
497 }
499 bool SafepointSynchronize::is_cleanup_needed() {
500 // Need a safepoint if some inline cache buffers is non-empty
501 if (!InlineCacheBuffer::is_empty()) return true;
502 return false;
503 }
507 // Various cleaning tasks that should be done periodically at safepoints
508 void SafepointSynchronize::do_cleanup_tasks() {
509 {
510 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
511 ObjectSynchronizer::deflate_idle_monitors();
512 }
514 {
515 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
516 InlineCacheBuffer::update_inline_caches();
517 }
518 {
519 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
520 CompilationPolicy::policy()->do_safepoint_work();
521 }
523 {
524 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
525 NMethodSweeper::mark_active_nmethods();
526 }
528 if (SymbolTable::needs_rehashing()) {
529 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
530 SymbolTable::rehash_table();
531 }
533 if (StringTable::needs_rehashing()) {
534 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
535 StringTable::rehash_table();
536 }
538 // rotate log files?
539 if (UseGCLogFileRotation) {
540 TraceTime t8("rotating gc logs", TraceSafepointCleanupTime);
541 gclog_or_tty->rotate_log(false);
542 }
544 {
545 // CMS delays purging the CLDG until the beginning of the next safepoint and to
546 // make sure concurrent sweep is done
547 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
548 ClassLoaderDataGraph::purge_if_needed();
549 }
550 }
553 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
554 switch(state) {
555 case _thread_in_native:
556 // native threads are safe if they have no java stack or have walkable stack
557 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
559 // blocked threads should have already have walkable stack
560 case _thread_blocked:
561 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
562 return true;
564 default:
565 return false;
566 }
567 }
570 // See if the thread is running inside a lazy critical native and
571 // update the thread critical count if so. Also set a suspend flag to
572 // cause the native wrapper to return into the JVM to do the unlock
573 // once the native finishes.
574 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
575 if (state == _thread_in_native &&
576 thread->has_last_Java_frame() &&
577 thread->frame_anchor()->walkable()) {
578 // This thread might be in a critical native nmethod so look at
579 // the top of the stack and increment the critical count if it
580 // is.
581 frame wrapper_frame = thread->last_frame();
582 CodeBlob* stub_cb = wrapper_frame.cb();
583 if (stub_cb != NULL &&
584 stub_cb->is_nmethod() &&
585 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
586 // A thread could potentially be in a critical native across
587 // more than one safepoint, so only update the critical state on
588 // the first one. When it returns it will perform the unlock.
589 if (!thread->do_critical_native_unlock()) {
590 #ifdef ASSERT
591 if (!thread->in_critical()) {
592 GC_locker::increment_debug_jni_lock_count();
593 }
594 #endif
595 thread->enter_critical();
596 // Make sure the native wrapper calls back on return to
597 // perform the needed critical unlock.
598 thread->set_critical_native_unlock();
599 }
600 }
601 }
602 }
606 // -------------------------------------------------------------------------------------------------------
607 // Implementation of Safepoint callback point
609 void SafepointSynchronize::block(JavaThread *thread) {
610 assert(thread != NULL, "thread must be set");
611 assert(thread->is_Java_thread(), "not a Java thread");
613 // Threads shouldn't block if they are in the middle of printing, but...
614 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
616 // Only bail from the block() call if the thread is gone from the
617 // thread list; starting to exit should still block.
618 if (thread->is_terminated()) {
619 // block current thread if we come here from native code when VM is gone
620 thread->block_if_vm_exited();
622 // otherwise do nothing
623 return;
624 }
626 JavaThreadState state = thread->thread_state();
627 thread->frame_anchor()->make_walkable(thread);
629 // Check that we have a valid thread_state at this point
630 switch(state) {
631 case _thread_in_vm_trans:
632 case _thread_in_Java: // From compiled code
634 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
635 // we pretend we are still in the VM.
636 thread->set_thread_state(_thread_in_vm);
638 if (is_synchronizing()) {
639 Atomic::inc (&TryingToBlock) ;
640 }
642 // We will always be holding the Safepoint_lock when we are examine the state
643 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
644 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
645 Safepoint_lock->lock_without_safepoint_check();
646 if (is_synchronizing()) {
647 // Decrement the number of threads to wait for and signal vm thread
648 assert(_waiting_to_block > 0, "sanity check");
649 _waiting_to_block--;
650 thread->safepoint_state()->set_has_called_back(true);
652 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
653 if (thread->in_critical()) {
654 // Notice that this thread is in a critical section
655 increment_jni_active_count();
656 }
658 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
659 if (_waiting_to_block == 0) {
660 Safepoint_lock->notify_all();
661 }
662 }
664 // We transition the thread to state _thread_blocked here, but
665 // we can't do our usual check for external suspension and then
666 // self-suspend after the lock_without_safepoint_check() call
667 // below because we are often called during transitions while
668 // we hold different locks. That would leave us suspended while
669 // holding a resource which results in deadlocks.
670 thread->set_thread_state(_thread_blocked);
671 Safepoint_lock->unlock();
673 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
674 // the entire safepoint, the threads will all line up here during the safepoint.
675 Threads_lock->lock_without_safepoint_check();
676 // restore original state. This is important if the thread comes from compiled code, so it
677 // will continue to execute with the _thread_in_Java state.
678 thread->set_thread_state(state);
679 Threads_lock->unlock();
680 break;
682 case _thread_in_native_trans:
683 case _thread_blocked_trans:
684 case _thread_new_trans:
685 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
686 thread->print_thread_state();
687 fatal("Deadlock in safepoint code. "
688 "Should have called back to the VM before blocking.");
689 }
691 // We transition the thread to state _thread_blocked here, but
692 // we can't do our usual check for external suspension and then
693 // self-suspend after the lock_without_safepoint_check() call
694 // below because we are often called during transitions while
695 // we hold different locks. That would leave us suspended while
696 // holding a resource which results in deadlocks.
697 thread->set_thread_state(_thread_blocked);
699 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
700 // the safepoint code might still be waiting for it to block. We need to change the state here,
701 // so it can see that it is at a safepoint.
703 // Block until the safepoint operation is completed.
704 Threads_lock->lock_without_safepoint_check();
706 // Restore state
707 thread->set_thread_state(state);
709 Threads_lock->unlock();
710 break;
712 default:
713 fatal(err_msg("Illegal threadstate encountered: %d", state));
714 }
716 // Check for pending. async. exceptions or suspends - except if the
717 // thread was blocked inside the VM. has_special_runtime_exit_condition()
718 // is called last since it grabs a lock and we only want to do that when
719 // we must.
720 //
721 // Note: we never deliver an async exception at a polling point as the
722 // compiler may not have an exception handler for it. The polling
723 // code will notice the async and deoptimize and the exception will
724 // be delivered. (Polling at a return point is ok though). Sure is
725 // a lot of bother for a deprecated feature...
726 //
727 // We don't deliver an async exception if the thread state is
728 // _thread_in_native_trans so JNI functions won't be called with
729 // a surprising pending exception. If the thread state is going back to java,
730 // async exception is checked in check_special_condition_for_native_trans().
732 if (state != _thread_blocked_trans &&
733 state != _thread_in_vm_trans &&
734 thread->has_special_runtime_exit_condition()) {
735 thread->handle_special_runtime_exit_condition(
736 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
737 }
738 }
740 // ------------------------------------------------------------------------------------------------------
741 // Exception handlers
744 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
745 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
746 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
747 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
749 if (ShowSafepointMsgs) {
750 tty->print("handle_polling_page_exception: ");
751 }
753 if (PrintSafepointStatistics) {
754 inc_page_trap_count();
755 }
757 ThreadSafepointState* state = thread->safepoint_state();
759 state->handle_polling_page_exception();
760 }
763 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
764 if (!timeout_error_printed) {
765 timeout_error_printed = true;
766 // Print out the thread infor which didn't reach the safepoint for debugging
767 // purposes (useful when there are lots of threads in the debugger).
768 tty->cr();
769 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
770 if (reason == _spinning_timeout) {
771 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
772 } else if (reason == _blocking_timeout) {
773 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
774 }
776 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
777 ThreadSafepointState *cur_state;
778 ResourceMark rm;
779 for(JavaThread *cur_thread = Threads::first(); cur_thread;
780 cur_thread = cur_thread->next()) {
781 cur_state = cur_thread->safepoint_state();
783 if (cur_thread->thread_state() != _thread_blocked &&
784 ((reason == _spinning_timeout && cur_state->is_running()) ||
785 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
786 tty->print("# ");
787 cur_thread->print();
788 tty->cr();
789 }
790 }
791 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
792 }
794 // To debug the long safepoint, specify both AbortVMOnSafepointTimeout &
795 // ShowMessageBoxOnError.
796 if (AbortVMOnSafepointTimeout) {
797 char msg[1024];
798 VM_Operation *op = VMThread::vm_operation();
799 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
800 SafepointTimeoutDelay,
801 op != NULL ? op->name() : "no vm operation");
802 fatal(msg);
803 }
804 }
807 // -------------------------------------------------------------------------------------------------------
808 // Implementation of ThreadSafepointState
810 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
811 _thread = thread;
812 _type = _running;
813 _has_called_back = false;
814 _at_poll_safepoint = false;
815 }
817 void ThreadSafepointState::create(JavaThread *thread) {
818 ThreadSafepointState *state = new ThreadSafepointState(thread);
819 thread->set_safepoint_state(state);
820 }
822 void ThreadSafepointState::destroy(JavaThread *thread) {
823 if (thread->safepoint_state()) {
824 delete(thread->safepoint_state());
825 thread->set_safepoint_state(NULL);
826 }
827 }
829 void ThreadSafepointState::examine_state_of_thread() {
830 assert(is_running(), "better be running or just have hit safepoint poll");
832 JavaThreadState state = _thread->thread_state();
834 // Save the state at the start of safepoint processing.
835 _orig_thread_state = state;
837 // Check for a thread that is suspended. Note that thread resume tries
838 // to grab the Threads_lock which we own here, so a thread cannot be
839 // resumed during safepoint synchronization.
841 // We check to see if this thread is suspended without locking to
842 // avoid deadlocking with a third thread that is waiting for this
843 // thread to be suspended. The third thread can notice the safepoint
844 // that we're trying to start at the beginning of its SR_lock->wait()
845 // call. If that happens, then the third thread will block on the
846 // safepoint while still holding the underlying SR_lock. We won't be
847 // able to get the SR_lock and we'll deadlock.
848 //
849 // We don't need to grab the SR_lock here for two reasons:
850 // 1) The suspend flags are both volatile and are set with an
851 // Atomic::cmpxchg() call so we should see the suspended
852 // state right away.
853 // 2) We're being called from the safepoint polling loop; if
854 // we don't see the suspended state on this iteration, then
855 // we'll come around again.
856 //
857 bool is_suspended = _thread->is_ext_suspended();
858 if (is_suspended) {
859 roll_forward(_at_safepoint);
860 return;
861 }
863 // Some JavaThread states have an initial safepoint state of
864 // running, but are actually at a safepoint. We will happily
865 // agree and update the safepoint state here.
866 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
867 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
868 roll_forward(_at_safepoint);
869 return;
870 }
872 if (state == _thread_in_vm) {
873 roll_forward(_call_back);
874 return;
875 }
877 // All other thread states will continue to run until they
878 // transition and self-block in state _blocked
879 // Safepoint polling in compiled code causes the Java threads to do the same.
880 // Note: new threads may require a malloc so they must be allowed to finish
882 assert(is_running(), "examine_state_of_thread on non-running thread");
883 return;
884 }
886 // Returns true is thread could not be rolled forward at present position.
887 void ThreadSafepointState::roll_forward(suspend_type type) {
888 _type = type;
890 switch(_type) {
891 case _at_safepoint:
892 SafepointSynchronize::signal_thread_at_safepoint();
893 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
894 if (_thread->in_critical()) {
895 // Notice that this thread is in a critical section
896 SafepointSynchronize::increment_jni_active_count();
897 }
898 break;
900 case _call_back:
901 set_has_called_back(false);
902 break;
904 case _running:
905 default:
906 ShouldNotReachHere();
907 }
908 }
910 void ThreadSafepointState::restart() {
911 switch(type()) {
912 case _at_safepoint:
913 case _call_back:
914 break;
916 case _running:
917 default:
918 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
919 _thread, _type);
920 _thread->print();
921 ShouldNotReachHere();
922 }
923 _type = _running;
924 set_has_called_back(false);
925 }
928 void ThreadSafepointState::print_on(outputStream *st) const {
929 const char *s = NULL;
931 switch(_type) {
932 case _running : s = "_running"; break;
933 case _at_safepoint : s = "_at_safepoint"; break;
934 case _call_back : s = "_call_back"; break;
935 default:
936 ShouldNotReachHere();
937 }
939 st->print_cr("Thread: " INTPTR_FORMAT
940 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
941 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
942 _at_poll_safepoint);
944 _thread->print_thread_state_on(st);
945 }
948 // ---------------------------------------------------------------------------------------------------------------------
950 // Block the thread at the safepoint poll or poll return.
951 void ThreadSafepointState::handle_polling_page_exception() {
953 // Check state. block() will set thread state to thread_in_vm which will
954 // cause the safepoint state _type to become _call_back.
955 assert(type() == ThreadSafepointState::_running,
956 "polling page exception on thread not running state");
958 // Step 1: Find the nmethod from the return address
959 if (ShowSafepointMsgs && Verbose) {
960 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
961 }
962 address real_return_addr = thread()->saved_exception_pc();
964 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
965 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
966 nmethod* nm = (nmethod*)cb;
968 // Find frame of caller
969 frame stub_fr = thread()->last_frame();
970 CodeBlob* stub_cb = stub_fr.cb();
971 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
972 RegisterMap map(thread(), true);
973 frame caller_fr = stub_fr.sender(&map);
975 // Should only be poll_return or poll
976 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
978 // This is a poll immediately before a return. The exception handling code
979 // has already had the effect of causing the return to occur, so the execution
980 // will continue immediately after the call. In addition, the oopmap at the
981 // return point does not mark the return value as an oop (if it is), so
982 // it needs a handle here to be updated.
983 if( nm->is_at_poll_return(real_return_addr) ) {
984 // See if return type is an oop.
985 bool return_oop = nm->method()->is_returning_oop();
986 Handle return_value;
987 if (return_oop) {
988 // The oop result has been saved on the stack together with all
989 // the other registers. In order to preserve it over GCs we need
990 // to keep it in a handle.
991 oop result = caller_fr.saved_oop_result(&map);
992 assert(result == NULL || result->is_oop(), "must be oop");
993 return_value = Handle(thread(), result);
994 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
995 }
997 // Block the thread
998 SafepointSynchronize::block(thread());
1000 // restore oop result, if any
1001 if (return_oop) {
1002 caller_fr.set_saved_oop_result(&map, return_value());
1003 }
1004 }
1006 // This is a safepoint poll. Verify the return address and block.
1007 else {
1008 set_at_poll_safepoint(true);
1010 // verify the blob built the "return address" correctly
1011 assert(real_return_addr == caller_fr.pc(), "must match");
1013 // Block the thread
1014 SafepointSynchronize::block(thread());
1015 set_at_poll_safepoint(false);
1017 // If we have a pending async exception deoptimize the frame
1018 // as otherwise we may never deliver it.
1019 if (thread()->has_async_condition()) {
1020 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1021 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1022 }
1024 // If an exception has been installed we must check for a pending deoptimization
1025 // Deoptimize frame if exception has been thrown.
1027 if (thread()->has_pending_exception() ) {
1028 RegisterMap map(thread(), true);
1029 frame caller_fr = stub_fr.sender(&map);
1030 if (caller_fr.is_deoptimized_frame()) {
1031 // The exception patch will destroy registers that are still
1032 // live and will be needed during deoptimization. Defer the
1033 // Async exception should have defered the exception until the
1034 // next safepoint which will be detected when we get into
1035 // the interpreter so if we have an exception now things
1036 // are messed up.
1038 fatal("Exception installed and deoptimization is pending");
1039 }
1040 }
1041 }
1042 }
1045 //
1046 // Statistics & Instrumentations
1047 //
1048 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1049 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1050 int SafepointSynchronize::_cur_stat_index = 0;
1051 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1052 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1053 jlong SafepointSynchronize::_max_sync_time = 0;
1054 jlong SafepointSynchronize::_max_vmop_time = 0;
1055 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1057 static jlong cleanup_end_time = 0;
1058 static bool need_to_track_page_armed_status = false;
1059 static bool init_done = false;
1061 // Helper method to print the header.
1062 static void print_header() {
1063 tty->print(" vmop "
1064 "[threads: total initially_running wait_to_block] ");
1065 tty->print("[time: spin block sync cleanup vmop] ");
1067 // no page armed status printed out if it is always armed.
1068 if (need_to_track_page_armed_status) {
1069 tty->print("page_armed ");
1070 }
1072 tty->print_cr("page_trap_count");
1073 }
1075 void SafepointSynchronize::deferred_initialize_stat() {
1076 if (init_done) return;
1078 if (PrintSafepointStatisticsCount <= 0) {
1079 fatal("Wrong PrintSafepointStatisticsCount");
1080 }
1082 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1083 // be printed right away, in which case, _safepoint_stats will regress to
1084 // a single element array. Otherwise, it is a circular ring buffer with default
1085 // size of PrintSafepointStatisticsCount.
1086 int stats_array_size;
1087 if (PrintSafepointStatisticsTimeout > 0) {
1088 stats_array_size = 1;
1089 PrintSafepointStatistics = true;
1090 } else {
1091 stats_array_size = PrintSafepointStatisticsCount;
1092 }
1093 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1094 * sizeof(SafepointStats), mtInternal);
1095 guarantee(_safepoint_stats != NULL,
1096 "not enough memory for safepoint instrumentation data");
1098 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1099 need_to_track_page_armed_status = true;
1100 }
1101 init_done = true;
1102 }
1104 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1105 assert(init_done, "safepoint statistics array hasn't been initialized");
1106 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1108 spstat->_time_stamp = _ts_of_current_safepoint;
1110 VM_Operation *op = VMThread::vm_operation();
1111 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1112 if (op != NULL) {
1113 _safepoint_reasons[spstat->_vmop_type]++;
1114 }
1116 spstat->_nof_total_threads = nof_threads;
1117 spstat->_nof_initial_running_threads = nof_running;
1118 spstat->_nof_threads_hit_page_trap = 0;
1120 // Records the start time of spinning. The real time spent on spinning
1121 // will be adjusted when spin is done. Same trick is applied for time
1122 // spent on waiting for threads to block.
1123 if (nof_running != 0) {
1124 spstat->_time_to_spin = os::javaTimeNanos();
1125 } else {
1126 spstat->_time_to_spin = 0;
1127 }
1128 }
1130 void SafepointSynchronize::update_statistics_on_spin_end() {
1131 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1133 jlong cur_time = os::javaTimeNanos();
1135 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1136 if (spstat->_nof_initial_running_threads != 0) {
1137 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1138 }
1140 if (need_to_track_page_armed_status) {
1141 spstat->_page_armed = (PageArmed == 1);
1142 }
1144 // Records the start time of waiting for to block. Updated when block is done.
1145 if (_waiting_to_block != 0) {
1146 spstat->_time_to_wait_to_block = cur_time;
1147 } else {
1148 spstat->_time_to_wait_to_block = 0;
1149 }
1150 }
1152 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1153 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1155 if (spstat->_nof_threads_wait_to_block != 0) {
1156 spstat->_time_to_wait_to_block = end_time -
1157 spstat->_time_to_wait_to_block;
1158 }
1160 // Records the end time of sync which will be used to calculate the total
1161 // vm operation time. Again, the real time spending in syncing will be deducted
1162 // from the start of the sync time later when end_statistics is called.
1163 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1164 if (spstat->_time_to_sync > _max_sync_time) {
1165 _max_sync_time = spstat->_time_to_sync;
1166 }
1168 spstat->_time_to_do_cleanups = end_time;
1169 }
1171 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1172 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1174 // Record how long spent in cleanup tasks.
1175 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1177 cleanup_end_time = end_time;
1178 }
1180 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1181 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1183 // Update the vm operation time.
1184 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1185 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1186 _max_vmop_time = spstat->_time_to_exec_vmop;
1187 }
1188 // Only the sync time longer than the specified
1189 // PrintSafepointStatisticsTimeout will be printed out right away.
1190 // By default, it is -1 meaning all samples will be put into the list.
1191 if ( PrintSafepointStatisticsTimeout > 0) {
1192 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1193 print_statistics();
1194 }
1195 } else {
1196 // The safepoint statistics will be printed out when the _safepoin_stats
1197 // array fills up.
1198 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1199 print_statistics();
1200 _cur_stat_index = 0;
1201 } else {
1202 _cur_stat_index++;
1203 }
1204 }
1205 }
1207 void SafepointSynchronize::print_statistics() {
1208 SafepointStats* sstats = _safepoint_stats;
1210 for (int index = 0; index <= _cur_stat_index; index++) {
1211 if (index % 30 == 0) {
1212 print_header();
1213 }
1214 sstats = &_safepoint_stats[index];
1215 tty->print("%.3f: ", sstats->_time_stamp);
1216 tty->print("%-26s ["
1217 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1218 " ] ",
1219 sstats->_vmop_type == -1 ? "no vm operation" :
1220 VM_Operation::name(sstats->_vmop_type),
1221 sstats->_nof_total_threads,
1222 sstats->_nof_initial_running_threads,
1223 sstats->_nof_threads_wait_to_block);
1224 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1225 tty->print(" ["
1226 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1227 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1228 INT64_FORMAT_W(6) " ] ",
1229 sstats->_time_to_spin / MICROUNITS,
1230 sstats->_time_to_wait_to_block / MICROUNITS,
1231 sstats->_time_to_sync / MICROUNITS,
1232 sstats->_time_to_do_cleanups / MICROUNITS,
1233 sstats->_time_to_exec_vmop / MICROUNITS);
1235 if (need_to_track_page_armed_status) {
1236 tty->print(INT32_FORMAT " ", sstats->_page_armed);
1237 }
1238 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
1239 }
1240 }
1242 // This method will be called when VM exits. It will first call
1243 // print_statistics to print out the rest of the sampling. Then
1244 // it tries to summarize the sampling.
1245 void SafepointSynchronize::print_stat_on_exit() {
1246 if (_safepoint_stats == NULL) return;
1248 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1250 // During VM exit, end_statistics may not get called and in that
1251 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1252 // don't print it out.
1253 // Approximate the vm op time.
1254 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1255 os::javaTimeNanos() - cleanup_end_time;
1257 if ( PrintSafepointStatisticsTimeout < 0 ||
1258 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1259 print_statistics();
1260 }
1261 tty->cr();
1263 // Print out polling page sampling status.
1264 if (!need_to_track_page_armed_status) {
1265 if (UseCompilerSafepoints) {
1266 tty->print_cr("Polling page always armed");
1267 }
1268 } else {
1269 tty->print_cr("Defer polling page loop count = %d\n",
1270 DeferPollingPageLoopCount);
1271 }
1273 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1274 if (_safepoint_reasons[index] != 0) {
1275 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1276 _safepoint_reasons[index]);
1277 }
1278 }
1280 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1281 _coalesced_vmop_count);
1282 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1283 _max_sync_time / MICROUNITS);
1284 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1285 INT64_FORMAT_W(5) " ms",
1286 _max_vmop_time / MICROUNITS);
1287 }
1289 // ------------------------------------------------------------------------------------------------
1290 // Non-product code
1292 #ifndef PRODUCT
1294 void SafepointSynchronize::print_state() {
1295 if (_state == _not_synchronized) {
1296 tty->print_cr("not synchronized");
1297 } else if (_state == _synchronizing || _state == _synchronized) {
1298 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1299 "synchronized");
1301 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1302 cur->safepoint_state()->print();
1303 }
1304 }
1305 }
1307 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1308 if (ShowSafepointMsgs) {
1309 va_list ap;
1310 va_start(ap, format);
1311 tty->vprint_cr(format, ap);
1312 va_end(ap);
1313 }
1314 }
1316 #endif // !PRODUCT