annotate hotspot/src/share/vm/runtime/safepoint.cpp @ 1:489c9b5090e2

Initial load
author duke
date Sat, 01 Dec 2007 00:00:00 +0000
parents
children 24b003a6fe46
rev   line source
duke@1 1 /*
duke@1 2 * Copyright 1997-2007 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);
duke@1 52 } else {
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
duke@1 84 // Begin the process of bringing the system to a safepoint.
duke@1 85 // Java threads can be in several different states and are
duke@1 86 // stopped by different mechanisms:
duke@1 87 //
duke@1 88 // 1. Running interpreted
duke@1 89 // The interpeter dispatch table is changed to force it to
duke@1 90 // check for a safepoint condition between bytecodes.
duke@1 91 // 2. Running in native code
duke@1 92 // When returning from the native code, a Java thread must check
duke@1 93 // the safepoint _state to see if we must block. If the
duke@1 94 // VM thread sees a Java thread in native, it does
duke@1 95 // not wait for this thread to block. The order of the memory
duke@1 96 // writes and reads of both the safepoint state and the Java
duke@1 97 // threads state is critical. In order to guarantee that the
duke@1 98 // memory writes are serialized with respect to each other,
duke@1 99 // the VM thread issues a memory barrier instruction
duke@1 100 // (on MP systems). In order to avoid the overhead of issuing
duke@1 101 // a memory barrier for each Java thread making native calls, each Java
duke@1 102 // thread performs a write to a single memory page after changing
duke@1 103 // the thread state. The VM thread performs a sequence of
duke@1 104 // mprotect OS calls which forces all previous writes from all
duke@1 105 // Java threads to be serialized. This is done in the
duke@1 106 // os::serialize_thread_states() call. This has proven to be
duke@1 107 // much more efficient than executing a membar instruction
duke@1 108 // on every call to native code.
duke@1 109 // 3. Running compiled Code
duke@1 110 // Compiled code reads a global (Safepoint Polling) page that
duke@1 111 // is set to fault if we are trying to get to a safepoint.
duke@1 112 // 4. Blocked
duke@1 113 // A thread which is blocked will not be allowed to return from the
duke@1 114 // block condition until the safepoint operation is complete.
duke@1 115 // 5. In VM or Transitioning between states
duke@1 116 // If a Java thread is currently running in the VM or transitioning
duke@1 117 // between states, the safepointing code will wait for the thread to
duke@1 118 // block itself when it attempts transitions to a new state.
duke@1 119 //
duke@1 120 _state = _synchronizing;
duke@1 121 OrderAccess::fence();
duke@1 122
duke@1 123 // Flush all thread states to memory
duke@1 124 if (!UseMembar) {
duke@1 125 os::serialize_thread_states();
duke@1 126 }
duke@1 127
duke@1 128 // Make interpreter safepoint aware
duke@1 129 Interpreter::notice_safepoints();
duke@1 130
duke@1 131 if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) {
duke@1 132 // Make polling safepoint aware
duke@1 133 guarantee (PageArmed == 0, "invariant") ;
duke@1 134 PageArmed = 1 ;
duke@1 135 os::make_polling_page_unreadable();
duke@1 136 }
duke@1 137
duke@1 138 // Consider using active_processor_count() ... but that call is expensive.
duke@1 139 int ncpus = os::processor_count() ;
duke@1 140
duke@1 141 #ifdef ASSERT
duke@1 142 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
duke@1 143 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
duke@1 144 }
duke@1 145 #endif // ASSERT
duke@1 146
duke@1 147 if (SafepointTimeout)
duke@1 148 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
duke@1 149
duke@1 150 // Iterate through all threads until it have been determined how to stop them all at a safepoint
duke@1 151 unsigned int iterations = 0;
duke@1 152 int steps = 0 ;
duke@1 153 while(still_running > 0) {
duke@1 154 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
duke@1 155 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
duke@1 156 ThreadSafepointState *cur_state = cur->safepoint_state();
duke@1 157 if (cur_state->is_running()) {
duke@1 158 cur_state->examine_state_of_thread();
duke@1 159 if (!cur_state->is_running()) {
duke@1 160 still_running--;
duke@1 161 // consider adjusting steps downward:
duke@1 162 // steps = 0
duke@1 163 // steps -= NNN
duke@1 164 // steps >>= 1
duke@1 165 // steps = MIN(steps, 2000-100)
duke@1 166 // if (iterations != 0) steps -= NNN
duke@1 167 }
duke@1 168 if (TraceSafepoint && Verbose) cur_state->print();
duke@1 169 }
duke@1 170 }
duke@1 171
duke@1 172 if ( (PrintSafepointStatistics || (PrintSafepointStatisticsTimeout > 0))
duke@1 173 && iterations == 0) {
duke@1 174 begin_statistics(nof_threads, still_running);
duke@1 175 }
duke@1 176
duke@1 177 if (still_running > 0) {
duke@1 178 // Check for if it takes to long
duke@1 179 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
duke@1 180 print_safepoint_timeout(_spinning_timeout);
duke@1 181 }
duke@1 182
duke@1 183 // Spin to avoid context switching.
duke@1 184 // There's a tension between allowing the mutators to run (and rendezvous)
duke@1 185 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
duke@1 186 // a mutator might otherwise use profitably to reach a safepoint. Excessive
duke@1 187 // spinning by the VM thread on a saturated system can increase rendezvous latency.
duke@1 188 // Blocking or yielding incur their own penalties in the form of context switching
duke@1 189 // and the resultant loss of $ residency.
duke@1 190 //
duke@1 191 // Further complicating matters is that yield() does not work as naively expected
duke@1 192 // on many platforms -- yield() does not guarantee that any other ready threads
duke@1 193 // will run. As such we revert yield_all() after some number of iterations.
duke@1 194 // Yield_all() is implemented as a short unconditional sleep on some platforms.
duke@1 195 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
duke@1 196 // can actually increase the time it takes the VM thread to detect that a system-wide
duke@1 197 // stop-the-world safepoint has been reached. In a pathological scenario such as that
duke@1 198 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
duke@1 199 // In that case the mutators will be stalled waiting for the safepoint to complete and the
duke@1 200 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
duke@1 201 // will eventually wake up and detect that all mutators are safe, at which point
duke@1 202 // we'll again make progress.
duke@1 203 //
duke@1 204 // Beware too that that the VMThread typically runs at elevated priority.
duke@1 205 // Its default priority is higher than the default mutator priority.
duke@1 206 // Obviously, this complicates spinning.
duke@1 207 //
duke@1 208 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
duke@1 209 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
duke@1 210 //
duke@1 211 // See the comments in synchronizer.cpp for additional remarks on spinning.
duke@1 212 //
duke@1 213 // In the future we might:
duke@1 214 // 1. Modify the safepoint scheme to avoid potentally unbounded spinning.
duke@1 215 // This is tricky as the path used by a thread exiting the JVM (say on
duke@1 216 // on JNI call-out) simply stores into its state field. The burden
duke@1 217 // is placed on the VM thread, which must poll (spin).
duke@1 218 // 2. Find something useful to do while spinning. If the safepoint is GC-related
duke@1 219 // we might aggressively scan the stacks of threads that are already safe.
duke@1 220 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
duke@1 221 // If all the mutators are ONPROC there's no reason to sleep or yield.
duke@1 222 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
duke@1 223 // 5. Check system saturation. If the system is not fully saturated then
duke@1 224 // simply spin and avoid sleep/yield.
duke@1 225 // 6. As still-running mutators rendezvous they could unpark the sleeping
duke@1 226 // VMthread. This works well for still-running mutators that become
duke@1 227 // safe. The VMthread must still poll for mutators that call-out.
duke@1 228 // 7. Drive the policy on time-since-begin instead of iterations.
duke@1 229 // 8. Consider making the spin duration a function of the # of CPUs:
duke@1 230 // Spin = (((ncpus-1) * M) + K) + F(still_running)
duke@1 231 // Alternately, instead of counting iterations of the outer loop
duke@1 232 // we could count the # of threads visited in the inner loop, above.
duke@1 233 // 9. On windows consider using the return value from SwitchThreadTo()
duke@1 234 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
duke@1 235
duke@1 236 if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) {
duke@1 237 guarantee (PageArmed == 0, "invariant") ;
duke@1 238 PageArmed = 1 ;
duke@1 239 os::make_polling_page_unreadable();
duke@1 240 }
duke@1 241
duke@1 242 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
duke@1 243 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
duke@1 244 ++steps ;
duke@1 245 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
duke@1 246 SpinPause() ; // MP-Polite spin
duke@1 247 } else
duke@1 248 if (steps < DeferThrSuspendLoopCount) {
duke@1 249 os::NakedYield() ;
duke@1 250 } else {
duke@1 251 os::yield_all(steps) ;
duke@1 252 // Alternately, the VM thread could transiently depress its scheduling priority or
duke@1 253 // transiently increase the priority of the tardy mutator(s).
duke@1 254 }
duke@1 255
duke@1 256 iterations ++ ;
duke@1 257 }
duke@1 258 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
duke@1 259 }
duke@1 260 assert(still_running == 0, "sanity check");
duke@1 261
duke@1 262 if (PrintSafepointStatistics) {
duke@1 263 update_statistics_on_spin_end();
duke@1 264 }
duke@1 265
duke@1 266 // wait until all threads are stopped
duke@1 267 while (_waiting_to_block > 0) {
duke@1 268 if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block);
duke@1 269 if (!SafepointTimeout || timeout_error_printed) {
duke@1 270 Safepoint_lock->wait(true); // true, means with no safepoint checks
duke@1 271 } else {
duke@1 272 // Compute remaining time
duke@1 273 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
duke@1 274
duke@1 275 // If there is no remaining time, then there is an error
duke@1 276 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
duke@1 277 print_safepoint_timeout(_blocking_timeout);
duke@1 278 }
duke@1 279 }
duke@1 280 }
duke@1 281 assert(_waiting_to_block == 0, "sanity check");
duke@1 282
duke@1 283 #ifndef PRODUCT
duke@1 284 if (SafepointTimeout) {
duke@1 285 jlong current_time = os::javaTimeNanos();
duke@1 286 if (safepoint_limit_time < current_time) {
duke@1 287 tty->print_cr("# SafepointSynchronize: Finished after "
duke@1 288 INT64_FORMAT_W(6) " ms",
duke@1 289 ((current_time - safepoint_limit_time) / MICROUNITS +
duke@1 290 SafepointTimeoutDelay));
duke@1 291 }
duke@1 292 }
duke@1 293 #endif
duke@1 294
duke@1 295 assert((_safepoint_counter & 0x1) == 0, "must be even");
duke@1 296 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 297 _safepoint_counter ++;
duke@1 298
duke@1 299 // Record state
duke@1 300 _state = _synchronized;
duke@1 301
duke@1 302 OrderAccess::fence();
duke@1 303
duke@1 304 if (TraceSafepoint) {
duke@1 305 VM_Operation *op = VMThread::vm_operation();
duke@1 306 tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation");
duke@1 307 }
duke@1 308
duke@1 309 RuntimeService::record_safepoint_synchronized();
duke@1 310 if (PrintSafepointStatistics) {
duke@1 311 update_statistics_on_sync_end(os::javaTimeNanos());
duke@1 312 }
duke@1 313
duke@1 314 // Call stuff that needs to be run when a safepoint is just about to be completed
duke@1 315 do_cleanup_tasks();
duke@1 316 }
duke@1 317 }
duke@1 318
duke@1 319 // Wake up all threads, so they are ready to resume execution after the safepoint
duke@1 320 // operation has been carried out
duke@1 321 void SafepointSynchronize::end() {
duke@1 322
duke@1 323 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 324 assert((_safepoint_counter & 0x1) == 1, "must be odd");
duke@1 325 _safepoint_counter ++;
duke@1 326 // memory fence isn't required here since an odd _safepoint_counter
duke@1 327 // value can do no harm and a fence is issued below anyway.
duke@1 328
duke@1 329 DEBUG_ONLY(Thread* myThread = Thread::current();)
duke@1 330 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
duke@1 331
duke@1 332 if (PrintSafepointStatistics) {
duke@1 333 end_statistics(os::javaTimeNanos());
duke@1 334 }
duke@1 335
duke@1 336 #ifdef ASSERT
duke@1 337 // A pending_exception cannot be installed during a safepoint. The threads
duke@1 338 // may install an async exception after they come back from a safepoint into
duke@1 339 // pending_exception after they unblock. But that should happen later.
duke@1 340 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 341 assert (!(cur->has_pending_exception() &&
duke@1 342 cur->safepoint_state()->is_at_poll_safepoint()),
duke@1 343 "safepoint installed a pending exception");
duke@1 344 }
duke@1 345 #endif // ASSERT
duke@1 346
duke@1 347 if (PageArmed) {
duke@1 348 // Make polling safepoint aware
duke@1 349 os::make_polling_page_readable();
duke@1 350 PageArmed = 0 ;
duke@1 351 }
duke@1 352
duke@1 353 // Remove safepoint check from interpreter
duke@1 354 Interpreter::ignore_safepoints();
duke@1 355
duke@1 356 {
duke@1 357 MutexLocker mu(Safepoint_lock);
duke@1 358
duke@1 359 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
duke@1 360
duke@1 361 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
duke@1 362 // when they get restarted.
duke@1 363 _state = _not_synchronized;
duke@1 364 OrderAccess::fence();
duke@1 365
duke@1 366 if (TraceSafepoint) {
duke@1 367 tty->print_cr("Leaving safepoint region");
duke@1 368 }
duke@1 369
duke@1 370 // Start suspended threads
duke@1 371 for(JavaThread *current = Threads::first(); current; current = current->next()) {
duke@1 372 // A problem occuring on Solaris is when attempting to restart threads
duke@1 373 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
duke@1 374 // to the next one (since it has been running the longest). We then have
duke@1 375 // to wait for a cpu to become available before we can continue restarting
duke@1 376 // threads.
duke@1 377 // FIXME: This causes the performance of the VM to degrade when active and with
duke@1 378 // large numbers of threads. Apparently this is due to the synchronous nature
duke@1 379 // of suspending threads.
duke@1 380 //
duke@1 381 // TODO-FIXME: the comments above are vestigial and no longer apply.
duke@1 382 // Furthermore, using solaris' schedctl in this particular context confers no benefit
duke@1 383 if (VMThreadHintNoPreempt) {
duke@1 384 os::hint_no_preempt();
duke@1 385 }
duke@1 386 ThreadSafepointState* cur_state = current->safepoint_state();
duke@1 387 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
duke@1 388 cur_state->restart();
duke@1 389 assert(cur_state->is_running(), "safepoint state has not been reset");
duke@1 390 }
duke@1 391
duke@1 392 RuntimeService::record_safepoint_end();
duke@1 393
duke@1 394 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
duke@1 395 // blocked in signal_thread_blocked
duke@1 396 Threads_lock->unlock();
duke@1 397
duke@1 398 }
duke@1 399 #ifndef SERIALGC
duke@1 400 // If there are any concurrent GC threads resume them.
duke@1 401 if (UseConcMarkSweepGC) {
duke@1 402 ConcurrentMarkSweepThread::desynchronize(false);
duke@1 403 } else {
duke@1 404 ConcurrentGCThread::safepoint_desynchronize();
duke@1 405 }
duke@1 406 #endif // SERIALGC
duke@1 407 }
duke@1 408
duke@1 409 bool SafepointSynchronize::is_cleanup_needed() {
duke@1 410 // Need a safepoint if some inline cache buffers is non-empty
duke@1 411 if (!InlineCacheBuffer::is_empty()) return true;
duke@1 412 return false;
duke@1 413 }
duke@1 414
duke@1 415 jlong CounterDecay::_last_timestamp = 0;
duke@1 416
duke@1 417 static void do_method(methodOop m) {
duke@1 418 m->invocation_counter()->decay();
duke@1 419 }
duke@1 420
duke@1 421 void CounterDecay::decay() {
duke@1 422 _last_timestamp = os::javaTimeMillis();
duke@1 423
duke@1 424 // This operation is going to be performed only at the end of a safepoint
duke@1 425 // and hence GC's will not be going on, all Java mutators are suspended
duke@1 426 // at this point and hence SystemDictionary_lock is also not needed.
duke@1 427 assert(SafepointSynchronize::is_at_safepoint(), "can only be executed at a safepoint");
duke@1 428 int nclasses = SystemDictionary::number_of_classes();
duke@1 429 double classes_per_tick = nclasses * (CounterDecayMinIntervalLength * 1e-3 /
duke@1 430 CounterHalfLifeTime);
duke@1 431 for (int i = 0; i < classes_per_tick; i++) {
duke@1 432 klassOop k = SystemDictionary::try_get_next_class();
duke@1 433 if (k != NULL && k->klass_part()->oop_is_instance()) {
duke@1 434 instanceKlass::cast(k)->methods_do(do_method);
duke@1 435 }
duke@1 436 }
duke@1 437 }
duke@1 438
duke@1 439 // Various cleaning tasks that should be done periodically at safepoints
duke@1 440 void SafepointSynchronize::do_cleanup_tasks() {
duke@1 441 jlong cleanup_time;
duke@1 442
duke@1 443 // Update fat-monitor pool, since this is a safepoint.
duke@1 444 if (TraceSafepoint) {
duke@1 445 cleanup_time = os::javaTimeNanos();
duke@1 446 }
duke@1 447
duke@1 448 ObjectSynchronizer::deflate_idle_monitors();
duke@1 449 InlineCacheBuffer::update_inline_caches();
duke@1 450 if(UseCounterDecay && CounterDecay::is_decay_needed()) {
duke@1 451 CounterDecay::decay();
duke@1 452 }
duke@1 453 NMethodSweeper::sweep();
duke@1 454
duke@1 455 if (TraceSafepoint) {
duke@1 456 tty->print_cr("do_cleanup_tasks takes "INT64_FORMAT_W(6) "ms",
duke@1 457 (os::javaTimeNanos() - cleanup_time) / MICROUNITS);
duke@1 458 }
duke@1 459 }
duke@1 460
duke@1 461
duke@1 462 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
duke@1 463 switch(state) {
duke@1 464 case _thread_in_native:
duke@1 465 // native threads are safe if they have no java stack or have walkable stack
duke@1 466 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
duke@1 467
duke@1 468 // blocked threads should have already have walkable stack
duke@1 469 case _thread_blocked:
duke@1 470 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
duke@1 471 return true;
duke@1 472
duke@1 473 default:
duke@1 474 return false;
duke@1 475 }
duke@1 476 }
duke@1 477
duke@1 478
duke@1 479 // -------------------------------------------------------------------------------------------------------
duke@1 480 // Implementation of Safepoint callback point
duke@1 481
duke@1 482 void SafepointSynchronize::block(JavaThread *thread) {
duke@1 483 assert(thread != NULL, "thread must be set");
duke@1 484 assert(thread->is_Java_thread(), "not a Java thread");
duke@1 485
duke@1 486 // Threads shouldn't block if they are in the middle of printing, but...
duke@1 487 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
duke@1 488
duke@1 489 // Only bail from the block() call if the thread is gone from the
duke@1 490 // thread list; starting to exit should still block.
duke@1 491 if (thread->is_terminated()) {
duke@1 492 // block current thread if we come here from native code when VM is gone
duke@1 493 thread->block_if_vm_exited();
duke@1 494
duke@1 495 // otherwise do nothing
duke@1 496 return;
duke@1 497 }
duke@1 498
duke@1 499 JavaThreadState state = thread->thread_state();
duke@1 500 thread->frame_anchor()->make_walkable(thread);
duke@1 501
duke@1 502 // Check that we have a valid thread_state at this point
duke@1 503 switch(state) {
duke@1 504 case _thread_in_vm_trans:
duke@1 505 case _thread_in_Java: // From compiled code
duke@1 506
duke@1 507 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
duke@1 508 // we pretend we are still in the VM.
duke@1 509 thread->set_thread_state(_thread_in_vm);
duke@1 510
duke@1 511 if (is_synchronizing()) {
duke@1 512 Atomic::inc (&TryingToBlock) ;
duke@1 513 }
duke@1 514
duke@1 515 // We will always be holding the Safepoint_lock when we are examine the state
duke@1 516 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
duke@1 517 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
duke@1 518 Safepoint_lock->lock_without_safepoint_check();
duke@1 519 if (is_synchronizing()) {
duke@1 520 // Decrement the number of threads to wait for and signal vm thread
duke@1 521 assert(_waiting_to_block > 0, "sanity check");
duke@1 522 _waiting_to_block--;
duke@1 523 thread->safepoint_state()->set_has_called_back(true);
duke@1 524
duke@1 525 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
duke@1 526 if (_waiting_to_block == 0) {
duke@1 527 Safepoint_lock->notify_all();
duke@1 528 }
duke@1 529 }
duke@1 530
duke@1 531 // We transition the thread to state _thread_blocked here, but
duke@1 532 // we can't do our usual check for external suspension and then
duke@1 533 // self-suspend after the lock_without_safepoint_check() call
duke@1 534 // below because we are often called during transitions while
duke@1 535 // we hold different locks. That would leave us suspended while
duke@1 536 // holding a resource which results in deadlocks.
duke@1 537 thread->set_thread_state(_thread_blocked);
duke@1 538 Safepoint_lock->unlock();
duke@1 539
duke@1 540 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
duke@1 541 // the entire safepoint, the threads will all line up here during the safepoint.
duke@1 542 Threads_lock->lock_without_safepoint_check();
duke@1 543 // restore original state. This is important if the thread comes from compiled code, so it
duke@1 544 // will continue to execute with the _thread_in_Java state.
duke@1 545 thread->set_thread_state(state);
duke@1 546 Threads_lock->unlock();
duke@1 547 break;
duke@1 548
duke@1 549 case _thread_in_native_trans:
duke@1 550 case _thread_blocked_trans:
duke@1 551 case _thread_new_trans:
duke@1 552 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
duke@1 553 thread->print_thread_state();
duke@1 554 fatal("Deadlock in safepoint code. "
duke@1 555 "Should have called back to the VM before blocking.");
duke@1 556 }
duke@1 557
duke@1 558 // We transition the thread to state _thread_blocked here, but
duke@1 559 // we can't do our usual check for external suspension and then
duke@1 560 // self-suspend after the lock_without_safepoint_check() call
duke@1 561 // below because we are often called during transitions while
duke@1 562 // we hold different locks. That would leave us suspended while
duke@1 563 // holding a resource which results in deadlocks.
duke@1 564 thread->set_thread_state(_thread_blocked);
duke@1 565
duke@1 566 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
duke@1 567 // the safepoint code might still be waiting for it to block. We need to change the state here,
duke@1 568 // so it can see that it is at a safepoint.
duke@1 569
duke@1 570 // Block until the safepoint operation is completed.
duke@1 571 Threads_lock->lock_without_safepoint_check();
duke@1 572
duke@1 573 // Restore state
duke@1 574 thread->set_thread_state(state);
duke@1 575
duke@1 576 Threads_lock->unlock();
duke@1 577 break;
duke@1 578
duke@1 579 default:
duke@1 580 fatal1("Illegal threadstate encountered: %d", state);
duke@1 581 }
duke@1 582
duke@1 583 // Check for pending. async. exceptions or suspends - except if the
duke@1 584 // thread was blocked inside the VM. has_special_runtime_exit_condition()
duke@1 585 // is called last since it grabs a lock and we only want to do that when
duke@1 586 // we must.
duke@1 587 //
duke@1 588 // Note: we never deliver an async exception at a polling point as the
duke@1 589 // compiler may not have an exception handler for it. The polling
duke@1 590 // code will notice the async and deoptimize and the exception will
duke@1 591 // be delivered. (Polling at a return point is ok though). Sure is
duke@1 592 // a lot of bother for a deprecated feature...
duke@1 593 //
duke@1 594 // We don't deliver an async exception if the thread state is
duke@1 595 // _thread_in_native_trans so JNI functions won't be called with
duke@1 596 // a surprising pending exception. If the thread state is going back to java,
duke@1 597 // async exception is checked in check_special_condition_for_native_trans().
duke@1 598
duke@1 599 if (state != _thread_blocked_trans &&
duke@1 600 state != _thread_in_vm_trans &&
duke@1 601 thread->has_special_runtime_exit_condition()) {
duke@1 602 thread->handle_special_runtime_exit_condition(
duke@1 603 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
duke@1 604 }
duke@1 605 }
duke@1 606
duke@1 607 // ------------------------------------------------------------------------------------------------------
duke@1 608 // Exception handlers
duke@1 609
duke@1 610 #ifndef PRODUCT
duke@1 611 #ifdef _LP64
duke@1 612 #define PTR_PAD ""
duke@1 613 #else
duke@1 614 #define PTR_PAD " "
duke@1 615 #endif
duke@1 616
duke@1 617 static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) {
duke@1 618 bool is_oop = newptr ? ((oop)newptr)->is_oop() : false;
duke@1 619 tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s",
duke@1 620 oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!',
duke@1 621 newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" "));
duke@1 622 }
duke@1 623
duke@1 624 static void print_longs(jlong oldptr, jlong newptr, bool wasoop) {
duke@1 625 bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false;
duke@1 626 tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %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 #ifdef SPARC
duke@1 632 static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) {
duke@1 633 #ifdef _LP64
duke@1 634 tty->print_cr("--------+------address-----+------before-----------+-------after----------+");
duke@1 635 const int incr = 1; // Increment to skip a long, in units of intptr_t
duke@1 636 #else
duke@1 637 tty->print_cr("--------+--address-+------before-----------+-------after----------+");
duke@1 638 const int incr = 2; // Increment to skip a long, in units of intptr_t
duke@1 639 #endif
duke@1 640 tty->print_cr("---SP---|");
duke@1 641 for( int i=0; i<16; i++ ) {
duke@1 642 tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
duke@1 643 tty->print_cr("--------|");
duke@1 644 for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) {
duke@1 645 tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
duke@1 646 tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++);
duke@1 647 tty->print_cr("--------|");
duke@1 648 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@1 649 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@1 650 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@1 651 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@1 652 tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp);
duke@1 653 old_sp += incr; new_sp += incr; was_oops += incr;
duke@1 654 // Skip the floats
duke@1 655 tty->print_cr("--Float-|"PTR_FORMAT,new_sp);
duke@1 656 tty->print_cr("---FP---|");
duke@1 657 old_sp += incr*32; new_sp += incr*32; was_oops += incr*32;
duke@1 658 for( int i2=0; i2<16; i2++ ) {
duke@1 659 tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); }
duke@1 660 tty->print_cr("");
duke@1 661 }
duke@1 662 #endif // SPARC
duke@1 663 #endif // PRODUCT
duke@1 664
duke@1 665
duke@1 666 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
duke@1 667 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
duke@1 668 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
duke@1 669 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
duke@1 670
duke@1 671 // Uncomment this to get some serious before/after printing of the
duke@1 672 // Sparc safepoint-blob frame structure.
duke@1 673 /*
duke@1 674 intptr_t* sp = thread->last_Java_sp();
duke@1 675 intptr_t stack_copy[150];
duke@1 676 for( int i=0; i<150; i++ ) stack_copy[i] = sp[i];
duke@1 677 bool was_oops[150];
duke@1 678 for( int i=0; i<150; i++ )
duke@1 679 was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false;
duke@1 680 */
duke@1 681
duke@1 682 if (ShowSafepointMsgs) {
duke@1 683 tty->print("handle_polling_page_exception: ");
duke@1 684 }
duke@1 685
duke@1 686 if (PrintSafepointStatistics) {
duke@1 687 inc_page_trap_count();
duke@1 688 }
duke@1 689
duke@1 690 ThreadSafepointState* state = thread->safepoint_state();
duke@1 691
duke@1 692 state->handle_polling_page_exception();
duke@1 693 // print_me(sp,stack_copy,was_oops);
duke@1 694 }
duke@1 695
duke@1 696
duke@1 697 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
duke@1 698 if (!timeout_error_printed) {
duke@1 699 timeout_error_printed = true;
duke@1 700 // Print out the thread infor which didn't reach the safepoint for debugging
duke@1 701 // purposes (useful when there are lots of threads in the debugger).
duke@1 702 tty->print_cr("");
duke@1 703 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
duke@1 704 if (reason == _spinning_timeout) {
duke@1 705 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
duke@1 706 } else if (reason == _blocking_timeout) {
duke@1 707 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
duke@1 708 }
duke@1 709
duke@1 710 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
duke@1 711 ThreadSafepointState *cur_state;
duke@1 712 ResourceMark rm;
duke@1 713 for(JavaThread *cur_thread = Threads::first(); cur_thread;
duke@1 714 cur_thread = cur_thread->next()) {
duke@1 715 cur_state = cur_thread->safepoint_state();
duke@1 716
duke@1 717 if (cur_thread->thread_state() != _thread_blocked &&
duke@1 718 ((reason == _spinning_timeout && cur_state->is_running()) ||
duke@1 719 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
duke@1 720 tty->print("# ");
duke@1 721 cur_thread->print();
duke@1 722 tty->print_cr("");
duke@1 723 }
duke@1 724 }
duke@1 725 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
duke@1 726 }
duke@1 727
duke@1 728 // To debug the long safepoint, specify both DieOnSafepointTimeout &
duke@1 729 // ShowMessageBoxOnError.
duke@1 730 if (DieOnSafepointTimeout) {
duke@1 731 char msg[1024];
duke@1 732 VM_Operation *op = VMThread::vm_operation();
duke@1 733 sprintf(msg, "Safepoint sync time longer than %d ms detected when executing %s.",
duke@1 734 SafepointTimeoutDelay,
duke@1 735 op != NULL ? op->name() : "no vm operation");
duke@1 736 fatal(msg);
duke@1 737 }
duke@1 738 }
duke@1 739
duke@1 740
duke@1 741 // -------------------------------------------------------------------------------------------------------
duke@1 742 // Implementation of ThreadSafepointState
duke@1 743
duke@1 744 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
duke@1 745 _thread = thread;
duke@1 746 _type = _running;
duke@1 747 _has_called_back = false;
duke@1 748 _at_poll_safepoint = false;
duke@1 749 }
duke@1 750
duke@1 751 void ThreadSafepointState::create(JavaThread *thread) {
duke@1 752 ThreadSafepointState *state = new ThreadSafepointState(thread);
duke@1 753 thread->set_safepoint_state(state);
duke@1 754 }
duke@1 755
duke@1 756 void ThreadSafepointState::destroy(JavaThread *thread) {
duke@1 757 if (thread->safepoint_state()) {
duke@1 758 delete(thread->safepoint_state());
duke@1 759 thread->set_safepoint_state(NULL);
duke@1 760 }
duke@1 761 }
duke@1 762
duke@1 763 void ThreadSafepointState::examine_state_of_thread() {
duke@1 764 assert(is_running(), "better be running or just have hit safepoint poll");
duke@1 765
duke@1 766 JavaThreadState state = _thread->thread_state();
duke@1 767
duke@1 768 // Check for a thread that is suspended. Note that thread resume tries
duke@1 769 // to grab the Threads_lock which we own here, so a thread cannot be
duke@1 770 // resumed during safepoint synchronization.
duke@1 771
duke@1 772 // We check with locking because another thread that has not yet
duke@1 773 // synchronized may be trying to suspend this one.
duke@1 774 bool is_suspended = _thread->is_any_suspended_with_lock();
duke@1 775 if (is_suspended) {
duke@1 776 roll_forward(_at_safepoint);
duke@1 777 return;
duke@1 778 }
duke@1 779
duke@1 780 // Some JavaThread states have an initial safepoint state of
duke@1 781 // running, but are actually at a safepoint. We will happily
duke@1 782 // agree and update the safepoint state here.
duke@1 783 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
duke@1 784 roll_forward(_at_safepoint);
duke@1 785 return;
duke@1 786 }
duke@1 787
duke@1 788 if (state == _thread_in_vm) {
duke@1 789 roll_forward(_call_back);
duke@1 790 return;
duke@1 791 }
duke@1 792
duke@1 793 // All other thread states will continue to run until they
duke@1 794 // transition and self-block in state _blocked
duke@1 795 // Safepoint polling in compiled code causes the Java threads to do the same.
duke@1 796 // Note: new threads may require a malloc so they must be allowed to finish
duke@1 797
duke@1 798 assert(is_running(), "examine_state_of_thread on non-running thread");
duke@1 799 return;
duke@1 800 }
duke@1 801
duke@1 802 // Returns true is thread could not be rolled forward at present position.
duke@1 803 void ThreadSafepointState::roll_forward(suspend_type type) {
duke@1 804 _type = type;
duke@1 805
duke@1 806 switch(_type) {
duke@1 807 case _at_safepoint:
duke@1 808 SafepointSynchronize::signal_thread_at_safepoint();
duke@1 809 break;
duke@1 810
duke@1 811 case _call_back:
duke@1 812 set_has_called_back(false);
duke@1 813 break;
duke@1 814
duke@1 815 case _running:
duke@1 816 default:
duke@1 817 ShouldNotReachHere();
duke@1 818 }
duke@1 819 }
duke@1 820
duke@1 821 void ThreadSafepointState::restart() {
duke@1 822 switch(type()) {
duke@1 823 case _at_safepoint:
duke@1 824 case _call_back:
duke@1 825 break;
duke@1 826
duke@1 827 case _running:
duke@1 828 default:
duke@1 829 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d",
duke@1 830 _thread, _type);
duke@1 831 _thread->print();
duke@1 832 ShouldNotReachHere();
duke@1 833 }
duke@1 834 _type = _running;
duke@1 835 set_has_called_back(false);
duke@1 836 }
duke@1 837
duke@1 838
duke@1 839 void ThreadSafepointState::print_on(outputStream *st) const {
duke@1 840 const char *s;
duke@1 841
duke@1 842 switch(_type) {
duke@1 843 case _running : s = "_running"; break;
duke@1 844 case _at_safepoint : s = "_at_safepoint"; break;
duke@1 845 case _call_back : s = "_call_back"; break;
duke@1 846 default:
duke@1 847 ShouldNotReachHere();
duke@1 848 }
duke@1 849
duke@1 850 st->print_cr("Thread: " INTPTR_FORMAT
duke@1 851 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
duke@1 852 _thread, _thread->osthread()->thread_id(), s, _has_called_back,
duke@1 853 _at_poll_safepoint);
duke@1 854
duke@1 855 _thread->print_thread_state_on(st);
duke@1 856 }
duke@1 857
duke@1 858
duke@1 859 // ---------------------------------------------------------------------------------------------------------------------
duke@1 860
duke@1 861 // Block the thread at the safepoint poll or poll return.
duke@1 862 void ThreadSafepointState::handle_polling_page_exception() {
duke@1 863
duke@1 864 // Check state. block() will set thread state to thread_in_vm which will
duke@1 865 // cause the safepoint state _type to become _call_back.
duke@1 866 assert(type() == ThreadSafepointState::_running,
duke@1 867 "polling page exception on thread not running state");
duke@1 868
duke@1 869 // Step 1: Find the nmethod from the return address
duke@1 870 if (ShowSafepointMsgs && Verbose) {
duke@1 871 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc());
duke@1 872 }
duke@1 873 address real_return_addr = thread()->saved_exception_pc();
duke@1 874
duke@1 875 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
duke@1 876 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
duke@1 877 nmethod* nm = (nmethod*)cb;
duke@1 878
duke@1 879 // Find frame of caller
duke@1 880 frame stub_fr = thread()->last_frame();
duke@1 881 CodeBlob* stub_cb = stub_fr.cb();
duke@1 882 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
duke@1 883 RegisterMap map(thread(), true);
duke@1 884 frame caller_fr = stub_fr.sender(&map);
duke@1 885
duke@1 886 // Should only be poll_return or poll
duke@1 887 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
duke@1 888
duke@1 889 // This is a poll immediately before a return. The exception handling code
duke@1 890 // has already had the effect of causing the return to occur, so the execution
duke@1 891 // will continue immediately after the call. In addition, the oopmap at the
duke@1 892 // return point does not mark the return value as an oop (if it is), so
duke@1 893 // it needs a handle here to be updated.
duke@1 894 if( nm->is_at_poll_return(real_return_addr) ) {
duke@1 895 // See if return type is an oop.
duke@1 896 bool return_oop = nm->method()->is_returning_oop();
duke@1 897 Handle return_value;
duke@1 898 if (return_oop) {
duke@1 899 // The oop result has been saved on the stack together with all
duke@1 900 // the other registers. In order to preserve it over GCs we need
duke@1 901 // to keep it in a handle.
duke@1 902 oop result = caller_fr.saved_oop_result(&map);
duke@1 903 assert(result == NULL || result->is_oop(), "must be oop");
duke@1 904 return_value = Handle(thread(), result);
duke@1 905 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
duke@1 906 }
duke@1 907
duke@1 908 // Block the thread
duke@1 909 SafepointSynchronize::block(thread());
duke@1 910
duke@1 911 // restore oop result, if any
duke@1 912 if (return_oop) {
duke@1 913 caller_fr.set_saved_oop_result(&map, return_value());
duke@1 914 }
duke@1 915 }
duke@1 916
duke@1 917 // This is a safepoint poll. Verify the return address and block.
duke@1 918 else {
duke@1 919 set_at_poll_safepoint(true);
duke@1 920
duke@1 921 // verify the blob built the "return address" correctly
duke@1 922 assert(real_return_addr == caller_fr.pc(), "must match");
duke@1 923
duke@1 924 // Block the thread
duke@1 925 SafepointSynchronize::block(thread());
duke@1 926 set_at_poll_safepoint(false);
duke@1 927
duke@1 928 // If we have a pending async exception deoptimize the frame
duke@1 929 // as otherwise we may never deliver it.
duke@1 930 if (thread()->has_async_condition()) {
duke@1 931 ThreadInVMfromJavaNoAsyncException __tiv(thread());
duke@1 932 VM_DeoptimizeFrame deopt(thread(), caller_fr.id());
duke@1 933 VMThread::execute(&deopt);
duke@1 934 }
duke@1 935
duke@1 936 // If an exception has been installed we must check for a pending deoptimization
duke@1 937 // Deoptimize frame if exception has been thrown.
duke@1 938
duke@1 939 if (thread()->has_pending_exception() ) {
duke@1 940 RegisterMap map(thread(), true);
duke@1 941 frame caller_fr = stub_fr.sender(&map);
duke@1 942 if (caller_fr.is_deoptimized_frame()) {
duke@1 943 // The exception patch will destroy registers that are still
duke@1 944 // live and will be needed during deoptimization. Defer the
duke@1 945 // Async exception should have defered the exception until the
duke@1 946 // next safepoint which will be detected when we get into
duke@1 947 // the interpreter so if we have an exception now things
duke@1 948 // are messed up.
duke@1 949
duke@1 950 fatal("Exception installed and deoptimization is pending");
duke@1 951 }
duke@1 952 }
duke@1 953 }
duke@1 954 }
duke@1 955
duke@1 956
duke@1 957 //
duke@1 958 // Statistics & Instrumentations
duke@1 959 //
duke@1 960 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
duke@1 961 int SafepointSynchronize::_cur_stat_index = 0;
duke@1 962 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
duke@1 963 julong SafepointSynchronize::_coalesced_vmop_count = 0;
duke@1 964 jlong SafepointSynchronize::_max_sync_time = 0;
duke@1 965
duke@1 966 // last_safepoint_start_time records the start time of last safepoint.
duke@1 967 static jlong last_safepoint_start_time = 0;
duke@1 968 static jlong sync_end_time = 0;
duke@1 969 static bool need_to_track_page_armed_status = false;
duke@1 970 static bool init_done = false;
duke@1 971
duke@1 972 void SafepointSynchronize::deferred_initialize_stat() {
duke@1 973 if (init_done) return;
duke@1 974
duke@1 975 if (PrintSafepointStatisticsCount <= 0) {
duke@1 976 fatal("Wrong PrintSafepointStatisticsCount");
duke@1 977 }
duke@1 978
duke@1 979 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
duke@1 980 // be printed right away, in which case, _safepoint_stats will regress to
duke@1 981 // a single element array. Otherwise, it is a circular ring buffer with default
duke@1 982 // size of PrintSafepointStatisticsCount.
duke@1 983 int stats_array_size;
duke@1 984 if (PrintSafepointStatisticsTimeout > 0) {
duke@1 985 stats_array_size = 1;
duke@1 986 PrintSafepointStatistics = true;
duke@1 987 } else {
duke@1 988 stats_array_size = PrintSafepointStatisticsCount;
duke@1 989 }
duke@1 990 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
duke@1 991 * sizeof(SafepointStats));
duke@1 992 guarantee(_safepoint_stats != NULL,
duke@1 993 "not enough memory for safepoint instrumentation data");
duke@1 994
duke@1 995 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) {
duke@1 996 need_to_track_page_armed_status = true;
duke@1 997 }
duke@1 998
duke@1 999 tty->print(" vmop_name "
duke@1 1000 "[threads: total initially_running wait_to_block] ");
duke@1 1001 tty->print("[time: spin block sync] "
duke@1 1002 "[vmop_time time_elapsed] ");
duke@1 1003
duke@1 1004 // no page armed status printed out if it is always armed.
duke@1 1005 if (need_to_track_page_armed_status) {
duke@1 1006 tty->print("page_armed ");
duke@1 1007 }
duke@1 1008
duke@1 1009 tty->print_cr("page_trap_count");
duke@1 1010
duke@1 1011 init_done = true;
duke@1 1012 }
duke@1 1013
duke@1 1014 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
duke@1 1015 deferred_initialize_stat();
duke@1 1016
duke@1 1017 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1018
duke@1 1019 VM_Operation *op = VMThread::vm_operation();
duke@1 1020 spstat->_vmop_type = (op != NULL ? op->type() : -1);
duke@1 1021 if (op != NULL) {
duke@1 1022 _safepoint_reasons[spstat->_vmop_type]++;
duke@1 1023 }
duke@1 1024
duke@1 1025 spstat->_nof_total_threads = nof_threads;
duke@1 1026 spstat->_nof_initial_running_threads = nof_running;
duke@1 1027 spstat->_nof_threads_hit_page_trap = 0;
duke@1 1028
duke@1 1029 // Records the start time of spinning. The real time spent on spinning
duke@1 1030 // will be adjusted when spin is done. Same trick is applied for time
duke@1 1031 // spent on waiting for threads to block.
duke@1 1032 if (nof_running != 0) {
duke@1 1033 spstat->_time_to_spin = os::javaTimeNanos();
duke@1 1034 } else {
duke@1 1035 spstat->_time_to_spin = 0;
duke@1 1036 }
duke@1 1037
duke@1 1038 if (last_safepoint_start_time == 0) {
duke@1 1039 spstat->_time_elapsed_since_last_safepoint = 0;
duke@1 1040 } else {
duke@1 1041 spstat->_time_elapsed_since_last_safepoint = _last_safepoint -
duke@1 1042 last_safepoint_start_time;
duke@1 1043 }
duke@1 1044 last_safepoint_start_time = _last_safepoint;
duke@1 1045 }
duke@1 1046
duke@1 1047 void SafepointSynchronize::update_statistics_on_spin_end() {
duke@1 1048 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1049
duke@1 1050 jlong cur_time = os::javaTimeNanos();
duke@1 1051
duke@1 1052 spstat->_nof_threads_wait_to_block = _waiting_to_block;
duke@1 1053 if (spstat->_nof_initial_running_threads != 0) {
duke@1 1054 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
duke@1 1055 }
duke@1 1056
duke@1 1057 if (need_to_track_page_armed_status) {
duke@1 1058 spstat->_page_armed = (PageArmed == 1);
duke@1 1059 }
duke@1 1060
duke@1 1061 // Records the start time of waiting for to block. Updated when block is done.
duke@1 1062 if (_waiting_to_block != 0) {
duke@1 1063 spstat->_time_to_wait_to_block = cur_time;
duke@1 1064 } else {
duke@1 1065 spstat->_time_to_wait_to_block = 0;
duke@1 1066 }
duke@1 1067 }
duke@1 1068
duke@1 1069 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
duke@1 1070 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1071
duke@1 1072 if (spstat->_nof_threads_wait_to_block != 0) {
duke@1 1073 spstat->_time_to_wait_to_block = end_time -
duke@1 1074 spstat->_time_to_wait_to_block;
duke@1 1075 }
duke@1 1076
duke@1 1077 // Records the end time of sync which will be used to calculate the total
duke@1 1078 // vm operation time. Again, the real time spending in syncing will be deducted
duke@1 1079 // from the start of the sync time later when end_statistics is called.
duke@1 1080 spstat->_time_to_sync = end_time - _last_safepoint;
duke@1 1081 if (spstat->_time_to_sync > _max_sync_time) {
duke@1 1082 _max_sync_time = spstat->_time_to_sync;
duke@1 1083 }
duke@1 1084 sync_end_time = end_time;
duke@1 1085 }
duke@1 1086
duke@1 1087 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
duke@1 1088 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1089
duke@1 1090 // Update the vm operation time.
duke@1 1091 spstat->_time_to_exec_vmop = vmop_end_time - sync_end_time;
duke@1 1092 // Only the sync time longer than the specified
duke@1 1093 // PrintSafepointStatisticsTimeout will be printed out right away.
duke@1 1094 // By default, it is -1 meaning all samples will be put into the list.
duke@1 1095 if ( PrintSafepointStatisticsTimeout > 0) {
duke@1 1096 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1097 print_statistics();
duke@1 1098 }
duke@1 1099 } else {
duke@1 1100 // The safepoint statistics will be printed out when the _safepoin_stats
duke@1 1101 // array fills up.
duke@1 1102 if (_cur_stat_index != PrintSafepointStatisticsCount - 1) {
duke@1 1103 _cur_stat_index ++;
duke@1 1104 } else {
duke@1 1105 print_statistics();
duke@1 1106 _cur_stat_index = 0;
duke@1 1107 tty->print_cr("");
duke@1 1108 }
duke@1 1109 }
duke@1 1110 }
duke@1 1111
duke@1 1112 void SafepointSynchronize::print_statistics() {
duke@1 1113 int index;
duke@1 1114 SafepointStats* sstats = _safepoint_stats;
duke@1 1115
duke@1 1116 for (index = 0; index <= _cur_stat_index; index++) {
duke@1 1117 sstats = &_safepoint_stats[index];
duke@1 1118 tty->print("%-28s ["
duke@1 1119 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15)
duke@1 1120 "] ",
duke@1 1121 sstats->_vmop_type == -1 ? "no vm operation" :
duke@1 1122 VM_Operation::name(sstats->_vmop_type),
duke@1 1123 sstats->_nof_total_threads,
duke@1 1124 sstats->_nof_initial_running_threads,
duke@1 1125 sstats->_nof_threads_wait_to_block);
duke@1 1126 // "/ MICROUNITS " is to convert the unit from nanos to millis.
duke@1 1127 tty->print(" ["
duke@1 1128 INT64_FORMAT_W(6)INT64_FORMAT_W(6)INT64_FORMAT_W(6)
duke@1 1129 "] "
duke@1 1130 "["INT64_FORMAT_W(6)INT64_FORMAT_W(9) "] ",
duke@1 1131 sstats->_time_to_spin / MICROUNITS,
duke@1 1132 sstats->_time_to_wait_to_block / MICROUNITS,
duke@1 1133 sstats->_time_to_sync / MICROUNITS,
duke@1 1134 sstats->_time_to_exec_vmop / MICROUNITS,
duke@1 1135 sstats->_time_elapsed_since_last_safepoint / MICROUNITS);
duke@1 1136
duke@1 1137 if (need_to_track_page_armed_status) {
duke@1 1138 tty->print(INT32_FORMAT" ", sstats->_page_armed);
duke@1 1139 }
duke@1 1140 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap);
duke@1 1141 }
duke@1 1142 }
duke@1 1143
duke@1 1144 // This method will be called when VM exits. It will first call
duke@1 1145 // print_statistics to print out the rest of the sampling. Then
duke@1 1146 // it tries to summarize the sampling.
duke@1 1147 void SafepointSynchronize::print_stat_on_exit() {
duke@1 1148 if (_safepoint_stats == NULL) return;
duke@1 1149
duke@1 1150 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1151
duke@1 1152 // During VM exit, end_statistics may not get called and in that
duke@1 1153 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
duke@1 1154 // don't print it out.
duke@1 1155 // Approximate the vm op time.
duke@1 1156 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
duke@1 1157 os::javaTimeNanos() - sync_end_time;
duke@1 1158
duke@1 1159 if ( PrintSafepointStatisticsTimeout < 0 ||
duke@1 1160 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1161 print_statistics();
duke@1 1162 }
duke@1 1163 tty->print_cr("");
duke@1 1164
duke@1 1165 // Print out polling page sampling status.
duke@1 1166 if (!need_to_track_page_armed_status) {
duke@1 1167 if (UseCompilerSafepoints) {
duke@1 1168 tty->print_cr("Polling page always armed");
duke@1 1169 }
duke@1 1170 } else {
duke@1 1171 tty->print_cr("Defer polling page loop count = %d\n",
duke@1 1172 DeferPollingPageLoopCount);
duke@1 1173 }
duke@1 1174
duke@1 1175 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
duke@1 1176 if (_safepoint_reasons[index] != 0) {
duke@1 1177 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index),
duke@1 1178 _safepoint_reasons[index]);
duke@1 1179 }
duke@1 1180 }
duke@1 1181
duke@1 1182 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint",
duke@1 1183 _coalesced_vmop_count);
duke@1 1184 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms",
duke@1 1185 _max_sync_time / MICROUNITS);
duke@1 1186 }
duke@1 1187
duke@1 1188 // ------------------------------------------------------------------------------------------------
duke@1 1189 // Non-product code
duke@1 1190
duke@1 1191 #ifndef PRODUCT
duke@1 1192
duke@1 1193 void SafepointSynchronize::print_state() {
duke@1 1194 if (_state == _not_synchronized) {
duke@1 1195 tty->print_cr("not synchronized");
duke@1 1196 } else if (_state == _synchronizing || _state == _synchronized) {
duke@1 1197 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
duke@1 1198 "synchronized");
duke@1 1199
duke@1 1200 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 1201 cur->safepoint_state()->print();
duke@1 1202 }
duke@1 1203 }
duke@1 1204 }
duke@1 1205
duke@1 1206 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
duke@1 1207 if (ShowSafepointMsgs) {
duke@1 1208 va_list ap;
duke@1 1209 va_start(ap, format);
duke@1 1210 tty->vprint_cr(format, ap);
duke@1 1211 va_end(ap);
duke@1 1212 }
duke@1 1213 }
duke@1 1214
duke@1 1215 #endif // !PRODUCT