1 /*
2 * Copyright (c) 1997, 2011, 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/systemDictionary.hpp"
27 #include "code/codeCache.hpp"
28 #include "code/icBuffer.hpp"
29 #include "code/nmethod.hpp"
30 #include "code/pcDesc.hpp"
31 #include "code/scopeDesc.hpp"
32 #include "gc_interface/collectedHeap.hpp"
33 #include "interpreter/interpreter.hpp"
34 #include "memory/resourceArea.hpp"
35 #include "memory/universe.inline.hpp"
36 #include "oops/oop.inline.hpp"
37 #include "oops/symbol.hpp"
38 #include "runtime/compilationPolicy.hpp"
39 #include "runtime/deoptimization.hpp"
40 #include "runtime/frame.inline.hpp"
41 #include "runtime/interfaceSupport.hpp"
42 #include "runtime/mutexLocker.hpp"
43 #include "runtime/osThread.hpp"
44 #include "runtime/safepoint.hpp"
45 #include "runtime/signature.hpp"
46 #include "runtime/stubCodeGenerator.hpp"
47 #include "runtime/stubRoutines.hpp"
48 #include "runtime/sweeper.hpp"
49 #include "runtime/synchronizer.hpp"
50 #include "services/runtimeService.hpp"
51 #include "utilities/events.hpp"
52 #ifdef TARGET_ARCH_x86
53 # include "nativeInst_x86.hpp"
54 # include "vmreg_x86.inline.hpp"
55 #endif
56 #ifdef TARGET_ARCH_sparc
57 # include "nativeInst_sparc.hpp"
58 # include "vmreg_sparc.inline.hpp"
59 #endif
60 #ifdef TARGET_ARCH_zero
61 # include "nativeInst_zero.hpp"
62 # include "vmreg_zero.inline.hpp"
63 #endif
64 #ifdef TARGET_ARCH_arm
65 # include "nativeInst_arm.hpp"
66 # include "vmreg_arm.inline.hpp"
67 #endif
68 #ifdef TARGET_ARCH_ppc
69 # include "nativeInst_ppc.hpp"
70 # include "vmreg_ppc.inline.hpp"
71 #endif
72 #ifdef TARGET_OS_FAMILY_linux
73 # include "thread_linux.inline.hpp"
74 #endif
75 #ifdef TARGET_OS_FAMILY_solaris
76 # include "thread_solaris.inline.hpp"
77 #endif
78 #ifdef TARGET_OS_FAMILY_windows
79 # include "thread_windows.inline.hpp"
80 #endif
81 #ifndef SERIALGC
82 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
83 #include "gc_implementation/shared/concurrentGCThread.hpp"
84 #endif
85 #ifdef COMPILER1
86 #include "c1/c1_globals.hpp"
87 #endif
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 long SafepointSynchronize::_end_of_last_safepoint = 0;
96 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
97 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
98 static bool timeout_error_printed = false;
99
100 // Roll all threads forward to a safepoint and suspend them all
101 void SafepointSynchronize::begin() {
102
103 Thread* myThread = Thread::current();
104 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
105
106 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
107 _safepoint_begin_time = os::javaTimeNanos();
108 _ts_of_current_safepoint = tty->time_stamp().seconds();
109 }
110
111 #ifndef SERIALGC
112 if (UseConcMarkSweepGC) {
113 // In the future we should investigate whether CMS can use the
114 // more-general mechanism below. DLD (01/05).
115 ConcurrentMarkSweepThread::synchronize(false);
116 } else if (UseG1GC) {
117 ConcurrentGCThread::safepoint_synchronize();
118 }
119 #endif // SERIALGC
120
121 // By getting the Threads_lock, we assure that no threads are about to start or
122 // exit. It is released again in SafepointSynchronize::end().
123 Threads_lock->lock();
124
125 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
126
127 int nof_threads = Threads::number_of_threads();
128
129 if (TraceSafepoint) {
130 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
131 }
132
133 RuntimeService::record_safepoint_begin();
134
135 {
136 MutexLocker mu(Safepoint_lock);
137
138 // Set number of threads to wait for, before we initiate the callbacks
139 _waiting_to_block = nof_threads;
140 TryingToBlock = 0 ;
141 int still_running = nof_threads;
142
143 // Save the starting time, so that it can be compared to see if this has taken
144 // too long to complete.
145 jlong safepoint_limit_time;
146 timeout_error_printed = false;
147
148 // PrintSafepointStatisticsTimeout can be specified separately. When
149 // specified, PrintSafepointStatistics will be set to true in
150 // deferred_initialize_stat method. The initialization has to be done
151 // early enough to avoid any races. See bug 6880029 for details.
152 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
153 deferred_initialize_stat();
154 }
155
156 // Begin the process of bringing the system to a safepoint.
157 // Java threads can be in several different states and are
158 // stopped by different mechanisms:
159 //
160 // 1. Running interpreted
161 // The interpeter dispatch table is changed to force it to
162 // check for a safepoint condition between bytecodes.
163 // 2. Running in native code
164 // When returning from the native code, a Java thread must check
165 // the safepoint _state to see if we must block. If the
166 // VM thread sees a Java thread in native, it does
167 // not wait for this thread to block. The order of the memory
168 // writes and reads of both the safepoint state and the Java
169 // threads state is critical. In order to guarantee that the
170 // memory writes are serialized with respect to each other,
171 // the VM thread issues a memory barrier instruction
172 // (on MP systems). In order to avoid the overhead of issuing
173 // a memory barrier for each Java thread making native calls, each Java
174 // thread performs a write to a single memory page after changing
175 // the thread state. The VM thread performs a sequence of
176 // mprotect OS calls which forces all previous writes from all
177 // Java threads to be serialized. This is done in the
178 // os::serialize_thread_states() call. This has proven to be
179 // much more efficient than executing a membar instruction
180 // on every call to native code.
181 // 3. Running compiled Code
182 // Compiled code reads a global (Safepoint Polling) page that
183 // is set to fault if we are trying to get to a safepoint.
184 // 4. Blocked
185 // A thread which is blocked will not be allowed to return from the
186 // block condition until the safepoint operation is complete.
187 // 5. In VM or Transitioning between states
188 // If a Java thread is currently running in the VM or transitioning
189 // between states, the safepointing code will wait for the thread to
190 // block itself when it attempts transitions to a new state.
191 //
192 _state = _synchronizing;
193 OrderAccess::fence();
194
195 // Flush all thread states to memory
196 if (!UseMembar) {
197 os::serialize_thread_states();
198 }
199
200 // Make interpreter safepoint aware
201 Interpreter::notice_safepoints();
202
203 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
204 // Make polling safepoint aware
205 guarantee (PageArmed == 0, "invariant") ;
206 PageArmed = 1 ;
207 os::make_polling_page_unreadable();
208 }
209
210 // Consider using active_processor_count() ... but that call is expensive.
211 int ncpus = os::processor_count() ;
212
213 #ifdef ASSERT
214 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
215 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
216 }
217 #endif // ASSERT
218
219 if (SafepointTimeout)
220 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
221
222 // Iterate through all threads until it have been determined how to stop them all at a safepoint
223 unsigned int iterations = 0;
224 int steps = 0 ;
225 while(still_running > 0) {
226 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
227 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
228 ThreadSafepointState *cur_state = cur->safepoint_state();
229 if (cur_state->is_running()) {
230 cur_state->examine_state_of_thread();
231 if (!cur_state->is_running()) {
232 still_running--;
233 // consider adjusting steps downward:
234 // steps = 0
235 // steps -= NNN
236 // steps >>= 1
237 // steps = MIN(steps, 2000-100)
238 // if (iterations != 0) steps -= NNN
239 }
240 if (TraceSafepoint && Verbose) cur_state->print();
241 }
242 }
243
244 if (PrintSafepointStatistics && iterations == 0) {
245 begin_statistics(nof_threads, still_running);
246 }
247
248 if (still_running > 0) {
249 // Check for if it takes to long
250 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
251 print_safepoint_timeout(_spinning_timeout);
252 }
253
254 // Spin to avoid context switching.
255 // There's a tension between allowing the mutators to run (and rendezvous)
256 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
257 // a mutator might otherwise use profitably to reach a safepoint. Excessive
258 // spinning by the VM thread on a saturated system can increase rendezvous latency.
259 // Blocking or yielding incur their own penalties in the form of context switching
260 // and the resultant loss of $ residency.
261 //
262 // Further complicating matters is that yield() does not work as naively expected
263 // on many platforms -- yield() does not guarantee that any other ready threads
264 // will run. As such we revert yield_all() after some number of iterations.
265 // Yield_all() is implemented as a short unconditional sleep on some platforms.
266 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
267 // can actually increase the time it takes the VM thread to detect that a system-wide
268 // stop-the-world safepoint has been reached. In a pathological scenario such as that
269 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
270 // In that case the mutators will be stalled waiting for the safepoint to complete and the
271 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
272 // will eventually wake up and detect that all mutators are safe, at which point
273 // we'll again make progress.
274 //
275 // Beware too that that the VMThread typically runs at elevated priority.
276 // Its default priority is higher than the default mutator priority.
277 // Obviously, this complicates spinning.
278 //
279 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
280 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
281 //
282 // See the comments in synchronizer.cpp for additional remarks on spinning.
283 //
284 // In the future we might:
285 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
286 // This is tricky as the path used by a thread exiting the JVM (say on
287 // on JNI call-out) simply stores into its state field. The burden
288 // is placed on the VM thread, which must poll (spin).
289 // 2. Find something useful to do while spinning. If the safepoint is GC-related
290 // we might aggressively scan the stacks of threads that are already safe.
291 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
292 // If all the mutators are ONPROC there's no reason to sleep or yield.
293 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
294 // 5. Check system saturation. If the system is not fully saturated then
295 // simply spin and avoid sleep/yield.
296 // 6. As still-running mutators rendezvous they could unpark the sleeping
297 // VMthread. This works well for still-running mutators that become
298 // safe. The VMthread must still poll for mutators that call-out.
299 // 7. Drive the policy on time-since-begin instead of iterations.
300 // 8. Consider making the spin duration a function of the # of CPUs:
301 // Spin = (((ncpus-1) * M) + K) + F(still_running)
302 // Alternately, instead of counting iterations of the outer loop
303 // we could count the # of threads visited in the inner loop, above.
304 // 9. On windows consider using the return value from SwitchThreadTo()
305 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
306
307 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
308 guarantee (PageArmed == 0, "invariant") ;
309 PageArmed = 1 ;
310 os::make_polling_page_unreadable();
311 }
312
313 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
314 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
315 ++steps ;
316 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
317 SpinPause() ; // MP-Polite spin
318 } else
319 if (steps < DeferThrSuspendLoopCount) {
320 os::NakedYield() ;
321 } else {
322 os::yield_all(steps) ;
323 // Alternately, the VM thread could transiently depress its scheduling priority or
324 // transiently increase the priority of the tardy mutator(s).
325 }
326
327 iterations ++ ;
328 }
329 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
330 }
331 assert(still_running == 0, "sanity check");
332
333 if (PrintSafepointStatistics) {
334 update_statistics_on_spin_end();
335 }
336
337 // wait until all threads are stopped
338 while (_waiting_to_block > 0) {
339 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
340 if (!SafepointTimeout || timeout_error_printed) {
341 Safepoint_lock->wait(true); // true, means with no safepoint checks
342 } else {
343 // Compute remaining time
344 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
345
346 // If there is no remaining time, then there is an error
347 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
348 print_safepoint_timeout(_blocking_timeout);
349 }
350 }
351 }
352 assert(_waiting_to_block == 0, "sanity check");
353
354 #ifndef PRODUCT
355 if (SafepointTimeout) {
356 jlong current_time = os::javaTimeNanos();
357 if (safepoint_limit_time < current_time) {
358 tty->print_cr("# SafepointSynchronize: Finished after "
359 INT64_FORMAT_W(6) " ms",
360 ((current_time - safepoint_limit_time) / MICROUNITS +
361 SafepointTimeoutDelay));
362 }
363 }
364 #endif
365
366 assert((_safepoint_counter & 0x1) == 0, "must be even");
367 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
368 _safepoint_counter ++;
369
370 // Record state
371 _state = _synchronized;
372
373 OrderAccess::fence();
374
375 if (TraceSafepoint) {
376 VM_Operation *op = VMThread::vm_operation();
377 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
378 }
379
380 RuntimeService::record_safepoint_synchronized();
381 if (PrintSafepointStatistics) {
382 update_statistics_on_sync_end(os::javaTimeNanos());
383 }
384
385 // Call stuff that needs to be run when a safepoint is just about to be completed
386 do_cleanup_tasks();
387
388 if (PrintSafepointStatistics) {
389 // Record how much time spend on the above cleanup tasks
390 update_statistics_on_cleanup_end(os::javaTimeNanos());
391 }
392 }
393 }
394
395 // Wake up all threads, so they are ready to resume execution after the safepoint
396 // operation has been carried out
397 void SafepointSynchronize::end() {
398
399 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
400 assert((_safepoint_counter & 0x1) == 1, "must be odd");
401 _safepoint_counter ++;
402 // memory fence isn't required here since an odd _safepoint_counter
403 // value can do no harm and a fence is issued below anyway.
404
405 DEBUG_ONLY(Thread* myThread = Thread::current();)
406 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
407
408 if (PrintSafepointStatistics) {
409 end_statistics(os::javaTimeNanos());
410 }
411
412 #ifdef ASSERT
413 // A pending_exception cannot be installed during a safepoint. The threads
414 // may install an async exception after they come back from a safepoint into
415 // pending_exception after they unblock. But that should happen later.
416 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
417 assert (!(cur->has_pending_exception() &&
418 cur->safepoint_state()->is_at_poll_safepoint()),
419 "safepoint installed a pending exception");
420 }
421 #endif // ASSERT
422
423 if (PageArmed) {
424 // Make polling safepoint aware
425 os::make_polling_page_readable();
426 PageArmed = 0 ;
427 }
428
429 // Remove safepoint check from interpreter
430 Interpreter::ignore_safepoints();
431
432 {
433 MutexLocker mu(Safepoint_lock);
434
435 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
436
437 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
438 // when they get restarted.
439 _state = _not_synchronized;
440 OrderAccess::fence();
441
442 if (TraceSafepoint) {
443 tty->print_cr("Leaving safepoint region");
444 }
445
446 // Start suspended threads
447 for(JavaThread *current = Threads::first(); current; current = current->next()) {
448 // A problem occurring on Solaris is when attempting to restart threads
449 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
450 // to the next one (since it has been running the longest). We then have
451 // to wait for a cpu to become available before we can continue restarting
452 // threads.
453 // FIXME: This causes the performance of the VM to degrade when active and with
454 // large numbers of threads. Apparently this is due to the synchronous nature
455 // of suspending threads.
456 //
457 // TODO-FIXME: the comments above are vestigial and no longer apply.
458 // Furthermore, using solaris' schedctl in this particular context confers no benefit
459 if (VMThreadHintNoPreempt) {
460 os::hint_no_preempt();
461 }
462 ThreadSafepointState* cur_state = current->safepoint_state();
463 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
464 cur_state->restart();
465 assert(cur_state->is_running(), "safepoint state has not been reset");
466 }
467
468 RuntimeService::record_safepoint_end();
469
470 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
471 // blocked in signal_thread_blocked
472 Threads_lock->unlock();
473
474 }
475 #ifndef SERIALGC
476 // If there are any concurrent GC threads resume them.
477 if (UseConcMarkSweepGC) {
478 ConcurrentMarkSweepThread::desynchronize(false);
479 } else if (UseG1GC) {
480 ConcurrentGCThread::safepoint_desynchronize();
481 }
482 #endif // SERIALGC
483 // record this time so VMThread can keep track how much time has elasped
484 // since last safepoint.
485 _end_of_last_safepoint = os::javaTimeMillis();
486 }
487
488 bool SafepointSynchronize::is_cleanup_needed() {
489 // Need a safepoint if some inline cache buffers is non-empty
490 if (!InlineCacheBuffer::is_empty()) return true;
491 return false;
492 }
493
494
495
496 // Various cleaning tasks that should be done periodically at safepoints
497 void SafepointSynchronize::do_cleanup_tasks() {
498 {
499 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
500 ObjectSynchronizer::deflate_idle_monitors();
501 }
502
503 {
504 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
505 InlineCacheBuffer::update_inline_caches();
506 }
507 {
508 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
509 CompilationPolicy::policy()->do_safepoint_work();
510 }
511
512 TraceTime t4("sweeping nmethods", TraceSafepointCleanupTime);
513 NMethodSweeper::scan_stacks();
514
515 // rotate log files?
516 if (UseGCLogFileRotation) {
517 gclog_or_tty->rotate_log();
518 }
519 }
520
521
522 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
523 switch(state) {
524 case _thread_in_native:
525 // native threads are safe if they have no java stack or have walkable stack
526 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
527
528 // blocked threads should have already have walkable stack
529 case _thread_blocked:
530 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
531 return true;
532
533 default:
534 return false;
535 }
536 }
537
538
539 // -------------------------------------------------------------------------------------------------------
540 // Implementation of Safepoint callback point
541
542 void SafepointSynchronize::block(JavaThread *thread) {
543 assert(thread != NULL, "thread must be set");
544 assert(thread->is_Java_thread(), "not a Java thread");
545
546 // Threads shouldn't block if they are in the middle of printing, but...
547 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
548
549 // Only bail from the block() call if the thread is gone from the
550 // thread list; starting to exit should still block.
551 if (thread->is_terminated()) {
552 // block current thread if we come here from native code when VM is gone
553 thread->block_if_vm_exited();
554
555 // otherwise do nothing
556 return;
557 }
558
559 JavaThreadState state = thread->thread_state();
560 thread->frame_anchor()->make_walkable(thread);
561
562 // Check that we have a valid thread_state at this point
563 switch(state) {
564 case _thread_in_vm_trans:
565 case _thread_in_Java: // From compiled code
566
567 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
568 // we pretend we are still in the VM.
569 thread->set_thread_state(_thread_in_vm);
570
571 if (is_synchronizing()) {
572 Atomic::inc (&TryingToBlock) ;
573 }
574
575 // We will always be holding the Safepoint_lock when we are examine the state
576 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
577 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
578 Safepoint_lock->lock_without_safepoint_check();
579 if (is_synchronizing()) {
580 // Decrement the number of threads to wait for and signal vm thread
581 assert(_waiting_to_block > 0, "sanity check");
582 _waiting_to_block--;
583 thread->safepoint_state()->set_has_called_back(true);
584
585 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
586 if (_waiting_to_block == 0) {
587 Safepoint_lock->notify_all();
588 }
589 }
590
591 // We transition the thread to state _thread_blocked here, but
592 // we can't do our usual check for external suspension and then
593 // self-suspend after the lock_without_safepoint_check() call
594 // below because we are often called during transitions while
595 // we hold different locks. That would leave us suspended while
596 // holding a resource which results in deadlocks.
597 thread->set_thread_state(_thread_blocked);
598 Safepoint_lock->unlock();
599
600 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
601 // the entire safepoint, the threads will all line up here during the safepoint.
602 Threads_lock->lock_without_safepoint_check();
603 // restore original state. This is important if the thread comes from compiled code, so it
604 // will continue to execute with the _thread_in_Java state.
605 thread->set_thread_state(state);
606 Threads_lock->unlock();
607 break;
608
609 case _thread_in_native_trans:
610 case _thread_blocked_trans:
611 case _thread_new_trans:
612 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
613 thread->print_thread_state();
614 fatal("Deadlock in safepoint code. "
615 "Should have called back to the VM before blocking.");
616 }
617
618 // We transition the thread to state _thread_blocked here, but
619 // we can't do our usual check for external suspension and then
620 // self-suspend after the lock_without_safepoint_check() call
621 // below because we are often called during transitions while
622 // we hold different locks. That would leave us suspended while
623 // holding a resource which results in deadlocks.
624 thread->set_thread_state(_thread_blocked);
625
626 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
627 // the safepoint code might still be waiting for it to block. We need to change the state here,
628 // so it can see that it is at a safepoint.
629
630 // Block until the safepoint operation is completed.
631 Threads_lock->lock_without_safepoint_check();
632
633 // Restore state
634 thread->set_thread_state(state);
635
636 Threads_lock->unlock();
637 break;
638
639 default:
640 fatal(err_msg("Illegal threadstate encountered: %d", state));
641 }
642
643 // Check for pending. async. exceptions or suspends - except if the
644 // thread was blocked inside the VM. has_special_runtime_exit_condition()
645 // is called last since it grabs a lock and we only want to do that when
646 // we must.
647 //
648 // Note: we never deliver an async exception at a polling point as the
649 // compiler may not have an exception handler for it. The polling
650 // code will notice the async and deoptimize and the exception will
651 // be delivered. (Polling at a return point is ok though). Sure is
652 // a lot of bother for a deprecated feature...
653 //
654 // We don't deliver an async exception if the thread state is
655 // _thread_in_native_trans so JNI functions won't be called with
656 // a surprising pending exception. If the thread state is going back to java,
657 // async exception is checked in check_special_condition_for_native_trans().
658
659 if (state != _thread_blocked_trans &&
660 state != _thread_in_vm_trans &&
661 thread->has_special_runtime_exit_condition()) {
662 thread->handle_special_runtime_exit_condition(
663 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
664 }
665 }
666
667 // ------------------------------------------------------------------------------------------------------
668 // Exception handlers
669
670 #ifndef PRODUCT
671 #ifdef _LP64
672 #define PTR_PAD ""
673 #else
674 #define PTR_PAD " "
675 #endif
676
677 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
678 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false;
679 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
680 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
681 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
682 }
683
684 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
685 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false;
686 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
687 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
688 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
689 }
690
691 #ifdef SPARC
692 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
693 #ifdef _LP64
694 tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
695 const int incr = 1; // Increment to skip a long, in units of intptr_t
696 #else
697 tty->print_cr("--------+--address-+------before-----------+-------after----------+");
698 const int incr = 2; // Increment to skip a long, in units of intptr_t
699 #endif
700 tty->print_cr("---SP---|");
701 for( int i=0; i<16; i++ ) {
702 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
703 tty->print_cr("--------|");
704 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
705 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
706 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
707 tty->print_cr("--------|");
708 tty->print(" G1 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
709 tty->print(" G3 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
710 tty->print(" G4 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
711 tty->print(" G5 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr;
712 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
713 old_sp += incr; new_sp += incr; was_oops += incr;
714 // Skip the floats
715 tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
716 tty->print_cr("---FP---|");
717 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32;
718 for( int i2=0; i2<16; i2++ ) {
719 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
720 tty->print_cr("");
721 }
722 #endif // SPARC
723 #endif // PRODUCT
724
725
726 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
727 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
728 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
729 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
730
731 // Uncomment this to get some serious before/after printing of the
732 // Sparc safepoint-blob frame structure.
733 /*
734 intptr_t* sp = thread->last_Java_sp();
735 intptr_t stack_copy[150];
736 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
737 bool was_oops[150];
738 for( int i=0; i<150; i++ )
739 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
740 */
741
742 if (ShowSafepointMsgs) {
743 tty->print("handle_polling_page_exception: ");
744 }
745
746 if (PrintSafepointStatistics) {
747 inc_page_trap_count();
748 }
749
750 ThreadSafepointState* state = thread->safepoint_state();
751
752 state->handle_polling_page_exception();
753 // print_me(sp,stack_copy,was_oops);
754 }
755
756
757 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
758 if (!timeout_error_printed) {
759 timeout_error_printed = true;
760 // Print out the thread infor which didn't reach the safepoint for debugging
761 // purposes (useful when there are lots of threads in the debugger).
762 tty->print_cr("");
763 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
764 if (reason == _spinning_timeout) {
765 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
766 } else if (reason == _blocking_timeout) {
767 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
768 }
769
770 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
771 ThreadSafepointState *cur_state;
772 ResourceMark rm;
773 for(JavaThread *cur_thread = Threads::first(); cur_thread;
774 cur_thread = cur_thread->next()) {
775 cur_state = cur_thread->safepoint_state();
776
777 if (cur_thread->thread_state() != _thread_blocked &&
778 ((reason == _spinning_timeout && cur_state->is_running()) ||
779 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
780 tty->print("# ");
781 cur_thread->print();
782 tty->print_cr("");
783 }
784 }
785 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
786 }
787
788 // To debug the long safepoint, specify both DieOnSafepointTimeout &
789 // ShowMessageBoxOnError.
790 if (DieOnSafepointTimeout) {
791 char msg[1024];
792 VM_Operation *op = VMThread::vm_operation();
793 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
794 SafepointTimeoutDelay,
795 op != NULL ? op->name() : "no vm operation");
796 fatal(msg);
797 }
798 }
799
800
801 // -------------------------------------------------------------------------------------------------------
802 // Implementation of ThreadSafepointState
803
804 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
805 _thread = thread;
806 _type = _running;
807 _has_called_back = false;
808 _at_poll_safepoint = false;
809 }
810
811 void ThreadSafepointState::create(JavaThread *thread) {
812 ThreadSafepointState *state = new ThreadSafepointState(thread);
813 thread->set_safepoint_state(state);
814 }
815
816 void ThreadSafepointState::destroy(JavaThread *thread) {
817 if (thread->safepoint_state()) {
818 delete(thread->safepoint_state());
819 thread->set_safepoint_state(NULL);
820 }
821 }
822
823 void ThreadSafepointState::examine_state_of_thread() {
824 assert(is_running(), "better be running or just have hit safepoint poll");
825
826 JavaThreadState state = _thread->thread_state();
827
828 // Save the state at the start of safepoint processing.
829 _orig_thread_state = state;
830
831 // Check for a thread that is suspended. Note that thread resume tries
832 // to grab the Threads_lock which we own here, so a thread cannot be
833 // resumed during safepoint synchronization.
834
835 // We check to see if this thread is suspended without locking to
836 // avoid deadlocking with a third thread that is waiting for this
837 // thread to be suspended. The third thread can notice the safepoint
838 // that we're trying to start at the beginning of its SR_lock->wait()
839 // call. If that happens, then the third thread will block on the
840 // safepoint while still holding the underlying SR_lock. We won't be
841 // able to get the SR_lock and we'll deadlock.
842 //
843 // We don't need to grab the SR_lock here for two reasons:
844 // 1) The suspend flags are both volatile and are set with an
845 // Atomic::cmpxchg() call so we should see the suspended
846 // state right away.
847 // 2) We're being called from the safepoint polling loop; if
848 // we don't see the suspended state on this iteration, then
849 // we'll come around again.
850 //
851 bool is_suspended = _thread->is_ext_suspended();
852 if (is_suspended) {
853 roll_forward(_at_safepoint);
854 return;
855 }
856
857 // Some JavaThread states have an initial safepoint state of
858 // running, but are actually at a safepoint. We will happily
859 // agree and update the safepoint state here.
860 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
861 roll_forward(_at_safepoint);
862 return;
863 }
864
865 if (state == _thread_in_vm) {
866 roll_forward(_call_back);
867 return;
868 }
869
870 // All other thread states will continue to run until they
871 // transition and self-block in state _blocked
872 // Safepoint polling in compiled code causes the Java threads to do the same.
873 // Note: new threads may require a malloc so they must be allowed to finish
874
875 assert(is_running(), "examine_state_of_thread on non-running thread");
876 return;
877 }
878
879 // Returns true is thread could not be rolled forward at present position.
880 void ThreadSafepointState::roll_forward(suspend_type type) {
881 _type = type;
882
883 switch(_type) {
884 case _at_safepoint:
885 SafepointSynchronize::signal_thread_at_safepoint();
886 break;
887
888 case _call_back:
889 set_has_called_back(false);
890 break;
891
892 case _running:
893 default:
894 ShouldNotReachHere();
895 }
896 }
897
898 void ThreadSafepointState::restart() {
899 switch(type()) {
900 case _at_safepoint:
901 case _call_back:
902 break;
903
904 case _running:
905 default:
906 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
907 _thread, _type);
908 _thread->print();
909 ShouldNotReachHere();
910 }
911 _type = _running;
912 set_has_called_back(false);
913 }
914
915
916 void ThreadSafepointState::print_on(outputStream *st) const {
917 const char *s;
918
919 switch(_type) {
920 case _running : s = "_running"; break;
921 case _at_safepoint : s = "_at_safepoint"; break;
922 case _call_back : s = "_call_back"; break;
923 default:
924 ShouldNotReachHere();
925 }
926
927 st->print_cr("Thread: " INTPTR_FORMAT
928 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
929 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
930 _at_poll_safepoint);
931
932 _thread->print_thread_state_on(st);
933 }
934
935
936 // ---------------------------------------------------------------------------------------------------------------------
937
938 // Block the thread at the safepoint poll or poll return.
939 void ThreadSafepointState::handle_polling_page_exception() {
940
941 // Check state. block() will set thread state to thread_in_vm which will
942 // cause the safepoint state _type to become _call_back.
943 assert(type() == ThreadSafepointState::_running,
944 "polling page exception on thread not running state");
945
946 // Step 1: Find the nmethod from the return address
947 if (ShowSafepointMsgs && Verbose) {
948 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
949 }
950 address real_return_addr = thread()->saved_exception_pc();
951
952 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
953 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
954 nmethod* nm = (nmethod*)cb;
955
956 // Find frame of caller
957 frame stub_fr = thread()->last_frame();
958 CodeBlob* stub_cb = stub_fr.cb();
959 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
960 RegisterMap map(thread(), true);
961 frame caller_fr = stub_fr.sender(&map);
962
963 // Should only be poll_return or poll
964 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
965
966 // This is a poll immediately before a return. The exception handling code
967 // has already had the effect of causing the return to occur, so the execution
968 // will continue immediately after the call. In addition, the oopmap at the
969 // return point does not mark the return value as an oop (if it is), so
970 // it needs a handle here to be updated.
971 if( nm->is_at_poll_return(real_return_addr) ) {
972 // See if return type is an oop.
973 bool return_oop = nm->method()->is_returning_oop();
974 Handle return_value;
975 if (return_oop) {
976 // The oop result has been saved on the stack together with all
977 // the other registers. In order to preserve it over GCs we need
978 // to keep it in a handle.
979 oop result = caller_fr.saved_oop_result(&map);
980 assert(result == NULL || result->is_oop(), "must be oop");
981 return_value = Handle(thread(), result);
982 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
983 }
984
985 // Block the thread
986 SafepointSynchronize::block(thread());
987
988 // restore oop result, if any
989 if (return_oop) {
990 caller_fr.set_saved_oop_result(&map, return_value());
991 }
992 }
993
994 // This is a safepoint poll. Verify the return address and block.
995 else {
996 set_at_poll_safepoint(true);
997
998 // verify the blob built the "return address" correctly
999 assert(real_return_addr == caller_fr.pc(), "must match");
1000
1001 // Block the thread
1002 SafepointSynchronize::block(thread());
1003 set_at_poll_safepoint(false);
1004
1005 // If we have a pending async exception deoptimize the frame
1006 // as otherwise we may never deliver it.
1007 if (thread()->has_async_condition()) {
1008 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1009 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1010 }
1011
1012 // If an exception has been installed we must check for a pending deoptimization
1013 // Deoptimize frame if exception has been thrown.
1014
1015 if (thread()->has_pending_exception() ) {
1016 RegisterMap map(thread(), true);
1017 frame caller_fr = stub_fr.sender(&map);
1018 if (caller_fr.is_deoptimized_frame()) {
1019 // The exception patch will destroy registers that are still
1020 // live and will be needed during deoptimization. Defer the
1021 // Async exception should have defered the exception until the
1022 // next safepoint which will be detected when we get into
1023 // the interpreter so if we have an exception now things
1024 // are messed up.
1025
1026 fatal("Exception installed and deoptimization is pending");
1027 }
1028 }
1029 }
1030 }
1031
1032
1033 //
1034 // Statistics & Instrumentations
1035 //
1036 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1037 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1038 int SafepointSynchronize::_cur_stat_index = 0;
1039 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1040 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1041 jlong SafepointSynchronize::_max_sync_time = 0;
1042 jlong SafepointSynchronize::_max_vmop_time = 0;
1043 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1044
1045 static jlong cleanup_end_time = 0;
1046 static bool need_to_track_page_armed_status = false;
1047 static bool init_done = false;
1048
1049 // Helper method to print the header.
1050 static void print_header() {
1051 tty->print(" vmop "
1052 "[threads: total initially_running wait_to_block] ");
1053 tty->print("[time: spin block sync cleanup vmop] ");
1054
1055 // no page armed status printed out if it is always armed.
1056 if (need_to_track_page_armed_status) {
1057 tty->print("page_armed ");
1058 }
1059
1060 tty->print_cr("page_trap_count");
1061 }
1062
1063 void SafepointSynchronize::deferred_initialize_stat() {
1064 if (init_done) return;
1065
1066 if (PrintSafepointStatisticsCount <= 0) {
1067 fatal("Wrong PrintSafepointStatisticsCount");
1068 }
1069
1070 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1071 // be printed right away, in which case, _safepoint_stats will regress to
1072 // a single element array. Otherwise, it is a circular ring buffer with default
1073 // size of PrintSafepointStatisticsCount.
1074 int stats_array_size;
1075 if (PrintSafepointStatisticsTimeout > 0) {
1076 stats_array_size = 1;
1077 PrintSafepointStatistics = true;
1078 } else {
1079 stats_array_size = PrintSafepointStatisticsCount;
1080 }
1081 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1082 * sizeof(SafepointStats));
1083 guarantee(_safepoint_stats != NULL,
1084 "not enough memory for safepoint instrumentation data");
1085
1086 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1087 need_to_track_page_armed_status = true;
1088 }
1089 init_done = true;
1090 }
1091
1092 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1093 assert(init_done, "safepoint statistics array hasn't been initialized");
1094 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1095
1096 spstat->_time_stamp = _ts_of_current_safepoint;
1097
1098 VM_Operation *op = VMThread::vm_operation();
1099 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1100 if (op != NULL) {
1101 _safepoint_reasons[spstat->_vmop_type]++;
1102 }
1103
1104 spstat->_nof_total_threads = nof_threads;
1105 spstat->_nof_initial_running_threads = nof_running;
1106 spstat->_nof_threads_hit_page_trap = 0;
1107
1108 // Records the start time of spinning. The real time spent on spinning
1109 // will be adjusted when spin is done. Same trick is applied for time
1110 // spent on waiting for threads to block.
1111 if (nof_running != 0) {
1112 spstat->_time_to_spin = os::javaTimeNanos();
1113 } else {
1114 spstat->_time_to_spin = 0;
1115 }
1116 }
1117
1118 void SafepointSynchronize::update_statistics_on_spin_end() {
1119 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1120
1121 jlong cur_time = os::javaTimeNanos();
1122
1123 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1124 if (spstat->_nof_initial_running_threads != 0) {
1125 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1126 }
1127
1128 if (need_to_track_page_armed_status) {
1129 spstat->_page_armed = (PageArmed == 1);
1130 }
1131
1132 // Records the start time of waiting for to block. Updated when block is done.
1133 if (_waiting_to_block != 0) {
1134 spstat->_time_to_wait_to_block = cur_time;
1135 } else {
1136 spstat->_time_to_wait_to_block = 0;
1137 }
1138 }
1139
1140 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1141 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1142
1143 if (spstat->_nof_threads_wait_to_block != 0) {
1144 spstat->_time_to_wait_to_block = end_time -
1145 spstat->_time_to_wait_to_block;
1146 }
1147
1148 // Records the end time of sync which will be used to calculate the total
1149 // vm operation time. Again, the real time spending in syncing will be deducted
1150 // from the start of the sync time later when end_statistics is called.
1151 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1152 if (spstat->_time_to_sync > _max_sync_time) {
1153 _max_sync_time = spstat->_time_to_sync;
1154 }
1155
1156 spstat->_time_to_do_cleanups = end_time;
1157 }
1158
1159 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1160 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1161
1162 // Record how long spent in cleanup tasks.
1163 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1164
1165 cleanup_end_time = end_time;
1166 }
1167
1168 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1169 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1170
1171 // Update the vm operation time.
1172 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1173 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1174 _max_vmop_time = spstat->_time_to_exec_vmop;
1175 }
1176 // Only the sync time longer than the specified
1177 // PrintSafepointStatisticsTimeout will be printed out right away.
1178 // By default, it is -1 meaning all samples will be put into the list.
1179 if ( PrintSafepointStatisticsTimeout > 0) {
1180 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1181 print_statistics();
1182 }
1183 } else {
1184 // The safepoint statistics will be printed out when the _safepoin_stats
1185 // array fills up.
1186 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1187 print_statistics();
1188 _cur_stat_index = 0;
1189 } else {
1190 _cur_stat_index++;
1191 }
1192 }
1193 }
1194
1195 void SafepointSynchronize::print_statistics() {
1196 SafepointStats* sstats = _safepoint_stats;
1197
1198 for (int index = 0; index <= _cur_stat_index; index++) {
1199 if (index % 30 == 0) {
1200 print_header();
1201 }
1202 sstats = &_safepoint_stats[index];
1203 tty->print("%.3f: ", sstats->_time_stamp);
1204 tty->print("%-26s ["
1205 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1206 " ] ",
1207 sstats->_vmop_type == -1 ? "no vm operation" :
1208 VM_Operation::name(sstats->_vmop_type),
1209 sstats->_nof_total_threads,
1210 sstats->_nof_initial_running_threads,
1211 sstats->_nof_threads_wait_to_block);
1212 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1213 tty->print(" ["
1214 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1215 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1216 INT64_FORMAT_W(6)" ] ",
1217 sstats->_time_to_spin / MICROUNITS,
1218 sstats->_time_to_wait_to_block / MICROUNITS,
1219 sstats->_time_to_sync / MICROUNITS,
1220 sstats->_time_to_do_cleanups / MICROUNITS,
1221 sstats->_time_to_exec_vmop / MICROUNITS);
1222
1223 if (need_to_track_page_armed_status) {
1224 tty->print(INT32_FORMAT" ", sstats->_page_armed);
1225 }
1226 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
1227 }
1228 }
1229
1230 // This method will be called when VM exits. It will first call
1231 // print_statistics to print out the rest of the sampling. Then
1232 // it tries to summarize the sampling.
1233 void SafepointSynchronize::print_stat_on_exit() {
1234 if (_safepoint_stats == NULL) return;
1235
1236 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1237
1238 // During VM exit, end_statistics may not get called and in that
1239 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1240 // don't print it out.
1241 // Approximate the vm op time.
1242 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1243 os::javaTimeNanos() - cleanup_end_time;
1244
1245 if ( PrintSafepointStatisticsTimeout < 0 ||
1246 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1247 print_statistics();
1248 }
1249 tty->print_cr("");
1250
1251 // Print out polling page sampling status.
1252 if (!need_to_track_page_armed_status) {
1253 if (UseCompilerSafepoints) {
1254 tty->print_cr("Polling page always armed");
1255 }
1256 } else {
1257 tty->print_cr("Defer polling page loop count = %d\n",
1258 DeferPollingPageLoopCount);
1259 }
1260
1261 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1262 if (_safepoint_reasons[index] != 0) {
1263 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1264 _safepoint_reasons[index]);
1265 }
1266 }
1267
1268 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1269 _coalesced_vmop_count);
1270 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
1271 _max_sync_time / MICROUNITS);
1272 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1273 INT64_FORMAT_W(5)" ms",
1274 _max_vmop_time / MICROUNITS);
1275 }
1276
1277 // ------------------------------------------------------------------------------------------------
1278 // Non-product code
1279
1280 #ifndef PRODUCT
1281
1282 void SafepointSynchronize::print_state() {
1283 if (_state == _not_synchronized) {
1284 tty->print_cr("not synchronized");
1285 } else if (_state == _synchronizing || _state == _synchronized) {
1286 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1287 "synchronized");
1288
1289 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1290 cur->safepoint_state()->print();
1291 }
1292 }
1293 }
1294
1295 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1296 if (ShowSafepointMsgs) {
1297 va_list ap;
1298 va_start(ap, format);
1299 tty->vprint_cr(format, ap);
1300 va_end(ap);
1301 }
1302 }
1303
1304 #endif // !PRODUCT