annotate hotspot/src/share/vm/runtime/safepoint.cpp @ 37176:663bdc7d0b86

8149023: Event based tracing should cover safepoint begin and end Summary: Add events to safepoint begin and end Reviewed-by: dholmes, mgronlun, egahlin
author dsimms
date Wed, 23 Mar 2016 10:52:35 +0100
parents e881f320966e
children 91e5f98fff6f
rev   line source
duke@1 1 /*
rprotacio@37043 2 * Copyright (c) 1997, 2016, Oracle and/or its affiliates. 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 *
trims@5547 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@5547 20 * or visit www.oracle.com if you need additional information or have any
trims@5547 21 * questions.
duke@1 22 *
duke@1 23 */
duke@1 24
stefank@7397 25 #include "precompiled.hpp"
gziemski@24426 26 #include "classfile/stringTable.hpp"
mgronlun@34666 27 #include "classfile/symbolTable.hpp"
stefank@7397 28 #include "classfile/systemDictionary.hpp"
stefank@7397 29 #include "code/codeCache.hpp"
stefank@7397 30 #include "code/icBuffer.hpp"
stefank@7397 31 #include "code/nmethod.hpp"
stefank@7397 32 #include "code/pcDesc.hpp"
stefank@7397 33 #include "code/scopeDesc.hpp"
pliden@30764 34 #include "gc/shared/collectedHeap.hpp"
pliden@30764 35 #include "gc/shared/gcLocker.inline.hpp"
stefank@7397 36 #include "interpreter/interpreter.hpp"
rprotacio@33763 37 #include "logging/log.hpp"
stefank@7397 38 #include "memory/resourceArea.hpp"
stefank@7397 39 #include "memory/universe.inline.hpp"
stefank@7397 40 #include "oops/oop.inline.hpp"
coleenp@8076 41 #include "oops/symbol.hpp"
goetz@25351 42 #include "runtime/atomic.inline.hpp"
stefank@7397 43 #include "runtime/compilationPolicy.hpp"
stefank@7397 44 #include "runtime/deoptimization.hpp"
stefank@7397 45 #include "runtime/frame.inline.hpp"
stefank@7397 46 #include "runtime/interfaceSupport.hpp"
stefank@7397 47 #include "runtime/mutexLocker.hpp"
goetz@24351 48 #include "runtime/orderAccess.inline.hpp"
stefank@7397 49 #include "runtime/osThread.hpp"
stefank@7397 50 #include "runtime/safepoint.hpp"
stefank@7397 51 #include "runtime/signature.hpp"
stefank@7397 52 #include "runtime/stubCodeGenerator.hpp"
stefank@7397 53 #include "runtime/stubRoutines.hpp"
stefank@7397 54 #include "runtime/sweeper.hpp"
stefank@7397 55 #include "runtime/synchronizer.hpp"
stefank@14583 56 #include "runtime/thread.inline.hpp"
rehn@37161 57 #include "runtime/timerTrace.hpp"
stefank@7397 58 #include "services/runtimeService.hpp"
dsimms@37176 59 #include "trace/tracing.hpp"
dsimms@37176 60 #include "trace/traceMacros.hpp"
stefank@7397 61 #include "utilities/events.hpp"
jprovino@15482 62 #include "utilities/macros.hpp"
jprovino@15482 63 #if INCLUDE_ALL_GCS
pliden@30764 64 #include "gc/cms/concurrentMarkSweepThread.hpp"
pliden@30764 65 #include "gc/g1/suspendibleThreadSet.hpp"
jprovino@15482 66 #endif // INCLUDE_ALL_GCS
stefank@7397 67 #ifdef COMPILER1
stefank@7397 68 #include "c1/c1_globals.hpp"
stefank@7397 69 #endif
duke@1 70
duke@1 71 // --------------------------------------------------------------------------------------------------
duke@1 72 // Implementation of Safepoint begin/end
duke@1 73
duke@1 74 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
duke@1 75 volatile int SafepointSynchronize::_waiting_to_block = 0;
duke@1 76 volatile int SafepointSynchronize::_safepoint_counter = 0;
never@11631 77 int SafepointSynchronize::_current_jni_active_count = 0;
xlu@5042 78 long SafepointSynchronize::_end_of_last_safepoint = 0;
duke@1 79 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
duke@1 80 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
duke@1 81 static bool timeout_error_printed = false;
duke@1 82
duke@1 83 // Roll all threads forward to a safepoint and suspend them all
duke@1 84 void SafepointSynchronize::begin() {
dsimms@37176 85 EventSafepointBegin begin_event;
duke@1 86 Thread* myThread = Thread::current();
duke@1 87 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
duke@1 88
xlu@5042 89 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@5042 90 _safepoint_begin_time = os::javaTimeNanos();
xlu@5042 91 _ts_of_current_safepoint = tty->time_stamp().seconds();
xlu@5042 92 }
duke@1 93
jprovino@15482 94 #if INCLUDE_ALL_GCS
duke@1 95 if (UseConcMarkSweepGC) {
duke@1 96 // In the future we should investigate whether CMS can use the
duke@1 97 // more-general mechanism below. DLD (01/05).
duke@1 98 ConcurrentMarkSweepThread::synchronize(false);
ysr@3262 99 } else if (UseG1GC) {
pliden@24094 100 SuspendibleThreadSet::synchronize();
duke@1 101 }
jprovino@15482 102 #endif // INCLUDE_ALL_GCS
duke@1 103
duke@1 104 // By getting the Threads_lock, we assure that no threads are about to start or
duke@1 105 // exit. It is released again in SafepointSynchronize::end().
duke@1 106 Threads_lock->lock();
duke@1 107
duke@1 108 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
duke@1 109
duke@1 110 int nof_threads = Threads::number_of_threads();
duke@1 111
rprotacio@33763 112 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
duke@1 113
duke@1 114 RuntimeService::record_safepoint_begin();
duke@1 115
duke@1 116 MutexLocker mu(Safepoint_lock);
duke@1 117
never@11631 118 // Reset the count of active JNI critical threads
never@11631 119 _current_jni_active_count = 0;
never@11631 120
duke@1 121 // Set number of threads to wait for, before we initiate the callbacks
duke@1 122 _waiting_to_block = nof_threads;
duke@1 123 TryingToBlock = 0 ;
duke@1 124 int still_running = nof_threads;
duke@1 125
duke@1 126 // Save the starting time, so that it can be compared to see if this has taken
duke@1 127 // too long to complete.
goetz@33589 128 jlong safepoint_limit_time = 0;
duke@1 129 timeout_error_printed = false;
duke@1 130
xlu@4006 131 // PrintSafepointStatisticsTimeout can be specified separately. When
xlu@4006 132 // specified, PrintSafepointStatistics will be set to true in
xlu@4006 133 // deferred_initialize_stat method. The initialization has to be done
xlu@4006 134 // early enough to avoid any races. See bug 6880029 for details.
xlu@4006 135 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@4006 136 deferred_initialize_stat();
xlu@4006 137 }
xlu@4006 138
duke@1 139 // Begin the process of bringing the system to a safepoint.
duke@1 140 // Java threads can be in several different states and are
duke@1 141 // stopped by different mechanisms:
duke@1 142 //
duke@1 143 // 1. Running interpreted
jwilhelm@22551 144 // The interpreter dispatch table is changed to force it to
duke@1 145 // check for a safepoint condition between bytecodes.
duke@1 146 // 2. Running in native code
duke@1 147 // When returning from the native code, a Java thread must check
duke@1 148 // the safepoint _state to see if we must block. If the
duke@1 149 // VM thread sees a Java thread in native, it does
duke@1 150 // not wait for this thread to block. The order of the memory
duke@1 151 // writes and reads of both the safepoint state and the Java
duke@1 152 // threads state is critical. In order to guarantee that the
duke@1 153 // memory writes are serialized with respect to each other,
duke@1 154 // the VM thread issues a memory barrier instruction
duke@1 155 // (on MP systems). In order to avoid the overhead of issuing
duke@1 156 // a memory barrier for each Java thread making native calls, each Java
duke@1 157 // thread performs a write to a single memory page after changing
duke@1 158 // the thread state. The VM thread performs a sequence of
duke@1 159 // mprotect OS calls which forces all previous writes from all
duke@1 160 // Java threads to be serialized. This is done in the
duke@1 161 // os::serialize_thread_states() call. This has proven to be
duke@1 162 // much more efficient than executing a membar instruction
duke@1 163 // on every call to native code.
duke@1 164 // 3. Running compiled Code
duke@1 165 // Compiled code reads a global (Safepoint Polling) page that
duke@1 166 // is set to fault if we are trying to get to a safepoint.
duke@1 167 // 4. Blocked
duke@1 168 // A thread which is blocked will not be allowed to return from the
duke@1 169 // block condition until the safepoint operation is complete.
duke@1 170 // 5. In VM or Transitioning between states
duke@1 171 // If a Java thread is currently running in the VM or transitioning
duke@1 172 // between states, the safepointing code will wait for the thread to
duke@1 173 // block itself when it attempts transitions to a new state.
duke@1 174 //
dsimms@37176 175 {
dsimms@37176 176 EventSafepointStateSync sync_event;
dsimms@37176 177 int initial_running = 0;
duke@1 178
dsimms@37176 179 _state = _synchronizing;
dsimms@37176 180 OrderAccess::fence();
duke@1 181
dsimms@37176 182 // Flush all thread states to memory
dsimms@37176 183 if (!UseMembar) {
dsimms@37176 184 os::serialize_thread_states();
dsimms@37176 185 }
duke@1 186
dsimms@37176 187 // Make interpreter safepoint aware
dsimms@37176 188 Interpreter::notice_safepoints();
duke@1 189
dsimms@37176 190 if (DeferPollingPageLoopCount < 0) {
dsimms@37176 191 // Make polling safepoint aware
dsimms@37176 192 guarantee (PageArmed == 0, "invariant") ;
dsimms@37176 193 PageArmed = 1 ;
dsimms@37176 194 os::make_polling_page_unreadable();
dsimms@37176 195 }
dsimms@37176 196
dsimms@37176 197 // Consider using active_processor_count() ... but that call is expensive.
dsimms@37176 198 int ncpus = os::processor_count() ;
duke@1 199
duke@1 200 #ifdef ASSERT
dsimms@37176 201 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
dsimms@37176 202 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
dsimms@37176 203 // Clear the visited flag to ensure that the critical counts are collected properly.
dsimms@37176 204 cur->set_visited_for_critical_count(false);
dsimms@37176 205 }
duke@1 206 #endif // ASSERT
duke@1 207
dsimms@37176 208 if (SafepointTimeout)
dsimms@37176 209 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
duke@1 210
dsimms@37176 211 // Iterate through all threads until it have been determined how to stop them all at a safepoint
dsimms@37176 212 unsigned int iterations = 0;
dsimms@37176 213 int steps = 0 ;
dsimms@37176 214 while(still_running > 0) {
dsimms@37176 215 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
dsimms@37176 216 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
dsimms@37176 217 ThreadSafepointState *cur_state = cur->safepoint_state();
dsimms@37176 218 if (cur_state->is_running()) {
dsimms@37176 219 cur_state->examine_state_of_thread();
dsimms@37176 220 if (!cur_state->is_running()) {
dsimms@37176 221 still_running--;
dsimms@37176 222 // consider adjusting steps downward:
dsimms@37176 223 // steps = 0
dsimms@37176 224 // steps -= NNN
dsimms@37176 225 // steps >>= 1
dsimms@37176 226 // steps = MIN(steps, 2000-100)
dsimms@37176 227 // if (iterations != 0) steps -= NNN
dsimms@37176 228 }
dsimms@37176 229 if (log_is_enabled(Trace, safepoint)) {
dsimms@37176 230 ResourceMark rm;
dsimms@37176 231 cur_state->print_on(LogHandle(safepoint)::trace_stream());
dsimms@37176 232 }
duke@1 233 }
dsimms@37176 234 }
dsimms@37176 235
dsimms@37176 236 if (iterations == 0) {
dsimms@37176 237 initial_running = still_running;
dsimms@37176 238 if (PrintSafepointStatistics) {
dsimms@37176 239 begin_statistics(nof_threads, still_running);
dsimms@37176 240 }
dsimms@37176 241 }
dsimms@37176 242
dsimms@37176 243 if (still_running > 0) {
dsimms@37176 244 // Check for if it takes to long
dsimms@37176 245 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
dsimms@37176 246 print_safepoint_timeout(_spinning_timeout);
dsimms@37176 247 }
dsimms@37176 248
dsimms@37176 249 // Spin to avoid context switching.
dsimms@37176 250 // There's a tension between allowing the mutators to run (and rendezvous)
dsimms@37176 251 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
dsimms@37176 252 // a mutator might otherwise use profitably to reach a safepoint. Excessive
dsimms@37176 253 // spinning by the VM thread on a saturated system can increase rendezvous latency.
dsimms@37176 254 // Blocking or yielding incur their own penalties in the form of context switching
dsimms@37176 255 // and the resultant loss of $ residency.
dsimms@37176 256 //
dsimms@37176 257 // Further complicating matters is that yield() does not work as naively expected
dsimms@37176 258 // on many platforms -- yield() does not guarantee that any other ready threads
dsimms@37176 259 // will run. As such we revert to naked_short_sleep() after some number of iterations.
dsimms@37176 260 // nakes_short_sleep() is implemented as a short unconditional sleep.
dsimms@37176 261 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
dsimms@37176 262 // can actually increase the time it takes the VM thread to detect that a system-wide
dsimms@37176 263 // stop-the-world safepoint has been reached. In a pathological scenario such as that
dsimms@37176 264 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
dsimms@37176 265 // In that case the mutators will be stalled waiting for the safepoint to complete and the
dsimms@37176 266 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
dsimms@37176 267 // will eventually wake up and detect that all mutators are safe, at which point
dsimms@37176 268 // we'll again make progress.
dsimms@37176 269 //
dsimms@37176 270 // Beware too that that the VMThread typically runs at elevated priority.
dsimms@37176 271 // Its default priority is higher than the default mutator priority.
dsimms@37176 272 // Obviously, this complicates spinning.
dsimms@37176 273 //
dsimms@37176 274 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
dsimms@37176 275 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
dsimms@37176 276 //
dsimms@37176 277 // See the comments in synchronizer.cpp for additional remarks on spinning.
dsimms@37176 278 //
dsimms@37176 279 // In the future we might:
dsimms@37176 280 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
dsimms@37176 281 // This is tricky as the path used by a thread exiting the JVM (say on
dsimms@37176 282 // on JNI call-out) simply stores into its state field. The burden
dsimms@37176 283 // is placed on the VM thread, which must poll (spin).
dsimms@37176 284 // 2. Find something useful to do while spinning. If the safepoint is GC-related
dsimms@37176 285 // we might aggressively scan the stacks of threads that are already safe.
dsimms@37176 286 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
dsimms@37176 287 // If all the mutators are ONPROC there's no reason to sleep or yield.
dsimms@37176 288 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
dsimms@37176 289 // 5. Check system saturation. If the system is not fully saturated then
dsimms@37176 290 // simply spin and avoid sleep/yield.
dsimms@37176 291 // 6. As still-running mutators rendezvous they could unpark the sleeping
dsimms@37176 292 // VMthread. This works well for still-running mutators that become
dsimms@37176 293 // safe. The VMthread must still poll for mutators that call-out.
dsimms@37176 294 // 7. Drive the policy on time-since-begin instead of iterations.
dsimms@37176 295 // 8. Consider making the spin duration a function of the # of CPUs:
dsimms@37176 296 // Spin = (((ncpus-1) * M) + K) + F(still_running)
dsimms@37176 297 // Alternately, instead of counting iterations of the outer loop
dsimms@37176 298 // we could count the # of threads visited in the inner loop, above.
dsimms@37176 299 // 9. On windows consider using the return value from SwitchThreadTo()
dsimms@37176 300 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
dsimms@37176 301
dsimms@37176 302 if (int(iterations) == DeferPollingPageLoopCount) {
dsimms@37176 303 guarantee (PageArmed == 0, "invariant") ;
dsimms@37176 304 PageArmed = 1 ;
dsimms@37176 305 os::make_polling_page_unreadable();
dsimms@37176 306 }
dsimms@37176 307
dsimms@37176 308 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
dsimms@37176 309 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
dsimms@37176 310 ++steps ;
dsimms@37176 311 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
dsimms@37176 312 SpinPause() ; // MP-Polite spin
dsimms@37176 313 } else
dsimms@37176 314 if (steps < DeferThrSuspendLoopCount) {
dsimms@37176 315 os::naked_yield() ;
dsimms@37176 316 } else {
dsimms@37176 317 os::naked_short_sleep(1);
dsimms@37176 318 }
dsimms@37176 319
dsimms@37176 320 iterations ++ ;
dsimms@37176 321 }
dsimms@37176 322 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
dsimms@37176 323 }
dsimms@37176 324 assert(still_running == 0, "sanity check");
dsimms@37176 325
dsimms@37176 326 if (PrintSafepointStatistics) {
dsimms@37176 327 update_statistics_on_spin_end();
dsimms@37176 328 }
dsimms@37176 329
dsimms@37176 330 if (sync_event.should_commit()) {
dsimms@37176 331 sync_event.set_safepointId(safepoint_counter());
dsimms@37176 332 sync_event.set_initialThreadCount(initial_running);
dsimms@37176 333 sync_event.set_runningThreadCount(_waiting_to_block);
dsimms@37176 334 sync_event.set_iterations(iterations);
dsimms@37176 335 sync_event.commit();
dsimms@37176 336 }
dsimms@37176 337 } //EventSafepointStateSync
dsimms@37176 338
dsimms@37176 339 // wait until all threads are stopped
dsimms@37176 340 {
dsimms@37176 341 EventSafepointWaitBlocked wait_blocked_event;
dsimms@37176 342 int initial_waiting_to_block = _waiting_to_block;
dsimms@37176 343
dsimms@37176 344 while (_waiting_to_block > 0) {
dsimms@37176 345 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
dsimms@37176 346 if (!SafepointTimeout || timeout_error_printed) {
dsimms@37176 347 Safepoint_lock->wait(true); // true, means with no safepoint checks
dsimms@37176 348 } else {
dsimms@37176 349 // Compute remaining time
dsimms@37176 350 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
dsimms@37176 351
dsimms@37176 352 // If there is no remaining time, then there is an error
dsimms@37176 353 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
dsimms@37176 354 print_safepoint_timeout(_blocking_timeout);
rprotacio@33763 355 }
duke@1 356 }
duke@1 357 }
dsimms@37176 358 assert(_waiting_to_block == 0, "sanity check");
duke@1 359
dsimms@37176 360 #ifndef PRODUCT
dsimms@37176 361 if (SafepointTimeout) {
dsimms@37176 362 jlong current_time = os::javaTimeNanos();
dsimms@37176 363 if (safepoint_limit_time < current_time) {
dsimms@37176 364 tty->print_cr("# SafepointSynchronize: Finished after "
dsimms@37176 365 INT64_FORMAT_W(6) " ms",
dsimms@37176 366 ((current_time - safepoint_limit_time) / MICROUNITS +
dsimms@37176 367 (jlong)SafepointTimeoutDelay));
duke@1 368 }
duke@1 369 }
duke@1 370 #endif
duke@1 371
dsimms@37176 372 assert((_safepoint_counter & 0x1) == 0, "must be even");
dsimms@37176 373 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
dsimms@37176 374 _safepoint_counter ++;
duke@1 375
dsimms@37176 376 // Record state
dsimms@37176 377 _state = _synchronized;
duke@1 378
dsimms@37176 379 OrderAccess::fence();
dsimms@37176 380
dsimms@37176 381 if (wait_blocked_event.should_commit()) {
dsimms@37176 382 wait_blocked_event.set_safepointId(safepoint_counter());
dsimms@37176 383 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
dsimms@37176 384 wait_blocked_event.commit();
dsimms@37176 385 }
dsimms@37176 386 } // EventSafepointWaitBlocked
duke@1 387
never@12108 388 #ifdef ASSERT
never@12108 389 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
never@12108 390 // make sure all the threads were visited
never@12108 391 assert(cur->was_visited_for_critical_count(), "missed a thread");
never@12108 392 }
never@12108 393 #endif // ASSERT
never@12108 394
never@11631 395 // Update the count of active JNI critical regions
david@35492 396 GCLocker::set_jni_lock_count(_current_jni_active_count);
never@11631 397
rprotacio@33763 398 if (log_is_enabled(Debug, safepoint)) {
duke@1 399 VM_Operation *op = VMThread::vm_operation();
rprotacio@33763 400 log_debug(safepoint)("Entering safepoint region: %s",
rprotacio@33763 401 (op != NULL) ? op->name() : "no vm operation");
duke@1 402 }
duke@1 403
duke@1 404 RuntimeService::record_safepoint_synchronized();
duke@1 405 if (PrintSafepointStatistics) {
duke@1 406 update_statistics_on_sync_end(os::javaTimeNanos());
duke@1 407 }
duke@1 408
duke@1 409 // Call stuff that needs to be run when a safepoint is just about to be completed
dsimms@37176 410 {
dsimms@37176 411 EventSafepointCleanup cleanup_event;
dsimms@37176 412 do_cleanup_tasks();
dsimms@37176 413 if (cleanup_event.should_commit()) {
dsimms@37176 414 cleanup_event.set_safepointId(safepoint_counter());
dsimms@37176 415 cleanup_event.commit();
dsimms@37176 416 }
dsimms@37176 417 }
xlu@5042 418
xlu@5042 419 if (PrintSafepointStatistics) {
xlu@5042 420 // Record how much time spend on the above cleanup tasks
xlu@5042 421 update_statistics_on_cleanup_end(os::javaTimeNanos());
xlu@5042 422 }
dsimms@37176 423 if (begin_event.should_commit()) {
dsimms@37176 424 begin_event.set_safepointId(safepoint_counter());
dsimms@37176 425 begin_event.set_totalThreadCount(nof_threads);
dsimms@37176 426 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
dsimms@37176 427 begin_event.commit();
dsimms@37176 428 }
duke@1 429 }
duke@1 430
duke@1 431 // Wake up all threads, so they are ready to resume execution after the safepoint
duke@1 432 // operation has been carried out
duke@1 433 void SafepointSynchronize::end() {
dsimms@37176 434 EventSafepointEnd event;
dsimms@37176 435 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
duke@1 436
duke@1 437 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 438 assert((_safepoint_counter & 0x1) == 1, "must be odd");
duke@1 439 _safepoint_counter ++;
duke@1 440 // memory fence isn't required here since an odd _safepoint_counter
duke@1 441 // value can do no harm and a fence is issued below anyway.
duke@1 442
duke@1 443 DEBUG_ONLY(Thread* myThread = Thread::current();)
duke@1 444 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
duke@1 445
duke@1 446 if (PrintSafepointStatistics) {
duke@1 447 end_statistics(os::javaTimeNanos());
duke@1 448 }
duke@1 449
duke@1 450 #ifdef ASSERT
duke@1 451 // A pending_exception cannot be installed during a safepoint. The threads
duke@1 452 // may install an async exception after they come back from a safepoint into
duke@1 453 // pending_exception after they unblock. But that should happen later.
duke@1 454 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 455 assert (!(cur->has_pending_exception() &&
duke@1 456 cur->safepoint_state()->is_at_poll_safepoint()),
duke@1 457 "safepoint installed a pending exception");
duke@1 458 }
duke@1 459 #endif // ASSERT
duke@1 460
duke@1 461 if (PageArmed) {
duke@1 462 // Make polling safepoint aware
duke@1 463 os::make_polling_page_readable();
duke@1 464 PageArmed = 0 ;
duke@1 465 }
duke@1 466
duke@1 467 // Remove safepoint check from interpreter
duke@1 468 Interpreter::ignore_safepoints();
duke@1 469
duke@1 470 {
duke@1 471 MutexLocker mu(Safepoint_lock);
duke@1 472
duke@1 473 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
duke@1 474
duke@1 475 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
duke@1 476 // when they get restarted.
duke@1 477 _state = _not_synchronized;
duke@1 478 OrderAccess::fence();
duke@1 479
rprotacio@33763 480 log_debug(safepoint)("Leaving safepoint region");
duke@1 481
duke@1 482 // Start suspended threads
duke@1 483 for(JavaThread *current = Threads::first(); current; current = current->next()) {
twisti@2131 484 // A problem occurring on Solaris is when attempting to restart threads
duke@1 485 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
duke@1 486 // to the next one (since it has been running the longest). We then have
duke@1 487 // to wait for a cpu to become available before we can continue restarting
duke@1 488 // threads.
duke@1 489 // FIXME: This causes the performance of the VM to degrade when active and with
duke@1 490 // large numbers of threads. Apparently this is due to the synchronous nature
duke@1 491 // of suspending threads.
duke@1 492 //
duke@1 493 // TODO-FIXME: the comments above are vestigial and no longer apply.
duke@1 494 // Furthermore, using solaris' schedctl in this particular context confers no benefit
duke@1 495 if (VMThreadHintNoPreempt) {
duke@1 496 os::hint_no_preempt();
duke@1 497 }
duke@1 498 ThreadSafepointState* cur_state = current->safepoint_state();
duke@1 499 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
duke@1 500 cur_state->restart();
duke@1 501 assert(cur_state->is_running(), "safepoint state has not been reset");
duke@1 502 }
duke@1 503
duke@1 504 RuntimeService::record_safepoint_end();
duke@1 505
duke@1 506 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
duke@1 507 // blocked in signal_thread_blocked
duke@1 508 Threads_lock->unlock();
duke@1 509
duke@1 510 }
jprovino@15482 511 #if INCLUDE_ALL_GCS
duke@1 512 // If there are any concurrent GC threads resume them.
duke@1 513 if (UseConcMarkSweepGC) {
duke@1 514 ConcurrentMarkSweepThread::desynchronize(false);
ysr@3262 515 } else if (UseG1GC) {
pliden@24094 516 SuspendibleThreadSet::desynchronize();
duke@1 517 }
jprovino@15482 518 #endif // INCLUDE_ALL_GCS
jwilhelm@22551 519 // record this time so VMThread can keep track how much time has elapsed
xlu@5042 520 // since last safepoint.
xlu@5042 521 _end_of_last_safepoint = os::javaTimeMillis();
dsimms@37176 522
dsimms@37176 523 if (event.should_commit()) {
dsimms@37176 524 event.set_safepointId(safepoint_id);
dsimms@37176 525 event.commit();
dsimms@37176 526 }
duke@1 527 }
duke@1 528
duke@1 529 bool SafepointSynchronize::is_cleanup_needed() {
duke@1 530 // Need a safepoint if some inline cache buffers is non-empty
duke@1 531 if (!InlineCacheBuffer::is_empty()) return true;
duke@1 532 return false;
duke@1 533 }
duke@1 534
dsimms@37176 535 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
dsimms@37176 536 if (event.should_commit()) {
dsimms@37176 537 event.set_safepointId(SafepointSynchronize::safepoint_counter());
dsimms@37176 538 event.set_name(name);
dsimms@37176 539 event.commit();
dsimms@37176 540 }
dsimms@37176 541 }
duke@1 542
duke@1 543 // Various cleaning tasks that should be done periodically at safepoints
duke@1 544 void SafepointSynchronize::do_cleanup_tasks() {
xlu@5042 545 {
dsimms@37176 546 const char* name = "deflating idle monitors";
dsimms@37176 547 EventSafepointCleanupTask event;
dsimms@37176 548 TraceTime timer(name, TRACETIME_LOG(Info, safepointcleanup));
xlu@5042 549 ObjectSynchronizer::deflate_idle_monitors();
dsimms@37176 550 event_safepoint_cleanup_task_commit(event, name);
duke@1 551 }
duke@1 552
xlu@5042 553 {
dsimms@37176 554 const char* name = "updating inline caches";
dsimms@37176 555 EventSafepointCleanupTask event;
dsimms@37176 556 TraceTime timer(name, TRACETIME_LOG(Info, safepointcleanup));
xlu@5042 557 InlineCacheBuffer::update_inline_caches();
dsimms@37176 558 event_safepoint_cleanup_task_commit(event, name);
xlu@5042 559 }
iveresov@6453 560 {
dsimms@37176 561 const char* name = "compilation policy safepoint handler";
dsimms@37176 562 EventSafepointCleanupTask event;
rehn@37161 563 TraceTime timer("compilation policy safepoint handler", TRACETIME_LOG(Info, safepointcleanup));
iveresov@6453 564 CompilationPolicy::policy()->do_safepoint_work();
dsimms@37176 565 event_safepoint_cleanup_task_commit(event, name);
duke@1 566 }
xlu@5042 567
coleenp@13087 568 {
dsimms@37176 569 const char* name = "mark nmethods";
dsimms@37176 570 EventSafepointCleanupTask event;
dsimms@37176 571 TraceTime timer(name, TRACETIME_LOG(Info, safepointcleanup));
anoll@20290 572 NMethodSweeper::mark_active_nmethods();
dsimms@37176 573 event_safepoint_cleanup_task_commit(event, name);
coleenp@13087 574 }
coleenp@13087 575
coleenp@13087 576 if (SymbolTable::needs_rehashing()) {
dsimms@37176 577 const char* name = "rehashing symbol table";
dsimms@37176 578 EventSafepointCleanupTask event;
dsimms@37176 579 TraceTime timer(name, TRACETIME_LOG(Info, safepointcleanup));
coleenp@13087 580 SymbolTable::rehash_table();
dsimms@37176 581 event_safepoint_cleanup_task_commit(event, name);
coleenp@13087 582 }
coleenp@13087 583
coleenp@13087 584 if (StringTable::needs_rehashing()) {
dsimms@37176 585 const char* name = "rehashing string table";
dsimms@37176 586 EventSafepointCleanupTask event;
dsimms@37176 587 TraceTime timer(name, TRACETIME_LOG(Info, safepointcleanup));
coleenp@13087 588 StringTable::rehash_table();
dsimms@37176 589 event_safepoint_cleanup_task_commit(event, name);
coleenp@13087 590 }
minqi@9990 591
coleenp@24457 592 {
coleenp@24457 593 // CMS delays purging the CLDG until the beginning of the next safepoint and to
coleenp@24457 594 // make sure concurrent sweep is done
dsimms@37176 595 const char* name = "purging class loader data graph";
dsimms@37176 596 EventSafepointCleanupTask event;
dsimms@37176 597 TraceTime timer(name, TRACETIME_LOG(Info, safepointcleanup));
coleenp@24457 598 ClassLoaderDataGraph::purge_if_needed();
dsimms@37176 599 event_safepoint_cleanup_task_commit(event, name);
coleenp@24457 600 }
duke@1 601 }
duke@1 602
duke@1 603
duke@1 604 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
duke@1 605 switch(state) {
duke@1 606 case _thread_in_native:
duke@1 607 // native threads are safe if they have no java stack or have walkable stack
duke@1 608 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
duke@1 609
duke@1 610 // blocked threads should have already have walkable stack
duke@1 611 case _thread_blocked:
duke@1 612 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
duke@1 613 return true;
duke@1 614
duke@1 615 default:
duke@1 616 return false;
duke@1 617 }
duke@1 618 }
duke@1 619
duke@1 620
never@11637 621 // See if the thread is running inside a lazy critical native and
never@11637 622 // update the thread critical count if so. Also set a suspend flag to
never@11637 623 // cause the native wrapper to return into the JVM to do the unlock
never@11637 624 // once the native finishes.
never@11637 625 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
never@11637 626 if (state == _thread_in_native &&
never@11637 627 thread->has_last_Java_frame() &&
never@11637 628 thread->frame_anchor()->walkable()) {
never@11637 629 // This thread might be in a critical native nmethod so look at
never@11637 630 // the top of the stack and increment the critical count if it
never@11637 631 // is.
never@11637 632 frame wrapper_frame = thread->last_frame();
never@11637 633 CodeBlob* stub_cb = wrapper_frame.cb();
never@11637 634 if (stub_cb != NULL &&
never@11637 635 stub_cb->is_nmethod() &&
never@11637 636 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
never@11637 637 // A thread could potentially be in a critical native across
never@11637 638 // more than one safepoint, so only update the critical state on
never@11637 639 // the first one. When it returns it will perform the unlock.
never@11637 640 if (!thread->do_critical_native_unlock()) {
never@11637 641 #ifdef ASSERT
never@11637 642 if (!thread->in_critical()) {
david@35492 643 GCLocker::increment_debug_jni_lock_count();
never@11637 644 }
never@11637 645 #endif
never@11637 646 thread->enter_critical();
never@11637 647 // Make sure the native wrapper calls back on return to
never@11637 648 // perform the needed critical unlock.
never@11637 649 thread->set_critical_native_unlock();
never@11637 650 }
never@11637 651 }
never@11637 652 }
never@11637 653 }
never@11637 654
never@11637 655
never@11637 656
duke@1 657 // -------------------------------------------------------------------------------------------------------
duke@1 658 // Implementation of Safepoint callback point
duke@1 659
duke@1 660 void SafepointSynchronize::block(JavaThread *thread) {
duke@1 661 assert(thread != NULL, "thread must be set");
duke@1 662 assert(thread->is_Java_thread(), "not a Java thread");
duke@1 663
duke@1 664 // Threads shouldn't block if they are in the middle of printing, but...
duke@1 665 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
duke@1 666
duke@1 667 // Only bail from the block() call if the thread is gone from the
duke@1 668 // thread list; starting to exit should still block.
duke@1 669 if (thread->is_terminated()) {
duke@1 670 // block current thread if we come here from native code when VM is gone
duke@1 671 thread->block_if_vm_exited();
duke@1 672
duke@1 673 // otherwise do nothing
duke@1 674 return;
duke@1 675 }
duke@1 676
duke@1 677 JavaThreadState state = thread->thread_state();
duke@1 678 thread->frame_anchor()->make_walkable(thread);
duke@1 679
duke@1 680 // Check that we have a valid thread_state at this point
duke@1 681 switch(state) {
duke@1 682 case _thread_in_vm_trans:
duke@1 683 case _thread_in_Java: // From compiled code
duke@1 684
duke@1 685 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
duke@1 686 // we pretend we are still in the VM.
duke@1 687 thread->set_thread_state(_thread_in_vm);
duke@1 688
duke@1 689 if (is_synchronizing()) {
duke@1 690 Atomic::inc (&TryingToBlock) ;
duke@1 691 }
duke@1 692
duke@1 693 // We will always be holding the Safepoint_lock when we are examine the state
duke@1 694 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
duke@1 695 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
duke@1 696 Safepoint_lock->lock_without_safepoint_check();
duke@1 697 if (is_synchronizing()) {
duke@1 698 // Decrement the number of threads to wait for and signal vm thread
duke@1 699 assert(_waiting_to_block > 0, "sanity check");
duke@1 700 _waiting_to_block--;
duke@1 701 thread->safepoint_state()->set_has_called_back(true);
duke@1 702
never@12108 703 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
never@11631 704 if (thread->in_critical()) {
never@11631 705 // Notice that this thread is in a critical section
never@11631 706 increment_jni_active_count();
never@11631 707 }
never@11631 708
duke@1 709 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
duke@1 710 if (_waiting_to_block == 0) {
duke@1 711 Safepoint_lock->notify_all();
duke@1 712 }
duke@1 713 }
duke@1 714
duke@1 715 // We transition the thread to state _thread_blocked here, but
duke@1 716 // we can't do our usual check for external suspension and then
duke@1 717 // self-suspend after the lock_without_safepoint_check() call
duke@1 718 // below because we are often called during transitions while
duke@1 719 // we hold different locks. That would leave us suspended while
duke@1 720 // holding a resource which results in deadlocks.
duke@1 721 thread->set_thread_state(_thread_blocked);
duke@1 722 Safepoint_lock->unlock();
duke@1 723
duke@1 724 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
duke@1 725 // the entire safepoint, the threads will all line up here during the safepoint.
duke@1 726 Threads_lock->lock_without_safepoint_check();
duke@1 727 // restore original state. This is important if the thread comes from compiled code, so it
duke@1 728 // will continue to execute with the _thread_in_Java state.
duke@1 729 thread->set_thread_state(state);
duke@1 730 Threads_lock->unlock();
duke@1 731 break;
duke@1 732
duke@1 733 case _thread_in_native_trans:
duke@1 734 case _thread_blocked_trans:
duke@1 735 case _thread_new_trans:
duke@1 736 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
duke@1 737 thread->print_thread_state();
duke@1 738 fatal("Deadlock in safepoint code. "
duke@1 739 "Should have called back to the VM before blocking.");
duke@1 740 }
duke@1 741
duke@1 742 // We transition the thread to state _thread_blocked here, but
duke@1 743 // we can't do our usual check for external suspension and then
duke@1 744 // self-suspend after the lock_without_safepoint_check() call
duke@1 745 // below because we are often called during transitions while
duke@1 746 // we hold different locks. That would leave us suspended while
duke@1 747 // holding a resource which results in deadlocks.
duke@1 748 thread->set_thread_state(_thread_blocked);
duke@1 749
duke@1 750 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
duke@1 751 // the safepoint code might still be waiting for it to block. We need to change the state here,
duke@1 752 // so it can see that it is at a safepoint.
duke@1 753
duke@1 754 // Block until the safepoint operation is completed.
duke@1 755 Threads_lock->lock_without_safepoint_check();
duke@1 756
duke@1 757 // Restore state
duke@1 758 thread->set_thread_state(state);
duke@1 759
duke@1 760 Threads_lock->unlock();
duke@1 761 break;
duke@1 762
duke@1 763 default:
david@33105 764 fatal("Illegal threadstate encountered: %d", state);
duke@1 765 }
duke@1 766
duke@1 767 // Check for pending. async. exceptions or suspends - except if the
duke@1 768 // thread was blocked inside the VM. has_special_runtime_exit_condition()
duke@1 769 // is called last since it grabs a lock and we only want to do that when
duke@1 770 // we must.
duke@1 771 //
duke@1 772 // Note: we never deliver an async exception at a polling point as the
duke@1 773 // compiler may not have an exception handler for it. The polling
duke@1 774 // code will notice the async and deoptimize and the exception will
duke@1 775 // be delivered. (Polling at a return point is ok though). Sure is
duke@1 776 // a lot of bother for a deprecated feature...
duke@1 777 //
duke@1 778 // We don't deliver an async exception if the thread state is
duke@1 779 // _thread_in_native_trans so JNI functions won't be called with
duke@1 780 // a surprising pending exception. If the thread state is going back to java,
duke@1 781 // async exception is checked in check_special_condition_for_native_trans().
duke@1 782
duke@1 783 if (state != _thread_blocked_trans &&
duke@1 784 state != _thread_in_vm_trans &&
duke@1 785 thread->has_special_runtime_exit_condition()) {
duke@1 786 thread->handle_special_runtime_exit_condition(
duke@1 787 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
duke@1 788 }
duke@1 789 }
duke@1 790
duke@1 791 // ------------------------------------------------------------------------------------------------------
duke@1 792 // Exception handlers
duke@1 793
duke@1 794
duke@1 795 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
duke@1 796 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
duke@1 797 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
duke@1 798 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
duke@1 799
duke@1 800 if (ShowSafepointMsgs) {
duke@1 801 tty->print("handle_polling_page_exception: ");
duke@1 802 }
duke@1 803
duke@1 804 if (PrintSafepointStatistics) {
duke@1 805 inc_page_trap_count();
duke@1 806 }
duke@1 807
duke@1 808 ThreadSafepointState* state = thread->safepoint_state();
duke@1 809
duke@1 810 state->handle_polling_page_exception();
duke@1 811 }
duke@1 812
duke@1 813
duke@1 814 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
duke@1 815 if (!timeout_error_printed) {
duke@1 816 timeout_error_printed = true;
jwilhelm@22551 817 // Print out the thread info which didn't reach the safepoint for debugging
duke@1 818 // purposes (useful when there are lots of threads in the debugger).
drchase@24424 819 tty->cr();
duke@1 820 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
duke@1 821 if (reason == _spinning_timeout) {
duke@1 822 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
duke@1 823 } else if (reason == _blocking_timeout) {
duke@1 824 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
duke@1 825 }
duke@1 826
duke@1 827 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
duke@1 828 ThreadSafepointState *cur_state;
duke@1 829 ResourceMark rm;
duke@1 830 for(JavaThread *cur_thread = Threads::first(); cur_thread;
duke@1 831 cur_thread = cur_thread->next()) {
duke@1 832 cur_state = cur_thread->safepoint_state();
duke@1 833
duke@1 834 if (cur_thread->thread_state() != _thread_blocked &&
duke@1 835 ((reason == _spinning_timeout && cur_state->is_running()) ||
duke@1 836 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
duke@1 837 tty->print("# ");
duke@1 838 cur_thread->print();
drchase@24424 839 tty->cr();
duke@1 840 }
duke@1 841 }
duke@1 842 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
duke@1 843 }
duke@1 844
duke@1 845 // To debug the long safepoint, specify both DieOnSafepointTimeout &
duke@1 846 // ShowMessageBoxOnError.
duke@1 847 if (DieOnSafepointTimeout) {
duke@1 848 VM_Operation *op = VMThread::vm_operation();
david@33105 849 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
david@33105 850 SafepointTimeoutDelay,
david@33105 851 op != NULL ? op->name() : "no vm operation");
duke@1 852 }
duke@1 853 }
duke@1 854
duke@1 855
duke@1 856 // -------------------------------------------------------------------------------------------------------
duke@1 857 // Implementation of ThreadSafepointState
duke@1 858
duke@1 859 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
duke@1 860 _thread = thread;
duke@1 861 _type = _running;
duke@1 862 _has_called_back = false;
duke@1 863 _at_poll_safepoint = false;
duke@1 864 }
duke@1 865
duke@1 866 void ThreadSafepointState::create(JavaThread *thread) {
duke@1 867 ThreadSafepointState *state = new ThreadSafepointState(thread);
duke@1 868 thread->set_safepoint_state(state);
duke@1 869 }
duke@1 870
duke@1 871 void ThreadSafepointState::destroy(JavaThread *thread) {
duke@1 872 if (thread->safepoint_state()) {
duke@1 873 delete(thread->safepoint_state());
duke@1 874 thread->set_safepoint_state(NULL);
duke@1 875 }
duke@1 876 }
duke@1 877
duke@1 878 void ThreadSafepointState::examine_state_of_thread() {
duke@1 879 assert(is_running(), "better be running or just have hit safepoint poll");
duke@1 880
duke@1 881 JavaThreadState state = _thread->thread_state();
duke@1 882
never@6269 883 // Save the state at the start of safepoint processing.
never@6269 884 _orig_thread_state = state;
never@6269 885
duke@1 886 // Check for a thread that is suspended. Note that thread resume tries
duke@1 887 // to grab the Threads_lock which we own here, so a thread cannot be
duke@1 888 // resumed during safepoint synchronization.
duke@1 889
dcubed@3826 890 // We check to see if this thread is suspended without locking to
dcubed@3826 891 // avoid deadlocking with a third thread that is waiting for this
dcubed@3826 892 // thread to be suspended. The third thread can notice the safepoint
dcubed@3826 893 // that we're trying to start at the beginning of its SR_lock->wait()
dcubed@3826 894 // call. If that happens, then the third thread will block on the
dcubed@3826 895 // safepoint while still holding the underlying SR_lock. We won't be
dcubed@3826 896 // able to get the SR_lock and we'll deadlock.
dcubed@3826 897 //
dcubed@3826 898 // We don't need to grab the SR_lock here for two reasons:
dcubed@3826 899 // 1) The suspend flags are both volatile and are set with an
dcubed@3826 900 // Atomic::cmpxchg() call so we should see the suspended
dcubed@3826 901 // state right away.
dcubed@3826 902 // 2) We're being called from the safepoint polling loop; if
dcubed@3826 903 // we don't see the suspended state on this iteration, then
dcubed@3826 904 // we'll come around again.
dcubed@3826 905 //
dcubed@3826 906 bool is_suspended = _thread->is_ext_suspended();
duke@1 907 if (is_suspended) {
duke@1 908 roll_forward(_at_safepoint);
duke@1 909 return;
duke@1 910 }
duke@1 911
duke@1 912 // Some JavaThread states have an initial safepoint state of
duke@1 913 // running, but are actually at a safepoint. We will happily
duke@1 914 // agree and update the safepoint state here.
duke@1 915 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
never@12108 916 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
never@11631 917 roll_forward(_at_safepoint);
never@11631 918 return;
duke@1 919 }
duke@1 920
duke@1 921 if (state == _thread_in_vm) {
duke@1 922 roll_forward(_call_back);
duke@1 923 return;
duke@1 924 }
duke@1 925
duke@1 926 // All other thread states will continue to run until they
duke@1 927 // transition and self-block in state _blocked
duke@1 928 // Safepoint polling in compiled code causes the Java threads to do the same.
duke@1 929 // Note: new threads may require a malloc so they must be allowed to finish
duke@1 930
duke@1 931 assert(is_running(), "examine_state_of_thread on non-running thread");
duke@1 932 return;
duke@1 933 }
duke@1 934
duke@1 935 // Returns true is thread could not be rolled forward at present position.
duke@1 936 void ThreadSafepointState::roll_forward(suspend_type type) {
duke@1 937 _type = type;
duke@1 938
duke@1 939 switch(_type) {
duke@1 940 case _at_safepoint:
duke@1 941 SafepointSynchronize::signal_thread_at_safepoint();
never@12108 942 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
never@12108 943 if (_thread->in_critical()) {
never@12108 944 // Notice that this thread is in a critical section
never@12108 945 SafepointSynchronize::increment_jni_active_count();
never@12108 946 }
duke@1 947 break;
duke@1 948
duke@1 949 case _call_back:
duke@1 950 set_has_called_back(false);
duke@1 951 break;
duke@1 952
duke@1 953 case _running:
duke@1 954 default:
duke@1 955 ShouldNotReachHere();
duke@1 956 }
duke@1 957 }
duke@1 958
duke@1 959 void ThreadSafepointState::restart() {
duke@1 960 switch(type()) {
duke@1 961 case _at_safepoint:
duke@1 962 case _call_back:
duke@1 963 break;
duke@1 964
duke@1 965 case _running:
duke@1 966 default:
bpittore@31592 967 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
david@33148 968 p2i(_thread), _type);
duke@1 969 _thread->print();
duke@1 970 ShouldNotReachHere();
duke@1 971 }
duke@1 972 _type = _running;
duke@1 973 set_has_called_back(false);
duke@1 974 }
duke@1 975
duke@1 976
duke@1 977 void ThreadSafepointState::print_on(outputStream *st) const {
goetz@33589 978 const char *s = NULL;
duke@1 979
duke@1 980 switch(_type) {
duke@1 981 case _running : s = "_running"; break;
duke@1 982 case _at_safepoint : s = "_at_safepoint"; break;
duke@1 983 case _call_back : s = "_call_back"; break;
duke@1 984 default:
duke@1 985 ShouldNotReachHere();
duke@1 986 }
duke@1 987
duke@1 988 st->print_cr("Thread: " INTPTR_FORMAT
duke@1 989 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
david@33148 990 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
duke@1 991 _at_poll_safepoint);
duke@1 992
duke@1 993 _thread->print_thread_state_on(st);
duke@1 994 }
duke@1 995
duke@1 996 // ---------------------------------------------------------------------------------------------------------------------
duke@1 997
duke@1 998 // Block the thread at the safepoint poll or poll return.
duke@1 999 void ThreadSafepointState::handle_polling_page_exception() {
duke@1 1000
duke@1 1001 // Check state. block() will set thread state to thread_in_vm which will
duke@1 1002 // cause the safepoint state _type to become _call_back.
duke@1 1003 assert(type() == ThreadSafepointState::_running,
duke@1 1004 "polling page exception on thread not running state");
duke@1 1005
duke@1 1006 // Step 1: Find the nmethod from the return address
duke@1 1007 if (ShowSafepointMsgs && Verbose) {
david@33148 1008 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
duke@1 1009 }
duke@1 1010 address real_return_addr = thread()->saved_exception_pc();
duke@1 1011
duke@1 1012 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
duke@1 1013 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod");
duke@1 1014 nmethod* nm = (nmethod*)cb;
duke@1 1015
duke@1 1016 // Find frame of caller
duke@1 1017 frame stub_fr = thread()->last_frame();
duke@1 1018 CodeBlob* stub_cb = stub_fr.cb();
duke@1 1019 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
duke@1 1020 RegisterMap map(thread(), true);
duke@1 1021 frame caller_fr = stub_fr.sender(&map);
duke@1 1022
duke@1 1023 // Should only be poll_return or poll
duke@1 1024 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
duke@1 1025
duke@1 1026 // This is a poll immediately before a return. The exception handling code
duke@1 1027 // has already had the effect of causing the return to occur, so the execution
duke@1 1028 // will continue immediately after the call. In addition, the oopmap at the
duke@1 1029 // return point does not mark the return value as an oop (if it is), so
duke@1 1030 // it needs a handle here to be updated.
duke@1 1031 if( nm->is_at_poll_return(real_return_addr) ) {
duke@1 1032 // See if return type is an oop.
duke@1 1033 bool return_oop = nm->method()->is_returning_oop();
duke@1 1034 Handle return_value;
duke@1 1035 if (return_oop) {
duke@1 1036 // The oop result has been saved on the stack together with all
duke@1 1037 // the other registers. In order to preserve it over GCs we need
duke@1 1038 // to keep it in a handle.
duke@1 1039 oop result = caller_fr.saved_oop_result(&map);
duke@1 1040 assert(result == NULL || result->is_oop(), "must be oop");
duke@1 1041 return_value = Handle(thread(), result);
duke@1 1042 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
duke@1 1043 }
duke@1 1044
duke@1 1045 // Block the thread
duke@1 1046 SafepointSynchronize::block(thread());
duke@1 1047
duke@1 1048 // restore oop result, if any
duke@1 1049 if (return_oop) {
duke@1 1050 caller_fr.set_saved_oop_result(&map, return_value());
duke@1 1051 }
duke@1 1052 }
duke@1 1053
duke@1 1054 // This is a safepoint poll. Verify the return address and block.
duke@1 1055 else {
duke@1 1056 set_at_poll_safepoint(true);
duke@1 1057
duke@1 1058 // verify the blob built the "return address" correctly
duke@1 1059 assert(real_return_addr == caller_fr.pc(), "must match");
duke@1 1060
duke@1 1061 // Block the thread
duke@1 1062 SafepointSynchronize::block(thread());
duke@1 1063 set_at_poll_safepoint(false);
duke@1 1064
duke@1 1065 // If we have a pending async exception deoptimize the frame
duke@1 1066 // as otherwise we may never deliver it.
duke@1 1067 if (thread()->has_async_condition()) {
duke@1 1068 ThreadInVMfromJavaNoAsyncException __tiv(thread());
never@7106 1069 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
duke@1 1070 }
duke@1 1071
duke@1 1072 // If an exception has been installed we must check for a pending deoptimization
duke@1 1073 // Deoptimize frame if exception has been thrown.
duke@1 1074
duke@1 1075 if (thread()->has_pending_exception() ) {
duke@1 1076 RegisterMap map(thread(), true);
duke@1 1077 frame caller_fr = stub_fr.sender(&map);
duke@1 1078 if (caller_fr.is_deoptimized_frame()) {
duke@1 1079 // The exception patch will destroy registers that are still
duke@1 1080 // live and will be needed during deoptimization. Defer the
jwilhelm@22551 1081 // Async exception should have deferred the exception until the
duke@1 1082 // next safepoint which will be detected when we get into
duke@1 1083 // the interpreter so if we have an exception now things
duke@1 1084 // are messed up.
duke@1 1085
duke@1 1086 fatal("Exception installed and deoptimization is pending");
duke@1 1087 }
duke@1 1088 }
duke@1 1089 }
duke@1 1090 }
duke@1 1091
duke@1 1092
duke@1 1093 //
duke@1 1094 // Statistics & Instrumentations
duke@1 1095 //
duke@1 1096 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
xlu@5042 1097 jlong SafepointSynchronize::_safepoint_begin_time = 0;
duke@1 1098 int SafepointSynchronize::_cur_stat_index = 0;
duke@1 1099 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
duke@1 1100 julong SafepointSynchronize::_coalesced_vmop_count = 0;
duke@1 1101 jlong SafepointSynchronize::_max_sync_time = 0;
xlu@5042 1102 jlong SafepointSynchronize::_max_vmop_time = 0;
xlu@5042 1103 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
duke@1 1104
xlu@5042 1105 static jlong cleanup_end_time = 0;
duke@1 1106 static bool need_to_track_page_armed_status = false;
duke@1 1107 static bool init_done = false;
duke@1 1108
xlu@5042 1109 // Helper method to print the header.
xlu@5042 1110 static void print_header() {
xlu@5042 1111 tty->print(" vmop "
xlu@5042 1112 "[threads: total initially_running wait_to_block] ");
xlu@5042 1113 tty->print("[time: spin block sync cleanup vmop] ");
xlu@5042 1114
xlu@5042 1115 // no page armed status printed out if it is always armed.
xlu@5042 1116 if (need_to_track_page_armed_status) {
xlu@5042 1117 tty->print("page_armed ");
xlu@5042 1118 }
xlu@5042 1119
xlu@5042 1120 tty->print_cr("page_trap_count");
xlu@5042 1121 }
xlu@5042 1122
duke@1 1123 void SafepointSynchronize::deferred_initialize_stat() {
duke@1 1124 if (init_done) return;
duke@1 1125
duke@1 1126 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
duke@1 1127 // be printed right away, in which case, _safepoint_stats will regress to
duke@1 1128 // a single element array. Otherwise, it is a circular ring buffer with default
duke@1 1129 // size of PrintSafepointStatisticsCount.
duke@1 1130 int stats_array_size;
duke@1 1131 if (PrintSafepointStatisticsTimeout > 0) {
duke@1 1132 stats_array_size = 1;
duke@1 1133 PrintSafepointStatistics = true;
duke@1 1134 } else {
duke@1 1135 stats_array_size = PrintSafepointStatisticsCount;
duke@1 1136 }
duke@1 1137 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
zgu@13195 1138 * sizeof(SafepointStats), mtInternal);
duke@1 1139 guarantee(_safepoint_stats != NULL,
duke@1 1140 "not enough memory for safepoint instrumentation data");
duke@1 1141
shade@27662 1142 if (DeferPollingPageLoopCount >= 0) {
duke@1 1143 need_to_track_page_armed_status = true;
duke@1 1144 }
duke@1 1145 init_done = true;
duke@1 1146 }
duke@1 1147
duke@1 1148 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
xlu@4006 1149 assert(init_done, "safepoint statistics array hasn't been initialized");
duke@1 1150 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1151
xlu@5042 1152 spstat->_time_stamp = _ts_of_current_safepoint;
xlu@5042 1153
duke@1 1154 VM_Operation *op = VMThread::vm_operation();
duke@1 1155 spstat->_vmop_type = (op != NULL ? op->type() : -1);
duke@1 1156 if (op != NULL) {
duke@1 1157 _safepoint_reasons[spstat->_vmop_type]++;
duke@1 1158 }
duke@1 1159
duke@1 1160 spstat->_nof_total_threads = nof_threads;
duke@1 1161 spstat->_nof_initial_running_threads = nof_running;
duke@1 1162 spstat->_nof_threads_hit_page_trap = 0;
duke@1 1163
duke@1 1164 // Records the start time of spinning. The real time spent on spinning
duke@1 1165 // will be adjusted when spin is done. Same trick is applied for time
duke@1 1166 // spent on waiting for threads to block.
duke@1 1167 if (nof_running != 0) {
duke@1 1168 spstat->_time_to_spin = os::javaTimeNanos();
duke@1 1169 } else {
duke@1 1170 spstat->_time_to_spin = 0;
duke@1 1171 }
duke@1 1172 }
duke@1 1173
duke@1 1174 void SafepointSynchronize::update_statistics_on_spin_end() {
duke@1 1175 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1176
duke@1 1177 jlong cur_time = os::javaTimeNanos();
duke@1 1178
duke@1 1179 spstat->_nof_threads_wait_to_block = _waiting_to_block;
duke@1 1180 if (spstat->_nof_initial_running_threads != 0) {
duke@1 1181 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
duke@1 1182 }
duke@1 1183
duke@1 1184 if (need_to_track_page_armed_status) {
duke@1 1185 spstat->_page_armed = (PageArmed == 1);
duke@1 1186 }
duke@1 1187
duke@1 1188 // Records the start time of waiting for to block. Updated when block is done.
duke@1 1189 if (_waiting_to_block != 0) {
duke@1 1190 spstat->_time_to_wait_to_block = cur_time;
duke@1 1191 } else {
duke@1 1192 spstat->_time_to_wait_to_block = 0;
duke@1 1193 }
duke@1 1194 }
duke@1 1195
duke@1 1196 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
duke@1 1197 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1198
duke@1 1199 if (spstat->_nof_threads_wait_to_block != 0) {
duke@1 1200 spstat->_time_to_wait_to_block = end_time -
duke@1 1201 spstat->_time_to_wait_to_block;
duke@1 1202 }
duke@1 1203
duke@1 1204 // Records the end time of sync which will be used to calculate the total
duke@1 1205 // vm operation time. Again, the real time spending in syncing will be deducted
duke@1 1206 // from the start of the sync time later when end_statistics is called.
xlu@5042 1207 spstat->_time_to_sync = end_time - _safepoint_begin_time;
duke@1 1208 if (spstat->_time_to_sync > _max_sync_time) {
duke@1 1209 _max_sync_time = spstat->_time_to_sync;
duke@1 1210 }
xlu@5042 1211
xlu@5042 1212 spstat->_time_to_do_cleanups = end_time;
xlu@5042 1213 }
xlu@5042 1214
xlu@5042 1215 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
xlu@5042 1216 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
xlu@5042 1217
xlu@5042 1218 // Record how long spent in cleanup tasks.
xlu@5042 1219 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
xlu@5042 1220
xlu@5042 1221 cleanup_end_time = end_time;
duke@1 1222 }
duke@1 1223
duke@1 1224 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
duke@1 1225 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1226
duke@1 1227 // Update the vm operation time.
xlu@5042 1228 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
xlu@5042 1229 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
xlu@5042 1230 _max_vmop_time = spstat->_time_to_exec_vmop;
xlu@5042 1231 }
duke@1 1232 // Only the sync time longer than the specified
duke@1 1233 // PrintSafepointStatisticsTimeout will be printed out right away.
duke@1 1234 // By default, it is -1 meaning all samples will be put into the list.
duke@1 1235 if ( PrintSafepointStatisticsTimeout > 0) {
gziemski@33222 1236 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1237 print_statistics();
duke@1 1238 }
duke@1 1239 } else {
duke@1 1240 // The safepoint statistics will be printed out when the _safepoin_stats
duke@1 1241 // array fills up.
xlu@5042 1242 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
duke@1 1243 print_statistics();
duke@1 1244 _cur_stat_index = 0;
xlu@5042 1245 } else {
xlu@5042 1246 _cur_stat_index++;
duke@1 1247 }
duke@1 1248 }
duke@1 1249 }
duke@1 1250
duke@1 1251 void SafepointSynchronize::print_statistics() {
duke@1 1252 SafepointStats* sstats = _safepoint_stats;
duke@1 1253
xlu@5042 1254 for (int index = 0; index <= _cur_stat_index; index++) {
xlu@5042 1255 if (index % 30 == 0) {
xlu@5042 1256 print_header();
xlu@5042 1257 }
duke@1 1258 sstats = &_safepoint_stats[index];
xlu@5042 1259 tty->print("%.3f: ", sstats->_time_stamp);
xlu@5042 1260 tty->print("%-26s ["
bpittore@31592 1261 INT32_FORMAT_W(8) INT32_FORMAT_W(11) INT32_FORMAT_W(15)
xlu@5042 1262 " ] ",
duke@1 1263 sstats->_vmop_type == -1 ? "no vm operation" :
duke@1 1264 VM_Operation::name(sstats->_vmop_type),
duke@1 1265 sstats->_nof_total_threads,
duke@1 1266 sstats->_nof_initial_running_threads,
duke@1 1267 sstats->_nof_threads_wait_to_block);
duke@1 1268 // "/ MICROUNITS " is to convert the unit from nanos to millis.
xlu@5042 1269 tty->print(" ["
bpittore@31592 1270 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
bpittore@31592 1271 INT64_FORMAT_W(6) INT64_FORMAT_W(6)
bpittore@31592 1272 INT64_FORMAT_W(6) " ] ",
duke@1 1273 sstats->_time_to_spin / MICROUNITS,
duke@1 1274 sstats->_time_to_wait_to_block / MICROUNITS,
duke@1 1275 sstats->_time_to_sync / MICROUNITS,
xlu@5042 1276 sstats->_time_to_do_cleanups / MICROUNITS,
xlu@5042 1277 sstats->_time_to_exec_vmop / MICROUNITS);
duke@1 1278
duke@1 1279 if (need_to_track_page_armed_status) {
bpittore@31592 1280 tty->print(INT32_FORMAT " ", sstats->_page_armed);
duke@1 1281 }
bpittore@31592 1282 tty->print_cr(INT32_FORMAT " ", sstats->_nof_threads_hit_page_trap);
duke@1 1283 }
duke@1 1284 }
duke@1 1285
duke@1 1286 // This method will be called when VM exits. It will first call
duke@1 1287 // print_statistics to print out the rest of the sampling. Then
duke@1 1288 // it tries to summarize the sampling.
duke@1 1289 void SafepointSynchronize::print_stat_on_exit() {
duke@1 1290 if (_safepoint_stats == NULL) return;
duke@1 1291
duke@1 1292 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1293
duke@1 1294 // During VM exit, end_statistics may not get called and in that
duke@1 1295 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
duke@1 1296 // don't print it out.
duke@1 1297 // Approximate the vm op time.
duke@1 1298 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
xlu@5042 1299 os::javaTimeNanos() - cleanup_end_time;
duke@1 1300
duke@1 1301 if ( PrintSafepointStatisticsTimeout < 0 ||
gziemski@33222 1302 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1303 print_statistics();
duke@1 1304 }
drchase@24424 1305 tty->cr();
duke@1 1306
duke@1 1307 // Print out polling page sampling status.
duke@1 1308 if (!need_to_track_page_armed_status) {
shade@27662 1309 tty->print_cr("Polling page always armed");
duke@1 1310 } else {
david@33148 1311 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
david@33148 1312 DeferPollingPageLoopCount);
duke@1 1313 }
duke@1 1314
duke@1 1315 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
duke@1 1316 if (_safepoint_reasons[index] != 0) {
bpittore@31592 1317 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
duke@1 1318 _safepoint_reasons[index]);
duke@1 1319 }
duke@1 1320 }
duke@1 1321
bpittore@31592 1322 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
duke@1 1323 _coalesced_vmop_count);
bpittore@31592 1324 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
duke@1 1325 _max_sync_time / MICROUNITS);
xlu@5042 1326 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
bpittore@31592 1327 INT64_FORMAT_W(5) " ms",
xlu@5042 1328 _max_vmop_time / MICROUNITS);
duke@1 1329 }
duke@1 1330
duke@1 1331 // ------------------------------------------------------------------------------------------------
duke@1 1332 // Non-product code
duke@1 1333
duke@1 1334 #ifndef PRODUCT
duke@1 1335
duke@1 1336 void SafepointSynchronize::print_state() {
duke@1 1337 if (_state == _not_synchronized) {
duke@1 1338 tty->print_cr("not synchronized");
duke@1 1339 } else if (_state == _synchronizing || _state == _synchronized) {
duke@1 1340 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
duke@1 1341 "synchronized");
duke@1 1342
duke@1 1343 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 1344 cur->safepoint_state()->print();
duke@1 1345 }
duke@1 1346 }
duke@1 1347 }
duke@1 1348
duke@1 1349 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
duke@1 1350 if (ShowSafepointMsgs) {
duke@1 1351 va_list ap;
duke@1 1352 va_start(ap, format);
duke@1 1353 tty->vprint_cr(format, ap);
duke@1 1354 va_end(ap);
duke@1 1355 }
duke@1 1356 }
duke@1 1357
duke@1 1358 #endif // !PRODUCT