1 /*
2 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
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 "services/memTracker.hpp"
52 #include "services/runtimeService.hpp"
53 #include "utilities/events.hpp"
54 #ifdef TARGET_ARCH_x86
55 # include "nativeInst_x86.hpp"
56 # include "vmreg_x86.inline.hpp"
57 #endif
58 #ifdef TARGET_ARCH_sparc
59 # include "nativeInst_sparc.hpp"
60 # include "vmreg_sparc.inline.hpp"
61 #endif
62 #ifdef TARGET_ARCH_zero
63 # include "nativeInst_zero.hpp"
64 # include "vmreg_zero.inline.hpp"
65 #endif
66 #ifdef TARGET_ARCH_arm
67 # include "nativeInst_arm.hpp"
68 # include "vmreg_arm.inline.hpp"
69 #endif
70 #ifdef TARGET_ARCH_ppc
71 # include "nativeInst_ppc.hpp"
72 # include "vmreg_ppc.inline.hpp"
73 #endif
74 #ifdef TARGET_OS_FAMILY_linux
75 # include "thread_linux.inline.hpp"
76 #endif
77 #ifdef TARGET_OS_FAMILY_solaris
78 # include "thread_solaris.inline.hpp"
79 #endif
80 #ifdef TARGET_OS_FAMILY_windows
81 # include "thread_windows.inline.hpp"
82 #endif
83 #ifdef TARGET_OS_FAMILY_bsd
84 # include "thread_bsd.inline.hpp"
85 #endif
86 #ifndef SERIALGC
87 #include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp"
88 #include "gc_implementation/shared/concurrentGCThread.hpp"
89 #endif
90 #ifdef COMPILER1
91 #include "c1/c1_globals.hpp"
92 #endif
93
94 // --------------------------------------------------------------------------------------------------
95 // Implementation of Safepoint begin/end
96
97 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
98 volatile int SafepointSynchronize::_waiting_to_block = 0;
99 volatile int SafepointSynchronize::_safepoint_counter = 0;
100 int SafepointSynchronize::_current_jni_active_count = 0;
101 long SafepointSynchronize::_end_of_last_safepoint = 0;
102 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
103 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
104 static bool timeout_error_printed = false;
105
106 // Roll all threads forward to a safepoint and suspend them all
107 void SafepointSynchronize::begin() {
108
109 Thread* myThread = Thread::current();
110 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
111
112 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
113 _safepoint_begin_time = os::javaTimeNanos();
114 _ts_of_current_safepoint = tty->time_stamp().seconds();
115 }
116
117 #ifndef SERIALGC
118 if (UseConcMarkSweepGC) {
119 // In the future we should investigate whether CMS can use the
120 // more-general mechanism below. DLD (01/05).
121 ConcurrentMarkSweepThread::synchronize(false);
122 } else if (UseG1GC) {
123 ConcurrentGCThread::safepoint_synchronize();
124 }
125 #endif // SERIALGC
126
127 // By getting the Threads_lock, we assure that no threads are about to start or
128 // exit. It is released again in SafepointSynchronize::end().
129 Threads_lock->lock();
130
131 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
132
133 int nof_threads = Threads::number_of_threads();
134
135 if (TraceSafepoint) {
136 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
137 }
138
139 RuntimeService::record_safepoint_begin();
140
141 MutexLocker mu(Safepoint_lock);
142
143 // Reset the count of active JNI critical threads
144 _current_jni_active_count = 0;
145
146 // Set number of threads to wait for, before we initiate the callbacks
147 _waiting_to_block = nof_threads;
148 TryingToBlock = 0 ;
149 int still_running = nof_threads;
150
151 // Save the starting time, so that it can be compared to see if this has taken
152 // too long to complete.
153 jlong safepoint_limit_time;
154 timeout_error_printed = false;
155
156 // PrintSafepointStatisticsTimeout can be specified separately. When
157 // specified, PrintSafepointStatistics will be set to true in
158 // deferred_initialize_stat method. The initialization has to be done
159 // early enough to avoid any races. See bug 6880029 for details.
160 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
161 deferred_initialize_stat();
162 }
163
164 // Begin the process of bringing the system to a safepoint.
165 // Java threads can be in several different states and are
166 // stopped by different mechanisms:
167 //
168 // 1. Running interpreted
169 // The interpeter dispatch table is changed to force it to
170 // check for a safepoint condition between bytecodes.
171 // 2. Running in native code
172 // When returning from the native code, a Java thread must check
173 // the safepoint _state to see if we must block. If the
174 // VM thread sees a Java thread in native, it does
175 // not wait for this thread to block. The order of the memory
176 // writes and reads of both the safepoint state and the Java
177 // threads state is critical. In order to guarantee that the
178 // memory writes are serialized with respect to each other,
179 // the VM thread issues a memory barrier instruction
180 // (on MP systems). In order to avoid the overhead of issuing
181 // a memory barrier for each Java thread making native calls, each Java
182 // thread performs a write to a single memory page after changing
183 // the thread state. The VM thread performs a sequence of
184 // mprotect OS calls which forces all previous writes from all
185 // Java threads to be serialized. This is done in the
186 // os::serialize_thread_states() call. This has proven to be
187 // much more efficient than executing a membar instruction
188 // on every call to native code.
189 // 3. Running compiled Code
190 // Compiled code reads a global (Safepoint Polling) page that
191 // is set to fault if we are trying to get to a safepoint.
192 // 4. Blocked
193 // A thread which is blocked will not be allowed to return from the
194 // block condition until the safepoint operation is complete.
195 // 5. In VM or Transitioning between states
196 // If a Java thread is currently running in the VM or transitioning
197 // between states, the safepointing code will wait for the thread to
198 // block itself when it attempts transitions to a new state.
199 //
200 _state = _synchronizing;
201 OrderAccess::fence();
202
203 // Flush all thread states to memory
204 if (!UseMembar) {
205 os::serialize_thread_states();
206 }
207
208 // Make interpreter safepoint aware
209 Interpreter::notice_safepoints();
210
211 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
212 // Make polling safepoint aware
213 guarantee (PageArmed == 0, "invariant") ;
214 PageArmed = 1 ;
215 os::make_polling_page_unreadable();
216 }
217
218 // Consider using active_processor_count() ... but that call is expensive.
219 int ncpus = os::processor_count() ;
220
221 #ifdef ASSERT
222 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
223 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
224 // Clear the visited flag to ensure that the critical counts are collected properly.
225 cur->set_visited_for_critical_count(false);
226 }
227 #endif // ASSERT
228
229 if (SafepointTimeout)
230 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
231
232 // Iterate through all threads until it have been determined how to stop them all at a safepoint
233 unsigned int iterations = 0;
234 int steps = 0 ;
235 while(still_running > 0) {
236 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
237 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
238 ThreadSafepointState *cur_state = cur->safepoint_state();
239 if (cur_state->is_running()) {
240 cur_state->examine_state_of_thread();
241 if (!cur_state->is_running()) {
242 still_running--;
243 // consider adjusting steps downward:
244 // steps = 0
245 // steps -= NNN
246 // steps >>= 1
247 // steps = MIN(steps, 2000-100)
248 // if (iterations != 0) steps -= NNN
249 }
250 if (TraceSafepoint && Verbose) cur_state->print();
251 }
252 }
253
254 if (PrintSafepointStatistics && iterations == 0) {
255 begin_statistics(nof_threads, still_running);
256 }
257
258 if (still_running > 0) {
259 // Check for if it takes to long
260 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
261 print_safepoint_timeout(_spinning_timeout);
262 }
263
264 // Spin to avoid context switching.
265 // There's a tension between allowing the mutators to run (and rendezvous)
266 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
267 // a mutator might otherwise use profitably to reach a safepoint. Excessive
268 // spinning by the VM thread on a saturated system can increase rendezvous latency.
269 // Blocking or yielding incur their own penalties in the form of context switching
270 // and the resultant loss of $ residency.
271 //
272 // Further complicating matters is that yield() does not work as naively expected
273 // on many platforms -- yield() does not guarantee that any other ready threads
274 // will run. As such we revert yield_all() after some number of iterations.
275 // Yield_all() is implemented as a short unconditional sleep on some platforms.
276 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
277 // can actually increase the time it takes the VM thread to detect that a system-wide
278 // stop-the-world safepoint has been reached. In a pathological scenario such as that
279 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
280 // In that case the mutators will be stalled waiting for the safepoint to complete and the
281 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
282 // will eventually wake up and detect that all mutators are safe, at which point
283 // we'll again make progress.
284 //
285 // Beware too that that the VMThread typically runs at elevated priority.
286 // Its default priority is higher than the default mutator priority.
287 // Obviously, this complicates spinning.
288 //
289 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
290 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
291 //
292 // See the comments in synchronizer.cpp for additional remarks on spinning.
293 //
294 // In the future we might:
295 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
296 // This is tricky as the path used by a thread exiting the JVM (say on
297 // on JNI call-out) simply stores into its state field. The burden
298 // is placed on the VM thread, which must poll (spin).
299 // 2. Find something useful to do while spinning. If the safepoint is GC-related
300 // we might aggressively scan the stacks of threads that are already safe.
301 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
302 // If all the mutators are ONPROC there's no reason to sleep or yield.
303 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
304 // 5. Check system saturation. If the system is not fully saturated then
305 // simply spin and avoid sleep/yield.
306 // 6. As still-running mutators rendezvous they could unpark the sleeping
307 // VMthread. This works well for still-running mutators that become
308 // safe. The VMthread must still poll for mutators that call-out.
309 // 7. Drive the policy on time-since-begin instead of iterations.
310 // 8. Consider making the spin duration a function of the # of CPUs:
311 // Spin = (((ncpus-1) * M) + K) + F(still_running)
312 // Alternately, instead of counting iterations of the outer loop
313 // we could count the # of threads visited in the inner loop, above.
314 // 9. On windows consider using the return value from SwitchThreadTo()
315 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
316
317 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
318 guarantee (PageArmed == 0, "invariant") ;
319 PageArmed = 1 ;
320 os::make_polling_page_unreadable();
321 }
322
323 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
324 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
325 ++steps ;
326 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
327 SpinPause() ; // MP-Polite spin
328 } else
329 if (steps < DeferThrSuspendLoopCount) {
330 os::NakedYield() ;
331 } else {
332 os::yield_all(steps) ;
333 // Alternately, the VM thread could transiently depress its scheduling priority or
334 // transiently increase the priority of the tardy mutator(s).
335 }
336
337 iterations ++ ;
338 }
339 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
340 }
341 assert(still_running == 0, "sanity check");
342
343 if (PrintSafepointStatistics) {
344 update_statistics_on_spin_end();
345 }
346
347 // wait until all threads are stopped
348 while (_waiting_to_block > 0) {
349 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
350 if (!SafepointTimeout || timeout_error_printed) {
351 Safepoint_lock->wait(true); // true, means with no safepoint checks
352 } else {
353 // Compute remaining time
354 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
355
356 // If there is no remaining time, then there is an error
357 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
358 print_safepoint_timeout(_blocking_timeout);
359 }
360 }
361 }
362 assert(_waiting_to_block == 0, "sanity check");
363
364 #ifndef PRODUCT
365 if (SafepointTimeout) {
366 jlong current_time = os::javaTimeNanos();
367 if (safepoint_limit_time < current_time) {
368 tty->print_cr("# SafepointSynchronize: Finished after "
369 INT64_FORMAT_W(6) " ms",
370 ((current_time - safepoint_limit_time) / MICROUNITS +
371 SafepointTimeoutDelay));
372 }
373 }
374 #endif
375
376 assert((_safepoint_counter & 0x1) == 0, "must be even");
377 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
378 _safepoint_counter ++;
379
380 // Record state
381 _state = _synchronized;
382
383 OrderAccess::fence();
384
385 #ifdef ASSERT
386 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
387 // make sure all the threads were visited
388 assert(cur->was_visited_for_critical_count(), "missed a thread");
389 }
390 #endif // ASSERT
391
392 // Update the count of active JNI critical regions
393 GC_locker::set_jni_lock_count(_current_jni_active_count);
394
395 if (TraceSafepoint) {
396 VM_Operation *op = VMThread::vm_operation();
397 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
398 }
399
400 RuntimeService::record_safepoint_synchronized();
401 if (PrintSafepointStatistics) {
402 update_statistics_on_sync_end(os::javaTimeNanos());
403 }
404
405 // Call stuff that needs to be run when a safepoint is just about to be completed
406 do_cleanup_tasks();
407
408 if (PrintSafepointStatistics) {
409 // Record how much time spend on the above cleanup tasks
410 update_statistics_on_cleanup_end(os::javaTimeNanos());
411 }
412 }
413
414 // Wake up all threads, so they are ready to resume execution after the safepoint
415 // operation has been carried out
416 void SafepointSynchronize::end() {
417
418 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
419 assert((_safepoint_counter & 0x1) == 1, "must be odd");
420 _safepoint_counter ++;
421 // memory fence isn't required here since an odd _safepoint_counter
422 // value can do no harm and a fence is issued below anyway.
423
424 DEBUG_ONLY(Thread* myThread = Thread::current();)
425 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
426
427 if (PrintSafepointStatistics) {
428 end_statistics(os::javaTimeNanos());
429 }
430
431 #ifdef ASSERT
432 // A pending_exception cannot be installed during a safepoint. The threads
433 // may install an async exception after they come back from a safepoint into
434 // pending_exception after they unblock. But that should happen later.
435 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
436 assert (!(cur->has_pending_exception() &&
437 cur->safepoint_state()->is_at_poll_safepoint()),
438 "safepoint installed a pending exception");
439 }
440 #endif // ASSERT
441
442 if (PageArmed) {
443 // Make polling safepoint aware
444 os::make_polling_page_readable();
445 PageArmed = 0 ;
446 }
447
448 // Remove safepoint check from interpreter
449 Interpreter::ignore_safepoints();
450
451 {
452 MutexLocker mu(Safepoint_lock);
453
454 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
455
456 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
457 // when they get restarted.
458 _state = _not_synchronized;
459 OrderAccess::fence();
460
461 if (TraceSafepoint) {
462 tty->print_cr("Leaving safepoint region");
463 }
464
465 // Start suspended threads
466 for(JavaThread *current = Threads::first(); current; current = current->next()) {
467 // A problem occurring on Solaris is when attempting to restart threads
468 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
469 // to the next one (since it has been running the longest). We then have
470 // to wait for a cpu to become available before we can continue restarting
471 // threads.
472 // FIXME: This causes the performance of the VM to degrade when active and with
473 // large numbers of threads. Apparently this is due to the synchronous nature
474 // of suspending threads.
475 //
476 // TODO-FIXME: the comments above are vestigial and no longer apply.
477 // Furthermore, using solaris' schedctl in this particular context confers no benefit
478 if (VMThreadHintNoPreempt) {
479 os::hint_no_preempt();
480 }
481 ThreadSafepointState* cur_state = current->safepoint_state();
482 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
483 cur_state->restart();
484 assert(cur_state->is_running(), "safepoint state has not been reset");
485 }
486
487 RuntimeService::record_safepoint_end();
488
489 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
490 // blocked in signal_thread_blocked
491 Threads_lock->unlock();
492
493 }
494 #ifndef SERIALGC
495 // If there are any concurrent GC threads resume them.
496 if (UseConcMarkSweepGC) {
497 ConcurrentMarkSweepThread::desynchronize(false);
498 } else if (UseG1GC) {
499 ConcurrentGCThread::safepoint_desynchronize();
500 }
501 #endif // SERIALGC
502 // record this time so VMThread can keep track how much time has elasped
503 // since last safepoint.
504 _end_of_last_safepoint = os::javaTimeMillis();
505 }
506
507 bool SafepointSynchronize::is_cleanup_needed() {
508 // Need a safepoint if some inline cache buffers is non-empty
509 if (!InlineCacheBuffer::is_empty()) return true;
510 return false;
511 }
512
513
514
515 // Various cleaning tasks that should be done periodically at safepoints
516 void SafepointSynchronize::do_cleanup_tasks() {
517 {
518 TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime);
519 ObjectSynchronizer::deflate_idle_monitors();
520 }
521
522 {
523 TraceTime t2("updating inline caches", TraceSafepointCleanupTime);
524 InlineCacheBuffer::update_inline_caches();
525 }
526 {
527 TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime);
528 CompilationPolicy::policy()->do_safepoint_work();
529 }
530
531 {
532 TraceTime t4("sweeping nmethods", TraceSafepointCleanupTime);
533 NMethodSweeper::scan_stacks();
534 }
535
536 if (SymbolTable::needs_rehashing()) {
537 TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime);
538 SymbolTable::rehash_table();
539 }
540
541 if (StringTable::needs_rehashing()) {
542 TraceTime t6("rehashing string table", TraceSafepointCleanupTime);
543 StringTable::rehash_table();
544 }
545
546 // rotate log files?
547 if (UseGCLogFileRotation) {
548 gclog_or_tty->rotate_log();
549 }
550
551 if (MemTracker::is_on()) {
552 MemTracker::sync();
553 }
554 }
555
556
557 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
558 switch(state) {
559 case _thread_in_native:
560 // native threads are safe if they have no java stack or have walkable stack
561 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
562
563 // blocked threads should have already have walkable stack
564 case _thread_blocked:
565 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
566 return true;
567
568 default:
569 return false;
570 }
571 }
572
573
574 // See if the thread is running inside a lazy critical native and
575 // update the thread critical count if so. Also set a suspend flag to
576 // cause the native wrapper to return into the JVM to do the unlock
577 // once the native finishes.
578 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
579 if (state == _thread_in_native &&
580 thread->has_last_Java_frame() &&
581 thread->frame_anchor()->walkable()) {
582 // This thread might be in a critical native nmethod so look at
583 // the top of the stack and increment the critical count if it
584 // is.
585 frame wrapper_frame = thread->last_frame();
586 CodeBlob* stub_cb = wrapper_frame.cb();
587 if (stub_cb != NULL &&
588 stub_cb->is_nmethod() &&
589 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
590 // A thread could potentially be in a critical native across
591 // more than one safepoint, so only update the critical state on
592 // the first one. When it returns it will perform the unlock.
593 if (!thread->do_critical_native_unlock()) {
594 #ifdef ASSERT
595 if (!thread->in_critical()) {
596 GC_locker::increment_debug_jni_lock_count();
597 }
598 #endif
599 thread->enter_critical();
600 // Make sure the native wrapper calls back on return to
601 // perform the needed critical unlock.
602 thread->set_critical_native_unlock();
603 }
604 }
605 }
606 }
607
608
609
610 // -------------------------------------------------------------------------------------------------------
611 // Implementation of Safepoint callback point
612
613 void SafepointSynchronize::block(JavaThread *thread) {
614 assert(thread != NULL, "thread must be set");
615 assert(thread->is_Java_thread(), "not a Java thread");
616
617 // Threads shouldn't block if they are in the middle of printing, but...
618 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
619
620 // Only bail from the block() call if the thread is gone from the
621 // thread list; starting to exit should still block.
622 if (thread->is_terminated()) {
623 // block current thread if we come here from native code when VM is gone
624 thread->block_if_vm_exited();
625
626 // otherwise do nothing
627 return;
628 }
629
630 JavaThreadState state = thread->thread_state();
631 thread->frame_anchor()->make_walkable(thread);
632
633 // Check that we have a valid thread_state at this point
634 switch(state) {
635 case _thread_in_vm_trans:
636 case _thread_in_Java: // From compiled code
637
638 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
639 // we pretend we are still in the VM.
640 thread->set_thread_state(_thread_in_vm);
641
642 if (is_synchronizing()) {
643 Atomic::inc (&TryingToBlock) ;
644 }
645
646 // We will always be holding the Safepoint_lock when we are examine the state
647 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
648 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
649 Safepoint_lock->lock_without_safepoint_check();
650 if (is_synchronizing()) {
651 // Decrement the number of threads to wait for and signal vm thread
652 assert(_waiting_to_block > 0, "sanity check");
653 _waiting_to_block--;
654 thread->safepoint_state()->set_has_called_back(true);
655
656 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
657 if (thread->in_critical()) {
658 // Notice that this thread is in a critical section
659 increment_jni_active_count();
660 }
661
662 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
663 if (_waiting_to_block == 0) {
664 Safepoint_lock->notify_all();
665 }
666 }
667
668 // We transition the thread to state _thread_blocked here, but
669 // we can't do our usual check for external suspension and then
670 // self-suspend after the lock_without_safepoint_check() call
671 // below because we are often called during transitions while
672 // we hold different locks. That would leave us suspended while
673 // holding a resource which results in deadlocks.
674 thread->set_thread_state(_thread_blocked);
675 Safepoint_lock->unlock();
676
677 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
678 // the entire safepoint, the threads will all line up here during the safepoint.
679 Threads_lock->lock_without_safepoint_check();
680 // restore original state. This is important if the thread comes from compiled code, so it
681 // will continue to execute with the _thread_in_Java state.
682 thread->set_thread_state(state);
683 Threads_lock->unlock();
684 break;
685
686 case _thread_in_native_trans:
687 case _thread_blocked_trans:
688 case _thread_new_trans:
689 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
690 thread->print_thread_state();
691 fatal("Deadlock in safepoint code. "
692 "Should have called back to the VM before blocking.");
693 }
694
695 // We transition the thread to state _thread_blocked here, but
696 // we can't do our usual check for external suspension and then
697 // self-suspend after the lock_without_safepoint_check() call
698 // below because we are often called during transitions while
699 // we hold different locks. That would leave us suspended while
700 // holding a resource which results in deadlocks.
701 thread->set_thread_state(_thread_blocked);
702
703 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
704 // the safepoint code might still be waiting for it to block. We need to change the state here,
705 // so it can see that it is at a safepoint.
706
707 // Block until the safepoint operation is completed.
708 Threads_lock->lock_without_safepoint_check();
709
710 // Restore state
711 thread->set_thread_state(state);
712
713 Threads_lock->unlock();
714 break;
715
716 default:
717 fatal(err_msg("Illegal threadstate encountered: %d", state));
718 }
719
720 // Check for pending. async. exceptions or suspends - except if the
721 // thread was blocked inside the VM. has_special_runtime_exit_condition()
722 // is called last since it grabs a lock and we only want to do that when
723 // we must.
724 //
725 // Note: we never deliver an async exception at a polling point as the
726 // compiler may not have an exception handler for it. The polling
727 // code will notice the async and deoptimize and the exception will
728 // be delivered. (Polling at a return point is ok though). Sure is
729 // a lot of bother for a deprecated feature...
730 //
731 // We don't deliver an async exception if the thread state is
732 // _thread_in_native_trans so JNI functions won't be called with
733 // a surprising pending exception. If the thread state is going back to java,
734 // async exception is checked in check_special_condition_for_native_trans().
735
736 if (state != _thread_blocked_trans &&
737 state != _thread_in_vm_trans &&
738 thread->has_special_runtime_exit_condition()) {
739 thread->handle_special_runtime_exit_condition(
740 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
741 }
742 }
743
744 // ------------------------------------------------------------------------------------------------------
745 // Exception handlers
746
747 #ifndef PRODUCT
748
749 #ifdef SPARC
750
751 #ifdef _LP64
752 #define PTR_PAD ""
753 #else
754 #define PTR_PAD " "
755 #endif
756
757 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
758 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false;
759 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
760 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
761 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
762 }
763
764 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
765 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false;
766 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
767 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
768 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
769 }
770
771 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
772 #ifdef _LP64
773 tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
774 const int incr = 1; // Increment to skip a long, in units of intptr_t
775 #else
776 tty->print_cr("--------+--address-+------before-----------+-------after----------+");
777 const int incr = 2; // Increment to skip a long, in units of intptr_t
778 #endif
779 tty->print_cr("---SP---|");
780 for( int i=0; i<16; i++ ) {
781 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
782 tty->print_cr("--------|");
783 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
784 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
785 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
786 tty->print_cr("--------|");
787 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;
788 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;
789 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;
790 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;
791 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
792 old_sp += incr; new_sp += incr; was_oops += incr;
793 // Skip the floats
794 tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
795 tty->print_cr("---FP---|");
796 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32;
797 for( int i2=0; i2<16; i2++ ) {
798 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
799 tty->print_cr("");
800 }
801 #endif // SPARC
802 #endif // PRODUCT
803
804
805 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
806 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
807 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
808 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
809
810 // Uncomment this to get some serious before/after printing of the
811 // Sparc safepoint-blob frame structure.
812 /*
813 intptr_t* sp = thread->last_Java_sp();
814 intptr_t stack_copy[150];
815 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
816 bool was_oops[150];
817 for( int i=0; i<150; i++ )
818 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
819 */
820
821 if (ShowSafepointMsgs) {
822 tty->print("handle_polling_page_exception: ");
823 }
824
825 if (PrintSafepointStatistics) {
826 inc_page_trap_count();
827 }
828
829 ThreadSafepointState* state = thread->safepoint_state();
830
831 state->handle_polling_page_exception();
832 // print_me(sp,stack_copy,was_oops);
833 }
834
835
836 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
837 if (!timeout_error_printed) {
838 timeout_error_printed = true;
839 // Print out the thread infor which didn't reach the safepoint for debugging
840 // purposes (useful when there are lots of threads in the debugger).
841 tty->print_cr("");
842 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
843 if (reason == _spinning_timeout) {
844 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
845 } else if (reason == _blocking_timeout) {
846 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
847 }
848
849 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
850 ThreadSafepointState *cur_state;
851 ResourceMark rm;
852 for(JavaThread *cur_thread = Threads::first(); cur_thread;
853 cur_thread = cur_thread->next()) {
854 cur_state = cur_thread->safepoint_state();
855
856 if (cur_thread->thread_state() != _thread_blocked &&
857 ((reason == _spinning_timeout && cur_state->is_running()) ||
858 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
859 tty->print("# ");
860 cur_thread->print();
861 tty->print_cr("");
862 }
863 }
864 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
865 }
866
867 // To debug the long safepoint, specify both DieOnSafepointTimeout &
868 // ShowMessageBoxOnError.
869 if (DieOnSafepointTimeout) {
870 char msg[1024];
871 VM_Operation *op = VMThread::vm_operation();
872 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
873 SafepointTimeoutDelay,
874 op != NULL ? op->name() : "no vm operation");
875 fatal(msg);
876 }
877 }
878
879
880 // -------------------------------------------------------------------------------------------------------
881 // Implementation of ThreadSafepointState
882
883 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
884 _thread = thread;
885 _type = _running;
886 _has_called_back = false;
887 _at_poll_safepoint = false;
888 }
889
890 void ThreadSafepointState::create(JavaThread *thread) {
891 ThreadSafepointState *state = new ThreadSafepointState(thread);
892 thread->set_safepoint_state(state);
893 }
894
895 void ThreadSafepointState::destroy(JavaThread *thread) {
896 if (thread->safepoint_state()) {
897 delete(thread->safepoint_state());
898 thread->set_safepoint_state(NULL);
899 }
900 }
901
902 void ThreadSafepointState::examine_state_of_thread() {
903 assert(is_running(), "better be running or just have hit safepoint poll");
904
905 JavaThreadState state = _thread->thread_state();
906
907 // Save the state at the start of safepoint processing.
908 _orig_thread_state = state;
909
910 // Check for a thread that is suspended. Note that thread resume tries
911 // to grab the Threads_lock which we own here, so a thread cannot be
912 // resumed during safepoint synchronization.
913
914 // We check to see if this thread is suspended without locking to
915 // avoid deadlocking with a third thread that is waiting for this
916 // thread to be suspended. The third thread can notice the safepoint
917 // that we're trying to start at the beginning of its SR_lock->wait()
918 // call. If that happens, then the third thread will block on the
919 // safepoint while still holding the underlying SR_lock. We won't be
920 // able to get the SR_lock and we'll deadlock.
921 //
922 // We don't need to grab the SR_lock here for two reasons:
923 // 1) The suspend flags are both volatile and are set with an
924 // Atomic::cmpxchg() call so we should see the suspended
925 // state right away.
926 // 2) We're being called from the safepoint polling loop; if
927 // we don't see the suspended state on this iteration, then
928 // we'll come around again.
929 //
930 bool is_suspended = _thread->is_ext_suspended();
931 if (is_suspended) {
932 roll_forward(_at_safepoint);
933 return;
934 }
935
936 // Some JavaThread states have an initial safepoint state of
937 // running, but are actually at a safepoint. We will happily
938 // agree and update the safepoint state here.
939 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
940 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
941 roll_forward(_at_safepoint);
942 return;
943 }
944
945 if (state == _thread_in_vm) {
946 roll_forward(_call_back);
947 return;
948 }
949
950 // All other thread states will continue to run until they
951 // transition and self-block in state _blocked
952 // Safepoint polling in compiled code causes the Java threads to do the same.
953 // Note: new threads may require a malloc so they must be allowed to finish
954
955 assert(is_running(), "examine_state_of_thread on non-running thread");
956 return;
957 }
958
959 // Returns true is thread could not be rolled forward at present position.
960 void ThreadSafepointState::roll_forward(suspend_type type) {
961 _type = type;
962
963 switch(_type) {
964 case _at_safepoint:
965 SafepointSynchronize::signal_thread_at_safepoint();
966 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
967 if (_thread->in_critical()) {
968 // Notice that this thread is in a critical section
969 SafepointSynchronize::increment_jni_active_count();
970 }
971 break;
972
973 case _call_back:
974 set_has_called_back(false);
975 break;
976
977 case _running:
978 default:
979 ShouldNotReachHere();
980 }
981 }
982
983 void ThreadSafepointState::restart() {
984 switch(type()) {
985 case _at_safepoint:
986 case _call_back:
987 break;
988
989 case _running:
990 default:
991 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
992 _thread, _type);
993 _thread->print();
994 ShouldNotReachHere();
995 }
996 _type = _running;
997 set_has_called_back(false);
998 }
999
1000
1001 void ThreadSafepointState::print_on(outputStream *st) const {
1002 const char *s;
1003
1004 switch(_type) {
1005 case _running : s = "_running"; break;
1006 case _at_safepoint : s = "_at_safepoint"; break;
1007 case _call_back : s = "_call_back"; break;
1008 default:
1009 ShouldNotReachHere();
1010 }
1011
1012 st->print_cr("Thread: " INTPTR_FORMAT
1013 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
1014 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
1015 _at_poll_safepoint);
1016
1017 _thread->print_thread_state_on(st);
1018 }
1019
1020
1021 // ---------------------------------------------------------------------------------------------------------------------
1022
1023 // Block the thread at the safepoint poll or poll return.
1024 void ThreadSafepointState::handle_polling_page_exception() {
1025
1026 // Check state. block() will set thread state to thread_in_vm which will
1027 // cause the safepoint state _type to become _call_back.
1028 assert(type() == ThreadSafepointState::_running,
1029 "polling page exception on thread not running state");
1030
1031 // Step 1: Find the nmethod from the return address
1032 if (ShowSafepointMsgs && Verbose) {
1033 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
1034 }
1035 address real_return_addr = thread()->saved_exception_pc();
1036
1037 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
1038 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
1039 nmethod* nm = (nmethod*)cb;
1040
1041 // Find frame of caller
1042 frame stub_fr = thread()->last_frame();
1043 CodeBlob* stub_cb = stub_fr.cb();
1044 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
1045 RegisterMap map(thread(), true);
1046 frame caller_fr = stub_fr.sender(&map);
1047
1048 // Should only be poll_return or poll
1049 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
1050
1051 // This is a poll immediately before a return. The exception handling code
1052 // has already had the effect of causing the return to occur, so the execution
1053 // will continue immediately after the call. In addition, the oopmap at the
1054 // return point does not mark the return value as an oop (if it is), so
1055 // it needs a handle here to be updated.
1056 if( nm->is_at_poll_return(real_return_addr) ) {
1057 // See if return type is an oop.
1058 bool return_oop = nm->method()->is_returning_oop();
1059 Handle return_value;
1060 if (return_oop) {
1061 // The oop result has been saved on the stack together with all
1062 // the other registers. In order to preserve it over GCs we need
1063 // to keep it in a handle.
1064 oop result = caller_fr.saved_oop_result(&map);
1065 assert(result == NULL || result->is_oop(), "must be oop");
1066 return_value = Handle(thread(), result);
1067 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
1068 }
1069
1070 // Block the thread
1071 SafepointSynchronize::block(thread());
1072
1073 // restore oop result, if any
1074 if (return_oop) {
1075 caller_fr.set_saved_oop_result(&map, return_value());
1076 }
1077 }
1078
1079 // This is a safepoint poll. Verify the return address and block.
1080 else {
1081 set_at_poll_safepoint(true);
1082
1083 // verify the blob built the "return address" correctly
1084 assert(real_return_addr == caller_fr.pc(), "must match");
1085
1086 // Block the thread
1087 SafepointSynchronize::block(thread());
1088 set_at_poll_safepoint(false);
1089
1090 // If we have a pending async exception deoptimize the frame
1091 // as otherwise we may never deliver it.
1092 if (thread()->has_async_condition()) {
1093 ThreadInVMfromJavaNoAsyncException __tiv(thread());
1094 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
1095 }
1096
1097 // If an exception has been installed we must check for a pending deoptimization
1098 // Deoptimize frame if exception has been thrown.
1099
1100 if (thread()->has_pending_exception() ) {
1101 RegisterMap map(thread(), true);
1102 frame caller_fr = stub_fr.sender(&map);
1103 if (caller_fr.is_deoptimized_frame()) {
1104 // The exception patch will destroy registers that are still
1105 // live and will be needed during deoptimization. Defer the
1106 // Async exception should have defered the exception until the
1107 // next safepoint which will be detected when we get into
1108 // the interpreter so if we have an exception now things
1109 // are messed up.
1110
1111 fatal("Exception installed and deoptimization is pending");
1112 }
1113 }
1114 }
1115 }
1116
1117
1118 //
1119 // Statistics & Instrumentations
1120 //
1121 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
1122 jlong SafepointSynchronize::_safepoint_begin_time = 0;
1123 int SafepointSynchronize::_cur_stat_index = 0;
1124 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
1125 julong SafepointSynchronize::_coalesced_vmop_count = 0;
1126 jlong SafepointSynchronize::_max_sync_time = 0;
1127 jlong SafepointSynchronize::_max_vmop_time = 0;
1128 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
1129
1130 static jlong cleanup_end_time = 0;
1131 static bool need_to_track_page_armed_status = false;
1132 static bool init_done = false;
1133
1134 // Helper method to print the header.
1135 static void print_header() {
1136 tty->print(" vmop "
1137 "[threads: total initially_running wait_to_block] ");
1138 tty->print("[time: spin block sync cleanup vmop] ");
1139
1140 // no page armed status printed out if it is always armed.
1141 if (need_to_track_page_armed_status) {
1142 tty->print("page_armed ");
1143 }
1144
1145 tty->print_cr("page_trap_count");
1146 }
1147
1148 void SafepointSynchronize::deferred_initialize_stat() {
1149 if (init_done) return;
1150
1151 if (PrintSafepointStatisticsCount <= 0) {
1152 fatal("Wrong PrintSafepointStatisticsCount");
1153 }
1154
1155 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
1156 // be printed right away, in which case, _safepoint_stats will regress to
1157 // a single element array. Otherwise, it is a circular ring buffer with default
1158 // size of PrintSafepointStatisticsCount.
1159 int stats_array_size;
1160 if (PrintSafepointStatisticsTimeout > 0) {
1161 stats_array_size = 1;
1162 PrintSafepointStatistics = true;
1163 } else {
1164 stats_array_size = PrintSafepointStatisticsCount;
1165 }
1166 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
1167 * sizeof(SafepointStats), mtInternal);
1168 guarantee(_safepoint_stats != NULL,
1169 "not enough memory for safepoint instrumentation data");
1170
1171 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
1172 need_to_track_page_armed_status = true;
1173 }
1174 init_done = true;
1175 }
1176
1177 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
1178 assert(init_done, "safepoint statistics array hasn't been initialized");
1179 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1180
1181 spstat->_time_stamp = _ts_of_current_safepoint;
1182
1183 VM_Operation *op = VMThread::vm_operation();
1184 spstat->_vmop_type = (op != NULL ? op->type() : -1);
1185 if (op != NULL) {
1186 _safepoint_reasons[spstat->_vmop_type]++;
1187 }
1188
1189 spstat->_nof_total_threads = nof_threads;
1190 spstat->_nof_initial_running_threads = nof_running;
1191 spstat->_nof_threads_hit_page_trap = 0;
1192
1193 // Records the start time of spinning. The real time spent on spinning
1194 // will be adjusted when spin is done. Same trick is applied for time
1195 // spent on waiting for threads to block.
1196 if (nof_running != 0) {
1197 spstat->_time_to_spin = os::javaTimeNanos();
1198 } else {
1199 spstat->_time_to_spin = 0;
1200 }
1201 }
1202
1203 void SafepointSynchronize::update_statistics_on_spin_end() {
1204 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1205
1206 jlong cur_time = os::javaTimeNanos();
1207
1208 spstat->_nof_threads_wait_to_block = _waiting_to_block;
1209 if (spstat->_nof_initial_running_threads != 0) {
1210 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
1211 }
1212
1213 if (need_to_track_page_armed_status) {
1214 spstat->_page_armed = (PageArmed == 1);
1215 }
1216
1217 // Records the start time of waiting for to block. Updated when block is done.
1218 if (_waiting_to_block != 0) {
1219 spstat->_time_to_wait_to_block = cur_time;
1220 } else {
1221 spstat->_time_to_wait_to_block = 0;
1222 }
1223 }
1224
1225 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
1226 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1227
1228 if (spstat->_nof_threads_wait_to_block != 0) {
1229 spstat->_time_to_wait_to_block = end_time -
1230 spstat->_time_to_wait_to_block;
1231 }
1232
1233 // Records the end time of sync which will be used to calculate the total
1234 // vm operation time. Again, the real time spending in syncing will be deducted
1235 // from the start of the sync time later when end_statistics is called.
1236 spstat->_time_to_sync = end_time - _safepoint_begin_time;
1237 if (spstat->_time_to_sync > _max_sync_time) {
1238 _max_sync_time = spstat->_time_to_sync;
1239 }
1240
1241 spstat->_time_to_do_cleanups = end_time;
1242 }
1243
1244 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
1245 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1246
1247 // Record how long spent in cleanup tasks.
1248 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
1249
1250 cleanup_end_time = end_time;
1251 }
1252
1253 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
1254 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1255
1256 // Update the vm operation time.
1257 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
1258 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
1259 _max_vmop_time = spstat->_time_to_exec_vmop;
1260 }
1261 // Only the sync time longer than the specified
1262 // PrintSafepointStatisticsTimeout will be printed out right away.
1263 // By default, it is -1 meaning all samples will be put into the list.
1264 if ( PrintSafepointStatisticsTimeout > 0) {
1265 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1266 print_statistics();
1267 }
1268 } else {
1269 // The safepoint statistics will be printed out when the _safepoin_stats
1270 // array fills up.
1271 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
1272 print_statistics();
1273 _cur_stat_index = 0;
1274 } else {
1275 _cur_stat_index++;
1276 }
1277 }
1278 }
1279
1280 void SafepointSynchronize::print_statistics() {
1281 SafepointStats* sstats = _safepoint_stats;
1282
1283 for (int index = 0; index <= _cur_stat_index; index++) {
1284 if (index % 30 == 0) {
1285 print_header();
1286 }
1287 sstats = &_safepoint_stats[index];
1288 tty->print("%.3f: ", sstats->_time_stamp);
1289 tty->print("%-26s ["
1290 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
1291 " ] ",
1292 sstats->_vmop_type == -1 ? "no vm operation" :
1293 VM_Operation::name(sstats->_vmop_type),
1294 sstats->_nof_total_threads,
1295 sstats->_nof_initial_running_threads,
1296 sstats->_nof_threads_wait_to_block);
1297 // "/ MICROUNITS " is to convert the unit from nanos to millis.
1298 tty->print(" ["
1299 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1300 INT64_FORMAT_W(6)INT64_FORMAT_W(6)
1301 INT64_FORMAT_W(6)" ] ",
1302 sstats->_time_to_spin / MICROUNITS,
1303 sstats->_time_to_wait_to_block / MICROUNITS,
1304 sstats->_time_to_sync / MICROUNITS,
1305 sstats->_time_to_do_cleanups / MICROUNITS,
1306 sstats->_time_to_exec_vmop / MICROUNITS);
1307
1308 if (need_to_track_page_armed_status) {
1309 tty->print(INT32_FORMAT" ", sstats->_page_armed);
1310 }
1311 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
1312 }
1313 }
1314
1315 // This method will be called when VM exits. It will first call
1316 // print_statistics to print out the rest of the sampling. Then
1317 // it tries to summarize the sampling.
1318 void SafepointSynchronize::print_stat_on_exit() {
1319 if (_safepoint_stats == NULL) return;
1320
1321 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
1322
1323 // During VM exit, end_statistics may not get called and in that
1324 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
1325 // don't print it out.
1326 // Approximate the vm op time.
1327 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
1328 os::javaTimeNanos() - cleanup_end_time;
1329
1330 if ( PrintSafepointStatisticsTimeout < 0 ||
1331 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
1332 print_statistics();
1333 }
1334 tty->print_cr("");
1335
1336 // Print out polling page sampling status.
1337 if (!need_to_track_page_armed_status) {
1338 if (UseCompilerSafepoints) {
1339 tty->print_cr("Polling page always armed");
1340 }
1341 } else {
1342 tty->print_cr("Defer polling page loop count = %d\n",
1343 DeferPollingPageLoopCount);
1344 }
1345
1346 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
1347 if (_safepoint_reasons[index] != 0) {
1348 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
1349 _safepoint_reasons[index]);
1350 }
1351 }
1352
1353 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
1354 _coalesced_vmop_count);
1355 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
1356 _max_sync_time / MICROUNITS);
1357 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
1358 INT64_FORMAT_W(5)" ms",
1359 _max_vmop_time / MICROUNITS);
1360 }
1361
1362 // ------------------------------------------------------------------------------------------------
1363 // Non-product code
1364
1365 #ifndef PRODUCT
1366
1367 void SafepointSynchronize::print_state() {
1368 if (_state == _not_synchronized) {
1369 tty->print_cr("not synchronized");
1370 } else if (_state == _synchronizing || _state == _synchronized) {
1371 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
1372 "synchronized");
1373
1374 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
1375 cur->safepoint_state()->print();
1376 }
1377 }
1378 }
1379
1380 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
1381 if (ShowSafepointMsgs) {
1382 va_list ap;
1383 va_start(ap, format);
1384 tty->vprint_cr(format, ap);
1385 va_end(ap);
1386 }
1387 }
1388
1389 #endif // !PRODUCT