1 /*
2 * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "code/icBuffer.hpp"
30 #include "code/nmethod.hpp"
31 #include "code/pcDesc.hpp"
32 #include "code/scopeDesc.hpp"
33 #include "gc_interface/collectedHeap.hpp"
34 #include "interpreter/interpreter.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "memory/universe.inline.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "oops/symbol.hpp"
39 #include "runtime/compilationPolicy.hpp"
40 #include "runtime/deoptimization.hpp"
41 #include "runtime/frame.inline.hpp"
42 #include "runtime/interfaceSupport.hpp"
43 #include "runtime/mutexLocker.hpp"
44 #include "runtime/orderAccess.inline.hpp"
45 #include "runtime/osThread.hpp"
46 #include "runtime/safepoint.hpp"
47 #include "runtime/signature.hpp"
48 #include "runtime/stubCodeGenerator.hpp"
49 #include "runtime/stubRoutines.hpp"
50 #include "runtime/sweeper.hpp"
51 #include "runtime/synchronizer.hpp"
52 #include "runtime/thread.inline.hpp"
53 #include "services/runtimeService.hpp"
54 #include "utilities/events.hpp"
55 #include "utilities/macros.hpp"
56 #ifdef TARGET_ARCH_x86
57 # include "nativeInst_x86.hpp"
58 # include "vmreg_x86.inline.hpp"
59 #endif
60 #ifdef TARGET_ARCH_aarch64
61 # include "nativeInst_aarch64.hpp"
62 # include "vmreg_aarch64.inline.hpp"
63 #endif
64 #ifdef TARGET_ARCH_sparc
65 # include "nativeInst_sparc.hpp"
66 # include "vmreg_sparc.inline.hpp"
67 #endif
68 #ifdef TARGET_ARCH_zero
69 # include "nativeInst_zero.hpp"
70 # include "vmreg_zero.inline.hpp"
71 #endif
72 #ifdef TARGET_ARCH_arm
73 # include "nativeInst_arm.hpp"
74 # include "vmreg_arm.inline.hpp"
75 #endif
76 #ifdef TARGET_ARCH_ppc
77 # include "nativeInst_ppc.hpp"
78 # include "vmreg_ppc.inline.hpp"
79 #endif
80 #if INCLUDE_ALL_GCS
81 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
82 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
83 #endif // INCLUDE_ALL_GCS
84 #ifdef COMPILER1
85 #include "c1/c1_globals.hpp"
86 #endif
87
88 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
89
90 // --------------------------------------------------------------------------------------------------
91 // Implementation of Safepoint begin/end
92
93 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
94 volatile int SafepointSynchronize::_waiting_to_block = 0;
95 volatile int SafepointSynchronize::_safepoint_counter = 0;
96 int SafepointSynchronize::_current_jni_active_count = 0;
97 long SafepointSynchronize::_end_of_last_safepoint = 0;
98 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
99 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
100 static bool timeout_error_printed = false;
101
102 // Roll all threads forward to a safepoint and suspend them all
103 void SafepointSynchronize::begin() {
104
105 Thread* myThread = Thread::current();
106 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
107
108 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
109 _safepoint_begin_time = os::javaTimeNanos();
110 _ts_of_current_safepoint = tty->time_stamp().seconds();
111 }
112
113 #if INCLUDE_ALL_GCS
114 if (UseConcMarkSweepGC) {
115 // In the future we should investigate whether CMS can use the
116 // more-general mechanism below. DLD (01/05).
117 ConcurrentMarkSweepThread::synchronize(false);
118 } else if (UseG1GC) {
119 SuspendibleThreadSet::synchronize();
120 }
121 #endif // INCLUDE_ALL_GCS
122
123 // By getting the Threads_lock, we assure that no threads are about to start or
124 // exit. It is released again in SafepointSynchronize::end().
125 Threads_lock->lock();
126
127 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
128
129 int nof_threads = Threads::number_of_threads();
130
131 if (TraceSafepoint) {
132 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
133 }
134
135 RuntimeService::record_safepoint_begin();
136
137 MutexLocker mu(Safepoint_lock);
138
139 // Reset the count of active JNI critical threads
140 _current_jni_active_count = 0;
141
142 // Set number of threads to wait for, before we initiate the callbacks
143 _waiting_to_block = nof_threads;
144 TryingToBlock = 0 ;
145 int still_running = nof_threads;
146
147 // Save the starting time, so that it can be compared to see if this has taken
148 // too long to complete.
149 jlong safepoint_limit_time = 0;
150 timeout_error_printed = false;
151
152 // PrintSafepointStatisticsTimeout can be specified separately. When
153 // specified, PrintSafepointStatistics will be set to true in
154 // deferred_initialize_stat method. The initialization has to be done
155 // early enough to avoid any races. See bug 6880029 for details.
156 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
157 deferred_initialize_stat();
158 }
159
160 // Begin the process of bringing the system to a safepoint.
161 // Java threads can be in several different states and are
162 // stopped by different mechanisms:
163 //
164 // 1. Running interpreted
165 // The interpeter dispatch table is changed to force it to
166 // check for a safepoint condition between bytecodes.
167 // 2. Running in native code
168 // When returning from the native code, a Java thread must check
169 // the safepoint _state to see if we must block. If the
170 // VM thread sees a Java thread in native, it does
171 // not wait for this thread to block. The order of the memory
172 // writes and reads of both the safepoint state and the Java
173 // threads state is critical. In order to guarantee that the
174 // memory writes are serialized with respect to each other,
175 // the VM thread issues a memory barrier instruction
176 // (on MP systems). In order to avoid the overhead of issuing
177 // a memory barrier for each Java thread making native calls, each Java
178 // thread performs a write to a single memory page after changing
179 // the thread state. The VM thread performs a sequence of
180 // mprotect OS calls which forces all previous writes from all
181 // Java threads to be serialized. This is done in the
182 // os::serialize_thread_states() call. This has proven to be
183 // much more efficient than executing a membar instruction
184 // on every call to native code.
185 // 3. Running compiled Code
186 // Compiled code reads a global (Safepoint Polling) page that
187 // is set to fault if we are trying to get to a safepoint.
188 // 4. Blocked
189 // A thread which is blocked will not be allowed to return from the
190 // block condition until the safepoint operation is complete.
191 // 5. In VM or Transitioning between states
192 // If a Java thread is currently running in the VM or transitioning
193 // between states, the safepointing code will wait for the thread to
194 // block itself when it attempts transitions to a new state.
195 //
196 _state = _synchronizing;
197 OrderAccess::fence();
198
199 // Flush all thread states to memory
200 if (!UseMembar) {
201 os::serialize_thread_states();
202 }
203
204 // Make interpreter safepoint aware
205 Interpreter::notice_safepoints();
206
207 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
208 // Make polling safepoint aware
209 guarantee (PageArmed == 0, "invariant") ;
210 PageArmed = 1 ;
211 os::make_polling_page_unreadable();
212 }
213
214 // Consider using active_processor_count() ... but that call is expensive.
215 int ncpus = os::processor_count() ;
216
217 #ifdef ASSERT
218 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
219 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
220 // Clear the visited flag to ensure that the critical counts are collected properly.
221 cur->set_visited_for_critical_count(false);
222 }
223 #endif // ASSERT
224
225 if (SafepointTimeout)
226 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
227
228 // Iterate through all threads until it have been determined how to stop them all at a safepoint
229 unsigned int iterations = 0;
230 int steps = 0 ;
231 while(still_running > 0) {
232 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
233 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
234 ThreadSafepointState *cur_state = cur->safepoint_state();
235 if (cur_state->is_running()) {
236 cur_state->examine_state_of_thread();
237 if (!cur_state->is_running()) {
238 still_running--;
239 // consider adjusting steps downward:
240 // steps = 0
241 // steps -= NNN
242 // steps >>= 1
243 // steps = MIN(steps, 2000-100)
244 // if (iterations != 0) steps -= NNN
245 }
246 if (TraceSafepoint && Verbose) cur_state->print();
247 }
248 }
249
250 if (PrintSafepointStatistics && iterations == 0) {
251 begin_statistics(nof_threads, still_running);
252 }
253
254 if (still_running > 0) {
255 // Check for if it takes to long
256 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
257 print_safepoint_timeout(_spinning_timeout);
258 }
259
260 // Spin to avoid context switching.
261 // There's a tension between allowing the mutators to run (and rendezvous)
262 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
263 // a mutator might otherwise use profitably to reach a safepoint. Excessive
264 // spinning by the VM thread on a saturated system can increase rendezvous latency.
265 // Blocking or yielding incur their own penalties in the form of context switching
266 // and the resultant loss of $ residency.
267 //
268 // Further complicating matters is that yield() does not work as naively expected
269 // on many platforms -- yield() does not guarantee that any other ready threads
270 // will run. As such we revert yield_all() after some number of iterations.
271 // Yield_all() is implemented as a short unconditional sleep on some platforms.
272 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
273 // can actually increase the time it takes the VM thread to detect that a system-wide
274 // stop-the-world safepoint has been reached. In a pathological scenario such as that
275 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
276 // In that case the mutators will be stalled waiting for the safepoint to complete and the
277 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
278 // will eventually wake up and detect that all mutators are safe, at which point
279 // we'll again make progress.
280 //
281 // Beware too that that the VMThread typically runs at elevated priority.
282 // Its default priority is higher than the default mutator priority.
283 // Obviously, this complicates spinning.
284 //
285 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
286 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
287 //
288 // See the comments in synchronizer.cpp for additional remarks on spinning.
289 //
290 // In the future we might:
291 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
292 // This is tricky as the path used by a thread exiting the JVM (say on
293 // on JNI call-out) simply stores into its state field. The burden
294 // is placed on the VM thread, which must poll (spin).
295 // 2. Find something useful to do while spinning. If the safepoint is GC-related
296 // we might aggressively scan the stacks of threads that are already safe.
297 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
298 // If all the mutators are ONPROC there's no reason to sleep or yield.
299 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
300 // 5. Check system saturation. If the system is not fully saturated then
301 // simply spin and avoid sleep/yield.
302 // 6. As still-running mutators rendezvous they could unpark the sleeping
303 // VMthread. This works well for still-running mutators that become
304 // safe. The VMthread must still poll for mutators that call-out.
305 // 7. Drive the policy on time-since-begin instead of iterations.
306 // 8. Consider making the spin duration a function of the # of CPUs:
307 // Spin = (((ncpus-1) * M) + K) + F(still_running)
308 // Alternately, instead of counting iterations of the outer loop
309 // we could count the # of threads visited in the inner loop, above.
310 // 9. On windows consider using the return value from SwitchThreadTo()
311 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
312
313 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
314 guarantee (PageArmed == 0, "invariant") ;
315 PageArmed = 1 ;
316 os::make_polling_page_unreadable();
317 }
318
319 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
320 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
321 ++steps ;
322 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
323 SpinPause() ; // MP-Polite spin
324 } else
325 if (steps < DeferThrSuspendLoopCount) {
326 os::NakedYield() ;
327 } else {
328 os::yield_all(steps) ;
329 // Alternately, the VM thread could transiently depress its scheduling priority or
330 // transiently increase the priority of the tardy mutator(s).
331 }
332
333 iterations ++ ;
334 }
335 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
336 }
337 assert(still_running == 0, "sanity check");
338
339 if (PrintSafepointStatistics) {
340 update_statistics_on_spin_end();
341 }
342
343 // wait until all threads are stopped
344 while (_waiting_to_block > 0) {
345 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
346 if (!SafepointTimeout || timeout_error_printed) {
347 Safepoint_lock->wait(true); // true, means with no safepoint checks
348 } else {
349 // Compute remaining time
350 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
351
352 // If there is no remaining time, then there is an error
353 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
354 print_safepoint_timeout(_blocking_timeout);
355 }
356 }
357 }
358 assert(_waiting_to_block == 0, "sanity check");
359
360 #ifndef PRODUCT
361 if (SafepointTimeout) {
362 jlong current_time = os::javaTimeNanos();
363 if (safepoint_limit_time < current_time) {
364 tty->print_cr("# SafepointSynchronize: Finished after "
365 INT64_FORMAT_W(6) " ms",
366 ((current_time - safepoint_limit_time) / MICROUNITS +
367 SafepointTimeoutDelay));
368 }
369 }
370 #endif
371
372 assert((_safepoint_counter & 0x1) == 0, "must be even");
373 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
374 _safepoint_counter ++;
375
376 // Record state
377 _state = _synchronized;
378
379 OrderAccess::fence();
380
381 #ifdef ASSERT
382 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
383 // make sure all the threads were visited
384 assert(cur->was_visited_for_critical_count(), "missed a thread");
385 }
386 #endif // ASSERT
387
388 // Update the count of active JNI critical regions
389 GC_locker::set_jni_lock_count(_current_jni_active_count);
390
391 if (TraceSafepoint) {
392 VM_Operation *op = VMThread::vm_operation();
393 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
394 }
395
396 RuntimeService::record_safepoint_synchronized();
397 if (PrintSafepointStatistics) {
398 update_statistics_on_sync_end(os::javaTimeNanos());
399 }
400
401 // Call stuff that needs to be run when a safepoint is just about to be completed
402 do_cleanup_tasks();
403
404 if (PrintSafepointStatistics) {
405 // Record how much time spend on the above cleanup tasks
406 update_statistics_on_cleanup_end(os::javaTimeNanos());
407 }
408 }
409
410 // Wake up all threads, so they are ready to resume execution after the safepoint
411 // operation has been carried out
412 void SafepointSynchronize::end() {
413
414 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
415 assert((_safepoint_counter & 0x1) == 1, "must be odd");
416 _safepoint_counter ++;
417 // memory fence isn't required here since an odd _safepoint_counter
418 // value can do no harm and a fence is issued below anyway.
419
420 DEBUG_ONLY(Thread* myThread = Thread::current();)
421 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
422
423 if (PrintSafepointStatistics) {
424 end_statistics(os::javaTimeNanos());
425 }
426
427 #ifdef ASSERT
428 // A pending_exception cannot be installed during a safepoint. The threads
429 // may install an async exception after they come back from a safepoint into
430 // pending_exception after they unblock. But that should happen later.
431 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
432 assert (!(cur->has_pending_exception() &&
433 cur->safepoint_state()->is_at_poll_safepoint()),
434 "safepoint installed a pending exception");
435 }
436 #endif // ASSERT
437
438 if (PageArmed) {
439 // Make polling safepoint aware
440 os::make_polling_page_readable();
441 PageArmed = 0 ;
442 }
443
444 // Remove safepoint check from interpreter
445 Interpreter::ignore_safepoints();
446
447 {
448 MutexLocker mu(Safepoint_lock);
449
450 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
451
452 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
453 // when they get restarted.
454 _state = _not_synchronized;
455 OrderAccess::fence();
456
457 if (TraceSafepoint) {
458 tty->print_cr("Leaving safepoint region");
459 }
460
461 // Start suspended threads
462 for(JavaThread *current = Threads::first(); current; current = current->next()) {
463 // A problem occurring on Solaris is when attempting to restart threads
464 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
465 // to the next one (since it has been running the longest). We then have
466 // to wait for a cpu to become available before we can continue restarting
467 // threads.
468 // FIXME: This causes the performance of the VM to degrade when active and with
469 // large numbers of threads. Apparently this is due to the synchronous nature
470 // of suspending threads.
471 //
472 // TODO-FIXME: the comments above are vestigial and no longer apply.
473 // Furthermore, using solaris' schedctl in this particular context confers no benefit
474 if (VMThreadHintNoPreempt) {
475 os::hint_no_preempt();
476 }
477 ThreadSafepointState* cur_state = current->safepoint_state();
478 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
479 cur_state->restart();
480 assert(cur_state->is_running(), "safepoint state has not been reset");
481 }
482
483 RuntimeService::record_safepoint_end();
484
485 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
486 // blocked in signal_thread_blocked
487 Threads_lock->unlock();
488
489 }
490 #if INCLUDE_ALL_GCS
491 // If there are any concurrent GC threads resume them.
492 if (UseConcMarkSweepGC) {
493 ConcurrentMarkSweepThread::desynchronize(false);
494 } else if (UseG1GC) {
495 SuspendibleThreadSet::desynchronize();
496 }
497 #endif // INCLUDE_ALL_GCS
498 // record this time so VMThread can keep track how much time has elasped
499 // since last safepoint.
500 _end_of_last_safepoint = os::javaTimeMillis();
501 }
502
503 bool SafepointSynchronize::is_cleanup_needed() {
504 // Need a safepoint if some inline cache buffers is non-empty
505 if (!InlineCacheBuffer::is_empty()) return true;
506 return false;
507 }
508
509
510
511 // Various cleaning tasks that should be done periodically at safepoints
512 void SafepointSynchronize::do_cleanup_tasks() {
513 {
514 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
515 ObjectSynchronizer::deflate_idle_monitors();
516 }
517
518 {
519 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
520 InlineCacheBuffer::update_inline_caches();
521 }
522 {
523 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
524 CompilationPolicy::policy()->do_safepoint_work();
525 }
526
527 {
528 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
529 NMethodSweeper::mark_active_nmethods();
530 }
531
532 if (SymbolTable::needs_rehashing()) {
533 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
534 SymbolTable::rehash_table();
535 }
536
537 if (StringTable::needs_rehashing()) {
538 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
539 StringTable::rehash_table();
540 }
541
542 // rotate log files?
543 if (UseGCLogFileRotation) {
544 gclog_or_tty->rotate_log(false);
545 }
546
547 {
548 // CMS delays purging the CLDG until the beginning of the next safepoint and to
549 // make sure concurrent sweep is done
550 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
551 ClassLoaderDataGraph::purge_if_needed();
552 }
553 }
554
555
556 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
557 switch(state) {
558 case _thread_in_native:
559 // native threads are safe if they have no java stack or have walkable stack
560 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
561
562 // blocked threads should have already have walkable stack
563 case _thread_blocked:
564 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
565 return true;
566
567 default:
568 return false;
569 }
570 }
571
572
573 // See if the thread is running inside a lazy critical native and
574 // update the thread critical count if so. Also set a suspend flag to
575 // cause the native wrapper to return into the JVM to do the unlock
576 // once the native finishes.
577 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
578 if (state == _thread_in_native &&
579 thread->has_last_Java_frame() &&
580 thread->frame_anchor()->walkable()) {
581 // This thread might be in a critical native nmethod so look at
582 // the top of the stack and increment the critical count if it
583 // is.
584 frame wrapper_frame = thread->last_frame();
585 CodeBlob* stub_cb = wrapper_frame.cb();
586 if (stub_cb != NULL &&
587 stub_cb->is_nmethod() &&
588 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
589 // A thread could potentially be in a critical native across
590 // more than one safepoint, so only update the critical state on
591 // the first one. When it returns it will perform the unlock.
592 if (!thread->do_critical_native_unlock()) {
593 #ifdef ASSERT
594 if (!thread->in_critical()) {
595 GC_locker::increment_debug_jni_lock_count();
596 }
597 #endif
598 thread->enter_critical();
599 // Make sure the native wrapper calls back on return to
600 // perform the needed critical unlock.
601 thread->set_critical_native_unlock();
602 }
603 }
604 }
605 }
606
607
608
609 // -------------------------------------------------------------------------------------------------------
610 // Implementation of Safepoint callback point
611
612 void SafepointSynchronize::block(JavaThread *thread) {
613 assert(thread != NULL, "thread must be set");
614 assert(thread->is_Java_thread(), "not a Java thread");
615
616 // Threads shouldn't block if they are in the middle of printing, but...
617 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
618
619 // Only bail from the block() call if the thread is gone from the
620 // thread list; starting to exit should still block.
621 if (thread->is_terminated()) {
622 // block current thread if we come here from native code when VM is gone
623 thread->block_if_vm_exited();
624
625 // otherwise do nothing
626 return;
627 }
628
629 JavaThreadState state = thread->thread_state();
630 thread->frame_anchor()->make_walkable(thread);
631
632 // Check that we have a valid thread_state at this point
633 switch(state) {
634 case _thread_in_vm_trans:
635 case _thread_in_Java: // From compiled code
636
637 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
638 // we pretend we are still in the VM.
639 thread->set_thread_state(_thread_in_vm);
640
641 if (is_synchronizing()) {
642 Atomic::inc (&TryingToBlock) ;
643 }
644
645 // We will always be holding the Safepoint_lock when we are examine the state
646 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
647 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
648 Safepoint_lock->lock_without_safepoint_check();
649 if (is_synchronizing()) {
650 // Decrement the number of threads to wait for and signal vm thread
651 assert(_waiting_to_block > 0, "sanity check");
652 _waiting_to_block--;
653 thread->safepoint_state()->set_has_called_back(true);
654
655 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
656 if (thread->in_critical()) {
657 // Notice that this thread is in a critical section
658 increment_jni_active_count();
659 }
660
661 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
662 if (_waiting_to_block == 0) {
663 Safepoint_lock->notify_all();
664 }
665 }
666
667 // We transition the thread to state _thread_blocked here, but
668 // we can't do our usual check for external suspension and then
669 // self-suspend after the lock_without_safepoint_check() call
670 // below because we are often called during transitions while
671 // we hold different locks. That would leave us suspended while
672 // holding a resource which results in deadlocks.
673 thread->set_thread_state(_thread_blocked);
674 Safepoint_lock->unlock();
675
676 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
677 // the entire safepoint, the threads will all line up here during the safepoint.
678 Threads_lock->lock_without_safepoint_check();
679 // restore original state. This is important if the thread comes from compiled code, so it
680 // will continue to execute with the _thread_in_Java state.
681 thread->set_thread_state(state);
682 Threads_lock->unlock();
683 break;
684
685 case _thread_in_native_trans:
686 case _thread_blocked_trans:
687 case _thread_new_trans:
688 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
689 thread->print_thread_state();
690 fatal("Deadlock in safepoint code. "
691 "Should have called back to the VM before blocking.");
692 }
693
694 // We transition the thread to state _thread_blocked here, but
695 // we can't do our usual check for external suspension and then
696 // self-suspend after the lock_without_safepoint_check() call
697 // below because we are often called during transitions while
698 // we hold different locks. That would leave us suspended while
699 // holding a resource which results in deadlocks.
700 thread->set_thread_state(_thread_blocked);
701
702 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
703 // the safepoint code might still be waiting for it to block. We need to change the state here,
704 // so it can see that it is at a safepoint.
705
706 // Block until the safepoint operation is completed.
707 Threads_lock->lock_without_safepoint_check();
708
709 // Restore state
710 thread->set_thread_state(state);
711
712 Threads_lock->unlock();
713 break;
714
715 default:
716 fatal(err_msg("Illegal threadstate encountered: %d", state));
717 }
718
719 // Check for pending. async. exceptions or suspends - except if the
720 // thread was blocked inside the VM. has_special_runtime_exit_condition()
721 // is called last since it grabs a lock and we only want to do that when
722 // we must.
723 //
724 // Note: we never deliver an async exception at a polling point as the
725 // compiler may not have an exception handler for it. The polling
726 // code will notice the async and deoptimize and the exception will
727 // be delivered. (Polling at a return point is ok though). Sure is
728 // a lot of bother for a deprecated feature...
729 //
730 // We don't deliver an async exception if the thread state is
731 // _thread_in_native_trans so JNI functions won't be called with
732 // a surprising pending exception. If the thread state is going back to java,
733 // async exception is checked in check_special_condition_for_native_trans().
734
735 if (state != _thread_blocked_trans &&
736 state != _thread_in_vm_trans &&
737 thread->has_special_runtime_exit_condition()) {
738 thread->handle_special_runtime_exit_condition(
739 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
740 }
741 }
742
743 // ------------------------------------------------------------------------------------------------------
744 // Exception handlers
745
746
747 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
748 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
749 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
750 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
751
752 if (ShowSafepointMsgs) {
753 tty->print("handle_polling_page_exception: ");
754 }
755
756 if (PrintSafepointStatistics) {
757 inc_page_trap_count();
758 }
759
760 ThreadSafepointState* state = thread->safepoint_state();
761
762 state->handle_polling_page_exception();
763 }
764
765
766 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
767 if (!timeout_error_printed) {
768 timeout_error_printed = true;
769 // Print out the thread infor which didn't reach the safepoint for debugging
770 // purposes (useful when there are lots of threads in the debugger).
771 tty->cr();
772 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
773 if (reason == _spinning_timeout) {
774 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
775 } else if (reason == _blocking_timeout) {
776 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
777 }
778
779 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
780 ThreadSafepointState *cur_state;
781 ResourceMark rm;
782 for(JavaThread *cur_thread = Threads::first(); cur_thread;
783 cur_thread = cur_thread->next()) {
784 cur_state = cur_thread->safepoint_state();
785
786 if (cur_thread->thread_state() != _thread_blocked &&
787 ((reason == _spinning_timeout && cur_state->is_running()) ||
788 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
789 tty->print("# ");
790 cur_thread->print();
791 tty->cr();
792 }
793 }
794 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
795 }
796
797 // To debug the long safepoint, specify both DieOnSafepointTimeout &
798 // ShowMessageBoxOnError.
799 if (DieOnSafepointTimeout) {
800 char msg[1024];
801 VM_Operation *op = VMThread::vm_operation();
802 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
803 SafepointTimeoutDelay,
804 op != NULL ? op->name() : "no vm operation");
805 fatal(msg);
806 }
807 }
808
809
810 // -------------------------------------------------------------------------------------------------------
811 // Implementation of ThreadSafepointState
812
813 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
814 _thread = thread;
815 _type = _running;
816 _has_called_back = false;
817 _at_poll_safepoint = false;
818 }
819
820 void ThreadSafepointState::create(JavaThread *thread) {
821 ThreadSafepointState *state = new ThreadSafepointState(thread);
822 thread->set_safepoint_state(state);
823 }
824
825 void ThreadSafepointState::destroy(JavaThread *thread) {
826 if (thread->safepoint_state()) {
827 delete(thread->safepoint_state());
828 thread->set_safepoint_state(NULL);
829 }
830 }
831
832 void ThreadSafepointState::examine_state_of_thread() {
833 assert(is_running(), "better be running or just have hit safepoint poll");
834
835 JavaThreadState state = _thread->thread_state();
836
837 // Save the state at the start of safepoint processing.
838 _orig_thread_state = state;
839
840 // Check for a thread that is suspended. Note that thread resume tries
841 // to grab the Threads_lock which we own here, so a thread cannot be
842 // resumed during safepoint synchronization.
843
844 // We check to see if this thread is suspended without locking to
845 // avoid deadlocking with a third thread that is waiting for this
846 // thread to be suspended. The third thread can notice the safepoint
847 // that we're trying to start at the beginning of its SR_lock->wait()
848 // call. If that happens, then the third thread will block on the
849 // safepoint while still holding the underlying SR_lock. We won't be
850 // able to get the SR_lock and we'll deadlock.
851 //
852 // We don't need to grab the SR_lock here for two reasons:
853 // 1) The suspend flags are both volatile and are set with an
854 // Atomic::cmpxchg() call so we should see the suspended
855 // state right away.
856 // 2) We're being called from the safepoint polling loop; if
857 // we don't see the suspended state on this iteration, then
858 // we'll come around again.
859 //
860 bool is_suspended = _thread->is_ext_suspended();
861 if (is_suspended) {
862 roll_forward(_at_safepoint);
863 return;
864 }
865
866 // Some JavaThread states have an initial safepoint state of
867 // running, but are actually at a safepoint. We will happily
868 // agree and update the safepoint state here.
869 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
870 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
871 roll_forward(_at_safepoint);
872 return;
873 }
874
875 if (state == _thread_in_vm) {
876 roll_forward(_call_back);
877 return;
878 }
879
880 // All other thread states will continue to run until they
881 // transition and self-block in state _blocked
882 // Safepoint polling in compiled code causes the Java threads to do the same.
883 // Note: new threads may require a malloc so they must be allowed to finish
884
885 assert(is_running(), "examine_state_of_thread on non-running thread");
886 return;
887 }
888
889 // Returns true is thread could not be rolled forward at present position.
890 void ThreadSafepointState::roll_forward(suspend_type type) {
891 _type = type;
892
893 switch(_type) {
894 case _at_safepoint:
895 SafepointSynchronize::signal_thread_at_safepoint();
896 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
897 if (_thread->in_critical()) {
898 // Notice that this thread is in a critical section
899 SafepointSynchronize::increment_jni_active_count();
900 }
901 break;
902
903 case _call_back:
904 set_has_called_back(false);
905 break;
906
907 case _running:
908 default:
909 ShouldNotReachHere();
910 }
911 }
912
913 void ThreadSafepointState::restart() {
914 switch(type()) {
915 case _at_safepoint:
916 case _call_back:
917 break;
918
919 case _running:
920 default:
921 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
922 _thread, _type);
923 _thread->print();
924 ShouldNotReachHere();
925 }
926 _type = _running;
927 set_has_called_back(false);
928 }
929
930
931 void ThreadSafepointState::print_on(outputStream *st) const {
932 const char *s = NULL;
933
934 switch(_type) {
935 case _running : s = "_running"; break;
936 case _at_safepoint : s = "_at_safepoint"; break;
937 case _call_back : s = "_call_back"; break;
938 default:
939 ShouldNotReachHere();
940 }
941
942 st->print_cr("Thread: " INTPTR_FORMAT
943 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
944 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
945 _at_poll_safepoint);
946
947 _thread->print_thread_state_on(st);
948 }
949
950
951 // ---------------------------------------------------------------------------------------------------------------------
952
953 // Block the thread at the safepoint poll or poll return.
954 void ThreadSafepointState::handle_polling_page_exception() {
955
956 // Check state. block() will set thread state to thread_in_vm which will
957 // cause the safepoint state _type to become _call_back.
958 assert(type() == ThreadSafepointState::_running,
959 "polling page exception on thread not running state");
960
961 // Step 1: Find the nmethod from the return address
962 if (ShowSafepointMsgs && Verbose) {
963 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
964 }
965 address real_return_addr = thread()->saved_exception_pc();
966
967 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
968 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
969 nmethod* nm = (nmethod*)cb;
970
971 // Find frame of caller
972 frame stub_fr = thread()->last_frame();
973 CodeBlob* stub_cb = stub_fr.cb();
974 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
975 RegisterMap map(thread(), true);
976 frame caller_fr = stub_fr.sender(&map);
977
978 // Should only be poll_return or poll
979 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
980
981 // This is a poll immediately before a return. The exception handling code
982 // has already had the effect of causing the return to occur, so the execution
983 // will continue immediately after the call. In addition, the oopmap at the
984 // return point does not mark the return value as an oop (if it is), so
985 // it needs a handle here to be updated.
986 if( nm->is_at_poll_return(real_return_addr) ) {
987 // See if return type is an oop.
988 bool return_oop = nm->method()->is_returning_oop();
989 Handle return_value;
990 if (return_oop) {
991 // The oop result has been saved on the stack together with all
992 // the other registers. In order to preserve it over GCs we need
993 // to keep it in a handle.
994 oop result = caller_fr.saved_oop_result(&map);
995 assert(result == NULL || result->is_oop(), "must be oop");
996 return_value = Handle(thread(), result);
997 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
998 }
999
1000 // Block the thread
1001 SafepointSynchronize::block(thread());
1002
1003 // restore oop result, if any
1004 if (return_oop) {
1005 caller_fr.set_saved_oop_result(&map, return_value());
1006 }
1007 }
1008
1009 // This is a safepoint poll. Verify the return address and block.
1010 else {
1011 set_at_poll_safepoint(true);
1012
1013 // verify the blob built the "return address" correctly
1014 assert(real_return_addr == caller_fr.pc(), "must match");
1015
1016 // Block the thread
1017 SafepointSynchronize::block(thread());
1018 set_at_poll_safepoint(false);
1019
1020 // If we have a pending async exception deoptimize the frame
1021 // as otherwise we may never deliver it.
1022 if (thread()->has_async_condition()) {
1023 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1024 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1025 }
1026
1027 // If an exception has been installed we must check for a pending deoptimization
1028 // Deoptimize frame if exception has been thrown.
1029
1030 if (thread()->has_pending_exception() ) {
1031 RegisterMap map(thread(), true);
1032 frame caller_fr = stub_fr.sender(&map);
1033 if (caller_fr.is_deoptimized_frame()) {
1034 // The exception patch will destroy registers that are still
1035 // live and will be needed during deoptimization. Defer the
1036 // Async exception should have defered the exception until the
1037 // next safepoint which will be detected when we get into
1038 // the interpreter so if we have an exception now things
1039 // are messed up.
1040
1041 fatal("Exception installed and deoptimization is pending");
1042 }
1043 }
1044 }
1045 }
1046
1047
1048 //
1049 // Statistics & Instrumentations
1050 //
1051 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1052 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1053 int SafepointSynchronize::_cur_stat_index = 0;
1054 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1055 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1056 jlong SafepointSynchronize::_max_sync_time = 0;
1057 jlong SafepointSynchronize::_max_vmop_time = 0;
1058 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1059
1060 static jlong cleanup_end_time = 0;
1061 static bool need_to_track_page_armed_status = false;
1062 static bool init_done = false;
1063
1064 // Helper method to print the header.
1065 static void print_header() {
1066 tty->print(" vmop "
1067 "[threads: total initially_running wait_to_block] ");
1068 tty->print("[time: spin block sync cleanup vmop] ");
1069
1070 // no page armed status printed out if it is always armed.
1071 if (need_to_track_page_armed_status) {
1072 tty->print("page_armed ");
1073 }
1074
1075 tty->print_cr("page_trap_count");
1076 }
1077
1078 void SafepointSynchronize::deferred_initialize_stat() {
1079 if (init_done) return;
1080
1081 if (PrintSafepointStatisticsCount <= 0) {
1082 fatal("Wrong PrintSafepointStatisticsCount");
1083 }
1084
1085 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1086 // be printed right away, in which case, _safepoint_stats will regress to
1087 // a single element array. Otherwise, it is a circular ring buffer with default
1088 // size of PrintSafepointStatisticsCount.
1089 int stats_array_size;
1090 if (PrintSafepointStatisticsTimeout > 0) {
1091 stats_array_size = 1;
1092 PrintSafepointStatistics = true;
1093 } else {
1094 stats_array_size = PrintSafepointStatisticsCount;
1095 }
1096 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1097 * sizeof(SafepointStats), mtInternal);
1098 guarantee(_safepoint_stats != NULL,
1099 "not enough memory for safepoint instrumentation data");
1100
1101 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1102 need_to_track_page_armed_status = true;
1103 }
1104 init_done = true;
1105 }
1106
1107 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1108 assert(init_done, "safepoint statistics array hasn't been initialized");
1109 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1110
1111 spstat->_time_stamp = _ts_of_current_safepoint;
1112
1113 VM_Operation *op = VMThread::vm_operation();
1114 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1115 if (op != NULL) {
1116 _safepoint_reasons[spstat->_vmop_type]++;
1117 }
1118
1119 spstat->_nof_total_threads = nof_threads;
1120 spstat->_nof_initial_running_threads = nof_running;
1121 spstat->_nof_threads_hit_page_trap = 0;
1122
1123 // Records the start time of spinning. The real time spent on spinning
1124 // will be adjusted when spin is done. Same trick is applied for time
1125 // spent on waiting for threads to block.
1126 if (nof_running != 0) {
1127 spstat->_time_to_spin = os::javaTimeNanos();
1128 } else {
1129 spstat->_time_to_spin = 0;
1130 }
1131 }
1132
1133 void SafepointSynchronize::update_statistics_on_spin_end() {
1134 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1135
1136 jlong cur_time = os::javaTimeNanos();
1137
1138 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1139 if (spstat->_nof_initial_running_threads != 0) {
1140 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1141 }
1142
1143 if (need_to_track_page_armed_status) {
1144 spstat->_page_armed = (PageArmed == 1);
1145 }
1146
1147 // Records the start time of waiting for to block. Updated when block is done.
1148 if (_waiting_to_block != 0) {
1149 spstat->_time_to_wait_to_block = cur_time;
1150 } else {
1151 spstat->_time_to_wait_to_block = 0;
1152 }
1153 }
1154
1155 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1156 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1157
1158 if (spstat->_nof_threads_wait_to_block != 0) {
1159 spstat->_time_to_wait_to_block = end_time -
1160 spstat->_time_to_wait_to_block;
1161 }
1162
1163 // Records the end time of sync which will be used to calculate the total
1164 // vm operation time. Again, the real time spending in syncing will be deducted
1165 // from the start of the sync time later when end_statistics is called.
1166 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1167 if (spstat->_time_to_sync > _max_sync_time) {
1168 _max_sync_time = spstat->_time_to_sync;
1169 }
1170
1171 spstat->_time_to_do_cleanups = end_time;
1172 }
1173
1174 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1175 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1176
1177 // Record how long spent in cleanup tasks.
1178 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1179
1180 cleanup_end_time = end_time;
1181 }
1182
1183 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1184 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1185
1186 // Update the vm operation time.
1187 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1188 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1189 _max_vmop_time = spstat->_time_to_exec_vmop;
1190 }
1191 // Only the sync time longer than the specified
1192 // PrintSafepointStatisticsTimeout will be printed out right away.
1193 // By default, it is -1 meaning all samples will be put into the list.
1194 if ( PrintSafepointStatisticsTimeout > 0) {
1195 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1196 print_statistics();
1197 }
1198 } else {
1199 // The safepoint statistics will be printed out when the _safepoin_stats
1200 // array fills up.
1201 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1202 print_statistics();
1203 _cur_stat_index = 0;
1204 } else {
1205 _cur_stat_index++;
1206 }
1207 }
1208 }
1209
1210 void SafepointSynchronize::print_statistics() {
1211 SafepointStats* sstats = _safepoint_stats;
1212
1213 for (int index = 0; index <= _cur_stat_index; index++) {
1214 if (index % 30 == 0) {
1215 print_header();
1216 }
1217 sstats = &_safepoint_stats[index];
1218 tty->print("%.3f: ", sstats->_time_stamp);
1219 tty->print("%-26s ["
1220 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1221 " ] ",
1222 sstats->_vmop_type == -1 ? "no vm operation" :
1223 VM_Operation::name(sstats->_vmop_type),
1224 sstats->_nof_total_threads,
1225 sstats->_nof_initial_running_threads,
1226 sstats->_nof_threads_wait_to_block);
1227 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1228 tty->print(" ["
1229 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1230 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1231 INT64_FORMAT_W(6)" ] ",
1232 sstats->_time_to_spin / MICROUNITS,
1233 sstats->_time_to_wait_to_block / MICROUNITS,
1234 sstats->_time_to_sync / MICROUNITS,
1235 sstats->_time_to_do_cleanups / MICROUNITS,
1236 sstats->_time_to_exec_vmop / MICROUNITS);
1237
1238 if (need_to_track_page_armed_status) {
1239 tty->print(INT32_FORMAT" ", sstats->_page_armed);
1240 }
1241 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
1242 }
1243 }
1244
1245 // This method will be called when VM exits. It will first call
1246 // print_statistics to print out the rest of the sampling. Then
1247 // it tries to summarize the sampling.
1248 void SafepointSynchronize::print_stat_on_exit() {
1249 if (_safepoint_stats == NULL) return;
1250
1251 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1252
1253 // During VM exit, end_statistics may not get called and in that
1254 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1255 // don't print it out.
1256 // Approximate the vm op time.
1257 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1258 os::javaTimeNanos() - cleanup_end_time;
1259
1260 if ( PrintSafepointStatisticsTimeout < 0 ||
1261 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1262 print_statistics();
1263 }
1264 tty->cr();
1265
1266 // Print out polling page sampling status.
1267 if (!need_to_track_page_armed_status) {
1268 if (UseCompilerSafepoints) {
1269 tty->print_cr("Polling page always armed");
1270 }
1271 } else {
1272 tty->print_cr("Defer polling page loop count = %d\n",
1273 DeferPollingPageLoopCount);
1274 }
1275
1276 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1277 if (_safepoint_reasons[index] != 0) {
1278 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1279 _safepoint_reasons[index]);
1280 }
1281 }
1282
1283 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1284 _coalesced_vmop_count);
1285 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
1286 _max_sync_time / MICROUNITS);
1287 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1288 INT64_FORMAT_W(5)" ms",
1289 _max_vmop_time / MICROUNITS);
1290 }
1291
1292 // ------------------------------------------------------------------------------------------------
1293 // Non-product code
1294
1295 #ifndef PRODUCT
1296
1297 void SafepointSynchronize::print_state() {
1298 if (_state == _not_synchronized) {
1299 tty->print_cr("not synchronized");
1300 } else if (_state == _synchronizing || _state == _synchronized) {
1301 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1302 "synchronized");
1303
1304 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1305 cur->safepoint_state()->print();
1306 }
1307 }
1308 }
1309
1310 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1311 if (ShowSafepointMsgs) {
1312 va_list ap;
1313 va_start(ap, format);
1314 tty->vprint_cr(format, ap);
1315 va_end(ap);
1316 }
1317 }
1318
1319 #endif // !PRODUCT