1 /*
2 * Copyright (c) 1997, 2014, 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_interface/collectedHeap.hpp"
34 #include "interpreter/interpreter.hpp"
35 #include "memory/gcLocker.inline.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/memTracker.hpp"
56 #include "services/runtimeService.hpp"
57 #include "utilities/events.hpp"
58 #include "utilities/macros.hpp"
59 #ifdef TARGET_ARCH_x86
60 # include "nativeInst_x86.hpp"
61 # include "vmreg_x86.inline.hpp"
62 #endif
63 #ifdef TARGET_ARCH_sparc
64 # include "nativeInst_sparc.hpp"
65 # include "vmreg_sparc.inline.hpp"
66 #endif
67 #ifdef TARGET_ARCH_zero
68 # include "nativeInst_zero.hpp"
69 # include "vmreg_zero.inline.hpp"
70 #endif
71 #ifdef TARGET_ARCH_arm
72 # include "nativeInst_arm.hpp"
73 # include "vmreg_arm.inline.hpp"
74 #endif
75 #ifdef TARGET_ARCH_ppc
76 # include "nativeInst_ppc.hpp"
77 # include "vmreg_ppc.inline.hpp"
78 #endif
79 #if INCLUDE_ALL_GCS
80 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
81 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
82 #endif // INCLUDE_ALL_GCS
83 #ifdef COMPILER1
84 #include "c1/c1_globals.hpp"
85 #endif
86
87 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
88
89 // --------------------------------------------------------------------------------------------------
90 // Implementation of Safepoint begin/end
91
92 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
93 volatile int SafepointSynchronize::_waiting_to_block = 0;
94 volatile int SafepointSynchronize::_safepoint_counter = 0;
95 int SafepointSynchronize::_current_jni_active_count = 0;
96 long SafepointSynchronize::_end_of_last_safepoint = 0;
97 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
98 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
99 static bool timeout_error_printed = false;
100
101 // Roll all threads forward to a safepoint and suspend them all
102 void SafepointSynchronize::begin() {
103
104 Thread* myThread = Thread::current();
105 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
106
107 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
108 _safepoint_begin_time = os::javaTimeNanos();
109 _ts_of_current_safepoint = tty->time_stamp().seconds();
110 }
111
112 #if INCLUDE_ALL_GCS
113 if (UseConcMarkSweepGC) {
114 // In the future we should investigate whether CMS can use the
115 // more-general mechanism below. DLD (01/05).
116 ConcurrentMarkSweepThread::synchronize(false);
117 } else if (UseG1GC) {
118 SuspendibleThreadSet::synchronize();
119 }
120 #endif // INCLUDE_ALL_GCS
121
122 // By getting the Threads_lock, we assure that no threads are about to start or
123 // exit. It is released again in SafepointSynchronize::end().
124 Threads_lock->lock();
125
126 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
127
128 int nof_threads = Threads::number_of_threads();
129
130 if (TraceSafepoint) {
131 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
132 }
133
134 RuntimeService::record_safepoint_begin();
135
136 MutexLocker mu(Safepoint_lock);
137
138 // Reset the count of active JNI critical threads
139 _current_jni_active_count = 0;
140
141 // Set number of threads to wait for, before we initiate the callbacks
142 _waiting_to_block = nof_threads;
143 TryingToBlock = 0 ;
144 int still_running = nof_threads;
145
146 // Save the starting time, so that it can be compared to see if this has taken
147 // too long to complete.
148 jlong safepoint_limit_time;
149 timeout_error_printed = false;
150
151 // PrintSafepointStatisticsTimeout can be specified separately. When
152 // specified, PrintSafepointStatistics will be set to true in
153 // deferred_initialize_stat method. The initialization has to be done
154 // early enough to avoid any races. See bug 6880029 for details.
155 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
156 deferred_initialize_stat();
157 }
158
159 // Begin the process of bringing the system to a safepoint.
160 // Java threads can be in several different states and are
161 // stopped by different mechanisms:
162 //
163 // 1. Running interpreted
164 // The interpreter dispatch table is changed to force it to
165 // check for a safepoint condition between bytecodes.
166 // 2. Running in native code
167 // When returning from the native code, a Java thread must check
168 // the safepoint _state to see if we must block. If the
169 // VM thread sees a Java thread in native, it does
170 // not wait for this thread to block. The order of the memory
171 // writes and reads of both the safepoint state and the Java
172 // threads state is critical. In order to guarantee that the
173 // memory writes are serialized with respect to each other,
174 // the VM thread issues a memory barrier instruction
175 // (on MP systems). In order to avoid the overhead of issuing
176 // a memory barrier for each Java thread making native calls, each Java
177 // thread performs a write to a single memory page after changing
178 // the thread state. The VM thread performs a sequence of
179 // mprotect OS calls which forces all previous writes from all
180 // Java threads to be serialized. This is done in the
181 // os::serialize_thread_states() call. This has proven to be
182 // much more efficient than executing a membar instruction
183 // on every call to native code.
184 // 3. Running compiled Code
185 // Compiled code reads a global (Safepoint Polling) page that
186 // is set to fault if we are trying to get to a safepoint.
187 // 4. Blocked
188 // A thread which is blocked will not be allowed to return from the
189 // block condition until the safepoint operation is complete.
190 // 5. In VM or Transitioning between states
191 // If a Java thread is currently running in the VM or transitioning
192 // between states, the safepointing code will wait for the thread to
193 // block itself when it attempts transitions to a new state.
194 //
195 _state = _synchronizing;
196 OrderAccess::fence();
197
198 // Flush all thread states to memory
199 if (!UseMembar) {
200 os::serialize_thread_states();
201 }
202
203 // Make interpreter safepoint aware
204 Interpreter::notice_safepoints();
205
206 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
207 // Make polling safepoint aware
208 guarantee (PageArmed == 0, "invariant") ;
209 PageArmed = 1 ;
210 os::make_polling_page_unreadable();
211 }
212
213 // Consider using active_processor_count() ... but that call is expensive.
214 int ncpus = os::processor_count() ;
215
216 #ifdef ASSERT
217 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
218 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
219 // Clear the visited flag to ensure that the critical counts are collected properly.
220 cur->set_visited_for_critical_count(false);
221 }
222 #endif // ASSERT
223
224 if (SafepointTimeout)
225 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
226
227 // Iterate through all threads until it have been determined how to stop them all at a safepoint
228 unsigned int iterations = 0;
229 int steps = 0 ;
230 while(still_running > 0) {
231 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
232 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
233 ThreadSafepointState *cur_state = cur->safepoint_state();
234 if (cur_state->is_running()) {
235 cur_state->examine_state_of_thread();
236 if (!cur_state->is_running()) {
237 still_running--;
238 // consider adjusting steps downward:
239 // steps = 0
240 // steps -= NNN
241 // steps >>= 1
242 // steps = MIN(steps, 2000-100)
243 // if (iterations != 0) steps -= NNN
244 }
245 if (TraceSafepoint && Verbose) cur_state->print();
246 }
247 }
248
249 if (PrintSafepointStatistics && iterations == 0) {
250 begin_statistics(nof_threads, still_running);
251 }
252
253 if (still_running > 0) {
254 // Check for if it takes to long
255 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
256 print_safepoint_timeout(_spinning_timeout);
257 }
258
259 // Spin to avoid context switching.
260 // There's a tension between allowing the mutators to run (and rendezvous)
261 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
262 // a mutator might otherwise use profitably to reach a safepoint. Excessive
263 // spinning by the VM thread on a saturated system can increase rendezvous latency.
264 // Blocking or yielding incur their own penalties in the form of context switching
265 // and the resultant loss of $ residency.
266 //
267 // Further complicating matters is that yield() does not work as naively expected
268 // on many platforms -- yield() does not guarantee that any other ready threads
269 // will run. As such we revert to naked_short_sleep() after some number of iterations.
270 // nakes_short_sleep() is implemented as a short unconditional sleep.
271 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
272 // can actually increase the time it takes the VM thread to detect that a system-wide
273 // stop-the-world safepoint has been reached. In a pathological scenario such as that
274 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
275 // In that case the mutators will be stalled waiting for the safepoint to complete and the
276 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
277 // will eventually wake up and detect that all mutators are safe, at which point
278 // we'll again make progress.
279 //
280 // Beware too that that the VMThread typically runs at elevated priority.
281 // Its default priority is higher than the default mutator priority.
282 // Obviously, this complicates spinning.
283 //
284 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
285 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
286 //
287 // See the comments in synchronizer.cpp for additional remarks on spinning.
288 //
289 // In the future we might:
290 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
291 // This is tricky as the path used by a thread exiting the JVM (say on
292 // on JNI call-out) simply stores into its state field. The burden
293 // is placed on the VM thread, which must poll (spin).
294 // 2. Find something useful to do while spinning. If the safepoint is GC-related
295 // we might aggressively scan the stacks of threads that are already safe.
296 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
297 // If all the mutators are ONPROC there's no reason to sleep or yield.
298 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
299 // 5. Check system saturation. If the system is not fully saturated then
300 // simply spin and avoid sleep/yield.
301 // 6. As still-running mutators rendezvous they could unpark the sleeping
302 // VMthread. This works well for still-running mutators that become
303 // safe. The VMthread must still poll for mutators that call-out.
304 // 7. Drive the policy on time-since-begin instead of iterations.
305 // 8. Consider making the spin duration a function of the # of CPUs:
306 // Spin = (((ncpus-1) * M) + K) + F(still_running)
307 // Alternately, instead of counting iterations of the outer loop
308 // we could count the # of threads visited in the inner loop, above.
309 // 9. On windows consider using the return value from SwitchThreadTo()
310 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
311
312 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
313 guarantee (PageArmed == 0, "invariant") ;
314 PageArmed = 1 ;
315 os::make_polling_page_unreadable();
316 }
317
318 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
319 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
320 ++steps ;
321 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
322 SpinPause() ; // MP-Polite spin
323 } else
324 if (steps < DeferThrSuspendLoopCount) {
325 os::NakedYield() ;
326 } else {
327 os::naked_short_sleep(1);
328 }
329
330 iterations ++ ;
331 }
332 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
333 }
334 assert(still_running == 0, "sanity check");
335
336 if (PrintSafepointStatistics) {
337 update_statistics_on_spin_end();
338 }
339
340 // wait until all threads are stopped
341 while (_waiting_to_block > 0) {
342 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
343 if (!SafepointTimeout || timeout_error_printed) {
344 Safepoint_lock->wait(true); // true, means with no safepoint checks
345 } else {
346 // Compute remaining time
347 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
348
349 // If there is no remaining time, then there is an error
350 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
351 print_safepoint_timeout(_blocking_timeout);
352 }
353 }
354 }
355 assert(_waiting_to_block == 0, "sanity check");
356
357 #ifndef PRODUCT
358 if (SafepointTimeout) {
359 jlong current_time = os::javaTimeNanos();
360 if (safepoint_limit_time < current_time) {
361 tty->print_cr("# SafepointSynchronize: Finished after "
362 INT64_FORMAT_W(6) " ms",
363 ((current_time - safepoint_limit_time) / MICROUNITS +
364 SafepointTimeoutDelay));
365 }
366 }
367 #endif
368
369 assert((_safepoint_counter & 0x1) == 0, "must be even");
370 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
371 _safepoint_counter ++;
372
373 // Record state
374 _state = _synchronized;
375
376 OrderAccess::fence();
377
378 #ifdef ASSERT
379 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
380 // make sure all the threads were visited
381 assert(cur->was_visited_for_critical_count(), "missed a thread");
382 }
383 #endif // ASSERT
384
385 // Update the count of active JNI critical regions
386 GC_locker::set_jni_lock_count(_current_jni_active_count);
387
388 if (TraceSafepoint) {
389 VM_Operation *op = VMThread::vm_operation();
390 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
391 }
392
393 RuntimeService::record_safepoint_synchronized();
394 if (PrintSafepointStatistics) {
395 update_statistics_on_sync_end(os::javaTimeNanos());
396 }
397
398 // Call stuff that needs to be run when a safepoint is just about to be completed
399 do_cleanup_tasks();
400
401 if (PrintSafepointStatistics) {
402 // Record how much time spend on the above cleanup tasks
403 update_statistics_on_cleanup_end(os::javaTimeNanos());
404 }
405 }
406
407 // Wake up all threads, so they are ready to resume execution after the safepoint
408 // operation has been carried out
409 void SafepointSynchronize::end() {
410
411 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
412 assert((_safepoint_counter & 0x1) == 1, "must be odd");
413 _safepoint_counter ++;
414 // memory fence isn't required here since an odd _safepoint_counter
415 // value can do no harm and a fence is issued below anyway.
416
417 DEBUG_ONLY(Thread* myThread = Thread::current();)
418 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
419
420 if (PrintSafepointStatistics) {
421 end_statistics(os::javaTimeNanos());
422 }
423
424 #ifdef ASSERT
425 // A pending_exception cannot be installed during a safepoint. The threads
426 // may install an async exception after they come back from a safepoint into
427 // pending_exception after they unblock. But that should happen later.
428 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
429 assert (!(cur->has_pending_exception() &&
430 cur->safepoint_state()->is_at_poll_safepoint()),
431 "safepoint installed a pending exception");
432 }
433 #endif // ASSERT
434
435 if (PageArmed) {
436 // Make polling safepoint aware
437 os::make_polling_page_readable();
438 PageArmed = 0 ;
439 }
440
441 // Remove safepoint check from interpreter
442 Interpreter::ignore_safepoints();
443
444 {
445 MutexLocker mu(Safepoint_lock);
446
447 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
448
449 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
450 // when they get restarted.
451 _state = _not_synchronized;
452 OrderAccess::fence();
453
454 if (TraceSafepoint) {
455 tty->print_cr("Leaving safepoint region");
456 }
457
458 // Start suspended threads
459 for(JavaThread *current = Threads::first(); current; current = current->next()) {
460 // A problem occurring on Solaris is when attempting to restart threads
461 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
462 // to the next one (since it has been running the longest). We then have
463 // to wait for a cpu to become available before we can continue restarting
464 // threads.
465 // FIXME: This causes the performance of the VM to degrade when active and with
466 // large numbers of threads. Apparently this is due to the synchronous nature
467 // of suspending threads.
468 //
469 // TODO-FIXME: the comments above are vestigial and no longer apply.
470 // Furthermore, using solaris' schedctl in this particular context confers no benefit
471 if (VMThreadHintNoPreempt) {
472 os::hint_no_preempt();
473 }
474 ThreadSafepointState* cur_state = current->safepoint_state();
475 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
476 cur_state->restart();
477 assert(cur_state->is_running(), "safepoint state has not been reset");
478 }
479
480 RuntimeService::record_safepoint_end();
481
482 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
483 // blocked in signal_thread_blocked
484 Threads_lock->unlock();
485
486 }
487 #if INCLUDE_ALL_GCS
488 // If there are any concurrent GC threads resume them.
489 if (UseConcMarkSweepGC) {
490 ConcurrentMarkSweepThread::desynchronize(false);
491 } else if (UseG1GC) {
492 SuspendibleThreadSet::desynchronize();
493 }
494 #endif // INCLUDE_ALL_GCS
495 // record this time so VMThread can keep track how much time has elapsed
496 // since last safepoint.
497 _end_of_last_safepoint = os::javaTimeMillis();
498 }
499
500 bool SafepointSynchronize::is_cleanup_needed() {
501 // Need a safepoint if some inline cache buffers is non-empty
502 if (!InlineCacheBuffer::is_empty()) return true;
503 return false;
504 }
505
506
507
508 // Various cleaning tasks that should be done periodically at safepoints
509 void SafepointSynchronize::do_cleanup_tasks() {
510 {
511 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
512 ObjectSynchronizer::deflate_idle_monitors();
513 }
514
515 {
516 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
517 InlineCacheBuffer::update_inline_caches();
518 }
519 {
520 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
521 CompilationPolicy::policy()->do_safepoint_work();
522 }
523
524 {
525 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
526 NMethodSweeper::mark_active_nmethods();
527 }
528
529 if (SymbolTable::needs_rehashing()) {
530 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
531 SymbolTable::rehash_table();
532 }
533
534 if (StringTable::needs_rehashing()) {
535 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
536 StringTable::rehash_table();
537 }
538
539 // rotate log files?
540 if (UseGCLogFileRotation) {
541 gclog_or_tty->rotate_log(false);
542 }
543
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
551 if (MemTracker::is_on()) {
552 MemTracker::sync();
553 }
554 }
555
556
557 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
558 switch(state) {
559 case _thread_in_native:
560 // native threads are safe if they have no java stack or have walkable stack
561 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
562
563 // blocked threads should have already have walkable stack
564 case _thread_blocked:
565 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
566 return true;
567
568 default:
569 return false;
570 }
571 }
572
573
574 // See if the thread is running inside a lazy critical native and
575 // update the thread critical count if so. Also set a suspend flag to
576 // cause the native wrapper to return into the JVM to do the unlock
577 // once the native finishes.
578 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
579 if (state == _thread_in_native &&
580 thread->has_last_Java_frame() &&
581 thread->frame_anchor()->walkable()) {
582 // This thread might be in a critical native nmethod so look at
583 // the top of the stack and increment the critical count if it
584 // is.
585 frame wrapper_frame = thread->last_frame();
586 CodeBlob* stub_cb = wrapper_frame.cb();
587 if (stub_cb != NULL &&
588 stub_cb->is_nmethod() &&
589 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
590 // A thread could potentially be in a critical native across
591 // more than one safepoint, so only update the critical state on
592 // the first one. When it returns it will perform the unlock.
593 if (!thread->do_critical_native_unlock()) {
594 #ifdef ASSERT
595 if (!thread->in_critical()) {
596 GC_locker::increment_debug_jni_lock_count();
597 }
598 #endif
599 thread->enter_critical();
600 // Make sure the native wrapper calls back on return to
601 // perform the needed critical unlock.
602 thread->set_critical_native_unlock();
603 }
604 }
605 }
606 }
607
608
609
610 // -------------------------------------------------------------------------------------------------------
611 // Implementation of Safepoint callback point
612
613 void SafepointSynchronize::block(JavaThread *thread) {
614 assert(thread != NULL, "thread must be set");
615 assert(thread->is_Java_thread(), "not a Java thread");
616
617 // Threads shouldn't block if they are in the middle of printing, but...
618 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
619
620 // Only bail from the block() call if the thread is gone from the
621 // thread list; starting to exit should still block.
622 if (thread->is_terminated()) {
623 // block current thread if we come here from native code when VM is gone
624 thread->block_if_vm_exited();
625
626 // otherwise do nothing
627 return;
628 }
629
630 JavaThreadState state = thread->thread_state();
631 thread->frame_anchor()->make_walkable(thread);
632
633 // Check that we have a valid thread_state at this point
634 switch(state) {
635 case _thread_in_vm_trans:
636 case _thread_in_Java: // From compiled code
637
638 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
639 // we pretend we are still in the VM.
640 thread->set_thread_state(_thread_in_vm);
641
642 if (is_synchronizing()) {
643 Atomic::inc (&TryingToBlock) ;
644 }
645
646 // We will always be holding the Safepoint_lock when we are examine the state
647 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
648 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
649 Safepoint_lock->lock_without_safepoint_check();
650 if (is_synchronizing()) {
651 // Decrement the number of threads to wait for and signal vm thread
652 assert(_waiting_to_block > 0, "sanity check");
653 _waiting_to_block--;
654 thread->safepoint_state()->set_has_called_back(true);
655
656 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
657 if (thread->in_critical()) {
658 // Notice that this thread is in a critical section
659 increment_jni_active_count();
660 }
661
662 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
663 if (_waiting_to_block == 0) {
664 Safepoint_lock->notify_all();
665 }
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 Safepoint_lock->unlock();
676
677 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
678 // the entire safepoint, the threads will all line up here during the safepoint.
679 Threads_lock->lock_without_safepoint_check();
680 // restore original state. This is important if the thread comes from compiled code, so it
681 // will continue to execute with the _thread_in_Java state.
682 thread->set_thread_state(state);
683 Threads_lock->unlock();
684 break;
685
686 case _thread_in_native_trans:
687 case _thread_blocked_trans:
688 case _thread_new_trans:
689 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
690 thread->print_thread_state();
691 fatal("Deadlock in safepoint code. "
692 "Should have called back to the VM before blocking.");
693 }
694
695 // We transition the thread to state _thread_blocked here, but
696 // we can't do our usual check for external suspension and then
697 // self-suspend after the lock_without_safepoint_check() call
698 // below because we are often called during transitions while
699 // we hold different locks. That would leave us suspended while
700 // holding a resource which results in deadlocks.
701 thread->set_thread_state(_thread_blocked);
702
703 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
704 // the safepoint code might still be waiting for it to block. We need to change the state here,
705 // so it can see that it is at a safepoint.
706
707 // Block until the safepoint operation is completed.
708 Threads_lock->lock_without_safepoint_check();
709
710 // Restore state
711 thread->set_thread_state(state);
712
713 Threads_lock->unlock();
714 break;
715
716 default:
717 fatal(err_msg("Illegal threadstate encountered: %d", state));
718 }
719
720 // Check for pending. async. exceptions or suspends - except if the
721 // thread was blocked inside the VM. has_special_runtime_exit_condition()
722 // is called last since it grabs a lock and we only want to do that when
723 // we must.
724 //
725 // Note: we never deliver an async exception at a polling point as the
726 // compiler may not have an exception handler for it. The polling
727 // code will notice the async and deoptimize and the exception will
728 // be delivered. (Polling at a return point is ok though). Sure is
729 // a lot of bother for a deprecated feature...
730 //
731 // We don't deliver an async exception if the thread state is
732 // _thread_in_native_trans so JNI functions won't be called with
733 // a surprising pending exception. If the thread state is going back to java,
734 // async exception is checked in check_special_condition_for_native_trans().
735
736 if (state != _thread_blocked_trans &&
737 state != _thread_in_vm_trans &&
738 thread->has_special_runtime_exit_condition()) {
739 thread->handle_special_runtime_exit_condition(
740 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
741 }
742 }
743
744 // ------------------------------------------------------------------------------------------------------
745 // Exception handlers
746
747
748 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
749 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
750 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
751 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
752
753 if (ShowSafepointMsgs) {
754 tty->print("handle_polling_page_exception: ");
755 }
756
757 if (PrintSafepointStatistics) {
758 inc_page_trap_count();
759 }
760
761 ThreadSafepointState* state = thread->safepoint_state();
762
763 state->handle_polling_page_exception();
764 }
765
766
767 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
768 if (!timeout_error_printed) {
769 timeout_error_printed = true;
770 // Print out the thread info which didn't reach the safepoint for debugging
771 // purposes (useful when there are lots of threads in the debugger).
772 tty->cr();
773 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
774 if (reason == _spinning_timeout) {
775 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
776 } else if (reason == _blocking_timeout) {
777 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
778 }
779
780 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
781 ThreadSafepointState *cur_state;
782 ResourceMark rm;
783 for(JavaThread *cur_thread = Threads::first(); cur_thread;
784 cur_thread = cur_thread->next()) {
785 cur_state = cur_thread->safepoint_state();
786
787 if (cur_thread->thread_state() != _thread_blocked &&
788 ((reason == _spinning_timeout && cur_state->is_running()) ||
789 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
790 tty->print("# ");
791 cur_thread->print();
792 tty->cr();
793 }
794 }
795 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
796 }
797
798 // To debug the long safepoint, specify both DieOnSafepointTimeout &
799 // ShowMessageBoxOnError.
800 if (DieOnSafepointTimeout) {
801 char msg[1024];
802 VM_Operation *op = VMThread::vm_operation();
803 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
804 SafepointTimeoutDelay,
805 op != NULL ? op->name() : "no vm operation");
806 fatal(msg);
807 }
808 }
809
810
811 // -------------------------------------------------------------------------------------------------------
812 // Implementation of ThreadSafepointState
813
814 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
815 _thread = thread;
816 _type = _running;
817 _has_called_back = false;
818 _at_poll_safepoint = false;
819 }
820
821 void ThreadSafepointState::create(JavaThread *thread) {
822 ThreadSafepointState *state = new ThreadSafepointState(thread);
823 thread->set_safepoint_state(state);
824 }
825
826 void ThreadSafepointState::destroy(JavaThread *thread) {
827 if (thread->safepoint_state()) {
828 delete(thread->safepoint_state());
829 thread->set_safepoint_state(NULL);
830 }
831 }
832
833 void ThreadSafepointState::examine_state_of_thread() {
834 assert(is_running(), "better be running or just have hit safepoint poll");
835
836 JavaThreadState state = _thread->thread_state();
837
838 // Save the state at the start of safepoint processing.
839 _orig_thread_state = state;
840
841 // Check for a thread that is suspended. Note that thread resume tries
842 // to grab the Threads_lock which we own here, so a thread cannot be
843 // resumed during safepoint synchronization.
844
845 // We check to see if this thread is suspended without locking to
846 // avoid deadlocking with a third thread that is waiting for this
847 // thread to be suspended. The third thread can notice the safepoint
848 // that we're trying to start at the beginning of its SR_lock->wait()
849 // call. If that happens, then the third thread will block on the
850 // safepoint while still holding the underlying SR_lock. We won't be
851 // able to get the SR_lock and we'll deadlock.
852 //
853 // We don't need to grab the SR_lock here for two reasons:
854 // 1) The suspend flags are both volatile and are set with an
855 // Atomic::cmpxchg() call so we should see the suspended
856 // state right away.
857 // 2) We're being called from the safepoint polling loop; if
858 // we don't see the suspended state on this iteration, then
859 // we'll come around again.
860 //
861 bool is_suspended = _thread->is_ext_suspended();
862 if (is_suspended) {
863 roll_forward(_at_safepoint);
864 return;
865 }
866
867 // Some JavaThread states have an initial safepoint state of
868 // running, but are actually at a safepoint. We will happily
869 // agree and update the safepoint state here.
870 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
871 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
872 roll_forward(_at_safepoint);
873 return;
874 }
875
876 if (state == _thread_in_vm) {
877 roll_forward(_call_back);
878 return;
879 }
880
881 // All other thread states will continue to run until they
882 // transition and self-block in state _blocked
883 // Safepoint polling in compiled code causes the Java threads to do the same.
884 // Note: new threads may require a malloc so they must be allowed to finish
885
886 assert(is_running(), "examine_state_of_thread on non-running thread");
887 return;
888 }
889
890 // Returns true is thread could not be rolled forward at present position.
891 void ThreadSafepointState::roll_forward(suspend_type type) {
892 _type = type;
893
894 switch(_type) {
895 case _at_safepoint:
896 SafepointSynchronize::signal_thread_at_safepoint();
897 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
898 if (_thread->in_critical()) {
899 // Notice that this thread is in a critical section
900 SafepointSynchronize::increment_jni_active_count();
901 }
902 break;
903
904 case _call_back:
905 set_has_called_back(false);
906 break;
907
908 case _running:
909 default:
910 ShouldNotReachHere();
911 }
912 }
913
914 void ThreadSafepointState::restart() {
915 switch(type()) {
916 case _at_safepoint:
917 case _call_back:
918 break;
919
920 case _running:
921 default:
922 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
923 _thread, _type);
924 _thread->print();
925 ShouldNotReachHere();
926 }
927 _type = _running;
928 set_has_called_back(false);
929 }
930
931
932 void ThreadSafepointState::print_on(outputStream *st) const {
933 const char *s;
934
935 switch(_type) {
936 case _running : s = "_running"; break;
937 case _at_safepoint : s = "_at_safepoint"; break;
938 case _call_back : s = "_call_back"; break;
939 default:
940 ShouldNotReachHere();
941 }
942
943 st->print_cr("Thread: " INTPTR_FORMAT
944 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
945 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
946 _at_poll_safepoint);
947
948 _thread->print_thread_state_on(st);
949 }
950
951
952 // ---------------------------------------------------------------------------------------------------------------------
953
954 // Block the thread at the safepoint poll or poll return.
955 void ThreadSafepointState::handle_polling_page_exception() {
956
957 // Check state. block() will set thread state to thread_in_vm which will
958 // cause the safepoint state _type to become _call_back.
959 assert(type() == ThreadSafepointState::_running,
960 "polling page exception on thread not running state");
961
962 // Step 1: Find the nmethod from the return address
963 if (ShowSafepointMsgs && Verbose) {
964 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
965 }
966 address real_return_addr = thread()->saved_exception_pc();
967
968 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
969 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
970 nmethod* nm = (nmethod*)cb;
971
972 // Find frame of caller
973 frame stub_fr = thread()->last_frame();
974 CodeBlob* stub_cb = stub_fr.cb();
975 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
976 RegisterMap map(thread(), true);
977 frame caller_fr = stub_fr.sender(&map);
978
979 // Should only be poll_return or poll
980 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
981
982 // This is a poll immediately before a return. The exception handling code
983 // has already had the effect of causing the return to occur, so the execution
984 // will continue immediately after the call. In addition, the oopmap at the
985 // return point does not mark the return value as an oop (if it is), so
986 // it needs a handle here to be updated.
987 if( nm->is_at_poll_return(real_return_addr) ) {
988 // See if return type is an oop.
989 bool return_oop = nm->method()->is_returning_oop();
990 Handle return_value;
991 if (return_oop) {
992 // The oop result has been saved on the stack together with all
993 // the other registers. In order to preserve it over GCs we need
994 // to keep it in a handle.
995 oop result = caller_fr.saved_oop_result(&map);
996 assert(result == NULL || result->is_oop(), "must be oop");
997 return_value = Handle(thread(), result);
998 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
999 }
1000
1001 // Block the thread
1002 SafepointSynchronize::block(thread());
1003
1004 // restore oop result, if any
1005 if (return_oop) {
1006 caller_fr.set_saved_oop_result(&map, return_value());
1007 }
1008 }
1009
1010 // This is a safepoint poll. Verify the return address and block.
1011 else {
1012 set_at_poll_safepoint(true);
1013
1014 // verify the blob built the "return address" correctly
1015 assert(real_return_addr == caller_fr.pc(), "must match");
1016
1017 // Block the thread
1018 SafepointSynchronize::block(thread());
1019 set_at_poll_safepoint(false);
1020
1021 // If we have a pending async exception deoptimize the frame
1022 // as otherwise we may never deliver it.
1023 if (thread()->has_async_condition()) {
1024 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1025 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1026 }
1027
1028 // If an exception has been installed we must check for a pending deoptimization
1029 // Deoptimize frame if exception has been thrown.
1030
1031 if (thread()->has_pending_exception() ) {
1032 RegisterMap map(thread(), true);
1033 frame caller_fr = stub_fr.sender(&map);
1034 if (caller_fr.is_deoptimized_frame()) {
1035 // The exception patch will destroy registers that are still
1036 // live and will be needed during deoptimization. Defer the
1037 // Async exception should have deferred the exception until the
1038 // next safepoint which will be detected when we get into
1039 // the interpreter so if we have an exception now things
1040 // are messed up.
1041
1042 fatal("Exception installed and deoptimization is pending");
1043 }
1044 }
1045 }
1046 }
1047
1048
1049 //
1050 // Statistics & Instrumentations
1051 //
1052 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1053 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1054 int SafepointSynchronize::_cur_stat_index = 0;
1055 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1056 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1057 jlong SafepointSynchronize::_max_sync_time = 0;
1058 jlong SafepointSynchronize::_max_vmop_time = 0;
1059 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1060
1061 static jlong cleanup_end_time = 0;
1062 static bool need_to_track_page_armed_status = false;
1063 static bool init_done = false;
1064
1065 // Helper method to print the header.
1066 static void print_header() {
1067 tty->print(" vmop "
1068 "[threads: total initially_running wait_to_block] ");
1069 tty->print("[time: spin block sync cleanup vmop] ");
1070
1071 // no page armed status printed out if it is always armed.
1072 if (need_to_track_page_armed_status) {
1073 tty->print("page_armed ");
1074 }
1075
1076 tty->print_cr("page_trap_count");
1077 }
1078
1079 void SafepointSynchronize::deferred_initialize_stat() {
1080 if (init_done) return;
1081
1082 if (PrintSafepointStatisticsCount <= 0) {
1083 fatal("Wrong PrintSafepointStatisticsCount");
1084 }
1085
1086 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1087 // be printed right away, in which case, _safepoint_stats will regress to
1088 // a single element array. Otherwise, it is a circular ring buffer with default
1089 // size of PrintSafepointStatisticsCount.
1090 int stats_array_size;
1091 if (PrintSafepointStatisticsTimeout > 0) {
1092 stats_array_size = 1;
1093 PrintSafepointStatistics = true;
1094 } else {
1095 stats_array_size = PrintSafepointStatisticsCount;
1096 }
1097 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1098 * sizeof(SafepointStats), mtInternal);
1099 guarantee(_safepoint_stats != NULL,
1100 "not enough memory for safepoint instrumentation data");
1101
1102 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1103 need_to_track_page_armed_status = true;
1104 }
1105 init_done = true;
1106 }
1107
1108 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1109 assert(init_done, "safepoint statistics array hasn't been initialized");
1110 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1111
1112 spstat->_time_stamp = _ts_of_current_safepoint;
1113
1114 VM_Operation *op = VMThread::vm_operation();
1115 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1116 if (op != NULL) {
1117 _safepoint_reasons[spstat->_vmop_type]++;
1118 }
1119
1120 spstat->_nof_total_threads = nof_threads;
1121 spstat->_nof_initial_running_threads = nof_running;
1122 spstat->_nof_threads_hit_page_trap = 0;
1123
1124 // Records the start time of spinning. The real time spent on spinning
1125 // will be adjusted when spin is done. Same trick is applied for time
1126 // spent on waiting for threads to block.
1127 if (nof_running != 0) {
1128 spstat->_time_to_spin = os::javaTimeNanos();
1129 } else {
1130 spstat->_time_to_spin = 0;
1131 }
1132 }
1133
1134 void SafepointSynchronize::update_statistics_on_spin_end() {
1135 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1136
1137 jlong cur_time = os::javaTimeNanos();
1138
1139 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1140 if (spstat->_nof_initial_running_threads != 0) {
1141 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1142 }
1143
1144 if (need_to_track_page_armed_status) {
1145 spstat->_page_armed = (PageArmed == 1);
1146 }
1147
1148 // Records the start time of waiting for to block. Updated when block is done.
1149 if (_waiting_to_block != 0) {
1150 spstat->_time_to_wait_to_block = cur_time;
1151 } else {
1152 spstat->_time_to_wait_to_block = 0;
1153 }
1154 }
1155
1156 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1157 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1158
1159 if (spstat->_nof_threads_wait_to_block != 0) {
1160 spstat->_time_to_wait_to_block = end_time -
1161 spstat->_time_to_wait_to_block;
1162 }
1163
1164 // Records the end time of sync which will be used to calculate the total
1165 // vm operation time. Again, the real time spending in syncing will be deducted
1166 // from the start of the sync time later when end_statistics is called.
1167 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1168 if (spstat->_time_to_sync > _max_sync_time) {
1169 _max_sync_time = spstat->_time_to_sync;
1170 }
1171
1172 spstat->_time_to_do_cleanups = end_time;
1173 }
1174
1175 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1176 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1177
1178 // Record how long spent in cleanup tasks.
1179 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1180
1181 cleanup_end_time = end_time;
1182 }
1183
1184 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1185 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1186
1187 // Update the vm operation time.
1188 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1189 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1190 _max_vmop_time = spstat->_time_to_exec_vmop;
1191 }
1192 // Only the sync time longer than the specified
1193 // PrintSafepointStatisticsTimeout will be printed out right away.
1194 // By default, it is -1 meaning all samples will be put into the list.
1195 if ( PrintSafepointStatisticsTimeout > 0) {
1196 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1197 print_statistics();
1198 }
1199 } else {
1200 // The safepoint statistics will be printed out when the _safepoin_stats
1201 // array fills up.
1202 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1203 print_statistics();
1204 _cur_stat_index = 0;
1205 } else {
1206 _cur_stat_index++;
1207 }
1208 }
1209 }
1210
1211 void SafepointSynchronize::print_statistics() {
1212 SafepointStats* sstats = _safepoint_stats;
1213
1214 for (int index = 0; index <= _cur_stat_index; index++) {
1215 if (index % 30 == 0) {
1216 print_header();
1217 }
1218 sstats = &_safepoint_stats[index];
1219 tty->print("%.3f: ", sstats->_time_stamp);
1220 tty->print("%-26s ["
1221 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1222 " ] ",
1223 sstats->_vmop_type == -1 ? "no vm operation" :
1224 VM_Operation::name(sstats->_vmop_type),
1225 sstats->_nof_total_threads,
1226 sstats->_nof_initial_running_threads,
1227 sstats->_nof_threads_wait_to_block);
1228 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1229 tty->print(" ["
1230 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1231 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1232 INT64_FORMAT_W(6)" ] ",
1233 sstats->_time_to_spin / MICROUNITS,
1234 sstats->_time_to_wait_to_block / MICROUNITS,
1235 sstats->_time_to_sync / MICROUNITS,
1236 sstats->_time_to_do_cleanups / MICROUNITS,
1237 sstats->_time_to_exec_vmop / MICROUNITS);
1238
1239 if (need_to_track_page_armed_status) {
1240 tty->print(INT32_FORMAT" ", sstats->_page_armed);
1241 }
1242 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
1243 }
1244 }
1245
1246 // This method will be called when VM exits. It will first call
1247 // print_statistics to print out the rest of the sampling. Then
1248 // it tries to summarize the sampling.
1249 void SafepointSynchronize::print_stat_on_exit() {
1250 if (_safepoint_stats == NULL) return;
1251
1252 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1253
1254 // During VM exit, end_statistics may not get called and in that
1255 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1256 // don't print it out.
1257 // Approximate the vm op time.
1258 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1259 os::javaTimeNanos() - cleanup_end_time;
1260
1261 if ( PrintSafepointStatisticsTimeout < 0 ||
1262 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1263 print_statistics();
1264 }
1265 tty->cr();
1266
1267 // Print out polling page sampling status.
1268 if (!need_to_track_page_armed_status) {
1269 if (UseCompilerSafepoints) {
1270 tty->print_cr("Polling page always armed");
1271 }
1272 } else {
1273 tty->print_cr("Defer polling page loop count = %d\n",
1274 DeferPollingPageLoopCount);
1275 }
1276
1277 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1278 if (_safepoint_reasons[index] != 0) {
1279 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1280 _safepoint_reasons[index]);
1281 }
1282 }
1283
1284 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1285 _coalesced_vmop_count);
1286 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
1287 _max_sync_time / MICROUNITS);
1288 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1289 INT64_FORMAT_W(5)" ms",
1290 _max_vmop_time / MICROUNITS);
1291 }
1292
1293 // ------------------------------------------------------------------------------------------------
1294 // Non-product code
1295
1296 #ifndef PRODUCT
1297
1298 void SafepointSynchronize::print_state() {
1299 if (_state == _not_synchronized) {
1300 tty->print_cr("not synchronized");
1301 } else if (_state == _synchronizing || _state == _synchronized) {
1302 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1303 "synchronized");
1304
1305 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1306 cur->safepoint_state()->print();
1307 }
1308 }
1309 }
1310
1311 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1312 if (ShowSafepointMsgs) {
1313 va_list ap;
1314 va_start(ap, format);
1315 tty->vprint_cr(format, ap);
1316 va_end(ap);
1317 }
1318 }
1319
1320 #endif // !PRODUCT