annotate hotspot/src/share/vm/runtime/safepoint.cpp @ 4006:7be2d5b3b15c

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 67b89f5a5cac
children f86707fd195a
rev   line source
duke@1 1 /*
xdono@2105 2 * Copyright 1997-2009 Sun Microsystems, Inc. All Rights Reserved.
duke@1 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@1 4 *
duke@1 5 * This code is free software; you can redistribute it and/or modify it
duke@1 6 * under the terms of the GNU General Public License version 2 only, as
duke@1 7 * published by the Free Software Foundation.
duke@1 8 *
duke@1 9 * This code is distributed in the hope that it will be useful, but WITHOUT
duke@1 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@1 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
duke@1 12 * version 2 for more details (a copy is included in the LICENSE file that
duke@1 13 * accompanied this code).
duke@1 14 *
duke@1 15 * You should have received a copy of the GNU General Public License version
duke@1 16 * 2 along with this work; if not, write to the Free Software Foundation,
duke@1 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@1 18 *
duke@1 19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@1 20 * CA 95054 USA or visit www.sun.com if you need additional information or
duke@1 21 * have any questions.
duke@1 22 *
duke@1 23 */
duke@1 24
duke@1 25 # include "incls/_precompiled.incl"
duke@1 26 # include "incls/_safepoint.cpp.incl"
duke@1 27
duke@1 28 // --------------------------------------------------------------------------------------------------
duke@1 29 // Implementation of Safepoint begin/end
duke@1 30
duke@1 31 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
duke@1 32 volatile int SafepointSynchronize::_waiting_to_block = 0;
duke@1 33 jlong SafepointSynchronize::_last_safepoint = 0;
duke@1 34 volatile int SafepointSynchronize::_safepoint_counter = 0;
duke@1 35 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
duke@1 36 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
duke@1 37 static bool timeout_error_printed = false;
duke@1 38
duke@1 39 // Roll all threads forward to a safepoint and suspend them all
duke@1 40 void SafepointSynchronize::begin() {
duke@1 41
duke@1 42 Thread* myThread = Thread::current();
duke@1 43 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
duke@1 44
duke@1 45 _last_safepoint = os::javaTimeNanos();
duke@1 46
duke@1 47 #ifndef SERIALGC
duke@1 48 if (UseConcMarkSweepGC) {
duke@1 49 // In the future we should investigate whether CMS can use the
duke@1 50 // more-general mechanism below. DLD (01/05).
duke@1 51 ConcurrentMarkSweepThread::synchronize(false);
ysr@3262 52 } else if (UseG1GC) {
duke@1 53 ConcurrentGCThread::safepoint_synchronize();
duke@1 54 }
duke@1 55 #endif // SERIALGC
duke@1 56
duke@1 57 // By getting the Threads_lock, we assure that no threads are about to start or
duke@1 58 // exit. It is released again in SafepointSynchronize::end().
duke@1 59 Threads_lock->lock();
duke@1 60
duke@1 61 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
duke@1 62
duke@1 63 int nof_threads = Threads::number_of_threads();
duke@1 64
duke@1 65 if (TraceSafepoint) {
duke@1 66 tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads);
duke@1 67 }
duke@1 68
duke@1 69 RuntimeService::record_safepoint_begin();
duke@1 70
duke@1 71 {
duke@1 72 MutexLocker mu(Safepoint_lock);
duke@1 73
duke@1 74 // Set number of threads to wait for, before we initiate the callbacks
duke@1 75 _waiting_to_block = nof_threads;
duke@1 76 TryingToBlock = 0 ;
duke@1 77 int still_running = nof_threads;
duke@1 78
duke@1 79 // Save the starting time, so that it can be compared to see if this has taken
duke@1 80 // too long to complete.
duke@1 81 jlong safepoint_limit_time;
duke@1 82 timeout_error_printed = false;
duke@1 83
xlu@4006 84 // PrintSafepointStatisticsTimeout can be specified separately. When
xlu@4006 85 // specified, PrintSafepointStatistics will be set to true in
xlu@4006 86 // deferred_initialize_stat method. The initialization has to be done
xlu@4006 87 // early enough to avoid any races. See bug 6880029 for details.
xlu@4006 88 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@4006 89 deferred_initialize_stat();
xlu@4006 90 }
xlu@4006 91
duke@1 92 // Begin the process of bringing the system to a safepoint.
duke@1 93 // Java threads can be in several different states and are
duke@1 94 // stopped by different mechanisms:
duke@1 95 //
duke@1 96 // 1. Running interpreted
duke@1 97 // The interpeter dispatch table is changed to force it to
duke@1 98 // check for a safepoint condition between bytecodes.
duke@1 99 // 2. Running in native code
duke@1 100 // When returning from the native code, a Java thread must check
duke@1 101 // the safepoint _state to see if we must block. If the
duke@1 102 // VM thread sees a Java thread in native, it does
duke@1 103 // not wait for this thread to block. The order of the memory
duke@1 104 // writes and reads of both the safepoint state and the Java
duke@1 105 // threads state is critical. In order to guarantee that the
duke@1 106 // memory writes are serialized with respect to each other,
duke@1 107 // the VM thread issues a memory barrier instruction
duke@1 108 // (on MP systems). In order to avoid the overhead of issuing
duke@1 109 // a memory barrier for each Java thread making native calls, each Java
duke@1 110 // thread performs a write to a single memory page after changing
duke@1 111 // the thread state. The VM thread performs a sequence of
duke@1 112 // mprotect OS calls which forces all previous writes from all
duke@1 113 // Java threads to be serialized. This is done in the
duke@1 114 // os::serialize_thread_states() call. This has proven to be
duke@1 115 // much more efficient than executing a membar instruction
duke@1 116 // on every call to native code.
duke@1 117 // 3. Running compiled Code
duke@1 118 // Compiled code reads a global (Safepoint Polling) page that
duke@1 119 // is set to fault if we are trying to get to a safepoint.
duke@1 120 // 4. Blocked
duke@1 121 // A thread which is blocked will not be allowed to return from the
duke@1 122 // block condition until the safepoint operation is complete.
duke@1 123 // 5. In VM or Transitioning between states
duke@1 124 // If a Java thread is currently running in the VM or transitioning
duke@1 125 // between states, the safepointing code will wait for the thread to
duke@1 126 // block itself when it attempts transitions to a new state.
duke@1 127 //
duke@1 128 _state = _synchronizing;
duke@1 129 OrderAccess::fence();
duke@1 130
duke@1 131 // Flush all thread states to memory
duke@1 132 if (!UseMembar) {
duke@1 133 os::serialize_thread_states();
duke@1 134 }
duke@1 135
duke@1 136 // Make interpreter safepoint aware
duke@1 137 Interpreter::notice_safepoints();
duke@1 138
duke@1 139 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
duke@1 140 // Make polling safepoint aware
duke@1 141 guarantee (PageArmed == 0, "invariant") ;
duke@1 142 PageArmed = 1 ;
duke@1 143 os::make_polling_page_unreadable();
duke@1 144 }
duke@1 145
duke@1 146 // Consider using active_processor_count() ... but that call is expensive.
duke@1 147 int ncpus = os::processor_count() ;
duke@1 148
duke@1 149 #ifdef ASSERT
duke@1 150 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
duke@1 151 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
duke@1 152 }
duke@1 153 #endif // ASSERT
duke@1 154
duke@1 155 if (SafepointTimeout)
duke@1 156 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
duke@1 157
duke@1 158 // Iterate through all threads until it have been determined how to stop them all at a safepoint
duke@1 159 unsigned int iterations = 0;
duke@1 160 int steps = 0 ;
duke@1 161 while(still_running > 0) {
duke@1 162 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
duke@1 163 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
duke@1 164 ThreadSafepointState *cur_state = cur->safepoint_state();
duke@1 165 if (cur_state->is_running()) {
duke@1 166 cur_state->examine_state_of_thread();
duke@1 167 if (!cur_state->is_running()) {
duke@1 168 still_running--;
duke@1 169 // consider adjusting steps downward:
duke@1 170 // steps = 0
duke@1 171 // steps -= NNN
duke@1 172 // steps >>= 1
duke@1 173 // steps = MIN(steps, 2000-100)
duke@1 174 // if (iterations != 0) steps -= NNN
duke@1 175 }
duke@1 176 if (TraceSafepoint && Verbose) cur_state->print();
duke@1 177 }
duke@1 178 }
duke@1 179
xlu@4006 180 if (PrintSafepointStatistics && iterations == 0) {
duke@1 181 begin_statistics(nof_threads, still_running);
duke@1 182 }
duke@1 183
duke@1 184 if (still_running > 0) {
duke@1 185 // Check for if it takes to long
duke@1 186 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
duke@1 187 print_safepoint_timeout(_spinning_timeout);
duke@1 188 }
duke@1 189
duke@1 190 // Spin to avoid context switching.
duke@1 191 // There's a tension between allowing the mutators to run (and rendezvous)
duke@1 192 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
duke@1 193 // a mutator might otherwise use profitably to reach a safepoint. Excessive
duke@1 194 // spinning by the VM thread on a saturated system can increase rendezvous latency.
duke@1 195 // Blocking or yielding incur their own penalties in the form of context switching
duke@1 196 // and the resultant loss of $ residency.
duke@1 197 //
duke@1 198 // Further complicating matters is that yield() does not work as naively expected
duke@1 199 // on many platforms -- yield() does not guarantee that any other ready threads
duke@1 200 // will run. As such we revert yield_all() after some number of iterations.
duke@1 201 // Yield_all() is implemented as a short unconditional sleep on some platforms.
duke@1 202 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
duke@1 203 // can actually increase the time it takes the VM thread to detect that a system-wide
duke@1 204 // stop-the-world safepoint has been reached. In a pathological scenario such as that
duke@1 205 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
duke@1 206 // In that case the mutators will be stalled waiting for the safepoint to complete and the
duke@1 207 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
duke@1 208 // will eventually wake up and detect that all mutators are safe, at which point
duke@1 209 // we'll again make progress.
duke@1 210 //
duke@1 211 // Beware too that that the VMThread typically runs at elevated priority.
duke@1 212 // Its default priority is higher than the default mutator priority.
duke@1 213 // Obviously, this complicates spinning.
duke@1 214 //
duke@1 215 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
duke@1 216 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
duke@1 217 //
duke@1 218 // See the comments in synchronizer.cpp for additional remarks on spinning.
duke@1 219 //
duke@1 220 // In the future we might:
duke@1 221 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
duke@1 222 // This is tricky as the path used by a thread exiting the JVM (say on
duke@1 223 // on JNI call-out) simply stores into its state field. The burden
duke@1 224 // is placed on the VM thread, which must poll (spin).
duke@1 225 // 2. Find something useful to do while spinning. If the safepoint is GC-related
duke@1 226 // we might aggressively scan the stacks of threads that are already safe.
duke@1 227 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
duke@1 228 // If all the mutators are ONPROC there's no reason to sleep or yield.
duke@1 229 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
duke@1 230 // 5. Check system saturation. If the system is not fully saturated then
duke@1 231 // simply spin and avoid sleep/yield.
duke@1 232 // 6. As still-running mutators rendezvous they could unpark the sleeping
duke@1 233 // VMthread. This works well for still-running mutators that become
duke@1 234 // safe. The VMthread must still poll for mutators that call-out.
duke@1 235 // 7. Drive the policy on time-since-begin instead of iterations.
duke@1 236 // 8. Consider making the spin duration a function of the # of CPUs:
duke@1 237 // Spin = (((ncpus-1) * M) + K) + F(still_running)
duke@1 238 // Alternately, instead of counting iterations of the outer loop
duke@1 239 // we could count the # of threads visited in the inner loop, above.
duke@1 240 // 9. On windows consider using the return value from SwitchThreadTo()
duke@1 241 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
duke@1 242
duke@1 243 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
duke@1 244 guarantee (PageArmed == 0, "invariant") ;
duke@1 245 PageArmed = 1 ;
duke@1 246 os::make_polling_page_unreadable();
duke@1 247 }
duke@1 248
duke@1 249 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
duke@1 250 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
duke@1 251 ++steps ;
duke@1 252 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
duke@1 253 SpinPause() ; // MP-Polite spin
duke@1 254 } else
duke@1 255 if (steps < DeferThrSuspendLoopCount) {
duke@1 256 os::NakedYield() ;
duke@1 257 } else {
duke@1 258 os::yield_all(steps) ;
duke@1 259 // Alternately, the VM thread could transiently depress its scheduling priority or
duke@1 260 // transiently increase the priority of the tardy mutator(s).
duke@1 261 }
duke@1 262
duke@1 263 iterations ++ ;
duke@1 264 }
duke@1 265 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
duke@1 266 }
duke@1 267 assert(still_running == 0, "sanity check");
duke@1 268
duke@1 269 if (PrintSafepointStatistics) {
duke@1 270 update_statistics_on_spin_end();
duke@1 271 }
duke@1 272
duke@1 273 // wait until all threads are stopped
duke@1 274 while (_waiting_to_block > 0) {
duke@1 275 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
duke@1 276 if (!SafepointTimeout || timeout_error_printed) {
duke@1 277 Safepoint_lock->wait(true); // true, means with no safepoint checks
duke@1 278 } else {
duke@1 279 // Compute remaining time
duke@1 280 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
duke@1 281
duke@1 282 // If there is no remaining time, then there is an error
duke@1 283 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
duke@1 284 print_safepoint_timeout(_blocking_timeout);
duke@1 285 }
duke@1 286 }
duke@1 287 }
duke@1 288 assert(_waiting_to_block == 0, "sanity check");
duke@1 289
duke@1 290 #ifndef PRODUCT
duke@1 291 if (SafepointTimeout) {
duke@1 292 jlong current_time = os::javaTimeNanos();
duke@1 293 if (safepoint_limit_time < current_time) {
duke@1 294 tty->print_cr("# SafepointSynchronize: Finished after "
duke@1 295 INT64_FORMAT_W(6) " ms",
duke@1 296 ((current_time - safepoint_limit_time) / MICROUNITS +
duke@1 297 SafepointTimeoutDelay));
duke@1 298 }
duke@1 299 }
duke@1 300 #endif
duke@1 301
duke@1 302 assert((_safepoint_counter & 0x1) == 0, "must be even");
duke@1 303 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 304 _safepoint_counter ++;
duke@1 305
duke@1 306 // Record state
duke@1 307 _state = _synchronized;
duke@1 308
duke@1 309 OrderAccess::fence();
duke@1 310
duke@1 311 if (TraceSafepoint) {
duke@1 312 VM_Operation *op = VMThread::vm_operation();
duke@1 313 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
duke@1 314 }
duke@1 315
duke@1 316 RuntimeService::record_safepoint_synchronized();
duke@1 317 if (PrintSafepointStatistics) {
duke@1 318 update_statistics_on_sync_end(os::javaTimeNanos());
duke@1 319 }
duke@1 320
duke@1 321 // Call stuff that needs to be run when a safepoint is just about to be completed
duke@1 322 do_cleanup_tasks();
duke@1 323 }
duke@1 324 }
duke@1 325
duke@1 326 // Wake up all threads, so they are ready to resume execution after the safepoint
duke@1 327 // operation has been carried out
duke@1 328 void SafepointSynchronize::end() {
duke@1 329
duke@1 330 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 331 assert((_safepoint_counter & 0x1) == 1, "must be odd");
duke@1 332 _safepoint_counter ++;
duke@1 333 // memory fence isn't required here since an odd _safepoint_counter
duke@1 334 // value can do no harm and a fence is issued below anyway.
duke@1 335
duke@1 336 DEBUG_ONLY(Thread* myThread = Thread::current();)
duke@1 337 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
duke@1 338
duke@1 339 if (PrintSafepointStatistics) {
duke@1 340 end_statistics(os::javaTimeNanos());
duke@1 341 }
duke@1 342
duke@1 343 #ifdef ASSERT
duke@1 344 // A pending_exception cannot be installed during a safepoint. The threads
duke@1 345 // may install an async exception after they come back from a safepoint into
duke@1 346 // pending_exception after they unblock. But that should happen later.
duke@1 347 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 348 assert (!(cur->has_pending_exception() &&
duke@1 349 cur->safepoint_state()->is_at_poll_safepoint()),
duke@1 350 "safepoint installed a pending exception");
duke@1 351 }
duke@1 352 #endif // ASSERT
duke@1 353
duke@1 354 if (PageArmed) {
duke@1 355 // Make polling safepoint aware
duke@1 356 os::make_polling_page_readable();
duke@1 357 PageArmed = 0 ;
duke@1 358 }
duke@1 359
duke@1 360 // Remove safepoint check from interpreter
duke@1 361 Interpreter::ignore_safepoints();
duke@1 362
duke@1 363 {
duke@1 364 MutexLocker mu(Safepoint_lock);
duke@1 365
duke@1 366 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
duke@1 367
duke@1 368 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
duke@1 369 // when they get restarted.
duke@1 370 _state = _not_synchronized;
duke@1 371 OrderAccess::fence();
duke@1 372
duke@1 373 if (TraceSafepoint) {
duke@1 374 tty->print_cr("Leaving safepoint region");
duke@1 375 }
duke@1 376
duke@1 377 // Start suspended threads
duke@1 378 for(JavaThread *current = Threads::first(); current; current = current->next()) {
twisti@2131 379 // A problem occurring on Solaris is when attempting to restart threads
duke@1 380 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
duke@1 381 // to the next one (since it has been running the longest). We then have
duke@1 382 // to wait for a cpu to become available before we can continue restarting
duke@1 383 // threads.
duke@1 384 // FIXME: This causes the performance of the VM to degrade when active and with
duke@1 385 // large numbers of threads. Apparently this is due to the synchronous nature
duke@1 386 // of suspending threads.
duke@1 387 //
duke@1 388 // TODO-FIXME: the comments above are vestigial and no longer apply.
duke@1 389 // Furthermore, using solaris' schedctl in this particular context confers no benefit
duke@1 390 if (VMThreadHintNoPreempt) {
duke@1 391 os::hint_no_preempt();
duke@1 392 }
duke@1 393 ThreadSafepointState* cur_state = current->safepoint_state();
duke@1 394 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
duke@1 395 cur_state->restart();
duke@1 396 assert(cur_state->is_running(), "safepoint state has not been reset");
duke@1 397 }
duke@1 398
duke@1 399 RuntimeService::record_safepoint_end();
duke@1 400
duke@1 401 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
duke@1 402 // blocked in signal_thread_blocked
duke@1 403 Threads_lock->unlock();
duke@1 404
duke@1 405 }
duke@1 406 #ifndef SERIALGC
duke@1 407 // If there are any concurrent GC threads resume them.
duke@1 408 if (UseConcMarkSweepGC) {
duke@1 409 ConcurrentMarkSweepThread::desynchronize(false);
ysr@3262 410 } else if (UseG1GC) {
duke@1 411 ConcurrentGCThread::safepoint_desynchronize();
duke@1 412 }
duke@1 413 #endif // SERIALGC
duke@1 414 }
duke@1 415
duke@1 416 bool SafepointSynchronize::is_cleanup_needed() {
duke@1 417 // Need a safepoint if some inline cache buffers is non-empty
duke@1 418 if (!InlineCacheBuffer::is_empty()) return true;
duke@1 419 return false;
duke@1 420 }
duke@1 421
duke@1 422 jlong CounterDecay::_last_timestamp = 0;
duke@1 423
duke@1 424 static void do_method(methodOop m) {
duke@1 425 m->invocation_counter()->decay();
duke@1 426 }
duke@1 427
duke@1 428 void CounterDecay::decay() {
duke@1 429 _last_timestamp = os::javaTimeMillis();
duke@1 430
duke@1 431 // This operation is going to be performed only at the end of a safepoint
duke@1 432 // and hence GC's will not be going on, all Java mutators are suspended
duke@1 433 // at this point and hence SystemDictionary_lock is also not needed.
duke@1 434 assert(SafepointSynchronize::is_at_safepoint(), "can only be executed at a safepoint");
duke@1 435 int nclasses = SystemDictionary::number_of_classes();
duke@1 436 double classes_per_tick = nclasses * (CounterDecayMinIntervalLength * 1e-3 /
duke@1 437 CounterHalfLifeTime);
duke@1 438 for (int i = 0; i < classes_per_tick; i++) {
duke@1 439 klassOop k = SystemDictionary::try_get_next_class();
duke@1 440 if (k != NULL && k->klass_part()->oop_is_instance()) {
duke@1 441 instanceKlass::cast(k)->methods_do(do_method);
duke@1 442 }
duke@1 443 }
duke@1 444 }
duke@1 445
duke@1 446 // Various cleaning tasks that should be done periodically at safepoints
duke@1 447 void SafepointSynchronize::do_cleanup_tasks() {
duke@1 448 jlong cleanup_time;
duke@1 449
duke@1 450 // Update fat-monitor pool, since this is a safepoint.
duke@1 451 if (TraceSafepoint) {
duke@1 452 cleanup_time = os::javaTimeNanos();
duke@1 453 }
duke@1 454
duke@1 455 ObjectSynchronizer::deflate_idle_monitors();
duke@1 456 InlineCacheBuffer::update_inline_caches();
duke@1 457 if(UseCounterDecay && CounterDecay::is_decay_needed()) {
duke@1 458 CounterDecay::decay();
duke@1 459 }
duke@1 460 NMethodSweeper::sweep();
duke@1 461
duke@1 462 if (TraceSafepoint) {
duke@1 463 tty->print_cr("do_cleanup_tasks takes "INT64_FORMAT_W(6) "ms",
duke@1 464 (os::javaTimeNanos() - cleanup_time) / MICROUNITS);
duke@1 465 }
duke@1 466 }
duke@1 467
duke@1 468
duke@1 469 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
duke@1 470 switch(state) {
duke@1 471 case _thread_in_native:
duke@1 472 // native threads are safe if they have no java stack or have walkable stack
duke@1 473 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
duke@1 474
duke@1 475 // blocked threads should have already have walkable stack
duke@1 476 case _thread_blocked:
duke@1 477 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
duke@1 478 return true;
duke@1 479
duke@1 480 default:
duke@1 481 return false;
duke@1 482 }
duke@1 483 }
duke@1 484
duke@1 485
duke@1 486 // -------------------------------------------------------------------------------------------------------
duke@1 487 // Implementation of Safepoint callback point
duke@1 488
duke@1 489 void SafepointSynchronize::block(JavaThread *thread) {
duke@1 490 assert(thread != NULL, "thread must be set");
duke@1 491 assert(thread->is_Java_thread(), "not a Java thread");
duke@1 492
duke@1 493 // Threads shouldn't block if they are in the middle of printing, but...
duke@1 494 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
duke@1 495
duke@1 496 // Only bail from the block() call if the thread is gone from the
duke@1 497 // thread list; starting to exit should still block.
duke@1 498 if (thread->is_terminated()) {
duke@1 499 // block current thread if we come here from native code when VM is gone
duke@1 500 thread->block_if_vm_exited();
duke@1 501
duke@1 502 // otherwise do nothing
duke@1 503 return;
duke@1 504 }
duke@1 505
duke@1 506 JavaThreadState state = thread->thread_state();
duke@1 507 thread->frame_anchor()->make_walkable(thread);
duke@1 508
duke@1 509 // Check that we have a valid thread_state at this point
duke@1 510 switch(state) {
duke@1 511 case _thread_in_vm_trans:
duke@1 512 case _thread_in_Java: // From compiled code
duke@1 513
duke@1 514 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
duke@1 515 // we pretend we are still in the VM.
duke@1 516 thread->set_thread_state(_thread_in_vm);
duke@1 517
duke@1 518 if (is_synchronizing()) {
duke@1 519 Atomic::inc (&TryingToBlock) ;
duke@1 520 }
duke@1 521
duke@1 522 // We will always be holding the Safepoint_lock when we are examine the state
duke@1 523 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
duke@1 524 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
duke@1 525 Safepoint_lock->lock_without_safepoint_check();
duke@1 526 if (is_synchronizing()) {
duke@1 527 // Decrement the number of threads to wait for and signal vm thread
duke@1 528 assert(_waiting_to_block > 0, "sanity check");
duke@1 529 _waiting_to_block--;
duke@1 530 thread->safepoint_state()->set_has_called_back(true);
duke@1 531
duke@1 532 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
duke@1 533 if (_waiting_to_block == 0) {
duke@1 534 Safepoint_lock->notify_all();
duke@1 535 }
duke@1 536 }
duke@1 537
duke@1 538 // We transition the thread to state _thread_blocked here, but
duke@1 539 // we can't do our usual check for external suspension and then
duke@1 540 // self-suspend after the lock_without_safepoint_check() call
duke@1 541 // below because we are often called during transitions while
duke@1 542 // we hold different locks. That would leave us suspended while
duke@1 543 // holding a resource which results in deadlocks.
duke@1 544 thread->set_thread_state(_thread_blocked);
duke@1 545 Safepoint_lock->unlock();
duke@1 546
duke@1 547 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
duke@1 548 // the entire safepoint, the threads will all line up here during the safepoint.
duke@1 549 Threads_lock->lock_without_safepoint_check();
duke@1 550 // restore original state. This is important if the thread comes from compiled code, so it
duke@1 551 // will continue to execute with the _thread_in_Java state.
duke@1 552 thread->set_thread_state(state);
duke@1 553 Threads_lock->unlock();
duke@1 554 break;
duke@1 555
duke@1 556 case _thread_in_native_trans:
duke@1 557 case _thread_blocked_trans:
duke@1 558 case _thread_new_trans:
duke@1 559 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
duke@1 560 thread->print_thread_state();
duke@1 561 fatal("Deadlock in safepoint code. "
duke@1 562 "Should have called back to the VM before blocking.");
duke@1 563 }
duke@1 564
duke@1 565 // We transition the thread to state _thread_blocked here, but
duke@1 566 // we can't do our usual check for external suspension and then
duke@1 567 // self-suspend after the lock_without_safepoint_check() call
duke@1 568 // below because we are often called during transitions while
duke@1 569 // we hold different locks. That would leave us suspended while
duke@1 570 // holding a resource which results in deadlocks.
duke@1 571 thread->set_thread_state(_thread_blocked);
duke@1 572
duke@1 573 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
duke@1 574 // the safepoint code might still be waiting for it to block. We need to change the state here,
duke@1 575 // so it can see that it is at a safepoint.
duke@1 576
duke@1 577 // Block until the safepoint operation is completed.
duke@1 578 Threads_lock->lock_without_safepoint_check();
duke@1 579
duke@1 580 // Restore state
duke@1 581 thread->set_thread_state(state);
duke@1 582
duke@1 583 Threads_lock->unlock();
duke@1 584 break;
duke@1 585
duke@1 586 default:
duke@1 587 fatal1("Illegal threadstate encountered: %d", state);
duke@1 588 }
duke@1 589
duke@1 590 // Check for pending. async. exceptions or suspends - except if the
duke@1 591 // thread was blocked inside the VM. has_special_runtime_exit_condition()
duke@1 592 // is called last since it grabs a lock and we only want to do that when
duke@1 593 // we must.
duke@1 594 //
duke@1 595 // Note: we never deliver an async exception at a polling point as the
duke@1 596 // compiler may not have an exception handler for it. The polling
duke@1 597 // code will notice the async and deoptimize and the exception will
duke@1 598 // be delivered. (Polling at a return point is ok though). Sure is
duke@1 599 // a lot of bother for a deprecated feature...
duke@1 600 //
duke@1 601 // We don't deliver an async exception if the thread state is
duke@1 602 // _thread_in_native_trans so JNI functions won't be called with
duke@1 603 // a surprising pending exception. If the thread state is going back to java,
duke@1 604 // async exception is checked in check_special_condition_for_native_trans().
duke@1 605
duke@1 606 if (state != _thread_blocked_trans &&
duke@1 607 state != _thread_in_vm_trans &&
duke@1 608 thread->has_special_runtime_exit_condition()) {
duke@1 609 thread->handle_special_runtime_exit_condition(
duke@1 610 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
duke@1 611 }
duke@1 612 }
duke@1 613
duke@1 614 // ------------------------------------------------------------------------------------------------------
duke@1 615 // Exception handlers
duke@1 616
duke@1 617 #ifndef PRODUCT
duke@1 618 #ifdef _LP64
duke@1 619 #define PTR_PAD ""
duke@1 620 #else
duke@1 621 #define PTR_PAD " "
duke@1 622 #endif
duke@1 623
duke@1 624 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
duke@1 625 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false;
duke@1 626 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
duke@1 627 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
duke@1 628 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
duke@1 629 }
duke@1 630
duke@1 631 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
duke@1 632 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false;
duke@1 633 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s",
duke@1 634 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
duke@1 635 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
duke@1 636 }
duke@1 637
duke@1 638 #ifdef SPARC
duke@1 639 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
duke@1 640 #ifdef _LP64
duke@1 641 tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
duke@1 642 const int incr = 1; // Increment to skip a long, in units of intptr_t
duke@1 643 #else
duke@1 644 tty->print_cr("--------+--address-+------before-----------+-------after----------+");
duke@1 645 const int incr = 2; // Increment to skip a long, in units of intptr_t
duke@1 646 #endif
duke@1 647 tty->print_cr("---SP---|");
duke@1 648 for( int i=0; i<16; i++ ) {
duke@1 649 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
duke@1 650 tty->print_cr("--------|");
duke@1 651 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
duke@1 652 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
duke@1 653 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
duke@1 654 tty->print_cr("--------|");
duke@1 655 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;
duke@1 656 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;
duke@1 657 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;
duke@1 658 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;
duke@1 659 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
duke@1 660 old_sp += incr; new_sp += incr; was_oops += incr;
duke@1 661 // Skip the floats
duke@1 662 tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
duke@1 663 tty->print_cr("---FP---|");
duke@1 664 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32;
duke@1 665 for( int i2=0; i2<16; i2++ ) {
duke@1 666 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
duke@1 667 tty->print_cr("");
duke@1 668 }
duke@1 669 #endif // SPARC
duke@1 670 #endif // PRODUCT
duke@1 671
duke@1 672
duke@1 673 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
duke@1 674 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
duke@1 675 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
duke@1 676 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
duke@1 677
duke@1 678 // Uncomment this to get some serious before/after printing of the
duke@1 679 // Sparc safepoint-blob frame structure.
duke@1 680 /*
duke@1 681 intptr_t* sp = thread->last_Java_sp();
duke@1 682 intptr_t stack_copy[150];
duke@1 683 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
duke@1 684 bool was_oops[150];
duke@1 685 for( int i=0; i<150; i++ )
duke@1 686 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
duke@1 687 */
duke@1 688
duke@1 689 if (ShowSafepointMsgs) {
duke@1 690 tty->print("handle_polling_page_exception: ");
duke@1 691 }
duke@1 692
duke@1 693 if (PrintSafepointStatistics) {
duke@1 694 inc_page_trap_count();
duke@1 695 }
duke@1 696
duke@1 697 ThreadSafepointState* state = thread->safepoint_state();
duke@1 698
duke@1 699 state->handle_polling_page_exception();
duke@1 700 // print_me(sp,stack_copy,was_oops);
duke@1 701 }
duke@1 702
duke@1 703
duke@1 704 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
duke@1 705 if (!timeout_error_printed) {
duke@1 706 timeout_error_printed = true;
duke@1 707 // Print out the thread infor which didn't reach the safepoint for debugging
duke@1 708 // purposes (useful when there are lots of threads in the debugger).
duke@1 709 tty->print_cr("");
duke@1 710 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
duke@1 711 if (reason == _spinning_timeout) {
duke@1 712 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
duke@1 713 } else if (reason == _blocking_timeout) {
duke@1 714 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
duke@1 715 }
duke@1 716
duke@1 717 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
duke@1 718 ThreadSafepointState *cur_state;
duke@1 719 ResourceMark rm;
duke@1 720 for(JavaThread *cur_thread = Threads::first(); cur_thread;
duke@1 721 cur_thread = cur_thread->next()) {
duke@1 722 cur_state = cur_thread->safepoint_state();
duke@1 723
duke@1 724 if (cur_thread->thread_state() != _thread_blocked &&
duke@1 725 ((reason == _spinning_timeout && cur_state->is_running()) ||
duke@1 726 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
duke@1 727 tty->print("# ");
duke@1 728 cur_thread->print();
duke@1 729 tty->print_cr("");
duke@1 730 }
duke@1 731 }
duke@1 732 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
duke@1 733 }
duke@1 734
duke@1 735 // To debug the long safepoint, specify both DieOnSafepointTimeout &
duke@1 736 // ShowMessageBoxOnError.
duke@1 737 if (DieOnSafepointTimeout) {
duke@1 738 char msg[1024];
duke@1 739 VM_Operation *op = VMThread::vm_operation();
xlu@1889 740 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
duke@1 741 SafepointTimeoutDelay,
duke@1 742 op != NULL ? op->name() : "no vm operation");
duke@1 743 fatal(msg);
duke@1 744 }
duke@1 745 }
duke@1 746
duke@1 747
duke@1 748 // -------------------------------------------------------------------------------------------------------
duke@1 749 // Implementation of ThreadSafepointState
duke@1 750
duke@1 751 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
duke@1 752 _thread = thread;
duke@1 753 _type = _running;
duke@1 754 _has_called_back = false;
duke@1 755 _at_poll_safepoint = false;
duke@1 756 }
duke@1 757
duke@1 758 void ThreadSafepointState::create(JavaThread *thread) {
duke@1 759 ThreadSafepointState *state = new ThreadSafepointState(thread);
duke@1 760 thread->set_safepoint_state(state);
duke@1 761 }
duke@1 762
duke@1 763 void ThreadSafepointState::destroy(JavaThread *thread) {
duke@1 764 if (thread->safepoint_state()) {
duke@1 765 delete(thread->safepoint_state());
duke@1 766 thread->set_safepoint_state(NULL);
duke@1 767 }
duke@1 768 }
duke@1 769
duke@1 770 void ThreadSafepointState::examine_state_of_thread() {
duke@1 771 assert(is_running(), "better be running or just have hit safepoint poll");
duke@1 772
duke@1 773 JavaThreadState state = _thread->thread_state();
duke@1 774
duke@1 775 // Check for a thread that is suspended. Note that thread resume tries
duke@1 776 // to grab the Threads_lock which we own here, so a thread cannot be
duke@1 777 // resumed during safepoint synchronization.
duke@1 778
dcubed@3826 779 // We check to see if this thread is suspended without locking to
dcubed@3826 780 // avoid deadlocking with a third thread that is waiting for this
dcubed@3826 781 // thread to be suspended. The third thread can notice the safepoint
dcubed@3826 782 // that we're trying to start at the beginning of its SR_lock->wait()
dcubed@3826 783 // call. If that happens, then the third thread will block on the
dcubed@3826 784 // safepoint while still holding the underlying SR_lock. We won't be
dcubed@3826 785 // able to get the SR_lock and we'll deadlock.
dcubed@3826 786 //
dcubed@3826 787 // We don't need to grab the SR_lock here for two reasons:
dcubed@3826 788 // 1) The suspend flags are both volatile and are set with an
dcubed@3826 789 // Atomic::cmpxchg() call so we should see the suspended
dcubed@3826 790 // state right away.
dcubed@3826 791 // 2) We're being called from the safepoint polling loop; if
dcubed@3826 792 // we don't see the suspended state on this iteration, then
dcubed@3826 793 // we'll come around again.
dcubed@3826 794 //
dcubed@3826 795 bool is_suspended = _thread->is_ext_suspended();
duke@1 796 if (is_suspended) {
duke@1 797 roll_forward(_at_safepoint);
duke@1 798 return;
duke@1 799 }
duke@1 800
duke@1 801 // Some JavaThread states have an initial safepoint state of
duke@1 802 // running, but are actually at a safepoint. We will happily
duke@1 803 // agree and update the safepoint state here.
duke@1 804 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
duke@1 805 roll_forward(_at_safepoint);
duke@1 806 return;
duke@1 807 }
duke@1 808
duke@1 809 if (state == _thread_in_vm) {
duke@1 810 roll_forward(_call_back);
duke@1 811 return;
duke@1 812 }
duke@1 813
duke@1 814 // All other thread states will continue to run until they
duke@1 815 // transition and self-block in state _blocked
duke@1 816 // Safepoint polling in compiled code causes the Java threads to do the same.
duke@1 817 // Note: new threads may require a malloc so they must be allowed to finish
duke@1 818
duke@1 819 assert(is_running(), "examine_state_of_thread on non-running thread");
duke@1 820 return;
duke@1 821 }
duke@1 822
duke@1 823 // Returns true is thread could not be rolled forward at present position.
duke@1 824 void ThreadSafepointState::roll_forward(suspend_type type) {
duke@1 825 _type = type;
duke@1 826
duke@1 827 switch(_type) {
duke@1 828 case _at_safepoint:
duke@1 829 SafepointSynchronize::signal_thread_at_safepoint();
duke@1 830 break;
duke@1 831
duke@1 832 case _call_back:
duke@1 833 set_has_called_back(false);
duke@1 834 break;
duke@1 835
duke@1 836 case _running:
duke@1 837 default:
duke@1 838 ShouldNotReachHere();
duke@1 839 }
duke@1 840 }
duke@1 841
duke@1 842 void ThreadSafepointState::restart() {
duke@1 843 switch(type()) {
duke@1 844 case _at_safepoint:
duke@1 845 case _call_back:
duke@1 846 break;
duke@1 847
duke@1 848 case _running:
duke@1 849 default:
duke@1 850 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
duke@1 851 _thread, _type);
duke@1 852 _thread->print();
duke@1 853 ShouldNotReachHere();
duke@1 854 }
duke@1 855 _type = _running;
duke@1 856 set_has_called_back(false);
duke@1 857 }
duke@1 858
duke@1 859
duke@1 860 void ThreadSafepointState::print_on(outputStream *st) const {
duke@1 861 const char *s;
duke@1 862
duke@1 863 switch(_type) {
duke@1 864 case _running : s = "_running"; break;
duke@1 865 case _at_safepoint : s = "_at_safepoint"; break;
duke@1 866 case _call_back : s = "_call_back"; break;
duke@1 867 default:
duke@1 868 ShouldNotReachHere();
duke@1 869 }
duke@1 870
duke@1 871 st->print_cr("Thread: " INTPTR_FORMAT
duke@1 872 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
duke@1 873 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
duke@1 874 _at_poll_safepoint);
duke@1 875
duke@1 876 _thread->print_thread_state_on(st);
duke@1 877 }
duke@1 878
duke@1 879
duke@1 880 // ---------------------------------------------------------------------------------------------------------------------
duke@1 881
duke@1 882 // Block the thread at the safepoint poll or poll return.
duke@1 883 void ThreadSafepointState::handle_polling_page_exception() {
duke@1 884
duke@1 885 // Check state. block() will set thread state to thread_in_vm which will
duke@1 886 // cause the safepoint state _type to become _call_back.
duke@1 887 assert(type() == ThreadSafepointState::_running,
duke@1 888 "polling page exception on thread not running state");
duke@1 889
duke@1 890 // Step 1: Find the nmethod from the return address
duke@1 891 if (ShowSafepointMsgs && Verbose) {
duke@1 892 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
duke@1 893 }
duke@1 894 address real_return_addr = thread()->saved_exception_pc();
duke@1 895
duke@1 896 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
duke@1 897 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
duke@1 898 nmethod* nm = (nmethod*)cb;
duke@1 899
duke@1 900 // Find frame of caller
duke@1 901 frame stub_fr = thread()->last_frame();
duke@1 902 CodeBlob* stub_cb = stub_fr.cb();
duke@1 903 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
duke@1 904 RegisterMap map(thread(), true);
duke@1 905 frame caller_fr = stub_fr.sender(&map);
duke@1 906
duke@1 907 // Should only be poll_return or poll
duke@1 908 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
duke@1 909
duke@1 910 // This is a poll immediately before a return. The exception handling code
duke@1 911 // has already had the effect of causing the return to occur, so the execution
duke@1 912 // will continue immediately after the call. In addition, the oopmap at the
duke@1 913 // return point does not mark the return value as an oop (if it is), so
duke@1 914 // it needs a handle here to be updated.
duke@1 915 if( nm->is_at_poll_return(real_return_addr) ) {
duke@1 916 // See if return type is an oop.
duke@1 917 bool return_oop = nm->method()->is_returning_oop();
duke@1 918 Handle return_value;
duke@1 919 if (return_oop) {
duke@1 920 // The oop result has been saved on the stack together with all
duke@1 921 // the other registers. In order to preserve it over GCs we need
duke@1 922 // to keep it in a handle.
duke@1 923 oop result = caller_fr.saved_oop_result(&map);
duke@1 924 assert(result == NULL || result->is_oop(), "must be oop");
duke@1 925 return_value = Handle(thread(), result);
duke@1 926 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
duke@1 927 }
duke@1 928
duke@1 929 // Block the thread
duke@1 930 SafepointSynchronize::block(thread());
duke@1 931
duke@1 932 // restore oop result, if any
duke@1 933 if (return_oop) {
duke@1 934 caller_fr.set_saved_oop_result(&map, return_value());
duke@1 935 }
duke@1 936 }
duke@1 937
duke@1 938 // This is a safepoint poll. Verify the return address and block.
duke@1 939 else {
duke@1 940 set_at_poll_safepoint(true);
duke@1 941
duke@1 942 // verify the blob built the "return address" correctly
duke@1 943 assert(real_return_addr == caller_fr.pc(), "must match");
duke@1 944
duke@1 945 // Block the thread
duke@1 946 SafepointSynchronize::block(thread());
duke@1 947 set_at_poll_safepoint(false);
duke@1 948
duke@1 949 // If we have a pending async exception deoptimize the frame
duke@1 950 // as otherwise we may never deliver it.
duke@1 951 if (thread()->has_async_condition()) {
duke@1 952 ThreadInVMfromJavaNoAsyncException __tiv(thread());
duke@1 953 VM_DeoptimizeFrame deopt(thread(), caller_fr.id());
duke@1 954 VMThread::execute(&deopt);
duke@1 955 }
duke@1 956
duke@1 957 // If an exception has been installed we must check for a pending deoptimization
duke@1 958 // Deoptimize frame if exception has been thrown.
duke@1 959
duke@1 960 if (thread()->has_pending_exception() ) {
duke@1 961 RegisterMap map(thread(), true);
duke@1 962 frame caller_fr = stub_fr.sender(&map);
duke@1 963 if (caller_fr.is_deoptimized_frame()) {
duke@1 964 // The exception patch will destroy registers that are still
duke@1 965 // live and will be needed during deoptimization. Defer the
duke@1 966 // Async exception should have defered the exception until the
duke@1 967 // next safepoint which will be detected when we get into
duke@1 968 // the interpreter so if we have an exception now things
duke@1 969 // are messed up.
duke@1 970
duke@1 971 fatal("Exception installed and deoptimization is pending");
duke@1 972 }
duke@1 973 }
duke@1 974 }
duke@1 975 }
duke@1 976
duke@1 977
duke@1 978 //
duke@1 979 // Statistics & Instrumentations
duke@1 980 //
duke@1 981 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
duke@1 982 int SafepointSynchronize::_cur_stat_index = 0;
duke@1 983 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
duke@1 984 julong SafepointSynchronize::_coalesced_vmop_count = 0;
duke@1 985 jlong SafepointSynchronize::_max_sync_time = 0;
duke@1 986
duke@1 987 // last_safepoint_start_time records the start time of last safepoint.
duke@1 988 static jlong last_safepoint_start_time = 0;
duke@1 989 static jlong sync_end_time = 0;
duke@1 990 static bool need_to_track_page_armed_status = false;
duke@1 991 static bool init_done = false;
duke@1 992
duke@1 993 void SafepointSynchronize::deferred_initialize_stat() {
duke@1 994 if (init_done) return;
duke@1 995
duke@1 996 if (PrintSafepointStatisticsCount <= 0) {
duke@1 997 fatal("Wrong PrintSafepointStatisticsCount");
duke@1 998 }
duke@1 999
duke@1 1000 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
duke@1 1001 // be printed right away, in which case, _safepoint_stats will regress to
duke@1 1002 // a single element array. Otherwise, it is a circular ring buffer with default
duke@1 1003 // size of PrintSafepointStatisticsCount.
duke@1 1004 int stats_array_size;
duke@1 1005 if (PrintSafepointStatisticsTimeout > 0) {
duke@1 1006 stats_array_size = 1;
duke@1 1007 PrintSafepointStatistics = true;
duke@1 1008 } else {
duke@1 1009 stats_array_size = PrintSafepointStatisticsCount;
duke@1 1010 }
duke@1 1011 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
duke@1 1012 * sizeof(SafepointStats));
duke@1 1013 guarantee(_safepoint_stats != NULL,
duke@1 1014 "not enough memory for safepoint instrumentation data");
duke@1 1015
duke@1 1016 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
duke@1 1017 need_to_track_page_armed_status = true;
duke@1 1018 }
duke@1 1019
duke@1 1020 tty->print(" vmop_name "
duke@1 1021 "[threads: total initially_running wait_to_block] ");
duke@1 1022 tty->print("[time: spin block sync] "
duke@1 1023 "[vmop_time time_elapsed] ");
duke@1 1024
duke@1 1025 // no page armed status printed out if it is always armed.
duke@1 1026 if (need_to_track_page_armed_status) {
duke@1 1027 tty->print("page_armed ");
duke@1 1028 }
duke@1 1029
duke@1 1030 tty->print_cr("page_trap_count");
duke@1 1031
duke@1 1032 init_done = true;
duke@1 1033 }
duke@1 1034
duke@1 1035 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
xlu@4006 1036 assert(init_done, "safepoint statistics array hasn't been initialized");
duke@1 1037 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1038
duke@1 1039 VM_Operation *op = VMThread::vm_operation();
duke@1 1040 spstat->_vmop_type = (op != NULL ? op->type() : -1);
duke@1 1041 if (op != NULL) {
duke@1 1042 _safepoint_reasons[spstat->_vmop_type]++;
duke@1 1043 }
duke@1 1044
duke@1 1045 spstat->_nof_total_threads = nof_threads;
duke@1 1046 spstat->_nof_initial_running_threads = nof_running;
duke@1 1047 spstat->_nof_threads_hit_page_trap = 0;
duke@1 1048
duke@1 1049 // Records the start time of spinning. The real time spent on spinning
duke@1 1050 // will be adjusted when spin is done. Same trick is applied for time
duke@1 1051 // spent on waiting for threads to block.
duke@1 1052 if (nof_running != 0) {
duke@1 1053 spstat->_time_to_spin = os::javaTimeNanos();
duke@1 1054 } else {
duke@1 1055 spstat->_time_to_spin = 0;
duke@1 1056 }
duke@1 1057
duke@1 1058 if (last_safepoint_start_time == 0) {
duke@1 1059 spstat->_time_elapsed_since_last_safepoint = 0;
duke@1 1060 } else {
duke@1 1061 spstat->_time_elapsed_since_last_safepoint = _last_safepoint -
duke@1 1062 last_safepoint_start_time;
duke@1 1063 }
duke@1 1064 last_safepoint_start_time = _last_safepoint;
duke@1 1065 }
duke@1 1066
duke@1 1067 void SafepointSynchronize::update_statistics_on_spin_end() {
duke@1 1068 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1069
duke@1 1070 jlong cur_time = os::javaTimeNanos();
duke@1 1071
duke@1 1072 spstat->_nof_threads_wait_to_block = _waiting_to_block;
duke@1 1073 if (spstat->_nof_initial_running_threads != 0) {
duke@1 1074 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
duke@1 1075 }
duke@1 1076
duke@1 1077 if (need_to_track_page_armed_status) {
duke@1 1078 spstat->_page_armed = (PageArmed == 1);
duke@1 1079 }
duke@1 1080
duke@1 1081 // Records the start time of waiting for to block. Updated when block is done.
duke@1 1082 if (_waiting_to_block != 0) {
duke@1 1083 spstat->_time_to_wait_to_block = cur_time;
duke@1 1084 } else {
duke@1 1085 spstat->_time_to_wait_to_block = 0;
duke@1 1086 }
duke@1 1087 }
duke@1 1088
duke@1 1089 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
duke@1 1090 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1091
duke@1 1092 if (spstat->_nof_threads_wait_to_block != 0) {
duke@1 1093 spstat->_time_to_wait_to_block = end_time -
duke@1 1094 spstat->_time_to_wait_to_block;
duke@1 1095 }
duke@1 1096
duke@1 1097 // Records the end time of sync which will be used to calculate the total
duke@1 1098 // vm operation time. Again, the real time spending in syncing will be deducted
duke@1 1099 // from the start of the sync time later when end_statistics is called.
duke@1 1100 spstat->_time_to_sync = end_time - _last_safepoint;
duke@1 1101 if (spstat->_time_to_sync > _max_sync_time) {
duke@1 1102 _max_sync_time = spstat->_time_to_sync;
duke@1 1103 }
duke@1 1104 sync_end_time = end_time;
duke@1 1105 }
duke@1 1106
duke@1 1107 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
duke@1 1108 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1109
duke@1 1110 // Update the vm operation time.
duke@1 1111 spstat->_time_to_exec_vmop = vmop_end_time - sync_end_time;
duke@1 1112 // Only the sync time longer than the specified
duke@1 1113 // PrintSafepointStatisticsTimeout will be printed out right away.
duke@1 1114 // By default, it is -1 meaning all samples will be put into the list.
duke@1 1115 if ( PrintSafepointStatisticsTimeout > 0) {
duke@1 1116 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1117 print_statistics();
duke@1 1118 }
duke@1 1119 } else {
duke@1 1120 // The safepoint statistics will be printed out when the _safepoin_stats
duke@1 1121 // array fills up.
duke@1 1122 if (_cur_stat_index != PrintSafepointStatisticsCount - 1) {
duke@1 1123 _cur_stat_index ++;
duke@1 1124 } else {
duke@1 1125 print_statistics();
duke@1 1126 _cur_stat_index = 0;
duke@1 1127 tty->print_cr("");
duke@1 1128 }
duke@1 1129 }
duke@1 1130 }
duke@1 1131
duke@1 1132 void SafepointSynchronize::print_statistics() {
duke@1 1133 int index;
duke@1 1134 SafepointStats* sstats = _safepoint_stats;
duke@1 1135
duke@1 1136 for (index = 0; index <= _cur_stat_index; index++) {
duke@1 1137 sstats = &_safepoint_stats[index];
duke@1 1138 tty->print("%-28s ["
duke@1 1139 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
duke@1 1140 "] ",
duke@1 1141 sstats->_vmop_type == -1 ? "no vm operation" :
duke@1 1142 VM_Operation::name(sstats->_vmop_type),
duke@1 1143 sstats->_nof_total_threads,
duke@1 1144 sstats->_nof_initial_running_threads,
duke@1 1145 sstats->_nof_threads_wait_to_block);
duke@1 1146 // "/ MICROUNITS " is to convert the unit from nanos to millis.
duke@1 1147 tty->print(" ["
duke@1 1148 INT64_FORMAT_W(6)INT64_FORMAT_W(6)INT64_FORMAT_W(6)
duke@1 1149 "] "
duke@1 1150 "["INT64_FORMAT_W(6)INT64_FORMAT_W(9) "] ",
duke@1 1151 sstats->_time_to_spin / MICROUNITS,
duke@1 1152 sstats->_time_to_wait_to_block / MICROUNITS,
duke@1 1153 sstats->_time_to_sync / MICROUNITS,
duke@1 1154 sstats->_time_to_exec_vmop / MICROUNITS,
duke@1 1155 sstats->_time_elapsed_since_last_safepoint / MICROUNITS);
duke@1 1156
duke@1 1157 if (need_to_track_page_armed_status) {
duke@1 1158 tty->print(INT32_FORMAT" ", sstats->_page_armed);
duke@1 1159 }
duke@1 1160 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
duke@1 1161 }
duke@1 1162 }
duke@1 1163
duke@1 1164 // This method will be called when VM exits. It will first call
duke@1 1165 // print_statistics to print out the rest of the sampling. Then
duke@1 1166 // it tries to summarize the sampling.
duke@1 1167 void SafepointSynchronize::print_stat_on_exit() {
duke@1 1168 if (_safepoint_stats == NULL) return;
duke@1 1169
duke@1 1170 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1171
duke@1 1172 // During VM exit, end_statistics may not get called and in that
duke@1 1173 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
duke@1 1174 // don't print it out.
duke@1 1175 // Approximate the vm op time.
duke@1 1176 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
duke@1 1177 os::javaTimeNanos() - sync_end_time;
duke@1 1178
duke@1 1179 if ( PrintSafepointStatisticsTimeout < 0 ||
duke@1 1180 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1181 print_statistics();
duke@1 1182 }
duke@1 1183 tty->print_cr("");
duke@1 1184
duke@1 1185 // Print out polling page sampling status.
duke@1 1186 if (!need_to_track_page_armed_status) {
duke@1 1187 if (UseCompilerSafepoints) {
duke@1 1188 tty->print_cr("Polling page always armed");
duke@1 1189 }
duke@1 1190 } else {
duke@1 1191 tty->print_cr("Defer polling page loop count = %d\n",
duke@1 1192 DeferPollingPageLoopCount);
duke@1 1193 }
duke@1 1194
duke@1 1195 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
duke@1 1196 if (_safepoint_reasons[index] != 0) {
duke@1 1197 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
duke@1 1198 _safepoint_reasons[index]);
duke@1 1199 }
duke@1 1200 }
duke@1 1201
duke@1 1202 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
duke@1 1203 _coalesced_vmop_count);
duke@1 1204 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
duke@1 1205 _max_sync_time / MICROUNITS);
duke@1 1206 }
duke@1 1207
duke@1 1208 // ------------------------------------------------------------------------------------------------
duke@1 1209 // Non-product code
duke@1 1210
duke@1 1211 #ifndef PRODUCT
duke@1 1212
duke@1 1213 void SafepointSynchronize::print_state() {
duke@1 1214 if (_state == _not_synchronized) {
duke@1 1215 tty->print_cr("not synchronized");
duke@1 1216 } else if (_state == _synchronizing || _state == _synchronized) {
duke@1 1217 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
duke@1 1218 "synchronized");
duke@1 1219
duke@1 1220 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 1221 cur->safepoint_state()->print();
duke@1 1222 }
duke@1 1223 }
duke@1 1224 }
duke@1 1225
duke@1 1226 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
duke@1 1227 if (ShowSafepointMsgs) {
duke@1 1228 va_list ap;
duke@1 1229 va_start(ap, format);
duke@1 1230 tty->vprint_cr(format, ap);
duke@1 1231 va_end(ap);
duke@1 1232 }
duke@1 1233 }
duke@1 1234
duke@1 1235 #endif // !PRODUCT