annotate src/hotspot/share/runtime/safepoint.cpp @ 48069:0ce0ac68ace7

8189941: Implementation JEP 312: Thread-local handshake Summary: Introduce a way to execute a callback on threads without performing a global VM safepoint. Make it both possible and cheap to stop individual threads and not just all threads or none. Reviewed-by: mdoerr, neliasso, acorn, aph, coleenp, dholmes Contributed-by: mikael.gerdin@oracle.com, erik.osterlund@oracle.com, robbin.ehn@oracle.com
author rehn
date Thu, 31 Aug 2017 10:00:28 +0200
parents 69c081ca110a
children 8d15b1369c7a
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"
rehn@37161 62 #include "runtime/timerTrace.hpp"
stefank@7397 63 #include "services/runtimeService.hpp"
dsimms@37176 64 #include "trace/tracing.hpp"
dsimms@37176 65 #include "trace/traceMacros.hpp"
stefank@7397 66 #include "utilities/events.hpp"
jprovino@15482 67 #include "utilities/macros.hpp"
stefank@7397 68 #ifdef COMPILER1
stefank@7397 69 #include "c1/c1_globals.hpp"
stefank@7397 70 #endif
duke@1 71
duke@1 72 // --------------------------------------------------------------------------------------------------
duke@1 73 // Implementation of Safepoint begin/end
duke@1 74
duke@1 75 SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized;
duke@1 76 volatile int SafepointSynchronize::_waiting_to_block = 0;
duke@1 77 volatile int SafepointSynchronize::_safepoint_counter = 0;
never@11631 78 int SafepointSynchronize::_current_jni_active_count = 0;
xlu@5042 79 long SafepointSynchronize::_end_of_last_safepoint = 0;
duke@1 80 static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE
duke@1 81 static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only
duke@1 82 static bool timeout_error_printed = false;
duke@1 83
duke@1 84 // Roll all threads forward to a safepoint and suspend them all
duke@1 85 void SafepointSynchronize::begin() {
dsimms@37176 86 EventSafepointBegin begin_event;
duke@1 87 Thread* myThread = Thread::current();
duke@1 88 assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint");
duke@1 89
xlu@5042 90 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@5042 91 _safepoint_begin_time = os::javaTimeNanos();
xlu@5042 92 _ts_of_current_safepoint = tty->time_stamp().seconds();
xlu@5042 93 }
duke@1 94
eosterlund@47791 95 Universe::heap()->safepoint_synchronize_begin();
duke@1 96
duke@1 97 // By getting the Threads_lock, we assure that no threads are about to start or
duke@1 98 // exit. It is released again in SafepointSynchronize::end().
duke@1 99 Threads_lock->lock();
duke@1 100
duke@1 101 assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state");
duke@1 102
duke@1 103 int nof_threads = Threads::number_of_threads();
duke@1 104
rprotacio@33763 105 log_debug(safepoint)("Safepoint synchronization initiated. (%d)", nof_threads);
duke@1 106
duke@1 107 RuntimeService::record_safepoint_begin();
duke@1 108
duke@1 109 MutexLocker mu(Safepoint_lock);
duke@1 110
never@11631 111 // Reset the count of active JNI critical threads
never@11631 112 _current_jni_active_count = 0;
never@11631 113
duke@1 114 // Set number of threads to wait for, before we initiate the callbacks
duke@1 115 _waiting_to_block = nof_threads;
duke@1 116 TryingToBlock = 0 ;
duke@1 117 int still_running = nof_threads;
duke@1 118
duke@1 119 // Save the starting time, so that it can be compared to see if this has taken
duke@1 120 // too long to complete.
goetz@33589 121 jlong safepoint_limit_time = 0;
duke@1 122 timeout_error_printed = false;
duke@1 123
xlu@4006 124 // PrintSafepointStatisticsTimeout can be specified separately. When
xlu@4006 125 // specified, PrintSafepointStatistics will be set to true in
xlu@4006 126 // deferred_initialize_stat method. The initialization has to be done
xlu@4006 127 // early enough to avoid any races. See bug 6880029 for details.
xlu@4006 128 if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) {
xlu@4006 129 deferred_initialize_stat();
xlu@4006 130 }
xlu@4006 131
duke@1 132 // Begin the process of bringing the system to a safepoint.
duke@1 133 // Java threads can be in several different states and are
duke@1 134 // stopped by different mechanisms:
duke@1 135 //
duke@1 136 // 1. Running interpreted
jwilhelm@22551 137 // The interpreter dispatch table is changed to force it to
duke@1 138 // check for a safepoint condition between bytecodes.
duke@1 139 // 2. Running in native code
duke@1 140 // When returning from the native code, a Java thread must check
duke@1 141 // the safepoint _state to see if we must block. If the
duke@1 142 // VM thread sees a Java thread in native, it does
duke@1 143 // not wait for this thread to block. The order of the memory
duke@1 144 // writes and reads of both the safepoint state and the Java
duke@1 145 // threads state is critical. In order to guarantee that the
duke@1 146 // memory writes are serialized with respect to each other,
duke@1 147 // the VM thread issues a memory barrier instruction
duke@1 148 // (on MP systems). In order to avoid the overhead of issuing
duke@1 149 // a memory barrier for each Java thread making native calls, each Java
duke@1 150 // thread performs a write to a single memory page after changing
duke@1 151 // the thread state. The VM thread performs a sequence of
duke@1 152 // mprotect OS calls which forces all previous writes from all
duke@1 153 // Java threads to be serialized. This is done in the
duke@1 154 // os::serialize_thread_states() call. This has proven to be
duke@1 155 // much more efficient than executing a membar instruction
duke@1 156 // on every call to native code.
duke@1 157 // 3. Running compiled Code
duke@1 158 // Compiled code reads a global (Safepoint Polling) page that
duke@1 159 // is set to fault if we are trying to get to a safepoint.
duke@1 160 // 4. Blocked
duke@1 161 // A thread which is blocked will not be allowed to return from the
duke@1 162 // block condition until the safepoint operation is complete.
duke@1 163 // 5. In VM or Transitioning between states
duke@1 164 // If a Java thread is currently running in the VM or transitioning
duke@1 165 // between states, the safepointing code will wait for the thread to
duke@1 166 // block itself when it attempts transitions to a new state.
duke@1 167 //
dsimms@37176 168 {
egahlin@40664 169 EventSafepointStateSynchronization sync_event;
dsimms@37176 170 int initial_running = 0;
duke@1 171
dsimms@37176 172 _state = _synchronizing;
rehn@48069 173
rehn@48069 174 if (SafepointMechanism::uses_thread_local_poll()) {
rehn@48069 175 // Arming the per thread poll while having _state != _not_synchronized means safepointing
rehn@48069 176 log_trace(safepoint)("Setting thread local yield flag for threads");
rehn@48069 177 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
rehn@48069 178 // Make sure the threads start polling, it is time to yield.
rehn@48069 179 SafepointMechanism::arm_local_poll(cur); // release store, global state -> local state
rehn@48069 180 }
rehn@48069 181 }
rehn@48069 182 OrderAccess::fence(); // storestore|storeload, global state -> local state
duke@1 183
dsimms@37176 184 // Flush all thread states to memory
dsimms@37176 185 if (!UseMembar) {
dsimms@37176 186 os::serialize_thread_states();
dsimms@37176 187 }
duke@1 188
rehn@48069 189 if (SafepointMechanism::uses_global_page_poll()) {
rehn@48069 190 // Make interpreter safepoint aware
rehn@48069 191 Interpreter::notice_safepoints();
duke@1 192
rehn@48069 193 if (DeferPollingPageLoopCount < 0) {
rehn@48069 194 // Make polling safepoint aware
rehn@48069 195 guarantee (PageArmed == 0, "invariant") ;
rehn@48069 196 PageArmed = 1 ;
rehn@48069 197 os::make_polling_page_unreadable();
rehn@48069 198 }
dsimms@37176 199 }
dsimms@37176 200
dsimms@37176 201 // Consider using active_processor_count() ... but that call is expensive.
dsimms@37176 202 int ncpus = os::processor_count() ;
duke@1 203
duke@1 204 #ifdef ASSERT
dsimms@37176 205 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
dsimms@37176 206 assert(cur->safepoint_state()->is_running(), "Illegal initial state");
dsimms@37176 207 // Clear the visited flag to ensure that the critical counts are collected properly.
dsimms@37176 208 cur->set_visited_for_critical_count(false);
dsimms@37176 209 }
duke@1 210 #endif // ASSERT
duke@1 211
dsimms@37176 212 if (SafepointTimeout)
dsimms@37176 213 safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS;
duke@1 214
dsimms@37176 215 // Iterate through all threads until it have been determined how to stop them all at a safepoint
dsimms@37176 216 unsigned int iterations = 0;
dsimms@37176 217 int steps = 0 ;
dsimms@37176 218 while(still_running > 0) {
dsimms@37176 219 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
dsimms@37176 220 assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended");
dsimms@37176 221 ThreadSafepointState *cur_state = cur->safepoint_state();
dsimms@37176 222 if (cur_state->is_running()) {
dsimms@37176 223 cur_state->examine_state_of_thread();
dsimms@37176 224 if (!cur_state->is_running()) {
dsimms@37176 225 still_running--;
dsimms@37176 226 // consider adjusting steps downward:
dsimms@37176 227 // steps = 0
dsimms@37176 228 // steps -= NNN
dsimms@37176 229 // steps >>= 1
dsimms@37176 230 // steps = MIN(steps, 2000-100)
dsimms@37176 231 // if (iterations != 0) steps -= NNN
dsimms@37176 232 }
stuefe@46701 233 LogTarget(Trace, safepoint) lt;
stuefe@46701 234 if (lt.is_enabled()) {
dsimms@37176 235 ResourceMark rm;
stuefe@46701 236 LogStream ls(lt);
stuefe@46701 237 cur_state->print_on(&ls);
dsimms@37176 238 }
duke@1 239 }
dsimms@37176 240 }
dsimms@37176 241
dsimms@37176 242 if (iterations == 0) {
dsimms@37176 243 initial_running = still_running;
dsimms@37176 244 if (PrintSafepointStatistics) {
dsimms@37176 245 begin_statistics(nof_threads, still_running);
dsimms@37176 246 }
dsimms@37176 247 }
dsimms@37176 248
dsimms@37176 249 if (still_running > 0) {
dsimms@37176 250 // Check for if it takes to long
dsimms@37176 251 if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) {
dsimms@37176 252 print_safepoint_timeout(_spinning_timeout);
dsimms@37176 253 }
dsimms@37176 254
dsimms@37176 255 // Spin to avoid context switching.
dsimms@37176 256 // There's a tension between allowing the mutators to run (and rendezvous)
dsimms@37176 257 // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that
dsimms@37176 258 // a mutator might otherwise use profitably to reach a safepoint. Excessive
dsimms@37176 259 // spinning by the VM thread on a saturated system can increase rendezvous latency.
dsimms@37176 260 // Blocking or yielding incur their own penalties in the form of context switching
dsimms@37176 261 // and the resultant loss of $ residency.
dsimms@37176 262 //
dsimms@37176 263 // Further complicating matters is that yield() does not work as naively expected
dsimms@37176 264 // on many platforms -- yield() does not guarantee that any other ready threads
dsimms@37176 265 // will run. As such we revert to naked_short_sleep() after some number of iterations.
dsimms@37176 266 // nakes_short_sleep() is implemented as a short unconditional sleep.
dsimms@37176 267 // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping
dsimms@37176 268 // can actually increase the time it takes the VM thread to detect that a system-wide
dsimms@37176 269 // stop-the-world safepoint has been reached. In a pathological scenario such as that
dsimms@37176 270 // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe.
dsimms@37176 271 // In that case the mutators will be stalled waiting for the safepoint to complete and the
dsimms@37176 272 // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread
dsimms@37176 273 // will eventually wake up and detect that all mutators are safe, at which point
dsimms@37176 274 // we'll again make progress.
dsimms@37176 275 //
dsimms@37176 276 // Beware too that that the VMThread typically runs at elevated priority.
dsimms@37176 277 // Its default priority is higher than the default mutator priority.
dsimms@37176 278 // Obviously, this complicates spinning.
dsimms@37176 279 //
dsimms@37176 280 // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0).
dsimms@37176 281 // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will.
dsimms@37176 282 //
dsimms@37176 283 // See the comments in synchronizer.cpp for additional remarks on spinning.
dsimms@37176 284 //
dsimms@37176 285 // In the future we might:
dsimms@37176 286 // 1. Modify the safepoint scheme to avoid potentially unbounded spinning.
dsimms@37176 287 // This is tricky as the path used by a thread exiting the JVM (say on
dsimms@37176 288 // on JNI call-out) simply stores into its state field. The burden
dsimms@37176 289 // is placed on the VM thread, which must poll (spin).
dsimms@37176 290 // 2. Find something useful to do while spinning. If the safepoint is GC-related
dsimms@37176 291 // we might aggressively scan the stacks of threads that are already safe.
dsimms@37176 292 // 3. Use Solaris schedctl to examine the state of the still-running mutators.
dsimms@37176 293 // If all the mutators are ONPROC there's no reason to sleep or yield.
dsimms@37176 294 // 4. YieldTo() any still-running mutators that are ready but OFFPROC.
dsimms@37176 295 // 5. Check system saturation. If the system is not fully saturated then
dsimms@37176 296 // simply spin and avoid sleep/yield.
dsimms@37176 297 // 6. As still-running mutators rendezvous they could unpark the sleeping
dsimms@37176 298 // VMthread. This works well for still-running mutators that become
dsimms@37176 299 // safe. The VMthread must still poll for mutators that call-out.
dsimms@37176 300 // 7. Drive the policy on time-since-begin instead of iterations.
dsimms@37176 301 // 8. Consider making the spin duration a function of the # of CPUs:
dsimms@37176 302 // Spin = (((ncpus-1) * M) + K) + F(still_running)
dsimms@37176 303 // Alternately, instead of counting iterations of the outer loop
dsimms@37176 304 // we could count the # of threads visited in the inner loop, above.
dsimms@37176 305 // 9. On windows consider using the return value from SwitchThreadTo()
dsimms@37176 306 // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions.
dsimms@37176 307
rehn@48069 308 if (SafepointMechanism::uses_global_page_poll() && int(iterations) == DeferPollingPageLoopCount) {
dsimms@37176 309 guarantee (PageArmed == 0, "invariant") ;
dsimms@37176 310 PageArmed = 1 ;
dsimms@37176 311 os::make_polling_page_unreadable();
dsimms@37176 312 }
dsimms@37176 313
dsimms@37176 314 // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or
dsimms@37176 315 // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus)
dsimms@37176 316 ++steps ;
dsimms@37176 317 if (ncpus > 1 && steps < SafepointSpinBeforeYield) {
dsimms@37176 318 SpinPause() ; // MP-Polite spin
dsimms@37176 319 } else
dsimms@37176 320 if (steps < DeferThrSuspendLoopCount) {
dsimms@37176 321 os::naked_yield() ;
dsimms@37176 322 } else {
dsimms@37176 323 os::naked_short_sleep(1);
dsimms@37176 324 }
dsimms@37176 325
dsimms@37176 326 iterations ++ ;
dsimms@37176 327 }
dsimms@37176 328 assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long");
dsimms@37176 329 }
dsimms@37176 330 assert(still_running == 0, "sanity check");
dsimms@37176 331
dsimms@37176 332 if (PrintSafepointStatistics) {
dsimms@37176 333 update_statistics_on_spin_end();
dsimms@37176 334 }
dsimms@37176 335
dsimms@37176 336 if (sync_event.should_commit()) {
egahlin@47784 337 // Group this event together with the ones committed after the counter is increased
egahlin@47784 338 sync_event.set_safepointId(safepoint_counter() + 1);
dsimms@37176 339 sync_event.set_initialThreadCount(initial_running);
dsimms@37176 340 sync_event.set_runningThreadCount(_waiting_to_block);
dsimms@37176 341 sync_event.set_iterations(iterations);
dsimms@37176 342 sync_event.commit();
dsimms@37176 343 }
dsimms@37176 344 } //EventSafepointStateSync
dsimms@37176 345
dsimms@37176 346 // wait until all threads are stopped
dsimms@37176 347 {
dsimms@37176 348 EventSafepointWaitBlocked wait_blocked_event;
dsimms@37176 349 int initial_waiting_to_block = _waiting_to_block;
dsimms@37176 350
dsimms@37176 351 while (_waiting_to_block > 0) {
dsimms@37176 352 log_debug(safepoint)("Waiting for %d thread(s) to block", _waiting_to_block);
dsimms@37176 353 if (!SafepointTimeout || timeout_error_printed) {
dsimms@37176 354 Safepoint_lock->wait(true); // true, means with no safepoint checks
dsimms@37176 355 } else {
dsimms@37176 356 // Compute remaining time
dsimms@37176 357 jlong remaining_time = safepoint_limit_time - os::javaTimeNanos();
dsimms@37176 358
dsimms@37176 359 // If there is no remaining time, then there is an error
dsimms@37176 360 if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) {
dsimms@37176 361 print_safepoint_timeout(_blocking_timeout);
rprotacio@33763 362 }
duke@1 363 }
duke@1 364 }
dsimms@37176 365 assert(_waiting_to_block == 0, "sanity check");
duke@1 366
dsimms@37176 367 #ifndef PRODUCT
dsimms@37176 368 if (SafepointTimeout) {
dsimms@37176 369 jlong current_time = os::javaTimeNanos();
dsimms@37176 370 if (safepoint_limit_time < current_time) {
dsimms@37176 371 tty->print_cr("# SafepointSynchronize: Finished after "
dsimms@37176 372 INT64_FORMAT_W(6) " ms",
jwilhelm@46630 373 (int64_t)((current_time - safepoint_limit_time) / MICROUNITS +
jwilhelm@46630 374 (jlong)SafepointTimeoutDelay));
duke@1 375 }
duke@1 376 }
duke@1 377 #endif
duke@1 378
dsimms@37176 379 assert((_safepoint_counter & 0x1) == 0, "must be even");
dsimms@37176 380 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
dsimms@37176 381 _safepoint_counter ++;
duke@1 382
dsimms@37176 383 // Record state
dsimms@37176 384 _state = _synchronized;
duke@1 385
dsimms@37176 386 OrderAccess::fence();
dsimms@37176 387
dsimms@37176 388 if (wait_blocked_event.should_commit()) {
dsimms@37176 389 wait_blocked_event.set_safepointId(safepoint_counter());
dsimms@37176 390 wait_blocked_event.set_runningThreadCount(initial_waiting_to_block);
dsimms@37176 391 wait_blocked_event.commit();
dsimms@37176 392 }
dsimms@37176 393 } // EventSafepointWaitBlocked
duke@1 394
never@12108 395 #ifdef ASSERT
never@12108 396 for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) {
never@12108 397 // make sure all the threads were visited
never@12108 398 assert(cur->was_visited_for_critical_count(), "missed a thread");
never@12108 399 }
never@12108 400 #endif // ASSERT
never@12108 401
never@11631 402 // Update the count of active JNI critical regions
david@35492 403 GCLocker::set_jni_lock_count(_current_jni_active_count);
never@11631 404
rprotacio@33763 405 if (log_is_enabled(Debug, safepoint)) {
rehn@46496 406 log_debug(safepoint)("Entering safepoint region: %s", VMThread::vm_safepoint_description());
duke@1 407 }
duke@1 408
duke@1 409 RuntimeService::record_safepoint_synchronized();
duke@1 410 if (PrintSafepointStatistics) {
duke@1 411 update_statistics_on_sync_end(os::javaTimeNanos());
duke@1 412 }
duke@1 413
duke@1 414 // Call stuff that needs to be run when a safepoint is just about to be completed
dsimms@37176 415 {
dsimms@37176 416 EventSafepointCleanup cleanup_event;
dsimms@37176 417 do_cleanup_tasks();
dsimms@37176 418 if (cleanup_event.should_commit()) {
dsimms@37176 419 cleanup_event.set_safepointId(safepoint_counter());
dsimms@37176 420 cleanup_event.commit();
dsimms@37176 421 }
dsimms@37176 422 }
xlu@5042 423
xlu@5042 424 if (PrintSafepointStatistics) {
xlu@5042 425 // Record how much time spend on the above cleanup tasks
xlu@5042 426 update_statistics_on_cleanup_end(os::javaTimeNanos());
xlu@5042 427 }
dsimms@37176 428 if (begin_event.should_commit()) {
dsimms@37176 429 begin_event.set_safepointId(safepoint_counter());
dsimms@37176 430 begin_event.set_totalThreadCount(nof_threads);
dsimms@37176 431 begin_event.set_jniCriticalThreadCount(_current_jni_active_count);
dsimms@37176 432 begin_event.commit();
dsimms@37176 433 }
duke@1 434 }
duke@1 435
duke@1 436 // Wake up all threads, so they are ready to resume execution after the safepoint
duke@1 437 // operation has been carried out
duke@1 438 void SafepointSynchronize::end() {
dsimms@37176 439 EventSafepointEnd event;
dsimms@37176 440 int safepoint_id = safepoint_counter(); // Keep the odd counter as "id"
duke@1 441
duke@1 442 assert(Threads_lock->owned_by_self(), "must hold Threads_lock");
duke@1 443 assert((_safepoint_counter & 0x1) == 1, "must be odd");
duke@1 444 _safepoint_counter ++;
duke@1 445 // memory fence isn't required here since an odd _safepoint_counter
duke@1 446 // value can do no harm and a fence is issued below anyway.
duke@1 447
duke@1 448 DEBUG_ONLY(Thread* myThread = Thread::current();)
duke@1 449 assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint");
duke@1 450
duke@1 451 if (PrintSafepointStatistics) {
duke@1 452 end_statistics(os::javaTimeNanos());
duke@1 453 }
duke@1 454
duke@1 455 #ifdef ASSERT
duke@1 456 // A pending_exception cannot be installed during a safepoint. The threads
duke@1 457 // may install an async exception after they come back from a safepoint into
duke@1 458 // pending_exception after they unblock. But that should happen later.
rehn@48069 459 for (JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 460 assert (!(cur->has_pending_exception() &&
duke@1 461 cur->safepoint_state()->is_at_poll_safepoint()),
duke@1 462 "safepoint installed a pending exception");
duke@1 463 }
duke@1 464 #endif // ASSERT
duke@1 465
duke@1 466 if (PageArmed) {
rehn@48069 467 assert(SafepointMechanism::uses_global_page_poll(), "sanity");
duke@1 468 // Make polling safepoint aware
duke@1 469 os::make_polling_page_readable();
duke@1 470 PageArmed = 0 ;
duke@1 471 }
duke@1 472
rehn@48069 473 if (SafepointMechanism::uses_global_page_poll()) {
rehn@48069 474 // Remove safepoint check from interpreter
rehn@48069 475 Interpreter::ignore_safepoints();
rehn@48069 476 }
duke@1 477
duke@1 478 {
duke@1 479 MutexLocker mu(Safepoint_lock);
duke@1 480
duke@1 481 assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization");
duke@1 482
rehn@48069 483 if (SafepointMechanism::uses_thread_local_poll()) {
rehn@48069 484 _state = _not_synchronized;
rehn@48069 485 OrderAccess::storestore(); // global state -> local state
rehn@48069 486 for (JavaThread *current = Threads::first(); current; current = current->next()) {
rehn@48069 487 ThreadSafepointState* cur_state = current->safepoint_state();
rehn@48069 488 cur_state->restart(); // TSS _running
rehn@48069 489 SafepointMechanism::disarm_local_poll(current); // release store, local state -> polling page
rehn@48069 490 }
rehn@48069 491 log_debug(safepoint)("Leaving safepoint region");
rehn@48069 492 } else {
rehn@48069 493 // Set to not synchronized, so the threads will not go into the signal_thread_blocked method
rehn@48069 494 // when they get restarted.
rehn@48069 495 _state = _not_synchronized;
rehn@48069 496 OrderAccess::fence();
duke@1 497
rehn@48069 498 log_debug(safepoint)("Leaving safepoint region");
duke@1 499
rehn@48069 500 // Start suspended threads
rehn@48069 501 for (JavaThread *current = Threads::first(); current; current = current->next()) {
rehn@48069 502 // A problem occurring on Solaris is when attempting to restart threads
rehn@48069 503 // the first #cpus - 1 go well, but then the VMThread is preempted when we get
rehn@48069 504 // to the next one (since it has been running the longest). We then have
rehn@48069 505 // to wait for a cpu to become available before we can continue restarting
rehn@48069 506 // threads.
rehn@48069 507 // FIXME: This causes the performance of the VM to degrade when active and with
rehn@48069 508 // large numbers of threads. Apparently this is due to the synchronous nature
rehn@48069 509 // of suspending threads.
rehn@48069 510 //
rehn@48069 511 // TODO-FIXME: the comments above are vestigial and no longer apply.
rehn@48069 512 // Furthermore, using solaris' schedctl in this particular context confers no benefit
rehn@48069 513 if (VMThreadHintNoPreempt) {
rehn@48069 514 os::hint_no_preempt();
rehn@48069 515 }
rehn@48069 516 ThreadSafepointState* cur_state = current->safepoint_state();
rehn@48069 517 assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint");
rehn@48069 518 cur_state->restart();
rehn@48069 519 assert(cur_state->is_running(), "safepoint state has not been reset");
duke@1 520 }
duke@1 521 }
duke@1 522
duke@1 523 RuntimeService::record_safepoint_end();
duke@1 524
duke@1 525 // Release threads lock, so threads can be created/destroyed again. It will also starts all threads
duke@1 526 // blocked in signal_thread_blocked
duke@1 527 Threads_lock->unlock();
duke@1 528
duke@1 529 }
eosterlund@47791 530 Universe::heap()->safepoint_synchronize_end();
jwilhelm@22551 531 // record this time so VMThread can keep track how much time has elapsed
xlu@5042 532 // since last safepoint.
xlu@5042 533 _end_of_last_safepoint = os::javaTimeMillis();
dsimms@37176 534
dsimms@37176 535 if (event.should_commit()) {
dsimms@37176 536 event.set_safepointId(safepoint_id);
dsimms@37176 537 event.commit();
dsimms@37176 538 }
duke@1 539 }
duke@1 540
duke@1 541 bool SafepointSynchronize::is_cleanup_needed() {
rehn@46541 542 // Need a safepoint if there are many monitors to deflate.
rehn@46541 543 if (ObjectSynchronizer::is_cleanup_needed()) return true;
duke@1 544 // Need a safepoint if some inline cache buffers is non-empty
duke@1 545 if (!InlineCacheBuffer::is_empty()) return true;
duke@1 546 return false;
duke@1 547 }
duke@1 548
dsimms@37176 549 static void event_safepoint_cleanup_task_commit(EventSafepointCleanupTask& event, const char* name) {
dsimms@37176 550 if (event.should_commit()) {
dsimms@37176 551 event.set_safepointId(SafepointSynchronize::safepoint_counter());
dsimms@37176 552 event.set_name(name);
dsimms@37176 553 event.commit();
dsimms@37176 554 }
dsimms@37176 555 }
duke@1 556
rkennke@46702 557 class ParallelSPCleanupThreadClosure : public ThreadClosure {
rkennke@46702 558 private:
rkennke@46702 559 CodeBlobClosure* _nmethod_cl;
rkennke@46702 560 DeflateMonitorCounters* _counters;
rkennke@46702 561
rkennke@46702 562 public:
rkennke@46702 563 ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
rkennke@46702 564 _counters(counters),
rkennke@46702 565 _nmethod_cl(NMethodSweeper::prepare_mark_active_nmethods()) {}
rkennke@46702 566
rkennke@46702 567 void do_thread(Thread* thread) {
rkennke@46702 568 ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
rkennke@46702 569 if (_nmethod_cl != NULL && thread->is_Java_thread() &&
rkennke@46702 570 ! thread->is_Code_cache_sweeper_thread()) {
rkennke@46702 571 JavaThread* jt = (JavaThread*) thread;
rkennke@46702 572 jt->nmethods_do(_nmethod_cl);
rkennke@46702 573 }
rkennke@46702 574 }
rkennke@46702 575 };
rkennke@46702 576
rkennke@46702 577 class ParallelSPCleanupTask : public AbstractGangTask {
rkennke@46702 578 private:
rkennke@46702 579 SubTasksDone _subtasks;
rkennke@46702 580 ParallelSPCleanupThreadClosure _cleanup_threads_cl;
rkennke@46702 581 uint _num_workers;
rkennke@46702 582 DeflateMonitorCounters* _counters;
rkennke@46702 583 public:
rkennke@46702 584 ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
rkennke@46702 585 AbstractGangTask("Parallel Safepoint Cleanup"),
rkennke@46702 586 _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
rkennke@46702 587 _num_workers(num_workers),
rkennke@46702 588 _subtasks(SubTasksDone(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS)),
rkennke@46702 589 _counters(counters) {}
rkennke@46702 590
rkennke@46702 591 void work(uint worker_id) {
rkennke@46702 592 // All threads deflate monitors and mark nmethods (if necessary).
rkennke@47792 593 Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
rkennke@46702 594
rkennke@46702 595 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
rkennke@46702 596 const char* name = "deflating idle monitors";
rkennke@46702 597 EventSafepointCleanupTask event;
rkennke@46702 598 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 599 ObjectSynchronizer::deflate_idle_monitors(_counters);
rkennke@46702 600 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 601 }
rkennke@46702 602
rkennke@46702 603 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_UPDATE_INLINE_CACHES)) {
rkennke@46702 604 const char* name = "updating inline caches";
rkennke@46702 605 EventSafepointCleanupTask event;
rkennke@46702 606 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 607 InlineCacheBuffer::update_inline_caches();
rkennke@46702 608 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 609 }
rkennke@46702 610
rkennke@46702 611 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_COMPILATION_POLICY)) {
rkennke@46702 612 const char* name = "compilation policy safepoint handler";
rkennke@46702 613 EventSafepointCleanupTask event;
rkennke@46702 614 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 615 CompilationPolicy::policy()->do_safepoint_work();
rkennke@46702 616 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 617 }
rkennke@46702 618
rkennke@46702 619 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYMBOL_TABLE_REHASH)) {
rkennke@46702 620 if (SymbolTable::needs_rehashing()) {
rkennke@46702 621 const char* name = "rehashing symbol table";
rkennke@46702 622 EventSafepointCleanupTask event;
rkennke@46702 623 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 624 SymbolTable::rehash_table();
rkennke@46702 625 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 626 }
rkennke@46702 627 }
rkennke@46702 628
rkennke@46702 629 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_STRING_TABLE_REHASH)) {
rkennke@46702 630 if (StringTable::needs_rehashing()) {
rkennke@46702 631 const char* name = "rehashing string table";
rkennke@46702 632 EventSafepointCleanupTask event;
rkennke@46702 633 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 634 StringTable::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_CLD_PURGE)) {
rkennke@46702 640 // CMS delays purging the CLDG until the beginning of the next safepoint and to
rkennke@46702 641 // make sure concurrent sweep is done
rkennke@46702 642 const char* name = "purging class loader data graph";
rkennke@46702 643 EventSafepointCleanupTask event;
rkennke@46702 644 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 645 ClassLoaderDataGraph::purge_if_needed();
rkennke@46702 646 event_safepoint_cleanup_task_commit(event, name);
rkennke@46702 647 }
gziemski@47955 648
gziemski@47955 649 if (!_subtasks.is_task_claimed(SafepointSynchronize::SAFEPOINT_CLEANUP_SYSTEM_DICTIONARY_RESIZE)) {
gziemski@47955 650 const char* name = "resizing system dictionaries";
gziemski@47955 651 EventSafepointCleanupTask event;
gziemski@47955 652 TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
gziemski@47955 653 ClassLoaderDataGraph::resize_if_needed();
gziemski@47955 654 event_safepoint_cleanup_task_commit(event, name);
gziemski@47955 655 }
rkennke@46702 656 _subtasks.all_tasks_completed(_num_workers);
rkennke@46702 657 }
rkennke@46702 658 };
rkennke@46702 659
rkennke@46702 660 // Various cleaning tasks that should be done periodically at safepoints.
duke@1 661 void SafepointSynchronize::do_cleanup_tasks() {
rkennke@46702 662
rkennke@46702 663 TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
rkennke@46702 664
rkennke@46702 665 // Prepare for monitor deflation.
rkennke@46702 666 DeflateMonitorCounters deflate_counters;
rkennke@46702 667 ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
rkennke@46702 668
rkennke@46702 669 CollectedHeap* heap = Universe::heap();
rkennke@46702 670 assert(heap != NULL, "heap not initialized yet?");
rkennke@46702 671 WorkGang* cleanup_workers = heap->get_safepoint_workers();
rkennke@46702 672 if (cleanup_workers != NULL) {
rkennke@46702 673 // Parallel cleanup using GC provided thread pool.
rkennke@46702 674 uint num_cleanup_workers = cleanup_workers->active_workers();
rkennke@46702 675 ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
rkennke@46702 676 StrongRootsScope srs(num_cleanup_workers);
rkennke@46702 677 cleanup_workers->run_task(&cleanup);
rkennke@46702 678 } else {
rkennke@46702 679 // Serial cleanup using VMThread.
rkennke@46702 680 ParallelSPCleanupTask cleanup(1, &deflate_counters);
rkennke@46702 681 StrongRootsScope srs(1);
rkennke@46702 682 cleanup.work(0);
duke@1 683 }
duke@1 684
rkennke@46702 685 // Finish monitor deflation.
rkennke@46702 686 ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
duke@1 687 }
duke@1 688
duke@1 689
duke@1 690 bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) {
duke@1 691 switch(state) {
duke@1 692 case _thread_in_native:
duke@1 693 // native threads are safe if they have no java stack or have walkable stack
duke@1 694 return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable();
duke@1 695
duke@1 696 // blocked threads should have already have walkable stack
duke@1 697 case _thread_blocked:
duke@1 698 assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable");
duke@1 699 return true;
duke@1 700
duke@1 701 default:
duke@1 702 return false;
duke@1 703 }
duke@1 704 }
duke@1 705
duke@1 706
never@11637 707 // See if the thread is running inside a lazy critical native and
never@11637 708 // update the thread critical count if so. Also set a suspend flag to
never@11637 709 // cause the native wrapper to return into the JVM to do the unlock
never@11637 710 // once the native finishes.
never@11637 711 void SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) {
never@11637 712 if (state == _thread_in_native &&
never@11637 713 thread->has_last_Java_frame() &&
never@11637 714 thread->frame_anchor()->walkable()) {
never@11637 715 // This thread might be in a critical native nmethod so look at
never@11637 716 // the top of the stack and increment the critical count if it
never@11637 717 // is.
never@11637 718 frame wrapper_frame = thread->last_frame();
never@11637 719 CodeBlob* stub_cb = wrapper_frame.cb();
never@11637 720 if (stub_cb != NULL &&
never@11637 721 stub_cb->is_nmethod() &&
never@11637 722 stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) {
never@11637 723 // A thread could potentially be in a critical native across
never@11637 724 // more than one safepoint, so only update the critical state on
never@11637 725 // the first one. When it returns it will perform the unlock.
never@11637 726 if (!thread->do_critical_native_unlock()) {
never@11637 727 #ifdef ASSERT
never@11637 728 if (!thread->in_critical()) {
david@35492 729 GCLocker::increment_debug_jni_lock_count();
never@11637 730 }
never@11637 731 #endif
never@11637 732 thread->enter_critical();
never@11637 733 // Make sure the native wrapper calls back on return to
never@11637 734 // perform the needed critical unlock.
never@11637 735 thread->set_critical_native_unlock();
never@11637 736 }
never@11637 737 }
never@11637 738 }
never@11637 739 }
never@11637 740
never@11637 741
never@11637 742
duke@1 743 // -------------------------------------------------------------------------------------------------------
duke@1 744 // Implementation of Safepoint callback point
duke@1 745
duke@1 746 void SafepointSynchronize::block(JavaThread *thread) {
duke@1 747 assert(thread != NULL, "thread must be set");
duke@1 748 assert(thread->is_Java_thread(), "not a Java thread");
duke@1 749
duke@1 750 // Threads shouldn't block if they are in the middle of printing, but...
duke@1 751 ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id());
duke@1 752
duke@1 753 // Only bail from the block() call if the thread is gone from the
duke@1 754 // thread list; starting to exit should still block.
duke@1 755 if (thread->is_terminated()) {
duke@1 756 // block current thread if we come here from native code when VM is gone
duke@1 757 thread->block_if_vm_exited();
duke@1 758
duke@1 759 // otherwise do nothing
duke@1 760 return;
duke@1 761 }
duke@1 762
duke@1 763 JavaThreadState state = thread->thread_state();
duke@1 764 thread->frame_anchor()->make_walkable(thread);
duke@1 765
duke@1 766 // Check that we have a valid thread_state at this point
duke@1 767 switch(state) {
duke@1 768 case _thread_in_vm_trans:
duke@1 769 case _thread_in_Java: // From compiled code
duke@1 770
duke@1 771 // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case,
duke@1 772 // we pretend we are still in the VM.
duke@1 773 thread->set_thread_state(_thread_in_vm);
duke@1 774
duke@1 775 if (is_synchronizing()) {
duke@1 776 Atomic::inc (&TryingToBlock) ;
duke@1 777 }
duke@1 778
duke@1 779 // We will always be holding the Safepoint_lock when we are examine the state
duke@1 780 // of a thread. Hence, the instructions between the Safepoint_lock->lock() and
duke@1 781 // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code
duke@1 782 Safepoint_lock->lock_without_safepoint_check();
duke@1 783 if (is_synchronizing()) {
duke@1 784 // Decrement the number of threads to wait for and signal vm thread
duke@1 785 assert(_waiting_to_block > 0, "sanity check");
duke@1 786 _waiting_to_block--;
duke@1 787 thread->safepoint_state()->set_has_called_back(true);
duke@1 788
never@12108 789 DEBUG_ONLY(thread->set_visited_for_critical_count(true));
never@11631 790 if (thread->in_critical()) {
never@11631 791 // Notice that this thread is in a critical section
never@11631 792 increment_jni_active_count();
never@11631 793 }
never@11631 794
duke@1 795 // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread
duke@1 796 if (_waiting_to_block == 0) {
duke@1 797 Safepoint_lock->notify_all();
duke@1 798 }
duke@1 799 }
duke@1 800
duke@1 801 // We transition the thread to state _thread_blocked here, but
duke@1 802 // we can't do our usual check for external suspension and then
duke@1 803 // self-suspend after the lock_without_safepoint_check() call
duke@1 804 // below because we are often called during transitions while
duke@1 805 // we hold different locks. That would leave us suspended while
duke@1 806 // holding a resource which results in deadlocks.
duke@1 807 thread->set_thread_state(_thread_blocked);
duke@1 808 Safepoint_lock->unlock();
duke@1 809
duke@1 810 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during
duke@1 811 // the entire safepoint, the threads will all line up here during the safepoint.
duke@1 812 Threads_lock->lock_without_safepoint_check();
duke@1 813 // restore original state. This is important if the thread comes from compiled code, so it
duke@1 814 // will continue to execute with the _thread_in_Java state.
duke@1 815 thread->set_thread_state(state);
duke@1 816 Threads_lock->unlock();
duke@1 817 break;
duke@1 818
duke@1 819 case _thread_in_native_trans:
duke@1 820 case _thread_blocked_trans:
duke@1 821 case _thread_new_trans:
duke@1 822 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) {
duke@1 823 thread->print_thread_state();
duke@1 824 fatal("Deadlock in safepoint code. "
duke@1 825 "Should have called back to the VM before blocking.");
duke@1 826 }
duke@1 827
duke@1 828 // We transition the thread to state _thread_blocked here, but
duke@1 829 // we can't do our usual check for external suspension and then
duke@1 830 // self-suspend after the lock_without_safepoint_check() call
duke@1 831 // below because we are often called during transitions while
duke@1 832 // we hold different locks. That would leave us suspended while
duke@1 833 // holding a resource which results in deadlocks.
duke@1 834 thread->set_thread_state(_thread_blocked);
duke@1 835
duke@1 836 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence,
duke@1 837 // the safepoint code might still be waiting for it to block. We need to change the state here,
duke@1 838 // so it can see that it is at a safepoint.
duke@1 839
duke@1 840 // Block until the safepoint operation is completed.
duke@1 841 Threads_lock->lock_without_safepoint_check();
duke@1 842
duke@1 843 // Restore state
duke@1 844 thread->set_thread_state(state);
duke@1 845
duke@1 846 Threads_lock->unlock();
duke@1 847 break;
duke@1 848
duke@1 849 default:
david@33105 850 fatal("Illegal threadstate encountered: %d", state);
duke@1 851 }
duke@1 852
duke@1 853 // Check for pending. async. exceptions or suspends - except if the
duke@1 854 // thread was blocked inside the VM. has_special_runtime_exit_condition()
duke@1 855 // is called last since it grabs a lock and we only want to do that when
duke@1 856 // we must.
duke@1 857 //
duke@1 858 // Note: we never deliver an async exception at a polling point as the
duke@1 859 // compiler may not have an exception handler for it. The polling
duke@1 860 // code will notice the async and deoptimize and the exception will
duke@1 861 // be delivered. (Polling at a return point is ok though). Sure is
duke@1 862 // a lot of bother for a deprecated feature...
duke@1 863 //
duke@1 864 // We don't deliver an async exception if the thread state is
duke@1 865 // _thread_in_native_trans so JNI functions won't be called with
duke@1 866 // a surprising pending exception. If the thread state is going back to java,
duke@1 867 // async exception is checked in check_special_condition_for_native_trans().
duke@1 868
duke@1 869 if (state != _thread_blocked_trans &&
duke@1 870 state != _thread_in_vm_trans &&
duke@1 871 thread->has_special_runtime_exit_condition()) {
duke@1 872 thread->handle_special_runtime_exit_condition(
duke@1 873 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans));
duke@1 874 }
duke@1 875 }
duke@1 876
duke@1 877 // ------------------------------------------------------------------------------------------------------
duke@1 878 // Exception handlers
duke@1 879
duke@1 880
duke@1 881 void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) {
duke@1 882 assert(thread->is_Java_thread(), "polling reference encountered by VM thread");
duke@1 883 assert(thread->thread_state() == _thread_in_Java, "should come from Java code");
rehn@48069 884 if (!ThreadLocalHandshakes) {
rehn@48069 885 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization");
rehn@48069 886 }
duke@1 887
duke@1 888 if (ShowSafepointMsgs) {
duke@1 889 tty->print("handle_polling_page_exception: ");
duke@1 890 }
duke@1 891
duke@1 892 if (PrintSafepointStatistics) {
duke@1 893 inc_page_trap_count();
duke@1 894 }
duke@1 895
duke@1 896 ThreadSafepointState* state = thread->safepoint_state();
duke@1 897
duke@1 898 state->handle_polling_page_exception();
duke@1 899 }
duke@1 900
duke@1 901
duke@1 902 void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) {
duke@1 903 if (!timeout_error_printed) {
duke@1 904 timeout_error_printed = true;
jwilhelm@22551 905 // Print out the thread info which didn't reach the safepoint for debugging
duke@1 906 // purposes (useful when there are lots of threads in the debugger).
drchase@24424 907 tty->cr();
duke@1 908 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:");
duke@1 909 if (reason == _spinning_timeout) {
duke@1 910 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint.");
duke@1 911 } else if (reason == _blocking_timeout) {
duke@1 912 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop.");
duke@1 913 }
duke@1 914
duke@1 915 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:");
duke@1 916 ThreadSafepointState *cur_state;
duke@1 917 ResourceMark rm;
rehn@48069 918 for (JavaThread *cur_thread = Threads::first(); cur_thread;
duke@1 919 cur_thread = cur_thread->next()) {
duke@1 920 cur_state = cur_thread->safepoint_state();
duke@1 921
duke@1 922 if (cur_thread->thread_state() != _thread_blocked &&
duke@1 923 ((reason == _spinning_timeout && cur_state->is_running()) ||
duke@1 924 (reason == _blocking_timeout && !cur_state->has_called_back()))) {
duke@1 925 tty->print("# ");
duke@1 926 cur_thread->print();
drchase@24424 927 tty->cr();
duke@1 928 }
duke@1 929 }
duke@1 930 tty->print_cr("# SafepointSynchronize::begin: (End of list)");
duke@1 931 }
duke@1 932
duke@1 933 // To debug the long safepoint, specify both DieOnSafepointTimeout &
duke@1 934 // ShowMessageBoxOnError.
duke@1 935 if (DieOnSafepointTimeout) {
david@33105 936 fatal("Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.",
rehn@46496 937 SafepointTimeoutDelay, VMThread::vm_safepoint_description());
duke@1 938 }
duke@1 939 }
duke@1 940
duke@1 941
duke@1 942 // -------------------------------------------------------------------------------------------------------
duke@1 943 // Implementation of ThreadSafepointState
duke@1 944
duke@1 945 ThreadSafepointState::ThreadSafepointState(JavaThread *thread) {
duke@1 946 _thread = thread;
duke@1 947 _type = _running;
duke@1 948 _has_called_back = false;
duke@1 949 _at_poll_safepoint = false;
duke@1 950 }
duke@1 951
duke@1 952 void ThreadSafepointState::create(JavaThread *thread) {
duke@1 953 ThreadSafepointState *state = new ThreadSafepointState(thread);
duke@1 954 thread->set_safepoint_state(state);
duke@1 955 }
duke@1 956
duke@1 957 void ThreadSafepointState::destroy(JavaThread *thread) {
duke@1 958 if (thread->safepoint_state()) {
duke@1 959 delete(thread->safepoint_state());
duke@1 960 thread->set_safepoint_state(NULL);
duke@1 961 }
duke@1 962 }
duke@1 963
duke@1 964 void ThreadSafepointState::examine_state_of_thread() {
duke@1 965 assert(is_running(), "better be running or just have hit safepoint poll");
duke@1 966
duke@1 967 JavaThreadState state = _thread->thread_state();
duke@1 968
never@6269 969 // Save the state at the start of safepoint processing.
never@6269 970 _orig_thread_state = state;
never@6269 971
duke@1 972 // Check for a thread that is suspended. Note that thread resume tries
duke@1 973 // to grab the Threads_lock which we own here, so a thread cannot be
duke@1 974 // resumed during safepoint synchronization.
duke@1 975
dcubed@3826 976 // We check to see if this thread is suspended without locking to
dcubed@3826 977 // avoid deadlocking with a third thread that is waiting for this
dcubed@3826 978 // thread to be suspended. The third thread can notice the safepoint
dcubed@3826 979 // that we're trying to start at the beginning of its SR_lock->wait()
dcubed@3826 980 // call. If that happens, then the third thread will block on the
dcubed@3826 981 // safepoint while still holding the underlying SR_lock. We won't be
dcubed@3826 982 // able to get the SR_lock and we'll deadlock.
dcubed@3826 983 //
dcubed@3826 984 // We don't need to grab the SR_lock here for two reasons:
dcubed@3826 985 // 1) The suspend flags are both volatile and are set with an
dcubed@3826 986 // Atomic::cmpxchg() call so we should see the suspended
dcubed@3826 987 // state right away.
dcubed@3826 988 // 2) We're being called from the safepoint polling loop; if
dcubed@3826 989 // we don't see the suspended state on this iteration, then
dcubed@3826 990 // we'll come around again.
dcubed@3826 991 //
dcubed@3826 992 bool is_suspended = _thread->is_ext_suspended();
duke@1 993 if (is_suspended) {
duke@1 994 roll_forward(_at_safepoint);
duke@1 995 return;
duke@1 996 }
duke@1 997
duke@1 998 // Some JavaThread states have an initial safepoint state of
duke@1 999 // running, but are actually at a safepoint. We will happily
duke@1 1000 // agree and update the safepoint state here.
duke@1 1001 if (SafepointSynchronize::safepoint_safe(_thread, state)) {
never@12108 1002 SafepointSynchronize::check_for_lazy_critical_native(_thread, state);
never@11631 1003 roll_forward(_at_safepoint);
never@11631 1004 return;
duke@1 1005 }
duke@1 1006
duke@1 1007 if (state == _thread_in_vm) {
duke@1 1008 roll_forward(_call_back);
duke@1 1009 return;
duke@1 1010 }
duke@1 1011
duke@1 1012 // All other thread states will continue to run until they
duke@1 1013 // transition and self-block in state _blocked
duke@1 1014 // Safepoint polling in compiled code causes the Java threads to do the same.
duke@1 1015 // Note: new threads may require a malloc so they must be allowed to finish
duke@1 1016
duke@1 1017 assert(is_running(), "examine_state_of_thread on non-running thread");
duke@1 1018 return;
duke@1 1019 }
duke@1 1020
duke@1 1021 // Returns true is thread could not be rolled forward at present position.
duke@1 1022 void ThreadSafepointState::roll_forward(suspend_type type) {
duke@1 1023 _type = type;
duke@1 1024
duke@1 1025 switch(_type) {
duke@1 1026 case _at_safepoint:
duke@1 1027 SafepointSynchronize::signal_thread_at_safepoint();
never@12108 1028 DEBUG_ONLY(_thread->set_visited_for_critical_count(true));
never@12108 1029 if (_thread->in_critical()) {
never@12108 1030 // Notice that this thread is in a critical section
never@12108 1031 SafepointSynchronize::increment_jni_active_count();
never@12108 1032 }
duke@1 1033 break;
duke@1 1034
duke@1 1035 case _call_back:
duke@1 1036 set_has_called_back(false);
duke@1 1037 break;
duke@1 1038
duke@1 1039 case _running:
duke@1 1040 default:
duke@1 1041 ShouldNotReachHere();
duke@1 1042 }
duke@1 1043 }
duke@1 1044
duke@1 1045 void ThreadSafepointState::restart() {
duke@1 1046 switch(type()) {
duke@1 1047 case _at_safepoint:
duke@1 1048 case _call_back:
duke@1 1049 break;
duke@1 1050
duke@1 1051 case _running:
duke@1 1052 default:
bpittore@31592 1053 tty->print_cr("restart thread " INTPTR_FORMAT " with state %d",
david@33148 1054 p2i(_thread), _type);
duke@1 1055 _thread->print();
duke@1 1056 ShouldNotReachHere();
duke@1 1057 }
duke@1 1058 _type = _running;
duke@1 1059 set_has_called_back(false);
duke@1 1060 }
duke@1 1061
duke@1 1062
duke@1 1063 void ThreadSafepointState::print_on(outputStream *st) const {
goetz@33589 1064 const char *s = NULL;
duke@1 1065
duke@1 1066 switch(_type) {
duke@1 1067 case _running : s = "_running"; break;
duke@1 1068 case _at_safepoint : s = "_at_safepoint"; break;
duke@1 1069 case _call_back : s = "_call_back"; break;
duke@1 1070 default:
duke@1 1071 ShouldNotReachHere();
duke@1 1072 }
duke@1 1073
duke@1 1074 st->print_cr("Thread: " INTPTR_FORMAT
duke@1 1075 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d",
david@33148 1076 p2i(_thread), _thread->osthread()->thread_id(), s, _has_called_back,
duke@1 1077 _at_poll_safepoint);
duke@1 1078
duke@1 1079 _thread->print_thread_state_on(st);
duke@1 1080 }
duke@1 1081
duke@1 1082 // ---------------------------------------------------------------------------------------------------------------------
duke@1 1083
rehn@48069 1084 // Block the thread at poll or poll return for safepoint/handshake.
duke@1 1085 void ThreadSafepointState::handle_polling_page_exception() {
duke@1 1086
duke@1 1087 // Check state. block() will set thread state to thread_in_vm which will
duke@1 1088 // cause the safepoint state _type to become _call_back.
rehn@48069 1089 suspend_type t = type();
rehn@48069 1090 assert(!SafepointMechanism::uses_global_page_poll() || t == ThreadSafepointState::_running,
rehn@48069 1091 "polling page exception on thread not running state: %u", uint(t));
duke@1 1092
duke@1 1093 // Step 1: Find the nmethod from the return address
duke@1 1094 if (ShowSafepointMsgs && Verbose) {
david@33148 1095 tty->print_cr("Polling page exception at " INTPTR_FORMAT, p2i(thread()->saved_exception_pc()));
duke@1 1096 }
duke@1 1097 address real_return_addr = thread()->saved_exception_pc();
duke@1 1098
duke@1 1099 CodeBlob *cb = CodeCache::find_blob(real_return_addr);
rbackman@38133 1100 assert(cb != NULL && cb->is_compiled(), "return address should be in nmethod");
rbackman@38133 1101 CompiledMethod* nm = (CompiledMethod*)cb;
duke@1 1102
duke@1 1103 // Find frame of caller
duke@1 1104 frame stub_fr = thread()->last_frame();
duke@1 1105 CodeBlob* stub_cb = stub_fr.cb();
duke@1 1106 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub");
duke@1 1107 RegisterMap map(thread(), true);
duke@1 1108 frame caller_fr = stub_fr.sender(&map);
duke@1 1109
duke@1 1110 // Should only be poll_return or poll
duke@1 1111 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" );
duke@1 1112
duke@1 1113 // This is a poll immediately before a return. The exception handling code
duke@1 1114 // has already had the effect of causing the return to occur, so the execution
duke@1 1115 // will continue immediately after the call. In addition, the oopmap at the
duke@1 1116 // return point does not mark the return value as an oop (if it is), so
duke@1 1117 // it needs a handle here to be updated.
duke@1 1118 if( nm->is_at_poll_return(real_return_addr) ) {
duke@1 1119 // See if return type is an oop.
duke@1 1120 bool return_oop = nm->method()->is_returning_oop();
duke@1 1121 Handle return_value;
duke@1 1122 if (return_oop) {
duke@1 1123 // The oop result has been saved on the stack together with all
duke@1 1124 // the other registers. In order to preserve it over GCs we need
duke@1 1125 // to keep it in a handle.
duke@1 1126 oop result = caller_fr.saved_oop_result(&map);
coleenp@46968 1127 assert(oopDesc::is_oop_or_null(result), "must be oop");
duke@1 1128 return_value = Handle(thread(), result);
duke@1 1129 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer");
duke@1 1130 }
duke@1 1131
duke@1 1132 // Block the thread
rehn@48069 1133 SafepointMechanism::block_if_requested(thread());
duke@1 1134
duke@1 1135 // restore oop result, if any
duke@1 1136 if (return_oop) {
duke@1 1137 caller_fr.set_saved_oop_result(&map, return_value());
duke@1 1138 }
duke@1 1139 }
duke@1 1140
duke@1 1141 // This is a safepoint poll. Verify the return address and block.
duke@1 1142 else {
duke@1 1143 set_at_poll_safepoint(true);
duke@1 1144
duke@1 1145 // verify the blob built the "return address" correctly
duke@1 1146 assert(real_return_addr == caller_fr.pc(), "must match");
duke@1 1147
duke@1 1148 // Block the thread
rehn@48069 1149 SafepointMechanism::block_if_requested(thread());
duke@1 1150 set_at_poll_safepoint(false);
duke@1 1151
duke@1 1152 // If we have a pending async exception deoptimize the frame
duke@1 1153 // as otherwise we may never deliver it.
duke@1 1154 if (thread()->has_async_condition()) {
duke@1 1155 ThreadInVMfromJavaNoAsyncException __tiv(thread());
never@7106 1156 Deoptimization::deoptimize_frame(thread(), caller_fr.id());
duke@1 1157 }
duke@1 1158
duke@1 1159 // If an exception has been installed we must check for a pending deoptimization
duke@1 1160 // Deoptimize frame if exception has been thrown.
duke@1 1161
duke@1 1162 if (thread()->has_pending_exception() ) {
duke@1 1163 RegisterMap map(thread(), true);
duke@1 1164 frame caller_fr = stub_fr.sender(&map);
duke@1 1165 if (caller_fr.is_deoptimized_frame()) {
duke@1 1166 // The exception patch will destroy registers that are still
duke@1 1167 // live and will be needed during deoptimization. Defer the
jwilhelm@22551 1168 // Async exception should have deferred the exception until the
duke@1 1169 // next safepoint which will be detected when we get into
duke@1 1170 // the interpreter so if we have an exception now things
duke@1 1171 // are messed up.
duke@1 1172
duke@1 1173 fatal("Exception installed and deoptimization is pending");
duke@1 1174 }
duke@1 1175 }
duke@1 1176 }
duke@1 1177 }
duke@1 1178
duke@1 1179
duke@1 1180 //
duke@1 1181 // Statistics & Instrumentations
duke@1 1182 //
duke@1 1183 SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL;
xlu@5042 1184 jlong SafepointSynchronize::_safepoint_begin_time = 0;
duke@1 1185 int SafepointSynchronize::_cur_stat_index = 0;
duke@1 1186 julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating];
duke@1 1187 julong SafepointSynchronize::_coalesced_vmop_count = 0;
duke@1 1188 jlong SafepointSynchronize::_max_sync_time = 0;
xlu@5042 1189 jlong SafepointSynchronize::_max_vmop_time = 0;
xlu@5042 1190 float SafepointSynchronize::_ts_of_current_safepoint = 0.0f;
duke@1 1191
xlu@5042 1192 static jlong cleanup_end_time = 0;
duke@1 1193 static bool need_to_track_page_armed_status = false;
duke@1 1194 static bool init_done = false;
duke@1 1195
xlu@5042 1196 // Helper method to print the header.
xlu@5042 1197 static void print_header() {
shade@46473 1198 // The number of spaces is significant here, and should match the format
shade@46473 1199 // specifiers in print_statistics().
shade@46473 1200
shade@46473 1201 tty->print(" vmop "
shade@46473 1202 "[ threads: total initially_running wait_to_block ]"
shade@46473 1203 "[ time: spin block sync cleanup vmop ] ");
xlu@5042 1204
xlu@5042 1205 // no page armed status printed out if it is always armed.
xlu@5042 1206 if (need_to_track_page_armed_status) {
xlu@5042 1207 tty->print("page_armed ");
xlu@5042 1208 }
xlu@5042 1209
xlu@5042 1210 tty->print_cr("page_trap_count");
xlu@5042 1211 }
xlu@5042 1212
duke@1 1213 void SafepointSynchronize::deferred_initialize_stat() {
duke@1 1214 if (init_done) return;
duke@1 1215
duke@1 1216 // If PrintSafepointStatisticsTimeout is specified, the statistics data will
duke@1 1217 // be printed right away, in which case, _safepoint_stats will regress to
duke@1 1218 // a single element array. Otherwise, it is a circular ring buffer with default
duke@1 1219 // size of PrintSafepointStatisticsCount.
duke@1 1220 int stats_array_size;
duke@1 1221 if (PrintSafepointStatisticsTimeout > 0) {
duke@1 1222 stats_array_size = 1;
duke@1 1223 PrintSafepointStatistics = true;
duke@1 1224 } else {
duke@1 1225 stats_array_size = PrintSafepointStatisticsCount;
duke@1 1226 }
duke@1 1227 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size
zgu@13195 1228 * sizeof(SafepointStats), mtInternal);
duke@1 1229 guarantee(_safepoint_stats != NULL,
duke@1 1230 "not enough memory for safepoint instrumentation data");
duke@1 1231
shade@27662 1232 if (DeferPollingPageLoopCount >= 0) {
duke@1 1233 need_to_track_page_armed_status = true;
duke@1 1234 }
duke@1 1235 init_done = true;
duke@1 1236 }
duke@1 1237
duke@1 1238 void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) {
xlu@4006 1239 assert(init_done, "safepoint statistics array hasn't been initialized");
duke@1 1240 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1241
xlu@5042 1242 spstat->_time_stamp = _ts_of_current_safepoint;
xlu@5042 1243
duke@1 1244 VM_Operation *op = VMThread::vm_operation();
duke@1 1245 spstat->_vmop_type = (op != NULL ? op->type() : -1);
duke@1 1246 if (op != NULL) {
duke@1 1247 _safepoint_reasons[spstat->_vmop_type]++;
duke@1 1248 }
duke@1 1249
duke@1 1250 spstat->_nof_total_threads = nof_threads;
duke@1 1251 spstat->_nof_initial_running_threads = nof_running;
duke@1 1252 spstat->_nof_threads_hit_page_trap = 0;
duke@1 1253
duke@1 1254 // Records the start time of spinning. The real time spent on spinning
duke@1 1255 // will be adjusted when spin is done. Same trick is applied for time
duke@1 1256 // spent on waiting for threads to block.
duke@1 1257 if (nof_running != 0) {
duke@1 1258 spstat->_time_to_spin = os::javaTimeNanos();
duke@1 1259 } else {
duke@1 1260 spstat->_time_to_spin = 0;
duke@1 1261 }
duke@1 1262 }
duke@1 1263
duke@1 1264 void SafepointSynchronize::update_statistics_on_spin_end() {
duke@1 1265 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1266
duke@1 1267 jlong cur_time = os::javaTimeNanos();
duke@1 1268
duke@1 1269 spstat->_nof_threads_wait_to_block = _waiting_to_block;
duke@1 1270 if (spstat->_nof_initial_running_threads != 0) {
duke@1 1271 spstat->_time_to_spin = cur_time - spstat->_time_to_spin;
duke@1 1272 }
duke@1 1273
duke@1 1274 if (need_to_track_page_armed_status) {
duke@1 1275 spstat->_page_armed = (PageArmed == 1);
duke@1 1276 }
duke@1 1277
duke@1 1278 // Records the start time of waiting for to block. Updated when block is done.
duke@1 1279 if (_waiting_to_block != 0) {
duke@1 1280 spstat->_time_to_wait_to_block = cur_time;
duke@1 1281 } else {
duke@1 1282 spstat->_time_to_wait_to_block = 0;
duke@1 1283 }
duke@1 1284 }
duke@1 1285
duke@1 1286 void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) {
duke@1 1287 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1288
duke@1 1289 if (spstat->_nof_threads_wait_to_block != 0) {
duke@1 1290 spstat->_time_to_wait_to_block = end_time -
duke@1 1291 spstat->_time_to_wait_to_block;
duke@1 1292 }
duke@1 1293
duke@1 1294 // Records the end time of sync which will be used to calculate the total
duke@1 1295 // vm operation time. Again, the real time spending in syncing will be deducted
duke@1 1296 // from the start of the sync time later when end_statistics is called.
xlu@5042 1297 spstat->_time_to_sync = end_time - _safepoint_begin_time;
duke@1 1298 if (spstat->_time_to_sync > _max_sync_time) {
duke@1 1299 _max_sync_time = spstat->_time_to_sync;
duke@1 1300 }
xlu@5042 1301
xlu@5042 1302 spstat->_time_to_do_cleanups = end_time;
xlu@5042 1303 }
xlu@5042 1304
xlu@5042 1305 void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) {
xlu@5042 1306 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
xlu@5042 1307
xlu@5042 1308 // Record how long spent in cleanup tasks.
xlu@5042 1309 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups;
xlu@5042 1310
xlu@5042 1311 cleanup_end_time = end_time;
duke@1 1312 }
duke@1 1313
duke@1 1314 void SafepointSynchronize::end_statistics(jlong vmop_end_time) {
duke@1 1315 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1316
duke@1 1317 // Update the vm operation time.
xlu@5042 1318 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time;
xlu@5042 1319 if (spstat->_time_to_exec_vmop > _max_vmop_time) {
xlu@5042 1320 _max_vmop_time = spstat->_time_to_exec_vmop;
xlu@5042 1321 }
duke@1 1322 // Only the sync time longer than the specified
duke@1 1323 // PrintSafepointStatisticsTimeout will be printed out right away.
duke@1 1324 // By default, it is -1 meaning all samples will be put into the list.
duke@1 1325 if ( PrintSafepointStatisticsTimeout > 0) {
gziemski@33222 1326 if (spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1327 print_statistics();
duke@1 1328 }
duke@1 1329 } else {
duke@1 1330 // The safepoint statistics will be printed out when the _safepoin_stats
duke@1 1331 // array fills up.
xlu@5042 1332 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) {
duke@1 1333 print_statistics();
duke@1 1334 _cur_stat_index = 0;
xlu@5042 1335 } else {
xlu@5042 1336 _cur_stat_index++;
duke@1 1337 }
duke@1 1338 }
duke@1 1339 }
duke@1 1340
duke@1 1341 void SafepointSynchronize::print_statistics() {
xlu@5042 1342 for (int index = 0; index <= _cur_stat_index; index++) {
xlu@5042 1343 if (index % 30 == 0) {
xlu@5042 1344 print_header();
xlu@5042 1345 }
shade@46473 1346 SafepointStats* sstats = &_safepoint_stats[index];
shade@46473 1347 tty->print("%8.3f: ", sstats->_time_stamp);
shade@46473 1348 tty->print("%-30s [ "
shade@46473 1349 INT32_FORMAT_W(8) " " INT32_FORMAT_W(17) " " INT32_FORMAT_W(13) " "
shade@46473 1350 "]",
shade@46473 1351 (sstats->_vmop_type == -1 ? "no vm operation" : VM_Operation::name(sstats->_vmop_type)),
duke@1 1352 sstats->_nof_total_threads,
duke@1 1353 sstats->_nof_initial_running_threads,
duke@1 1354 sstats->_nof_threads_wait_to_block);
duke@1 1355 // "/ MICROUNITS " is to convert the unit from nanos to millis.
shade@46473 1356 tty->print("[ "
shade@46473 1357 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
shade@46473 1358 INT64_FORMAT_W(7) " " INT64_FORMAT_W(7) " "
shade@46473 1359 INT64_FORMAT_W(7) " ] ",
jwilhelm@46630 1360 (int64_t)(sstats->_time_to_spin / MICROUNITS),
jwilhelm@46630 1361 (int64_t)(sstats->_time_to_wait_to_block / MICROUNITS),
jwilhelm@46630 1362 (int64_t)(sstats->_time_to_sync / MICROUNITS),
jwilhelm@46630 1363 (int64_t)(sstats->_time_to_do_cleanups / MICROUNITS),
jwilhelm@46630 1364 (int64_t)(sstats->_time_to_exec_vmop / MICROUNITS));
duke@1 1365
duke@1 1366 if (need_to_track_page_armed_status) {
shade@46473 1367 tty->print(INT32_FORMAT_W(10) " ", sstats->_page_armed);
duke@1 1368 }
shade@46473 1369 tty->print_cr(INT32_FORMAT_W(15) " ", sstats->_nof_threads_hit_page_trap);
duke@1 1370 }
duke@1 1371 }
duke@1 1372
duke@1 1373 // This method will be called when VM exits. It will first call
duke@1 1374 // print_statistics to print out the rest of the sampling. Then
duke@1 1375 // it tries to summarize the sampling.
duke@1 1376 void SafepointSynchronize::print_stat_on_exit() {
duke@1 1377 if (_safepoint_stats == NULL) return;
duke@1 1378
duke@1 1379 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index];
duke@1 1380
duke@1 1381 // During VM exit, end_statistics may not get called and in that
duke@1 1382 // case, if the sync time is less than PrintSafepointStatisticsTimeout,
duke@1 1383 // don't print it out.
duke@1 1384 // Approximate the vm op time.
duke@1 1385 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop =
xlu@5042 1386 os::javaTimeNanos() - cleanup_end_time;
duke@1 1387
duke@1 1388 if ( PrintSafepointStatisticsTimeout < 0 ||
gziemski@33222 1389 spstat->_time_to_sync > (jlong)PrintSafepointStatisticsTimeout * MICROUNITS) {
duke@1 1390 print_statistics();
duke@1 1391 }
drchase@24424 1392 tty->cr();
duke@1 1393
duke@1 1394 // Print out polling page sampling status.
duke@1 1395 if (!need_to_track_page_armed_status) {
shade@27662 1396 tty->print_cr("Polling page always armed");
duke@1 1397 } else {
david@33148 1398 tty->print_cr("Defer polling page loop count = " INTX_FORMAT "\n",
david@33148 1399 DeferPollingPageLoopCount);
duke@1 1400 }
duke@1 1401
duke@1 1402 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) {
duke@1 1403 if (_safepoint_reasons[index] != 0) {
bpittore@31592 1404 tty->print_cr("%-26s" UINT64_FORMAT_W(10), VM_Operation::name(index),
duke@1 1405 _safepoint_reasons[index]);
duke@1 1406 }
duke@1 1407 }
duke@1 1408
bpittore@31592 1409 tty->print_cr(UINT64_FORMAT_W(5) " VM operations coalesced during safepoint",
duke@1 1410 _coalesced_vmop_count);
bpittore@31592 1411 tty->print_cr("Maximum sync time " INT64_FORMAT_W(5) " ms",
jwilhelm@46630 1412 (int64_t)(_max_sync_time / MICROUNITS));
xlu@5042 1413 tty->print_cr("Maximum vm operation time (except for Exit VM operation) "
bpittore@31592 1414 INT64_FORMAT_W(5) " ms",
jwilhelm@46630 1415 (int64_t)(_max_vmop_time / MICROUNITS));
duke@1 1416 }
duke@1 1417
duke@1 1418 // ------------------------------------------------------------------------------------------------
duke@1 1419 // Non-product code
duke@1 1420
duke@1 1421 #ifndef PRODUCT
duke@1 1422
duke@1 1423 void SafepointSynchronize::print_state() {
duke@1 1424 if (_state == _not_synchronized) {
duke@1 1425 tty->print_cr("not synchronized");
duke@1 1426 } else if (_state == _synchronizing || _state == _synchronized) {
duke@1 1427 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" :
duke@1 1428 "synchronized");
duke@1 1429
rehn@48069 1430 for (JavaThread *cur = Threads::first(); cur; cur = cur->next()) {
duke@1 1431 cur->safepoint_state()->print();
duke@1 1432 }
duke@1 1433 }
duke@1 1434 }
duke@1 1435
duke@1 1436 void SafepointSynchronize::safepoint_msg(const char* format, ...) {
duke@1 1437 if (ShowSafepointMsgs) {
duke@1 1438 va_list ap;
duke@1 1439 va_start(ap, format);
duke@1 1440 tty->vprint_cr(format, ap);
duke@1 1441 va_end(ap);
duke@1 1442 }
duke@1 1443 }
duke@1 1444
duke@1 1445 #endif // !PRODUCT