Wed, 16 Jan 2013 16:30:04 +0100
8006403: Regression: jstack failed due to the FieldInfo regression in SA
Reviewed-by: sla, dholmes
Contributed-by: Aleksey Shipilev <aleksey.shipilev@oracle.com>
1 /*
2 * Copyright (c) 1997, 2012, 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 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "code/icBuffer.hpp"
30 #include "code/nmethod.hpp"
31 #include "code/pcDesc.hpp"
32 #include "code/scopeDesc.hpp"
33 #include "gc_interface/collectedHeap.hpp"
34 #include "interpreter/interpreter.hpp"
35 #include "memory/resourceArea.hpp"
36 #include "memory/universe.inline.hpp"
37 #include "oops/oop.inline.hpp"
38 #include "oops/symbol.hpp"
39 #include "runtime/compilationPolicy.hpp"
40 #include "runtime/deoptimization.hpp"
41 #include "runtime/frame.inline.hpp"
42 #include "runtime/interfaceSupport.hpp"
43 #include "runtime/mutexLocker.hpp"
44 #include "runtime/osThread.hpp"
45 #include "runtime/safepoint.hpp"
46 #include "runtime/signature.hpp"
47 #include "runtime/stubCodeGenerator.hpp"
48 #include "runtime/stubRoutines.hpp"
49 #include "runtime/sweeper.hpp"
50 #include "runtime/synchronizer.hpp"
51 #include "runtime/thread.inline.hpp"
52 #include "services/memTracker.hpp"
53 #include "services/runtimeService.hpp"
54 #include "utilities/events.hpp"
55 #ifdef TARGET_ARCH_x86
56 # include "nativeInst_x86.hpp"
57 # include "vmreg_x86.inline.hpp"
58 #endif
59 #ifdef TARGET_ARCH_sparc
60 # include "nativeInst_sparc.hpp"
61 # include "vmreg_sparc.inline.hpp"
62 #endif
63 #ifdef TARGET_ARCH_zero
64 # include "nativeInst_zero.hpp"
65 # include "vmreg_zero.inline.hpp"
66 #endif
67 #ifdef TARGET_ARCH_arm
68 # include "nativeInst_arm.hpp"
69 # include "vmreg_arm.inline.hpp"
70 #endif
71 #ifdef TARGET_ARCH_ppc
72 # include "nativeInst_ppc.hpp"
73 # include "vmreg_ppc.inline.hpp"
74 #endif
75 #ifndef SERIALGC
76 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
77 #include "gc_implementation/shared/concurrentGCThread.hpp"
78 #endif
79 #ifdef COMPILER1
80 #include "c1/c1_globals.hpp"
81 #endif
83 // --------------------------------------------------------------------------------------------------
84 // Implementation of Safepoint begin/end
86 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
87 volatile int SafepointSynchronize::_waiting_to_block = 0;
88 volatile int SafepointSynchronize::_safepoint_counter = 0;
89 int SafepointSynchronize::_current_jni_active_count = 0;
90 long SafepointSynchronize::_end_of_last_safepoint = 0;
91 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
92 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
93 static bool timeout_error_printed = false;
95 // Roll all threads forward to a safepoint and suspend them all
96 void SafepointSynchronize::begin() {
98 Thread* myThread = Thread::current();
99 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
101 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
102 _safepoint_begin_time = os::javaTimeNanos();
103 _ts_of_current_safepoint = tty->time_stamp().seconds();
104 }
106 #ifndef SERIALGC
107 if (UseConcMarkSweepGC) {
108 // In the future we should investigate whether CMS can use the
109 // more-general mechanism below. DLD (01/05).
110 ConcurrentMarkSweepThread::synchronize(false);
111 } else if (UseG1GC) {
112 ConcurrentGCThread::safepoint_synchronize();
113 }
114 #endif // SERIALGC
116 // By getting the Threads_lock, we assure that no threads are about to start or
117 // exit. It is released again in SafepointSynchronize::end().
118 Threads_lock->lock();
120 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
122 int nof_threads = Threads::number_of_threads();
124 if (TraceSafepoint) {
125 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
126 }
128 RuntimeService::record_safepoint_begin();
130 MutexLocker mu(Safepoint_lock);
132 // Reset the count of active JNI critical threads
133 _current_jni_active_count = 0;
135 // Set number of threads to wait for, before we initiate the callbacks
136 _waiting_to_block = nof_threads;
137 TryingToBlock = 0 ;
138 int still_running = nof_threads;
140 // Save the starting time, so that it can be compared to see if this has taken
141 // too long to complete.
142 jlong safepoint_limit_time;
143 timeout_error_printed = false;
145 // PrintSafepointStatisticsTimeout can be specified separately. When
146 // specified, PrintSafepointStatistics will be set to true in
147 // deferred_initialize_stat method. The initialization has to be done
148 // early enough to avoid any races. See bug 6880029 for details.
149 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
150 deferred_initialize_stat();
151 }
153 // Begin the process of bringing the system to a safepoint.
154 // Java threads can be in several different states and are
155 // stopped by different mechanisms:
156 //
157 // 1. Running interpreted
158 // The interpeter dispatch table is changed to force it to
159 // check for a safepoint condition between bytecodes.
160 // 2. Running in native code
161 // When returning from the native code, a Java thread must check
162 // the safepoint _state to see if we must block. If the
163 // VM thread sees a Java thread in native, it does
164 // not wait for this thread to block. The order of the memory
165 // writes and reads of both the safepoint state and the Java
166 // threads state is critical. In order to guarantee that the
167 // memory writes are serialized with respect to each other,
168 // the VM thread issues a memory barrier instruction
169 // (on MP systems). In order to avoid the overhead of issuing
170 // a memory barrier for each Java thread making native calls, each Java
171 // thread performs a write to a single memory page after changing
172 // the thread state. The VM thread performs a sequence of
173 // mprotect OS calls which forces all previous writes from all
174 // Java threads to be serialized. This is done in the
175 // os::serialize_thread_states() call. This has proven to be
176 // much more efficient than executing a membar instruction
177 // on every call to native code.
178 // 3. Running compiled Code
179 // Compiled code reads a global (Safepoint Polling) page that
180 // is set to fault if we are trying to get to a safepoint.
181 // 4. Blocked
182 // A thread which is blocked will not be allowed to return from the
183 // block condition until the safepoint operation is complete.
184 // 5. In VM or Transitioning between states
185 // If a Java thread is currently running in the VM or transitioning
186 // between states, the safepointing code will wait for the thread to
187 // block itself when it attempts transitions to a new state.
188 //
189 _state = _synchronizing;
190 OrderAccess::fence();
192 // Flush all thread states to memory
193 if (!UseMembar) {
194 os::serialize_thread_states();
195 }
197 // Make interpreter safepoint aware
198 Interpreter::notice_safepoints();
200 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
201 // Make polling safepoint aware
202 guarantee (PageArmed == 0, "invariant") ;
203 PageArmed = 1 ;
204 os::make_polling_page_unreadable();
205 }
207 // Consider using active_processor_count() ... but that call is expensive.
208 int ncpus = os::processor_count() ;
210 #ifdef ASSERT
211 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
212 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
213 // Clear the visited flag to ensure that the critical counts are collected properly.
214 cur->set_visited_for_critical_count(false);
215 }
216 #endif // ASSERT
218 if (SafepointTimeout)
219 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
221 // Iterate through all threads until it have been determined how to stop them all at a safepoint
222 unsigned int iterations = 0;
223 int steps = 0 ;
224 while(still_running > 0) {
225 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
226 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
227 ThreadSafepointState *cur_state = cur->safepoint_state();
228 if (cur_state->is_running()) {
229 cur_state->examine_state_of_thread();
230 if (!cur_state->is_running()) {
231 still_running--;
232 // consider adjusting steps downward:
233 // steps = 0
234 // steps -= NNN
235 // steps >>= 1
236 // steps = MIN(steps, 2000-100)
237 // if (iterations != 0) steps -= NNN
238 }
239 if (TraceSafepoint && Verbose) cur_state->print();
240 }
241 }
243 if (PrintSafepointStatistics && iterations == 0) {
244 begin_statistics(nof_threads, still_running);
245 }
247 if (still_running > 0) {
248 // Check for if it takes to long
249 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
250 print_safepoint_timeout(_spinning_timeout);
251 }
253 // Spin to avoid context switching.
254 // There's a tension between allowing the mutators to run (and rendezvous)
255 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
256 // a mutator might otherwise use profitably to reach a safepoint. Excessive
257 // spinning by the VM thread on a saturated system can increase rendezvous latency.
258 // Blocking or yielding incur their own penalties in the form of context switching
259 // and the resultant loss of $ residency.
260 //
261 // Further complicating matters is that yield() does not work as naively expected
262 // on many platforms -- yield() does not guarantee that any other ready threads
263 // will run. As such we revert yield_all() after some number of iterations.
264 // Yield_all() is implemented as a short unconditional sleep on some platforms.
265 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
266 // can actually increase the time it takes the VM thread to detect that a system-wide
267 // stop-the-world safepoint has been reached. In a pathological scenario such as that
268 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
269 // In that case the mutators will be stalled waiting for the safepoint to complete and the
270 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
271 // will eventually wake up and detect that all mutators are safe, at which point
272 // we'll again make progress.
273 //
274 // Beware too that that the VMThread typically runs at elevated priority.
275 // Its default priority is higher than the default mutator priority.
276 // Obviously, this complicates spinning.
277 //
278 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
279 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
280 //
281 // See the comments in synchronizer.cpp for additional remarks on spinning.
282 //
283 // In the future we might:
284 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
285 // This is tricky as the path used by a thread exiting the JVM (say on
286 // on JNI call-out) simply stores into its state field. The burden
287 // is placed on the VM thread, which must poll (spin).
288 // 2. Find something useful to do while spinning. If the safepoint is GC-related
289 // we might aggressively scan the stacks of threads that are already safe.
290 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
291 // If all the mutators are ONPROC there's no reason to sleep or yield.
292 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
293 // 5. Check system saturation. If the system is not fully saturated then
294 // simply spin and avoid sleep/yield.
295 // 6. As still-running mutators rendezvous they could unpark the sleeping
296 // VMthread. This works well for still-running mutators that become
297 // safe. The VMthread must still poll for mutators that call-out.
298 // 7. Drive the policy on time-since-begin instead of iterations.
299 // 8. Consider making the spin duration a function of the # of CPUs:
300 // Spin = (((ncpus-1) * M) + K) + F(still_running)
301 // Alternately, instead of counting iterations of the outer loop
302 // we could count the # of threads visited in the inner loop, above.
303 // 9. On windows consider using the return value from SwitchThreadTo()
304 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
306 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
307 guarantee (PageArmed == 0, "invariant") ;
308 PageArmed = 1 ;
309 os::make_polling_page_unreadable();
310 }
312 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
313 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
314 ++steps ;
315 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
316 SpinPause() ; // MP-Polite spin
317 } else
318 if (steps < DeferThrSuspendLoopCount) {
319 os::NakedYield() ;
320 } else {
321 os::yield_all(steps) ;
322 // Alternately, the VM thread could transiently depress its scheduling priority or
323 // transiently increase the priority of the tardy mutator(s).
324 }
326 iterations ++ ;
327 }
328 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
329 }
330 assert(still_running == 0, "sanity check");
332 if (PrintSafepointStatistics) {
333 update_statistics_on_spin_end();
334 }
336 // wait until all threads are stopped
337 while (_waiting_to_block > 0) {
338 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
339 if (!SafepointTimeout || timeout_error_printed) {
340 Safepoint_lock->wait(true); // true, means with no safepoint checks
341 } else {
342 // Compute remaining time
343 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
345 // If there is no remaining time, then there is an error
346 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
347 print_safepoint_timeout(_blocking_timeout);
348 }
349 }
350 }
351 assert(_waiting_to_block == 0, "sanity check");
353 #ifndef PRODUCT
354 if (SafepointTimeout) {
355 jlong current_time = os::javaTimeNanos();
356 if (safepoint_limit_time < current_time) {
357 tty->print_cr("# SafepointSynchronize: Finished after "
358 INT64_FORMAT_W(6) " ms",
359 ((current_time - safepoint_limit_time) / MICROUNITS +
360 SafepointTimeoutDelay));
361 }
362 }
363 #endif
365 assert((_safepoint_counter & 0x1) == 0, "must be even");
366 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
367 _safepoint_counter ++;
369 // Record state
370 _state = _synchronized;
372 OrderAccess::fence();
374 #ifdef ASSERT
375 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
376 // make sure all the threads were visited
377 assert(cur->was_visited_for_critical_count(), "missed a thread");
378 }
379 #endif // ASSERT
381 // Update the count of active JNI critical regions
382 GC_locker::set_jni_lock_count(_current_jni_active_count);
384 if (TraceSafepoint) {
385 VM_Operation *op = VMThread::vm_operation();
386 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
387 }
389 RuntimeService::record_safepoint_synchronized();
390 if (PrintSafepointStatistics) {
391 update_statistics_on_sync_end(os::javaTimeNanos());
392 }
394 // Call stuff that needs to be run when a safepoint is just about to be completed
395 do_cleanup_tasks();
397 if (PrintSafepointStatistics) {
398 // Record how much time spend on the above cleanup tasks
399 update_statistics_on_cleanup_end(os::javaTimeNanos());
400 }
401 }
403 // Wake up all threads, so they are ready to resume execution after the safepoint
404 // operation has been carried out
405 void SafepointSynchronize::end() {
407 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
408 assert((_safepoint_counter & 0x1) == 1, "must be odd");
409 _safepoint_counter ++;
410 // memory fence isn't required here since an odd _safepoint_counter
411 // value can do no harm and a fence is issued below anyway.
413 DEBUG_ONLY(Thread* myThread = Thread::current();)
414 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
416 if (PrintSafepointStatistics) {
417 end_statistics(os::javaTimeNanos());
418 }
420 #ifdef ASSERT
421 // A pending_exception cannot be installed during a safepoint. The threads
422 // may install an async exception after they come back from a safepoint into
423 // pending_exception after they unblock. But that should happen later.
424 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
425 assert (!(cur->has_pending_exception() &&
426 cur->safepoint_state()->is_at_poll_safepoint()),
427 "safepoint installed a pending exception");
428 }
429 #endif // ASSERT
431 if (PageArmed) {
432 // Make polling safepoint aware
433 os::make_polling_page_readable();
434 PageArmed = 0 ;
435 }
437 // Remove safepoint check from interpreter
438 Interpreter::ignore_safepoints();
440 {
441 MutexLocker mu(Safepoint_lock);
443 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
445 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
446 // when they get restarted.
447 _state = _not_synchronized;
448 OrderAccess::fence();
450 if (TraceSafepoint) {
451 tty->print_cr("Leaving safepoint region");
452 }
454 // Start suspended threads
455 for(JavaThread *current = Threads::first(); current; current = current->next()) {
456 // A problem occurring on Solaris is when attempting to restart threads
457 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
458 // to the next one (since it has been running the longest). We then have
459 // to wait for a cpu to become available before we can continue restarting
460 // threads.
461 // FIXME: This causes the performance of the VM to degrade when active and with
462 // large numbers of threads. Apparently this is due to the synchronous nature
463 // of suspending threads.
464 //
465 // TODO-FIXME: the comments above are vestigial and no longer apply.
466 // Furthermore, using solaris' schedctl in this particular context confers no benefit
467 if (VMThreadHintNoPreempt) {
468 os::hint_no_preempt();
469 }
470 ThreadSafepointState* cur_state = current->safepoint_state();
471 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
472 cur_state->restart();
473 assert(cur_state->is_running(), "safepoint state has not been reset");
474 }
476 RuntimeService::record_safepoint_end();
478 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
479 // blocked in signal_thread_blocked
480 Threads_lock->unlock();
482 }
483 #ifndef SERIALGC
484 // If there are any concurrent GC threads resume them.
485 if (UseConcMarkSweepGC) {
486 ConcurrentMarkSweepThread::desynchronize(false);
487 } else if (UseG1GC) {
488 ConcurrentGCThread::safepoint_desynchronize();
489 }
490 #endif // SERIALGC
491 // record this time so VMThread can keep track how much time has elasped
492 // since last safepoint.
493 _end_of_last_safepoint = os::javaTimeMillis();
494 }
496 bool SafepointSynchronize::is_cleanup_needed() {
497 // Need a safepoint if some inline cache buffers is non-empty
498 if (!InlineCacheBuffer::is_empty()) return true;
499 return false;
500 }
504 // Various cleaning tasks that should be done periodically at safepoints
505 void SafepointSynchronize::do_cleanup_tasks() {
506 {
507 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
508 ObjectSynchronizer::deflate_idle_monitors();
509 }
511 {
512 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
513 InlineCacheBuffer::update_inline_caches();
514 }
515 {
516 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
517 CompilationPolicy::policy()->do_safepoint_work();
518 }
520 {
521 TraceTime t4("sweeping nmethods", TraceSafepointCleanupTime);
522 NMethodSweeper::scan_stacks();
523 }
525 if (SymbolTable::needs_rehashing()) {
526 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
527 SymbolTable::rehash_table();
528 }
530 if (StringTable::needs_rehashing()) {
531 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
532 StringTable::rehash_table();
533 }
535 // rotate log files?
536 if (UseGCLogFileRotation) {
537 gclog_or_tty->rotate_log();
538 }
540 if (MemTracker::is_on()) {
541 MemTracker::sync();
542 }
543 }
546 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
547 switch(state) {
548 case _thread_in_native:
549 // native threads are safe if they have no java stack or have walkable stack
550 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
552 // blocked threads should have already have walkable stack
553 case _thread_blocked:
554 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
555 return true;
557 default:
558 return false;
559 }
560 }
563 // See if the thread is running inside a lazy critical native and
564 // update the thread critical count if so. Also set a suspend flag to
565 // cause the native wrapper to return into the JVM to do the unlock
566 // once the native finishes.
567 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
568 if (state == _thread_in_native &&
569 thread->has_last_Java_frame() &&
570 thread->frame_anchor()->walkable()) {
571 // This thread might be in a critical native nmethod so look at
572 // the top of the stack and increment the critical count if it
573 // is.
574 frame wrapper_frame = thread->last_frame();
575 CodeBlob* stub_cb = wrapper_frame.cb();
576 if (stub_cb != NULL &&
577 stub_cb->is_nmethod() &&
578 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
579 // A thread could potentially be in a critical native across
580 // more than one safepoint, so only update the critical state on
581 // the first one. When it returns it will perform the unlock.
582 if (!thread->do_critical_native_unlock()) {
583 #ifdef ASSERT
584 if (!thread->in_critical()) {
585 GC_locker::increment_debug_jni_lock_count();
586 }
587 #endif
588 thread->enter_critical();
589 // Make sure the native wrapper calls back on return to
590 // perform the needed critical unlock.
591 thread->set_critical_native_unlock();
592 }
593 }
594 }
595 }
599 // -------------------------------------------------------------------------------------------------------
600 // Implementation of Safepoint callback point
602 void SafepointSynchronize::block(JavaThread *thread) {
603 assert(thread != NULL, "thread must be set");
604 assert(thread->is_Java_thread(), "not a Java thread");
606 // Threads shouldn't block if they are in the middle of printing, but...
607 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
609 // Only bail from the block() call if the thread is gone from the
610 // thread list; starting to exit should still block.
611 if (thread->is_terminated()) {
612 // block current thread if we come here from native code when VM is gone
613 thread->block_if_vm_exited();
615 // otherwise do nothing
616 return;
617 }
619 JavaThreadState state = thread->thread_state();
620 thread->frame_anchor()->make_walkable(thread);
622 // Check that we have a valid thread_state at this point
623 switch(state) {
624 case _thread_in_vm_trans:
625 case _thread_in_Java: // From compiled code
627 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
628 // we pretend we are still in the VM.
629 thread->set_thread_state(_thread_in_vm);
631 if (is_synchronizing()) {
632 Atomic::inc (&TryingToBlock) ;
633 }
635 // We will always be holding the Safepoint_lock when we are examine the state
636 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
637 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
638 Safepoint_lock->lock_without_safepoint_check();
639 if (is_synchronizing()) {
640 // Decrement the number of threads to wait for and signal vm thread
641 assert(_waiting_to_block > 0, "sanity check");
642 _waiting_to_block--;
643 thread->safepoint_state()->set_has_called_back(true);
645 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
646 if (thread->in_critical()) {
647 // Notice that this thread is in a critical section
648 increment_jni_active_count();
649 }
651 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
652 if (_waiting_to_block == 0) {
653 Safepoint_lock->notify_all();
654 }
655 }
657 // We transition the thread to state _thread_blocked here, but
658 // we can't do our usual check for external suspension and then
659 // self-suspend after the lock_without_safepoint_check() call
660 // below because we are often called during transitions while
661 // we hold different locks. That would leave us suspended while
662 // holding a resource which results in deadlocks.
663 thread->set_thread_state(_thread_blocked);
664 Safepoint_lock->unlock();
666 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
667 // the entire safepoint, the threads will all line up here during the safepoint.
668 Threads_lock->lock_without_safepoint_check();
669 // restore original state. This is important if the thread comes from compiled code, so it
670 // will continue to execute with the _thread_in_Java state.
671 thread->set_thread_state(state);
672 Threads_lock->unlock();
673 break;
675 case _thread_in_native_trans:
676 case _thread_blocked_trans:
677 case _thread_new_trans:
678 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
679 thread->print_thread_state();
680 fatal("Deadlock in safepoint code. "
681 "Should have called back to the VM before blocking.");
682 }
684 // We transition the thread to state _thread_blocked here, but
685 // we can't do our usual check for external suspension and then
686 // self-suspend after the lock_without_safepoint_check() call
687 // below because we are often called during transitions while
688 // we hold different locks. That would leave us suspended while
689 // holding a resource which results in deadlocks.
690 thread->set_thread_state(_thread_blocked);
692 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
693 // the safepoint code might still be waiting for it to block. We need to change the state here,
694 // so it can see that it is at a safepoint.
696 // Block until the safepoint operation is completed.
697 Threads_lock->lock_without_safepoint_check();
699 // Restore state
700 thread->set_thread_state(state);
702 Threads_lock->unlock();
703 break;
705 default:
706 fatal(err_msg("Illegal threadstate encountered: %d", state));
707 }
709 // Check for pending. async. exceptions or suspends - except if the
710 // thread was blocked inside the VM. has_special_runtime_exit_condition()
711 // is called last since it grabs a lock and we only want to do that when
712 // we must.
713 //
714 // Note: we never deliver an async exception at a polling point as the
715 // compiler may not have an exception handler for it. The polling
716 // code will notice the async and deoptimize and the exception will
717 // be delivered. (Polling at a return point is ok though). Sure is
718 // a lot of bother for a deprecated feature...
719 //
720 // We don't deliver an async exception if the thread state is
721 // _thread_in_native_trans so JNI functions won't be called with
722 // a surprising pending exception. If the thread state is going back to java,
723 // async exception is checked in check_special_condition_for_native_trans().
725 if (state != _thread_blocked_trans &&
726 state != _thread_in_vm_trans &&
727 thread->has_special_runtime_exit_condition()) {
728 thread->handle_special_runtime_exit_condition(
729 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
730 }
731 }
733 // ------------------------------------------------------------------------------------------------------
734 // Exception handlers
736 #ifndef PRODUCT
737 #ifdef _LP64
738 #define PTR_PAD ""
739 #else
740 #define PTR_PAD " "
741 #endif
743 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
744 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false;
745 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
746 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
747 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
748 }
750 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
751 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false;
752 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
753 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
754 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
755 }
757 #ifdef SPARC
758 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
759 #ifdef _LP64
760 tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
761 const int incr = 1; // Increment to skip a long, in units of intptr_t
762 #else
763 tty->print_cr("--------+--address-+------before-----------+-------after----------+");
764 const int incr = 2; // Increment to skip a long, in units of intptr_t
765 #endif
766 tty->print_cr("---SP---|");
767 for( int i=0; i<16; i++ ) {
768 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
769 tty->print_cr("--------|");
770 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
771 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
772 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
773 tty->print_cr("--------|");
774 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;
775 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;
776 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;
777 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;
778 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
779 old_sp += incr; new_sp += incr; was_oops += incr;
780 // Skip the floats
781 tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
782 tty->print_cr("---FP---|");
783 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32;
784 for( int i2=0; i2<16; i2++ ) {
785 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
786 tty->print_cr("");
787 }
788 #endif // SPARC
789 #endif // PRODUCT
792 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
793 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
794 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
795 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
797 // Uncomment this to get some serious before/after printing of the
798 // Sparc safepoint-blob frame structure.
799 /*
800 intptr_t* sp = thread->last_Java_sp();
801 intptr_t stack_copy[150];
802 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
803 bool was_oops[150];
804 for( int i=0; i<150; i++ )
805 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
806 */
808 if (ShowSafepointMsgs) {
809 tty->print("handle_polling_page_exception: ");
810 }
812 if (PrintSafepointStatistics) {
813 inc_page_trap_count();
814 }
816 ThreadSafepointState* state = thread->safepoint_state();
818 state->handle_polling_page_exception();
819 // print_me(sp,stack_copy,was_oops);
820 }
823 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
824 if (!timeout_error_printed) {
825 timeout_error_printed = true;
826 // Print out the thread infor which didn't reach the safepoint for debugging
827 // purposes (useful when there are lots of threads in the debugger).
828 tty->print_cr("");
829 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
830 if (reason == _spinning_timeout) {
831 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
832 } else if (reason == _blocking_timeout) {
833 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
834 }
836 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
837 ThreadSafepointState *cur_state;
838 ResourceMark rm;
839 for(JavaThread *cur_thread = Threads::first(); cur_thread;
840 cur_thread = cur_thread->next()) {
841 cur_state = cur_thread->safepoint_state();
843 if (cur_thread->thread_state() != _thread_blocked &&
844 ((reason == _spinning_timeout && cur_state->is_running()) ||
845 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
846 tty->print("# ");
847 cur_thread->print();
848 tty->print_cr("");
849 }
850 }
851 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
852 }
854 // To debug the long safepoint, specify both DieOnSafepointTimeout &
855 // ShowMessageBoxOnError.
856 if (DieOnSafepointTimeout) {
857 char msg[1024];
858 VM_Operation *op = VMThread::vm_operation();
859 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
860 SafepointTimeoutDelay,
861 op != NULL ? op->name() : "no vm operation");
862 fatal(msg);
863 }
864 }
867 // -------------------------------------------------------------------------------------------------------
868 // Implementation of ThreadSafepointState
870 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
871 _thread = thread;
872 _type = _running;
873 _has_called_back = false;
874 _at_poll_safepoint = false;
875 }
877 void ThreadSafepointState::create(JavaThread *thread) {
878 ThreadSafepointState *state = new ThreadSafepointState(thread);
879 thread->set_safepoint_state(state);
880 }
882 void ThreadSafepointState::destroy(JavaThread *thread) {
883 if (thread->safepoint_state()) {
884 delete(thread->safepoint_state());
885 thread->set_safepoint_state(NULL);
886 }
887 }
889 void ThreadSafepointState::examine_state_of_thread() {
890 assert(is_running(), "better be running or just have hit safepoint poll");
892 JavaThreadState state = _thread->thread_state();
894 // Save the state at the start of safepoint processing.
895 _orig_thread_state = state;
897 // Check for a thread that is suspended. Note that thread resume tries
898 // to grab the Threads_lock which we own here, so a thread cannot be
899 // resumed during safepoint synchronization.
901 // We check to see if this thread is suspended without locking to
902 // avoid deadlocking with a third thread that is waiting for this
903 // thread to be suspended. The third thread can notice the safepoint
904 // that we're trying to start at the beginning of its SR_lock->wait()
905 // call. If that happens, then the third thread will block on the
906 // safepoint while still holding the underlying SR_lock. We won't be
907 // able to get the SR_lock and we'll deadlock.
908 //
909 // We don't need to grab the SR_lock here for two reasons:
910 // 1) The suspend flags are both volatile and are set with an
911 // Atomic::cmpxchg() call so we should see the suspended
912 // state right away.
913 // 2) We're being called from the safepoint polling loop; if
914 // we don't see the suspended state on this iteration, then
915 // we'll come around again.
916 //
917 bool is_suspended = _thread->is_ext_suspended();
918 if (is_suspended) {
919 roll_forward(_at_safepoint);
920 return;
921 }
923 // Some JavaThread states have an initial safepoint state of
924 // running, but are actually at a safepoint. We will happily
925 // agree and update the safepoint state here.
926 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
927 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
928 roll_forward(_at_safepoint);
929 return;
930 }
932 if (state == _thread_in_vm) {
933 roll_forward(_call_back);
934 return;
935 }
937 // All other thread states will continue to run until they
938 // transition and self-block in state _blocked
939 // Safepoint polling in compiled code causes the Java threads to do the same.
940 // Note: new threads may require a malloc so they must be allowed to finish
942 assert(is_running(), "examine_state_of_thread on non-running thread");
943 return;
944 }
946 // Returns true is thread could not be rolled forward at present position.
947 void ThreadSafepointState::roll_forward(suspend_type type) {
948 _type = type;
950 switch(_type) {
951 case _at_safepoint:
952 SafepointSynchronize::signal_thread_at_safepoint();
953 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
954 if (_thread->in_critical()) {
955 // Notice that this thread is in a critical section
956 SafepointSynchronize::increment_jni_active_count();
957 }
958 break;
960 case _call_back:
961 set_has_called_back(false);
962 break;
964 case _running:
965 default:
966 ShouldNotReachHere();
967 }
968 }
970 void ThreadSafepointState::restart() {
971 switch(type()) {
972 case _at_safepoint:
973 case _call_back:
974 break;
976 case _running:
977 default:
978 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
979 _thread, _type);
980 _thread->print();
981 ShouldNotReachHere();
982 }
983 _type = _running;
984 set_has_called_back(false);
985 }
988 void ThreadSafepointState::print_on(outputStream *st) const {
989 const char *s;
991 switch(_type) {
992 case _running : s = "_running"; break;
993 case _at_safepoint : s = "_at_safepoint"; break;
994 case _call_back : s = "_call_back"; break;
995 default:
996 ShouldNotReachHere();
997 }
999 st->print_cr("Thread: " INTPTR_FORMAT
1000 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1001 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1002 _at_poll_safepoint);
1004 _thread->print_thread_state_on(st);
1005 }
1008 // ---------------------------------------------------------------------------------------------------------------------
1010 // Block the thread at the safepoint poll or poll return.
1011 void ThreadSafepointState::handle_polling_page_exception() {
1013 // Check state. block() will set thread state to thread_in_vm which will
1014 // cause the safepoint state _type to become _call_back.
1015 assert(type() == ThreadSafepointState::_running,
1016 "polling page exception on thread not running state");
1018 // Step 1: Find the nmethod from the return address
1019 if (ShowSafepointMsgs && Verbose) {
1020 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1021 }
1022 address real_return_addr = thread()->saved_exception_pc();
1024 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1025 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1026 nmethod* nm = (nmethod*)cb;
1028 // Find frame of caller
1029 frame stub_fr = thread()->last_frame();
1030 CodeBlob* stub_cb = stub_fr.cb();
1031 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1032 RegisterMap map(thread(), true);
1033 frame caller_fr = stub_fr.sender(&map);
1035 // Should only be poll_return or poll
1036 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1038 // This is a poll immediately before a return. The exception handling code
1039 // has already had the effect of causing the return to occur, so the execution
1040 // will continue immediately after the call. In addition, the oopmap at the
1041 // return point does not mark the return value as an oop (if it is), so
1042 // it needs a handle here to be updated.
1043 if( nm->is_at_poll_return(real_return_addr) ) {
1044 // See if return type is an oop.
1045 bool return_oop = nm->method()->is_returning_oop();
1046 Handle return_value;
1047 if (return_oop) {
1048 // The oop result has been saved on the stack together with all
1049 // the other registers. In order to preserve it over GCs we need
1050 // to keep it in a handle.
1051 oop result = caller_fr.saved_oop_result(&map);
1052 assert(result == NULL || result->is_oop(), "must be oop");
1053 return_value = Handle(thread(), result);
1054 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1055 }
1057 // Block the thread
1058 SafepointSynchronize::block(thread());
1060 // restore oop result, if any
1061 if (return_oop) {
1062 caller_fr.set_saved_oop_result(&map, return_value());
1063 }
1064 }
1066 // This is a safepoint poll. Verify the return address and block.
1067 else {
1068 set_at_poll_safepoint(true);
1070 // verify the blob built the "return address" correctly
1071 assert(real_return_addr == caller_fr.pc(), "must match");
1073 // Block the thread
1074 SafepointSynchronize::block(thread());
1075 set_at_poll_safepoint(false);
1077 // If we have a pending async exception deoptimize the frame
1078 // as otherwise we may never deliver it.
1079 if (thread()->has_async_condition()) {
1080 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1081 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1082 }
1084 // If an exception has been installed we must check for a pending deoptimization
1085 // Deoptimize frame if exception has been thrown.
1087 if (thread()->has_pending_exception() ) {
1088 RegisterMap map(thread(), true);
1089 frame caller_fr = stub_fr.sender(&map);
1090 if (caller_fr.is_deoptimized_frame()) {
1091 // The exception patch will destroy registers that are still
1092 // live and will be needed during deoptimization. Defer the
1093 // Async exception should have defered the exception until the
1094 // next safepoint which will be detected when we get into
1095 // the interpreter so if we have an exception now things
1096 // are messed up.
1098 fatal("Exception installed and deoptimization is pending");
1099 }
1100 }
1101 }
1102 }
1105 //
1106 // Statistics & Instrumentations
1107 //
1108 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1109 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1110 int SafepointSynchronize::_cur_stat_index = 0;
1111 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1112 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1113 jlong SafepointSynchronize::_max_sync_time = 0;
1114 jlong SafepointSynchronize::_max_vmop_time = 0;
1115 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1117 static jlong cleanup_end_time = 0;
1118 static bool need_to_track_page_armed_status = false;
1119 static bool init_done = false;
1121 // Helper method to print the header.
1122 static void print_header() {
1123 tty->print(" vmop "
1124 "[threads: total initially_running wait_to_block] ");
1125 tty->print("[time: spin block sync cleanup vmop] ");
1127 // no page armed status printed out if it is always armed.
1128 if (need_to_track_page_armed_status) {
1129 tty->print("page_armed ");
1130 }
1132 tty->print_cr("page_trap_count");
1133 }
1135 void SafepointSynchronize::deferred_initialize_stat() {
1136 if (init_done) return;
1138 if (PrintSafepointStatisticsCount <= 0) {
1139 fatal("Wrong PrintSafepointStatisticsCount");
1140 }
1142 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1143 // be printed right away, in which case, _safepoint_stats will regress to
1144 // a single element array. Otherwise, it is a circular ring buffer with default
1145 // size of PrintSafepointStatisticsCount.
1146 int stats_array_size;
1147 if (PrintSafepointStatisticsTimeout > 0) {
1148 stats_array_size = 1;
1149 PrintSafepointStatistics = true;
1150 } else {
1151 stats_array_size = PrintSafepointStatisticsCount;
1152 }
1153 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1154 * sizeof(SafepointStats), mtInternal);
1155 guarantee(_safepoint_stats != NULL,
1156 "not enough memory for safepoint instrumentation data");
1158 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1159 need_to_track_page_armed_status = true;
1160 }
1161 init_done = true;
1162 }
1164 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1165 assert(init_done, "safepoint statistics array hasn't been initialized");
1166 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1168 spstat->_time_stamp = _ts_of_current_safepoint;
1170 VM_Operation *op = VMThread::vm_operation();
1171 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1172 if (op != NULL) {
1173 _safepoint_reasons[spstat->_vmop_type]++;
1174 }
1176 spstat->_nof_total_threads = nof_threads;
1177 spstat->_nof_initial_running_threads = nof_running;
1178 spstat->_nof_threads_hit_page_trap = 0;
1180 // Records the start time of spinning. The real time spent on spinning
1181 // will be adjusted when spin is done. Same trick is applied for time
1182 // spent on waiting for threads to block.
1183 if (nof_running != 0) {
1184 spstat->_time_to_spin = os::javaTimeNanos();
1185 } else {
1186 spstat->_time_to_spin = 0;
1187 }
1188 }
1190 void SafepointSynchronize::update_statistics_on_spin_end() {
1191 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1193 jlong cur_time = os::javaTimeNanos();
1195 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1196 if (spstat->_nof_initial_running_threads != 0) {
1197 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1198 }
1200 if (need_to_track_page_armed_status) {
1201 spstat->_page_armed = (PageArmed == 1);
1202 }
1204 // Records the start time of waiting for to block. Updated when block is done.
1205 if (_waiting_to_block != 0) {
1206 spstat->_time_to_wait_to_block = cur_time;
1207 } else {
1208 spstat->_time_to_wait_to_block = 0;
1209 }
1210 }
1212 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1213 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1215 if (spstat->_nof_threads_wait_to_block != 0) {
1216 spstat->_time_to_wait_to_block = end_time -
1217 spstat->_time_to_wait_to_block;
1218 }
1220 // Records the end time of sync which will be used to calculate the total
1221 // vm operation time. Again, the real time spending in syncing will be deducted
1222 // from the start of the sync time later when end_statistics is called.
1223 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1224 if (spstat->_time_to_sync > _max_sync_time) {
1225 _max_sync_time = spstat->_time_to_sync;
1226 }
1228 spstat->_time_to_do_cleanups = end_time;
1229 }
1231 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1232 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1234 // Record how long spent in cleanup tasks.
1235 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1237 cleanup_end_time = end_time;
1238 }
1240 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1241 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1243 // Update the vm operation time.
1244 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1245 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1246 _max_vmop_time = spstat->_time_to_exec_vmop;
1247 }
1248 // Only the sync time longer than the specified
1249 // PrintSafepointStatisticsTimeout will be printed out right away.
1250 // By default, it is -1 meaning all samples will be put into the list.
1251 if ( PrintSafepointStatisticsTimeout > 0) {
1252 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1253 print_statistics();
1254 }
1255 } else {
1256 // The safepoint statistics will be printed out when the _safepoin_stats
1257 // array fills up.
1258 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1259 print_statistics();
1260 _cur_stat_index = 0;
1261 } else {
1262 _cur_stat_index++;
1263 }
1264 }
1265 }
1267 void SafepointSynchronize::print_statistics() {
1268 SafepointStats* sstats = _safepoint_stats;
1270 for (int index = 0; index <= _cur_stat_index; index++) {
1271 if (index % 30 == 0) {
1272 print_header();
1273 }
1274 sstats = &_safepoint_stats[index];
1275 tty->print("%.3f: ", sstats->_time_stamp);
1276 tty->print("%-26s ["
1277 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1278 " ] ",
1279 sstats->_vmop_type == -1 ? "no vm operation" :
1280 VM_Operation::name(sstats->_vmop_type),
1281 sstats->_nof_total_threads,
1282 sstats->_nof_initial_running_threads,
1283 sstats->_nof_threads_wait_to_block);
1284 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1285 tty->print(" ["
1286 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1287 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1288 INT64_FORMAT_W(6)" ] ",
1289 sstats->_time_to_spin / MICROUNITS,
1290 sstats->_time_to_wait_to_block / MICROUNITS,
1291 sstats->_time_to_sync / MICROUNITS,
1292 sstats->_time_to_do_cleanups / MICROUNITS,
1293 sstats->_time_to_exec_vmop / MICROUNITS);
1295 if (need_to_track_page_armed_status) {
1296 tty->print(INT32_FORMAT" ", sstats->_page_armed);
1297 }
1298 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
1299 }
1300 }
1302 // This method will be called when VM exits. It will first call
1303 // print_statistics to print out the rest of the sampling. Then
1304 // it tries to summarize the sampling.
1305 void SafepointSynchronize::print_stat_on_exit() {
1306 if (_safepoint_stats == NULL) return;
1308 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1310 // During VM exit, end_statistics may not get called and in that
1311 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1312 // don't print it out.
1313 // Approximate the vm op time.
1314 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1315 os::javaTimeNanos() - cleanup_end_time;
1317 if ( PrintSafepointStatisticsTimeout < 0 ||
1318 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1319 print_statistics();
1320 }
1321 tty->print_cr("");
1323 // Print out polling page sampling status.
1324 if (!need_to_track_page_armed_status) {
1325 if (UseCompilerSafepoints) {
1326 tty->print_cr("Polling page always armed");
1327 }
1328 } else {
1329 tty->print_cr("Defer polling page loop count = %d\n",
1330 DeferPollingPageLoopCount);
1331 }
1333 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1334 if (_safepoint_reasons[index] != 0) {
1335 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1336 _safepoint_reasons[index]);
1337 }
1338 }
1340 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1341 _coalesced_vmop_count);
1342 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
1343 _max_sync_time / MICROUNITS);
1344 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1345 INT64_FORMAT_W(5)" ms",
1346 _max_vmop_time / MICROUNITS);
1347 }
1349 // ------------------------------------------------------------------------------------------------
1350 // Non-product code
1352 #ifndef PRODUCT
1354 void SafepointSynchronize::print_state() {
1355 if (_state == _not_synchronized) {
1356 tty->print_cr("not synchronized");
1357 } else if (_state == _synchronizing || _state == _synchronized) {
1358 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1359 "synchronized");
1361 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1362 cur->safepoint_state()->print();
1363 }
1364 }
1365 }
1367 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1368 if (ShowSafepointMsgs) {
1369 va_list ap;
1370 va_start(ap, format);
1371 tty->vprint_cr(format, ap);
1372 va_end(ap);
1373 }
1374 }
1376 #endif // !PRODUCT