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/stringTable.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/shared/collectedHeap.hpp"
34 #include "gc/shared/gcLocker.inline.hpp"
35 #include "interpreter/interpreter.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "memory/universe.inline.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "oops/symbol.hpp"
40 #include "runtime/atomic.inline.hpp"
41 #include "runtime/compilationPolicy.hpp"
42 #include "runtime/deoptimization.hpp"
43 #include "runtime/frame.inline.hpp"
44 #include "runtime/interfaceSupport.hpp"
45 #include "runtime/mutexLocker.hpp"
46 #include "runtime/orderAccess.inline.hpp"
47 #include "runtime/osThread.hpp"
48 #include "runtime/safepoint.hpp"
49 #include "runtime/signature.hpp"
50 #include "runtime/stubCodeGenerator.hpp"
51 #include "runtime/stubRoutines.hpp"
52 #include "runtime/sweeper.hpp"
53 #include "runtime/synchronizer.hpp"
54 #include "runtime/thread.inline.hpp"
55 #include "services/runtimeService.hpp"
56 #include "utilities/events.hpp"
57 #include "utilities/macros.hpp"
58 #if INCLUDE_ALL_GCS
59 #include "gc/cms/concurrentMarkSweepThread.hpp"
60 #include "gc/g1/suspendibleThreadSet.hpp"
61 #endif // INCLUDE_ALL_GCS
62 #ifdef COMPILER1
63 #include "c1/c1_globals.hpp"
64 #endif
65
66 // --------------------------------------------------------------------------------------------------
67 // Implementation of Safepoint begin/end
68
69 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
70 volatile int SafepointSynchronize::_waiting_to_block = 0;
71 volatile int SafepointSynchronize::_safepoint_counter = 0;
72 int SafepointSynchronize::_current_jni_active_count = 0;
73 long SafepointSynchronize::_end_of_last_safepoint = 0;
74 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
75 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
76 static bool timeout_error_printed = false;
77
78 // Roll all threads forward to a safepoint and suspend them all
79 void SafepointSynchronize::begin() {
80
81 Thread* myThread = Thread::current();
82 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
83
84 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
85 _safepoint_begin_time = os::javaTimeNanos();
86 _ts_of_current_safepoint = tty->time_stamp().seconds();
87 }
88
89 #if INCLUDE_ALL_GCS
90 if (UseConcMarkSweepGC) {
91 // In the future we should investigate whether CMS can use the
92 // more-general mechanism below. DLD (01/05).
93 ConcurrentMarkSweepThread::synchronize(false);
94 } else if (UseG1GC) {
95 SuspendibleThreadSet::synchronize();
96 }
97 #endif // INCLUDE_ALL_GCS
98
99 // By getting the Threads_lock, we assure that no threads are about to start or
100 // exit. It is released again in SafepointSynchronize::end().
101 Threads_lock->lock();
102
103 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
104
105 int nof_threads = Threads::number_of_threads();
106
107 if (TraceSafepoint) {
108 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
109 }
110
111 RuntimeService::record_safepoint_begin();
112
113 MutexLocker mu(Safepoint_lock);
114
115 // Reset the count of active JNI critical threads
116 _current_jni_active_count = 0;
117
118 // Set number of threads to wait for, before we initiate the callbacks
119 _waiting_to_block = nof_threads;
120 TryingToBlock = 0 ;
121 int still_running = nof_threads;
122
123 // Save the starting time, so that it can be compared to see if this has taken
124 // too long to complete.
125 jlong safepoint_limit_time;
126 timeout_error_printed = false;
127
128 // PrintSafepointStatisticsTimeout can be specified separately. When
129 // specified, PrintSafepointStatistics will be set to true in
130 // deferred_initialize_stat method. The initialization has to be done
131 // early enough to avoid any races. See bug 6880029 for details.
132 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
133 deferred_initialize_stat();
134 }
135
136 // Begin the process of bringing the system to a safepoint.
137 // Java threads can be in several different states and are
138 // stopped by different mechanisms:
139 //
140 // 1. Running interpreted
141 // The interpreter dispatch table is changed to force it to
142 // check for a safepoint condition between bytecodes.
143 // 2. Running in native code
144 // When returning from the native code, a Java thread must check
145 // the safepoint _state to see if we must block. If the
146 // VM thread sees a Java thread in native, it does
147 // not wait for this thread to block. The order of the memory
148 // writes and reads of both the safepoint state and the Java
149 // threads state is critical. In order to guarantee that the
150 // memory writes are serialized with respect to each other,
151 // the VM thread issues a memory barrier instruction
152 // (on MP systems). In order to avoid the overhead of issuing
153 // a memory barrier for each Java thread making native calls, each Java
154 // thread performs a write to a single memory page after changing
155 // the thread state. The VM thread performs a sequence of
156 // mprotect OS calls which forces all previous writes from all
157 // Java threads to be serialized. This is done in the
158 // os::serialize_thread_states() call. This has proven to be
159 // much more efficient than executing a membar instruction
160 // on every call to native code.
161 // 3. Running compiled Code
162 // Compiled code reads a global (Safepoint Polling) page that
163 // is set to fault if we are trying to get to a safepoint.
164 // 4. Blocked
165 // A thread which is blocked will not be allowed to return from the
166 // block condition until the safepoint operation is complete.
167 // 5. In VM or Transitioning between states
168 // If a Java thread is currently running in the VM or transitioning
169 // between states, the safepointing code will wait for the thread to
170 // block itself when it attempts transitions to a new state.
171 //
172 _state = _synchronizing;
173 OrderAccess::fence();
174
175 // Flush all thread states to memory
176 if (!UseMembar) {
177 os::serialize_thread_states();
178 }
179
180 // Make interpreter safepoint aware
181 Interpreter::notice_safepoints();
182
183 if (DeferPollingPageLoopCount < 0) {
184 // Make polling safepoint aware
185 guarantee (PageArmed == 0, "invariant") ;
186 PageArmed = 1 ;
187 os::make_polling_page_unreadable();
188 }
189
190 // Consider using active_processor_count() ... but that call is expensive.
191 int ncpus = os::processor_count() ;
192
193 #ifdef ASSERT
194 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
195 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
196 // Clear the visited flag to ensure that the critical counts are collected properly.
197 cur->set_visited_for_critical_count(false);
198 }
199 #endif // ASSERT
200
201 if (SafepointTimeout)
202 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
203
204 // Iterate through all threads until it have been determined how to stop them all at a safepoint
205 unsigned int iterations = 0;
206 int steps = 0 ;
207 while(still_running > 0) {
208 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
209 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
210 ThreadSafepointState *cur_state = cur->safepoint_state();
211 if (cur_state->is_running()) {
212 cur_state->examine_state_of_thread();
213 if (!cur_state->is_running()) {
214 still_running--;
215 // consider adjusting steps downward:
216 // steps = 0
217 // steps -= NNN
218 // steps >>= 1
219 // steps = MIN(steps, 2000-100)
220 // if (iterations != 0) steps -= NNN
221 }
222 if (TraceSafepoint && Verbose) cur_state->print();
223 }
224 }
225
226 if (PrintSafepointStatistics && iterations == 0) {
227 begin_statistics(nof_threads, still_running);
228 }
229
230 if (still_running > 0) {
231 // Check for if it takes to long
232 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
233 print_safepoint_timeout(_spinning_timeout);
234 }
235
236 // Spin to avoid context switching.
237 // There's a tension between allowing the mutators to run (and rendezvous)
238 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
239 // a mutator might otherwise use profitably to reach a safepoint. Excessive
240 // spinning by the VM thread on a saturated system can increase rendezvous latency.
241 // Blocking or yielding incur their own penalties in the form of context switching
242 // and the resultant loss of $ residency.
243 //
244 // Further complicating matters is that yield() does not work as naively expected
245 // on many platforms -- yield() does not guarantee that any other ready threads
246 // will run. As such we revert to naked_short_sleep() after some number of iterations.
247 // nakes_short_sleep() is implemented as a short unconditional sleep.
248 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
249 // can actually increase the time it takes the VM thread to detect that a system-wide
250 // stop-the-world safepoint has been reached. In a pathological scenario such as that
251 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
252 // In that case the mutators will be stalled waiting for the safepoint to complete and the
253 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
254 // will eventually wake up and detect that all mutators are safe, at which point
255 // we'll again make progress.
256 //
257 // Beware too that that the VMThread typically runs at elevated priority.
258 // Its default priority is higher than the default mutator priority.
259 // Obviously, this complicates spinning.
260 //
261 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
262 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
263 //
264 // See the comments in synchronizer.cpp for additional remarks on spinning.
265 //
266 // In the future we might:
267 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
268 // This is tricky as the path used by a thread exiting the JVM (say on
269 // on JNI call-out) simply stores into its state field. The burden
270 // is placed on the VM thread, which must poll (spin).
271 // 2. Find something useful to do while spinning. If the safepoint is GC-related
272 // we might aggressively scan the stacks of threads that are already safe.
273 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
274 // If all the mutators are ONPROC there's no reason to sleep or yield.
275 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
276 // 5. Check system saturation. If the system is not fully saturated then
277 // simply spin and avoid sleep/yield.
278 // 6. As still-running mutators rendezvous they could unpark the sleeping
279 // VMthread. This works well for still-running mutators that become
280 // safe. The VMthread must still poll for mutators that call-out.
281 // 7. Drive the policy on time-since-begin instead of iterations.
282 // 8. Consider making the spin duration a function of the # of CPUs:
283 // Spin = (((ncpus-1) * M) + K) + F(still_running)
284 // Alternately, instead of counting iterations of the outer loop
285 // we could count the # of threads visited in the inner loop, above.
286 // 9. On windows consider using the return value from SwitchThreadTo()
287 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
288
289 if (int(iterations) == DeferPollingPageLoopCount) {
290 guarantee (PageArmed == 0, "invariant") ;
291 PageArmed = 1 ;
292 os::make_polling_page_unreadable();
293 }
294
295 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
296 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
297 ++steps ;
298 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
299 SpinPause() ; // MP-Polite spin
300 } else
301 if (steps < DeferThrSuspendLoopCount) {
302 os::naked_yield() ;
303 } else {
304 os::naked_short_sleep(1);
305 }
306
307 iterations ++ ;
308 }
309 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
310 }
311 assert(still_running == 0, "sanity check");
312
313 if (PrintSafepointStatistics) {
314 update_statistics_on_spin_end();
315 }
316
317 // wait until all threads are stopped
318 while (_waiting_to_block > 0) {
319 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
320 if (!SafepointTimeout || timeout_error_printed) {
321 Safepoint_lock->wait(true); // true, means with no safepoint checks
322 } else {
323 // Compute remaining time
324 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
325
326 // If there is no remaining time, then there is an error
327 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
328 print_safepoint_timeout(_blocking_timeout);
329 }
330 }
331 }
332 assert(_waiting_to_block == 0, "sanity check");
333
334 #ifndef PRODUCT
335 if (SafepointTimeout) {
336 jlong current_time = os::javaTimeNanos();
337 if (safepoint_limit_time < current_time) {
338 tty->print_cr("# SafepointSynchronize: Finished after "
339 INT64_FORMAT_W(6) " ms",
340 ((current_time - safepoint_limit_time) / MICROUNITS +
341 SafepointTimeoutDelay));
342 }
343 }
344 #endif
345
346 assert((_safepoint_counter & 0x1) == 0, "must be even");
347 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
348 _safepoint_counter ++;
349
350 // Record state
351 _state = _synchronized;
352
353 OrderAccess::fence();
354
355 #ifdef ASSERT
356 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
357 // make sure all the threads were visited
358 assert(cur->was_visited_for_critical_count(), "missed a thread");
359 }
360 #endif // ASSERT
361
362 // Update the count of active JNI critical regions
363 GC_locker::set_jni_lock_count(_current_jni_active_count);
364
365 if (TraceSafepoint) {
366 VM_Operation *op = VMThread::vm_operation();
367 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
368 }
369
370 RuntimeService::record_safepoint_synchronized();
371 if (PrintSafepointStatistics) {
372 update_statistics_on_sync_end(os::javaTimeNanos());
373 }
374
375 // Call stuff that needs to be run when a safepoint is just about to be completed
376 do_cleanup_tasks();
377
378 if (PrintSafepointStatistics) {
379 // Record how much time spend on the above cleanup tasks
380 update_statistics_on_cleanup_end(os::javaTimeNanos());
381 }
382 }
383
384 // Wake up all threads, so they are ready to resume execution after the safepoint
385 // operation has been carried out
386 void SafepointSynchronize::end() {
387
388 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
389 assert((_safepoint_counter & 0x1) == 1, "must be odd");
390 _safepoint_counter ++;
391 // memory fence isn't required here since an odd _safepoint_counter
392 // value can do no harm and a fence is issued below anyway.
393
394 DEBUG_ONLY(Thread* myThread = Thread::current();)
395 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
396
397 if (PrintSafepointStatistics) {
398 end_statistics(os::javaTimeNanos());
399 }
400
401 #ifdef ASSERT
402 // A pending_exception cannot be installed during a safepoint. The threads
403 // may install an async exception after they come back from a safepoint into
404 // pending_exception after they unblock. But that should happen later.
405 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
406 assert (!(cur->has_pending_exception() &&
407 cur->safepoint_state()->is_at_poll_safepoint()),
408 "safepoint installed a pending exception");
409 }
410 #endif // ASSERT
411
412 if (PageArmed) {
413 // Make polling safepoint aware
414 os::make_polling_page_readable();
415 PageArmed = 0 ;
416 }
417
418 // Remove safepoint check from interpreter
419 Interpreter::ignore_safepoints();
420
421 {
422 MutexLocker mu(Safepoint_lock);
423
424 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
425
426 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
427 // when they get restarted.
428 _state = _not_synchronized;
429 OrderAccess::fence();
430
431 if (TraceSafepoint) {
432 tty->print_cr("Leaving safepoint region");
433 }
434
435 // Start suspended threads
436 for(JavaThread *current = Threads::first(); current; current = current->next()) {
437 // A problem occurring on Solaris is when attempting to restart threads
438 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
439 // to the next one (since it has been running the longest). We then have
440 // to wait for a cpu to become available before we can continue restarting
441 // threads.
442 // FIXME: This causes the performance of the VM to degrade when active and with
443 // large numbers of threads. Apparently this is due to the synchronous nature
444 // of suspending threads.
445 //
446 // TODO-FIXME: the comments above are vestigial and no longer apply.
447 // Furthermore, using solaris' schedctl in this particular context confers no benefit
448 if (VMThreadHintNoPreempt) {
449 os::hint_no_preempt();
450 }
451 ThreadSafepointState* cur_state = current->safepoint_state();
452 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
453 cur_state->restart();
454 assert(cur_state->is_running(), "safepoint state has not been reset");
455 }
456
457 RuntimeService::record_safepoint_end();
458
459 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
460 // blocked in signal_thread_blocked
461 Threads_lock->unlock();
462
463 }
464 #if INCLUDE_ALL_GCS
465 // If there are any concurrent GC threads resume them.
466 if (UseConcMarkSweepGC) {
467 ConcurrentMarkSweepThread::desynchronize(false);
468 } else if (UseG1GC) {
469 SuspendibleThreadSet::desynchronize();
470 }
471 #endif // INCLUDE_ALL_GCS
472 // record this time so VMThread can keep track how much time has elapsed
473 // since last safepoint.
474 _end_of_last_safepoint = os::javaTimeMillis();
475 }
476
477 bool SafepointSynchronize::is_cleanup_needed() {
478 // Need a safepoint if some inline cache buffers is non-empty
479 if (!InlineCacheBuffer::is_empty()) return true;
480 return false;
481 }
482
483
484
485 // Various cleaning tasks that should be done periodically at safepoints
486 void SafepointSynchronize::do_cleanup_tasks() {
487 {
488 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
489 ObjectSynchronizer::deflate_idle_monitors();
490 }
491
492 {
493 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
494 InlineCacheBuffer::update_inline_caches();
495 }
496 {
497 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
498 CompilationPolicy::policy()->do_safepoint_work();
499 }
500
501 {
502 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
503 NMethodSweeper::mark_active_nmethods();
504 }
505
506 if (SymbolTable::needs_rehashing()) {
507 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
508 SymbolTable::rehash_table();
509 }
510
511 if (StringTable::needs_rehashing()) {
512 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
513 StringTable::rehash_table();
514 }
515
516 // rotate log files?
517 if (UseGCLogFileRotation) {
518 gclog_or_tty->rotate_log(false);
519 }
520
521 {
522 // CMS delays purging the CLDG until the beginning of the next safepoint and to
523 // make sure concurrent sweep is done
524 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
525 ClassLoaderDataGraph::purge_if_needed();
526 }
527 }
528
529
530 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
531 switch(state) {
532 case _thread_in_native:
533 // native threads are safe if they have no java stack or have walkable stack
534 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
535
536 // blocked threads should have already have walkable stack
537 case _thread_blocked:
538 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
539 return true;
540
541 default:
542 return false;
543 }
544 }
545
546
547 // See if the thread is running inside a lazy critical native and
548 // update the thread critical count if so. Also set a suspend flag to
549 // cause the native wrapper to return into the JVM to do the unlock
550 // once the native finishes.
551 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
552 if (state == _thread_in_native &&
553 thread->has_last_Java_frame() &&
554 thread->frame_anchor()->walkable()) {
555 // This thread might be in a critical native nmethod so look at
556 // the top of the stack and increment the critical count if it
557 // is.
558 frame wrapper_frame = thread->last_frame();
559 CodeBlob* stub_cb = wrapper_frame.cb();
560 if (stub_cb != NULL &&
561 stub_cb->is_nmethod() &&
562 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
563 // A thread could potentially be in a critical native across
564 // more than one safepoint, so only update the critical state on
565 // the first one. When it returns it will perform the unlock.
566 if (!thread->do_critical_native_unlock()) {
567 #ifdef ASSERT
568 if (!thread->in_critical()) {
569 GC_locker::increment_debug_jni_lock_count();
570 }
571 #endif
572 thread->enter_critical();
573 // Make sure the native wrapper calls back on return to
574 // perform the needed critical unlock.
575 thread->set_critical_native_unlock();
576 }
577 }
578 }
579 }
580
581
582
583 // -------------------------------------------------------------------------------------------------------
584 // Implementation of Safepoint callback point
585
586 void SafepointSynchronize::block(JavaThread *thread) {
587 assert(thread != NULL, "thread must be set");
588 assert(thread->is_Java_thread(), "not a Java thread");
589
590 // Threads shouldn't block if they are in the middle of printing, but...
591 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
592
593 // Only bail from the block() call if the thread is gone from the
594 // thread list; starting to exit should still block.
595 if (thread->is_terminated()) {
596 // block current thread if we come here from native code when VM is gone
597 thread->block_if_vm_exited();
598
599 // otherwise do nothing
600 return;
601 }
602
603 JavaThreadState state = thread->thread_state();
604 thread->frame_anchor()->make_walkable(thread);
605
606 // Check that we have a valid thread_state at this point
607 switch(state) {
608 case _thread_in_vm_trans:
609 case _thread_in_Java: // From compiled code
610
611 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
612 // we pretend we are still in the VM.
613 thread->set_thread_state(_thread_in_vm);
614
615 if (is_synchronizing()) {
616 Atomic::inc (&TryingToBlock) ;
617 }
618
619 // We will always be holding the Safepoint_lock when we are examine the state
620 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
621 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
622 Safepoint_lock->lock_without_safepoint_check();
623 if (is_synchronizing()) {
624 // Decrement the number of threads to wait for and signal vm thread
625 assert(_waiting_to_block > 0, "sanity check");
626 _waiting_to_block--;
627 thread->safepoint_state()->set_has_called_back(true);
628
629 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
630 if (thread->in_critical()) {
631 // Notice that this thread is in a critical section
632 increment_jni_active_count();
633 }
634
635 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
636 if (_waiting_to_block == 0) {
637 Safepoint_lock->notify_all();
638 }
639 }
640
641 // We transition the thread to state _thread_blocked here, but
642 // we can't do our usual check for external suspension and then
643 // self-suspend after the lock_without_safepoint_check() call
644 // below because we are often called during transitions while
645 // we hold different locks. That would leave us suspended while
646 // holding a resource which results in deadlocks.
647 thread->set_thread_state(_thread_blocked);
648 Safepoint_lock->unlock();
649
650 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
651 // the entire safepoint, the threads will all line up here during the safepoint.
652 Threads_lock->lock_without_safepoint_check();
653 // restore original state. This is important if the thread comes from compiled code, so it
654 // will continue to execute with the _thread_in_Java state.
655 thread->set_thread_state(state);
656 Threads_lock->unlock();
657 break;
658
659 case _thread_in_native_trans:
660 case _thread_blocked_trans:
661 case _thread_new_trans:
662 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
663 thread->print_thread_state();
664 fatal("Deadlock in safepoint code. "
665 "Should have called back to the VM before blocking.");
666 }
667
668 // We transition the thread to state _thread_blocked here, but
669 // we can't do our usual check for external suspension and then
670 // self-suspend after the lock_without_safepoint_check() call
671 // below because we are often called during transitions while
672 // we hold different locks. That would leave us suspended while
673 // holding a resource which results in deadlocks.
674 thread->set_thread_state(_thread_blocked);
675
676 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
677 // the safepoint code might still be waiting for it to block. We need to change the state here,
678 // so it can see that it is at a safepoint.
679
680 // Block until the safepoint operation is completed.
681 Threads_lock->lock_without_safepoint_check();
682
683 // Restore state
684 thread->set_thread_state(state);
685
686 Threads_lock->unlock();
687 break;
688
689 default:
690 fatal("Illegal threadstate encountered: %d", state);
691 }
692
693 // Check for pending. async. exceptions or suspends - except if the
694 // thread was blocked inside the VM. has_special_runtime_exit_condition()
695 // is called last since it grabs a lock and we only want to do that when
696 // we must.
697 //
698 // Note: we never deliver an async exception at a polling point as the
699 // compiler may not have an exception handler for it. The polling
700 // code will notice the async and deoptimize and the exception will
701 // be delivered. (Polling at a return point is ok though). Sure is
702 // a lot of bother for a deprecated feature...
703 //
704 // We don't deliver an async exception if the thread state is
705 // _thread_in_native_trans so JNI functions won't be called with
706 // a surprising pending exception. If the thread state is going back to java,
707 // async exception is checked in check_special_condition_for_native_trans().
708
709 if (state != _thread_blocked_trans &&
710 state != _thread_in_vm_trans &&
711 thread->has_special_runtime_exit_condition()) {
712 thread->handle_special_runtime_exit_condition(
713 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
714 }
715 }
716
717 // ------------------------------------------------------------------------------------------------------
718 // Exception handlers
719
720
721 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
722 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
723 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
724 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
725
726 if (ShowSafepointMsgs) {
727 tty->print("handle_polling_page_exception: ");
728 }
729
730 if (PrintSafepointStatistics) {
731 inc_page_trap_count();
732 }
733
734 ThreadSafepointState* state = thread->safepoint_state();
735
736 state->handle_polling_page_exception();
737 }
738
739
740 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
741 if (!timeout_error_printed) {
742 timeout_error_printed = true;
743 // Print out the thread info which didn't reach the safepoint for debugging
744 // purposes (useful when there are lots of threads in the debugger).
745 tty->cr();
746 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
747 if (reason == _spinning_timeout) {
748 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
749 } else if (reason == _blocking_timeout) {
750 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
751 }
752
753 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
754 ThreadSafepointState *cur_state;
755 ResourceMark rm;
756 for(JavaThread *cur_thread = Threads::first(); cur_thread;
757 cur_thread = cur_thread->next()) {
758 cur_state = cur_thread->safepoint_state();
759
760 if (cur_thread->thread_state() != _thread_blocked &&
761 ((reason == _spinning_timeout && cur_state->is_running()) ||
762 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
763 tty->print("# ");
764 cur_thread->print();
765 tty->cr();
766 }
767 }
768 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
769 }
770
771 // To debug the long safepoint, specify both DieOnSafepointTimeout &
772 // ShowMessageBoxOnError.
773 if (DieOnSafepointTimeout) {
774 VM_Operation *op = VMThread::vm_operation();
775 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
776 SafepointTimeoutDelay,
777 op != NULL ? op->name() : "no vm operation");
778 }
779 }
780
781
782 // -------------------------------------------------------------------------------------------------------
783 // Implementation of ThreadSafepointState
784
785 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
786 _thread = thread;
787 _type = _running;
788 _has_called_back = false;
789 _at_poll_safepoint = false;
790 }
791
792 void ThreadSafepointState::create(JavaThread *thread) {
793 ThreadSafepointState *state = new ThreadSafepointState(thread);
794 thread->set_safepoint_state(state);
795 }
796
797 void ThreadSafepointState::destroy(JavaThread *thread) {
798 if (thread->safepoint_state()) {
799 delete(thread->safepoint_state());
800 thread->set_safepoint_state(NULL);
801 }
802 }
803
804 void ThreadSafepointState::examine_state_of_thread() {
805 assert(is_running(), "better be running or just have hit safepoint poll");
806
807 JavaThreadState state = _thread->thread_state();
808
809 // Save the state at the start of safepoint processing.
810 _orig_thread_state = state;
811
812 // Check for a thread that is suspended. Note that thread resume tries
813 // to grab the Threads_lock which we own here, so a thread cannot be
814 // resumed during safepoint synchronization.
815
816 // We check to see if this thread is suspended without locking to
817 // avoid deadlocking with a third thread that is waiting for this
818 // thread to be suspended. The third thread can notice the safepoint
819 // that we're trying to start at the beginning of its SR_lock->wait()
820 // call. If that happens, then the third thread will block on the
821 // safepoint while still holding the underlying SR_lock. We won't be
822 // able to get the SR_lock and we'll deadlock.
823 //
824 // We don't need to grab the SR_lock here for two reasons:
825 // 1) The suspend flags are both volatile and are set with an
826 // Atomic::cmpxchg() call so we should see the suspended
827 // state right away.
828 // 2) We're being called from the safepoint polling loop; if
829 // we don't see the suspended state on this iteration, then
830 // we'll come around again.
831 //
832 bool is_suspended = _thread->is_ext_suspended();
833 if (is_suspended) {
834 roll_forward(_at_safepoint);
835 return;
836 }
837
838 // Some JavaThread states have an initial safepoint state of
839 // running, but are actually at a safepoint. We will happily
840 // agree and update the safepoint state here.
841 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
842 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
843 roll_forward(_at_safepoint);
844 return;
845 }
846
847 if (state == _thread_in_vm) {
848 roll_forward(_call_back);
849 return;
850 }
851
852 // All other thread states will continue to run until they
853 // transition and self-block in state _blocked
854 // Safepoint polling in compiled code causes the Java threads to do the same.
855 // Note: new threads may require a malloc so they must be allowed to finish
856
857 assert(is_running(), "examine_state_of_thread on non-running thread");
858 return;
859 }
860
861 // Returns true is thread could not be rolled forward at present position.
862 void ThreadSafepointState::roll_forward(suspend_type type) {
863 _type = type;
864
865 switch(_type) {
866 case _at_safepoint:
867 SafepointSynchronize::signal_thread_at_safepoint();
868 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
869 if (_thread->in_critical()) {
870 // Notice that this thread is in a critical section
871 SafepointSynchronize::increment_jni_active_count();
872 }
873 break;
874
875 case _call_back:
876 set_has_called_back(false);
877 break;
878
879 case _running:
880 default:
881 ShouldNotReachHere();
882 }
883 }
884
885 void ThreadSafepointState::restart() {
886 switch(type()) {
887 case _at_safepoint:
888 case _call_back:
889 break;
890
891 case _running:
892 default:
893 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
894 p2i(_thread), _type);
895 _thread->print();
896 ShouldNotReachHere();
897 }
898 _type = _running;
899 set_has_called_back(false);
900 }
901
902
903 void ThreadSafepointState::print_on(outputStream *st) const {
904 const char *s;
905
906 switch(_type) {
907 case _running : s = "_running"; break;
908 case _at_safepoint : s = "_at_safepoint"; break;
909 case _call_back : s = "_call_back"; break;
910 default:
911 ShouldNotReachHere();
912 }
913
914 st->print_cr("Thread: " INTPTR_FORMAT
915 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
916 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
917 _at_poll_safepoint);
918
919 _thread->print_thread_state_on(st);
920 }
921
922
923 // ---------------------------------------------------------------------------------------------------------------------
924
925 // Block the thread at the safepoint poll or poll return.
926 void ThreadSafepointState::handle_polling_page_exception() {
927
928 // Check state. block() will set thread state to thread_in_vm which will
929 // cause the safepoint state _type to become _call_back.
930 assert(type() == ThreadSafepointState::_running,
931 "polling page exception on thread not running state");
932
933 // Step 1: Find the nmethod from the return address
934 if (ShowSafepointMsgs && Verbose) {
935 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
936 }
937 address real_return_addr = thread()->saved_exception_pc();
938
939 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
940 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
941 nmethod* nm = (nmethod*)cb;
942
943 // Find frame of caller
944 frame stub_fr = thread()->last_frame();
945 CodeBlob* stub_cb = stub_fr.cb();
946 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
947 RegisterMap map(thread(), true);
948 frame caller_fr = stub_fr.sender(&map);
949
950 // Should only be poll_return or poll
951 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
952
953 // This is a poll immediately before a return. The exception handling code
954 // has already had the effect of causing the return to occur, so the execution
955 // will continue immediately after the call. In addition, the oopmap at the
956 // return point does not mark the return value as an oop (if it is), so
957 // it needs a handle here to be updated.
958 if( nm->is_at_poll_return(real_return_addr) ) {
959 // See if return type is an oop.
960 bool return_oop = nm->method()->is_returning_oop();
961 Handle return_value;
962 if (return_oop) {
963 // The oop result has been saved on the stack together with all
964 // the other registers. In order to preserve it over GCs we need
965 // to keep it in a handle.
966 oop result = caller_fr.saved_oop_result(&map);
967 assert(result == NULL || result->is_oop(), "must be oop");
968 return_value = Handle(thread(), result);
969 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
970 }
971
972 // Block the thread
973 SafepointSynchronize::block(thread());
974
975 // restore oop result, if any
976 if (return_oop) {
977 caller_fr.set_saved_oop_result(&map, return_value());
978 }
979 }
980
981 // This is a safepoint poll. Verify the return address and block.
982 else {
983 set_at_poll_safepoint(true);
984
985 // verify the blob built the "return address" correctly
986 assert(real_return_addr == caller_fr.pc(), "must match");
987
988 // Block the thread
989 SafepointSynchronize::block(thread());
990 set_at_poll_safepoint(false);
991
992 // If we have a pending async exception deoptimize the frame
993 // as otherwise we may never deliver it.
994 if (thread()->has_async_condition()) {
995 ThreadInVMfromJavaNoAsyncException __tiv(thread());
996 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
997 }
998
999 // If an exception has been installed we must check for a pending deoptimization
1000 // Deoptimize frame if exception has been thrown.
1001
1002 if (thread()->has_pending_exception() ) {
1003 RegisterMap map(thread(), true);
1004 frame caller_fr = stub_fr.sender(&map);
1005 if (caller_fr.is_deoptimized_frame()) {
1006 // The exception patch will destroy registers that are still
1007 // live and will be needed during deoptimization. Defer the
1008 // Async exception should have deferred the exception until the
1009 // next safepoint which will be detected when we get into
1010 // the interpreter so if we have an exception now things
1011 // are messed up.
1012
1013 fatal("Exception installed and deoptimization is pending");
1014 }
1015 }
1016 }
1017 }
1018
1019
1020 //
1021 // Statistics & Instrumentations
1022 //
1023 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1024 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1025 int SafepointSynchronize::_cur_stat_index = 0;
1026 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1027 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1028 jlong SafepointSynchronize::_max_sync_time = 0;
1029 jlong SafepointSynchronize::_max_vmop_time = 0;
1030 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1031
1032 static jlong cleanup_end_time = 0;
1033 static bool need_to_track_page_armed_status = false;
1034 static bool init_done = false;
1035
1036 // Helper method to print the header.
1037 static void print_header() {
1038 tty->print(" vmop "
1039 "[threads: total initially_running wait_to_block] ");
1040 tty->print("[time: spin block sync cleanup vmop] ");
1041
1042 // no page armed status printed out if it is always armed.
1043 if (need_to_track_page_armed_status) {
1044 tty->print("page_armed ");
1045 }
1046
1047 tty->print_cr("page_trap_count");
1048 }
1049
1050 void SafepointSynchronize::deferred_initialize_stat() {
1051 if (init_done) return;
1052
1053 if (PrintSafepointStatisticsCount <= 0) {
1054 fatal("Wrong PrintSafepointStatisticsCount");
1055 }
1056
1057 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1058 // be printed right away, in which case, _safepoint_stats will regress to
1059 // a single element array. Otherwise, it is a circular ring buffer with default
1060 // size of PrintSafepointStatisticsCount.
1061 int stats_array_size;
1062 if (PrintSafepointStatisticsTimeout > 0) {
1063 stats_array_size = 1;
1064 PrintSafepointStatistics = true;
1065 } else {
1066 stats_array_size = PrintSafepointStatisticsCount;
1067 }
1068 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1069 * sizeof(SafepointStats), mtInternal);
1070 guarantee(_safepoint_stats != NULL,
1071 "not enough memory for safepoint instrumentation data");
1072
1073 if (DeferPollingPageLoopCount >= 0) {
1074 need_to_track_page_armed_status = true;
1075 }
1076 init_done = true;
1077 }
1078
1079 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1080 assert(init_done, "safepoint statistics array hasn't been initialized");
1081 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1082
1083 spstat->_time_stamp = _ts_of_current_safepoint;
1084
1085 VM_Operation *op = VMThread::vm_operation();
1086 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1087 if (op != NULL) {
1088 _safepoint_reasons[spstat->_vmop_type]++;
1089 }
1090
1091 spstat->_nof_total_threads = nof_threads;
1092 spstat->_nof_initial_running_threads = nof_running;
1093 spstat->_nof_threads_hit_page_trap = 0;
1094
1095 // Records the start time of spinning. The real time spent on spinning
1096 // will be adjusted when spin is done. Same trick is applied for time
1097 // spent on waiting for threads to block.
1098 if (nof_running != 0) {
1099 spstat->_time_to_spin = os::javaTimeNanos();
1100 } else {
1101 spstat->_time_to_spin = 0;
1102 }
1103 }
1104
1105 void SafepointSynchronize::update_statistics_on_spin_end() {
1106 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1107
1108 jlong cur_time = os::javaTimeNanos();
1109
1110 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1111 if (spstat->_nof_initial_running_threads != 0) {
1112 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1113 }
1114
1115 if (need_to_track_page_armed_status) {
1116 spstat->_page_armed = (PageArmed == 1);
1117 }
1118
1119 // Records the start time of waiting for to block. Updated when block is done.
1120 if (_waiting_to_block != 0) {
1121 spstat->_time_to_wait_to_block = cur_time;
1122 } else {
1123 spstat->_time_to_wait_to_block = 0;
1124 }
1125 }
1126
1127 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1128 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1129
1130 if (spstat->_nof_threads_wait_to_block != 0) {
1131 spstat->_time_to_wait_to_block = end_time -
1132 spstat->_time_to_wait_to_block;
1133 }
1134
1135 // Records the end time of sync which will be used to calculate the total
1136 // vm operation time. Again, the real time spending in syncing will be deducted
1137 // from the start of the sync time later when end_statistics is called.
1138 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1139 if (spstat->_time_to_sync > _max_sync_time) {
1140 _max_sync_time = spstat->_time_to_sync;
1141 }
1142
1143 spstat->_time_to_do_cleanups = end_time;
1144 }
1145
1146 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1147 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1148
1149 // Record how long spent in cleanup tasks.
1150 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1151
1152 cleanup_end_time = end_time;
1153 }
1154
1155 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1156 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1157
1158 // Update the vm operation time.
1159 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1160 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1161 _max_vmop_time = spstat->_time_to_exec_vmop;
1162 }
1163 // Only the sync time longer than the specified
1164 // PrintSafepointStatisticsTimeout will be printed out right away.
1165 // By default, it is -1 meaning all samples will be put into the list.
1166 if ( PrintSafepointStatisticsTimeout > 0) {
1167 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1168 print_statistics();
1169 }
1170 } else {
1171 // The safepoint statistics will be printed out when the _safepoin_stats
1172 // array fills up.
1173 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1174 print_statistics();
1175 _cur_stat_index = 0;
1176 } else {
1177 _cur_stat_index++;
1178 }
1179 }
1180 }
1181
1182 void SafepointSynchronize::print_statistics() {
1183 SafepointStats* sstats = _safepoint_stats;
1184
1185 for (int index = 0; index <= _cur_stat_index; index++) {
1186 if (index % 30 == 0) {
1187 print_header();
1188 }
1189 sstats = &_safepoint_stats[index];
1190 tty->print("%.3f: ", sstats->_time_stamp);
1191 tty->print("%-26s ["
1192 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
1193 " ] ",
1194 sstats->_vmop_type == -1 ? "no vm operation" :
1195 VM_Operation::name(sstats->_vmop_type),
1196 sstats->_nof_total_threads,
1197 sstats->_nof_initial_running_threads,
1198 sstats->_nof_threads_wait_to_block);
1199 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1200 tty->print(" ["
1201 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1202 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
1203 INT64_FORMAT_W(6) " ] ",
1204 sstats->_time_to_spin / MICROUNITS,
1205 sstats->_time_to_wait_to_block / MICROUNITS,
1206 sstats->_time_to_sync / MICROUNITS,
1207 sstats->_time_to_do_cleanups / MICROUNITS,
1208 sstats->_time_to_exec_vmop / MICROUNITS);
1209
1210 if (need_to_track_page_armed_status) {
1211 tty->print(INT32_FORMAT " ", sstats->_page_armed);
1212 }
1213 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
1214 }
1215 }
1216
1217 // This method will be called when VM exits. It will first call
1218 // print_statistics to print out the rest of the sampling. Then
1219 // it tries to summarize the sampling.
1220 void SafepointSynchronize::print_stat_on_exit() {
1221 if (_safepoint_stats == NULL) return;
1222
1223 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1224
1225 // During VM exit, end_statistics may not get called and in that
1226 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1227 // don't print it out.
1228 // Approximate the vm op time.
1229 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1230 os::javaTimeNanos() - cleanup_end_time;
1231
1232 if ( PrintSafepointStatisticsTimeout < 0 ||
1233 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1234 print_statistics();
1235 }
1236 tty->cr();
1237
1238 // Print out polling page sampling status.
1239 if (!need_to_track_page_armed_status) {
1240 tty->print_cr("Polling page always armed");
1241 } else {
1242 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
1243 DeferPollingPageLoopCount);
1244 }
1245
1246 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1247 if (_safepoint_reasons[index] != 0) {
1248 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
1249 _safepoint_reasons[index]);
1250 }
1251 }
1252
1253 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
1254 _coalesced_vmop_count);
1255 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
1256 _max_sync_time / MICROUNITS);
1257 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1258 INT64_FORMAT_W(5) " ms",
1259 _max_vmop_time / MICROUNITS);
1260 }
1261
1262 // ------------------------------------------------------------------------------------------------
1263 // Non-product code
1264
1265 #ifndef PRODUCT
1266
1267 void SafepointSynchronize::print_state() {
1268 if (_state == _not_synchronized) {
1269 tty->print_cr("not synchronized");
1270 } else if (_state == _synchronizing || _state == _synchronized) {
1271 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1272 "synchronized");
1273
1274 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1275 cur->safepoint_state()->print();
1276 }
1277 }
1278 }
1279
1280 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1281 if (ShowSafepointMsgs) {
1282 va_list ap;
1283 va_start(ap, format);
1284 tty->vprint_cr(format, ap);
1285 va_end(ap);
1286 }
1287 }
1288
1289 #endif // !PRODUCT