annotate src/hotspot/share/runtime/safepoint.cpp @ 48321:8d15b1369c7a

8167108: inconsistent handling of SR_lock can lead to crashes Summary: Add Thread Safe Memory Reclamation (Thread-SMR) mechanism. Reviewed-by: coleenp, dcubed, dholmes, eosterlund, gthornbr, kbarrett, rehn, sspitsyn, stefank Contributed-by: daniel.daugherty@oracle.com, erik.osterlund@oracle.com, robbin.ehn@oracle.com
author dcubed
date Wed, 22 Nov 2017 17:54:50 -0800
parents 0ce0ac68ace7
children de2e4ff493bf
rev   line source
duke@1 1 /*
shade@46473 2 * Copyright (c) 1997, 2017, 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@47955 26 #include "classfile/classLoaderData.hpp"
gziemski@24426 27 #include "classfile/stringTable.hpp"
mgronlun@34666 28 #include "classfile/symbolTable.hpp"
stefank@7397 29 #include "classfile/systemDictionary.hpp"
stefank@7397 30 #include "code/codeCache.hpp"
stefank@7397 31 #include "code/icBuffer.hpp"
stefank@7397 32 #include "code/nmethod.hpp"
stefank@7397 33 #include "code/pcDesc.hpp"
stefank@7397 34 #include "code/scopeDesc.hpp"
pliden@30764 35 #include "gc/shared/collectedHeap.hpp"
pliden@30764 36 #include "gc/shared/gcLocker.inline.hpp"
rkennke@46702 37 #include "gc/shared/strongRootsScope.hpp"
rkennke@46702 38 #include "gc/shared/workgroup.hpp"
stefank@7397 39 #include "interpreter/interpreter.hpp"
rprotacio@33763 40 #include "logging/log.hpp"
stuefe@46701 41 #include "logging/logStream.hpp"
stefank@7397 42 #include "memory/resourceArea.hpp"
stefank@7397 43 #include "memory/universe.inline.hpp"
stefank@7397 44 #include "oops/oop.inline.hpp"
coleenp@8076 45 #include "oops/symbol.hpp"
dholmes@40655 46 #include "runtime/atomic.hpp"
stefank@7397 47 #include "runtime/compilationPolicy.hpp"
stefank@7397 48 #include "runtime/deoptimization.hpp"
stefank@7397 49 #include "runtime/frame.inline.hpp"
stefank@7397 50 #include "runtime/interfaceSupport.hpp"
stefank@7397 51 #include "runtime/mutexLocker.hpp"
goetz@24351 52 #include "runtime/orderAccess.inline.hpp"
stefank@7397 53 #include "runtime/osThread.hpp"
stefank@7397 54 #include "runtime/safepoint.hpp"
rehn@48069 55 #include "runtime/safepointMechanism.inline.hpp"
stefank@7397 56 #include "runtime/signature.hpp"
stefank@7397 57 #include "runtime/stubCodeGenerator.hpp"
stefank@7397 58 #include "runtime/stubRoutines.hpp"
stefank@7397 59 #include "runtime/sweeper.hpp"
stefank@7397 60 #include "runtime/synchronizer.hpp"
stefank@14583 61 #include "runtime/thread.inline.hpp"
dcubed@48321 62 #include "runtime/threadSMR.hpp"
rehn@37161 63 #include "runtime/timerTrace.hpp"
stefank@7397 64 #include "services/runtimeService.hpp"
dsimms@37176 65 #include "trace/tracing.hpp"
dsimms@37176 66 #include "trace/traceMacros.hpp"
stefank@7397 67 #include "utilities/events.hpp"
jprovino@15482 68 #include "utilities/macros.hpp"
stefank@7397 69 #ifdef COMPILER1
stefank@7397 70 #include "c1/c1_globals.hpp"
stefank@7397 71 #endif
duke@1 72
duke@1 73 // --------------------------------------------------------------------------------------------------
duke@1 74 // Implementation of Safepoint begin/end
duke@1 75
duke@1 76 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
duke@1 77 volatile int SafepointSynchronize::_waiting_to_block = 0;
duke@1 78 volatile int SafepointSynchronize::_safepoint_counter = 0;
never@11631 79 int SafepointSynchronize::_current_jni_active_count = 0;
xlu@5042 80 long SafepointSynchronize::_end_of_last_safepoint = 0;
duke@1 81 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
duke@1 82 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
duke@1 83 static bool timeout_error_printed = false;
duke@1 84
duke@1 85 // Roll all threads forward to a safepoint and suspend them all
duke@1 86 void SafepointSynchronize::begin() {
dsimms@37176 87 EventSafepointBegin begin_event;
duke@1 88 Thread* myThread = Thread::current();
duke@1 89 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
duke@1 90
xlu@5042 91 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@5042 92 _safepoint_begin_time = os::javaTimeNanos();
xlu@5042 93 _ts_of_current_safepoint = tty->time_stamp().seconds();
xlu@5042 94 }
duke@1 95
eosterlund@47791 96 Universe::heap()->safepoint_synchronize_begin();
duke@1 97
duke@1 98 // By getting the Threads_lock, we assure that no threads are about to start or
duke@1 99 // exit. It is released again in SafepointSynchronize::end().
duke@1 100 Threads_lock->lock();
duke@1 101
duke@1 102 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
duke@1 103
duke@1 104 int nof_threads = Threads::number_of_threads();
duke@1 105
rprotacio@33763 106 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
duke@1 107
duke@1 108 RuntimeService::record_safepoint_begin();
duke@1 109
duke@1 110 MutexLocker mu(Safepoint_lock);
duke@1 111
never@11631 112 // Reset the count of active JNI critical threads
never@11631 113 _current_jni_active_count = 0;
never@11631 114
duke@1 115 // Set number of threads to wait for, before we initiate the callbacks
duke@1 116 _waiting_to_block = nof_threads;
duke@1 117 TryingToBlock = 0 ;
duke@1 118 int still_running = nof_threads;
duke@1 119
duke@1 120 // Save the starting time, so that it can be compared to see if this has taken
duke@1 121 // too long to complete.
goetz@33589 122 jlong safepoint_limit_time = 0;
duke@1 123 timeout_error_printed = false;
duke@1 124
xlu@4006 125 // PrintSafepointStatisticsTimeout can be specified separately. When
xlu@4006 126 // specified, PrintSafepointStatistics will be set to true in
xlu@4006 127 // deferred_initialize_stat method. The initialization has to be done
xlu@4006 128 // early enough to avoid any races. See bug 6880029 for details.
xlu@4006 129 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@4006 130 deferred_initialize_stat();
xlu@4006 131 }
xlu@4006 132
duke@1 133 // Begin the process of bringing the system to a safepoint.
duke@1 134 // Java threads can be in several different states and are
duke@1 135 // stopped by different mechanisms:
duke@1 136 //
duke@1 137 // 1. Running interpreted
jwilhelm@22551 138 // The interpreter dispatch table is changed to force it to
duke@1 139 // check for a safepoint condition between bytecodes.
duke@1 140 // 2. Running in native code
duke@1 141 // When returning from the native code, a Java thread must check
duke@1 142 // the safepoint _state to see if we must block. If the
duke@1 143 // VM thread sees a Java thread in native, it does
duke@1 144 // not wait for this thread to block. The order of the memory
duke@1 145 // writes and reads of both the safepoint state and the Java
duke@1 146 // threads state is critical. In order to guarantee that the
duke@1 147 // memory writes are serialized with respect to each other,
duke@1 148 // the VM thread issues a memory barrier instruction
duke@1 149 // (on MP systems). In order to avoid the overhead of issuing
duke@1 150 // a memory barrier for each Java thread making native calls, each Java
duke@1 151 // thread performs a write to a single memory page after changing
duke@1 152 // the thread state. The VM thread performs a sequence of
duke@1 153 // mprotect OS calls which forces all previous writes from all
duke@1 154 // Java threads to be serialized. This is done in the
duke@1 155 // os::serialize_thread_states() call. This has proven to be
duke@1 156 // much more efficient than executing a membar instruction
duke@1 157 // on every call to native code.
duke@1 158 // 3. Running compiled Code
duke@1 159 // Compiled code reads a global (Safepoint Polling) page that
duke@1 160 // is set to fault if we are trying to get to a safepoint.
duke@1 161 // 4. Blocked
duke@1 162 // A thread which is blocked will not be allowed to return from the
duke@1 163 // block condition until the safepoint operation is complete.
duke@1 164 // 5. In VM or Transitioning between states
duke@1 165 // If a Java thread is currently running in the VM or transitioning
duke@1 166 // between states, the safepointing code will wait for the thread to
duke@1 167 // block itself when it attempts transitions to a new state.
duke@1 168 //
dsimms@37176 169 {
egahlin@40664 170 EventSafepointStateSynchronization sync_event;
dsimms@37176 171 int initial_running = 0;
duke@1 172
dsimms@37176 173 _state = _synchronizing;
rehn@48069 174
rehn@48069 175 if (SafepointMechanism::uses_thread_local_poll()) {
rehn@48069 176 // Arming the per thread poll while having _state != _not_synchronized means safepointing
rehn@48069 177 log_trace(safepoint)("Setting thread local yield flag for threads");
dcubed@48321 178 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
rehn@48069 179 // Make sure the threads start polling, it is time to yield.
rehn@48069 180 SafepointMechanism::arm_local_poll(cur); // release store, global state -> local state
rehn@48069 181 }
rehn@48069 182 }
rehn@48069 183 OrderAccess::fence(); // storestore|storeload, global state -> local state
duke@1 184
dsimms@37176 185 // Flush all thread states to memory
dsimms@37176 186 if (!UseMembar) {
dsimms@37176 187 os::serialize_thread_states();
dsimms@37176 188 }
duke@1 189
rehn@48069 190 if (SafepointMechanism::uses_global_page_poll()) {
rehn@48069 191 // Make interpreter safepoint aware
rehn@48069 192 Interpreter::notice_safepoints();
duke@1 193
rehn@48069 194 if (DeferPollingPageLoopCount < 0) {
rehn@48069 195 // Make polling safepoint aware
rehn@48069 196 guarantee (PageArmed == 0, "invariant") ;
rehn@48069 197 PageArmed = 1 ;
rehn@48069 198 os::make_polling_page_unreadable();
rehn@48069 199 }
dsimms@37176 200 }
dsimms@37176 201
dsimms@37176 202 // Consider using active_processor_count() ... but that call is expensive.
dsimms@37176 203 int ncpus = os::processor_count() ;
dcubed@48321 204 unsigned int iterations = 0;
duke@1 205
dcubed@48321 206 {
dcubed@48321 207 JavaThreadIteratorWithHandle jtiwh;
duke@1 208 #ifdef ASSERT
dcubed@48321 209 for (; JavaThread *cur = jtiwh.next(); ) {
dcubed@48321 210 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
dcubed@48321 211 // Clear the visited flag to ensure that the critical counts are collected properly.
dcubed@48321 212 cur->set_visited_for_critical_count(false);
dcubed@48321 213 }
duke@1 214 #endif // ASSERT
duke@1 215
dcubed@48321 216 if (SafepointTimeout)
dcubed@48321 217 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
duke@1 218
dcubed@48321 219 // Iterate through all threads until it have been determined how to stop them all at a safepoint
dcubed@48321 220 int steps = 0 ;
dcubed@48321 221 while(still_running > 0) {
dcubed@48321 222 jtiwh.rewind();
dcubed@48321 223 for (; JavaThread *cur = jtiwh.next(); ) {
dcubed@48321 224 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
dcubed@48321 225 ThreadSafepointState *cur_state = cur->safepoint_state();
dcubed@48321 226 if (cur_state->is_running()) {
dcubed@48321 227 cur_state->examine_state_of_thread();
dcubed@48321 228 if (!cur_state->is_running()) {
dcubed@48321 229 still_running--;
dcubed@48321 230 // consider adjusting steps downward:
dcubed@48321 231 // steps = 0
dcubed@48321 232 // steps -= NNN
dcubed@48321 233 // steps >>= 1
dcubed@48321 234 // steps = MIN(steps, 2000-100)
dcubed@48321 235 // if (iterations != 0) steps -= NNN
dcubed@48321 236 }
dcubed@48321 237 LogTarget(Trace, safepoint) lt;
dcubed@48321 238 if (lt.is_enabled()) {
dcubed@48321 239 ResourceMark rm;
dcubed@48321 240 LogStream ls(lt);
dcubed@48321 241 cur_state->print_on(&ls);
dcubed@48321 242 }
dsimms@37176 243 }
duke@1 244 }
dsimms@37176 245
dcubed@48321 246 if (iterations == 0) {
dcubed@48321 247 initial_running = still_running;
dcubed@48321 248 if (PrintSafepointStatistics) {
dcubed@48321 249 begin_statistics(nof_threads, still_running);
dcubed@48321 250 }
dsimms@37176 251 }
dsimms@37176 252
dcubed@48321 253 if (still_running > 0) {
dcubed@48321 254 // Check for if it takes to long
dcubed@48321 255 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
dcubed@48321 256 print_safepoint_timeout(_spinning_timeout);
dsimms@37176 257 }
dsimms@37176 258
dcubed@48321 259 // Spin to avoid context switching.
dcubed@48321 260 // There's a tension between allowing the mutators to run (and rendezvous)
dcubed@48321 261 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
dcubed@48321 262 // a mutator might otherwise use profitably to reach a safepoint. Excessive
dcubed@48321 263 // spinning by the VM thread on a saturated system can increase rendezvous latency.
dcubed@48321 264 // Blocking or yielding incur their own penalties in the form of context switching
dcubed@48321 265 // and the resultant loss of $ residency.
dcubed@48321 266 //
dcubed@48321 267 // Further complicating matters is that yield() does not work as naively expected
dcubed@48321 268 // on many platforms -- yield() does not guarantee that any other ready threads
dcubed@48321 269 // will run. As such we revert to naked_short_sleep() after some number of iterations.
dcubed@48321 270 // nakes_short_sleep() is implemented as a short unconditional sleep.
dcubed@48321 271 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
dcubed@48321 272 // can actually increase the time it takes the VM thread to detect that a system-wide
dcubed@48321 273 // stop-the-world safepoint has been reached. In a pathological scenario such as that
dcubed@48321 274 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
dcubed@48321 275 // In that case the mutators will be stalled waiting for the safepoint to complete and the
dcubed@48321 276 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
dcubed@48321 277 // will eventually wake up and detect that all mutators are safe, at which point
dcubed@48321 278 // we'll again make progress.
dcubed@48321 279 //
dcubed@48321 280 // Beware too that that the VMThread typically runs at elevated priority.
dcubed@48321 281 // Its default priority is higher than the default mutator priority.
dcubed@48321 282 // Obviously, this complicates spinning.
dcubed@48321 283 //
dcubed@48321 284 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
dcubed@48321 285 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
dcubed@48321 286 //
dcubed@48321 287 // See the comments in synchronizer.cpp for additional remarks on spinning.
dcubed@48321 288 //
dcubed@48321 289 // In the future we might:
dcubed@48321 290 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
dcubed@48321 291 // This is tricky as the path used by a thread exiting the JVM (say on
dcubed@48321 292 // on JNI call-out) simply stores into its state field. The burden
dcubed@48321 293 // is placed on the VM thread, which must poll (spin).
dcubed@48321 294 // 2. Find something useful to do while spinning. If the safepoint is GC-related
dcubed@48321 295 // we might aggressively scan the stacks of threads that are already safe.
dcubed@48321 296 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
dcubed@48321 297 // If all the mutators are ONPROC there's no reason to sleep or yield.
dcubed@48321 298 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
dcubed@48321 299 // 5. Check system saturation. If the system is not fully saturated then
dcubed@48321 300 // simply spin and avoid sleep/yield.
dcubed@48321 301 // 6. As still-running mutators rendezvous they could unpark the sleeping
dcubed@48321 302 // VMthread. This works well for still-running mutators that become
dcubed@48321 303 // safe. The VMthread must still poll for mutators that call-out.
dcubed@48321 304 // 7. Drive the policy on time-since-begin instead of iterations.
dcubed@48321 305 // 8. Consider making the spin duration a function of the # of CPUs:
dcubed@48321 306 // Spin = (((ncpus-1) * M) + K) + F(still_running)
dcubed@48321 307 // Alternately, instead of counting iterations of the outer loop
dcubed@48321 308 // we could count the # of threads visited in the inner loop, above.
dcubed@48321 309 // 9. On windows consider using the return value from SwitchThreadTo()
dcubed@48321 310 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
dcubed@48321 311
dcubed@48321 312 if (SafepointMechanism::uses_global_page_poll() && int(iterations) == DeferPollingPageLoopCount) {
dcubed@48321 313 guarantee (PageArmed == 0, "invariant") ;
dcubed@48321 314 PageArmed = 1 ;
dcubed@48321 315 os::make_polling_page_unreadable();
dcubed@48321 316 }
dcubed@48321 317
dcubed@48321 318 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
dcubed@48321 319 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
dcubed@48321 320 ++steps ;
dcubed@48321 321 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
dcubed@48321 322 SpinPause() ; // MP-Polite spin
dcubed@48321 323 } else
dcubed@48321 324 if (steps < DeferThrSuspendLoopCount) {
dcubed@48321 325 os::naked_yield() ;
dcubed@48321 326 } else {
dcubed@48321 327 os::naked_short_sleep(1);
dcubed@48321 328 }
dcubed@48321 329
dcubed@48321 330 iterations ++ ;
dcubed@48321 331 }
dcubed@48321 332 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
dsimms@37176 333 }
dcubed@48321 334 } // ThreadsListHandle destroyed here.
dsimms@37176 335 assert(still_running == 0, "sanity check");
dsimms@37176 336
dsimms@37176 337 if (PrintSafepointStatistics) {
dsimms@37176 338 update_statistics_on_spin_end();
dsimms@37176 339 }
dsimms@37176 340
dsimms@37176 341 if (sync_event.should_commit()) {
egahlin@47784 342 // Group this event together with the ones committed after the counter is increased
egahlin@47784 343 sync_event.set_safepointId(safepoint_counter() + 1);
dsimms@37176 344 sync_event.set_initialThreadCount(initial_running);
dsimms@37176 345 sync_event.set_runningThreadCount(_waiting_to_block);
dsimms@37176 346 sync_event.set_iterations(iterations);
dsimms@37176 347 sync_event.commit();
dsimms@37176 348 }
dcubed@48321 349 } // EventSafepointStateSynchronization destroyed here.
dsimms@37176 350
dsimms@37176 351 // wait until all threads are stopped
dsimms@37176 352 {
dsimms@37176 353 EventSafepointWaitBlocked wait_blocked_event;
dsimms@37176 354 int initial_waiting_to_block = _waiting_to_block;
dsimms@37176 355
dsimms@37176 356 while (_waiting_to_block > 0) {
dsimms@37176 357 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
dsimms@37176 358 if (!SafepointTimeout || timeout_error_printed) {
dsimms@37176 359 Safepoint_lock->wait(true); // true, means with no safepoint checks
dsimms@37176 360 } else {
dsimms@37176 361 // Compute remaining time
dsimms@37176 362 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
dsimms@37176 363
dsimms@37176 364 // If there is no remaining time, then there is an error
dsimms@37176 365 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
dsimms@37176 366 print_safepoint_timeout(_blocking_timeout);
rprotacio@33763 367 }
duke@1 368 }
duke@1 369 }
dsimms@37176 370 assert(_waiting_to_block == 0, "sanity check");
duke@1 371
dsimms@37176 372 #ifndef PRODUCT
dsimms@37176 373 if (SafepointTimeout) {
dsimms@37176 374 jlong current_time = os::javaTimeNanos();
dsimms@37176 375 if (safepoint_limit_time < current_time) {
dsimms@37176 376 tty->print_cr("# SafepointSynchronize: Finished after "
dsimms@37176 377 INT64_FORMAT_W(6) " ms",
jwilhelm@46630 378 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
jwilhelm@46630 379 (jlong)SafepointTimeoutDelay));
duke@1 380 }
duke@1 381 }
duke@1 382 #endif
duke@1 383
dsimms@37176 384 assert((_safepoint_counter & 0x1) == 0, "must be even");
dsimms@37176 385 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
dsimms@37176 386 _safepoint_counter ++;
duke@1 387
dsimms@37176 388 // Record state
dsimms@37176 389 _state = _synchronized;
duke@1 390
dsimms@37176 391 OrderAccess::fence();
dsimms@37176 392
dsimms@37176 393 if (wait_blocked_event.should_commit()) {
dsimms@37176 394 wait_blocked_event.set_safepointId(safepoint_counter());
dsimms@37176 395 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
dsimms@37176 396 wait_blocked_event.commit();
dsimms@37176 397 }
dsimms@37176 398 } // EventSafepointWaitBlocked
duke@1 399
never@12108 400 #ifdef ASSERT
dcubed@48321 401 // Make sure all the threads were visited.
dcubed@48321 402 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
never@12108 403 assert(cur->was_visited_for_critical_count(), "missed a thread");
never@12108 404 }
never@12108 405 #endif // ASSERT
never@12108 406
never@11631 407 // Update the count of active JNI critical regions
david@35492 408 GCLocker::set_jni_lock_count(_current_jni_active_count);
never@11631 409
rprotacio@33763 410 if (log_is_enabled(Debug, safepoint)) {
rehn@46496 411 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
duke@1 412 }
duke@1 413
duke@1 414 RuntimeService::record_safepoint_synchronized();
duke@1 415 if (PrintSafepointStatistics) {
duke@1 416 update_statistics_on_sync_end(os::javaTimeNanos());
duke@1 417 }
duke@1 418
duke@1 419 // Call stuff that needs to be run when a safepoint is just about to be completed
dsimms@37176 420 {
dsimms@37176 421 EventSafepointCleanup cleanup_event;
dsimms@37176 422 do_cleanup_tasks();
dsimms@37176 423 if (cleanup_event.should_commit()) {
dsimms@37176 424 cleanup_event.set_safepointId(safepoint_counter());
dsimms@37176 425 cleanup_event.commit();
dsimms@37176 426 }
dsimms@37176 427 }
xlu@5042 428
xlu@5042 429 if (PrintSafepointStatistics) {
xlu@5042 430 // Record how much time spend on the above cleanup tasks
xlu@5042 431 update_statistics_on_cleanup_end(os::javaTimeNanos());
xlu@5042 432 }
dsimms@37176 433 if (begin_event.should_commit()) {
dsimms@37176 434 begin_event.set_safepointId(safepoint_counter());
dsimms@37176 435 begin_event.set_totalThreadCount(nof_threads);
dsimms@37176 436 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
dsimms@37176 437 begin_event.commit();
dsimms@37176 438 }
duke@1 439 }
duke@1 440
duke@1 441 // Wake up all threads, so they are ready to resume execution after the safepoint
duke@1 442 // operation has been carried out
duke@1 443 void SafepointSynchronize::end() {
dsimms@37176 444 EventSafepointEnd event;
dsimms@37176 445 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
duke@1 446
duke@1 447 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 448 assert((_safepoint_counter & 0x1) == 1, "must be odd");
duke@1 449 _safepoint_counter ++;
duke@1 450 // memory fence isn't required here since an odd _safepoint_counter
duke@1 451 // value can do no harm and a fence is issued below anyway.
duke@1 452
duke@1 453 DEBUG_ONLY(Thread* myThread = Thread::current();)
duke@1 454 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
duke@1 455
duke@1 456 if (PrintSafepointStatistics) {
duke@1 457 end_statistics(os::javaTimeNanos());
duke@1 458 }
duke@1 459
dcubed@48321 460 {
dcubed@48321 461 JavaThreadIteratorWithHandle jtiwh;
duke@1 462 #ifdef ASSERT
dcubed@48321 463 // A pending_exception cannot be installed during a safepoint. The threads
dcubed@48321 464 // may install an async exception after they come back from a safepoint into
dcubed@48321 465 // pending_exception after they unblock. But that should happen later.
dcubed@48321 466 for (; JavaThread *cur = jtiwh.next(); ) {
dcubed@48321 467 assert (!(cur->has_pending_exception() &&
dcubed@48321 468 cur->safepoint_state()->is_at_poll_safepoint()),
dcubed@48321 469 "safepoint installed a pending exception");
dcubed@48321 470 }
duke@1 471 #endif // ASSERT
duke@1 472
dcubed@48321 473 if (PageArmed) {
dcubed@48321 474 assert(SafepointMechanism::uses_global_page_poll(), "sanity");
dcubed@48321 475 // Make polling safepoint aware
dcubed@48321 476 os::make_polling_page_readable();
dcubed@48321 477 PageArmed = 0 ;
duke@1 478 }
duke@1 479
dcubed@48321 480 if (SafepointMechanism::uses_global_page_poll()) {
dcubed@48321 481 // Remove safepoint check from interpreter
dcubed@48321 482 Interpreter::ignore_safepoints();
dcubed@48321 483 }
duke@1 484
dcubed@48321 485 {
dcubed@48321 486 MutexLocker mu(Safepoint_lock);
duke@1 487
dcubed@48321 488 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
dcubed@48321 489
dcubed@48321 490 if (SafepointMechanism::uses_thread_local_poll()) {
dcubed@48321 491 _state = _not_synchronized;
dcubed@48321 492 OrderAccess::storestore(); // global state -> local state
dcubed@48321 493 jtiwh.rewind();
dcubed@48321 494 for (; JavaThread *current = jtiwh.next(); ) {
dcubed@48321 495 ThreadSafepointState* cur_state = current->safepoint_state();
dcubed@48321 496 cur_state->restart(); // TSS _running
dcubed@48321 497 SafepointMechanism::disarm_local_poll(current); // release store, local state -> polling page
dcubed@48321 498 }
dcubed@48321 499 log_debug(safepoint)("Leaving safepoint region");
dcubed@48321 500 } else {
dcubed@48321 501 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
dcubed@48321 502 // when they get restarted.
dcubed@48321 503 _state = _not_synchronized;
dcubed@48321 504 OrderAccess::fence();
dcubed@48321 505
dcubed@48321 506 log_debug(safepoint)("Leaving safepoint region");
dcubed@48321 507
dcubed@48321 508 // Start suspended threads
dcubed@48321 509 jtiwh.rewind();
dcubed@48321 510 for (; JavaThread *current = jtiwh.next(); ) {
dcubed@48321 511 // A problem occurring on Solaris is when attempting to restart threads
dcubed@48321 512 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
dcubed@48321 513 // to the next one (since it has been running the longest). We then have
dcubed@48321 514 // to wait for a cpu to become available before we can continue restarting
dcubed@48321 515 // threads.
dcubed@48321 516 // FIXME: This causes the performance of the VM to degrade when active and with
dcubed@48321 517 // large numbers of threads. Apparently this is due to the synchronous nature
dcubed@48321 518 // of suspending threads.
dcubed@48321 519 //
dcubed@48321 520 // TODO-FIXME: the comments above are vestigial and no longer apply.
dcubed@48321 521 // Furthermore, using solaris' schedctl in this particular context confers no benefit
dcubed@48321 522 if (VMThreadHintNoPreempt) {
dcubed@48321 523 os::hint_no_preempt();
dcubed@48321 524 }
dcubed@48321 525 ThreadSafepointState* cur_state = current->safepoint_state();
dcubed@48321 526 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
dcubed@48321 527 cur_state->restart();
dcubed@48321 528 assert(cur_state->is_running(), "safepoint state has not been reset");
dcubed@48321 529 }
dcubed@48321 530 }
dcubed@48321 531
dcubed@48321 532 RuntimeService::record_safepoint_end();
dcubed@48321 533
dcubed@48321 534 // Release threads lock, so threads can be created/destroyed again.
dcubed@48321 535 // It will also release all threads blocked in signal_thread_blocked.
dcubed@48321 536 Threads_lock->unlock();
dcubed@48321 537 }
dcubed@48321 538 } // ThreadsListHandle destroyed here.
dcubed@48321 539
eosterlund@47791 540 Universe::heap()->safepoint_synchronize_end();
jwilhelm@22551 541 // record this time so VMThread can keep track how much time has elapsed
xlu@5042 542 // since last safepoint.
xlu@5042 543 _end_of_last_safepoint = os::javaTimeMillis();
dsimms@37176 544
dsimms@37176 545 if (event.should_commit()) {
dsimms@37176 546 event.set_safepointId(safepoint_id);
dsimms@37176 547 event.commit();
dsimms@37176 548 }
duke@1 549 }
duke@1 550
duke@1 551 bool SafepointSynchronize::is_cleanup_needed() {
rehn@46541 552 // Need a safepoint if there are many monitors to deflate.
rehn@46541 553 if (ObjectSynchronizer::is_cleanup_needed()) return true;
duke@1 554 // Need a safepoint if some inline cache buffers is non-empty
duke@1 555 if (!InlineCacheBuffer::is_empty()) return true;
duke@1 556 return false;
duke@1 557 }
duke@1 558
dsimms@37176 559 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
dsimms@37176 560 if (event.should_commit()) {
dsimms@37176 561 event.set_safepointId(SafepointSynchronize::safepoint_counter());
dsimms@37176 562 event.set_name(name);
dsimms@37176 563 event.commit();
dsimms@37176 564 }
dsimms@37176 565 }
duke@1 566
rkennke@46702 567 class ParallelSPCleanupThreadClosure : public ThreadClosure {
rkennke@46702 568 private:
rkennke@46702 569 CodeBlobClosure* _nmethod_cl;
rkennke@46702 570 DeflateMonitorCounters* _counters;
rkennke@46702 571
rkennke@46702 572 public:
rkennke@46702 573 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
rkennke@46702 574 _counters(counters),
rkennke@46702 575 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
rkennke@46702 576
rkennke@46702 577 void do_thread(Thread* thread) {
rkennke@46702 578 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
rkennke@46702 579 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
rkennke@46702 580 ! thread->is_Code_cache_sweeper_thread()) {
rkennke@46702 581 JavaThread* jt = (JavaThread*) thread;
rkennke@46702 582 jt->nmethods_do(_nmethod_cl);
rkennke@46702 583 }
rkennke@46702 584 }
rkennke@46702 585 };
rkennke@46702 586
rkennke@46702 587 class ParallelSPCleanupTask : public AbstractGangTask {
rkennke@46702 588 private:
rkennke@46702 589 SubTasksDone _subtasks;
rkennke@46702 590 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
rkennke@46702 591 uint _num_workers;
rkennke@46702 592 DeflateMonitorCounters* _counters;
rkennke@46702 593 public:
rkennke@46702 594 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
rkennke@46702 595 AbstractGangTask("Parallel Safepoint Cleanup"),
rkennke@46702 596 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
rkennke@46702 597 _num_workers(num_workers),
rkennke@46702 598 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
rkennke@46702 599 _counters(counters) {}
rkennke@46702 600
rkennke@46702 601 void work(uint worker_id) {
rkennke@46702 602 // All threads deflate monitors and mark nmethods (if necessary).
rkennke@47792 603 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
rkennke@46702 604
rkennke@46702 605 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
rkennke@46702 606 const char* name = "deflating idle monitors";
rkennke@46702 607 EventSafepointCleanupTask event;
rkennke@46702 608 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 609 ObjectSynchronizer::deflate_idle_monitors(_counters);
rkennke@46702 610 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 611 }
rkennke@46702 612
rkennke@46702 613 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
rkennke@46702 614 const char* name = "updating inline caches";
rkennke@46702 615 EventSafepointCleanupTask event;
rkennke@46702 616 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 617 InlineCacheBuffer::update_inline_caches();
rkennke@46702 618 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 619 }
rkennke@46702 620
rkennke@46702 621 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
rkennke@46702 622 const char* name = "compilation policy safepoint handler";
rkennke@46702 623 EventSafepointCleanupTask event;
rkennke@46702 624 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 625 CompilationPolicy::policy()->do_safepoint_work();
rkennke@46702 626 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 627 }
rkennke@46702 628
rkennke@46702 629 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
rkennke@46702 630 if (SymbolTable::needs_rehashing()) {
rkennke@46702 631 const char* name = "rehashing symbol table";
rkennke@46702 632 EventSafepointCleanupTask event;
rkennke@46702 633 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 634 SymbolTable::rehash_table();
rkennke@46702 635 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 636 }
rkennke@46702 637 }
rkennke@46702 638
rkennke@46702 639 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
rkennke@46702 640 if (StringTable::needs_rehashing()) {
rkennke@46702 641 const char* name = "rehashing string table";
rkennke@46702 642 EventSafepointCleanupTask event;
rkennke@46702 643 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 644 StringTable::rehash_table();
rkennke@46702 645 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 646 }
rkennke@46702 647 }
rkennke@46702 648
rkennke@46702 649 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_CLD_PURGE)) {
rkennke@46702 650 // CMS delays purging the CLDG until the beginning of the next safepoint and to
rkennke@46702 651 // make sure concurrent sweep is done
rkennke@46702 652 const char* name = "purging class loader data graph";
rkennke@46702 653 EventSafepointCleanupTask event;
rkennke@46702 654 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 655 ClassLoaderDataGraph::purge_if_needed();
rkennke@46702 656 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 657 }
gziemski@47955 658
gziemski@47955 659 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
gziemski@47955 660 const char* name = "resizing system dictionaries";
gziemski@47955 661 EventSafepointCleanupTask event;
gziemski@47955 662 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
gziemski@47955 663 ClassLoaderDataGraph::resize_if_needed();
gziemski@47955 664 event_safepoint_cleanup_task_commit(event, name);
gziemski@47955 665 }
rkennke@46702 666 _subtasks.all_tasks_completed(_num_workers);
rkennke@46702 667 }
rkennke@46702 668 };
rkennke@46702 669
rkennke@46702 670 // Various cleaning tasks that should be done periodically at safepoints.
duke@1 671 void SafepointSynchronize::do_cleanup_tasks() {
rkennke@46702 672
rkennke@46702 673 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 674
rkennke@46702 675 // Prepare for monitor deflation.
rkennke@46702 676 DeflateMonitorCounters deflate_counters;
rkennke@46702 677 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
rkennke@46702 678
rkennke@46702 679 CollectedHeap* heap = Universe::heap();
rkennke@46702 680 assert(heap != NULL, "heap not initialized yet?");
rkennke@46702 681 WorkGang* cleanup_workers = heap->get_safepoint_workers();
rkennke@46702 682 if (cleanup_workers != NULL) {
rkennke@46702 683 // Parallel cleanup using GC provided thread pool.
rkennke@46702 684 uint num_cleanup_workers = cleanup_workers->active_workers();
rkennke@46702 685 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
rkennke@46702 686 StrongRootsScope srs(num_cleanup_workers);
rkennke@46702 687 cleanup_workers->run_task(&cleanup);
rkennke@46702 688 } else {
rkennke@46702 689 // Serial cleanup using VMThread.
rkennke@46702 690 ParallelSPCleanupTask cleanup(1, &deflate_counters);
rkennke@46702 691 StrongRootsScope srs(1);
rkennke@46702 692 cleanup.work(0);
duke@1 693 }
duke@1 694
rkennke@46702 695 // Finish monitor deflation.
rkennke@46702 696 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
duke@1 697 }
duke@1 698
duke@1 699
duke@1 700 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
duke@1 701 switch(state) {
duke@1 702 case _thread_in_native:
duke@1 703 // native threads are safe if they have no java stack or have walkable stack
duke@1 704 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
duke@1 705
duke@1 706 // blocked threads should have already have walkable stack
duke@1 707 case _thread_blocked:
duke@1 708 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
duke@1 709 return true;
duke@1 710
duke@1 711 default:
duke@1 712 return false;
duke@1 713 }
duke@1 714 }
duke@1 715
duke@1 716
never@11637 717 // See if the thread is running inside a lazy critical native and
never@11637 718 // update the thread critical count if so. Also set a suspend flag to
never@11637 719 // cause the native wrapper to return into the JVM to do the unlock
never@11637 720 // once the native finishes.
never@11637 721 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
never@11637 722 if (state == _thread_in_native &&
never@11637 723 thread->has_last_Java_frame() &&
never@11637 724 thread->frame_anchor()->walkable()) {
never@11637 725 // This thread might be in a critical native nmethod so look at
never@11637 726 // the top of the stack and increment the critical count if it
never@11637 727 // is.
never@11637 728 frame wrapper_frame = thread->last_frame();
never@11637 729 CodeBlob* stub_cb = wrapper_frame.cb();
never@11637 730 if (stub_cb != NULL &&
never@11637 731 stub_cb->is_nmethod() &&
never@11637 732 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
never@11637 733 // A thread could potentially be in a critical native across
never@11637 734 // more than one safepoint, so only update the critical state on
never@11637 735 // the first one. When it returns it will perform the unlock.
never@11637 736 if (!thread->do_critical_native_unlock()) {
never@11637 737 #ifdef ASSERT
never@11637 738 if (!thread->in_critical()) {
david@35492 739 GCLocker::increment_debug_jni_lock_count();
never@11637 740 }
never@11637 741 #endif
never@11637 742 thread->enter_critical();
never@11637 743 // Make sure the native wrapper calls back on return to
never@11637 744 // perform the needed critical unlock.
never@11637 745 thread->set_critical_native_unlock();
never@11637 746 }
never@11637 747 }
never@11637 748 }
never@11637 749 }
never@11637 750
never@11637 751
never@11637 752
duke@1 753 // -------------------------------------------------------------------------------------------------------
duke@1 754 // Implementation of Safepoint callback point
duke@1 755
duke@1 756 void SafepointSynchronize::block(JavaThread *thread) {
duke@1 757 assert(thread != NULL, "thread must be set");
duke@1 758 assert(thread->is_Java_thread(), "not a Java thread");
duke@1 759
duke@1 760 // Threads shouldn't block if they are in the middle of printing, but...
duke@1 761 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
duke@1 762
duke@1 763 // Only bail from the block() call if the thread is gone from the
duke@1 764 // thread list; starting to exit should still block.
duke@1 765 if (thread->is_terminated()) {
duke@1 766 // block current thread if we come here from native code when VM is gone
duke@1 767 thread->block_if_vm_exited();
duke@1 768
duke@1 769 // otherwise do nothing
duke@1 770 return;
duke@1 771 }
duke@1 772
duke@1 773 JavaThreadState state = thread->thread_state();
duke@1 774 thread->frame_anchor()->make_walkable(thread);
duke@1 775
duke@1 776 // Check that we have a valid thread_state at this point
duke@1 777 switch(state) {
duke@1 778 case _thread_in_vm_trans:
duke@1 779 case _thread_in_Java: // From compiled code
duke@1 780
duke@1 781 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
duke@1 782 // we pretend we are still in the VM.
duke@1 783 thread->set_thread_state(_thread_in_vm);
duke@1 784
duke@1 785 if (is_synchronizing()) {
duke@1 786 Atomic::inc (&TryingToBlock) ;
duke@1 787 }
duke@1 788
duke@1 789 // We will always be holding the Safepoint_lock when we are examine the state
duke@1 790 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
duke@1 791 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
duke@1 792 Safepoint_lock->lock_without_safepoint_check();
duke@1 793 if (is_synchronizing()) {
duke@1 794 // Decrement the number of threads to wait for and signal vm thread
duke@1 795 assert(_waiting_to_block > 0, "sanity check");
duke@1 796 _waiting_to_block--;
duke@1 797 thread->safepoint_state()->set_has_called_back(true);
duke@1 798
never@12108 799 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
never@11631 800 if (thread->in_critical()) {
never@11631 801 // Notice that this thread is in a critical section
never@11631 802 increment_jni_active_count();
never@11631 803 }
never@11631 804
duke@1 805 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
duke@1 806 if (_waiting_to_block == 0) {
duke@1 807 Safepoint_lock->notify_all();
duke@1 808 }
duke@1 809 }
duke@1 810
duke@1 811 // We transition the thread to state _thread_blocked here, but
duke@1 812 // we can't do our usual check for external suspension and then
duke@1 813 // self-suspend after the lock_without_safepoint_check() call
duke@1 814 // below because we are often called during transitions while
duke@1 815 // we hold different locks. That would leave us suspended while
duke@1 816 // holding a resource which results in deadlocks.
duke@1 817 thread->set_thread_state(_thread_blocked);
duke@1 818 Safepoint_lock->unlock();
duke@1 819
duke@1 820 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
duke@1 821 // the entire safepoint, the threads will all line up here during the safepoint.
duke@1 822 Threads_lock->lock_without_safepoint_check();
duke@1 823 // restore original state. This is important if the thread comes from compiled code, so it
duke@1 824 // will continue to execute with the _thread_in_Java state.
duke@1 825 thread->set_thread_state(state);
duke@1 826 Threads_lock->unlock();
duke@1 827 break;
duke@1 828
duke@1 829 case _thread_in_native_trans:
duke@1 830 case _thread_blocked_trans:
duke@1 831 case _thread_new_trans:
duke@1 832 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
duke@1 833 thread->print_thread_state();
duke@1 834 fatal("Deadlock in safepoint code. "
duke@1 835 "Should have called back to the VM before blocking.");
duke@1 836 }
duke@1 837
duke@1 838 // We transition the thread to state _thread_blocked here, but
duke@1 839 // we can't do our usual check for external suspension and then
duke@1 840 // self-suspend after the lock_without_safepoint_check() call
duke@1 841 // below because we are often called during transitions while
duke@1 842 // we hold different locks. That would leave us suspended while
duke@1 843 // holding a resource which results in deadlocks.
duke@1 844 thread->set_thread_state(_thread_blocked);
duke@1 845
duke@1 846 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
duke@1 847 // the safepoint code might still be waiting for it to block. We need to change the state here,
duke@1 848 // so it can see that it is at a safepoint.
duke@1 849
duke@1 850 // Block until the safepoint operation is completed.
duke@1 851 Threads_lock->lock_without_safepoint_check();
duke@1 852
duke@1 853 // Restore state
duke@1 854 thread->set_thread_state(state);
duke@1 855
duke@1 856 Threads_lock->unlock();
duke@1 857 break;
duke@1 858
duke@1 859 default:
david@33105 860 fatal("Illegal threadstate encountered: %d", state);
duke@1 861 }
duke@1 862
duke@1 863 // Check for pending. async. exceptions or suspends - except if the
duke@1 864 // thread was blocked inside the VM. has_special_runtime_exit_condition()
duke@1 865 // is called last since it grabs a lock and we only want to do that when
duke@1 866 // we must.
duke@1 867 //
duke@1 868 // Note: we never deliver an async exception at a polling point as the
duke@1 869 // compiler may not have an exception handler for it. The polling
duke@1 870 // code will notice the async and deoptimize and the exception will
duke@1 871 // be delivered. (Polling at a return point is ok though). Sure is
duke@1 872 // a lot of bother for a deprecated feature...
duke@1 873 //
duke@1 874 // We don't deliver an async exception if the thread state is
duke@1 875 // _thread_in_native_trans so JNI functions won't be called with
duke@1 876 // a surprising pending exception. If the thread state is going back to java,
duke@1 877 // async exception is checked in check_special_condition_for_native_trans().
duke@1 878
duke@1 879 if (state != _thread_blocked_trans &&
duke@1 880 state != _thread_in_vm_trans &&
duke@1 881 thread->has_special_runtime_exit_condition()) {
duke@1 882 thread->handle_special_runtime_exit_condition(
duke@1 883 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
duke@1 884 }
duke@1 885 }
duke@1 886
duke@1 887 // ------------------------------------------------------------------------------------------------------
duke@1 888 // Exception handlers
duke@1 889
duke@1 890
duke@1 891 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
duke@1 892 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
duke@1 893 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
rehn@48069 894 if (!ThreadLocalHandshakes) {
rehn@48069 895 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
rehn@48069 896 }
duke@1 897
duke@1 898 if (ShowSafepointMsgs) {
duke@1 899 tty->print("handle_polling_page_exception: ");
duke@1 900 }
duke@1 901
duke@1 902 if (PrintSafepointStatistics) {
duke@1 903 inc_page_trap_count();
duke@1 904 }
duke@1 905
duke@1 906 ThreadSafepointState* state = thread->safepoint_state();
duke@1 907
duke@1 908 state->handle_polling_page_exception();
duke@1 909 }
duke@1 910
duke@1 911
duke@1 912 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
duke@1 913 if (!timeout_error_printed) {
duke@1 914 timeout_error_printed = true;
jwilhelm@22551 915 // Print out the thread info which didn't reach the safepoint for debugging
duke@1 916 // purposes (useful when there are lots of threads in the debugger).
drchase@24424 917 tty->cr();
duke@1 918 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
duke@1 919 if (reason == _spinning_timeout) {
duke@1 920 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
duke@1 921 } else if (reason == _blocking_timeout) {
duke@1 922 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
duke@1 923 }
duke@1 924
duke@1 925 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
duke@1 926 ThreadSafepointState *cur_state;
duke@1 927 ResourceMark rm;
dcubed@48321 928 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur_thread = jtiwh.next(); ) {
duke@1 929 cur_state = cur_thread->safepoint_state();
duke@1 930
duke@1 931 if (cur_thread->thread_state() != _thread_blocked &&
dcubed@48321 932 ((reason == _spinning_timeout && cur_state->is_running()) ||
duke@1 933 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
duke@1 934 tty->print("# ");
duke@1 935 cur_thread->print();
drchase@24424 936 tty->cr();
duke@1 937 }
duke@1 938 }
duke@1 939 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
duke@1 940 }
duke@1 941
duke@1 942 // To debug the long safepoint, specify both DieOnSafepointTimeout &
duke@1 943 // ShowMessageBoxOnError.
duke@1 944 if (DieOnSafepointTimeout) {
david@33105 945 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
rehn@46496 946 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
duke@1 947 }
duke@1 948 }
duke@1 949
duke@1 950
duke@1 951 // -------------------------------------------------------------------------------------------------------
duke@1 952 // Implementation of ThreadSafepointState
duke@1 953
duke@1 954 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
duke@1 955 _thread = thread;
duke@1 956 _type = _running;
duke@1 957 _has_called_back = false;
duke@1 958 _at_poll_safepoint = false;
duke@1 959 }
duke@1 960
duke@1 961 void ThreadSafepointState::create(JavaThread *thread) {
duke@1 962 ThreadSafepointState *state = new ThreadSafepointState(thread);
duke@1 963 thread->set_safepoint_state(state);
duke@1 964 }
duke@1 965
duke@1 966 void ThreadSafepointState::destroy(JavaThread *thread) {
duke@1 967 if (thread->safepoint_state()) {
duke@1 968 delete(thread->safepoint_state());
duke@1 969 thread->set_safepoint_state(NULL);
duke@1 970 }
duke@1 971 }
duke@1 972
duke@1 973 void ThreadSafepointState::examine_state_of_thread() {
duke@1 974 assert(is_running(), "better be running or just have hit safepoint poll");
duke@1 975
duke@1 976 JavaThreadState state = _thread->thread_state();
duke@1 977
never@6269 978 // Save the state at the start of safepoint processing.
never@6269 979 _orig_thread_state = state;
never@6269 980
duke@1 981 // Check for a thread that is suspended. Note that thread resume tries
duke@1 982 // to grab the Threads_lock which we own here, so a thread cannot be
duke@1 983 // resumed during safepoint synchronization.
duke@1 984
dcubed@3826 985 // We check to see if this thread is suspended without locking to
dcubed@3826 986 // avoid deadlocking with a third thread that is waiting for this
dcubed@3826 987 // thread to be suspended. The third thread can notice the safepoint
dcubed@3826 988 // that we're trying to start at the beginning of its SR_lock->wait()
dcubed@3826 989 // call. If that happens, then the third thread will block on the
dcubed@3826 990 // safepoint while still holding the underlying SR_lock. We won't be
dcubed@3826 991 // able to get the SR_lock and we'll deadlock.
dcubed@3826 992 //
dcubed@3826 993 // We don't need to grab the SR_lock here for two reasons:
dcubed@3826 994 // 1) The suspend flags are both volatile and are set with an
dcubed@3826 995 // Atomic::cmpxchg() call so we should see the suspended
dcubed@3826 996 // state right away.
dcubed@3826 997 // 2) We're being called from the safepoint polling loop; if
dcubed@3826 998 // we don't see the suspended state on this iteration, then
dcubed@3826 999 // we'll come around again.
dcubed@3826 1000 //
dcubed@3826 1001 bool is_suspended = _thread->is_ext_suspended();
duke@1 1002 if (is_suspended) {
duke@1 1003 roll_forward(_at_safepoint);
duke@1 1004 return;
duke@1 1005 }
duke@1 1006
duke@1 1007 // Some JavaThread states have an initial safepoint state of
duke@1 1008 // running, but are actually at a safepoint. We will happily
duke@1 1009 // agree and update the safepoint state here.
duke@1 1010 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
never@12108 1011 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
never@11631 1012 roll_forward(_at_safepoint);
never@11631 1013 return;
duke@1 1014 }
duke@1 1015
duke@1 1016 if (state == _thread_in_vm) {
duke@1 1017 roll_forward(_call_back);
duke@1 1018 return;
duke@1 1019 }
duke@1 1020
duke@1 1021 // All other thread states will continue to run until they
duke@1 1022 // transition and self-block in state _blocked
duke@1 1023 // Safepoint polling in compiled code causes the Java threads to do the same.
duke@1 1024 // Note: new threads may require a malloc so they must be allowed to finish
duke@1 1025
duke@1 1026 assert(is_running(), "examine_state_of_thread on non-running thread");
duke@1 1027 return;
duke@1 1028 }
duke@1 1029
duke@1 1030 // Returns true is thread could not be rolled forward at present position.
duke@1 1031 void ThreadSafepointState::roll_forward(suspend_type type) {
duke@1 1032 _type = type;
duke@1 1033
duke@1 1034 switch(_type) {
duke@1 1035 case _at_safepoint:
duke@1 1036 SafepointSynchronize::signal_thread_at_safepoint();
never@12108 1037 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
never@12108 1038 if (_thread->in_critical()) {
never@12108 1039 // Notice that this thread is in a critical section
never@12108 1040 SafepointSynchronize::increment_jni_active_count();
never@12108 1041 }
duke@1 1042 break;
duke@1 1043
duke@1 1044 case _call_back:
duke@1 1045 set_has_called_back(false);
duke@1 1046 break;
duke@1 1047
duke@1 1048 case _running:
duke@1 1049 default:
duke@1 1050 ShouldNotReachHere();
duke@1 1051 }
duke@1 1052 }
duke@1 1053
duke@1 1054 void ThreadSafepointState::restart() {
duke@1 1055 switch(type()) {
duke@1 1056 case _at_safepoint:
duke@1 1057 case _call_back:
duke@1 1058 break;
duke@1 1059
duke@1 1060 case _running:
duke@1 1061 default:
bpittore@31592 1062 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
david@33148 1063 p2i(_thread), _type);
duke@1 1064 _thread->print();
duke@1 1065 ShouldNotReachHere();
duke@1 1066 }
duke@1 1067 _type = _running;
duke@1 1068 set_has_called_back(false);
duke@1 1069 }
duke@1 1070
duke@1 1071
duke@1 1072 void ThreadSafepointState::print_on(outputStream *st) const {
goetz@33589 1073 const char *s = NULL;
duke@1 1074
duke@1 1075 switch(_type) {
duke@1 1076 case _running : s = "_running"; break;
duke@1 1077 case _at_safepoint : s = "_at_safepoint"; break;
duke@1 1078 case _call_back : s = "_call_back"; break;
duke@1 1079 default:
duke@1 1080 ShouldNotReachHere();
duke@1 1081 }
duke@1 1082
duke@1 1083 st->print_cr("Thread: " INTPTR_FORMAT
duke@1 1084 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
david@33148 1085 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
duke@1 1086 _at_poll_safepoint);
duke@1 1087
duke@1 1088 _thread->print_thread_state_on(st);
duke@1 1089 }
duke@1 1090
duke@1 1091 // ---------------------------------------------------------------------------------------------------------------------
duke@1 1092
rehn@48069 1093 // Block the thread at poll or poll return for safepoint/handshake.
duke@1 1094 void ThreadSafepointState::handle_polling_page_exception() {
duke@1 1095
duke@1 1096 // Check state. block() will set thread state to thread_in_vm which will
duke@1 1097 // cause the safepoint state _type to become _call_back.
rehn@48069 1098 suspend_type t = type();
rehn@48069 1099 assert(!SafepointMechanism::uses_global_page_poll() || t == ThreadSafepointState::_running,
rehn@48069 1100 "polling page exception on thread not running state: %u", uint(t));
duke@1 1101
duke@1 1102 // Step 1: Find the nmethod from the return address
duke@1 1103 if (ShowSafepointMsgs && Verbose) {
david@33148 1104 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
duke@1 1105 }
duke@1 1106 address real_return_addr = thread()->saved_exception_pc();
duke@1 1107
duke@1 1108 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
rbackman@38133 1109 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
rbackman@38133 1110 CompiledMethod* nm = (CompiledMethod*)cb;
duke@1 1111
duke@1 1112 // Find frame of caller
duke@1 1113 frame stub_fr = thread()->last_frame();
duke@1 1114 CodeBlob* stub_cb = stub_fr.cb();
duke@1 1115 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
duke@1 1116 RegisterMap map(thread(), true);
duke@1 1117 frame caller_fr = stub_fr.sender(&map);
duke@1 1118
duke@1 1119 // Should only be poll_return or poll
duke@1 1120 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
duke@1 1121
duke@1 1122 // This is a poll immediately before a return. The exception handling code
duke@1 1123 // has already had the effect of causing the return to occur, so the execution
duke@1 1124 // will continue immediately after the call. In addition, the oopmap at the
duke@1 1125 // return point does not mark the return value as an oop (if it is), so
duke@1 1126 // it needs a handle here to be updated.
duke@1 1127 if( nm->is_at_poll_return(real_return_addr) ) {
duke@1 1128 // See if return type is an oop.
duke@1 1129 bool return_oop = nm->method()->is_returning_oop();
duke@1 1130 Handle return_value;
duke@1 1131 if (return_oop) {
duke@1 1132 // The oop result has been saved on the stack together with all
duke@1 1133 // the other registers. In order to preserve it over GCs we need
duke@1 1134 // to keep it in a handle.
duke@1 1135 oop result = caller_fr.saved_oop_result(&map);
coleenp@46968 1136 assert(oopDesc::is_oop_or_null(result), "must be oop");
duke@1 1137 return_value = Handle(thread(), result);
duke@1 1138 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
duke@1 1139 }
duke@1 1140
duke@1 1141 // Block the thread
rehn@48069 1142 SafepointMechanism::block_if_requested(thread());
duke@1 1143
duke@1 1144 // restore oop result, if any
duke@1 1145 if (return_oop) {
duke@1 1146 caller_fr.set_saved_oop_result(&map, return_value());
duke@1 1147 }
duke@1 1148 }
duke@1 1149
duke@1 1150 // This is a safepoint poll. Verify the return address and block.
duke@1 1151 else {
duke@1 1152 set_at_poll_safepoint(true);
duke@1 1153
duke@1 1154 // verify the blob built the "return address" correctly
duke@1 1155 assert(real_return_addr == caller_fr.pc(), "must match");
duke@1 1156
duke@1 1157 // Block the thread
rehn@48069 1158 SafepointMechanism::block_if_requested(thread());
duke@1 1159 set_at_poll_safepoint(false);
duke@1 1160
duke@1 1161 // If we have a pending async exception deoptimize the frame
duke@1 1162 // as otherwise we may never deliver it.
duke@1 1163 if (thread()->has_async_condition()) {
duke@1 1164 ThreadInVMfromJavaNoAsyncException __tiv(thread());
never@7106 1165 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
duke@1 1166 }
duke@1 1167
duke@1 1168 // If an exception has been installed we must check for a pending deoptimization
duke@1 1169 // Deoptimize frame if exception has been thrown.
duke@1 1170
duke@1 1171 if (thread()->has_pending_exception() ) {
duke@1 1172 RegisterMap map(thread(), true);
duke@1 1173 frame caller_fr = stub_fr.sender(&map);
duke@1 1174 if (caller_fr.is_deoptimized_frame()) {
duke@1 1175 // The exception patch will destroy registers that are still
duke@1 1176 // live and will be needed during deoptimization. Defer the
jwilhelm@22551 1177 // Async exception should have deferred the exception until the
duke@1 1178 // next safepoint which will be detected when we get into
duke@1 1179 // the interpreter so if we have an exception now things
duke@1 1180 // are messed up.
duke@1 1181
duke@1 1182 fatal("Exception installed and deoptimization is pending");
duke@1 1183 }
duke@1 1184 }
duke@1 1185 }
duke@1 1186 }
duke@1 1187
duke@1 1188
duke@1 1189 //
duke@1 1190 // Statistics & Instrumentations
duke@1 1191 //
duke@1 1192 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
xlu@5042 1193 jlong SafepointSynchronize::_safepoint_begin_time = 0;
duke@1 1194 int SafepointSynchronize::_cur_stat_index = 0;
duke@1 1195 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
duke@1 1196 julong SafepointSynchronize::_coalesced_vmop_count = 0;
duke@1 1197 jlong SafepointSynchronize::_max_sync_time = 0;
xlu@5042 1198 jlong SafepointSynchronize::_max_vmop_time = 0;
xlu@5042 1199 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
duke@1 1200
xlu@5042 1201 static jlong cleanup_end_time = 0;
duke@1 1202 static bool need_to_track_page_armed_status = false;
duke@1 1203 static bool init_done = false;
duke@1 1204
xlu@5042 1205 // Helper method to print the header.
xlu@5042 1206 static void print_header() {
shade@46473 1207 // The number of spaces is significant here, and should match the format
shade@46473 1208 // specifiers in print_statistics().
shade@46473 1209
shade@46473 1210 tty->print(" vmop "
shade@46473 1211 "[ threads: total initially_running wait_to_block ]"
shade@46473 1212 "[ time: spin block sync cleanup vmop ] ");
xlu@5042 1213
xlu@5042 1214 // no page armed status printed out if it is always armed.
xlu@5042 1215 if (need_to_track_page_armed_status) {
xlu@5042 1216 tty->print("page_armed ");
xlu@5042 1217 }
xlu@5042 1218
xlu@5042 1219 tty->print_cr("page_trap_count");
xlu@5042 1220 }
xlu@5042 1221
duke@1 1222 void SafepointSynchronize::deferred_initialize_stat() {
duke@1 1223 if (init_done) return;
duke@1 1224
duke@1 1225 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
duke@1 1226 // be printed right away, in which case, _safepoint_stats will regress to
duke@1 1227 // a single element array. Otherwise, it is a circular ring buffer with default
duke@1 1228 // size of PrintSafepointStatisticsCount.
duke@1 1229 int stats_array_size;
duke@1 1230 if (PrintSafepointStatisticsTimeout > 0) {
duke@1 1231 stats_array_size = 1;
duke@1 1232 PrintSafepointStatistics = true;
duke@1 1233 } else {
duke@1 1234 stats_array_size = PrintSafepointStatisticsCount;
duke@1 1235 }
duke@1 1236 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
zgu@13195 1237 * sizeof(SafepointStats), mtInternal);
duke@1 1238 guarantee(_safepoint_stats != NULL,
duke@1 1239 "not enough memory for safepoint instrumentation data");
duke@1 1240
shade@27662 1241 if (DeferPollingPageLoopCount >= 0) {
duke@1 1242 need_to_track_page_armed_status = true;
duke@1 1243 }
duke@1 1244 init_done = true;
duke@1 1245 }
duke@1 1246
duke@1 1247 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
xlu@4006 1248 assert(init_done, "safepoint statistics array hasn't been initialized");
duke@1 1249 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1250
xlu@5042 1251 spstat->_time_stamp = _ts_of_current_safepoint;
xlu@5042 1252
duke@1 1253 VM_Operation *op = VMThread::vm_operation();
duke@1 1254 spstat->_vmop_type = (op != NULL ? op->type() : -1);
duke@1 1255 if (op != NULL) {
duke@1 1256 _safepoint_reasons[spstat->_vmop_type]++;
duke@1 1257 }
duke@1 1258
duke@1 1259 spstat->_nof_total_threads = nof_threads;
duke@1 1260 spstat->_nof_initial_running_threads = nof_running;
duke@1 1261 spstat->_nof_threads_hit_page_trap = 0;
duke@1 1262
duke@1 1263 // Records the start time of spinning. The real time spent on spinning
duke@1 1264 // will be adjusted when spin is done. Same trick is applied for time
duke@1 1265 // spent on waiting for threads to block.
duke@1 1266 if (nof_running != 0) {
duke@1 1267 spstat->_time_to_spin = os::javaTimeNanos();
duke@1 1268 } else {
duke@1 1269 spstat->_time_to_spin = 0;
duke@1 1270 }
duke@1 1271 }
duke@1 1272
duke@1 1273 void SafepointSynchronize::update_statistics_on_spin_end() {
duke@1 1274 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1275
duke@1 1276 jlong cur_time = os::javaTimeNanos();
duke@1 1277
duke@1 1278 spstat->_nof_threads_wait_to_block = _waiting_to_block;
duke@1 1279 if (spstat->_nof_initial_running_threads != 0) {
duke@1 1280 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
duke@1 1281 }
duke@1 1282
duke@1 1283 if (need_to_track_page_armed_status) {
duke@1 1284 spstat->_page_armed = (PageArmed == 1);
duke@1 1285 }
duke@1 1286
duke@1 1287 // Records the start time of waiting for to block. Updated when block is done.
duke@1 1288 if (_waiting_to_block != 0) {
duke@1 1289 spstat->_time_to_wait_to_block = cur_time;
duke@1 1290 } else {
duke@1 1291 spstat->_time_to_wait_to_block = 0;
duke@1 1292 }
duke@1 1293 }
duke@1 1294
duke@1 1295 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
duke@1 1296 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1297
duke@1 1298 if (spstat->_nof_threads_wait_to_block != 0) {
duke@1 1299 spstat->_time_to_wait_to_block = end_time -
duke@1 1300 spstat->_time_to_wait_to_block;
duke@1 1301 }
duke@1 1302
duke@1 1303 // Records the end time of sync which will be used to calculate the total
duke@1 1304 // vm operation time. Again, the real time spending in syncing will be deducted
duke@1 1305 // from the start of the sync time later when end_statistics is called.
xlu@5042 1306 spstat->_time_to_sync = end_time - _safepoint_begin_time;
duke@1 1307 if (spstat->_time_to_sync > _max_sync_time) {
duke@1 1308 _max_sync_time = spstat->_time_to_sync;
duke@1 1309 }
xlu@5042 1310
xlu@5042 1311 spstat->_time_to_do_cleanups = end_time;
xlu@5042 1312 }
xlu@5042 1313
xlu@5042 1314 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
xlu@5042 1315 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
xlu@5042 1316
xlu@5042 1317 // Record how long spent in cleanup tasks.
xlu@5042 1318 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
xlu@5042 1319
xlu@5042 1320 cleanup_end_time = end_time;
duke@1 1321 }
duke@1 1322
duke@1 1323 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
duke@1 1324 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1325
duke@1 1326 // Update the vm operation time.
xlu@5042 1327 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
xlu@5042 1328 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
xlu@5042 1329 _max_vmop_time = spstat->_time_to_exec_vmop;
xlu@5042 1330 }
duke@1 1331 // Only the sync time longer than the specified
duke@1 1332 // PrintSafepointStatisticsTimeout will be printed out right away.
duke@1 1333 // By default, it is -1 meaning all samples will be put into the list.
duke@1 1334 if ( PrintSafepointStatisticsTimeout > 0) {
gziemski@33222 1335 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1336 print_statistics();
duke@1 1337 }
duke@1 1338 } else {
duke@1 1339 // The safepoint statistics will be printed out when the _safepoin_stats
duke@1 1340 // array fills up.
xlu@5042 1341 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
duke@1 1342 print_statistics();
duke@1 1343 _cur_stat_index = 0;
xlu@5042 1344 } else {
xlu@5042 1345 _cur_stat_index++;
duke@1 1346 }
duke@1 1347 }
duke@1 1348 }
duke@1 1349
duke@1 1350 void SafepointSynchronize::print_statistics() {
xlu@5042 1351 for (int index = 0; index <= _cur_stat_index; index++) {
xlu@5042 1352 if (index % 30 == 0) {
xlu@5042 1353 print_header();
xlu@5042 1354 }
shade@46473 1355 SafepointStats* sstats = &_safepoint_stats[index];
shade@46473 1356 tty->print("%8.3f: ", sstats->_time_stamp);
shade@46473 1357 tty->print("%-30s [ "
shade@46473 1358 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
shade@46473 1359 "]",
shade@46473 1360 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
duke@1 1361 sstats->_nof_total_threads,
duke@1 1362 sstats->_nof_initial_running_threads,
duke@1 1363 sstats->_nof_threads_wait_to_block);
duke@1 1364 // "/ MICROUNITS " is to convert the unit from nanos to millis.
shade@46473 1365 tty->print("[ "
shade@46473 1366 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
shade@46473 1367 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
shade@46473 1368 INT64_FORMAT_W(7) " ] ",
jwilhelm@46630 1369 (int64_t)(sstats->_time_to_spin / MICROUNITS),
jwilhelm@46630 1370 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
jwilhelm@46630 1371 (int64_t)(sstats->_time_to_sync / MICROUNITS),
jwilhelm@46630 1372 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
jwilhelm@46630 1373 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
duke@1 1374
duke@1 1375 if (need_to_track_page_armed_status) {
shade@46473 1376 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
duke@1 1377 }
shade@46473 1378 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
duke@1 1379 }
duke@1 1380 }
duke@1 1381
duke@1 1382 // This method will be called when VM exits. It will first call
duke@1 1383 // print_statistics to print out the rest of the sampling. Then
duke@1 1384 // it tries to summarize the sampling.
duke@1 1385 void SafepointSynchronize::print_stat_on_exit() {
duke@1 1386 if (_safepoint_stats == NULL) return;
duke@1 1387
duke@1 1388 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1389
duke@1 1390 // During VM exit, end_statistics may not get called and in that
duke@1 1391 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
duke@1 1392 // don't print it out.
duke@1 1393 // Approximate the vm op time.
duke@1 1394 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
xlu@5042 1395 os::javaTimeNanos() - cleanup_end_time;
duke@1 1396
duke@1 1397 if ( PrintSafepointStatisticsTimeout < 0 ||
gziemski@33222 1398 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1399 print_statistics();
duke@1 1400 }
drchase@24424 1401 tty->cr();
duke@1 1402
duke@1 1403 // Print out polling page sampling status.
duke@1 1404 if (!need_to_track_page_armed_status) {
shade@27662 1405 tty->print_cr("Polling page always armed");
duke@1 1406 } else {
david@33148 1407 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
david@33148 1408 DeferPollingPageLoopCount);
duke@1 1409 }
duke@1 1410
duke@1 1411 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
duke@1 1412 if (_safepoint_reasons[index] != 0) {
bpittore@31592 1413 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
duke@1 1414 _safepoint_reasons[index]);
duke@1 1415 }
duke@1 1416 }
duke@1 1417
bpittore@31592 1418 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
duke@1 1419 _coalesced_vmop_count);
bpittore@31592 1420 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
jwilhelm@46630 1421 (int64_t)(_max_sync_time / MICROUNITS));
xlu@5042 1422 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
bpittore@31592 1423 INT64_FORMAT_W(5) " ms",
jwilhelm@46630 1424 (int64_t)(_max_vmop_time / MICROUNITS));
duke@1 1425 }
duke@1 1426
duke@1 1427 // ------------------------------------------------------------------------------------------------
duke@1 1428 // Non-product code
duke@1 1429
duke@1 1430 #ifndef PRODUCT
duke@1 1431
duke@1 1432 void SafepointSynchronize::print_state() {
duke@1 1433 if (_state == _not_synchronized) {
duke@1 1434 tty->print_cr("not synchronized");
duke@1 1435 } else if (_state == _synchronizing || _state == _synchronized) {
duke@1 1436 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
duke@1 1437 "synchronized");
duke@1 1438
dcubed@48321 1439 for (JavaThreadIteratorWithHandle jtiwh; JavaThread *cur = jtiwh.next(); ) {
duke@1 1440 cur->safepoint_state()->print();
duke@1 1441 }
duke@1 1442 }
duke@1 1443 }
duke@1 1444
duke@1 1445 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
duke@1 1446 if (ShowSafepointMsgs) {
duke@1 1447 va_list ap;
duke@1 1448 va_start(ap, format);
duke@1 1449 tty->vprint_cr(format, ap);
duke@1 1450 va_end(ap);
duke@1 1451 }
duke@1 1452 }
duke@1 1453
duke@1 1454 #endif // !PRODUCT