Mon, 18 Mar 2013 13:19:06 +0100
8008555: Debugging code in compiled method sometimes leaks memory
Summary: support for strings that have same life-time as code that uses them.
Reviewed-by: kvn, twisti
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.
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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 #include "utilities/macros.hpp"
56 #ifdef TARGET_ARCH_x86
57 # include "nativeInst_x86.hpp"
58 # include "vmreg_x86.inline.hpp"
59 #endif
60 #ifdef TARGET_ARCH_sparc
61 # include "nativeInst_sparc.hpp"
62 # include "vmreg_sparc.inline.hpp"
63 #endif
64 #ifdef TARGET_ARCH_zero
65 # include "nativeInst_zero.hpp"
66 # include "vmreg_zero.inline.hpp"
67 #endif
68 #ifdef TARGET_ARCH_arm
69 # include "nativeInst_arm.hpp"
70 # include "vmreg_arm.inline.hpp"
71 #endif
72 #ifdef TARGET_ARCH_ppc
73 # include "nativeInst_ppc.hpp"
74 # include "vmreg_ppc.inline.hpp"
75 #endif
76 #if INCLUDE_ALL_GCS
77 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
78 #include "gc_implementation/shared/concurrentGCThread.hpp"
79 #endif // INCLUDE_ALL_GCS
80 #ifdef COMPILER1
81 #include "c1/c1_globals.hpp"
82 #endif
84 // --------------------------------------------------------------------------------------------------
85 // Implementation of Safepoint begin/end
87 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
88 volatile int SafepointSynchronize::_waiting_to_block = 0;
89 volatile int SafepointSynchronize::_safepoint_counter = 0;
90 int SafepointSynchronize::_current_jni_active_count = 0;
91 long SafepointSynchronize::_end_of_last_safepoint = 0;
92 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
93 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
94 static bool timeout_error_printed = false;
96 // Roll all threads forward to a safepoint and suspend them all
97 void SafepointSynchronize::begin() {
99 Thread* myThread = Thread::current();
100 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
102 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
103 _safepoint_begin_time = os::javaTimeNanos();
104 _ts_of_current_safepoint = tty->time_stamp().seconds();
105 }
107 #if INCLUDE_ALL_GCS
108 if (UseConcMarkSweepGC) {
109 // In the future we should investigate whether CMS can use the
110 // more-general mechanism below. DLD (01/05).
111 ConcurrentMarkSweepThread::synchronize(false);
112 } else if (UseG1GC) {
113 ConcurrentGCThread::safepoint_synchronize();
114 }
115 #endif // INCLUDE_ALL_GCS
117 // By getting the Threads_lock, we assure that no threads are about to start or
118 // exit. It is released again in SafepointSynchronize::end().
119 Threads_lock->lock();
121 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
123 int nof_threads = Threads::number_of_threads();
125 if (TraceSafepoint) {
126 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
127 }
129 RuntimeService::record_safepoint_begin();
131 MutexLocker mu(Safepoint_lock);
133 // Reset the count of active JNI critical threads
134 _current_jni_active_count = 0;
136 // Set number of threads to wait for, before we initiate the callbacks
137 _waiting_to_block = nof_threads;
138 TryingToBlock = 0 ;
139 int still_running = nof_threads;
141 // Save the starting time, so that it can be compared to see if this has taken
142 // too long to complete.
143 jlong safepoint_limit_time;
144 timeout_error_printed = false;
146 // PrintSafepointStatisticsTimeout can be specified separately. When
147 // specified, PrintSafepointStatistics will be set to true in
148 // deferred_initialize_stat method. The initialization has to be done
149 // early enough to avoid any races. See bug 6880029 for details.
150 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
151 deferred_initialize_stat();
152 }
154 // Begin the process of bringing the system to a safepoint.
155 // Java threads can be in several different states and are
156 // stopped by different mechanisms:
157 //
158 // 1. Running interpreted
159 // The interpeter dispatch table is changed to force it to
160 // check for a safepoint condition between bytecodes.
161 // 2. Running in native code
162 // When returning from the native code, a Java thread must check
163 // the safepoint _state to see if we must block. If the
164 // VM thread sees a Java thread in native, it does
165 // not wait for this thread to block. The order of the memory
166 // writes and reads of both the safepoint state and the Java
167 // threads state is critical. In order to guarantee that the
168 // memory writes are serialized with respect to each other,
169 // the VM thread issues a memory barrier instruction
170 // (on MP systems). In order to avoid the overhead of issuing
171 // a memory barrier for each Java thread making native calls, each Java
172 // thread performs a write to a single memory page after changing
173 // the thread state. The VM thread performs a sequence of
174 // mprotect OS calls which forces all previous writes from all
175 // Java threads to be serialized. This is done in the
176 // os::serialize_thread_states() call. This has proven to be
177 // much more efficient than executing a membar instruction
178 // on every call to native code.
179 // 3. Running compiled Code
180 // Compiled code reads a global (Safepoint Polling) page that
181 // is set to fault if we are trying to get to a safepoint.
182 // 4. Blocked
183 // A thread which is blocked will not be allowed to return from the
184 // block condition until the safepoint operation is complete.
185 // 5. In VM or Transitioning between states
186 // If a Java thread is currently running in the VM or transitioning
187 // between states, the safepointing code will wait for the thread to
188 // block itself when it attempts transitions to a new state.
189 //
190 _state = _synchronizing;
191 OrderAccess::fence();
193 // Flush all thread states to memory
194 if (!UseMembar) {
195 os::serialize_thread_states();
196 }
198 // Make interpreter safepoint aware
199 Interpreter::notice_safepoints();
201 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
202 // Make polling safepoint aware
203 guarantee (PageArmed == 0, "invariant") ;
204 PageArmed = 1 ;
205 os::make_polling_page_unreadable();
206 }
208 // Consider using active_processor_count() ... but that call is expensive.
209 int ncpus = os::processor_count() ;
211 #ifdef ASSERT
212 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
213 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
214 // Clear the visited flag to ensure that the critical counts are collected properly.
215 cur->set_visited_for_critical_count(false);
216 }
217 #endif // ASSERT
219 if (SafepointTimeout)
220 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
222 // Iterate through all threads until it have been determined how to stop them all at a safepoint
223 unsigned int iterations = 0;
224 int steps = 0 ;
225 while(still_running > 0) {
226 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
227 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
228 ThreadSafepointState *cur_state = cur->safepoint_state();
229 if (cur_state->is_running()) {
230 cur_state->examine_state_of_thread();
231 if (!cur_state->is_running()) {
232 still_running--;
233 // consider adjusting steps downward:
234 // steps = 0
235 // steps -= NNN
236 // steps >>= 1
237 // steps = MIN(steps, 2000-100)
238 // if (iterations != 0) steps -= NNN
239 }
240 if (TraceSafepoint && Verbose) cur_state->print();
241 }
242 }
244 if (PrintSafepointStatistics && iterations == 0) {
245 begin_statistics(nof_threads, still_running);
246 }
248 if (still_running > 0) {
249 // Check for if it takes to long
250 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
251 print_safepoint_timeout(_spinning_timeout);
252 }
254 // Spin to avoid context switching.
255 // There's a tension between allowing the mutators to run (and rendezvous)
256 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
257 // a mutator might otherwise use profitably to reach a safepoint. Excessive
258 // spinning by the VM thread on a saturated system can increase rendezvous latency.
259 // Blocking or yielding incur their own penalties in the form of context switching
260 // and the resultant loss of $ residency.
261 //
262 // Further complicating matters is that yield() does not work as naively expected
263 // on many platforms -- yield() does not guarantee that any other ready threads
264 // will run. As such we revert yield_all() after some number of iterations.
265 // Yield_all() is implemented as a short unconditional sleep on some platforms.
266 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
267 // can actually increase the time it takes the VM thread to detect that a system-wide
268 // stop-the-world safepoint has been reached. In a pathological scenario such as that
269 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
270 // In that case the mutators will be stalled waiting for the safepoint to complete and the
271 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
272 // will eventually wake up and detect that all mutators are safe, at which point
273 // we'll again make progress.
274 //
275 // Beware too that that the VMThread typically runs at elevated priority.
276 // Its default priority is higher than the default mutator priority.
277 // Obviously, this complicates spinning.
278 //
279 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
280 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
281 //
282 // See the comments in synchronizer.cpp for additional remarks on spinning.
283 //
284 // In the future we might:
285 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
286 // This is tricky as the path used by a thread exiting the JVM (say on
287 // on JNI call-out) simply stores into its state field. The burden
288 // is placed on the VM thread, which must poll (spin).
289 // 2. Find something useful to do while spinning. If the safepoint is GC-related
290 // we might aggressively scan the stacks of threads that are already safe.
291 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
292 // If all the mutators are ONPROC there's no reason to sleep or yield.
293 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
294 // 5. Check system saturation. If the system is not fully saturated then
295 // simply spin and avoid sleep/yield.
296 // 6. As still-running mutators rendezvous they could unpark the sleeping
297 // VMthread. This works well for still-running mutators that become
298 // safe. The VMthread must still poll for mutators that call-out.
299 // 7. Drive the policy on time-since-begin instead of iterations.
300 // 8. Consider making the spin duration a function of the # of CPUs:
301 // Spin = (((ncpus-1) * M) + K) + F(still_running)
302 // Alternately, instead of counting iterations of the outer loop
303 // we could count the # of threads visited in the inner loop, above.
304 // 9. On windows consider using the return value from SwitchThreadTo()
305 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
307 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
308 guarantee (PageArmed == 0, "invariant") ;
309 PageArmed = 1 ;
310 os::make_polling_page_unreadable();
311 }
313 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
314 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
315 ++steps ;
316 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
317 SpinPause() ; // MP-Polite spin
318 } else
319 if (steps < DeferThrSuspendLoopCount) {
320 os::NakedYield() ;
321 } else {
322 os::yield_all(steps) ;
323 // Alternately, the VM thread could transiently depress its scheduling priority or
324 // transiently increase the priority of the tardy mutator(s).
325 }
327 iterations ++ ;
328 }
329 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
330 }
331 assert(still_running == 0, "sanity check");
333 if (PrintSafepointStatistics) {
334 update_statistics_on_spin_end();
335 }
337 // wait until all threads are stopped
338 while (_waiting_to_block > 0) {
339 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
340 if (!SafepointTimeout || timeout_error_printed) {
341 Safepoint_lock->wait(true); // true, means with no safepoint checks
342 } else {
343 // Compute remaining time
344 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
346 // If there is no remaining time, then there is an error
347 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
348 print_safepoint_timeout(_blocking_timeout);
349 }
350 }
351 }
352 assert(_waiting_to_block == 0, "sanity check");
354 #ifndef PRODUCT
355 if (SafepointTimeout) {
356 jlong current_time = os::javaTimeNanos();
357 if (safepoint_limit_time < current_time) {
358 tty->print_cr("# SafepointSynchronize: Finished after "
359 INT64_FORMAT_W(6) " ms",
360 ((current_time - safepoint_limit_time) / MICROUNITS +
361 SafepointTimeoutDelay));
362 }
363 }
364 #endif
366 assert((_safepoint_counter & 0x1) == 0, "must be even");
367 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
368 _safepoint_counter ++;
370 // Record state
371 _state = _synchronized;
373 OrderAccess::fence();
375 #ifdef ASSERT
376 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
377 // make sure all the threads were visited
378 assert(cur->was_visited_for_critical_count(), "missed a thread");
379 }
380 #endif // ASSERT
382 // Update the count of active JNI critical regions
383 GC_locker::set_jni_lock_count(_current_jni_active_count);
385 if (TraceSafepoint) {
386 VM_Operation *op = VMThread::vm_operation();
387 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
388 }
390 RuntimeService::record_safepoint_synchronized();
391 if (PrintSafepointStatistics) {
392 update_statistics_on_sync_end(os::javaTimeNanos());
393 }
395 // Call stuff that needs to be run when a safepoint is just about to be completed
396 do_cleanup_tasks();
398 if (PrintSafepointStatistics) {
399 // Record how much time spend on the above cleanup tasks
400 update_statistics_on_cleanup_end(os::javaTimeNanos());
401 }
402 }
404 // Wake up all threads, so they are ready to resume execution after the safepoint
405 // operation has been carried out
406 void SafepointSynchronize::end() {
408 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
409 assert((_safepoint_counter & 0x1) == 1, "must be odd");
410 _safepoint_counter ++;
411 // memory fence isn't required here since an odd _safepoint_counter
412 // value can do no harm and a fence is issued below anyway.
414 DEBUG_ONLY(Thread* myThread = Thread::current();)
415 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
417 if (PrintSafepointStatistics) {
418 end_statistics(os::javaTimeNanos());
419 }
421 #ifdef ASSERT
422 // A pending_exception cannot be installed during a safepoint. The threads
423 // may install an async exception after they come back from a safepoint into
424 // pending_exception after they unblock. But that should happen later.
425 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
426 assert (!(cur->has_pending_exception() &&
427 cur->safepoint_state()->is_at_poll_safepoint()),
428 "safepoint installed a pending exception");
429 }
430 #endif // ASSERT
432 if (PageArmed) {
433 // Make polling safepoint aware
434 os::make_polling_page_readable();
435 PageArmed = 0 ;
436 }
438 // Remove safepoint check from interpreter
439 Interpreter::ignore_safepoints();
441 {
442 MutexLocker mu(Safepoint_lock);
444 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
446 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
447 // when they get restarted.
448 _state = _not_synchronized;
449 OrderAccess::fence();
451 if (TraceSafepoint) {
452 tty->print_cr("Leaving safepoint region");
453 }
455 // Start suspended threads
456 for(JavaThread *current = Threads::first(); current; current = current->next()) {
457 // A problem occurring on Solaris is when attempting to restart threads
458 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
459 // to the next one (since it has been running the longest). We then have
460 // to wait for a cpu to become available before we can continue restarting
461 // threads.
462 // FIXME: This causes the performance of the VM to degrade when active and with
463 // large numbers of threads. Apparently this is due to the synchronous nature
464 // of suspending threads.
465 //
466 // TODO-FIXME: the comments above are vestigial and no longer apply.
467 // Furthermore, using solaris' schedctl in this particular context confers no benefit
468 if (VMThreadHintNoPreempt) {
469 os::hint_no_preempt();
470 }
471 ThreadSafepointState* cur_state = current->safepoint_state();
472 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
473 cur_state->restart();
474 assert(cur_state->is_running(), "safepoint state has not been reset");
475 }
477 RuntimeService::record_safepoint_end();
479 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
480 // blocked in signal_thread_blocked
481 Threads_lock->unlock();
483 }
484 #if INCLUDE_ALL_GCS
485 // If there are any concurrent GC threads resume them.
486 if (UseConcMarkSweepGC) {
487 ConcurrentMarkSweepThread::desynchronize(false);
488 } else if (UseG1GC) {
489 ConcurrentGCThread::safepoint_desynchronize();
490 }
491 #endif // INCLUDE_ALL_GCS
492 // record this time so VMThread can keep track how much time has elasped
493 // since last safepoint.
494 _end_of_last_safepoint = os::javaTimeMillis();
495 }
497 bool SafepointSynchronize::is_cleanup_needed() {
498 // Need a safepoint if some inline cache buffers is non-empty
499 if (!InlineCacheBuffer::is_empty()) return true;
500 return false;
501 }
505 // Various cleaning tasks that should be done periodically at safepoints
506 void SafepointSynchronize::do_cleanup_tasks() {
507 {
508 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
509 ObjectSynchronizer::deflate_idle_monitors();
510 }
512 {
513 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
514 InlineCacheBuffer::update_inline_caches();
515 }
516 {
517 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
518 CompilationPolicy::policy()->do_safepoint_work();
519 }
521 {
522 TraceTime t4("sweeping nmethods", TraceSafepointCleanupTime);
523 NMethodSweeper::scan_stacks();
524 }
526 if (SymbolTable::needs_rehashing()) {
527 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
528 SymbolTable::rehash_table();
529 }
531 if (StringTable::needs_rehashing()) {
532 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
533 StringTable::rehash_table();
534 }
536 // rotate log files?
537 if (UseGCLogFileRotation) {
538 gclog_or_tty->rotate_log();
539 }
541 if (MemTracker::is_on()) {
542 MemTracker::sync();
543 }
544 }
547 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
548 switch(state) {
549 case _thread_in_native:
550 // native threads are safe if they have no java stack or have walkable stack
551 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
553 // blocked threads should have already have walkable stack
554 case _thread_blocked:
555 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
556 return true;
558 default:
559 return false;
560 }
561 }
564 // See if the thread is running inside a lazy critical native and
565 // update the thread critical count if so. Also set a suspend flag to
566 // cause the native wrapper to return into the JVM to do the unlock
567 // once the native finishes.
568 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
569 if (state == _thread_in_native &&
570 thread->has_last_Java_frame() &&
571 thread->frame_anchor()->walkable()) {
572 // This thread might be in a critical native nmethod so look at
573 // the top of the stack and increment the critical count if it
574 // is.
575 frame wrapper_frame = thread->last_frame();
576 CodeBlob* stub_cb = wrapper_frame.cb();
577 if (stub_cb != NULL &&
578 stub_cb->is_nmethod() &&
579 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
580 // A thread could potentially be in a critical native across
581 // more than one safepoint, so only update the critical state on
582 // the first one. When it returns it will perform the unlock.
583 if (!thread->do_critical_native_unlock()) {
584 #ifdef ASSERT
585 if (!thread->in_critical()) {
586 GC_locker::increment_debug_jni_lock_count();
587 }
588 #endif
589 thread->enter_critical();
590 // Make sure the native wrapper calls back on return to
591 // perform the needed critical unlock.
592 thread->set_critical_native_unlock();
593 }
594 }
595 }
596 }
600 // -------------------------------------------------------------------------------------------------------
601 // Implementation of Safepoint callback point
603 void SafepointSynchronize::block(JavaThread *thread) {
604 assert(thread != NULL, "thread must be set");
605 assert(thread->is_Java_thread(), "not a Java thread");
607 // Threads shouldn't block if they are in the middle of printing, but...
608 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
610 // Only bail from the block() call if the thread is gone from the
611 // thread list; starting to exit should still block.
612 if (thread->is_terminated()) {
613 // block current thread if we come here from native code when VM is gone
614 thread->block_if_vm_exited();
616 // otherwise do nothing
617 return;
618 }
620 JavaThreadState state = thread->thread_state();
621 thread->frame_anchor()->make_walkable(thread);
623 // Check that we have a valid thread_state at this point
624 switch(state) {
625 case _thread_in_vm_trans:
626 case _thread_in_Java: // From compiled code
628 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
629 // we pretend we are still in the VM.
630 thread->set_thread_state(_thread_in_vm);
632 if (is_synchronizing()) {
633 Atomic::inc (&TryingToBlock) ;
634 }
636 // We will always be holding the Safepoint_lock when we are examine the state
637 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
638 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
639 Safepoint_lock->lock_without_safepoint_check();
640 if (is_synchronizing()) {
641 // Decrement the number of threads to wait for and signal vm thread
642 assert(_waiting_to_block > 0, "sanity check");
643 _waiting_to_block--;
644 thread->safepoint_state()->set_has_called_back(true);
646 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
647 if (thread->in_critical()) {
648 // Notice that this thread is in a critical section
649 increment_jni_active_count();
650 }
652 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
653 if (_waiting_to_block == 0) {
654 Safepoint_lock->notify_all();
655 }
656 }
658 // We transition the thread to state _thread_blocked here, but
659 // we can't do our usual check for external suspension and then
660 // self-suspend after the lock_without_safepoint_check() call
661 // below because we are often called during transitions while
662 // we hold different locks. That would leave us suspended while
663 // holding a resource which results in deadlocks.
664 thread->set_thread_state(_thread_blocked);
665 Safepoint_lock->unlock();
667 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
668 // the entire safepoint, the threads will all line up here during the safepoint.
669 Threads_lock->lock_without_safepoint_check();
670 // restore original state. This is important if the thread comes from compiled code, so it
671 // will continue to execute with the _thread_in_Java state.
672 thread->set_thread_state(state);
673 Threads_lock->unlock();
674 break;
676 case _thread_in_native_trans:
677 case _thread_blocked_trans:
678 case _thread_new_trans:
679 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
680 thread->print_thread_state();
681 fatal("Deadlock in safepoint code. "
682 "Should have called back to the VM before blocking.");
683 }
685 // We transition the thread to state _thread_blocked here, but
686 // we can't do our usual check for external suspension and then
687 // self-suspend after the lock_without_safepoint_check() call
688 // below because we are often called during transitions while
689 // we hold different locks. That would leave us suspended while
690 // holding a resource which results in deadlocks.
691 thread->set_thread_state(_thread_blocked);
693 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
694 // the safepoint code might still be waiting for it to block. We need to change the state here,
695 // so it can see that it is at a safepoint.
697 // Block until the safepoint operation is completed.
698 Threads_lock->lock_without_safepoint_check();
700 // Restore state
701 thread->set_thread_state(state);
703 Threads_lock->unlock();
704 break;
706 default:
707 fatal(err_msg("Illegal threadstate encountered: %d", state));
708 }
710 // Check for pending. async. exceptions or suspends - except if the
711 // thread was blocked inside the VM. has_special_runtime_exit_condition()
712 // is called last since it grabs a lock and we only want to do that when
713 // we must.
714 //
715 // Note: we never deliver an async exception at a polling point as the
716 // compiler may not have an exception handler for it. The polling
717 // code will notice the async and deoptimize and the exception will
718 // be delivered. (Polling at a return point is ok though). Sure is
719 // a lot of bother for a deprecated feature...
720 //
721 // We don't deliver an async exception if the thread state is
722 // _thread_in_native_trans so JNI functions won't be called with
723 // a surprising pending exception. If the thread state is going back to java,
724 // async exception is checked in check_special_condition_for_native_trans().
726 if (state != _thread_blocked_trans &&
727 state != _thread_in_vm_trans &&
728 thread->has_special_runtime_exit_condition()) {
729 thread->handle_special_runtime_exit_condition(
730 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
731 }
732 }
734 // ------------------------------------------------------------------------------------------------------
735 // Exception handlers
737 #ifndef PRODUCT
738 #ifdef _LP64
739 #define PTR_PAD ""
740 #else
741 #define PTR_PAD " "
742 #endif
744 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
745 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false;
746 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
747 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
748 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
749 }
751 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
752 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false;
753 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
754 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
755 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
756 }
758 #ifdef SPARC
759 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
760 #ifdef _LP64
761 tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
762 const int incr = 1; // Increment to skip a long, in units of intptr_t
763 #else
764 tty->print_cr("--------+--address-+------before-----------+-------after----------+");
765 const int incr = 2; // Increment to skip a long, in units of intptr_t
766 #endif
767 tty->print_cr("---SP---|");
768 for( int i=0; i<16; i++ ) {
769 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
770 tty->print_cr("--------|");
771 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
772 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
773 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
774 tty->print_cr("--------|");
775 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;
776 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;
777 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;
778 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;
779 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
780 old_sp += incr; new_sp += incr; was_oops += incr;
781 // Skip the floats
782 tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
783 tty->print_cr("---FP---|");
784 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32;
785 for( int i2=0; i2<16; i2++ ) {
786 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
787 tty->print_cr("");
788 }
789 #endif // SPARC
790 #endif // PRODUCT
793 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
794 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
795 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
796 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
798 // Uncomment this to get some serious before/after printing of the
799 // Sparc safepoint-blob frame structure.
800 /*
801 intptr_t* sp = thread->last_Java_sp();
802 intptr_t stack_copy[150];
803 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
804 bool was_oops[150];
805 for( int i=0; i<150; i++ )
806 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
807 */
809 if (ShowSafepointMsgs) {
810 tty->print("handle_polling_page_exception: ");
811 }
813 if (PrintSafepointStatistics) {
814 inc_page_trap_count();
815 }
817 ThreadSafepointState* state = thread->safepoint_state();
819 state->handle_polling_page_exception();
820 // print_me(sp,stack_copy,was_oops);
821 }
824 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
825 if (!timeout_error_printed) {
826 timeout_error_printed = true;
827 // Print out the thread infor which didn't reach the safepoint for debugging
828 // purposes (useful when there are lots of threads in the debugger).
829 tty->print_cr("");
830 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
831 if (reason == _spinning_timeout) {
832 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
833 } else if (reason == _blocking_timeout) {
834 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
835 }
837 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
838 ThreadSafepointState *cur_state;
839 ResourceMark rm;
840 for(JavaThread *cur_thread = Threads::first(); cur_thread;
841 cur_thread = cur_thread->next()) {
842 cur_state = cur_thread->safepoint_state();
844 if (cur_thread->thread_state() != _thread_blocked &&
845 ((reason == _spinning_timeout && cur_state->is_running()) ||
846 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
847 tty->print("# ");
848 cur_thread->print();
849 tty->print_cr("");
850 }
851 }
852 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
853 }
855 // To debug the long safepoint, specify both DieOnSafepointTimeout &
856 // ShowMessageBoxOnError.
857 if (DieOnSafepointTimeout) {
858 char msg[1024];
859 VM_Operation *op = VMThread::vm_operation();
860 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
861 SafepointTimeoutDelay,
862 op != NULL ? op->name() : "no vm operation");
863 fatal(msg);
864 }
865 }
868 // -------------------------------------------------------------------------------------------------------
869 // Implementation of ThreadSafepointState
871 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
872 _thread = thread;
873 _type = _running;
874 _has_called_back = false;
875 _at_poll_safepoint = false;
876 }
878 void ThreadSafepointState::create(JavaThread *thread) {
879 ThreadSafepointState *state = new ThreadSafepointState(thread);
880 thread->set_safepoint_state(state);
881 }
883 void ThreadSafepointState::destroy(JavaThread *thread) {
884 if (thread->safepoint_state()) {
885 delete(thread->safepoint_state());
886 thread->set_safepoint_state(NULL);
887 }
888 }
890 void ThreadSafepointState::examine_state_of_thread() {
891 assert(is_running(), "better be running or just have hit safepoint poll");
893 JavaThreadState state = _thread->thread_state();
895 // Save the state at the start of safepoint processing.
896 _orig_thread_state = state;
898 // Check for a thread that is suspended. Note that thread resume tries
899 // to grab the Threads_lock which we own here, so a thread cannot be
900 // resumed during safepoint synchronization.
902 // We check to see if this thread is suspended without locking to
903 // avoid deadlocking with a third thread that is waiting for this
904 // thread to be suspended. The third thread can notice the safepoint
905 // that we're trying to start at the beginning of its SR_lock->wait()
906 // call. If that happens, then the third thread will block on the
907 // safepoint while still holding the underlying SR_lock. We won't be
908 // able to get the SR_lock and we'll deadlock.
909 //
910 // We don't need to grab the SR_lock here for two reasons:
911 // 1) The suspend flags are both volatile and are set with an
912 // Atomic::cmpxchg() call so we should see the suspended
913 // state right away.
914 // 2) We're being called from the safepoint polling loop; if
915 // we don't see the suspended state on this iteration, then
916 // we'll come around again.
917 //
918 bool is_suspended = _thread->is_ext_suspended();
919 if (is_suspended) {
920 roll_forward(_at_safepoint);
921 return;
922 }
924 // Some JavaThread states have an initial safepoint state of
925 // running, but are actually at a safepoint. We will happily
926 // agree and update the safepoint state here.
927 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
928 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
929 roll_forward(_at_safepoint);
930 return;
931 }
933 if (state == _thread_in_vm) {
934 roll_forward(_call_back);
935 return;
936 }
938 // All other thread states will continue to run until they
939 // transition and self-block in state _blocked
940 // Safepoint polling in compiled code causes the Java threads to do the same.
941 // Note: new threads may require a malloc so they must be allowed to finish
943 assert(is_running(), "examine_state_of_thread on non-running thread");
944 return;
945 }
947 // Returns true is thread could not be rolled forward at present position.
948 void ThreadSafepointState::roll_forward(suspend_type type) {
949 _type = type;
951 switch(_type) {
952 case _at_safepoint:
953 SafepointSynchronize::signal_thread_at_safepoint();
954 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
955 if (_thread->in_critical()) {
956 // Notice that this thread is in a critical section
957 SafepointSynchronize::increment_jni_active_count();
958 }
959 break;
961 case _call_back:
962 set_has_called_back(false);
963 break;
965 case _running:
966 default:
967 ShouldNotReachHere();
968 }
969 }
971 void ThreadSafepointState::restart() {
972 switch(type()) {
973 case _at_safepoint:
974 case _call_back:
975 break;
977 case _running:
978 default:
979 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
980 _thread, _type);
981 _thread->print();
982 ShouldNotReachHere();
983 }
984 _type = _running;
985 set_has_called_back(false);
986 }
989 void ThreadSafepointState::print_on(outputStream *st) const {
990 const char *s;
992 switch(_type) {
993 case _running : s = "_running"; break;
994 case _at_safepoint : s = "_at_safepoint"; break;
995 case _call_back : s = "_call_back"; break;
996 default:
997 ShouldNotReachHere();
998 }
1000 st->print_cr("Thread: " INTPTR_FORMAT
1001 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1002 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1003 _at_poll_safepoint);
1005 _thread->print_thread_state_on(st);
1006 }
1009 // ---------------------------------------------------------------------------------------------------------------------
1011 // Block the thread at the safepoint poll or poll return.
1012 void ThreadSafepointState::handle_polling_page_exception() {
1014 // Check state. block() will set thread state to thread_in_vm which will
1015 // cause the safepoint state _type to become _call_back.
1016 assert(type() == ThreadSafepointState::_running,
1017 "polling page exception on thread not running state");
1019 // Step 1: Find the nmethod from the return address
1020 if (ShowSafepointMsgs && Verbose) {
1021 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1022 }
1023 address real_return_addr = thread()->saved_exception_pc();
1025 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1026 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1027 nmethod* nm = (nmethod*)cb;
1029 // Find frame of caller
1030 frame stub_fr = thread()->last_frame();
1031 CodeBlob* stub_cb = stub_fr.cb();
1032 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1033 RegisterMap map(thread(), true);
1034 frame caller_fr = stub_fr.sender(&map);
1036 // Should only be poll_return or poll
1037 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1039 // This is a poll immediately before a return. The exception handling code
1040 // has already had the effect of causing the return to occur, so the execution
1041 // will continue immediately after the call. In addition, the oopmap at the
1042 // return point does not mark the return value as an oop (if it is), so
1043 // it needs a handle here to be updated.
1044 if( nm->is_at_poll_return(real_return_addr) ) {
1045 // See if return type is an oop.
1046 bool return_oop = nm->method()->is_returning_oop();
1047 Handle return_value;
1048 if (return_oop) {
1049 // The oop result has been saved on the stack together with all
1050 // the other registers. In order to preserve it over GCs we need
1051 // to keep it in a handle.
1052 oop result = caller_fr.saved_oop_result(&map);
1053 assert(result == NULL || result->is_oop(), "must be oop");
1054 return_value = Handle(thread(), result);
1055 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1056 }
1058 // Block the thread
1059 SafepointSynchronize::block(thread());
1061 // restore oop result, if any
1062 if (return_oop) {
1063 caller_fr.set_saved_oop_result(&map, return_value());
1064 }
1065 }
1067 // This is a safepoint poll. Verify the return address and block.
1068 else {
1069 set_at_poll_safepoint(true);
1071 // verify the blob built the "return address" correctly
1072 assert(real_return_addr == caller_fr.pc(), "must match");
1074 // Block the thread
1075 SafepointSynchronize::block(thread());
1076 set_at_poll_safepoint(false);
1078 // If we have a pending async exception deoptimize the frame
1079 // as otherwise we may never deliver it.
1080 if (thread()->has_async_condition()) {
1081 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1082 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1083 }
1085 // If an exception has been installed we must check for a pending deoptimization
1086 // Deoptimize frame if exception has been thrown.
1088 if (thread()->has_pending_exception() ) {
1089 RegisterMap map(thread(), true);
1090 frame caller_fr = stub_fr.sender(&map);
1091 if (caller_fr.is_deoptimized_frame()) {
1092 // The exception patch will destroy registers that are still
1093 // live and will be needed during deoptimization. Defer the
1094 // Async exception should have defered the exception until the
1095 // next safepoint which will be detected when we get into
1096 // the interpreter so if we have an exception now things
1097 // are messed up.
1099 fatal("Exception installed and deoptimization is pending");
1100 }
1101 }
1102 }
1103 }
1106 //
1107 // Statistics & Instrumentations
1108 //
1109 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1110 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1111 int SafepointSynchronize::_cur_stat_index = 0;
1112 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1113 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1114 jlong SafepointSynchronize::_max_sync_time = 0;
1115 jlong SafepointSynchronize::_max_vmop_time = 0;
1116 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1118 static jlong cleanup_end_time = 0;
1119 static bool need_to_track_page_armed_status = false;
1120 static bool init_done = false;
1122 // Helper method to print the header.
1123 static void print_header() {
1124 tty->print(" vmop "
1125 "[threads: total initially_running wait_to_block] ");
1126 tty->print("[time: spin block sync cleanup vmop] ");
1128 // no page armed status printed out if it is always armed.
1129 if (need_to_track_page_armed_status) {
1130 tty->print("page_armed ");
1131 }
1133 tty->print_cr("page_trap_count");
1134 }
1136 void SafepointSynchronize::deferred_initialize_stat() {
1137 if (init_done) return;
1139 if (PrintSafepointStatisticsCount <= 0) {
1140 fatal("Wrong PrintSafepointStatisticsCount");
1141 }
1143 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1144 // be printed right away, in which case, _safepoint_stats will regress to
1145 // a single element array. Otherwise, it is a circular ring buffer with default
1146 // size of PrintSafepointStatisticsCount.
1147 int stats_array_size;
1148 if (PrintSafepointStatisticsTimeout > 0) {
1149 stats_array_size = 1;
1150 PrintSafepointStatistics = true;
1151 } else {
1152 stats_array_size = PrintSafepointStatisticsCount;
1153 }
1154 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1155 * sizeof(SafepointStats), mtInternal);
1156 guarantee(_safepoint_stats != NULL,
1157 "not enough memory for safepoint instrumentation data");
1159 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1160 need_to_track_page_armed_status = true;
1161 }
1162 init_done = true;
1163 }
1165 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1166 assert(init_done, "safepoint statistics array hasn't been initialized");
1167 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1169 spstat->_time_stamp = _ts_of_current_safepoint;
1171 VM_Operation *op = VMThread::vm_operation();
1172 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1173 if (op != NULL) {
1174 _safepoint_reasons[spstat->_vmop_type]++;
1175 }
1177 spstat->_nof_total_threads = nof_threads;
1178 spstat->_nof_initial_running_threads = nof_running;
1179 spstat->_nof_threads_hit_page_trap = 0;
1181 // Records the start time of spinning. The real time spent on spinning
1182 // will be adjusted when spin is done. Same trick is applied for time
1183 // spent on waiting for threads to block.
1184 if (nof_running != 0) {
1185 spstat->_time_to_spin = os::javaTimeNanos();
1186 } else {
1187 spstat->_time_to_spin = 0;
1188 }
1189 }
1191 void SafepointSynchronize::update_statistics_on_spin_end() {
1192 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1194 jlong cur_time = os::javaTimeNanos();
1196 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1197 if (spstat->_nof_initial_running_threads != 0) {
1198 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1199 }
1201 if (need_to_track_page_armed_status) {
1202 spstat->_page_armed = (PageArmed == 1);
1203 }
1205 // Records the start time of waiting for to block. Updated when block is done.
1206 if (_waiting_to_block != 0) {
1207 spstat->_time_to_wait_to_block = cur_time;
1208 } else {
1209 spstat->_time_to_wait_to_block = 0;
1210 }
1211 }
1213 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1214 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1216 if (spstat->_nof_threads_wait_to_block != 0) {
1217 spstat->_time_to_wait_to_block = end_time -
1218 spstat->_time_to_wait_to_block;
1219 }
1221 // Records the end time of sync which will be used to calculate the total
1222 // vm operation time. Again, the real time spending in syncing will be deducted
1223 // from the start of the sync time later when end_statistics is called.
1224 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1225 if (spstat->_time_to_sync > _max_sync_time) {
1226 _max_sync_time = spstat->_time_to_sync;
1227 }
1229 spstat->_time_to_do_cleanups = end_time;
1230 }
1232 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1233 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1235 // Record how long spent in cleanup tasks.
1236 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1238 cleanup_end_time = end_time;
1239 }
1241 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1242 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1244 // Update the vm operation time.
1245 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1246 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1247 _max_vmop_time = spstat->_time_to_exec_vmop;
1248 }
1249 // Only the sync time longer than the specified
1250 // PrintSafepointStatisticsTimeout will be printed out right away.
1251 // By default, it is -1 meaning all samples will be put into the list.
1252 if ( PrintSafepointStatisticsTimeout > 0) {
1253 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1254 print_statistics();
1255 }
1256 } else {
1257 // The safepoint statistics will be printed out when the _safepoin_stats
1258 // array fills up.
1259 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1260 print_statistics();
1261 _cur_stat_index = 0;
1262 } else {
1263 _cur_stat_index++;
1264 }
1265 }
1266 }
1268 void SafepointSynchronize::print_statistics() {
1269 SafepointStats* sstats = _safepoint_stats;
1271 for (int index = 0; index <= _cur_stat_index; index++) {
1272 if (index % 30 == 0) {
1273 print_header();
1274 }
1275 sstats = &_safepoint_stats[index];
1276 tty->print("%.3f: ", sstats->_time_stamp);
1277 tty->print("%-26s ["
1278 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1279 " ] ",
1280 sstats->_vmop_type == -1 ? "no vm operation" :
1281 VM_Operation::name(sstats->_vmop_type),
1282 sstats->_nof_total_threads,
1283 sstats->_nof_initial_running_threads,
1284 sstats->_nof_threads_wait_to_block);
1285 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1286 tty->print(" ["
1287 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1288 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1289 INT64_FORMAT_W(6)" ] ",
1290 sstats->_time_to_spin / MICROUNITS,
1291 sstats->_time_to_wait_to_block / MICROUNITS,
1292 sstats->_time_to_sync / MICROUNITS,
1293 sstats->_time_to_do_cleanups / MICROUNITS,
1294 sstats->_time_to_exec_vmop / MICROUNITS);
1296 if (need_to_track_page_armed_status) {
1297 tty->print(INT32_FORMAT" ", sstats->_page_armed);
1298 }
1299 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
1300 }
1301 }
1303 // This method will be called when VM exits. It will first call
1304 // print_statistics to print out the rest of the sampling. Then
1305 // it tries to summarize the sampling.
1306 void SafepointSynchronize::print_stat_on_exit() {
1307 if (_safepoint_stats == NULL) return;
1309 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1311 // During VM exit, end_statistics may not get called and in that
1312 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1313 // don't print it out.
1314 // Approximate the vm op time.
1315 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1316 os::javaTimeNanos() - cleanup_end_time;
1318 if ( PrintSafepointStatisticsTimeout < 0 ||
1319 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1320 print_statistics();
1321 }
1322 tty->print_cr("");
1324 // Print out polling page sampling status.
1325 if (!need_to_track_page_armed_status) {
1326 if (UseCompilerSafepoints) {
1327 tty->print_cr("Polling page always armed");
1328 }
1329 } else {
1330 tty->print_cr("Defer polling page loop count = %d\n",
1331 DeferPollingPageLoopCount);
1332 }
1334 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1335 if (_safepoint_reasons[index] != 0) {
1336 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1337 _safepoint_reasons[index]);
1338 }
1339 }
1341 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1342 _coalesced_vmop_count);
1343 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
1344 _max_sync_time / MICROUNITS);
1345 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1346 INT64_FORMAT_W(5)" ms",
1347 _max_vmop_time / MICROUNITS);
1348 }
1350 // ------------------------------------------------------------------------------------------------
1351 // Non-product code
1353 #ifndef PRODUCT
1355 void SafepointSynchronize::print_state() {
1356 if (_state == _not_synchronized) {
1357 tty->print_cr("not synchronized");
1358 } else if (_state == _synchronizing || _state == _synchronized) {
1359 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1360 "synchronized");
1362 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1363 cur->safepoint_state()->print();
1364 }
1365 }
1366 }
1368 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1369 if (ShowSafepointMsgs) {
1370 va_list ap;
1371 va_start(ap, format);
1372 tty->vprint_cr(format, ap);
1373 va_end(ap);
1374 }
1375 }
1377 #endif // !PRODUCT