Thu, 24 May 2018 17:06:56 +0800
Merge
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 */
25 /*
26 * This file has been modified by Loongson Technology in 2015. These
27 * modifications are Copyright (c) 2015 Loongson Technology, and are made
28 * available on the same license terms set forth above.
29 */
31 #include "precompiled.hpp"
32 #include "classfile/symbolTable.hpp"
33 #include "classfile/systemDictionary.hpp"
34 #include "code/codeCache.hpp"
35 #include "code/icBuffer.hpp"
36 #include "code/nmethod.hpp"
37 #include "code/pcDesc.hpp"
38 #include "code/scopeDesc.hpp"
39 #include "gc_interface/collectedHeap.hpp"
40 #include "interpreter/interpreter.hpp"
41 #include "memory/resourceArea.hpp"
42 #include "memory/universe.inline.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "oops/symbol.hpp"
45 #include "runtime/compilationPolicy.hpp"
46 #include "runtime/deoptimization.hpp"
47 #include "runtime/frame.inline.hpp"
48 #include "runtime/interfaceSupport.hpp"
49 #include "runtime/mutexLocker.hpp"
50 #include "runtime/orderAccess.inline.hpp"
51 #include "runtime/osThread.hpp"
52 #include "runtime/safepoint.hpp"
53 #include "runtime/signature.hpp"
54 #include "runtime/stubCodeGenerator.hpp"
55 #include "runtime/stubRoutines.hpp"
56 #include "runtime/sweeper.hpp"
57 #include "runtime/synchronizer.hpp"
58 #include "runtime/thread.inline.hpp"
59 #include "services/runtimeService.hpp"
60 #include "utilities/events.hpp"
61 #include "utilities/macros.hpp"
62 #ifdef TARGET_ARCH_x86
63 # include "nativeInst_x86.hpp"
64 # include "vmreg_x86.inline.hpp"
65 #endif
66 #ifdef TARGET_ARCH_sparc
67 # include "nativeInst_sparc.hpp"
68 # include "vmreg_sparc.inline.hpp"
69 #endif
70 #ifdef TARGET_ARCH_zero
71 # include "nativeInst_zero.hpp"
72 # include "vmreg_zero.inline.hpp"
73 #endif
74 #ifdef TARGET_ARCH_arm
75 # include "nativeInst_arm.hpp"
76 # include "vmreg_arm.inline.hpp"
77 #endif
78 #ifdef TARGET_ARCH_ppc
79 # include "nativeInst_ppc.hpp"
80 # include "vmreg_ppc.inline.hpp"
81 #endif
82 #ifdef TARGET_ARCH_mips
83 # include "nativeInst_mips.hpp"
84 # include "vmreg_mips.inline.hpp"
85 #endif
86 #if INCLUDE_ALL_GCS
87 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
88 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
89 #endif // INCLUDE_ALL_GCS
90 #ifdef COMPILER1
91 #include "c1/c1_globals.hpp"
92 #endif
94 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
96 // --------------------------------------------------------------------------------------------------
97 // Implementation of Safepoint begin/end
99 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
100 volatile int SafepointSynchronize::_waiting_to_block = 0;
101 volatile int SafepointSynchronize::_safepoint_counter = 0;
102 int SafepointSynchronize::_current_jni_active_count = 0;
103 long SafepointSynchronize::_end_of_last_safepoint = 0;
104 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
105 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
106 static bool timeout_error_printed = false;
108 // Roll all threads forward to a safepoint and suspend them all
109 void SafepointSynchronize::begin() {
111 Thread* myThread = Thread::current();
112 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
114 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
115 _safepoint_begin_time = os::javaTimeNanos();
116 _ts_of_current_safepoint = tty->time_stamp().seconds();
117 }
119 #if INCLUDE_ALL_GCS
120 if (UseConcMarkSweepGC) {
121 // In the future we should investigate whether CMS can use the
122 // more-general mechanism below. DLD (01/05).
123 ConcurrentMarkSweepThread::synchronize(false);
124 } else if (UseG1GC) {
125 SuspendibleThreadSet::synchronize();
126 }
127 #endif // INCLUDE_ALL_GCS
129 // By getting the Threads_lock, we assure that no threads are about to start or
130 // exit. It is released again in SafepointSynchronize::end().
131 Threads_lock->lock();
133 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
135 int nof_threads = Threads::number_of_threads();
137 if (TraceSafepoint) {
138 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
139 }
141 RuntimeService::record_safepoint_begin();
143 MutexLocker mu(Safepoint_lock);
145 // Reset the count of active JNI critical threads
146 _current_jni_active_count = 0;
148 // Set number of threads to wait for, before we initiate the callbacks
149 _waiting_to_block = nof_threads;
150 TryingToBlock = 0 ;
151 int still_running = nof_threads;
153 // Save the starting time, so that it can be compared to see if this has taken
154 // too long to complete.
155 jlong safepoint_limit_time = 0;
156 timeout_error_printed = false;
158 // PrintSafepointStatisticsTimeout can be specified separately. When
159 // specified, PrintSafepointStatistics will be set to true in
160 // deferred_initialize_stat method. The initialization has to be done
161 // early enough to avoid any races. See bug 6880029 for details.
162 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
163 deferred_initialize_stat();
164 }
166 // Begin the process of bringing the system to a safepoint.
167 // Java threads can be in several different states and are
168 // stopped by different mechanisms:
169 //
170 // 1. Running interpreted
171 // The interpeter dispatch table is changed to force it to
172 // check for a safepoint condition between bytecodes.
173 // 2. Running in native code
174 // When returning from the native code, a Java thread must check
175 // the safepoint _state to see if we must block. If the
176 // VM thread sees a Java thread in native, it does
177 // not wait for this thread to block. The order of the memory
178 // writes and reads of both the safepoint state and the Java
179 // threads state is critical. In order to guarantee that the
180 // memory writes are serialized with respect to each other,
181 // the VM thread issues a memory barrier instruction
182 // (on MP systems). In order to avoid the overhead of issuing
183 // a memory barrier for each Java thread making native calls, each Java
184 // thread performs a write to a single memory page after changing
185 // the thread state. The VM thread performs a sequence of
186 // mprotect OS calls which forces all previous writes from all
187 // Java threads to be serialized. This is done in the
188 // os::serialize_thread_states() call. This has proven to be
189 // much more efficient than executing a membar instruction
190 // on every call to native code.
191 // 3. Running compiled Code
192 // Compiled code reads a global (Safepoint Polling) page that
193 // is set to fault if we are trying to get to a safepoint.
194 // 4. Blocked
195 // A thread which is blocked will not be allowed to return from the
196 // block condition until the safepoint operation is complete.
197 // 5. In VM or Transitioning between states
198 // If a Java thread is currently running in the VM or transitioning
199 // between states, the safepointing code will wait for the thread to
200 // block itself when it attempts transitions to a new state.
201 //
202 _state = _synchronizing;
203 OrderAccess::fence();
205 // Flush all thread states to memory
206 if (!UseMembar) {
207 os::serialize_thread_states();
208 }
210 // Make interpreter safepoint aware
211 Interpreter::notice_safepoints();
213 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
214 // Make polling safepoint aware
215 guarantee (PageArmed == 0, "invariant") ;
216 PageArmed = 1 ;
217 os::make_polling_page_unreadable();
218 }
220 // Consider using active_processor_count() ... but that call is expensive.
221 int ncpus = os::processor_count() ;
223 #ifdef ASSERT
224 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
225 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
226 // Clear the visited flag to ensure that the critical counts are collected properly.
227 cur->set_visited_for_critical_count(false);
228 }
229 #endif // ASSERT
231 if (SafepointTimeout)
232 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
234 // Iterate through all threads until it have been determined how to stop them all at a safepoint
235 unsigned int iterations = 0;
236 int steps = 0 ;
237 while(still_running > 0) {
238 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
239 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
240 ThreadSafepointState *cur_state = cur->safepoint_state();
241 if (cur_state->is_running()) {
242 cur_state->examine_state_of_thread();
243 if (!cur_state->is_running()) {
244 still_running--;
245 // consider adjusting steps downward:
246 // steps = 0
247 // steps -= NNN
248 // steps >>= 1
249 // steps = MIN(steps, 2000-100)
250 // if (iterations != 0) steps -= NNN
251 }
252 if (TraceSafepoint && Verbose) cur_state->print();
253 }
254 }
256 if (PrintSafepointStatistics && iterations == 0) {
257 begin_statistics(nof_threads, still_running);
258 }
260 if (still_running > 0) {
261 // Check for if it takes to long
262 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
263 print_safepoint_timeout(_spinning_timeout);
264 }
266 // Spin to avoid context switching.
267 // There's a tension between allowing the mutators to run (and rendezvous)
268 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
269 // a mutator might otherwise use profitably to reach a safepoint. Excessive
270 // spinning by the VM thread on a saturated system can increase rendezvous latency.
271 // Blocking or yielding incur their own penalties in the form of context switching
272 // and the resultant loss of $ residency.
273 //
274 // Further complicating matters is that yield() does not work as naively expected
275 // on many platforms -- yield() does not guarantee that any other ready threads
276 // will run. As such we revert yield_all() after some number of iterations.
277 // Yield_all() is implemented as a short unconditional sleep on some platforms.
278 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
279 // can actually increase the time it takes the VM thread to detect that a system-wide
280 // stop-the-world safepoint has been reached. In a pathological scenario such as that
281 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
282 // In that case the mutators will be stalled waiting for the safepoint to complete and the
283 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
284 // will eventually wake up and detect that all mutators are safe, at which point
285 // we'll again make progress.
286 //
287 // Beware too that that the VMThread typically runs at elevated priority.
288 // Its default priority is higher than the default mutator priority.
289 // Obviously, this complicates spinning.
290 //
291 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
292 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
293 //
294 // See the comments in synchronizer.cpp for additional remarks on spinning.
295 //
296 // In the future we might:
297 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
298 // This is tricky as the path used by a thread exiting the JVM (say on
299 // on JNI call-out) simply stores into its state field. The burden
300 // is placed on the VM thread, which must poll (spin).
301 // 2. Find something useful to do while spinning. If the safepoint is GC-related
302 // we might aggressively scan the stacks of threads that are already safe.
303 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
304 // If all the mutators are ONPROC there's no reason to sleep or yield.
305 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
306 // 5. Check system saturation. If the system is not fully saturated then
307 // simply spin and avoid sleep/yield.
308 // 6. As still-running mutators rendezvous they could unpark the sleeping
309 // VMthread. This works well for still-running mutators that become
310 // safe. The VMthread must still poll for mutators that call-out.
311 // 7. Drive the policy on time-since-begin instead of iterations.
312 // 8. Consider making the spin duration a function of the # of CPUs:
313 // Spin = (((ncpus-1) * M) + K) + F(still_running)
314 // Alternately, instead of counting iterations of the outer loop
315 // we could count the # of threads visited in the inner loop, above.
316 // 9. On windows consider using the return value from SwitchThreadTo()
317 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
319 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
320 guarantee (PageArmed == 0, "invariant") ;
321 PageArmed = 1 ;
322 os::make_polling_page_unreadable();
323 }
325 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
326 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
327 ++steps ;
328 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
329 SpinPause() ; // MP-Polite spin
330 } else
331 if (steps < DeferThrSuspendLoopCount) {
332 os::NakedYield() ;
333 } else {
334 os::yield_all(steps) ;
335 // Alternately, the VM thread could transiently depress its scheduling priority or
336 // transiently increase the priority of the tardy mutator(s).
337 }
339 iterations ++ ;
340 }
341 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
342 }
343 assert(still_running == 0, "sanity check");
345 if (PrintSafepointStatistics) {
346 update_statistics_on_spin_end();
347 }
349 // wait until all threads are stopped
350 while (_waiting_to_block > 0) {
351 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
352 if (!SafepointTimeout || timeout_error_printed) {
353 Safepoint_lock->wait(true); // true, means with no safepoint checks
354 } else {
355 // Compute remaining time
356 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
358 // If there is no remaining time, then there is an error
359 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
360 print_safepoint_timeout(_blocking_timeout);
361 }
362 }
363 }
364 assert(_waiting_to_block == 0, "sanity check");
366 #ifndef PRODUCT
367 if (SafepointTimeout) {
368 jlong current_time = os::javaTimeNanos();
369 if (safepoint_limit_time < current_time) {
370 tty->print_cr("# SafepointSynchronize: Finished after "
371 INT64_FORMAT_W(6) " ms",
372 ((current_time - safepoint_limit_time) / MICROUNITS +
373 SafepointTimeoutDelay));
374 }
375 }
376 #endif
378 assert((_safepoint_counter & 0x1) == 0, "must be even");
379 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
380 _safepoint_counter ++;
382 // Record state
383 _state = _synchronized;
385 OrderAccess::fence();
387 #ifdef ASSERT
388 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
389 // make sure all the threads were visited
390 assert(cur->was_visited_for_critical_count(), "missed a thread");
391 }
392 #endif // ASSERT
394 // Update the count of active JNI critical regions
395 GC_locker::set_jni_lock_count(_current_jni_active_count);
397 if (TraceSafepoint) {
398 VM_Operation *op = VMThread::vm_operation();
399 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
400 }
402 RuntimeService::record_safepoint_synchronized();
403 if (PrintSafepointStatistics) {
404 update_statistics_on_sync_end(os::javaTimeNanos());
405 }
407 // Call stuff that needs to be run when a safepoint is just about to be completed
408 do_cleanup_tasks();
410 if (PrintSafepointStatistics) {
411 // Record how much time spend on the above cleanup tasks
412 update_statistics_on_cleanup_end(os::javaTimeNanos());
413 }
414 }
416 // Wake up all threads, so they are ready to resume execution after the safepoint
417 // operation has been carried out
418 void SafepointSynchronize::end() {
420 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
421 assert((_safepoint_counter & 0x1) == 1, "must be odd");
422 _safepoint_counter ++;
423 // memory fence isn't required here since an odd _safepoint_counter
424 // value can do no harm and a fence is issued below anyway.
426 DEBUG_ONLY(Thread* myThread = Thread::current();)
427 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
429 if (PrintSafepointStatistics) {
430 end_statistics(os::javaTimeNanos());
431 }
433 #ifdef ASSERT
434 // A pending_exception cannot be installed during a safepoint. The threads
435 // may install an async exception after they come back from a safepoint into
436 // pending_exception after they unblock. But that should happen later.
437 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
438 assert (!(cur->has_pending_exception() &&
439 cur->safepoint_state()->is_at_poll_safepoint()),
440 "safepoint installed a pending exception");
441 }
442 #endif // ASSERT
444 if (PageArmed) {
445 // Make polling safepoint aware
446 os::make_polling_page_readable();
447 PageArmed = 0 ;
448 }
450 // Remove safepoint check from interpreter
451 Interpreter::ignore_safepoints();
453 {
454 MutexLocker mu(Safepoint_lock);
456 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
458 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
459 // when they get restarted.
460 _state = _not_synchronized;
461 OrderAccess::fence();
463 if (TraceSafepoint) {
464 tty->print_cr("Leaving safepoint region");
465 }
467 // Start suspended threads
468 for(JavaThread *current = Threads::first(); current; current = current->next()) {
469 // A problem occurring on Solaris is when attempting to restart threads
470 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
471 // to the next one (since it has been running the longest). We then have
472 // to wait for a cpu to become available before we can continue restarting
473 // threads.
474 // FIXME: This causes the performance of the VM to degrade when active and with
475 // large numbers of threads. Apparently this is due to the synchronous nature
476 // of suspending threads.
477 //
478 // TODO-FIXME: the comments above are vestigial and no longer apply.
479 // Furthermore, using solaris' schedctl in this particular context confers no benefit
480 if (VMThreadHintNoPreempt) {
481 os::hint_no_preempt();
482 }
483 ThreadSafepointState* cur_state = current->safepoint_state();
484 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
485 cur_state->restart();
486 assert(cur_state->is_running(), "safepoint state has not been reset");
487 }
489 RuntimeService::record_safepoint_end();
491 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
492 // blocked in signal_thread_blocked
493 Threads_lock->unlock();
495 }
496 #if INCLUDE_ALL_GCS
497 // If there are any concurrent GC threads resume them.
498 if (UseConcMarkSweepGC) {
499 ConcurrentMarkSweepThread::desynchronize(false);
500 } else if (UseG1GC) {
501 SuspendibleThreadSet::desynchronize();
502 }
503 #endif // INCLUDE_ALL_GCS
504 // record this time so VMThread can keep track how much time has elasped
505 // since last safepoint.
506 _end_of_last_safepoint = os::javaTimeMillis();
507 }
509 bool SafepointSynchronize::is_cleanup_needed() {
510 // Need a safepoint if some inline cache buffers is non-empty
511 if (!InlineCacheBuffer::is_empty()) return true;
512 return false;
513 }
517 // Various cleaning tasks that should be done periodically at safepoints
518 void SafepointSynchronize::do_cleanup_tasks() {
519 {
520 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
521 ObjectSynchronizer::deflate_idle_monitors();
522 }
524 {
525 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
526 InlineCacheBuffer::update_inline_caches();
527 }
528 {
529 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
530 CompilationPolicy::policy()->do_safepoint_work();
531 }
533 {
534 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
535 NMethodSweeper::mark_active_nmethods();
536 }
538 if (SymbolTable::needs_rehashing()) {
539 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
540 SymbolTable::rehash_table();
541 }
543 if (StringTable::needs_rehashing()) {
544 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
545 StringTable::rehash_table();
546 }
548 // rotate log files?
549 if (UseGCLogFileRotation) {
550 gclog_or_tty->rotate_log(false);
551 }
553 {
554 // CMS delays purging the CLDG until the beginning of the next safepoint and to
555 // make sure concurrent sweep is done
556 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
557 ClassLoaderDataGraph::purge_if_needed();
558 }
559 }
562 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
563 switch(state) {
564 case _thread_in_native:
565 // native threads are safe if they have no java stack or have walkable stack
566 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
568 // blocked threads should have already have walkable stack
569 case _thread_blocked:
570 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
571 return true;
573 default:
574 return false;
575 }
576 }
579 // See if the thread is running inside a lazy critical native and
580 // update the thread critical count if so. Also set a suspend flag to
581 // cause the native wrapper to return into the JVM to do the unlock
582 // once the native finishes.
583 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
584 if (state == _thread_in_native &&
585 thread->has_last_Java_frame() &&
586 thread->frame_anchor()->walkable()) {
587 // This thread might be in a critical native nmethod so look at
588 // the top of the stack and increment the critical count if it
589 // is.
590 frame wrapper_frame = thread->last_frame();
591 CodeBlob* stub_cb = wrapper_frame.cb();
592 if (stub_cb != NULL &&
593 stub_cb->is_nmethod() &&
594 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
595 // A thread could potentially be in a critical native across
596 // more than one safepoint, so only update the critical state on
597 // the first one. When it returns it will perform the unlock.
598 if (!thread->do_critical_native_unlock()) {
599 #ifdef ASSERT
600 if (!thread->in_critical()) {
601 GC_locker::increment_debug_jni_lock_count();
602 }
603 #endif
604 thread->enter_critical();
605 // Make sure the native wrapper calls back on return to
606 // perform the needed critical unlock.
607 thread->set_critical_native_unlock();
608 }
609 }
610 }
611 }
615 // -------------------------------------------------------------------------------------------------------
616 // Implementation of Safepoint callback point
618 void SafepointSynchronize::block(JavaThread *thread) {
619 assert(thread != NULL, "thread must be set");
620 assert(thread->is_Java_thread(), "not a Java thread");
622 // Threads shouldn't block if they are in the middle of printing, but...
623 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
625 // Only bail from the block() call if the thread is gone from the
626 // thread list; starting to exit should still block.
627 if (thread->is_terminated()) {
628 // block current thread if we come here from native code when VM is gone
629 thread->block_if_vm_exited();
631 // otherwise do nothing
632 return;
633 }
635 JavaThreadState state = thread->thread_state();
636 thread->frame_anchor()->make_walkable(thread);
638 // Check that we have a valid thread_state at this point
639 switch(state) {
640 case _thread_in_vm_trans:
641 case _thread_in_Java: // From compiled code
643 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
644 // we pretend we are still in the VM.
645 thread->set_thread_state(_thread_in_vm);
647 if (is_synchronizing()) {
648 Atomic::inc (&TryingToBlock) ;
649 }
651 // We will always be holding the Safepoint_lock when we are examine the state
652 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
653 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
654 Safepoint_lock->lock_without_safepoint_check();
655 if (is_synchronizing()) {
656 // Decrement the number of threads to wait for and signal vm thread
657 assert(_waiting_to_block > 0, "sanity check");
658 _waiting_to_block--;
659 thread->safepoint_state()->set_has_called_back(true);
661 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
662 if (thread->in_critical()) {
663 // Notice that this thread is in a critical section
664 increment_jni_active_count();
665 }
667 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
668 if (_waiting_to_block == 0) {
669 Safepoint_lock->notify_all();
670 }
671 }
673 // We transition the thread to state _thread_blocked here, but
674 // we can't do our usual check for external suspension and then
675 // self-suspend after the lock_without_safepoint_check() call
676 // below because we are often called during transitions while
677 // we hold different locks. That would leave us suspended while
678 // holding a resource which results in deadlocks.
679 thread->set_thread_state(_thread_blocked);
680 Safepoint_lock->unlock();
682 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
683 // the entire safepoint, the threads will all line up here during the safepoint.
684 Threads_lock->lock_without_safepoint_check();
685 // restore original state. This is important if the thread comes from compiled code, so it
686 // will continue to execute with the _thread_in_Java state.
687 thread->set_thread_state(state);
688 Threads_lock->unlock();
689 break;
691 case _thread_in_native_trans:
692 case _thread_blocked_trans:
693 case _thread_new_trans:
694 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
695 thread->print_thread_state();
696 fatal("Deadlock in safepoint code. "
697 "Should have called back to the VM before blocking.");
698 }
700 // We transition the thread to state _thread_blocked here, but
701 // we can't do our usual check for external suspension and then
702 // self-suspend after the lock_without_safepoint_check() call
703 // below because we are often called during transitions while
704 // we hold different locks. That would leave us suspended while
705 // holding a resource which results in deadlocks.
706 thread->set_thread_state(_thread_blocked);
708 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
709 // the safepoint code might still be waiting for it to block. We need to change the state here,
710 // so it can see that it is at a safepoint.
712 // Block until the safepoint operation is completed.
713 Threads_lock->lock_without_safepoint_check();
715 // Restore state
716 thread->set_thread_state(state);
718 Threads_lock->unlock();
719 break;
721 default:
722 fatal(err_msg("Illegal threadstate encountered: %d", state));
723 }
725 // Check for pending. async. exceptions or suspends - except if the
726 // thread was blocked inside the VM. has_special_runtime_exit_condition()
727 // is called last since it grabs a lock and we only want to do that when
728 // we must.
729 //
730 // Note: we never deliver an async exception at a polling point as the
731 // compiler may not have an exception handler for it. The polling
732 // code will notice the async and deoptimize and the exception will
733 // be delivered. (Polling at a return point is ok though). Sure is
734 // a lot of bother for a deprecated feature...
735 //
736 // We don't deliver an async exception if the thread state is
737 // _thread_in_native_trans so JNI functions won't be called with
738 // a surprising pending exception. If the thread state is going back to java,
739 // async exception is checked in check_special_condition_for_native_trans().
741 if (state != _thread_blocked_trans &&
742 state != _thread_in_vm_trans &&
743 thread->has_special_runtime_exit_condition()) {
744 thread->handle_special_runtime_exit_condition(
745 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
746 }
747 }
749 // ------------------------------------------------------------------------------------------------------
750 // Exception handlers
753 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
754 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
755 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
756 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
758 if (ShowSafepointMsgs) {
759 tty->print("handle_polling_page_exception: ");
760 }
762 if (PrintSafepointStatistics) {
763 inc_page_trap_count();
764 }
766 ThreadSafepointState* state = thread->safepoint_state();
768 state->handle_polling_page_exception();
769 }
772 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
773 if (!timeout_error_printed) {
774 timeout_error_printed = true;
775 // Print out the thread infor which didn't reach the safepoint for debugging
776 // purposes (useful when there are lots of threads in the debugger).
777 tty->cr();
778 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
779 if (reason == _spinning_timeout) {
780 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
781 } else if (reason == _blocking_timeout) {
782 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
783 }
785 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
786 ThreadSafepointState *cur_state;
787 ResourceMark rm;
788 for(JavaThread *cur_thread = Threads::first(); cur_thread;
789 cur_thread = cur_thread->next()) {
790 cur_state = cur_thread->safepoint_state();
792 if (cur_thread->thread_state() != _thread_blocked &&
793 ((reason == _spinning_timeout && cur_state->is_running()) ||
794 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
795 tty->print("# ");
796 cur_thread->print();
797 tty->cr();
798 }
799 }
800 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
801 }
803 // To debug the long safepoint, specify both DieOnSafepointTimeout &
804 // ShowMessageBoxOnError.
805 if (DieOnSafepointTimeout) {
806 char msg[1024];
807 VM_Operation *op = VMThread::vm_operation();
808 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
809 SafepointTimeoutDelay,
810 op != NULL ? op->name() : "no vm operation");
811 fatal(msg);
812 }
813 }
816 // -------------------------------------------------------------------------------------------------------
817 // Implementation of ThreadSafepointState
819 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
820 _thread = thread;
821 _type = _running;
822 _has_called_back = false;
823 _at_poll_safepoint = false;
824 }
826 void ThreadSafepointState::create(JavaThread *thread) {
827 ThreadSafepointState *state = new ThreadSafepointState(thread);
828 thread->set_safepoint_state(state);
829 }
831 void ThreadSafepointState::destroy(JavaThread *thread) {
832 if (thread->safepoint_state()) {
833 delete(thread->safepoint_state());
834 thread->set_safepoint_state(NULL);
835 }
836 }
838 void ThreadSafepointState::examine_state_of_thread() {
839 assert(is_running(), "better be running or just have hit safepoint poll");
841 JavaThreadState state = _thread->thread_state();
843 // Save the state at the start of safepoint processing.
844 _orig_thread_state = state;
846 // Check for a thread that is suspended. Note that thread resume tries
847 // to grab the Threads_lock which we own here, so a thread cannot be
848 // resumed during safepoint synchronization.
850 // We check to see if this thread is suspended without locking to
851 // avoid deadlocking with a third thread that is waiting for this
852 // thread to be suspended. The third thread can notice the safepoint
853 // that we're trying to start at the beginning of its SR_lock->wait()
854 // call. If that happens, then the third thread will block on the
855 // safepoint while still holding the underlying SR_lock. We won't be
856 // able to get the SR_lock and we'll deadlock.
857 //
858 // We don't need to grab the SR_lock here for two reasons:
859 // 1) The suspend flags are both volatile and are set with an
860 // Atomic::cmpxchg() call so we should see the suspended
861 // state right away.
862 // 2) We're being called from the safepoint polling loop; if
863 // we don't see the suspended state on this iteration, then
864 // we'll come around again.
865 //
866 bool is_suspended = _thread->is_ext_suspended();
867 if (is_suspended) {
868 roll_forward(_at_safepoint);
869 return;
870 }
872 // Some JavaThread states have an initial safepoint state of
873 // running, but are actually at a safepoint. We will happily
874 // agree and update the safepoint state here.
875 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
876 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
877 roll_forward(_at_safepoint);
878 return;
879 }
881 if (state == _thread_in_vm) {
882 roll_forward(_call_back);
883 return;
884 }
886 // All other thread states will continue to run until they
887 // transition and self-block in state _blocked
888 // Safepoint polling in compiled code causes the Java threads to do the same.
889 // Note: new threads may require a malloc so they must be allowed to finish
891 assert(is_running(), "examine_state_of_thread on non-running thread");
892 return;
893 }
895 // Returns true is thread could not be rolled forward at present position.
896 void ThreadSafepointState::roll_forward(suspend_type type) {
897 _type = type;
899 switch(_type) {
900 case _at_safepoint:
901 SafepointSynchronize::signal_thread_at_safepoint();
902 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
903 if (_thread->in_critical()) {
904 // Notice that this thread is in a critical section
905 SafepointSynchronize::increment_jni_active_count();
906 }
907 break;
909 case _call_back:
910 set_has_called_back(false);
911 break;
913 case _running:
914 default:
915 ShouldNotReachHere();
916 }
917 }
919 void ThreadSafepointState::restart() {
920 switch(type()) {
921 case _at_safepoint:
922 case _call_back:
923 break;
925 case _running:
926 default:
927 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
928 _thread, _type);
929 _thread->print();
930 ShouldNotReachHere();
931 }
932 _type = _running;
933 set_has_called_back(false);
934 }
937 void ThreadSafepointState::print_on(outputStream *st) const {
938 const char *s = NULL;
940 switch(_type) {
941 case _running : s = "_running"; break;
942 case _at_safepoint : s = "_at_safepoint"; break;
943 case _call_back : s = "_call_back"; break;
944 default:
945 ShouldNotReachHere();
946 }
948 st->print_cr("Thread: " INTPTR_FORMAT
949 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
950 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
951 _at_poll_safepoint);
953 _thread->print_thread_state_on(st);
954 }
957 // ---------------------------------------------------------------------------------------------------------------------
959 // Block the thread at the safepoint poll or poll return.
960 void ThreadSafepointState::handle_polling_page_exception() {
962 // Check state. block() will set thread state to thread_in_vm which will
963 // cause the safepoint state _type to become _call_back.
964 assert(type() == ThreadSafepointState::_running,
965 "polling page exception on thread not running state");
967 // Step 1: Find the nmethod from the return address
968 if (ShowSafepointMsgs && Verbose) {
969 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
970 }
971 address real_return_addr = thread()->saved_exception_pc();
973 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
974 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
975 nmethod* nm = (nmethod*)cb;
977 // Find frame of caller
978 frame stub_fr = thread()->last_frame();
979 CodeBlob* stub_cb = stub_fr.cb();
980 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
981 RegisterMap map(thread(), true);
982 frame caller_fr = stub_fr.sender(&map);
984 // Should only be poll_return or poll
985 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
987 // This is a poll immediately before a return. The exception handling code
988 // has already had the effect of causing the return to occur, so the execution
989 // will continue immediately after the call. In addition, the oopmap at the
990 // return point does not mark the return value as an oop (if it is), so
991 // it needs a handle here to be updated.
992 if( nm->is_at_poll_return(real_return_addr) ) {
993 // See if return type is an oop.
994 bool return_oop = nm->method()->is_returning_oop();
995 Handle return_value;
996 if (return_oop) {
997 // The oop result has been saved on the stack together with all
998 // the other registers. In order to preserve it over GCs we need
999 // to keep it in a handle.
1000 oop result = caller_fr.saved_oop_result(&map);
1001 assert(result == NULL || result->is_oop(), "must be oop");
1002 return_value = Handle(thread(), result);
1003 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1004 }
1006 // Block the thread
1007 SafepointSynchronize::block(thread());
1009 // restore oop result, if any
1010 if (return_oop) {
1011 caller_fr.set_saved_oop_result(&map, return_value());
1012 }
1013 }
1015 // This is a safepoint poll. Verify the return address and block.
1016 else {
1017 set_at_poll_safepoint(true);
1019 // verify the blob built the "return address" correctly
1020 assert(real_return_addr == caller_fr.pc(), "must match");
1022 // Block the thread
1023 SafepointSynchronize::block(thread());
1024 set_at_poll_safepoint(false);
1026 // If we have a pending async exception deoptimize the frame
1027 // as otherwise we may never deliver it.
1028 if (thread()->has_async_condition()) {
1029 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1030 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1031 }
1033 // If an exception has been installed we must check for a pending deoptimization
1034 // Deoptimize frame if exception has been thrown.
1036 if (thread()->has_pending_exception() ) {
1037 RegisterMap map(thread(), true);
1038 frame caller_fr = stub_fr.sender(&map);
1039 if (caller_fr.is_deoptimized_frame()) {
1040 // The exception patch will destroy registers that are still
1041 // live and will be needed during deoptimization. Defer the
1042 // Async exception should have defered the exception until the
1043 // next safepoint which will be detected when we get into
1044 // the interpreter so if we have an exception now things
1045 // are messed up.
1047 fatal("Exception installed and deoptimization is pending");
1048 }
1049 }
1050 }
1051 }
1054 //
1055 // Statistics & Instrumentations
1056 //
1057 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1058 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1059 int SafepointSynchronize::_cur_stat_index = 0;
1060 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1061 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1062 jlong SafepointSynchronize::_max_sync_time = 0;
1063 jlong SafepointSynchronize::_max_vmop_time = 0;
1064 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1066 static jlong cleanup_end_time = 0;
1067 static bool need_to_track_page_armed_status = false;
1068 static bool init_done = false;
1070 // Helper method to print the header.
1071 static void print_header() {
1072 tty->print(" vmop "
1073 "[threads: total initially_running wait_to_block] ");
1074 tty->print("[time: spin block sync cleanup vmop] ");
1076 // no page armed status printed out if it is always armed.
1077 if (need_to_track_page_armed_status) {
1078 tty->print("page_armed ");
1079 }
1081 tty->print_cr("page_trap_count");
1082 }
1084 void SafepointSynchronize::deferred_initialize_stat() {
1085 if (init_done) return;
1087 if (PrintSafepointStatisticsCount <= 0) {
1088 fatal("Wrong PrintSafepointStatisticsCount");
1089 }
1091 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1092 // be printed right away, in which case, _safepoint_stats will regress to
1093 // a single element array. Otherwise, it is a circular ring buffer with default
1094 // size of PrintSafepointStatisticsCount.
1095 int stats_array_size;
1096 if (PrintSafepointStatisticsTimeout > 0) {
1097 stats_array_size = 1;
1098 PrintSafepointStatistics = true;
1099 } else {
1100 stats_array_size = PrintSafepointStatisticsCount;
1101 }
1102 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1103 * sizeof(SafepointStats), mtInternal);
1104 guarantee(_safepoint_stats != NULL,
1105 "not enough memory for safepoint instrumentation data");
1107 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1108 need_to_track_page_armed_status = true;
1109 }
1110 init_done = true;
1111 }
1113 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1114 assert(init_done, "safepoint statistics array hasn't been initialized");
1115 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1117 spstat->_time_stamp = _ts_of_current_safepoint;
1119 VM_Operation *op = VMThread::vm_operation();
1120 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1121 if (op != NULL) {
1122 _safepoint_reasons[spstat->_vmop_type]++;
1123 }
1125 spstat->_nof_total_threads = nof_threads;
1126 spstat->_nof_initial_running_threads = nof_running;
1127 spstat->_nof_threads_hit_page_trap = 0;
1129 // Records the start time of spinning. The real time spent on spinning
1130 // will be adjusted when spin is done. Same trick is applied for time
1131 // spent on waiting for threads to block.
1132 if (nof_running != 0) {
1133 spstat->_time_to_spin = os::javaTimeNanos();
1134 } else {
1135 spstat->_time_to_spin = 0;
1136 }
1137 }
1139 void SafepointSynchronize::update_statistics_on_spin_end() {
1140 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1142 jlong cur_time = os::javaTimeNanos();
1144 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1145 if (spstat->_nof_initial_running_threads != 0) {
1146 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1147 }
1149 if (need_to_track_page_armed_status) {
1150 spstat->_page_armed = (PageArmed == 1);
1151 }
1153 // Records the start time of waiting for to block. Updated when block is done.
1154 if (_waiting_to_block != 0) {
1155 spstat->_time_to_wait_to_block = cur_time;
1156 } else {
1157 spstat->_time_to_wait_to_block = 0;
1158 }
1159 }
1161 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1162 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1164 if (spstat->_nof_threads_wait_to_block != 0) {
1165 spstat->_time_to_wait_to_block = end_time -
1166 spstat->_time_to_wait_to_block;
1167 }
1169 // Records the end time of sync which will be used to calculate the total
1170 // vm operation time. Again, the real time spending in syncing will be deducted
1171 // from the start of the sync time later when end_statistics is called.
1172 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1173 if (spstat->_time_to_sync > _max_sync_time) {
1174 _max_sync_time = spstat->_time_to_sync;
1175 }
1177 spstat->_time_to_do_cleanups = end_time;
1178 }
1180 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1181 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1183 // Record how long spent in cleanup tasks.
1184 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1186 cleanup_end_time = end_time;
1187 }
1189 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1190 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1192 // Update the vm operation time.
1193 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1194 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1195 _max_vmop_time = spstat->_time_to_exec_vmop;
1196 }
1197 // Only the sync time longer than the specified
1198 // PrintSafepointStatisticsTimeout will be printed out right away.
1199 // By default, it is -1 meaning all samples will be put into the list.
1200 if ( PrintSafepointStatisticsTimeout > 0) {
1201 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1202 print_statistics();
1203 }
1204 } else {
1205 // The safepoint statistics will be printed out when the _safepoin_stats
1206 // array fills up.
1207 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1208 print_statistics();
1209 _cur_stat_index = 0;
1210 } else {
1211 _cur_stat_index++;
1212 }
1213 }
1214 }
1216 void SafepointSynchronize::print_statistics() {
1217 SafepointStats* sstats = _safepoint_stats;
1219 for (int index = 0; index <= _cur_stat_index; index++) {
1220 if (index % 30 == 0) {
1221 print_header();
1222 }
1223 sstats = &_safepoint_stats[index];
1224 tty->print("%.3f: ", sstats->_time_stamp);
1225 tty->print("%-26s ["
1226 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1227 " ] ",
1228 sstats->_vmop_type == -1 ? "no vm operation" :
1229 VM_Operation::name(sstats->_vmop_type),
1230 sstats->_nof_total_threads,
1231 sstats->_nof_initial_running_threads,
1232 sstats->_nof_threads_wait_to_block);
1233 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1234 tty->print(" ["
1235 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1236 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1237 INT64_FORMAT_W(6)" ] ",
1238 sstats->_time_to_spin / MICROUNITS,
1239 sstats->_time_to_wait_to_block / MICROUNITS,
1240 sstats->_time_to_sync / MICROUNITS,
1241 sstats->_time_to_do_cleanups / MICROUNITS,
1242 sstats->_time_to_exec_vmop / MICROUNITS);
1244 if (need_to_track_page_armed_status) {
1245 tty->print(INT32_FORMAT" ", sstats->_page_armed);
1246 }
1247 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
1248 }
1249 }
1251 // This method will be called when VM exits. It will first call
1252 // print_statistics to print out the rest of the sampling. Then
1253 // it tries to summarize the sampling.
1254 void SafepointSynchronize::print_stat_on_exit() {
1255 if (_safepoint_stats == NULL) return;
1257 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1259 // During VM exit, end_statistics may not get called and in that
1260 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1261 // don't print it out.
1262 // Approximate the vm op time.
1263 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1264 os::javaTimeNanos() - cleanup_end_time;
1266 if ( PrintSafepointStatisticsTimeout < 0 ||
1267 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1268 print_statistics();
1269 }
1270 tty->cr();
1272 // Print out polling page sampling status.
1273 if (!need_to_track_page_armed_status) {
1274 if (UseCompilerSafepoints) {
1275 tty->print_cr("Polling page always armed");
1276 }
1277 } else {
1278 tty->print_cr("Defer polling page loop count = %d\n",
1279 DeferPollingPageLoopCount);
1280 }
1282 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1283 if (_safepoint_reasons[index] != 0) {
1284 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1285 _safepoint_reasons[index]);
1286 }
1287 }
1289 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1290 _coalesced_vmop_count);
1291 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
1292 _max_sync_time / MICROUNITS);
1293 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1294 INT64_FORMAT_W(5)" ms",
1295 _max_vmop_time / MICROUNITS);
1296 }
1298 // ------------------------------------------------------------------------------------------------
1299 // Non-product code
1301 #ifndef PRODUCT
1303 void SafepointSynchronize::print_state() {
1304 if (_state == _not_synchronized) {
1305 tty->print_cr("not synchronized");
1306 } else if (_state == _synchronizing || _state == _synchronized) {
1307 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1308 "synchronized");
1310 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1311 cur->safepoint_state()->print();
1312 }
1313 }
1314 }
1316 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1317 if (ShowSafepointMsgs) {
1318 va_list ap;
1319 va_start(ap, format);
1320 tty->vprint_cr(format, ap);
1321 va_end(ap);
1322 }
1323 }
1325 #endif // !PRODUCT