safepoint.cpp revision 6628:45831d971923
18876Srgrimes/* 24Srgrimes * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved. 34Srgrimes * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 44Srgrimes * 58876Srgrimes * This code is free software; you can redistribute it and/or modify it 64Srgrimes * under the terms of the GNU General Public License version 2 only, as 74Srgrimes * published by the Free Software Foundation. 84Srgrimes * 94Srgrimes * This code is distributed in the hope that it will be useful, but WITHOUT 104Srgrimes * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 118876Srgrimes * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 128876Srgrimes * version 2 for more details (a copy is included in the LICENSE file that 134Srgrimes * accompanied this code). 144Srgrimes * 158876Srgrimes * You should have received a copy of the GNU General Public License version 164Srgrimes * 2 along with this work; if not, write to the Free Software Foundation, 178876Srgrimes * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 184Srgrimes * 194Srgrimes * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 204Srgrimes * or visit www.oracle.com if you need additional information or have any 214Srgrimes * questions. 228876Srgrimes * 234Srgrimes */ 244Srgrimes 254Srgrimes#include "precompiled.hpp" 264Srgrimes#include "classfile/stringTable.hpp" 274Srgrimes#include "classfile/systemDictionary.hpp" 284Srgrimes#include "code/codeCache.hpp" 294Srgrimes#include "code/icBuffer.hpp" 304Srgrimes#include "code/nmethod.hpp" 314Srgrimes#include "code/pcDesc.hpp" 324Srgrimes#include "code/scopeDesc.hpp" 33116176Sobrien#include "gc_interface/collectedHeap.hpp" 34116176Sobrien#include "interpreter/interpreter.hpp" 35116176Sobrien#include "memory/resourceArea.hpp" 36116176Sobrien#include "memory/universe.inline.hpp" 372056Swollman#include "oops/oop.inline.hpp" 3842654Sjdp#include "oops/symbol.hpp" 3986998Sdd#include "runtime/compilationPolicy.hpp" 4086998Sdd#include "runtime/deoptimization.hpp" 4186998Sdd#include "runtime/frame.inline.hpp" 4217848Spst#include "runtime/interfaceSupport.hpp" 4386998Sdd#include "runtime/mutexLocker.hpp" 442056Swollman#include "runtime/orderAccess.inline.hpp" 4549558Sphk#include "runtime/osThread.hpp" 46126399Sphk#include "runtime/safepoint.hpp" 4712734Sbde#include "runtime/signature.hpp" 482056Swollman#include "runtime/stubCodeGenerator.hpp" 4912473Sbde#include "runtime/stubRoutines.hpp" 504Srgrimes#include "runtime/sweeper.hpp" 514Srgrimes#include "runtime/synchronizer.hpp" 524Srgrimes#include "runtime/thread.inline.hpp" 53118990Smarcel#include "services/memTracker.hpp" 5479418Sjulian#include "services/runtimeService.hpp" 554Srgrimes#include "utilities/events.hpp" 564Srgrimes#include "utilities/macros.hpp" 574Srgrimes#ifdef TARGET_ARCH_x86 584Srgrimes# include "nativeInst_x86.hpp" 594Srgrimes# include "vmreg_x86.inline.hpp" 6018296Sbde#endif 614Srgrimes#ifdef TARGET_ARCH_sparc 624Srgrimes# include "nativeInst_sparc.hpp" 634Srgrimes# include "vmreg_sparc.inline.hpp" 644Srgrimes#endif 654Srgrimes#ifdef TARGET_ARCH_zero 6678161Speter# include "nativeInst_zero.hpp" 6778161Speter# include "vmreg_zero.inline.hpp" 6878161Speter#endif 6912515Sphk#ifdef TARGET_ARCH_arm 7017848Spst# include "nativeInst_arm.hpp" 7186998Sdd# include "vmreg_arm.inline.hpp" 7285944Speter#endif 73126399Sphk#ifdef TARGET_ARCH_ppc 7417848Spst# include "nativeInst_ppc.hpp" 7518296Sbde# include "vmreg_ppc.inline.hpp" 7618296Sbde#endif 7718296Sbde#if INCLUDE_ALL_GCS 784Srgrimes#include "gc_implementation/concurrentMarkSweep/concurrentMarkSweepThread.hpp" 794Srgrimes#include "gc_implementation/shared/suspendibleThreadSet.hpp" 804Srgrimes#endif // INCLUDE_ALL_GCS 814Srgrimes#ifdef COMPILER1 824Srgrimes#include "c1/c1_globals.hpp" 8312515Sphk#endif 844Srgrimes 854SrgrimesPRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC 864Srgrimes 874Srgrimes// -------------------------------------------------------------------------------------------------- 884Srgrimes// Implementation of Safepoint begin/end 894Srgrimes 904SrgrimesSafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; 914Srgrimesvolatile int SafepointSynchronize::_waiting_to_block = 0; 924Srgrimesvolatile int SafepointSynchronize::_safepoint_counter = 0; 934Srgrimesint SafepointSynchronize::_current_jni_active_count = 0; 944Srgrimeslong SafepointSynchronize::_end_of_last_safepoint = 0; 954Srgrimesstatic volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE 964Srgrimesstatic volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only 974Srgrimesstatic bool timeout_error_printed = false; 984Srgrimes 994Srgrimes// Roll all threads forward to a safepoint and suspend them all 1004Srgrimesvoid SafepointSynchronize::begin() { 1014Srgrimes 1024Srgrimes Thread* myThread = Thread::current(); 1034Srgrimes assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); 1044Srgrimes 1054Srgrimes if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 10693009Sbde _safepoint_begin_time = os::javaTimeNanos(); 10793009Sbde _ts_of_current_safepoint = tty->time_stamp().seconds(); 10892756Salfred } 10993009Sbde 11093009Sbde#if INCLUDE_ALL_GCS 11192756Salfred if (UseConcMarkSweepGC) { 11293009Sbde // In the future we should investigate whether CMS can use the 11393009Sbde // more-general mechanism below. DLD (01/05). 11412473Sbde ConcurrentMarkSweepThread::synchronize(false); 1154Srgrimes } else if (UseG1GC) { 1164Srgrimes SuspendibleThreadSet::synchronize(); 1174Srgrimes } 11812515Sphk#endif // INCLUDE_ALL_GCS 11978161Speter 1204Srgrimes // By getting the Threads_lock, we assure that no threads are about to start or 1214Srgrimes // exit. It is released again in SafepointSynchronize::end(). 12218296Sbde Threads_lock->lock(); 12378161Speter 1244Srgrimes assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); 1254Srgrimes 1264Srgrimes int nof_threads = Threads::number_of_threads(); 12718296Sbde 1284Srgrimes if (TraceSafepoint) { 1294Srgrimes tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); 1304Srgrimes } 1314Srgrimes 1324Srgrimes RuntimeService::record_safepoint_begin(); 1334Srgrimes 1344Srgrimes MutexLocker mu(Safepoint_lock); 1354Srgrimes 1364Srgrimes // Reset the count of active JNI critical threads 1374Srgrimes _current_jni_active_count = 0; 1384Srgrimes 1394Srgrimes // Set number of threads to wait for, before we initiate the callbacks 1404Srgrimes _waiting_to_block = nof_threads; 1414Srgrimes TryingToBlock = 0 ; 1424Srgrimes int still_running = nof_threads; 1434Srgrimes 1444Srgrimes // Save the starting time, so that it can be compared to see if this has taken 1454Srgrimes // too long to complete. 1464Srgrimes jlong safepoint_limit_time; 1474Srgrimes timeout_error_printed = false; 1484Srgrimes 1494Srgrimes // PrintSafepointStatisticsTimeout can be specified separately. When 1504Srgrimes // specified, PrintSafepointStatistics will be set to true in 1514Srgrimes // deferred_initialize_stat method. The initialization has to be done 1524Srgrimes // early enough to avoid any races. See bug 6880029 for details. 1534Srgrimes if (PrintSafepointStatistics || PrintSafepointStatisticsTimeout > 0) { 1544Srgrimes deferred_initialize_stat(); 1554Srgrimes } 1564Srgrimes 1574Srgrimes // Begin the process of bringing the system to a safepoint. 1584Srgrimes // Java threads can be in several different states and are 1594Srgrimes // stopped by different mechanisms: 16018296Sbde // 16118296Sbde // 1. Running interpreted 16278161Speter // The interpreter dispatch table is changed to force it to 16318296Sbde // check for a safepoint condition between bytecodes. 16418296Sbde // 2. Running in native code 16518296Sbde // When returning from the native code, a Java thread must check 16618296Sbde // the safepoint _state to see if we must block. If the 16718296Sbde // VM thread sees a Java thread in native, it does 16818296Sbde // not wait for this thread to block. The order of the memory 16918296Sbde // writes and reads of both the safepoint state and the Java 17018296Sbde // threads state is critical. In order to guarantee that the 17118296Sbde // memory writes are serialized with respect to each other, 17218296Sbde // the VM thread issues a memory barrier instruction 17318296Sbde // (on MP systems). In order to avoid the overhead of issuing 17418296Sbde // a memory barrier for each Java thread making native calls, each Java 17518296Sbde // thread performs a write to a single memory page after changing 17618296Sbde // the thread state. The VM thread performs a sequence of 17718296Sbde // mprotect OS calls which forces all previous writes from all 17818296Sbde // Java threads to be serialized. This is done in the 17918296Sbde // os::serialize_thread_states() call. This has proven to be 18018296Sbde // much more efficient than executing a membar instruction 18118296Sbde // on every call to native code. 18218296Sbde // 3. Running compiled Code 18318296Sbde // Compiled code reads a global (Safepoint Polling) page that 18418296Sbde // is set to fault if we are trying to get to a safepoint. 18518296Sbde // 4. Blocked 18618296Sbde // A thread which is blocked will not be allowed to return from the 18718296Sbde // block condition until the safepoint operation is complete. 18818296Sbde // 5. In VM or Transitioning between states 18918296Sbde // If a Java thread is currently running in the VM or transitioning 19018296Sbde // between states, the safepointing code will wait for the thread to 19118296Sbde // block itself when it attempts transitions to a new state. 1924Srgrimes // 1934Srgrimes _state = _synchronizing; 1944Srgrimes OrderAccess::fence(); 1954Srgrimes 1964Srgrimes // Flush all thread states to memory 1974Srgrimes if (!UseMembar) { 1984Srgrimes os::serialize_thread_states(); 1994Srgrimes } 2004Srgrimes 20112515Sphk // Make interpreter safepoint aware 20278161Speter Interpreter::notice_safepoints(); 2034Srgrimes 20418296Sbde if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) { 20578161Speter // Make polling safepoint aware 2064Srgrimes guarantee (PageArmed == 0, "invariant") ; 2074Srgrimes PageArmed = 1 ; 20818296Sbde os::make_polling_page_unreadable(); 2094Srgrimes } 2104Srgrimes 2114Srgrimes // Consider using active_processor_count() ... but that call is expensive. 2124Srgrimes int ncpus = os::processor_count() ; 2134Srgrimes 21418296Sbde#ifdef ASSERT 21518296Sbde for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 21678161Speter assert(cur->safepoint_state()->is_running(), "Illegal initial state"); 21718296Sbde // Clear the visited flag to ensure that the critical counts are collected properly. 21818296Sbde cur->set_visited_for_critical_count(false); 21918296Sbde } 2204Srgrimes#endif // ASSERT 2214Srgrimes 22212515Sphk if (SafepointTimeout) 22378161Speter safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; 2244Srgrimes 2254Srgrimes // Iterate through all threads until it have been determined how to stop them all at a safepoint 22618296Sbde unsigned int iterations = 0; 22778161Speter int steps = 0 ; 2284Srgrimes while(still_running > 0) { 2294Srgrimes for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 2304Srgrimes assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); 2314Srgrimes ThreadSafepointState *cur_state = cur->safepoint_state(); 2324Srgrimes if (cur_state->is_running()) { 233798Swollman cur_state->examine_state_of_thread(); 2344Srgrimes if (!cur_state->is_running()) { 2354Srgrimes still_running--; 2364Srgrimes // consider adjusting steps downward: 2374Srgrimes // steps = 0 2384Srgrimes // steps -= NNN 2394Srgrimes // steps >>= 1 2404Srgrimes // steps = MIN(steps, 2000-100) 2414Srgrimes // if (iterations != 0) steps -= NNN 2424Srgrimes } 2434Srgrimes if (TraceSafepoint && Verbose) cur_state->print(); 2444Srgrimes } 2454Srgrimes } 24610348Sbde 2474Srgrimes if (PrintSafepointStatistics && iterations == 0) { 2484Srgrimes begin_statistics(nof_threads, still_running); 2494Srgrimes } 2504Srgrimes 2514Srgrimes if (still_running > 0) { 2524Srgrimes // Check for if it takes to long 2534Srgrimes if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { 2544Srgrimes print_safepoint_timeout(_spinning_timeout); 2554Srgrimes } 2564Srgrimes 2574Srgrimes // Spin to avoid context switching. 2584Srgrimes // There's a tension between allowing the mutators to run (and rendezvous) 2594Srgrimes // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that 2604Srgrimes // a mutator might otherwise use profitably to reach a safepoint. Excessive 26118296Sbde // spinning by the VM thread on a saturated system can increase rendezvous latency. 26278161Speter // Blocking or yielding incur their own penalties in the form of context switching 2634Srgrimes // and the resultant loss of $ residency. 2644Srgrimes // 2654Srgrimes // Further complicating matters is that yield() does not work as naively expected 2664Srgrimes // on many platforms -- yield() does not guarantee that any other ready threads 2674Srgrimes // will run. As such we revert to naked_short_sleep() after some number of iterations. 2684Srgrimes // nakes_short_sleep() is implemented as a short unconditional sleep. 2694Srgrimes // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping 2704Srgrimes // can actually increase the time it takes the VM thread to detect that a system-wide 2714Srgrimes // stop-the-world safepoint has been reached. In a pathological scenario such as that 2724Srgrimes // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. 2734Srgrimes // In that case the mutators will be stalled waiting for the safepoint to complete and the 27478161Speter // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread 2754Srgrimes // will eventually wake up and detect that all mutators are safe, at which point 2764Srgrimes // we'll again make progress. 2774Srgrimes // 2784Srgrimes // Beware too that that the VMThread typically runs at elevated priority. 2794Srgrimes // Its default priority is higher than the default mutator priority. 2804Srgrimes // Obviously, this complicates spinning. 28118296Sbde // 28218296Sbde // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). 283104321Sphk // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. 28478161Speter // 28578161Speter // See the comments in synchronizer.cpp for additional remarks on spinning. 286104321Sphk // 28718296Sbde // In the future we might: 2884Srgrimes // 1. Modify the safepoint scheme to avoid potentially unbounded spinning. 2894Srgrimes // This is tricky as the path used by a thread exiting the JVM (say on 29078161Speter // on JNI call-out) simply stores into its state field. The burden 2914Srgrimes // is placed on the VM thread, which must poll (spin). 2924Srgrimes // 2. Find something useful to do while spinning. If the safepoint is GC-related 2934Srgrimes // we might aggressively scan the stacks of threads that are already safe. 2944Srgrimes // 3. Use Solaris schedctl to examine the state of the still-running mutators. 2954Srgrimes // If all the mutators are ONPROC there's no reason to sleep or yield. 2964Srgrimes // 4. YieldTo() any still-running mutators that are ready but OFFPROC. 2974Srgrimes // 5. Check system saturation. If the system is not fully saturated then 2984Srgrimes // simply spin and avoid sleep/yield. 2994Srgrimes // 6. As still-running mutators rendezvous they could unpark the sleeping 3004Srgrimes // VMthread. This works well for still-running mutators that become 3014Srgrimes // safe. The VMthread must still poll for mutators that call-out. 3024Srgrimes // 7. Drive the policy on time-since-begin instead of iterations. 3034Srgrimes // 8. Consider making the spin duration a function of the # of CPUs: 3044Srgrimes // Spin = (((ncpus-1) * M) + K) + F(still_running) 3054Srgrimes // Alternately, instead of counting iterations of the outer loop 3064Srgrimes // we could count the # of threads visited in the inner loop, above. 3074Srgrimes // 9. On windows consider using the return value from SwitchThreadTo() 3084Srgrimes // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. 3094Srgrimes 3104Srgrimes if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) { 3114Srgrimes guarantee (PageArmed == 0, "invariant") ; 3124Srgrimes PageArmed = 1 ; 3134Srgrimes os::make_polling_page_unreadable(); 3144Srgrimes } 3154Srgrimes 3164Srgrimes // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or 3174Srgrimes // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) 3184Srgrimes ++steps ; 3194Srgrimes if (ncpus > 1 && steps < SafepointSpinBeforeYield) { 3204Srgrimes SpinPause() ; // MP-Polite spin 3214Srgrimes } else 3224Srgrimes if (steps < DeferThrSuspendLoopCount) { 3234Srgrimes os::NakedYield() ; 3244Srgrimes } else { 3254Srgrimes os::naked_short_sleep(1); 3264Srgrimes } 3274Srgrimes 3284Srgrimes iterations ++ ; 3294Srgrimes } 3304Srgrimes assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); 3314Srgrimes } 3324Srgrimes assert(still_running == 0, "sanity check"); 3334Srgrimes 3344Srgrimes if (PrintSafepointStatistics) { 3354Srgrimes update_statistics_on_spin_end(); 3364Srgrimes } 3374Srgrimes 3384Srgrimes // wait until all threads are stopped 3394Srgrimes while (_waiting_to_block > 0) { 3404Srgrimes if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); 3414Srgrimes if (!SafepointTimeout || timeout_error_printed) { 3424Srgrimes Safepoint_lock->wait(true); // true, means with no safepoint checks 3434Srgrimes } else { 3444Srgrimes // Compute remaining time 3454Srgrimes jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); 3464Srgrimes 3474Srgrimes // If there is no remaining time, then there is an error 3484Srgrimes if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { 349118268Sjhb print_safepoint_timeout(_blocking_timeout); 3504Srgrimes } 3514Srgrimes } 3524Srgrimes } 3534Srgrimes assert(_waiting_to_block == 0, "sanity check"); 3544Srgrimes 3554Srgrimes#ifndef PRODUCT 3564Srgrimes if (SafepointTimeout) { 3574Srgrimes jlong current_time = os::javaTimeNanos(); 3584Srgrimes if (safepoint_limit_time < current_time) { 3594Srgrimes tty->print_cr("# SafepointSynchronize: Finished after " 3604Srgrimes INT64_FORMAT_W(6) " ms", 3614Srgrimes ((current_time - safepoint_limit_time) / MICROUNITS + 3624Srgrimes SafepointTimeoutDelay)); 3634Srgrimes } 3644Srgrimes } 3654Srgrimes#endif 3664Srgrimes 3674Srgrimes assert((_safepoint_counter & 0x1) == 0, "must be even"); 3684Srgrimes assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 3694Srgrimes _safepoint_counter ++; 3704Srgrimes 3714Srgrimes // Record state 3724Srgrimes _state = _synchronized; 3734Srgrimes 3744Srgrimes OrderAccess::fence(); 3754Srgrimes 3762112Swollman#ifdef ASSERT 37712515Sphk for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { 3784Srgrimes // make sure all the threads were visited 3791147Sguido assert(cur->was_visited_for_critical_count(), "missed a thread"); 3802320Sdg } 3811549Srgrimes#endif // ASSERT 3824Srgrimes 3834Srgrimes // Update the count of active JNI critical regions 3844Srgrimes GC_locker::set_jni_lock_count(_current_jni_active_count); 38512515Sphk 3864Srgrimes if (TraceSafepoint) { 3874Srgrimes VM_Operation *op = VMThread::vm_operation(); 3884Srgrimes tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); 3894Srgrimes } 3904Srgrimes 3914Srgrimes RuntimeService::record_safepoint_synchronized(); 3924Srgrimes if (PrintSafepointStatistics) { 3934Srgrimes update_statistics_on_sync_end(os::javaTimeNanos()); 3944Srgrimes } 3954Srgrimes 39612515Sphk // Call stuff that needs to be run when a safepoint is just about to be completed 3974Srgrimes do_cleanup_tasks(); 3986920Sjoerg 3994Srgrimes if (PrintSafepointStatistics) { 4004Srgrimes // Record how much time spend on the above cleanup tasks 4014Srgrimes update_statistics_on_cleanup_end(os::javaTimeNanos()); 4024Srgrimes } 4034Srgrimes} 4044Srgrimes 4054Srgrimes// Wake up all threads, so they are ready to resume execution after the safepoint 4064Srgrimes// operation has been carried out 4074Srgrimesvoid SafepointSynchronize::end() { 4084Srgrimes 4094Srgrimes assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); 41079573Sbsd assert((_safepoint_counter & 0x1) == 1, "must be odd"); 41179573Sbsd _safepoint_counter ++; 4124Srgrimes // memory fence isn't required here since an odd _safepoint_counter 4134Srgrimes // value can do no harm and a fence is issued below anyway. 4144Srgrimes 4154Srgrimes DEBUG_ONLY(Thread* myThread = Thread::current();) 4164Srgrimes assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); 4174Srgrimes 4184Srgrimes if (PrintSafepointStatistics) { 4194Srgrimes end_statistics(os::javaTimeNanos()); 420115607Sphk } 4214Srgrimes 4224Srgrimes#ifdef ASSERT 4231147Sguido // A pending_exception cannot be installed during a safepoint. The threads 42417848Spst // may install an async exception after they come back from a safepoint into 42585944Speter // pending_exception after they unblock. But that should happen later. 42686998Sdd for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 427126399Sphk assert (!(cur->has_pending_exception() && 4284Srgrimes cur->safepoint_state()->is_at_poll_safepoint()), 4294Srgrimes "safepoint installed a pending exception"); 4304Srgrimes } 43112515Sphk#endif // ASSERT 4324Srgrimes 4337090Sbde if (PageArmed) { 4344Srgrimes // Make polling safepoint aware 4354Srgrimes os::make_polling_page_readable(); 4364Srgrimes PageArmed = 0 ; 4374Srgrimes } 4384Srgrimes 4394Srgrimes // Remove safepoint check from interpreter 4404Srgrimes Interpreter::ignore_safepoints(); 4414Srgrimes 4424Srgrimes { 4434Srgrimes MutexLocker mu(Safepoint_lock); 4444Srgrimes 4457090Sbde assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); 4464Srgrimes 44733296Sbde // Set to not synchronized, so the threads will not go into the signal_thread_blocked method 44833296Sbde // when they get restarted. 44933296Sbde _state = _not_synchronized; 45033296Sbde OrderAccess::fence(); 45133296Sbde 4526204Sphk if (TraceSafepoint) { 4537170Sdg tty->print_cr("Leaving safepoint region"); 4546204Sphk } 4556204Sphk 4566204Sphk // Start suspended threads 4574Srgrimes for(JavaThread *current = Threads::first(); current; current = current->next()) { 4584Srgrimes // A problem occurring on Solaris is when attempting to restart threads 4594Srgrimes // the first #cpus - 1 go well, but then the VMThread is preempted when we get 4604Srgrimes // to the next one (since it has been running the longest). We then have 4614Srgrimes // to wait for a cpu to become available before we can continue restarting 4624Srgrimes // threads. 4634Srgrimes // FIXME: This causes the performance of the VM to degrade when active and with 4644Srgrimes // large numbers of threads. Apparently this is due to the synchronous nature 4654Srgrimes // of suspending threads. 4664Srgrimes // 4674Srgrimes // TODO-FIXME: the comments above are vestigial and no longer apply. 4684Srgrimes // Furthermore, using solaris' schedctl in this particular context confers no benefit 4694Srgrimes if (VMThreadHintNoPreempt) { 4704Srgrimes os::hint_no_preempt(); 4714Srgrimes } 4724Srgrimes ThreadSafepointState* cur_state = current->safepoint_state(); 4734Srgrimes assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); 4744Srgrimes cur_state->restart(); 47518296Sbde assert(cur_state->is_running(), "safepoint state has not been reset"); 47678161Speter } 4774Srgrimes 4784Srgrimes RuntimeService::record_safepoint_end(); 4794Srgrimes 4804Srgrimes // Release threads lock, so threads can be created/destroyed again. It will also starts all threads 4814Srgrimes // blocked in signal_thread_blocked 482103746Smarkm Threads_lock->unlock(); 4834Srgrimes 4844Srgrimes } 48579884Skris#if INCLUDE_ALL_GCS 4864Srgrimes // If there are any concurrent GC threads resume them. 4874Srgrimes if (UseConcMarkSweepGC) { 4884Srgrimes ConcurrentMarkSweepThread::desynchronize(false); 4894Srgrimes } else if (UseG1GC) { 4904Srgrimes SuspendibleThreadSet::desynchronize(); 4914Srgrimes } 4924Srgrimes#endif // INCLUDE_ALL_GCS 4934Srgrimes // record this time so VMThread can keep track how much time has elapsed 4944Srgrimes // since last safepoint. 49512515Sphk _end_of_last_safepoint = os::javaTimeMillis(); 49610348Sbde} 49710348Sbde 49810348Sbdebool SafepointSynchronize::is_cleanup_needed() { 49910348Sbde // Need a safepoint if some inline cache buffers is non-empty 50010348Sbde if (!InlineCacheBuffer::is_empty()) return true; 5014Srgrimes return false; 5024Srgrimes} 50312473Sbde 5044Srgrimes 5054Srgrimes 5064Srgrimes// Various cleaning tasks that should be done periodically at safepoints 50792756Salfredvoid SafepointSynchronize::do_cleanup_tasks() { 50893009Sbde { 50993009Sbde TraceTime t1("deflating idle monitors", TraceSafepointCleanupTime); 51012473Sbde ObjectSynchronizer::deflate_idle_monitors(); 5114Srgrimes } 5124Srgrimes 5134Srgrimes { 5144Srgrimes TraceTime t2("updating inline caches", TraceSafepointCleanupTime); 5154Srgrimes InlineCacheBuffer::update_inline_caches(); 5164Srgrimes } 5174Srgrimes { 51812473Sbde TraceTime t3("compilation policy safepoint handler", TraceSafepointCleanupTime); 5194Srgrimes CompilationPolicy::policy()->do_safepoint_work(); 5204Srgrimes } 5214Srgrimes 5224Srgrimes { 5234Srgrimes TraceTime t4("mark nmethods", TraceSafepointCleanupTime); 5244Srgrimes NMethodSweeper::mark_active_nmethods(); 5254Srgrimes } 5264Srgrimes 5274Srgrimes if (SymbolTable::needs_rehashing()) { 5284Srgrimes TraceTime t5("rehashing symbol table", TraceSafepointCleanupTime); 5294Srgrimes SymbolTable::rehash_table(); 5304Srgrimes } 5314Srgrimes 5324Srgrimes if (StringTable::needs_rehashing()) { 5334Srgrimes TraceTime t6("rehashing string table", TraceSafepointCleanupTime); 5344Srgrimes StringTable::rehash_table(); 5354Srgrimes } 5364Srgrimes 5374Srgrimes // rotate log files? 5384Srgrimes if (UseGCLogFileRotation) { 5394Srgrimes gclog_or_tty->rotate_log(false); 5404Srgrimes } 5414Srgrimes 5424Srgrimes { 5434Srgrimes // CMS delays purging the CLDG until the beginning of the next safepoint and to 5444Srgrimes // make sure concurrent sweep is done 5454Srgrimes TraceTime t7("purging class loader data graph", TraceSafepointCleanupTime); 5464Srgrimes ClassLoaderDataGraph::purge_if_needed(); 5474Srgrimes } 5484Srgrimes 5494Srgrimes if (MemTracker::is_on()) { 5504Srgrimes MemTracker::sync(); 5514Srgrimes } 5524Srgrimes} 55348407Speter 5544Srgrimes 55517848Spstbool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { 55617848Spst switch(state) { 55717848Spst case _thread_in_native: 558111017Sphk // native threads are safe if they have no java stack or have walkable stack 55946783Sphk return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); 56046783Sphk 56146658Smckusick // blocked threads should have already have walkable stack 56217848Spst case _thread_blocked: 56317848Spst assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); 56417848Spst return true; 56517848Spst 56617848Spst default: 56717848Spst return false; 56817848Spst } 56946658Smckusick} 570111017Sphk 57146658Smckusick 57246658Smckusick// See if the thread is running inside a lazy critical native and 57346658Smckusick// update the thread critical count if so. Also set a suspend flag to 57446658Smckusick// cause the native wrapper to return into the JVM to do the unlock 57517848Spst// once the native finishes. 57617848Spstvoid SafepointSynchronize::check_for_lazy_critical_native(JavaThread *thread, JavaThreadState state) { 57717848Spst if (state == _thread_in_native && 57817848Spst thread->has_last_Java_frame() && 57917848Spst thread->frame_anchor()->walkable()) { 58017848Spst // This thread might be in a critical native nmethod so look at 58185944Speter // the top of the stack and increment the critical count if it 58285944Speter // is. 58386998Sdd frame wrapper_frame = thread->last_frame(); 58486998Sdd CodeBlob* stub_cb = wrapper_frame.cb(); 58586998Sdd if (stub_cb != NULL && 58686998Sdd stub_cb->is_nmethod() && 58786998Sdd stub_cb->as_nmethod_or_null()->is_lazy_critical_native()) { 58886998Sdd // A thread could potentially be in a critical native across 58986998Sdd // more than one safepoint, so only update the critical state on 59086998Sdd // the first one. When it returns it will perform the unlock. 59186998Sdd if (!thread->do_critical_native_unlock()) { 59286998Sdd#ifdef ASSERT 59386998Sdd if (!thread->in_critical()) { 59486998Sdd GC_locker::increment_debug_jni_lock_count(); 59586998Sdd } 59686998Sdd#endif 59786998Sdd thread->enter_critical(); 59886998Sdd // Make sure the native wrapper calls back on return to 59986998Sdd // perform the needed critical unlock. 60086998Sdd thread->set_critical_native_unlock(); 60186998Sdd } 60286998Sdd } 60386998Sdd } 60486998Sdd} 60586998Sdd 60686998Sdd 60786998Sdd 60886998Sdd// ------------------------------------------------------------------------------------------------------- 60986998Sdd// Implementation of Safepoint callback point 61086998Sdd 61186998Sddvoid SafepointSynchronize::block(JavaThread *thread) { 61286998Sdd assert(thread != NULL, "thread must be set"); 61386998Sdd assert(thread->is_Java_thread(), "not a Java thread"); 61486998Sdd 61586998Sdd // Threads shouldn't block if they are in the middle of printing, but... 61686998Sdd ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); 61786998Sdd 61886998Sdd // Only bail from the block() call if the thread is gone from the 61986998Sdd // thread list; starting to exit should still block. 62089442Smjacob if (thread->is_terminated()) { 62186998Sdd // block current thread if we come here from native code when VM is gone 62286998Sdd thread->block_if_vm_exited(); 62386998Sdd 62489442Smjacob // otherwise do nothing 62586998Sdd return; 62686998Sdd } 62786998Sdd 62886998Sdd JavaThreadState state = thread->thread_state(); 62986998Sdd thread->frame_anchor()->make_walkable(thread); 63086998Sdd 63186998Sdd // Check that we have a valid thread_state at this point 63286998Sdd switch(state) { 63386998Sdd case _thread_in_vm_trans: 63486998Sdd case _thread_in_Java: // From compiled code 63586998Sdd 63685944Speter // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, 63785944Speter // we pretend we are still in the VM. 63885944Speter thread->set_thread_state(_thread_in_vm); 63985944Speter 64085944Speter if (is_synchronizing()) { 64185944Speter Atomic::inc (&TryingToBlock) ; 64285944Speter } 64385944Speter 64485944Speter // We will always be holding the Safepoint_lock when we are examine the state 645126399Sphk // of a thread. Hence, the instructions between the Safepoint_lock->lock() and 646126399Sphk // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code 647126399Sphk Safepoint_lock->lock_without_safepoint_check(); 648126399Sphk if (is_synchronizing()) { 649126399Sphk // Decrement the number of threads to wait for and signal vm thread 650126399Sphk assert(_waiting_to_block > 0, "sanity check"); 651126399Sphk _waiting_to_block--; 652126399Sphk thread->safepoint_state()->set_has_called_back(true); 653126399Sphk 654126399Sphk DEBUG_ONLY(thread->set_visited_for_critical_count(true)); 655126399Sphk if (thread->in_critical()) { 656126399Sphk // Notice that this thread is in a critical section 657126399Sphk increment_jni_active_count(); 658126399Sphk } 659126399Sphk 660126399Sphk // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread 661126399Sphk if (_waiting_to_block == 0) { 662126399Sphk Safepoint_lock->notify_all(); 663 } 664 } 665 666 // We transition the thread to state _thread_blocked here, but 667 // we can't do our usual check for external suspension and then 668 // self-suspend after the lock_without_safepoint_check() call 669 // below because we are often called during transitions while 670 // we hold different locks. That would leave us suspended while 671 // holding a resource which results in deadlocks. 672 thread->set_thread_state(_thread_blocked); 673 Safepoint_lock->unlock(); 674 675 // We now try to acquire the threads lock. Since this lock is hold by the VM thread during 676 // the entire safepoint, the threads will all line up here during the safepoint. 677 Threads_lock->lock_without_safepoint_check(); 678 // restore original state. This is important if the thread comes from compiled code, so it 679 // will continue to execute with the _thread_in_Java state. 680 thread->set_thread_state(state); 681 Threads_lock->unlock(); 682 break; 683 684 case _thread_in_native_trans: 685 case _thread_blocked_trans: 686 case _thread_new_trans: 687 if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { 688 thread->print_thread_state(); 689 fatal("Deadlock in safepoint code. " 690 "Should have called back to the VM before blocking."); 691 } 692 693 // We transition the thread to state _thread_blocked here, but 694 // we can't do our usual check for external suspension and then 695 // self-suspend after the lock_without_safepoint_check() call 696 // below because we are often called during transitions while 697 // we hold different locks. That would leave us suspended while 698 // holding a resource which results in deadlocks. 699 thread->set_thread_state(_thread_blocked); 700 701 // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, 702 // the safepoint code might still be waiting for it to block. We need to change the state here, 703 // so it can see that it is at a safepoint. 704 705 // Block until the safepoint operation is completed. 706 Threads_lock->lock_without_safepoint_check(); 707 708 // Restore state 709 thread->set_thread_state(state); 710 711 Threads_lock->unlock(); 712 break; 713 714 default: 715 fatal(err_msg("Illegal threadstate encountered: %d", state)); 716 } 717 718 // Check for pending. async. exceptions or suspends - except if the 719 // thread was blocked inside the VM. has_special_runtime_exit_condition() 720 // is called last since it grabs a lock and we only want to do that when 721 // we must. 722 // 723 // Note: we never deliver an async exception at a polling point as the 724 // compiler may not have an exception handler for it. The polling 725 // code will notice the async and deoptimize and the exception will 726 // be delivered. (Polling at a return point is ok though). Sure is 727 // a lot of bother for a deprecated feature... 728 // 729 // We don't deliver an async exception if the thread state is 730 // _thread_in_native_trans so JNI functions won't be called with 731 // a surprising pending exception. If the thread state is going back to java, 732 // async exception is checked in check_special_condition_for_native_trans(). 733 734 if (state != _thread_blocked_trans && 735 state != _thread_in_vm_trans && 736 thread->has_special_runtime_exit_condition()) { 737 thread->handle_special_runtime_exit_condition( 738 !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); 739 } 740} 741 742// ------------------------------------------------------------------------------------------------------ 743// Exception handlers 744 745 746void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { 747 assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); 748 assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); 749 assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); 750 751 if (ShowSafepointMsgs) { 752 tty->print("handle_polling_page_exception: "); 753 } 754 755 if (PrintSafepointStatistics) { 756 inc_page_trap_count(); 757 } 758 759 ThreadSafepointState* state = thread->safepoint_state(); 760 761 state->handle_polling_page_exception(); 762} 763 764 765void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { 766 if (!timeout_error_printed) { 767 timeout_error_printed = true; 768 // Print out the thread info which didn't reach the safepoint for debugging 769 // purposes (useful when there are lots of threads in the debugger). 770 tty->cr(); 771 tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); 772 if (reason == _spinning_timeout) { 773 tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); 774 } else if (reason == _blocking_timeout) { 775 tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); 776 } 777 778 tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); 779 ThreadSafepointState *cur_state; 780 ResourceMark rm; 781 for(JavaThread *cur_thread = Threads::first(); cur_thread; 782 cur_thread = cur_thread->next()) { 783 cur_state = cur_thread->safepoint_state(); 784 785 if (cur_thread->thread_state() != _thread_blocked && 786 ((reason == _spinning_timeout && cur_state->is_running()) || 787 (reason == _blocking_timeout && !cur_state->has_called_back()))) { 788 tty->print("# "); 789 cur_thread->print(); 790 tty->cr(); 791 } 792 } 793 tty->print_cr("# SafepointSynchronize::begin: (End of list)"); 794 } 795 796 // To debug the long safepoint, specify both DieOnSafepointTimeout & 797 // ShowMessageBoxOnError. 798 if (DieOnSafepointTimeout) { 799 char msg[1024]; 800 VM_Operation *op = VMThread::vm_operation(); 801 sprintf(msg, "Safepoint sync time longer than " INTX_FORMAT "ms detected when executing %s.", 802 SafepointTimeoutDelay, 803 op != NULL ? op->name() : "no vm operation"); 804 fatal(msg); 805 } 806} 807 808 809// ------------------------------------------------------------------------------------------------------- 810// Implementation of ThreadSafepointState 811 812ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { 813 _thread = thread; 814 _type = _running; 815 _has_called_back = false; 816 _at_poll_safepoint = false; 817} 818 819void ThreadSafepointState::create(JavaThread *thread) { 820 ThreadSafepointState *state = new ThreadSafepointState(thread); 821 thread->set_safepoint_state(state); 822} 823 824void ThreadSafepointState::destroy(JavaThread *thread) { 825 if (thread->safepoint_state()) { 826 delete(thread->safepoint_state()); 827 thread->set_safepoint_state(NULL); 828 } 829} 830 831void ThreadSafepointState::examine_state_of_thread() { 832 assert(is_running(), "better be running or just have hit safepoint poll"); 833 834 JavaThreadState state = _thread->thread_state(); 835 836 // Save the state at the start of safepoint processing. 837 _orig_thread_state = state; 838 839 // Check for a thread that is suspended. Note that thread resume tries 840 // to grab the Threads_lock which we own here, so a thread cannot be 841 // resumed during safepoint synchronization. 842 843 // We check to see if this thread is suspended without locking to 844 // avoid deadlocking with a third thread that is waiting for this 845 // thread to be suspended. The third thread can notice the safepoint 846 // that we're trying to start at the beginning of its SR_lock->wait() 847 // call. If that happens, then the third thread will block on the 848 // safepoint while still holding the underlying SR_lock. We won't be 849 // able to get the SR_lock and we'll deadlock. 850 // 851 // We don't need to grab the SR_lock here for two reasons: 852 // 1) The suspend flags are both volatile and are set with an 853 // Atomic::cmpxchg() call so we should see the suspended 854 // state right away. 855 // 2) We're being called from the safepoint polling loop; if 856 // we don't see the suspended state on this iteration, then 857 // we'll come around again. 858 // 859 bool is_suspended = _thread->is_ext_suspended(); 860 if (is_suspended) { 861 roll_forward(_at_safepoint); 862 return; 863 } 864 865 // Some JavaThread states have an initial safepoint state of 866 // running, but are actually at a safepoint. We will happily 867 // agree and update the safepoint state here. 868 if (SafepointSynchronize::safepoint_safe(_thread, state)) { 869 SafepointSynchronize::check_for_lazy_critical_native(_thread, state); 870 roll_forward(_at_safepoint); 871 return; 872 } 873 874 if (state == _thread_in_vm) { 875 roll_forward(_call_back); 876 return; 877 } 878 879 // All other thread states will continue to run until they 880 // transition and self-block in state _blocked 881 // Safepoint polling in compiled code causes the Java threads to do the same. 882 // Note: new threads may require a malloc so they must be allowed to finish 883 884 assert(is_running(), "examine_state_of_thread on non-running thread"); 885 return; 886} 887 888// Returns true is thread could not be rolled forward at present position. 889void ThreadSafepointState::roll_forward(suspend_type type) { 890 _type = type; 891 892 switch(_type) { 893 case _at_safepoint: 894 SafepointSynchronize::signal_thread_at_safepoint(); 895 DEBUG_ONLY(_thread->set_visited_for_critical_count(true)); 896 if (_thread->in_critical()) { 897 // Notice that this thread is in a critical section 898 SafepointSynchronize::increment_jni_active_count(); 899 } 900 break; 901 902 case _call_back: 903 set_has_called_back(false); 904 break; 905 906 case _running: 907 default: 908 ShouldNotReachHere(); 909 } 910} 911 912void ThreadSafepointState::restart() { 913 switch(type()) { 914 case _at_safepoint: 915 case _call_back: 916 break; 917 918 case _running: 919 default: 920 tty->print_cr("restart thread "INTPTR_FORMAT" with state %d", 921 _thread, _type); 922 _thread->print(); 923 ShouldNotReachHere(); 924 } 925 _type = _running; 926 set_has_called_back(false); 927} 928 929 930void ThreadSafepointState::print_on(outputStream *st) const { 931 const char *s; 932 933 switch(_type) { 934 case _running : s = "_running"; break; 935 case _at_safepoint : s = "_at_safepoint"; break; 936 case _call_back : s = "_call_back"; break; 937 default: 938 ShouldNotReachHere(); 939 } 940 941 st->print_cr("Thread: " INTPTR_FORMAT 942 " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", 943 _thread, _thread->osthread()->thread_id(), s, _has_called_back, 944 _at_poll_safepoint); 945 946 _thread->print_thread_state_on(st); 947} 948 949 950// --------------------------------------------------------------------------------------------------------------------- 951 952// Block the thread at the safepoint poll or poll return. 953void ThreadSafepointState::handle_polling_page_exception() { 954 955 // Check state. block() will set thread state to thread_in_vm which will 956 // cause the safepoint state _type to become _call_back. 957 assert(type() == ThreadSafepointState::_running, 958 "polling page exception on thread not running state"); 959 960 // Step 1: Find the nmethod from the return address 961 if (ShowSafepointMsgs && Verbose) { 962 tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); 963 } 964 address real_return_addr = thread()->saved_exception_pc(); 965 966 CodeBlob *cb = CodeCache::find_blob(real_return_addr); 967 assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); 968 nmethod* nm = (nmethod*)cb; 969 970 // Find frame of caller 971 frame stub_fr = thread()->last_frame(); 972 CodeBlob* stub_cb = stub_fr.cb(); 973 assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); 974 RegisterMap map(thread(), true); 975 frame caller_fr = stub_fr.sender(&map); 976 977 // Should only be poll_return or poll 978 assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); 979 980 // This is a poll immediately before a return. The exception handling code 981 // has already had the effect of causing the return to occur, so the execution 982 // will continue immediately after the call. In addition, the oopmap at the 983 // return point does not mark the return value as an oop (if it is), so 984 // it needs a handle here to be updated. 985 if( nm->is_at_poll_return(real_return_addr) ) { 986 // See if return type is an oop. 987 bool return_oop = nm->method()->is_returning_oop(); 988 Handle return_value; 989 if (return_oop) { 990 // The oop result has been saved on the stack together with all 991 // the other registers. In order to preserve it over GCs we need 992 // to keep it in a handle. 993 oop result = caller_fr.saved_oop_result(&map); 994 assert(result == NULL || result->is_oop(), "must be oop"); 995 return_value = Handle(thread(), result); 996 assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); 997 } 998 999 // Block the thread 1000 SafepointSynchronize::block(thread()); 1001 1002 // restore oop result, if any 1003 if (return_oop) { 1004 caller_fr.set_saved_oop_result(&map, return_value()); 1005 } 1006 } 1007 1008 // This is a safepoint poll. Verify the return address and block. 1009 else { 1010 set_at_poll_safepoint(true); 1011 1012 // verify the blob built the "return address" correctly 1013 assert(real_return_addr == caller_fr.pc(), "must match"); 1014 1015 // Block the thread 1016 SafepointSynchronize::block(thread()); 1017 set_at_poll_safepoint(false); 1018 1019 // If we have a pending async exception deoptimize the frame 1020 // as otherwise we may never deliver it. 1021 if (thread()->has_async_condition()) { 1022 ThreadInVMfromJavaNoAsyncException __tiv(thread()); 1023 Deoptimization::deoptimize_frame(thread(), caller_fr.id()); 1024 } 1025 1026 // If an exception has been installed we must check for a pending deoptimization 1027 // Deoptimize frame if exception has been thrown. 1028 1029 if (thread()->has_pending_exception() ) { 1030 RegisterMap map(thread(), true); 1031 frame caller_fr = stub_fr.sender(&map); 1032 if (caller_fr.is_deoptimized_frame()) { 1033 // The exception patch will destroy registers that are still 1034 // live and will be needed during deoptimization. Defer the 1035 // Async exception should have deferred the exception until the 1036 // next safepoint which will be detected when we get into 1037 // the interpreter so if we have an exception now things 1038 // are messed up. 1039 1040 fatal("Exception installed and deoptimization is pending"); 1041 } 1042 } 1043 } 1044} 1045 1046 1047// 1048// Statistics & Instrumentations 1049// 1050SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; 1051jlong SafepointSynchronize::_safepoint_begin_time = 0; 1052int SafepointSynchronize::_cur_stat_index = 0; 1053julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; 1054julong SafepointSynchronize::_coalesced_vmop_count = 0; 1055jlong SafepointSynchronize::_max_sync_time = 0; 1056jlong SafepointSynchronize::_max_vmop_time = 0; 1057float SafepointSynchronize::_ts_of_current_safepoint = 0.0f; 1058 1059static jlong cleanup_end_time = 0; 1060static bool need_to_track_page_armed_status = false; 1061static bool init_done = false; 1062 1063// Helper method to print the header. 1064static void print_header() { 1065 tty->print(" vmop " 1066 "[threads: total initially_running wait_to_block] "); 1067 tty->print("[time: spin block sync cleanup vmop] "); 1068 1069 // no page armed status printed out if it is always armed. 1070 if (need_to_track_page_armed_status) { 1071 tty->print("page_armed "); 1072 } 1073 1074 tty->print_cr("page_trap_count"); 1075} 1076 1077void SafepointSynchronize::deferred_initialize_stat() { 1078 if (init_done) return; 1079 1080 if (PrintSafepointStatisticsCount <= 0) { 1081 fatal("Wrong PrintSafepointStatisticsCount"); 1082 } 1083 1084 // If PrintSafepointStatisticsTimeout is specified, the statistics data will 1085 // be printed right away, in which case, _safepoint_stats will regress to 1086 // a single element array. Otherwise, it is a circular ring buffer with default 1087 // size of PrintSafepointStatisticsCount. 1088 int stats_array_size; 1089 if (PrintSafepointStatisticsTimeout > 0) { 1090 stats_array_size = 1; 1091 PrintSafepointStatistics = true; 1092 } else { 1093 stats_array_size = PrintSafepointStatisticsCount; 1094 } 1095 _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size 1096 * sizeof(SafepointStats), mtInternal); 1097 guarantee(_safepoint_stats != NULL, 1098 "not enough memory for safepoint instrumentation data"); 1099 1100 if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) { 1101 need_to_track_page_armed_status = true; 1102 } 1103 init_done = true; 1104} 1105 1106void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { 1107 assert(init_done, "safepoint statistics array hasn't been initialized"); 1108 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1109 1110 spstat->_time_stamp = _ts_of_current_safepoint; 1111 1112 VM_Operation *op = VMThread::vm_operation(); 1113 spstat->_vmop_type = (op != NULL ? op->type() : -1); 1114 if (op != NULL) { 1115 _safepoint_reasons[spstat->_vmop_type]++; 1116 } 1117 1118 spstat->_nof_total_threads = nof_threads; 1119 spstat->_nof_initial_running_threads = nof_running; 1120 spstat->_nof_threads_hit_page_trap = 0; 1121 1122 // Records the start time of spinning. The real time spent on spinning 1123 // will be adjusted when spin is done. Same trick is applied for time 1124 // spent on waiting for threads to block. 1125 if (nof_running != 0) { 1126 spstat->_time_to_spin = os::javaTimeNanos(); 1127 } else { 1128 spstat->_time_to_spin = 0; 1129 } 1130} 1131 1132void SafepointSynchronize::update_statistics_on_spin_end() { 1133 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1134 1135 jlong cur_time = os::javaTimeNanos(); 1136 1137 spstat->_nof_threads_wait_to_block = _waiting_to_block; 1138 if (spstat->_nof_initial_running_threads != 0) { 1139 spstat->_time_to_spin = cur_time - spstat->_time_to_spin; 1140 } 1141 1142 if (need_to_track_page_armed_status) { 1143 spstat->_page_armed = (PageArmed == 1); 1144 } 1145 1146 // Records the start time of waiting for to block. Updated when block is done. 1147 if (_waiting_to_block != 0) { 1148 spstat->_time_to_wait_to_block = cur_time; 1149 } else { 1150 spstat->_time_to_wait_to_block = 0; 1151 } 1152} 1153 1154void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { 1155 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1156 1157 if (spstat->_nof_threads_wait_to_block != 0) { 1158 spstat->_time_to_wait_to_block = end_time - 1159 spstat->_time_to_wait_to_block; 1160 } 1161 1162 // Records the end time of sync which will be used to calculate the total 1163 // vm operation time. Again, the real time spending in syncing will be deducted 1164 // from the start of the sync time later when end_statistics is called. 1165 spstat->_time_to_sync = end_time - _safepoint_begin_time; 1166 if (spstat->_time_to_sync > _max_sync_time) { 1167 _max_sync_time = spstat->_time_to_sync; 1168 } 1169 1170 spstat->_time_to_do_cleanups = end_time; 1171} 1172 1173void SafepointSynchronize::update_statistics_on_cleanup_end(jlong end_time) { 1174 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1175 1176 // Record how long spent in cleanup tasks. 1177 spstat->_time_to_do_cleanups = end_time - spstat->_time_to_do_cleanups; 1178 1179 cleanup_end_time = end_time; 1180} 1181 1182void SafepointSynchronize::end_statistics(jlong vmop_end_time) { 1183 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1184 1185 // Update the vm operation time. 1186 spstat->_time_to_exec_vmop = vmop_end_time - cleanup_end_time; 1187 if (spstat->_time_to_exec_vmop > _max_vmop_time) { 1188 _max_vmop_time = spstat->_time_to_exec_vmop; 1189 } 1190 // Only the sync time longer than the specified 1191 // PrintSafepointStatisticsTimeout will be printed out right away. 1192 // By default, it is -1 meaning all samples will be put into the list. 1193 if ( PrintSafepointStatisticsTimeout > 0) { 1194 if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1195 print_statistics(); 1196 } 1197 } else { 1198 // The safepoint statistics will be printed out when the _safepoin_stats 1199 // array fills up. 1200 if (_cur_stat_index == PrintSafepointStatisticsCount - 1) { 1201 print_statistics(); 1202 _cur_stat_index = 0; 1203 } else { 1204 _cur_stat_index++; 1205 } 1206 } 1207} 1208 1209void SafepointSynchronize::print_statistics() { 1210 SafepointStats* sstats = _safepoint_stats; 1211 1212 for (int index = 0; index <= _cur_stat_index; index++) { 1213 if (index % 30 == 0) { 1214 print_header(); 1215 } 1216 sstats = &_safepoint_stats[index]; 1217 tty->print("%.3f: ", sstats->_time_stamp); 1218 tty->print("%-26s [" 1219 INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15) 1220 " ] ", 1221 sstats->_vmop_type == -1 ? "no vm operation" : 1222 VM_Operation::name(sstats->_vmop_type), 1223 sstats->_nof_total_threads, 1224 sstats->_nof_initial_running_threads, 1225 sstats->_nof_threads_wait_to_block); 1226 // "/ MICROUNITS " is to convert the unit from nanos to millis. 1227 tty->print(" [" 1228 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1229 INT64_FORMAT_W(6)INT64_FORMAT_W(6) 1230 INT64_FORMAT_W(6)" ] ", 1231 sstats->_time_to_spin / MICROUNITS, 1232 sstats->_time_to_wait_to_block / MICROUNITS, 1233 sstats->_time_to_sync / MICROUNITS, 1234 sstats->_time_to_do_cleanups / MICROUNITS, 1235 sstats->_time_to_exec_vmop / MICROUNITS); 1236 1237 if (need_to_track_page_armed_status) { 1238 tty->print(INT32_FORMAT" ", sstats->_page_armed); 1239 } 1240 tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap); 1241 } 1242} 1243 1244// This method will be called when VM exits. It will first call 1245// print_statistics to print out the rest of the sampling. Then 1246// it tries to summarize the sampling. 1247void SafepointSynchronize::print_stat_on_exit() { 1248 if (_safepoint_stats == NULL) return; 1249 1250 SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; 1251 1252 // During VM exit, end_statistics may not get called and in that 1253 // case, if the sync time is less than PrintSafepointStatisticsTimeout, 1254 // don't print it out. 1255 // Approximate the vm op time. 1256 _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = 1257 os::javaTimeNanos() - cleanup_end_time; 1258 1259 if ( PrintSafepointStatisticsTimeout < 0 || 1260 spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { 1261 print_statistics(); 1262 } 1263 tty->cr(); 1264 1265 // Print out polling page sampling status. 1266 if (!need_to_track_page_armed_status) { 1267 if (UseCompilerSafepoints) { 1268 tty->print_cr("Polling page always armed"); 1269 } 1270 } else { 1271 tty->print_cr("Defer polling page loop count = %d\n", 1272 DeferPollingPageLoopCount); 1273 } 1274 1275 for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { 1276 if (_safepoint_reasons[index] != 0) { 1277 tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index), 1278 _safepoint_reasons[index]); 1279 } 1280 } 1281 1282 tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint", 1283 _coalesced_vmop_count); 1284 tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms", 1285 _max_sync_time / MICROUNITS); 1286 tty->print_cr("Maximum vm operation time (except for Exit VM operation) " 1287 INT64_FORMAT_W(5)" ms", 1288 _max_vmop_time / MICROUNITS); 1289} 1290 1291// ------------------------------------------------------------------------------------------------ 1292// Non-product code 1293 1294#ifndef PRODUCT 1295 1296void SafepointSynchronize::print_state() { 1297 if (_state == _not_synchronized) { 1298 tty->print_cr("not synchronized"); 1299 } else if (_state == _synchronizing || _state == _synchronized) { 1300 tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : 1301 "synchronized"); 1302 1303 for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { 1304 cur->safepoint_state()->print(); 1305 } 1306 } 1307} 1308 1309void SafepointSynchronize::safepoint_msg(const char* format, ...) { 1310 if (ShowSafepointMsgs) { 1311 va_list ap; 1312 va_start(ap, format); 1313 tty->vprint_cr(format, ap); 1314 va_end(ap); 1315 } 1316} 1317 1318#endif // !PRODUCT 1319