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annotate src/share/vm/runtime/safepoint.cpp @ 1003:528d98fe1037
6880029: JDK 1.6.0_u14p Application crashed very early
Reviewed-by: never, ysr, acorn
| author | xlu |
|---|---|
| date | Thu, 24 Sep 2009 12:10:46 -0700 |
| parents | 87770dcf831b |
| children | 4b0f2f4918ed |
| rev | line source |
|---|---|
| 0 | 1 /* |
| 579 | 2 * Copyright 1997-2009 Sun Microsystems, Inc. All Rights Reserved. |
| 0 | 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
| 20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
| 21 * have any questions. | |
| 22 * | |
| 23 */ | |
| 24 | |
| 25 # include "incls/_precompiled.incl" | |
| 26 # include "incls/_safepoint.cpp.incl" | |
| 27 | |
| 28 // -------------------------------------------------------------------------------------------------- | |
| 29 // Implementation of Safepoint begin/end | |
| 30 | |
| 31 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; | |
| 32 volatile int SafepointSynchronize::_waiting_to_block = 0; | |
| 33 jlong SafepointSynchronize::_last_safepoint = 0; | |
| 34 volatile int SafepointSynchronize::_safepoint_counter = 0; | |
| 35 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE | |
| 36 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only | |
| 37 static bool timeout_error_printed = false; | |
| 38 | |
| 39 // Roll all threads forward to a safepoint and suspend them all | |
| 40 void SafepointSynchronize::begin() { | |
| 41 | |
| 42 Thread* myThread = Thread::current(); | |
| 43 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); | |
| 44 | |
| 45 _last_safepoint = os::javaTimeNanos(); | |
| 46 | |
| 47 #ifndef SERIALGC | |
| 48 if (UseConcMarkSweepGC) { | |
| 49 // In the future we should investigate whether CMS can use the | |
| 50 // more-general mechanism below. DLD (01/05). | |
| 51 ConcurrentMarkSweepThread::synchronize(false); | |
|
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52 } else if (UseG1GC) { |
| 0 | 53 ConcurrentGCThread::safepoint_synchronize(); |
| 54 } | |
| 55 #endif // SERIALGC | |
| 56 | |
| 57 // By getting the Threads_lock, we assure that no threads are about to start or | |
| 58 // exit. It is released again in SafepointSynchronize::end(). | |
| 59 Threads_lock->lock(); | |
| 60 | |
| 61 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); | |
| 62 | |
| 63 int nof_threads = Threads::number_of_threads(); | |
| 64 | |
| 65 if (TraceSafepoint) { | |
| 66 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); | |
| 67 } | |
| 68 | |
| 69 RuntimeService::record_safepoint_begin(); | |
| 70 | |
| 71 { | |
| 72 MutexLocker mu(Safepoint_lock); | |
| 73 | |
| 74 // Set number of threads to wait for, before we initiate the callbacks | |
| 75 _waiting_to_block = nof_threads; | |
| 76 TryingToBlock = 0 ; | |
| 77 int still_running = nof_threads; | |
| 78 | |
| 79 // Save the starting time, so that it can be compared to see if this has taken | |
| 80 // too long to complete. | |
| 81 jlong safepoint_limit_time; | |
| 82 timeout_error_printed = false; | |
| 83 | |
| 1003 | 84 // PrintSafepointStatisticsTimeout can be specified separately. When |
| 85 // specified, PrintSafepointStatistics will be set to true in | |
| 86 // deferred_initialize_stat method. The initialization has to be done | |
| 87 // early enough to avoid any races. See bug 6880029 for details. | |
| 88 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { | |
| 89 deferred_initialize_stat(); | |
| 90 } | |
| 91 | |
| 0 | 92 // Begin the process of bringing the system to a safepoint. |
| 93 // Java threads can be in several different states and are | |
| 94 // stopped by different mechanisms: | |
| 95 // | |
| 96 // 1. Running interpreted | |
| 97 // The interpeter dispatch table is changed to force it to | |
| 98 // check for a safepoint condition between bytecodes. | |
| 99 // 2. Running in native code | |
| 100 // When returning from the native code, a Java thread must check | |
| 101 // the safepoint _state to see if we must block. If the | |
| 102 // VM thread sees a Java thread in native, it does | |
| 103 // not wait for this thread to block. The order of the memory | |
| 104 // writes and reads of both the safepoint state and the Java | |
| 105 // threads state is critical. In order to guarantee that the | |
| 106 // memory writes are serialized with respect to each other, | |
| 107 // the VM thread issues a memory barrier instruction | |
| 108 // (on MP systems). In order to avoid the overhead of issuing | |
| 109 // a memory barrier for each Java thread making native calls, each Java | |
| 110 // thread performs a write to a single memory page after changing | |
| 111 // the thread state. The VM thread performs a sequence of | |
| 112 // mprotect OS calls which forces all previous writes from all | |
| 113 // Java threads to be serialized. This is done in the | |
| 114 // os::serialize_thread_states() call. This has proven to be | |
| 115 // much more efficient than executing a membar instruction | |
| 116 // on every call to native code. | |
| 117 // 3. Running compiled Code | |
| 118 // Compiled code reads a global (Safepoint Polling) page that | |
| 119 // is set to fault if we are trying to get to a safepoint. | |
| 120 // 4. Blocked | |
| 121 // A thread which is blocked will not be allowed to return from the | |
| 122 // block condition until the safepoint operation is complete. | |
| 123 // 5. In VM or Transitioning between states | |
| 124 // If a Java thread is currently running in the VM or transitioning | |
| 125 // between states, the safepointing code will wait for the thread to | |
| 126 // block itself when it attempts transitions to a new state. | |
| 127 // | |
| 128 _state = _synchronizing; | |
| 129 OrderAccess::fence(); | |
| 130 | |
| 131 // Flush all thread states to memory | |
| 132 if (!UseMembar) { | |
| 133 os::serialize_thread_states(); | |
| 134 } | |
| 135 | |
| 136 // Make interpreter safepoint aware | |
| 137 Interpreter::notice_safepoints(); | |
| 138 | |
| 139 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) { | |
| 140 // Make polling safepoint aware | |
| 141 guarantee (PageArmed == 0, "invariant") ; | |
| 142 PageArmed = 1 ; | |
| 143 os::make_polling_page_unreadable(); | |
| 144 } | |
| 145 | |
| 146 // Consider using active_processor_count() ... but that call is expensive. | |
| 147 int ncpus = os::processor_count() ; | |
| 148 | |
| 149 #ifdef ASSERT | |
| 150 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { | |
| 151 assert(cur->safepoint_state()->is_running(), "Illegal initial state"); | |
| 152 } | |
| 153 #endif // ASSERT | |
| 154 | |
| 155 if (SafepointTimeout) | |
| 156 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; | |
| 157 | |
| 158 // Iterate through all threads until it have been determined how to stop them all at a safepoint | |
| 159 unsigned int iterations = 0; | |
| 160 int steps = 0 ; | |
| 161 while(still_running > 0) { | |
| 162 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { | |
| 163 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); | |
| 164 ThreadSafepointState *cur_state = cur->safepoint_state(); | |
| 165 if (cur_state->is_running()) { | |
| 166 cur_state->examine_state_of_thread(); | |
| 167 if (!cur_state->is_running()) { | |
| 168 still_running--; | |
| 169 // consider adjusting steps downward: | |
| 170 // steps = 0 | |
| 171 // steps -= NNN | |
| 172 // steps >>= 1 | |
| 173 // steps = MIN(steps, 2000-100) | |
| 174 // if (iterations != 0) steps -= NNN | |
| 175 } | |
| 176 if (TraceSafepoint && Verbose) cur_state->print(); | |
| 177 } | |
| 178 } | |
| 179 | |
| 1003 | 180 if (PrintSafepointStatistics && iterations == 0) { |
| 0 | 181 begin_statistics(nof_threads, still_running); |
| 182 } | |
| 183 | |
| 184 if (still_running > 0) { | |
| 185 // Check for if it takes to long | |
| 186 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { | |
| 187 print_safepoint_timeout(_spinning_timeout); | |
| 188 } | |
| 189 | |
| 190 // Spin to avoid context switching. | |
| 191 // There's a tension between allowing the mutators to run (and rendezvous) | |
| 192 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that | |
| 193 // a mutator might otherwise use profitably to reach a safepoint. Excessive | |
| 194 // spinning by the VM thread on a saturated system can increase rendezvous latency. | |
| 195 // Blocking or yielding incur their own penalties in the form of context switching | |
| 196 // and the resultant loss of $ residency. | |
| 197 // | |
| 198 // Further complicating matters is that yield() does not work as naively expected | |
| 199 // on many platforms -- yield() does not guarantee that any other ready threads | |
| 200 // will run. As such we revert yield_all() after some number of iterations. | |
| 201 // Yield_all() is implemented as a short unconditional sleep on some platforms. | |
| 202 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping | |
| 203 // can actually increase the time it takes the VM thread to detect that a system-wide | |
| 204 // stop-the-world safepoint has been reached. In a pathological scenario such as that | |
| 205 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. | |
| 206 // In that case the mutators will be stalled waiting for the safepoint to complete and the | |
| 207 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread | |
| 208 // will eventually wake up and detect that all mutators are safe, at which point | |
| 209 // we'll again make progress. | |
| 210 // | |
| 211 // Beware too that that the VMThread typically runs at elevated priority. | |
| 212 // Its default priority is higher than the default mutator priority. | |
| 213 // Obviously, this complicates spinning. | |
| 214 // | |
| 215 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). | |
| 216 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. | |
| 217 // | |
| 218 // See the comments in synchronizer.cpp for additional remarks on spinning. | |
| 219 // | |
| 220 // In the future we might: | |
| 221 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning. | |
| 222 // This is tricky as the path used by a thread exiting the JVM (say on | |
| 223 // on JNI call-out) simply stores into its state field. The burden | |
| 224 // is placed on the VM thread, which must poll (spin). | |
| 225 // 2. Find something useful to do while spinning. If the safepoint is GC-related | |
| 226 // we might aggressively scan the stacks of threads that are already safe. | |
| 227 // 3. Use Solaris schedctl to examine the state of the still-running mutators. | |
| 228 // If all the mutators are ONPROC there's no reason to sleep or yield. | |
| 229 // 4. YieldTo() any still-running mutators that are ready but OFFPROC. | |
| 230 // 5. Check system saturation. If the system is not fully saturated then | |
| 231 // simply spin and avoid sleep/yield. | |
| 232 // 6. As still-running mutators rendezvous they could unpark the sleeping | |
| 233 // VMthread. This works well for still-running mutators that become | |
| 234 // safe. The VMthread must still poll for mutators that call-out. | |
| 235 // 7. Drive the policy on time-since-begin instead of iterations. | |
| 236 // 8. Consider making the spin duration a function of the # of CPUs: | |
| 237 // Spin = (((ncpus-1) * M) + K) + F(still_running) | |
| 238 // Alternately, instead of counting iterations of the outer loop | |
| 239 // we could count the # of threads visited in the inner loop, above. | |
| 240 // 9. On windows consider using the return value from SwitchThreadTo() | |
| 241 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. | |
| 242 | |
| 243 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) { | |
| 244 guarantee (PageArmed == 0, "invariant") ; | |
| 245 PageArmed = 1 ; | |
| 246 os::make_polling_page_unreadable(); | |
| 247 } | |
| 248 | |
| 249 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or | |
| 250 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) | |
| 251 ++steps ; | |
| 252 if (ncpus > 1 && steps < SafepointSpinBeforeYield) { | |
| 253 SpinPause() ; // MP-Polite spin | |
| 254 } else | |
| 255 if (steps < DeferThrSuspendLoopCount) { | |
| 256 os::NakedYield() ; | |
| 257 } else { | |
| 258 os::yield_all(steps) ; | |
| 259 // Alternately, the VM thread could transiently depress its scheduling priority or | |
| 260 // transiently increase the priority of the tardy mutator(s). | |
| 261 } | |
| 262 | |
| 263 iterations ++ ; | |
| 264 } | |
| 265 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); | |
| 266 } | |
| 267 assert(still_running == 0, "sanity check"); | |
| 268 | |
| 269 if (PrintSafepointStatistics) { | |
| 270 update_statistics_on_spin_end(); | |
| 271 } | |
| 272 | |
| 273 // wait until all threads are stopped | |
| 274 while (_waiting_to_block > 0) { | |
| 275 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); | |
| 276 if (!SafepointTimeout || timeout_error_printed) { | |
| 277 Safepoint_lock->wait(true); // true, means with no safepoint checks | |
| 278 } else { | |
| 279 // Compute remaining time | |
| 280 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); | |
| 281 | |
| 282 // If there is no remaining time, then there is an error | |
| 283 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { | |
| 284 print_safepoint_timeout(_blocking_timeout); | |
| 285 } | |
| 286 } | |
| 287 } | |
| 288 assert(_waiting_to_block == 0, "sanity check"); | |
| 289 | |
| 290 #ifndef PRODUCT | |
| 291 if (SafepointTimeout) { | |
| 292 jlong current_time = os::javaTimeNanos(); | |
| 293 if (safepoint_limit_time < current_time) { | |
| 294 tty->print_cr("# SafepointSynchronize: Finished after " | |
| 295 INT64_FORMAT_W(6) " ms", | |
| 296 ((current_time - safepoint_limit_time) / MICROUNITS + | |
| 297 SafepointTimeoutDelay)); | |
| 298 } | |
| 299 } | |
| 300 #endif | |
| 301 | |
| 302 assert((_safepoint_counter & 0x1) == 0, "must be even"); | |
| 303 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); | |
| 304 _safepoint_counter ++; | |
| 305 | |
| 306 // Record state | |
| 307 _state = _synchronized; | |
| 308 | |
| 309 OrderAccess::fence(); | |
| 310 | |
| 311 if (TraceSafepoint) { | |
| 312 VM_Operation *op = VMThread::vm_operation(); | |
| 313 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); | |
| 314 } | |
| 315 | |
| 316 RuntimeService::record_safepoint_synchronized(); | |
| 317 if (PrintSafepointStatistics) { | |
| 318 update_statistics_on_sync_end(os::javaTimeNanos()); | |
| 319 } | |
| 320 | |
| 321 // Call stuff that needs to be run when a safepoint is just about to be completed | |
| 322 do_cleanup_tasks(); | |
| 323 } | |
| 324 } | |
| 325 | |
| 326 // Wake up all threads, so they are ready to resume execution after the safepoint | |
| 327 // operation has been carried out | |
| 328 void SafepointSynchronize::end() { | |
| 329 | |
| 330 assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); | |
| 331 assert((_safepoint_counter & 0x1) == 1, "must be odd"); | |
| 332 _safepoint_counter ++; | |
| 333 // memory fence isn't required here since an odd _safepoint_counter | |
| 334 // value can do no harm and a fence is issued below anyway. | |
| 335 | |
| 336 DEBUG_ONLY(Thread* myThread = Thread::current();) | |
| 337 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); | |
| 338 | |
| 339 if (PrintSafepointStatistics) { | |
| 340 end_statistics(os::javaTimeNanos()); | |
| 341 } | |
| 342 | |
| 343 #ifdef ASSERT | |
| 344 // A pending_exception cannot be installed during a safepoint. The threads | |
| 345 // may install an async exception after they come back from a safepoint into | |
| 346 // pending_exception after they unblock. But that should happen later. | |
| 347 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { | |
| 348 assert (!(cur->has_pending_exception() && | |
| 349 cur->safepoint_state()->is_at_poll_safepoint()), | |
| 350 "safepoint installed a pending exception"); | |
| 351 } | |
| 352 #endif // ASSERT | |
| 353 | |
| 354 if (PageArmed) { | |
| 355 // Make polling safepoint aware | |
| 356 os::make_polling_page_readable(); | |
| 357 PageArmed = 0 ; | |
| 358 } | |
| 359 | |
| 360 // Remove safepoint check from interpreter | |
| 361 Interpreter::ignore_safepoints(); | |
| 362 | |
| 363 { | |
| 364 MutexLocker mu(Safepoint_lock); | |
| 365 | |
| 366 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); | |
| 367 | |
| 368 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method | |
| 369 // when they get restarted. | |
| 370 _state = _not_synchronized; | |
| 371 OrderAccess::fence(); | |
| 372 | |
| 373 if (TraceSafepoint) { | |
| 374 tty->print_cr("Leaving safepoint region"); | |
| 375 } | |
| 376 | |
| 377 // Start suspended threads | |
| 378 for(JavaThread *current = Threads::first(); current; current = current->next()) { | |
| 605 | 379 // A problem occurring on Solaris is when attempting to restart threads |
| 0 | 380 // the first #cpus - 1 go well, but then the VMThread is preempted when we get |
| 381 // to the next one (since it has been running the longest). We then have | |
| 382 // to wait for a cpu to become available before we can continue restarting | |
| 383 // threads. | |
| 384 // FIXME: This causes the performance of the VM to degrade when active and with | |
| 385 // large numbers of threads. Apparently this is due to the synchronous nature | |
| 386 // of suspending threads. | |
| 387 // | |
| 388 // TODO-FIXME: the comments above are vestigial and no longer apply. | |
| 389 // Furthermore, using solaris' schedctl in this particular context confers no benefit | |
| 390 if (VMThreadHintNoPreempt) { | |
| 391 os::hint_no_preempt(); | |
| 392 } | |
| 393 ThreadSafepointState* cur_state = current->safepoint_state(); | |
| 394 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); | |
| 395 cur_state->restart(); | |
| 396 assert(cur_state->is_running(), "safepoint state has not been reset"); | |
| 397 } | |
| 398 | |
| 399 RuntimeService::record_safepoint_end(); | |
| 400 | |
| 401 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads | |
| 402 // blocked in signal_thread_blocked | |
| 403 Threads_lock->unlock(); | |
| 404 | |
| 405 } | |
| 406 #ifndef SERIALGC | |
| 407 // If there are any concurrent GC threads resume them. | |
| 408 if (UseConcMarkSweepGC) { | |
| 409 ConcurrentMarkSweepThread::desynchronize(false); | |
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410 } else if (UseG1GC) { |
| 0 | 411 ConcurrentGCThread::safepoint_desynchronize(); |
| 412 } | |
| 413 #endif // SERIALGC | |
| 414 } | |
| 415 | |
| 416 bool SafepointSynchronize::is_cleanup_needed() { | |
| 417 // Need a safepoint if some inline cache buffers is non-empty | |
| 418 if (!InlineCacheBuffer::is_empty()) return true; | |
| 419 return false; | |
| 420 } | |
| 421 | |
| 422 jlong CounterDecay::_last_timestamp = 0; | |
| 423 | |
| 424 static void do_method(methodOop m) { | |
| 425 m->invocation_counter()->decay(); | |
| 426 } | |
| 427 | |
| 428 void CounterDecay::decay() { | |
| 429 _last_timestamp = os::javaTimeMillis(); | |
| 430 | |
| 431 // This operation is going to be performed only at the end of a safepoint | |
| 432 // and hence GC's will not be going on, all Java mutators are suspended | |
| 433 // at this point and hence SystemDictionary_lock is also not needed. | |
| 434 assert(SafepointSynchronize::is_at_safepoint(), "can only be executed at a safepoint"); | |
| 435 int nclasses = SystemDictionary::number_of_classes(); | |
| 436 double classes_per_tick = nclasses * (CounterDecayMinIntervalLength * 1e-3 / | |
| 437 CounterHalfLifeTime); | |
| 438 for (int i = 0; i < classes_per_tick; i++) { | |
| 439 klassOop k = SystemDictionary::try_get_next_class(); | |
| 440 if (k != NULL && k->klass_part()->oop_is_instance()) { | |
| 441 instanceKlass::cast(k)->methods_do(do_method); | |
| 442 } | |
| 443 } | |
| 444 } | |
| 445 | |
| 446 // Various cleaning tasks that should be done periodically at safepoints | |
| 447 void SafepointSynchronize::do_cleanup_tasks() { | |
| 448 jlong cleanup_time; | |
| 449 | |
| 450 // Update fat-monitor pool, since this is a safepoint. | |
| 451 if (TraceSafepoint) { | |
| 452 cleanup_time = os::javaTimeNanos(); | |
| 453 } | |
| 454 | |
| 455 ObjectSynchronizer::deflate_idle_monitors(); | |
| 456 InlineCacheBuffer::update_inline_caches(); | |
| 457 if(UseCounterDecay && CounterDecay::is_decay_needed()) { | |
| 458 CounterDecay::decay(); | |
| 459 } | |
| 460 NMethodSweeper::sweep(); | |
| 461 | |
| 462 if (TraceSafepoint) { | |
| 463 tty->print_cr("do_cleanup_tasks takes "INT64_FORMAT_W(6) "ms", | |
| 464 (os::javaTimeNanos() - cleanup_time) / MICROUNITS); | |
| 465 } | |
| 466 } | |
| 467 | |
| 468 | |
| 469 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { | |
| 470 switch(state) { | |
| 471 case _thread_in_native: | |
| 472 // native threads are safe if they have no java stack or have walkable stack | |
| 473 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); | |
| 474 | |
| 475 // blocked threads should have already have walkable stack | |
| 476 case _thread_blocked: | |
| 477 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); | |
| 478 return true; | |
| 479 | |
| 480 default: | |
| 481 return false; | |
| 482 } | |
| 483 } | |
| 484 | |
| 485 | |
| 486 // ------------------------------------------------------------------------------------------------------- | |
| 487 // Implementation of Safepoint callback point | |
| 488 | |
| 489 void SafepointSynchronize::block(JavaThread *thread) { | |
| 490 assert(thread != NULL, "thread must be set"); | |
| 491 assert(thread->is_Java_thread(), "not a Java thread"); | |
| 492 | |
| 493 // Threads shouldn't block if they are in the middle of printing, but... | |
| 494 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); | |
| 495 | |
| 496 // Only bail from the block() call if the thread is gone from the | |
| 497 // thread list; starting to exit should still block. | |
| 498 if (thread->is_terminated()) { | |
| 499 // block current thread if we come here from native code when VM is gone | |
| 500 thread->block_if_vm_exited(); | |
| 501 | |
| 502 // otherwise do nothing | |
| 503 return; | |
| 504 } | |
| 505 | |
| 506 JavaThreadState state = thread->thread_state(); | |
| 507 thread->frame_anchor()->make_walkable(thread); | |
| 508 | |
| 509 // Check that we have a valid thread_state at this point | |
| 510 switch(state) { | |
| 511 case _thread_in_vm_trans: | |
| 512 case _thread_in_Java: // From compiled code | |
| 513 | |
| 514 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, | |
| 515 // we pretend we are still in the VM. | |
| 516 thread->set_thread_state(_thread_in_vm); | |
| 517 | |
| 518 if (is_synchronizing()) { | |
| 519 Atomic::inc (&TryingToBlock) ; | |
| 520 } | |
| 521 | |
| 522 // We will always be holding the Safepoint_lock when we are examine the state | |
| 523 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and | |
| 524 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code | |
| 525 Safepoint_lock->lock_without_safepoint_check(); | |
| 526 if (is_synchronizing()) { | |
| 527 // Decrement the number of threads to wait for and signal vm thread | |
| 528 assert(_waiting_to_block > 0, "sanity check"); | |
| 529 _waiting_to_block--; | |
| 530 thread->safepoint_state()->set_has_called_back(true); | |
| 531 | |
| 532 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread | |
| 533 if (_waiting_to_block == 0) { | |
| 534 Safepoint_lock->notify_all(); | |
| 535 } | |
| 536 } | |
| 537 | |
| 538 // We transition the thread to state _thread_blocked here, but | |
| 539 // we can't do our usual check for external suspension and then | |
| 540 // self-suspend after the lock_without_safepoint_check() call | |
| 541 // below because we are often called during transitions while | |
| 542 // we hold different locks. That would leave us suspended while | |
| 543 // holding a resource which results in deadlocks. | |
| 544 thread->set_thread_state(_thread_blocked); | |
| 545 Safepoint_lock->unlock(); | |
| 546 | |
| 547 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during | |
| 548 // the entire safepoint, the threads will all line up here during the safepoint. | |
| 549 Threads_lock->lock_without_safepoint_check(); | |
| 550 // restore original state. This is important if the thread comes from compiled code, so it | |
| 551 // will continue to execute with the _thread_in_Java state. | |
| 552 thread->set_thread_state(state); | |
| 553 Threads_lock->unlock(); | |
| 554 break; | |
| 555 | |
| 556 case _thread_in_native_trans: | |
| 557 case _thread_blocked_trans: | |
| 558 case _thread_new_trans: | |
| 559 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { | |
| 560 thread->print_thread_state(); | |
| 561 fatal("Deadlock in safepoint code. " | |
| 562 "Should have called back to the VM before blocking."); | |
| 563 } | |
| 564 | |
| 565 // We transition the thread to state _thread_blocked here, but | |
| 566 // we can't do our usual check for external suspension and then | |
| 567 // self-suspend after the lock_without_safepoint_check() call | |
| 568 // below because we are often called during transitions while | |
| 569 // we hold different locks. That would leave us suspended while | |
| 570 // holding a resource which results in deadlocks. | |
| 571 thread->set_thread_state(_thread_blocked); | |
| 572 | |
| 573 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, | |
| 574 // the safepoint code might still be waiting for it to block. We need to change the state here, | |
| 575 // so it can see that it is at a safepoint. | |
| 576 | |
| 577 // Block until the safepoint operation is completed. | |
| 578 Threads_lock->lock_without_safepoint_check(); | |
| 579 | |
| 580 // Restore state | |
| 581 thread->set_thread_state(state); | |
| 582 | |
| 583 Threads_lock->unlock(); | |
| 584 break; | |
| 585 | |
| 586 default: | |
| 587 fatal1("Illegal threadstate encountered: %d", state); | |
| 588 } | |
| 589 | |
| 590 // Check for pending. async. exceptions or suspends - except if the | |
| 591 // thread was blocked inside the VM. has_special_runtime_exit_condition() | |
| 592 // is called last since it grabs a lock and we only want to do that when | |
| 593 // we must. | |
| 594 // | |
| 595 // Note: we never deliver an async exception at a polling point as the | |
| 596 // compiler may not have an exception handler for it. The polling | |
| 597 // code will notice the async and deoptimize and the exception will | |
| 598 // be delivered. (Polling at a return point is ok though). Sure is | |
| 599 // a lot of bother for a deprecated feature... | |
| 600 // | |
| 601 // We don't deliver an async exception if the thread state is | |
| 602 // _thread_in_native_trans so JNI functions won't be called with | |
| 603 // a surprising pending exception. If the thread state is going back to java, | |
| 604 // async exception is checked in check_special_condition_for_native_trans(). | |
| 605 | |
| 606 if (state != _thread_blocked_trans && | |
| 607 state != _thread_in_vm_trans && | |
| 608 thread->has_special_runtime_exit_condition()) { | |
| 609 thread->handle_special_runtime_exit_condition( | |
| 610 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); | |
| 611 } | |
| 612 } | |
| 613 | |
| 614 // ------------------------------------------------------------------------------------------------------ | |
| 615 // Exception handlers | |
| 616 | |
| 617 #ifndef PRODUCT | |
| 618 #ifdef _LP64 | |
| 619 #define PTR_PAD "" | |
| 620 #else | |
| 621 #define PTR_PAD " " | |
| 622 #endif | |
| 623 | |
| 624 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) { | |
| 625 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false; | |
| 626 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s", | |
| 627 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', | |
| 628 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); | |
| 629 } | |
| 630 | |
| 631 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) { | |
| 632 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false; | |
| 633 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s", | |
| 634 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', | |
| 635 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); | |
| 636 } | |
| 637 | |
| 638 #ifdef SPARC | |
| 639 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) { | |
| 640 #ifdef _LP64 | |
| 641 tty->print_cr("--------+------address-----+------before-----------+-------after----------+"); | |
| 642 const int incr = 1; // Increment to skip a long, in units of intptr_t | |
| 643 #else | |
| 644 tty->print_cr("--------+--address-+------before-----------+-------after----------+"); | |
| 645 const int incr = 2; // Increment to skip a long, in units of intptr_t | |
| 646 #endif | |
| 647 tty->print_cr("---SP---|"); | |
| 648 for( int i=0; i<16; i++ ) { | |
| 649 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } | |
| 650 tty->print_cr("--------|"); | |
| 651 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) { | |
| 652 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } | |
| 653 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); | |
| 654 tty->print_cr("--------|"); | |
| 655 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; | |
| 656 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; | |
| 657 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; | |
| 658 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; | |
| 659 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp); | |
| 660 old_sp += incr; new_sp += incr; was_oops += incr; | |
| 661 // Skip the floats | |
| 662 tty->print_cr("--Float-|"PTR_FORMAT,new_sp); | |
| 663 tty->print_cr("---FP---|"); | |
| 664 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32; | |
| 665 for( int i2=0; i2<16; i2++ ) { | |
| 666 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } | |
| 667 tty->print_cr(""); | |
| 668 } | |
| 669 #endif // SPARC | |
| 670 #endif // PRODUCT | |
| 671 | |
| 672 | |
| 673 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { | |
| 674 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); | |
| 675 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); | |
| 676 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); | |
| 677 | |
| 678 // Uncomment this to get some serious before/after printing of the | |
| 679 // Sparc safepoint-blob frame structure. | |
| 680 /* | |
| 681 intptr_t* sp = thread->last_Java_sp(); | |
| 682 intptr_t stack_copy[150]; | |
| 683 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i]; | |
| 684 bool was_oops[150]; | |
| 685 for( int i=0; i<150; i++ ) | |
| 686 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false; | |
| 687 */ | |
| 688 | |
| 689 if (ShowSafepointMsgs) { | |
| 690 tty->print("handle_polling_page_exception: "); | |
| 691 } | |
| 692 | |
| 693 if (PrintSafepointStatistics) { | |
| 694 inc_page_trap_count(); | |
| 695 } | |
| 696 | |
| 697 ThreadSafepointState* state = thread->safepoint_state(); | |
| 698 | |
| 699 state->handle_polling_page_exception(); | |
| 700 // print_me(sp,stack_copy,was_oops); | |
| 701 } | |
| 702 | |
| 703 | |
| 704 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { | |
| 705 if (!timeout_error_printed) { | |
| 706 timeout_error_printed = true; | |
| 707 // Print out the thread infor which didn't reach the safepoint for debugging | |
| 708 // purposes (useful when there are lots of threads in the debugger). | |
| 709 tty->print_cr(""); | |
| 710 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); | |
| 711 if (reason == _spinning_timeout) { | |
| 712 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); | |
| 713 } else if (reason == _blocking_timeout) { | |
| 714 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); | |
| 715 } | |
| 716 | |
| 717 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); | |
| 718 ThreadSafepointState *cur_state; | |
| 719 ResourceMark rm; | |
| 720 for(JavaThread *cur_thread = Threads::first(); cur_thread; | |
| 721 cur_thread = cur_thread->next()) { | |
| 722 cur_state = cur_thread->safepoint_state(); | |
| 723 | |
| 724 if (cur_thread->thread_state() != _thread_blocked && | |
| 725 ((reason == _spinning_timeout && cur_state->is_running()) || | |
| 726 (reason == _blocking_timeout && !cur_state->has_called_back()))) { | |
| 727 tty->print("# "); | |
| 728 cur_thread->print(); | |
| 729 tty->print_cr(""); | |
| 730 } | |
| 731 } | |
| 732 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); | |
| 733 } | |
| 734 | |
| 735 // To debug the long safepoint, specify both DieOnSafepointTimeout & | |
| 736 // ShowMessageBoxOnError. | |
| 737 if (DieOnSafepointTimeout) { | |
| 738 char msg[1024]; | |
| 739 VM_Operation *op = VMThread::vm_operation(); | |
|
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740 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", |
| 0 | 741 SafepointTimeoutDelay, |
| 742 op != NULL ? op->name() : "no vm operation"); | |
| 743 fatal(msg); | |
| 744 } | |
| 745 } | |
| 746 | |
| 747 | |
| 748 // ------------------------------------------------------------------------------------------------------- | |
| 749 // Implementation of ThreadSafepointState | |
| 750 | |
| 751 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { | |
| 752 _thread = thread; | |
| 753 _type = _running; | |
| 754 _has_called_back = false; | |
| 755 _at_poll_safepoint = false; | |
| 756 } | |
| 757 | |
| 758 void ThreadSafepointState::create(JavaThread *thread) { | |
| 759 ThreadSafepointState *state = new ThreadSafepointState(thread); | |
| 760 thread->set_safepoint_state(state); | |
| 761 } | |
| 762 | |
| 763 void ThreadSafepointState::destroy(JavaThread *thread) { | |
| 764 if (thread->safepoint_state()) { | |
| 765 delete(thread->safepoint_state()); | |
| 766 thread->set_safepoint_state(NULL); | |
| 767 } | |
| 768 } | |
| 769 | |
| 770 void ThreadSafepointState::examine_state_of_thread() { | |
| 771 assert(is_running(), "better be running or just have hit safepoint poll"); | |
| 772 | |
| 773 JavaThreadState state = _thread->thread_state(); | |
| 774 | |
| 775 // Check for a thread that is suspended. Note that thread resume tries | |
| 776 // to grab the Threads_lock which we own here, so a thread cannot be | |
| 777 // resumed during safepoint synchronization. | |
| 778 | |
| 979 | 779 // We check to see if this thread is suspended without locking to |
| 780 // avoid deadlocking with a third thread that is waiting for this | |
| 781 // thread to be suspended. The third thread can notice the safepoint | |
| 782 // that we're trying to start at the beginning of its SR_lock->wait() | |
| 783 // call. If that happens, then the third thread will block on the | |
| 784 // safepoint while still holding the underlying SR_lock. We won't be | |
| 785 // able to get the SR_lock and we'll deadlock. | |
| 786 // | |
| 787 // We don't need to grab the SR_lock here for two reasons: | |
| 788 // 1) The suspend flags are both volatile and are set with an | |
| 789 // Atomic::cmpxchg() call so we should see the suspended | |
| 790 // state right away. | |
| 791 // 2) We're being called from the safepoint polling loop; if | |
| 792 // we don't see the suspended state on this iteration, then | |
| 793 // we'll come around again. | |
| 794 // | |
| 795 bool is_suspended = _thread->is_ext_suspended(); | |
| 0 | 796 if (is_suspended) { |
| 797 roll_forward(_at_safepoint); | |
| 798 return; | |
| 799 } | |
| 800 | |
| 801 // Some JavaThread states have an initial safepoint state of | |
| 802 // running, but are actually at a safepoint. We will happily | |
| 803 // agree and update the safepoint state here. | |
| 804 if (SafepointSynchronize::safepoint_safe(_thread, state)) { | |
| 805 roll_forward(_at_safepoint); | |
| 806 return; | |
| 807 } | |
| 808 | |
| 809 if (state == _thread_in_vm) { | |
| 810 roll_forward(_call_back); | |
| 811 return; | |
| 812 } | |
| 813 | |
| 814 // All other thread states will continue to run until they | |
| 815 // transition and self-block in state _blocked | |
| 816 // Safepoint polling in compiled code causes the Java threads to do the same. | |
| 817 // Note: new threads may require a malloc so they must be allowed to finish | |
| 818 | |
| 819 assert(is_running(), "examine_state_of_thread on non-running thread"); | |
| 820 return; | |
| 821 } | |
| 822 | |
| 823 // Returns true is thread could not be rolled forward at present position. | |
| 824 void ThreadSafepointState::roll_forward(suspend_type type) { | |
| 825 _type = type; | |
| 826 | |
| 827 switch(_type) { | |
| 828 case _at_safepoint: | |
| 829 SafepointSynchronize::signal_thread_at_safepoint(); | |
| 830 break; | |
| 831 | |
| 832 case _call_back: | |
| 833 set_has_called_back(false); | |
| 834 break; | |
| 835 | |
| 836 case _running: | |
| 837 default: | |
| 838 ShouldNotReachHere(); | |
| 839 } | |
| 840 } | |
| 841 | |
| 842 void ThreadSafepointState::restart() { | |
| 843 switch(type()) { | |
| 844 case _at_safepoint: | |
| 845 case _call_back: | |
| 846 break; | |
| 847 | |
| 848 case _running: | |
| 849 default: | |
| 850 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d", | |
| 851 _thread, _type); | |
| 852 _thread->print(); | |
| 853 ShouldNotReachHere(); | |
| 854 } | |
| 855 _type = _running; | |
| 856 set_has_called_back(false); | |
| 857 } | |
| 858 | |
| 859 | |
| 860 void ThreadSafepointState::print_on(outputStream *st) const { | |
| 861 const char *s; | |
| 862 | |
| 863 switch(_type) { | |
| 864 case _running : s = "_running"; break; | |
| 865 case _at_safepoint : s = "_at_safepoint"; break; | |
| 866 case _call_back : s = "_call_back"; break; | |
| 867 default: | |
| 868 ShouldNotReachHere(); | |
| 869 } | |
| 870 | |
| 871 st->print_cr("Thread: " INTPTR_FORMAT | |
| 872 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", | |
| 873 _thread, _thread->osthread()->thread_id(), s, _has_called_back, | |
| 874 _at_poll_safepoint); | |
| 875 | |
| 876 _thread->print_thread_state_on(st); | |
| 877 } | |
| 878 | |
| 879 | |
| 880 // --------------------------------------------------------------------------------------------------------------------- | |
| 881 | |
| 882 // Block the thread at the safepoint poll or poll return. | |
| 883 void ThreadSafepointState::handle_polling_page_exception() { | |
| 884 | |
| 885 // Check state. block() will set thread state to thread_in_vm which will | |
| 886 // cause the safepoint state _type to become _call_back. | |
| 887 assert(type() == ThreadSafepointState::_running, | |
| 888 "polling page exception on thread not running state"); | |
| 889 | |
| 890 // Step 1: Find the nmethod from the return address | |
| 891 if (ShowSafepointMsgs && Verbose) { | |
| 892 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); | |
| 893 } | |
| 894 address real_return_addr = thread()->saved_exception_pc(); | |
| 895 | |
| 896 CodeBlob *cb = CodeCache::find_blob(real_return_addr); | |
| 897 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); | |
| 898 nmethod* nm = (nmethod*)cb; | |
| 899 | |
| 900 // Find frame of caller | |
| 901 frame stub_fr = thread()->last_frame(); | |
| 902 CodeBlob* stub_cb = stub_fr.cb(); | |
| 903 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); | |
| 904 RegisterMap map(thread(), true); | |
| 905 frame caller_fr = stub_fr.sender(&map); | |
| 906 | |
| 907 // Should only be poll_return or poll | |
| 908 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); | |
| 909 | |
| 910 // This is a poll immediately before a return. The exception handling code | |
| 911 // has already had the effect of causing the return to occur, so the execution | |
| 912 // will continue immediately after the call. In addition, the oopmap at the | |
| 913 // return point does not mark the return value as an oop (if it is), so | |
| 914 // it needs a handle here to be updated. | |
| 915 if( nm->is_at_poll_return(real_return_addr) ) { | |
| 916 // See if return type is an oop. | |
| 917 bool return_oop = nm->method()->is_returning_oop(); | |
| 918 Handle return_value; | |
| 919 if (return_oop) { | |
| 920 // The oop result has been saved on the stack together with all | |
| 921 // the other registers. In order to preserve it over GCs we need | |
| 922 // to keep it in a handle. | |
| 923 oop result = caller_fr.saved_oop_result(&map); | |
| 924 assert(result == NULL || result->is_oop(), "must be oop"); | |
| 925 return_value = Handle(thread(), result); | |
| 926 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); | |
| 927 } | |
| 928 | |
| 929 // Block the thread | |
| 930 SafepointSynchronize::block(thread()); | |
| 931 | |
| 932 // restore oop result, if any | |
| 933 if (return_oop) { | |
| 934 caller_fr.set_saved_oop_result(&map, return_value()); | |
| 935 } | |
| 936 } | |
| 937 | |
| 938 // This is a safepoint poll. Verify the return address and block. | |
| 939 else { | |
| 940 set_at_poll_safepoint(true); | |
| 941 | |
| 942 // verify the blob built the "return address" correctly | |
| 943 assert(real_return_addr == caller_fr.pc(), "must match"); | |
| 944 | |
| 945 // Block the thread | |
| 946 SafepointSynchronize::block(thread()); | |
| 947 set_at_poll_safepoint(false); | |
| 948 | |
| 949 // If we have a pending async exception deoptimize the frame | |
| 950 // as otherwise we may never deliver it. | |
| 951 if (thread()->has_async_condition()) { | |
| 952 ThreadInVMfromJavaNoAsyncException __tiv(thread()); | |
| 953 VM_DeoptimizeFrame deopt(thread(), caller_fr.id()); | |
| 954 VMThread::execute(&deopt); | |
| 955 } | |
| 956 | |
| 957 // If an exception has been installed we must check for a pending deoptimization | |
| 958 // Deoptimize frame if exception has been thrown. | |
| 959 | |
| 960 if (thread()->has_pending_exception() ) { | |
| 961 RegisterMap map(thread(), true); | |
| 962 frame caller_fr = stub_fr.sender(&map); | |
| 963 if (caller_fr.is_deoptimized_frame()) { | |
| 964 // The exception patch will destroy registers that are still | |
| 965 // live and will be needed during deoptimization. Defer the | |
| 966 // Async exception should have defered the exception until the | |
| 967 // next safepoint which will be detected when we get into | |
| 968 // the interpreter so if we have an exception now things | |
| 969 // are messed up. | |
| 970 | |
| 971 fatal("Exception installed and deoptimization is pending"); | |
| 972 } | |
| 973 } | |
| 974 } | |
| 975 } | |
| 976 | |
| 977 | |
| 978 // | |
| 979 // Statistics & Instrumentations | |
| 980 // | |
| 981 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; | |
| 982 int SafepointSynchronize::_cur_stat_index = 0; | |
| 983 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; | |
| 984 julong SafepointSynchronize::_coalesced_vmop_count = 0; | |
| 985 jlong SafepointSynchronize::_max_sync_time = 0; | |
| 986 | |
| 987 // last_safepoint_start_time records the start time of last safepoint. | |
| 988 static jlong last_safepoint_start_time = 0; | |
| 989 static jlong sync_end_time = 0; | |
| 990 static bool need_to_track_page_armed_status = false; | |
| 991 static bool init_done = false; | |
| 992 | |
| 993 void SafepointSynchronize::deferred_initialize_stat() { | |
| 994 if (init_done) return; | |
| 995 | |
| 996 if (PrintSafepointStatisticsCount <= 0) { | |
| 997 fatal("Wrong PrintSafepointStatisticsCount"); | |
| 998 } | |
| 999 | |
| 1000 // If PrintSafepointStatisticsTimeout is specified, the statistics data will | |
| 1001 // be printed right away, in which case, _safepoint_stats will regress to | |
| 1002 // a single element array. Otherwise, it is a circular ring buffer with default | |
| 1003 // size of PrintSafepointStatisticsCount. | |
| 1004 int stats_array_size; | |
| 1005 if (PrintSafepointStatisticsTimeout > 0) { | |
| 1006 stats_array_size = 1; | |
| 1007 PrintSafepointStatistics = true; | |
| 1008 } else { | |
| 1009 stats_array_size = PrintSafepointStatisticsCount; | |
| 1010 } | |
| 1011 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size | |
| 1012 * sizeof(SafepointStats)); | |
| 1013 guarantee(_safepoint_stats != NULL, | |
| 1014 "not enough memory for safepoint instrumentation data"); | |
| 1015 | |
| 1016 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) { | |
| 1017 need_to_track_page_armed_status = true; | |
| 1018 } | |
| 1019 | |
| 1020 tty->print(" vmop_name " | |
| 1021 "[threads: total initially_running wait_to_block] "); | |
| 1022 tty->print("[time: spin block sync] " | |
| 1023 "[vmop_time time_elapsed] "); | |
| 1024 | |
| 1025 // no page armed status printed out if it is always armed. | |
| 1026 if (need_to_track_page_armed_status) { | |
| 1027 tty->print("page_armed "); | |
| 1028 } | |
| 1029 | |
| 1030 tty->print_cr("page_trap_count"); | |
| 1031 | |
| 1032 init_done = true; | |
| 1033 } | |
| 1034 | |
| 1035 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { | |
| 1003 | 1036 assert(init_done, "safepoint statistics array hasn't been initialized"); |
| 0 | 1037 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; |
| 1038 | |
| 1039 VM_Operation *op = VMThread::vm_operation(); | |
| 1040 spstat->_vmop_type = (op != NULL ? op->type() : -1); | |
| 1041 if (op != NULL) { | |
| 1042 _safepoint_reasons[spstat->_vmop_type]++; | |
| 1043 } | |
| 1044 | |
| 1045 spstat->_nof_total_threads = nof_threads; | |
| 1046 spstat->_nof_initial_running_threads = nof_running; | |
| 1047 spstat->_nof_threads_hit_page_trap = 0; | |
| 1048 | |
| 1049 // Records the start time of spinning. The real time spent on spinning | |
| 1050 // will be adjusted when spin is done. Same trick is applied for time | |
| 1051 // spent on waiting for threads to block. | |
| 1052 if (nof_running != 0) { | |
| 1053 spstat->_time_to_spin = os::javaTimeNanos(); | |
| 1054 } else { | |
| 1055 spstat->_time_to_spin = 0; | |
| 1056 } | |
| 1057 | |
| 1058 if (last_safepoint_start_time == 0) { | |
| 1059 spstat->_time_elapsed_since_last_safepoint = 0; | |
| 1060 } else { | |
| 1061 spstat->_time_elapsed_since_last_safepoint = _last_safepoint - | |
| 1062 last_safepoint_start_time; | |
| 1063 } | |
| 1064 last_safepoint_start_time = _last_safepoint; | |
| 1065 } | |
| 1066 | |
| 1067 void SafepointSynchronize::update_statistics_on_spin_end() { | |
| 1068 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; | |
| 1069 | |
| 1070 jlong cur_time = os::javaTimeNanos(); | |
| 1071 | |
| 1072 spstat->_nof_threads_wait_to_block = _waiting_to_block; | |
| 1073 if (spstat->_nof_initial_running_threads != 0) { | |
| 1074 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; | |
| 1075 } | |
| 1076 | |
| 1077 if (need_to_track_page_armed_status) { | |
| 1078 spstat->_page_armed = (PageArmed == 1); | |
| 1079 } | |
| 1080 | |
| 1081 // Records the start time of waiting for to block. Updated when block is done. | |
| 1082 if (_waiting_to_block != 0) { | |
| 1083 spstat->_time_to_wait_to_block = cur_time; | |
| 1084 } else { | |
| 1085 spstat->_time_to_wait_to_block = 0; | |
| 1086 } | |
| 1087 } | |
| 1088 | |
| 1089 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { | |
| 1090 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; | |
| 1091 | |
| 1092 if (spstat->_nof_threads_wait_to_block != 0) { | |
| 1093 spstat->_time_to_wait_to_block = end_time - | |
| 1094 spstat->_time_to_wait_to_block; | |
| 1095 } | |
| 1096 | |
| 1097 // Records the end time of sync which will be used to calculate the total | |
| 1098 // vm operation time. Again, the real time spending in syncing will be deducted | |
| 1099 // from the start of the sync time later when end_statistics is called. | |
| 1100 spstat->_time_to_sync = end_time - _last_safepoint; | |
| 1101 if (spstat->_time_to_sync > _max_sync_time) { | |
| 1102 _max_sync_time = spstat->_time_to_sync; | |
| 1103 } | |
| 1104 sync_end_time = end_time; | |
| 1105 } | |
| 1106 | |
| 1107 void SafepointSynchronize::end_statistics(jlong vmop_end_time) { | |
| 1108 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; | |
| 1109 | |
| 1110 // Update the vm operation time. | |
| 1111 spstat->_time_to_exec_vmop = vmop_end_time - sync_end_time; | |
| 1112 // Only the sync time longer than the specified | |
| 1113 // PrintSafepointStatisticsTimeout will be printed out right away. | |
| 1114 // By default, it is -1 meaning all samples will be put into the list. | |
| 1115 if ( PrintSafepointStatisticsTimeout > 0) { | |
| 1116 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { | |
| 1117 print_statistics(); | |
| 1118 } | |
| 1119 } else { | |
| 1120 // The safepoint statistics will be printed out when the _safepoin_stats | |
| 1121 // array fills up. | |
| 1122 if (_cur_stat_index != PrintSafepointStatisticsCount - 1) { | |
| 1123 _cur_stat_index ++; | |
| 1124 } else { | |
| 1125 print_statistics(); | |
| 1126 _cur_stat_index = 0; | |
| 1127 tty->print_cr(""); | |
| 1128 } | |
| 1129 } | |
| 1130 } | |
| 1131 | |
| 1132 void SafepointSynchronize::print_statistics() { | |
| 1133 int index; | |
| 1134 SafepointStats* sstats = _safepoint_stats; | |
| 1135 | |
| 1136 for (index = 0; index <= _cur_stat_index; index++) { | |
| 1137 sstats = &_safepoint_stats[index]; | |
| 1138 tty->print("%-28s [" | |
| 1139 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15) | |
| 1140 "] ", | |
| 1141 sstats->_vmop_type == -1 ? "no vm operation" : | |
| 1142 VM_Operation::name(sstats->_vmop_type), | |
| 1143 sstats->_nof_total_threads, | |
| 1144 sstats->_nof_initial_running_threads, | |
| 1145 sstats->_nof_threads_wait_to_block); | |
| 1146 // "/ MICROUNITS " is to convert the unit from nanos to millis. | |
| 1147 tty->print(" [" | |
| 1148 INT64_FORMAT_W(6)INT64_FORMAT_W(6)INT64_FORMAT_W(6) | |
| 1149 "] " | |
| 1150 "["INT64_FORMAT_W(6)INT64_FORMAT_W(9) "] ", | |
| 1151 sstats->_time_to_spin / MICROUNITS, | |
| 1152 sstats->_time_to_wait_to_block / MICROUNITS, | |
| 1153 sstats->_time_to_sync / MICROUNITS, | |
| 1154 sstats->_time_to_exec_vmop / MICROUNITS, | |
| 1155 sstats->_time_elapsed_since_last_safepoint / MICROUNITS); | |
| 1156 | |
| 1157 if (need_to_track_page_armed_status) { | |
| 1158 tty->print(INT32_FORMAT" ", sstats->_page_armed); | |
| 1159 } | |
| 1160 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap); | |
| 1161 } | |
| 1162 } | |
| 1163 | |
| 1164 // This method will be called when VM exits. It will first call | |
| 1165 // print_statistics to print out the rest of the sampling. Then | |
| 1166 // it tries to summarize the sampling. | |
| 1167 void SafepointSynchronize::print_stat_on_exit() { | |
| 1168 if (_safepoint_stats == NULL) return; | |
| 1169 | |
| 1170 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; | |
| 1171 | |
| 1172 // During VM exit, end_statistics may not get called and in that | |
| 1173 // case, if the sync time is less than PrintSafepointStatisticsTimeout, | |
| 1174 // don't print it out. | |
| 1175 // Approximate the vm op time. | |
| 1176 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = | |
| 1177 os::javaTimeNanos() - sync_end_time; | |
| 1178 | |
| 1179 if ( PrintSafepointStatisticsTimeout < 0 || | |
| 1180 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { | |
| 1181 print_statistics(); | |
| 1182 } | |
| 1183 tty->print_cr(""); | |
| 1184 | |
| 1185 // Print out polling page sampling status. | |
| 1186 if (!need_to_track_page_armed_status) { | |
| 1187 if (UseCompilerSafepoints) { | |
| 1188 tty->print_cr("Polling page always armed"); | |
| 1189 } | |
| 1190 } else { | |
| 1191 tty->print_cr("Defer polling page loop count = %d\n", | |
| 1192 DeferPollingPageLoopCount); | |
| 1193 } | |
| 1194 | |
| 1195 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { | |
| 1196 if (_safepoint_reasons[index] != 0) { | |
| 1197 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index), | |
| 1198 _safepoint_reasons[index]); | |
| 1199 } | |
| 1200 } | |
| 1201 | |
| 1202 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint", | |
| 1203 _coalesced_vmop_count); | |
| 1204 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms", | |
| 1205 _max_sync_time / MICROUNITS); | |
| 1206 } | |
| 1207 | |
| 1208 // ------------------------------------------------------------------------------------------------ | |
| 1209 // Non-product code | |
| 1210 | |
| 1211 #ifndef PRODUCT | |
| 1212 | |
| 1213 void SafepointSynchronize::print_state() { | |
| 1214 if (_state == _not_synchronized) { | |
| 1215 tty->print_cr("not synchronized"); | |
| 1216 } else if (_state == _synchronizing || _state == _synchronized) { | |
| 1217 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : | |
| 1218 "synchronized"); | |
| 1219 | |
| 1220 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { | |
| 1221 cur->safepoint_state()->print(); | |
| 1222 } | |
| 1223 } | |
| 1224 } | |
| 1225 | |
| 1226 void SafepointSynchronize::safepoint_msg(const char* format, ...) { | |
| 1227 if (ShowSafepointMsgs) { | |
| 1228 va_list ap; | |
| 1229 va_start(ap, format); | |
| 1230 tty->vprint_cr(format, ap); | |
| 1231 va_end(ap); | |
| 1232 } | |
| 1233 } | |
| 1234 | |
| 1235 #endif // !PRODUCT |