1 /*
2 * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/stringTable.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/gcLocker.inline.hpp"
36 #include "memory/resourceArea.hpp"
37 #include "memory/universe.inline.hpp"
38 #include "oops/oop.inline.hpp"
39 #include "oops/symbol.hpp"
40 #include "runtime/atomic.inline.hpp"
41 #include "runtime/compilationPolicy.hpp"
42 #include "runtime/deoptimization.hpp"
43 #include "runtime/frame.inline.hpp"
44 #include "runtime/interfaceSupport.hpp"
45 #include "runtime/mutexLocker.hpp"
46 #include "runtime/orderAccess.inline.hpp"
47 #include "runtime/osThread.hpp"
48 #include "runtime/safepoint.hpp"
49 #include "runtime/signature.hpp"
50 #include "runtime/stubCodeGenerator.hpp"
51 #include "runtime/stubRoutines.hpp"
52 #include "runtime/sweeper.hpp"
53 #include "runtime/synchronizer.hpp"
54 #include "runtime/thread.inline.hpp"
55 #include "services/memTracker.hpp"
56 #include "services/runtimeService.hpp"
57 #include "utilities/events.hpp"
58 #include "utilities/macros.hpp"
59 #ifdef TARGET_ARCH_x86
60 # include "nativeInst_x86.hpp"
61 # include "vmreg_x86.inline.hpp"
62 #endif
63 #ifdef TARGET_ARCH_sparc
64 # include "nativeInst_sparc.hpp"
65 # include "vmreg_sparc.inline.hpp"
66 #endif
67 #ifdef TARGET_ARCH_zero
68 # include "nativeInst_zero.hpp"
69 # include "vmreg_zero.inline.hpp"
70 #endif
71 #ifdef TARGET_ARCH_arm
72 # include "nativeInst_arm.hpp"
73 # include "vmreg_arm.inline.hpp"
74 #endif
75 #ifdef TARGET_ARCH_ppc
76 # include "nativeInst_ppc.hpp"
77 # include "vmreg_ppc.inline.hpp"
78 #endif
79 #if INCLUDE_ALL_GCS
80 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
81 #include "gc_implementation/shared/suspendibleThreadSet.hpp"
82 #endif // INCLUDE_ALL_GCS
83 #ifdef COMPILER1
84 #include "c1/c1_globals.hpp"
85 #endif
86
87 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
88
89 // --------------------------------------------------------------------------------------------------
90 // Implementation of Safepoint begin/end
91
92 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
93 volatile int SafepointSynchronize::_waiting_to_block = 0;
94 volatile int SafepointSynchronize::_safepoint_counter = 0;
95 int SafepointSynchronize::_current_jni_active_count = 0;
96 long SafepointSynchronize::_end_of_last_safepoint = 0;
97 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
98 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
99 static bool timeout_error_printed = false;
100
101 // Roll all threads forward to a safepoint and suspend them all
102 void SafepointSynchronize::begin() {
103
104 Thread* myThread = Thread::current();
105 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
106
107 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
108 _safepoint_begin_time = os::javaTimeNanos();
109 _ts_of_current_safepoint = tty->time_stamp().seconds();
110 }
111
112 #if INCLUDE_ALL_GCS
113 if (UseConcMarkSweepGC) {
114 // In the future we should investigate whether CMS can use the
115 // more-general mechanism below. DLD (01/05).
116 ConcurrentMarkSweepThread::synchronize(false);
117 } else if (UseG1GC) {
118 SuspendibleThreadSet::synchronize();
119 }
120 #endif // INCLUDE_ALL_GCS
121
122 // By getting the Threads_lock, we assure that no threads are about to start or
123 // exit. It is released again in SafepointSynchronize::end().
124 Threads_lock->lock();
125
126 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
127
128 int nof_threads = Threads::number_of_threads();
129
130 if (TraceSafepoint) {
131 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
132 }
133
134 RuntimeService::record_safepoint_begin();
135
136 MutexLocker mu(Safepoint_lock);
137
138 // Reset the count of active JNI critical threads
139 _current_jni_active_count = 0;
140
141 // Set number of threads to wait for, before we initiate the callbacks
142 _waiting_to_block = nof_threads;
143 TryingToBlock = 0 ;
144 int still_running = nof_threads;
145
146 // Save the starting time, so that it can be compared to see if this has taken
147 // too long to complete.
148 jlong safepoint_limit_time;
149 timeout_error_printed = false;
150
151 // PrintSafepointStatisticsTimeout can be specified separately. When
152 // specified, PrintSafepointStatistics will be set to true in
153 // deferred_initialize_stat method. The initialization has to be done
154 // early enough to avoid any races. See bug 6880029 for details.
155 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
156 deferred_initialize_stat();
157 }
158
159 // Begin the process of bringing the system to a safepoint.
160 // Java threads can be in several different states and are
161 // stopped by different mechanisms:
162 //
163 // 1. Running interpreted
164 // The interpreter dispatch table is changed to force it to
165 // check for a safepoint condition between bytecodes.
166 // 2. Running in native code
167 // When returning from the native code, a Java thread must check
168 // the safepoint _state to see if we must block. If the
169 // VM thread sees a Java thread in native, it does
170 // not wait for this thread to block. The order of the memory
171 // writes and reads of both the safepoint state and the Java
172 // threads state is critical. In order to guarantee that the
173 // memory writes are serialized with respect to each other,
174 // the VM thread issues a memory barrier instruction
175 // (on MP systems). In order to avoid the overhead of issuing
176 // a memory barrier for each Java thread making native calls, each Java
177 // thread performs a write to a single memory page after changing
178 // the thread state. The VM thread performs a sequence of
179 // mprotect OS calls which forces all previous writes from all
180 // Java threads to be serialized. This is done in the
181 // os::serialize_thread_states() call. This has proven to be
182 // much more efficient than executing a membar instruction
183 // on every call to native code.
184 // 3. Running compiled Code
185 // Compiled code reads a global (Safepoint Polling) page that
186 // is set to fault if we are trying to get to a safepoint.
187 // 4. Blocked
188 // A thread which is blocked will not be allowed to return from the
189 // block condition until the safepoint operation is complete.
190 // 5. In VM or Transitioning between states
191 // If a Java thread is currently running in the VM or transitioning
192 // between states, the safepointing code will wait for the thread to
193 // block itself when it attempts transitions to a new state.
194 //
195 _state = _synchronizing;
196 OrderAccess::fence();
197
198 // Flush all thread states to memory
199 if (!UseMembar) {
200 os::serialize_thread_states();
201 }
202
203 // Make interpreter safepoint aware
204 Interpreter::notice_safepoints();
205
206 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
207 // Make polling safepoint aware
208 guarantee (PageArmed == 0, "invariant") ;
209 PageArmed = 1 ;
210 os::make_polling_page_unreadable();
211 }
212
213 // Consider using active_processor_count() ... but that call is expensive.
214 int ncpus = os::processor_count() ;
215
216 #ifdef ASSERT
217 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
218 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
219 // Clear the visited flag to ensure that the critical counts are collected properly.
220 cur->set_visited_for_critical_count(false);
221 }
222 #endif // ASSERT
223
224 if (SafepointTimeout)
225 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
226
227 // Iterate through all threads until it have been determined how to stop them all at a safepoint
228 unsigned int iterations = 0;
229 int steps = 0 ;
230 while(still_running > 0) {
231 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
232 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
233 ThreadSafepointState *cur_state = cur->safepoint_state();
234 if (cur_state->is_running()) {
235 cur_state->examine_state_of_thread();
236 if (!cur_state->is_running()) {
237 still_running--;
238 // consider adjusting steps downward:
239 // steps = 0
240 // steps -= NNN
241 // steps >>= 1
242 // steps = MIN(steps, 2000-100)
243 // if (iterations != 0) steps -= NNN
244 }
245 if (TraceSafepoint && Verbose) cur_state->print();
246 }
247 }
248
249 if (PrintSafepointStatistics && iterations == 0) {
250 begin_statistics(nof_threads, still_running);
251 }
252
253 if (still_running > 0) {
254 // Check for if it takes to long
255 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
256 print_safepoint_timeout(_spinning_timeout);
257 }
258
259 // Spin to avoid context switching.
260 // There's a tension between allowing the mutators to run (and rendezvous)
261 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
262 // a mutator might otherwise use profitably to reach a safepoint. Excessive
263 // spinning by the VM thread on a saturated system can increase rendezvous latency.
264 // Blocking or yielding incur their own penalties in the form of context switching
265 // and the resultant loss of $ residency.
266 //
267 // Further complicating matters is that yield() does not work as naively expected
268 // on many platforms -- yield() does not guarantee that any other ready threads
269 // will run. As such we revert yield_all() after some number of iterations.
270 // Yield_all() is implemented as a short unconditional sleep on some platforms.
271 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
272 // can actually increase the time it takes the VM thread to detect that a system-wide
273 // stop-the-world safepoint has been reached. In a pathological scenario such as that
274 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
275 // In that case the mutators will be stalled waiting for the safepoint to complete and the
276 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
277 // will eventually wake up and detect that all mutators are safe, at which point
278 // we'll again make progress.
279 //
280 // Beware too that that the VMThread typically runs at elevated priority.
281 // Its default priority is higher than the default mutator priority.
282 // Obviously, this complicates spinning.
283 //
284 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
285 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
286 //
287 // See the comments in synchronizer.cpp for additional remarks on spinning.
288 //
289 // In the future we might:
290 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
291 // This is tricky as the path used by a thread exiting the JVM (say on
292 // on JNI call-out) simply stores into its state field. The burden
293 // is placed on the VM thread, which must poll (spin).
294 // 2. Find something useful to do while spinning. If the safepoint is GC-related
295 // we might aggressively scan the stacks of threads that are already safe.
296 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
297 // If all the mutators are ONPROC there's no reason to sleep or yield.
298 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
299 // 5. Check system saturation. If the system is not fully saturated then
300 // simply spin and avoid sleep/yield.
301 // 6. As still-running mutators rendezvous they could unpark the sleeping
302 // VMthread. This works well for still-running mutators that become
303 // safe. The VMthread must still poll for mutators that call-out.
304 // 7. Drive the policy on time-since-begin instead of iterations.
305 // 8. Consider making the spin duration a function of the # of CPUs:
306 // Spin = (((ncpus-1) * M) + K) + F(still_running)
307 // Alternately, instead of counting iterations of the outer loop
308 // we could count the # of threads visited in the inner loop, above.
309 // 9. On windows consider using the return value from SwitchThreadTo()
310 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
311
312 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
313 guarantee (PageArmed == 0, "invariant") ;
314 PageArmed = 1 ;
315 os::make_polling_page_unreadable();
316 }
317
318 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
319 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
320 ++steps ;
321 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
322 SpinPause() ; // MP-Polite spin
323 } else
324 if (steps < DeferThrSuspendLoopCount) {
325 os::NakedYield() ;
326 } else {
327 os::yield_all() ;
328 // Alternately, the VM thread could transiently depress its scheduling priority or
329 // transiently increase the priority of the tardy mutator(s).
330 }
331
332 iterations ++ ;
333 }
334 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
335 }
336 assert(still_running == 0, "sanity check");
337
338 if (PrintSafepointStatistics) {
339 update_statistics_on_spin_end();
340 }
341
342 // wait until all threads are stopped
343 while (_waiting_to_block > 0) {
344 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
345 if (!SafepointTimeout || timeout_error_printed) {
346 Safepoint_lock->wait(true); // true, means with no safepoint checks
347 } else {
348 // Compute remaining time
349 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
350
351 // If there is no remaining time, then there is an error
352 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
353 print_safepoint_timeout(_blocking_timeout);
354 }
355 }
356 }
357 assert(_waiting_to_block == 0, "sanity check");
358
359 #ifndef PRODUCT
360 if (SafepointTimeout) {
361 jlong current_time = os::javaTimeNanos();
362 if (safepoint_limit_time < current_time) {
363 tty->print_cr("# SafepointSynchronize: Finished after "
364 INT64_FORMAT_W(6) " ms",
365 ((current_time - safepoint_limit_time) / MICROUNITS +
366 SafepointTimeoutDelay));
367 }
368 }
369 #endif
370
371 assert((_safepoint_counter & 0x1) == 0, "must be even");
372 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
373 _safepoint_counter ++;
374
375 // Record state
376 _state = _synchronized;
377
378 OrderAccess::fence();
379
380 #ifdef ASSERT
381 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
382 // make sure all the threads were visited
383 assert(cur->was_visited_for_critical_count(), "missed a thread");
384 }
385 #endif // ASSERT
386
387 // Update the count of active JNI critical regions
388 GC_locker::set_jni_lock_count(_current_jni_active_count);
389
390 if (TraceSafepoint) {
391 VM_Operation *op = VMThread::vm_operation();
392 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
393 }
394
395 RuntimeService::record_safepoint_synchronized();
396 if (PrintSafepointStatistics) {
397 update_statistics_on_sync_end(os::javaTimeNanos());
398 }
399
400 // Call stuff that needs to be run when a safepoint is just about to be completed
401 do_cleanup_tasks();
402
403 if (PrintSafepointStatistics) {
404 // Record how much time spend on the above cleanup tasks
405 update_statistics_on_cleanup_end(os::javaTimeNanos());
406 }
407 }
408
409 // Wake up all threads, so they are ready to resume execution after the safepoint
410 // operation has been carried out
411 void SafepointSynchronize::end() {
412
413 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
414 assert((_safepoint_counter & 0x1) == 1, "must be odd");
415 _safepoint_counter ++;
416 // memory fence isn't required here since an odd _safepoint_counter
417 // value can do no harm and a fence is issued below anyway.
418
419 DEBUG_ONLY(Thread* myThread = Thread::current();)
420 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
421
422 if (PrintSafepointStatistics) {
423 end_statistics(os::javaTimeNanos());
424 }
425
426 #ifdef ASSERT
427 // A pending_exception cannot be installed during a safepoint. The threads
428 // may install an async exception after they come back from a safepoint into
429 // pending_exception after they unblock. But that should happen later.
430 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
431 assert (!(cur->has_pending_exception() &&
432 cur->safepoint_state()->is_at_poll_safepoint()),
433 "safepoint installed a pending exception");
434 }
435 #endif // ASSERT
436
437 if (PageArmed) {
438 // Make polling safepoint aware
439 os::make_polling_page_readable();
440 PageArmed = 0 ;
441 }
442
443 // Remove safepoint check from interpreter
444 Interpreter::ignore_safepoints();
445
446 {
447 MutexLocker mu(Safepoint_lock);
448
449 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
450
451 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
452 // when they get restarted.
453 _state = _not_synchronized;
454 OrderAccess::fence();
455
456 if (TraceSafepoint) {
457 tty->print_cr("Leaving safepoint region");
458 }
459
460 // Start suspended threads
461 for(JavaThread *current = Threads::first(); current; current = current->next()) {
462 // A problem occurring on Solaris is when attempting to restart threads
463 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
464 // to the next one (since it has been running the longest). We then have
465 // to wait for a cpu to become available before we can continue restarting
466 // threads.
467 // FIXME: This causes the performance of the VM to degrade when active and with
468 // large numbers of threads. Apparently this is due to the synchronous nature
469 // of suspending threads.
470 //
471 // TODO-FIXME: the comments above are vestigial and no longer apply.
472 // Furthermore, using solaris' schedctl in this particular context confers no benefit
473 if (VMThreadHintNoPreempt) {
474 os::hint_no_preempt();
475 }
476 ThreadSafepointState* cur_state = current->safepoint_state();
477 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
478 cur_state->restart();
479 assert(cur_state->is_running(), "safepoint state has not been reset");
480 }
481
482 RuntimeService::record_safepoint_end();
483
484 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
485 // blocked in signal_thread_blocked
486 Threads_lock->unlock();
487
488 }
489 #if INCLUDE_ALL_GCS
490 // If there are any concurrent GC threads resume them.
491 if (UseConcMarkSweepGC) {
492 ConcurrentMarkSweepThread::desynchronize(false);
493 } else if (UseG1GC) {
494 SuspendibleThreadSet::desynchronize();
495 }
496 #endif // INCLUDE_ALL_GCS
497 // record this time so VMThread can keep track how much time has elapsed
498 // since last safepoint.
499 _end_of_last_safepoint = os::javaTimeMillis();
500 }
501
502 bool SafepointSynchronize::is_cleanup_needed() {
503 // Need a safepoint if some inline cache buffers is non-empty
504 if (!InlineCacheBuffer::is_empty()) return true;
505 return false;
506 }
507
508
509
510 // Various cleaning tasks that should be done periodically at safepoints
511 void SafepointSynchronize::do_cleanup_tasks() {
512 {
513 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
514 ObjectSynchronizer::deflate_idle_monitors();
515 }
516
517 {
518 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
519 InlineCacheBuffer::update_inline_caches();
520 }
521 {
522 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
523 CompilationPolicy::policy()->do_safepoint_work();
524 }
525
526 {
527 TraceTime t4("mark nmethods", TraceSafepointCleanupTime);
528 NMethodSweeper::mark_active_nmethods();
529 }
530
531 if (SymbolTable::needs_rehashing()) {
532 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
533 SymbolTable::rehash_table();
534 }
535
536 if (StringTable::needs_rehashing()) {
537 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
538 StringTable::rehash_table();
539 }
540
541 // rotate log files?
542 if (UseGCLogFileRotation) {
543 gclog_or_tty->rotate_log(false);
544 }
545
546 {
547 // CMS delays purging the CLDG until the beginning of the next safepoint and to
548 // make sure concurrent sweep is done
549 TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime);
550 ClassLoaderDataGraph::purge_if_needed();
551 }
552
553 if (MemTracker::is_on()) {
554 MemTracker::sync();
555 }
556 }
557
558
559 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
560 switch(state) {
561 case _thread_in_native:
562 // native threads are safe if they have no java stack or have walkable stack
563 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
564
565 // blocked threads should have already have walkable stack
566 case _thread_blocked:
567 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
568 return true;
569
570 default:
571 return false;
572 }
573 }
574
575
576 // See if the thread is running inside a lazy critical native and
577 // update the thread critical count if so. Also set a suspend flag to
578 // cause the native wrapper to return into the JVM to do the unlock
579 // once the native finishes.
580 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
581 if (state == _thread_in_native &&
582 thread->has_last_Java_frame() &&
583 thread->frame_anchor()->walkable()) {
584 // This thread might be in a critical native nmethod so look at
585 // the top of the stack and increment the critical count if it
586 // is.
587 frame wrapper_frame = thread->last_frame();
588 CodeBlob* stub_cb = wrapper_frame.cb();
589 if (stub_cb != NULL &&
590 stub_cb->is_nmethod() &&
591 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
592 // A thread could potentially be in a critical native across
593 // more than one safepoint, so only update the critical state on
594 // the first one. When it returns it will perform the unlock.
595 if (!thread->do_critical_native_unlock()) {
596 #ifdef ASSERT
597 if (!thread->in_critical()) {
598 GC_locker::increment_debug_jni_lock_count();
599 }
600 #endif
601 thread->enter_critical();
602 // Make sure the native wrapper calls back on return to
603 // perform the needed critical unlock.
604 thread->set_critical_native_unlock();
605 }
606 }
607 }
608 }
609
610
611
612 // -------------------------------------------------------------------------------------------------------
613 // Implementation of Safepoint callback point
614
615 void SafepointSynchronize::block(JavaThread *thread) {
616 assert(thread != NULL, "thread must be set");
617 assert(thread->is_Java_thread(), "not a Java thread");
618
619 // Threads shouldn't block if they are in the middle of printing, but...
620 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
621
622 // Only bail from the block() call if the thread is gone from the
623 // thread list; starting to exit should still block.
624 if (thread->is_terminated()) {
625 // block current thread if we come here from native code when VM is gone
626 thread->block_if_vm_exited();
627
628 // otherwise do nothing
629 return;
630 }
631
632 JavaThreadState state = thread->thread_state();
633 thread->frame_anchor()->make_walkable(thread);
634
635 // Check that we have a valid thread_state at this point
636 switch(state) {
637 case _thread_in_vm_trans:
638 case _thread_in_Java: // From compiled code
639
640 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
641 // we pretend we are still in the VM.
642 thread->set_thread_state(_thread_in_vm);
643
644 if (is_synchronizing()) {
645 Atomic::inc (&TryingToBlock) ;
646 }
647
648 // We will always be holding the Safepoint_lock when we are examine the state
649 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
650 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
651 Safepoint_lock->lock_without_safepoint_check();
652 if (is_synchronizing()) {
653 // Decrement the number of threads to wait for and signal vm thread
654 assert(_waiting_to_block > 0, "sanity check");
655 _waiting_to_block--;
656 thread->safepoint_state()->set_has_called_back(true);
657
658 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
659 if (thread->in_critical()) {
660 // Notice that this thread is in a critical section
661 increment_jni_active_count();
662 }
663
664 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
665 if (_waiting_to_block == 0) {
666 Safepoint_lock->notify_all();
667 }
668 }
669
670 // We transition the thread to state _thread_blocked here, but
671 // we can't do our usual check for external suspension and then
672 // self-suspend after the lock_without_safepoint_check() call
673 // below because we are often called during transitions while
674 // we hold different locks. That would leave us suspended while
675 // holding a resource which results in deadlocks.
676 thread->set_thread_state(_thread_blocked);
677 Safepoint_lock->unlock();
678
679 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
680 // the entire safepoint, the threads will all line up here during the safepoint.
681 Threads_lock->lock_without_safepoint_check();
682 // restore original state. This is important if the thread comes from compiled code, so it
683 // will continue to execute with the _thread_in_Java state.
684 thread->set_thread_state(state);
685 Threads_lock->unlock();
686 break;
687
688 case _thread_in_native_trans:
689 case _thread_blocked_trans:
690 case _thread_new_trans:
691 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
692 thread->print_thread_state();
693 fatal("Deadlock in safepoint code. "
694 "Should have called back to the VM before blocking.");
695 }
696
697 // We transition the thread to state _thread_blocked here, but
698 // we can't do our usual check for external suspension and then
699 // self-suspend after the lock_without_safepoint_check() call
700 // below because we are often called during transitions while
701 // we hold different locks. That would leave us suspended while
702 // holding a resource which results in deadlocks.
703 thread->set_thread_state(_thread_blocked);
704
705 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
706 // the safepoint code might still be waiting for it to block. We need to change the state here,
707 // so it can see that it is at a safepoint.
708
709 // Block until the safepoint operation is completed.
710 Threads_lock->lock_without_safepoint_check();
711
712 // Restore state
713 thread->set_thread_state(state);
714
715 Threads_lock->unlock();
716 break;
717
718 default:
719 fatal(err_msg("Illegal threadstate encountered: %d", state));
720 }
721
722 // Check for pending. async. exceptions or suspends - except if the
723 // thread was blocked inside the VM. has_special_runtime_exit_condition()
724 // is called last since it grabs a lock and we only want to do that when
725 // we must.
726 //
727 // Note: we never deliver an async exception at a polling point as the
728 // compiler may not have an exception handler for it. The polling
729 // code will notice the async and deoptimize and the exception will
730 // be delivered. (Polling at a return point is ok though). Sure is
731 // a lot of bother for a deprecated feature...
732 //
733 // We don't deliver an async exception if the thread state is
734 // _thread_in_native_trans so JNI functions won't be called with
735 // a surprising pending exception. If the thread state is going back to java,
736 // async exception is checked in check_special_condition_for_native_trans().
737
738 if (state != _thread_blocked_trans &&
739 state != _thread_in_vm_trans &&
740 thread->has_special_runtime_exit_condition()) {
741 thread->handle_special_runtime_exit_condition(
742 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
743 }
744 }
745
746 // ------------------------------------------------------------------------------------------------------
747 // Exception handlers
748
749 #ifndef PRODUCT
750
751 #ifdef SPARC
752
753 #ifdef _LP64
754 #define PTR_PAD ""
755 #else
756 #define PTR_PAD " "
757 #endif
758
759 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
760 bool is_oop = newptr ? (cast_to_oop(newptr))->is_oop() : false;
761 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
762 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
763 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
764 }
765
766 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
767 bool is_oop = newptr ? (cast_to_oop(newptr))->is_oop() : false;
768 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
769 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
770 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
771 }
772
773 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
774 #ifdef _LP64
775 tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
776 const int incr = 1; // Increment to skip a long, in units of intptr_t
777 #else
778 tty->print_cr("--------+--address-+------before-----------+-------after----------+");
779 const int incr = 2; // Increment to skip a long, in units of intptr_t
780 #endif
781 tty->print_cr("---SP---|");
782 for( int i=0; i<16; i++ ) {
783 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
784 tty->print_cr("--------|");
785 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
786 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
787 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
788 tty->print_cr("--------|");
789 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;
790 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;
791 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;
792 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;
793 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
794 old_sp += incr; new_sp += incr; was_oops += incr;
795 // Skip the floats
796 tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
797 tty->print_cr("---FP---|");
798 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32;
799 for( int i2=0; i2<16; i2++ ) {
800 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
801 tty->cr();
802 }
803 #endif // SPARC
804 #endif // PRODUCT
805
806
807 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
808 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
809 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
810 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
811
812 // Uncomment this to get some serious before/after printing of the
813 // Sparc safepoint-blob frame structure.
814 /*
815 intptr_t* sp = thread->last_Java_sp();
816 intptr_t stack_copy[150];
817 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
818 bool was_oops[150];
819 for( int i=0; i<150; i++ )
820 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
821 */
822
823 if (ShowSafepointMsgs) {
824 tty->print("handle_polling_page_exception: ");
825 }
826
827 if (PrintSafepointStatistics) {
828 inc_page_trap_count();
829 }
830
831 ThreadSafepointState* state = thread->safepoint_state();
832
833 state->handle_polling_page_exception();
834 // print_me(sp,stack_copy,was_oops);
835 }
836
837
838 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
839 if (!timeout_error_printed) {
840 timeout_error_printed = true;
841 // Print out the thread info which didn't reach the safepoint for debugging
842 // purposes (useful when there are lots of threads in the debugger).
843 tty->cr();
844 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
845 if (reason == _spinning_timeout) {
846 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
847 } else if (reason == _blocking_timeout) {
848 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
849 }
850
851 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
852 ThreadSafepointState *cur_state;
853 ResourceMark rm;
854 for(JavaThread *cur_thread = Threads::first(); cur_thread;
855 cur_thread = cur_thread->next()) {
856 cur_state = cur_thread->safepoint_state();
857
858 if (cur_thread->thread_state() != _thread_blocked &&
859 ((reason == _spinning_timeout && cur_state->is_running()) ||
860 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
861 tty->print("# ");
862 cur_thread->print();
863 tty->cr();
864 }
865 }
866 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
867 }
868
869 // To debug the long safepoint, specify both DieOnSafepointTimeout &
870 // ShowMessageBoxOnError.
871 if (DieOnSafepointTimeout) {
872 char msg[1024];
873 VM_Operation *op = VMThread::vm_operation();
874 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
875 SafepointTimeoutDelay,
876 op != NULL ? op->name() : "no vm operation");
877 fatal(msg);
878 }
879 }
880
881
882 // -------------------------------------------------------------------------------------------------------
883 // Implementation of ThreadSafepointState
884
885 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
886 _thread = thread;
887 _type = _running;
888 _has_called_back = false;
889 _at_poll_safepoint = false;
890 }
891
892 void ThreadSafepointState::create(JavaThread *thread) {
893 ThreadSafepointState *state = new ThreadSafepointState(thread);
894 thread->set_safepoint_state(state);
895 }
896
897 void ThreadSafepointState::destroy(JavaThread *thread) {
898 if (thread->safepoint_state()) {
899 delete(thread->safepoint_state());
900 thread->set_safepoint_state(NULL);
901 }
902 }
903
904 void ThreadSafepointState::examine_state_of_thread() {
905 assert(is_running(), "better be running or just have hit safepoint poll");
906
907 JavaThreadState state = _thread->thread_state();
908
909 // Save the state at the start of safepoint processing.
910 _orig_thread_state = state;
911
912 // Check for a thread that is suspended. Note that thread resume tries
913 // to grab the Threads_lock which we own here, so a thread cannot be
914 // resumed during safepoint synchronization.
915
916 // We check to see if this thread is suspended without locking to
917 // avoid deadlocking with a third thread that is waiting for this
918 // thread to be suspended. The third thread can notice the safepoint
919 // that we're trying to start at the beginning of its SR_lock->wait()
920 // call. If that happens, then the third thread will block on the
921 // safepoint while still holding the underlying SR_lock. We won't be
922 // able to get the SR_lock and we'll deadlock.
923 //
924 // We don't need to grab the SR_lock here for two reasons:
925 // 1) The suspend flags are both volatile and are set with an
926 // Atomic::cmpxchg() call so we should see the suspended
927 // state right away.
928 // 2) We're being called from the safepoint polling loop; if
929 // we don't see the suspended state on this iteration, then
930 // we'll come around again.
931 //
932 bool is_suspended = _thread->is_ext_suspended();
933 if (is_suspended) {
934 roll_forward(_at_safepoint);
935 return;
936 }
937
938 // Some JavaThread states have an initial safepoint state of
939 // running, but are actually at a safepoint. We will happily
940 // agree and update the safepoint state here.
941 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
942 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
943 roll_forward(_at_safepoint);
944 return;
945 }
946
947 if (state == _thread_in_vm) {
948 roll_forward(_call_back);
949 return;
950 }
951
952 // All other thread states will continue to run until they
953 // transition and self-block in state _blocked
954 // Safepoint polling in compiled code causes the Java threads to do the same.
955 // Note: new threads may require a malloc so they must be allowed to finish
956
957 assert(is_running(), "examine_state_of_thread on non-running thread");
958 return;
959 }
960
961 // Returns true is thread could not be rolled forward at present position.
962 void ThreadSafepointState::roll_forward(suspend_type type) {
963 _type = type;
964
965 switch(_type) {
966 case _at_safepoint:
967 SafepointSynchronize::signal_thread_at_safepoint();
968 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
969 if (_thread->in_critical()) {
970 // Notice that this thread is in a critical section
971 SafepointSynchronize::increment_jni_active_count();
972 }
973 break;
974
975 case _call_back:
976 set_has_called_back(false);
977 break;
978
979 case _running:
980 default:
981 ShouldNotReachHere();
982 }
983 }
984
985 void ThreadSafepointState::restart() {
986 switch(type()) {
987 case _at_safepoint:
988 case _call_back:
989 break;
990
991 case _running:
992 default:
993 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
994 _thread, _type);
995 _thread->print();
996 ShouldNotReachHere();
997 }
998 _type = _running;
999 set_has_called_back(false);
1000 }
1001
1002
1003 void ThreadSafepointState::print_on(outputStream *st) const {
1004 const char *s;
1005
1006 switch(_type) {
1007 case _running : s = "_running"; break;
1008 case _at_safepoint : s = "_at_safepoint"; break;
1009 case _call_back : s = "_call_back"; break;
1010 default:
1011 ShouldNotReachHere();
1012 }
1013
1014 st->print_cr("Thread: " INTPTR_FORMAT
1015 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1016 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1017 _at_poll_safepoint);
1018
1019 _thread->print_thread_state_on(st);
1020 }
1021
1022
1023 // ---------------------------------------------------------------------------------------------------------------------
1024
1025 // Block the thread at the safepoint poll or poll return.
1026 void ThreadSafepointState::handle_polling_page_exception() {
1027
1028 // Check state. block() will set thread state to thread_in_vm which will
1029 // cause the safepoint state _type to become _call_back.
1030 assert(type() == ThreadSafepointState::_running,
1031 "polling page exception on thread not running state");
1032
1033 // Step 1: Find the nmethod from the return address
1034 if (ShowSafepointMsgs && Verbose) {
1035 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1036 }
1037 address real_return_addr = thread()->saved_exception_pc();
1038
1039 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1040 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1041 nmethod* nm = (nmethod*)cb;
1042
1043 // Find frame of caller
1044 frame stub_fr = thread()->last_frame();
1045 CodeBlob* stub_cb = stub_fr.cb();
1046 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1047 RegisterMap map(thread(), true);
1048 frame caller_fr = stub_fr.sender(&map);
1049
1050 // Should only be poll_return or poll
1051 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1052
1053 // This is a poll immediately before a return. The exception handling code
1054 // has already had the effect of causing the return to occur, so the execution
1055 // will continue immediately after the call. In addition, the oopmap at the
1056 // return point does not mark the return value as an oop (if it is), so
1057 // it needs a handle here to be updated.
1058 if( nm->is_at_poll_return(real_return_addr) ) {
1059 // See if return type is an oop.
1060 bool return_oop = nm->method()->is_returning_oop();
1061 Handle return_value;
1062 if (return_oop) {
1063 // The oop result has been saved on the stack together with all
1064 // the other registers. In order to preserve it over GCs we need
1065 // to keep it in a handle.
1066 oop result = caller_fr.saved_oop_result(&map);
1067 assert(result == NULL || result->is_oop(), "must be oop");
1068 return_value = Handle(thread(), result);
1069 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1070 }
1071
1072 // Block the thread
1073 SafepointSynchronize::block(thread());
1074
1075 // restore oop result, if any
1076 if (return_oop) {
1077 caller_fr.set_saved_oop_result(&map, return_value());
1078 }
1079 }
1080
1081 // This is a safepoint poll. Verify the return address and block.
1082 else {
1083 set_at_poll_safepoint(true);
1084
1085 // verify the blob built the "return address" correctly
1086 assert(real_return_addr == caller_fr.pc(), "must match");
1087
1088 // Block the thread
1089 SafepointSynchronize::block(thread());
1090 set_at_poll_safepoint(false);
1091
1092 // If we have a pending async exception deoptimize the frame
1093 // as otherwise we may never deliver it.
1094 if (thread()->has_async_condition()) {
1095 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1096 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1097 }
1098
1099 // If an exception has been installed we must check for a pending deoptimization
1100 // Deoptimize frame if exception has been thrown.
1101
1102 if (thread()->has_pending_exception() ) {
1103 RegisterMap map(thread(), true);
1104 frame caller_fr = stub_fr.sender(&map);
1105 if (caller_fr.is_deoptimized_frame()) {
1106 // The exception patch will destroy registers that are still
1107 // live and will be needed during deoptimization. Defer the
1108 // Async exception should have deferred the exception until the
1109 // next safepoint which will be detected when we get into
1110 // the interpreter so if we have an exception now things
1111 // are messed up.
1112
1113 fatal("Exception installed and deoptimization is pending");
1114 }
1115 }
1116 }
1117 }
1118
1119
1120 //
1121 // Statistics & Instrumentations
1122 //
1123 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1124 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1125 int SafepointSynchronize::_cur_stat_index = 0;
1126 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1127 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1128 jlong SafepointSynchronize::_max_sync_time = 0;
1129 jlong SafepointSynchronize::_max_vmop_time = 0;
1130 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1131
1132 static jlong cleanup_end_time = 0;
1133 static bool need_to_track_page_armed_status = false;
1134 static bool init_done = false;
1135
1136 // Helper method to print the header.
1137 static void print_header() {
1138 tty->print(" vmop "
1139 "[threads: total initially_running wait_to_block] ");
1140 tty->print("[time: spin block sync cleanup vmop] ");
1141
1142 // no page armed status printed out if it is always armed.
1143 if (need_to_track_page_armed_status) {
1144 tty->print("page_armed ");
1145 }
1146
1147 tty->print_cr("page_trap_count");
1148 }
1149
1150 void SafepointSynchronize::deferred_initialize_stat() {
1151 if (init_done) return;
1152
1153 if (PrintSafepointStatisticsCount <= 0) {
1154 fatal("Wrong PrintSafepointStatisticsCount");
1155 }
1156
1157 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1158 // be printed right away, in which case, _safepoint_stats will regress to
1159 // a single element array. Otherwise, it is a circular ring buffer with default
1160 // size of PrintSafepointStatisticsCount.
1161 int stats_array_size;
1162 if (PrintSafepointStatisticsTimeout > 0) {
1163 stats_array_size = 1;
1164 PrintSafepointStatistics = true;
1165 } else {
1166 stats_array_size = PrintSafepointStatisticsCount;
1167 }
1168 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1169 * sizeof(SafepointStats), mtInternal);
1170 guarantee(_safepoint_stats != NULL,
1171 "not enough memory for safepoint instrumentation data");
1172
1173 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1174 need_to_track_page_armed_status = true;
1175 }
1176 init_done = true;
1177 }
1178
1179 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1180 assert(init_done, "safepoint statistics array hasn't been initialized");
1181 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1182
1183 spstat->_time_stamp = _ts_of_current_safepoint;
1184
1185 VM_Operation *op = VMThread::vm_operation();
1186 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1187 if (op != NULL) {
1188 _safepoint_reasons[spstat->_vmop_type]++;
1189 }
1190
1191 spstat->_nof_total_threads = nof_threads;
1192 spstat->_nof_initial_running_threads = nof_running;
1193 spstat->_nof_threads_hit_page_trap = 0;
1194
1195 // Records the start time of spinning. The real time spent on spinning
1196 // will be adjusted when spin is done. Same trick is applied for time
1197 // spent on waiting for threads to block.
1198 if (nof_running != 0) {
1199 spstat->_time_to_spin = os::javaTimeNanos();
1200 } else {
1201 spstat->_time_to_spin = 0;
1202 }
1203 }
1204
1205 void SafepointSynchronize::update_statistics_on_spin_end() {
1206 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1207
1208 jlong cur_time = os::javaTimeNanos();
1209
1210 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1211 if (spstat->_nof_initial_running_threads != 0) {
1212 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1213 }
1214
1215 if (need_to_track_page_armed_status) {
1216 spstat->_page_armed = (PageArmed == 1);
1217 }
1218
1219 // Records the start time of waiting for to block. Updated when block is done.
1220 if (_waiting_to_block != 0) {
1221 spstat->_time_to_wait_to_block = cur_time;
1222 } else {
1223 spstat->_time_to_wait_to_block = 0;
1224 }
1225 }
1226
1227 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1228 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1229
1230 if (spstat->_nof_threads_wait_to_block != 0) {
1231 spstat->_time_to_wait_to_block = end_time -
1232 spstat->_time_to_wait_to_block;
1233 }
1234
1235 // Records the end time of sync which will be used to calculate the total
1236 // vm operation time. Again, the real time spending in syncing will be deducted
1237 // from the start of the sync time later when end_statistics is called.
1238 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1239 if (spstat->_time_to_sync > _max_sync_time) {
1240 _max_sync_time = spstat->_time_to_sync;
1241 }
1242
1243 spstat->_time_to_do_cleanups = end_time;
1244 }
1245
1246 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1247 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1248
1249 // Record how long spent in cleanup tasks.
1250 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1251
1252 cleanup_end_time = end_time;
1253 }
1254
1255 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1256 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1257
1258 // Update the vm operation time.
1259 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1260 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1261 _max_vmop_time = spstat->_time_to_exec_vmop;
1262 }
1263 // Only the sync time longer than the specified
1264 // PrintSafepointStatisticsTimeout will be printed out right away.
1265 // By default, it is -1 meaning all samples will be put into the list.
1266 if ( PrintSafepointStatisticsTimeout > 0) {
1267 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1268 print_statistics();
1269 }
1270 } else {
1271 // The safepoint statistics will be printed out when the _safepoin_stats
1272 // array fills up.
1273 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1274 print_statistics();
1275 _cur_stat_index = 0;
1276 } else {
1277 _cur_stat_index++;
1278 }
1279 }
1280 }
1281
1282 void SafepointSynchronize::print_statistics() {
1283 SafepointStats* sstats = _safepoint_stats;
1284
1285 for (int index = 0; index <= _cur_stat_index; index++) {
1286 if (index % 30 == 0) {
1287 print_header();
1288 }
1289 sstats = &_safepoint_stats[index];
1290 tty->print("%.3f: ", sstats->_time_stamp);
1291 tty->print("%-26s ["
1292 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1293 " ] ",
1294 sstats->_vmop_type == -1 ? "no vm operation" :
1295 VM_Operation::name(sstats->_vmop_type),
1296 sstats->_nof_total_threads,
1297 sstats->_nof_initial_running_threads,
1298 sstats->_nof_threads_wait_to_block);
1299 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1300 tty->print(" ["
1301 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1302 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1303 INT64_FORMAT_W(6)" ] ",
1304 sstats->_time_to_spin / MICROUNITS,
1305 sstats->_time_to_wait_to_block / MICROUNITS,
1306 sstats->_time_to_sync / MICROUNITS,
1307 sstats->_time_to_do_cleanups / MICROUNITS,
1308 sstats->_time_to_exec_vmop / MICROUNITS);
1309
1310 if (need_to_track_page_armed_status) {
1311 tty->print(INT32_FORMAT" ", sstats->_page_armed);
1312 }
1313 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
1314 }
1315 }
1316
1317 // This method will be called when VM exits. It will first call
1318 // print_statistics to print out the rest of the sampling. Then
1319 // it tries to summarize the sampling.
1320 void SafepointSynchronize::print_stat_on_exit() {
1321 if (_safepoint_stats == NULL) return;
1322
1323 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1324
1325 // During VM exit, end_statistics may not get called and in that
1326 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1327 // don't print it out.
1328 // Approximate the vm op time.
1329 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1330 os::javaTimeNanos() - cleanup_end_time;
1331
1332 if ( PrintSafepointStatisticsTimeout < 0 ||
1333 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1334 print_statistics();
1335 }
1336 tty->cr();
1337
1338 // Print out polling page sampling status.
1339 if (!need_to_track_page_armed_status) {
1340 if (UseCompilerSafepoints) {
1341 tty->print_cr("Polling page always armed");
1342 }
1343 } else {
1344 tty->print_cr("Defer polling page loop count = %d\n",
1345 DeferPollingPageLoopCount);
1346 }
1347
1348 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1349 if (_safepoint_reasons[index] != 0) {
1350 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1351 _safepoint_reasons[index]);
1352 }
1353 }
1354
1355 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1356 _coalesced_vmop_count);
1357 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
1358 _max_sync_time / MICROUNITS);
1359 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1360 INT64_FORMAT_W(5)" ms",
1361 _max_vmop_time / MICROUNITS);
1362 }
1363
1364 // ------------------------------------------------------------------------------------------------
1365 // Non-product code
1366
1367 #ifndef PRODUCT
1368
1369 void SafepointSynchronize::print_state() {
1370 if (_state == _not_synchronized) {
1371 tty->print_cr("not synchronized");
1372 } else if (_state == _synchronizing || _state == _synchronized) {
1373 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1374 "synchronized");
1375
1376 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1377 cur->safepoint_state()->print();
1378 }
1379 }
1380 }
1381
1382 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1383 if (ShowSafepointMsgs) {
1384 va_list ap;
1385 va_start(ap, format);
1386 tty->vprint_cr(format, ap);
1387 va_end(ap);
1388 }
1389 }
1390
1391 #endif // !PRODUCT