Mercurial > hg > truffle
diff src/share/vm/runtime/safepoint.cpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | 2328d1d3f8cf |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/runtime/safepoint.cpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,1215 @@ +/* + * Copyright 1997-2007 Sun Microsystems, Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +# include "incls/_precompiled.incl" +# include "incls/_safepoint.cpp.incl" + +// -------------------------------------------------------------------------------------------------- +// Implementation of Safepoint begin/end + +SafepointSynchronize::SynchronizeState volatile SafepointSynchronize::_state = SafepointSynchronize::_not_synchronized; +volatile int SafepointSynchronize::_waiting_to_block = 0; +jlong SafepointSynchronize::_last_safepoint = 0; +volatile int SafepointSynchronize::_safepoint_counter = 0; +static volatile int PageArmed = 0 ; // safepoint polling page is RO|RW vs PROT_NONE +static volatile int TryingToBlock = 0 ; // proximate value -- for advisory use only +static bool timeout_error_printed = false; + +// Roll all threads forward to a safepoint and suspend them all +void SafepointSynchronize::begin() { + + Thread* myThread = Thread::current(); + assert(myThread->is_VM_thread(), "Only VM thread may execute a safepoint"); + + _last_safepoint = os::javaTimeNanos(); + +#ifndef SERIALGC + if (UseConcMarkSweepGC) { + // In the future we should investigate whether CMS can use the + // more-general mechanism below. DLD (01/05). + ConcurrentMarkSweepThread::synchronize(false); + } else { + ConcurrentGCThread::safepoint_synchronize(); + } +#endif // SERIALGC + + // By getting the Threads_lock, we assure that no threads are about to start or + // exit. It is released again in SafepointSynchronize::end(). + Threads_lock->lock(); + + assert( _state == _not_synchronized, "trying to safepoint synchronize with wrong state"); + + int nof_threads = Threads::number_of_threads(); + + if (TraceSafepoint) { + tty->print_cr("Safepoint synchronization initiated. (%d)", nof_threads); + } + + RuntimeService::record_safepoint_begin(); + + { + MutexLocker mu(Safepoint_lock); + + // Set number of threads to wait for, before we initiate the callbacks + _waiting_to_block = nof_threads; + TryingToBlock = 0 ; + int still_running = nof_threads; + + // Save the starting time, so that it can be compared to see if this has taken + // too long to complete. + jlong safepoint_limit_time; + timeout_error_printed = false; + + // Begin the process of bringing the system to a safepoint. + // Java threads can be in several different states and are + // stopped by different mechanisms: + // + // 1. Running interpreted + // The interpeter dispatch table is changed to force it to + // check for a safepoint condition between bytecodes. + // 2. Running in native code + // When returning from the native code, a Java thread must check + // the safepoint _state to see if we must block. If the + // VM thread sees a Java thread in native, it does + // not wait for this thread to block. The order of the memory + // writes and reads of both the safepoint state and the Java + // threads state is critical. In order to guarantee that the + // memory writes are serialized with respect to each other, + // the VM thread issues a memory barrier instruction + // (on MP systems). In order to avoid the overhead of issuing + // a memory barrier for each Java thread making native calls, each Java + // thread performs a write to a single memory page after changing + // the thread state. The VM thread performs a sequence of + // mprotect OS calls which forces all previous writes from all + // Java threads to be serialized. This is done in the + // os::serialize_thread_states() call. This has proven to be + // much more efficient than executing a membar instruction + // on every call to native code. + // 3. Running compiled Code + // Compiled code reads a global (Safepoint Polling) page that + // is set to fault if we are trying to get to a safepoint. + // 4. Blocked + // A thread which is blocked will not be allowed to return from the + // block condition until the safepoint operation is complete. + // 5. In VM or Transitioning between states + // If a Java thread is currently running in the VM or transitioning + // between states, the safepointing code will wait for the thread to + // block itself when it attempts transitions to a new state. + // + _state = _synchronizing; + OrderAccess::fence(); + + // Flush all thread states to memory + if (!UseMembar) { + os::serialize_thread_states(); + } + + // Make interpreter safepoint aware + Interpreter::notice_safepoints(); + + if (UseCompilerSafepoints && DeferPollingPageLoopCount < 0) { + // Make polling safepoint aware + guarantee (PageArmed == 0, "invariant") ; + PageArmed = 1 ; + os::make_polling_page_unreadable(); + } + + // Consider using active_processor_count() ... but that call is expensive. + int ncpus = os::processor_count() ; + +#ifdef ASSERT + for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { + assert(cur->safepoint_state()->is_running(), "Illegal initial state"); + } +#endif // ASSERT + + if (SafepointTimeout) + safepoint_limit_time = os::javaTimeNanos() + (jlong)SafepointTimeoutDelay * MICROUNITS; + + // Iterate through all threads until it have been determined how to stop them all at a safepoint + unsigned int iterations = 0; + int steps = 0 ; + while(still_running > 0) { + for (JavaThread *cur = Threads::first(); cur != NULL; cur = cur->next()) { + assert(!cur->is_ConcurrentGC_thread(), "A concurrent GC thread is unexpectly being suspended"); + ThreadSafepointState *cur_state = cur->safepoint_state(); + if (cur_state->is_running()) { + cur_state->examine_state_of_thread(); + if (!cur_state->is_running()) { + still_running--; + // consider adjusting steps downward: + // steps = 0 + // steps -= NNN + // steps >>= 1 + // steps = MIN(steps, 2000-100) + // if (iterations != 0) steps -= NNN + } + if (TraceSafepoint && Verbose) cur_state->print(); + } + } + + if ( (PrintSafepointStatistics || (PrintSafepointStatisticsTimeout > 0)) + && iterations == 0) { + begin_statistics(nof_threads, still_running); + } + + if (still_running > 0) { + // Check for if it takes to long + if (SafepointTimeout && safepoint_limit_time < os::javaTimeNanos()) { + print_safepoint_timeout(_spinning_timeout); + } + + // Spin to avoid context switching. + // There's a tension between allowing the mutators to run (and rendezvous) + // vs spinning. As the VM thread spins, wasting cycles, it consumes CPU that + // a mutator might otherwise use profitably to reach a safepoint. Excessive + // spinning by the VM thread on a saturated system can increase rendezvous latency. + // Blocking or yielding incur their own penalties in the form of context switching + // and the resultant loss of $ residency. + // + // Further complicating matters is that yield() does not work as naively expected + // on many platforms -- yield() does not guarantee that any other ready threads + // will run. As such we revert yield_all() after some number of iterations. + // Yield_all() is implemented as a short unconditional sleep on some platforms. + // Typical operating systems round a "short" sleep period up to 10 msecs, so sleeping + // can actually increase the time it takes the VM thread to detect that a system-wide + // stop-the-world safepoint has been reached. In a pathological scenario such as that + // described in CR6415670 the VMthread may sleep just before the mutator(s) become safe. + // In that case the mutators will be stalled waiting for the safepoint to complete and the + // the VMthread will be sleeping, waiting for the mutators to rendezvous. The VMthread + // will eventually wake up and detect that all mutators are safe, at which point + // we'll again make progress. + // + // Beware too that that the VMThread typically runs at elevated priority. + // Its default priority is higher than the default mutator priority. + // Obviously, this complicates spinning. + // + // Note too that on Windows XP SwitchThreadTo() has quite different behavior than Sleep(0). + // Sleep(0) will _not yield to lower priority threads, while SwitchThreadTo() will. + // + // See the comments in synchronizer.cpp for additional remarks on spinning. + // + // In the future we might: + // 1. Modify the safepoint scheme to avoid potentally unbounded spinning. + // This is tricky as the path used by a thread exiting the JVM (say on + // on JNI call-out) simply stores into its state field. The burden + // is placed on the VM thread, which must poll (spin). + // 2. Find something useful to do while spinning. If the safepoint is GC-related + // we might aggressively scan the stacks of threads that are already safe. + // 3. Use Solaris schedctl to examine the state of the still-running mutators. + // If all the mutators are ONPROC there's no reason to sleep or yield. + // 4. YieldTo() any still-running mutators that are ready but OFFPROC. + // 5. Check system saturation. If the system is not fully saturated then + // simply spin and avoid sleep/yield. + // 6. As still-running mutators rendezvous they could unpark the sleeping + // VMthread. This works well for still-running mutators that become + // safe. The VMthread must still poll for mutators that call-out. + // 7. Drive the policy on time-since-begin instead of iterations. + // 8. Consider making the spin duration a function of the # of CPUs: + // Spin = (((ncpus-1) * M) + K) + F(still_running) + // Alternately, instead of counting iterations of the outer loop + // we could count the # of threads visited in the inner loop, above. + // 9. On windows consider using the return value from SwitchThreadTo() + // to drive subsequent spin/SwitchThreadTo()/Sleep(N) decisions. + + if (UseCompilerSafepoints && int(iterations) == DeferPollingPageLoopCount) { + guarantee (PageArmed == 0, "invariant") ; + PageArmed = 1 ; + os::make_polling_page_unreadable(); + } + + // Instead of (ncpus > 1) consider either (still_running < (ncpus + EPSILON)) or + // ((still_running + _waiting_to_block - TryingToBlock)) < ncpus) + ++steps ; + if (ncpus > 1 && steps < SafepointSpinBeforeYield) { + SpinPause() ; // MP-Polite spin + } else + if (steps < DeferThrSuspendLoopCount) { + os::NakedYield() ; + } else { + os::yield_all(steps) ; + // Alternately, the VM thread could transiently depress its scheduling priority or + // transiently increase the priority of the tardy mutator(s). + } + + iterations ++ ; + } + assert(iterations < (uint)max_jint, "We have been iterating in the safepoint loop too long"); + } + assert(still_running == 0, "sanity check"); + + if (PrintSafepointStatistics) { + update_statistics_on_spin_end(); + } + + // wait until all threads are stopped + while (_waiting_to_block > 0) { + if (TraceSafepoint) tty->print_cr("Waiting for %d thread(s) to block", _waiting_to_block); + if (!SafepointTimeout || timeout_error_printed) { + Safepoint_lock->wait(true); // true, means with no safepoint checks + } else { + // Compute remaining time + jlong remaining_time = safepoint_limit_time - os::javaTimeNanos(); + + // If there is no remaining time, then there is an error + if (remaining_time < 0 || Safepoint_lock->wait(true, remaining_time / MICROUNITS)) { + print_safepoint_timeout(_blocking_timeout); + } + } + } + assert(_waiting_to_block == 0, "sanity check"); + +#ifndef PRODUCT + if (SafepointTimeout) { + jlong current_time = os::javaTimeNanos(); + if (safepoint_limit_time < current_time) { + tty->print_cr("# SafepointSynchronize: Finished after " + INT64_FORMAT_W(6) " ms", + ((current_time - safepoint_limit_time) / MICROUNITS + + SafepointTimeoutDelay)); + } + } +#endif + + assert((_safepoint_counter & 0x1) == 0, "must be even"); + assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); + _safepoint_counter ++; + + // Record state + _state = _synchronized; + + OrderAccess::fence(); + + if (TraceSafepoint) { + VM_Operation *op = VMThread::vm_operation(); + tty->print_cr("Entering safepoint region: %s", (op != NULL) ? op->name() : "no vm operation"); + } + + RuntimeService::record_safepoint_synchronized(); + if (PrintSafepointStatistics) { + update_statistics_on_sync_end(os::javaTimeNanos()); + } + + // Call stuff that needs to be run when a safepoint is just about to be completed + do_cleanup_tasks(); + } +} + +// Wake up all threads, so they are ready to resume execution after the safepoint +// operation has been carried out +void SafepointSynchronize::end() { + + assert(Threads_lock->owned_by_self(), "must hold Threads_lock"); + assert((_safepoint_counter & 0x1) == 1, "must be odd"); + _safepoint_counter ++; + // memory fence isn't required here since an odd _safepoint_counter + // value can do no harm and a fence is issued below anyway. + + DEBUG_ONLY(Thread* myThread = Thread::current();) + assert(myThread->is_VM_thread(), "Only VM thread can execute a safepoint"); + + if (PrintSafepointStatistics) { + end_statistics(os::javaTimeNanos()); + } + +#ifdef ASSERT + // A pending_exception cannot be installed during a safepoint. The threads + // may install an async exception after they come back from a safepoint into + // pending_exception after they unblock. But that should happen later. + for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { + assert (!(cur->has_pending_exception() && + cur->safepoint_state()->is_at_poll_safepoint()), + "safepoint installed a pending exception"); + } +#endif // ASSERT + + if (PageArmed) { + // Make polling safepoint aware + os::make_polling_page_readable(); + PageArmed = 0 ; + } + + // Remove safepoint check from interpreter + Interpreter::ignore_safepoints(); + + { + MutexLocker mu(Safepoint_lock); + + assert(_state == _synchronized, "must be synchronized before ending safepoint synchronization"); + + // Set to not synchronized, so the threads will not go into the signal_thread_blocked method + // when they get restarted. + _state = _not_synchronized; + OrderAccess::fence(); + + if (TraceSafepoint) { + tty->print_cr("Leaving safepoint region"); + } + + // Start suspended threads + for(JavaThread *current = Threads::first(); current; current = current->next()) { + // A problem occuring on Solaris is when attempting to restart threads + // the first #cpus - 1 go well, but then the VMThread is preempted when we get + // to the next one (since it has been running the longest). We then have + // to wait for a cpu to become available before we can continue restarting + // threads. + // FIXME: This causes the performance of the VM to degrade when active and with + // large numbers of threads. Apparently this is due to the synchronous nature + // of suspending threads. + // + // TODO-FIXME: the comments above are vestigial and no longer apply. + // Furthermore, using solaris' schedctl in this particular context confers no benefit + if (VMThreadHintNoPreempt) { + os::hint_no_preempt(); + } + ThreadSafepointState* cur_state = current->safepoint_state(); + assert(cur_state->type() != ThreadSafepointState::_running, "Thread not suspended at safepoint"); + cur_state->restart(); + assert(cur_state->is_running(), "safepoint state has not been reset"); + } + + RuntimeService::record_safepoint_end(); + + // Release threads lock, so threads can be created/destroyed again. It will also starts all threads + // blocked in signal_thread_blocked + Threads_lock->unlock(); + + } +#ifndef SERIALGC + // If there are any concurrent GC threads resume them. + if (UseConcMarkSweepGC) { + ConcurrentMarkSweepThread::desynchronize(false); + } else { + ConcurrentGCThread::safepoint_desynchronize(); + } +#endif // SERIALGC +} + +bool SafepointSynchronize::is_cleanup_needed() { + // Need a safepoint if some inline cache buffers is non-empty + if (!InlineCacheBuffer::is_empty()) return true; + return false; +} + +jlong CounterDecay::_last_timestamp = 0; + +static void do_method(methodOop m) { + m->invocation_counter()->decay(); +} + +void CounterDecay::decay() { + _last_timestamp = os::javaTimeMillis(); + + // This operation is going to be performed only at the end of a safepoint + // and hence GC's will not be going on, all Java mutators are suspended + // at this point and hence SystemDictionary_lock is also not needed. + assert(SafepointSynchronize::is_at_safepoint(), "can only be executed at a safepoint"); + int nclasses = SystemDictionary::number_of_classes(); + double classes_per_tick = nclasses * (CounterDecayMinIntervalLength * 1e-3 / + CounterHalfLifeTime); + for (int i = 0; i < classes_per_tick; i++) { + klassOop k = SystemDictionary::try_get_next_class(); + if (k != NULL && k->klass_part()->oop_is_instance()) { + instanceKlass::cast(k)->methods_do(do_method); + } + } +} + +// Various cleaning tasks that should be done periodically at safepoints +void SafepointSynchronize::do_cleanup_tasks() { + jlong cleanup_time; + + // Update fat-monitor pool, since this is a safepoint. + if (TraceSafepoint) { + cleanup_time = os::javaTimeNanos(); + } + + ObjectSynchronizer::deflate_idle_monitors(); + InlineCacheBuffer::update_inline_caches(); + if(UseCounterDecay && CounterDecay::is_decay_needed()) { + CounterDecay::decay(); + } + NMethodSweeper::sweep(); + + if (TraceSafepoint) { + tty->print_cr("do_cleanup_tasks takes "INT64_FORMAT_W(6) "ms", + (os::javaTimeNanos() - cleanup_time) / MICROUNITS); + } +} + + +bool SafepointSynchronize::safepoint_safe(JavaThread *thread, JavaThreadState state) { + switch(state) { + case _thread_in_native: + // native threads are safe if they have no java stack or have walkable stack + return !thread->has_last_Java_frame() || thread->frame_anchor()->walkable(); + + // blocked threads should have already have walkable stack + case _thread_blocked: + assert(!thread->has_last_Java_frame() || thread->frame_anchor()->walkable(), "blocked and not walkable"); + return true; + + default: + return false; + } +} + + +// ------------------------------------------------------------------------------------------------------- +// Implementation of Safepoint callback point + +void SafepointSynchronize::block(JavaThread *thread) { + assert(thread != NULL, "thread must be set"); + assert(thread->is_Java_thread(), "not a Java thread"); + + // Threads shouldn't block if they are in the middle of printing, but... + ttyLocker::break_tty_lock_for_safepoint(os::current_thread_id()); + + // Only bail from the block() call if the thread is gone from the + // thread list; starting to exit should still block. + if (thread->is_terminated()) { + // block current thread if we come here from native code when VM is gone + thread->block_if_vm_exited(); + + // otherwise do nothing + return; + } + + JavaThreadState state = thread->thread_state(); + thread->frame_anchor()->make_walkable(thread); + + // Check that we have a valid thread_state at this point + switch(state) { + case _thread_in_vm_trans: + case _thread_in_Java: // From compiled code + + // We are highly likely to block on the Safepoint_lock. In order to avoid blocking in this case, + // we pretend we are still in the VM. + thread->set_thread_state(_thread_in_vm); + + if (is_synchronizing()) { + Atomic::inc (&TryingToBlock) ; + } + + // We will always be holding the Safepoint_lock when we are examine the state + // of a thread. Hence, the instructions between the Safepoint_lock->lock() and + // Safepoint_lock->unlock() are happening atomic with regards to the safepoint code + Safepoint_lock->lock_without_safepoint_check(); + if (is_synchronizing()) { + // Decrement the number of threads to wait for and signal vm thread + assert(_waiting_to_block > 0, "sanity check"); + _waiting_to_block--; + thread->safepoint_state()->set_has_called_back(true); + + // Consider (_waiting_to_block < 2) to pipeline the wakeup of the VM thread + if (_waiting_to_block == 0) { + Safepoint_lock->notify_all(); + } + } + + // We transition the thread to state _thread_blocked here, but + // we can't do our usual check for external suspension and then + // self-suspend after the lock_without_safepoint_check() call + // below because we are often called during transitions while + // we hold different locks. That would leave us suspended while + // holding a resource which results in deadlocks. + thread->set_thread_state(_thread_blocked); + Safepoint_lock->unlock(); + + // We now try to acquire the threads lock. Since this lock is hold by the VM thread during + // the entire safepoint, the threads will all line up here during the safepoint. + Threads_lock->lock_without_safepoint_check(); + // restore original state. This is important if the thread comes from compiled code, so it + // will continue to execute with the _thread_in_Java state. + thread->set_thread_state(state); + Threads_lock->unlock(); + break; + + case _thread_in_native_trans: + case _thread_blocked_trans: + case _thread_new_trans: + if (thread->safepoint_state()->type() == ThreadSafepointState::_call_back) { + thread->print_thread_state(); + fatal("Deadlock in safepoint code. " + "Should have called back to the VM before blocking."); + } + + // We transition the thread to state _thread_blocked here, but + // we can't do our usual check for external suspension and then + // self-suspend after the lock_without_safepoint_check() call + // below because we are often called during transitions while + // we hold different locks. That would leave us suspended while + // holding a resource which results in deadlocks. + thread->set_thread_state(_thread_blocked); + + // It is not safe to suspend a thread if we discover it is in _thread_in_native_trans. Hence, + // the safepoint code might still be waiting for it to block. We need to change the state here, + // so it can see that it is at a safepoint. + + // Block until the safepoint operation is completed. + Threads_lock->lock_without_safepoint_check(); + + // Restore state + thread->set_thread_state(state); + + Threads_lock->unlock(); + break; + + default: + fatal1("Illegal threadstate encountered: %d", state); + } + + // Check for pending. async. exceptions or suspends - except if the + // thread was blocked inside the VM. has_special_runtime_exit_condition() + // is called last since it grabs a lock and we only want to do that when + // we must. + // + // Note: we never deliver an async exception at a polling point as the + // compiler may not have an exception handler for it. The polling + // code will notice the async and deoptimize and the exception will + // be delivered. (Polling at a return point is ok though). Sure is + // a lot of bother for a deprecated feature... + // + // We don't deliver an async exception if the thread state is + // _thread_in_native_trans so JNI functions won't be called with + // a surprising pending exception. If the thread state is going back to java, + // async exception is checked in check_special_condition_for_native_trans(). + + if (state != _thread_blocked_trans && + state != _thread_in_vm_trans && + thread->has_special_runtime_exit_condition()) { + thread->handle_special_runtime_exit_condition( + !thread->is_at_poll_safepoint() && (state != _thread_in_native_trans)); + } +} + +// ------------------------------------------------------------------------------------------------------ +// Exception handlers + +#ifndef PRODUCT +#ifdef _LP64 +#define PTR_PAD "" +#else +#define PTR_PAD " " +#endif + +static void print_ptrs(intptr_t oldptr, intptr_t newptr, bool wasoop) { + bool is_oop = newptr ? ((oop)newptr)->is_oop() : false; + tty->print_cr(PTR_FORMAT PTR_PAD " %s %c " PTR_FORMAT PTR_PAD " %s %s", + oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', + newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); +} + +static void print_longs(jlong oldptr, jlong newptr, bool wasoop) { + bool is_oop = newptr ? ((oop)(intptr_t)newptr)->is_oop() : false; + tty->print_cr(PTR64_FORMAT " %s %c " PTR64_FORMAT " %s %s", + oldptr, wasoop?"oop":" ", oldptr == newptr ? ' ' : '!', + newptr, is_oop?"oop":" ", (wasoop && !is_oop) ? "STALE" : ((wasoop==false&&is_oop==false&&oldptr !=newptr)?"STOMP":" ")); +} + +#ifdef SPARC +static void print_me(intptr_t *new_sp, intptr_t *old_sp, bool *was_oops) { +#ifdef _LP64 + tty->print_cr("--------+------address-----+------before-----------+-------after----------+"); + const int incr = 1; // Increment to skip a long, in units of intptr_t +#else + tty->print_cr("--------+--address-+------before-----------+-------after----------+"); + const int incr = 2; // Increment to skip a long, in units of intptr_t +#endif + tty->print_cr("---SP---|"); + for( int i=0; i<16; i++ ) { + tty->print("blob %c%d |"PTR_FORMAT" ","LO"[i>>3],i&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } + tty->print_cr("--------|"); + for( int i1=0; i1<frame::memory_parameter_word_sp_offset-16; i1++ ) { + tty->print("argv pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } + tty->print(" pad|"PTR_FORMAT" ",new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); + tty->print_cr("--------|"); + tty->print(" G1 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; + tty->print(" G3 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; + tty->print(" G4 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; + tty->print(" G5 |"PTR_FORMAT" ",new_sp); print_longs(*(jlong*)old_sp,*(jlong*)new_sp,was_oops[incr-1]); old_sp += incr; new_sp += incr; was_oops += incr; + tty->print_cr(" FSR |"PTR_FORMAT" "PTR64_FORMAT" "PTR64_FORMAT,new_sp,*(jlong*)old_sp,*(jlong*)new_sp); + old_sp += incr; new_sp += incr; was_oops += incr; + // Skip the floats + tty->print_cr("--Float-|"PTR_FORMAT,new_sp); + tty->print_cr("---FP---|"); + old_sp += incr*32; new_sp += incr*32; was_oops += incr*32; + for( int i2=0; i2<16; i2++ ) { + tty->print("call %c%d |"PTR_FORMAT" ","LI"[i2>>3],i2&7,new_sp); print_ptrs(*old_sp++,*new_sp++,*was_oops++); } + tty->print_cr(""); +} +#endif // SPARC +#endif // PRODUCT + + +void SafepointSynchronize::handle_polling_page_exception(JavaThread *thread) { + assert(thread->is_Java_thread(), "polling reference encountered by VM thread"); + assert(thread->thread_state() == _thread_in_Java, "should come from Java code"); + assert(SafepointSynchronize::is_synchronizing(), "polling encountered outside safepoint synchronization"); + + // Uncomment this to get some serious before/after printing of the + // Sparc safepoint-blob frame structure. + /* + intptr_t* sp = thread->last_Java_sp(); + intptr_t stack_copy[150]; + for( int i=0; i<150; i++ ) stack_copy[i] = sp[i]; + bool was_oops[150]; + for( int i=0; i<150; i++ ) + was_oops[i] = stack_copy[i] ? ((oop)stack_copy[i])->is_oop() : false; + */ + + if (ShowSafepointMsgs) { + tty->print("handle_polling_page_exception: "); + } + + if (PrintSafepointStatistics) { + inc_page_trap_count(); + } + + ThreadSafepointState* state = thread->safepoint_state(); + + state->handle_polling_page_exception(); + // print_me(sp,stack_copy,was_oops); +} + + +void SafepointSynchronize::print_safepoint_timeout(SafepointTimeoutReason reason) { + if (!timeout_error_printed) { + timeout_error_printed = true; + // Print out the thread infor which didn't reach the safepoint for debugging + // purposes (useful when there are lots of threads in the debugger). + tty->print_cr(""); + tty->print_cr("# SafepointSynchronize::begin: Timeout detected:"); + if (reason == _spinning_timeout) { + tty->print_cr("# SafepointSynchronize::begin: Timed out while spinning to reach a safepoint."); + } else if (reason == _blocking_timeout) { + tty->print_cr("# SafepointSynchronize::begin: Timed out while waiting for threads to stop."); + } + + tty->print_cr("# SafepointSynchronize::begin: Threads which did not reach the safepoint:"); + ThreadSafepointState *cur_state; + ResourceMark rm; + for(JavaThread *cur_thread = Threads::first(); cur_thread; + cur_thread = cur_thread->next()) { + cur_state = cur_thread->safepoint_state(); + + if (cur_thread->thread_state() != _thread_blocked && + ((reason == _spinning_timeout && cur_state->is_running()) || + (reason == _blocking_timeout && !cur_state->has_called_back()))) { + tty->print("# "); + cur_thread->print(); + tty->print_cr(""); + } + } + tty->print_cr("# SafepointSynchronize::begin: (End of list)"); + } + + // To debug the long safepoint, specify both DieOnSafepointTimeout & + // ShowMessageBoxOnError. + if (DieOnSafepointTimeout) { + char msg[1024]; + VM_Operation *op = VMThread::vm_operation(); + sprintf(msg, "Safepoint sync time longer than %d ms detected when executing %s.", + SafepointTimeoutDelay, + op != NULL ? op->name() : "no vm operation"); + fatal(msg); + } +} + + +// ------------------------------------------------------------------------------------------------------- +// Implementation of ThreadSafepointState + +ThreadSafepointState::ThreadSafepointState(JavaThread *thread) { + _thread = thread; + _type = _running; + _has_called_back = false; + _at_poll_safepoint = false; +} + +void ThreadSafepointState::create(JavaThread *thread) { + ThreadSafepointState *state = new ThreadSafepointState(thread); + thread->set_safepoint_state(state); +} + +void ThreadSafepointState::destroy(JavaThread *thread) { + if (thread->safepoint_state()) { + delete(thread->safepoint_state()); + thread->set_safepoint_state(NULL); + } +} + +void ThreadSafepointState::examine_state_of_thread() { + assert(is_running(), "better be running or just have hit safepoint poll"); + + JavaThreadState state = _thread->thread_state(); + + // Check for a thread that is suspended. Note that thread resume tries + // to grab the Threads_lock which we own here, so a thread cannot be + // resumed during safepoint synchronization. + + // We check with locking because another thread that has not yet + // synchronized may be trying to suspend this one. + bool is_suspended = _thread->is_any_suspended_with_lock(); + if (is_suspended) { + roll_forward(_at_safepoint); + return; + } + + // Some JavaThread states have an initial safepoint state of + // running, but are actually at a safepoint. We will happily + // agree and update the safepoint state here. + if (SafepointSynchronize::safepoint_safe(_thread, state)) { + roll_forward(_at_safepoint); + return; + } + + if (state == _thread_in_vm) { + roll_forward(_call_back); + return; + } + + // All other thread states will continue to run until they + // transition and self-block in state _blocked + // Safepoint polling in compiled code causes the Java threads to do the same. + // Note: new threads may require a malloc so they must be allowed to finish + + assert(is_running(), "examine_state_of_thread on non-running thread"); + return; +} + +// Returns true is thread could not be rolled forward at present position. +void ThreadSafepointState::roll_forward(suspend_type type) { + _type = type; + + switch(_type) { + case _at_safepoint: + SafepointSynchronize::signal_thread_at_safepoint(); + break; + + case _call_back: + set_has_called_back(false); + break; + + case _running: + default: + ShouldNotReachHere(); + } +} + +void ThreadSafepointState::restart() { + switch(type()) { + case _at_safepoint: + case _call_back: + break; + + case _running: + default: + tty->print_cr("restart thread "INTPTR_FORMAT" with state %d", + _thread, _type); + _thread->print(); + ShouldNotReachHere(); + } + _type = _running; + set_has_called_back(false); +} + + +void ThreadSafepointState::print_on(outputStream *st) const { + const char *s; + + switch(_type) { + case _running : s = "_running"; break; + case _at_safepoint : s = "_at_safepoint"; break; + case _call_back : s = "_call_back"; break; + default: + ShouldNotReachHere(); + } + + st->print_cr("Thread: " INTPTR_FORMAT + " [0x%2x] State: %s _has_called_back %d _at_poll_safepoint %d", + _thread, _thread->osthread()->thread_id(), s, _has_called_back, + _at_poll_safepoint); + + _thread->print_thread_state_on(st); +} + + +// --------------------------------------------------------------------------------------------------------------------- + +// Block the thread at the safepoint poll or poll return. +void ThreadSafepointState::handle_polling_page_exception() { + + // Check state. block() will set thread state to thread_in_vm which will + // cause the safepoint state _type to become _call_back. + assert(type() == ThreadSafepointState::_running, + "polling page exception on thread not running state"); + + // Step 1: Find the nmethod from the return address + if (ShowSafepointMsgs && Verbose) { + tty->print_cr("Polling page exception at " INTPTR_FORMAT, thread()->saved_exception_pc()); + } + address real_return_addr = thread()->saved_exception_pc(); + + CodeBlob *cb = CodeCache::find_blob(real_return_addr); + assert(cb != NULL && cb->is_nmethod(), "return address should be in nmethod"); + nmethod* nm = (nmethod*)cb; + + // Find frame of caller + frame stub_fr = thread()->last_frame(); + CodeBlob* stub_cb = stub_fr.cb(); + assert(stub_cb->is_safepoint_stub(), "must be a safepoint stub"); + RegisterMap map(thread(), true); + frame caller_fr = stub_fr.sender(&map); + + // Should only be poll_return or poll + assert( nm->is_at_poll_or_poll_return(real_return_addr), "should not be at call" ); + + // This is a poll immediately before a return. The exception handling code + // has already had the effect of causing the return to occur, so the execution + // will continue immediately after the call. In addition, the oopmap at the + // return point does not mark the return value as an oop (if it is), so + // it needs a handle here to be updated. + if( nm->is_at_poll_return(real_return_addr) ) { + // See if return type is an oop. + bool return_oop = nm->method()->is_returning_oop(); + Handle return_value; + if (return_oop) { + // The oop result has been saved on the stack together with all + // the other registers. In order to preserve it over GCs we need + // to keep it in a handle. + oop result = caller_fr.saved_oop_result(&map); + assert(result == NULL || result->is_oop(), "must be oop"); + return_value = Handle(thread(), result); + assert(Universe::heap()->is_in_or_null(result), "must be heap pointer"); + } + + // Block the thread + SafepointSynchronize::block(thread()); + + // restore oop result, if any + if (return_oop) { + caller_fr.set_saved_oop_result(&map, return_value()); + } + } + + // This is a safepoint poll. Verify the return address and block. + else { + set_at_poll_safepoint(true); + + // verify the blob built the "return address" correctly + assert(real_return_addr == caller_fr.pc(), "must match"); + + // Block the thread + SafepointSynchronize::block(thread()); + set_at_poll_safepoint(false); + + // If we have a pending async exception deoptimize the frame + // as otherwise we may never deliver it. + if (thread()->has_async_condition()) { + ThreadInVMfromJavaNoAsyncException __tiv(thread()); + VM_DeoptimizeFrame deopt(thread(), caller_fr.id()); + VMThread::execute(&deopt); + } + + // If an exception has been installed we must check for a pending deoptimization + // Deoptimize frame if exception has been thrown. + + if (thread()->has_pending_exception() ) { + RegisterMap map(thread(), true); + frame caller_fr = stub_fr.sender(&map); + if (caller_fr.is_deoptimized_frame()) { + // The exception patch will destroy registers that are still + // live and will be needed during deoptimization. Defer the + // Async exception should have defered the exception until the + // next safepoint which will be detected when we get into + // the interpreter so if we have an exception now things + // are messed up. + + fatal("Exception installed and deoptimization is pending"); + } + } + } +} + + +// +// Statistics & Instrumentations +// +SafepointSynchronize::SafepointStats* SafepointSynchronize::_safepoint_stats = NULL; +int SafepointSynchronize::_cur_stat_index = 0; +julong SafepointSynchronize::_safepoint_reasons[VM_Operation::VMOp_Terminating]; +julong SafepointSynchronize::_coalesced_vmop_count = 0; +jlong SafepointSynchronize::_max_sync_time = 0; + +// last_safepoint_start_time records the start time of last safepoint. +static jlong last_safepoint_start_time = 0; +static jlong sync_end_time = 0; +static bool need_to_track_page_armed_status = false; +static bool init_done = false; + +void SafepointSynchronize::deferred_initialize_stat() { + if (init_done) return; + + if (PrintSafepointStatisticsCount <= 0) { + fatal("Wrong PrintSafepointStatisticsCount"); + } + + // If PrintSafepointStatisticsTimeout is specified, the statistics data will + // be printed right away, in which case, _safepoint_stats will regress to + // a single element array. Otherwise, it is a circular ring buffer with default + // size of PrintSafepointStatisticsCount. + int stats_array_size; + if (PrintSafepointStatisticsTimeout > 0) { + stats_array_size = 1; + PrintSafepointStatistics = true; + } else { + stats_array_size = PrintSafepointStatisticsCount; + } + _safepoint_stats = (SafepointStats*)os::malloc(stats_array_size + * sizeof(SafepointStats)); + guarantee(_safepoint_stats != NULL, + "not enough memory for safepoint instrumentation data"); + + if (UseCompilerSafepoints && DeferPollingPageLoopCount >= 0) { + need_to_track_page_armed_status = true; + } + + tty->print(" vmop_name " + "[threads: total initially_running wait_to_block] "); + tty->print("[time: spin block sync] " + "[vmop_time time_elapsed] "); + + // no page armed status printed out if it is always armed. + if (need_to_track_page_armed_status) { + tty->print("page_armed "); + } + + tty->print_cr("page_trap_count"); + + init_done = true; +} + +void SafepointSynchronize::begin_statistics(int nof_threads, int nof_running) { + deferred_initialize_stat(); + + SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; + + VM_Operation *op = VMThread::vm_operation(); + spstat->_vmop_type = (op != NULL ? op->type() : -1); + if (op != NULL) { + _safepoint_reasons[spstat->_vmop_type]++; + } + + spstat->_nof_total_threads = nof_threads; + spstat->_nof_initial_running_threads = nof_running; + spstat->_nof_threads_hit_page_trap = 0; + + // Records the start time of spinning. The real time spent on spinning + // will be adjusted when spin is done. Same trick is applied for time + // spent on waiting for threads to block. + if (nof_running != 0) { + spstat->_time_to_spin = os::javaTimeNanos(); + } else { + spstat->_time_to_spin = 0; + } + + if (last_safepoint_start_time == 0) { + spstat->_time_elapsed_since_last_safepoint = 0; + } else { + spstat->_time_elapsed_since_last_safepoint = _last_safepoint - + last_safepoint_start_time; + } + last_safepoint_start_time = _last_safepoint; +} + +void SafepointSynchronize::update_statistics_on_spin_end() { + SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; + + jlong cur_time = os::javaTimeNanos(); + + spstat->_nof_threads_wait_to_block = _waiting_to_block; + if (spstat->_nof_initial_running_threads != 0) { + spstat->_time_to_spin = cur_time - spstat->_time_to_spin; + } + + if (need_to_track_page_armed_status) { + spstat->_page_armed = (PageArmed == 1); + } + + // Records the start time of waiting for to block. Updated when block is done. + if (_waiting_to_block != 0) { + spstat->_time_to_wait_to_block = cur_time; + } else { + spstat->_time_to_wait_to_block = 0; + } +} + +void SafepointSynchronize::update_statistics_on_sync_end(jlong end_time) { + SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; + + if (spstat->_nof_threads_wait_to_block != 0) { + spstat->_time_to_wait_to_block = end_time - + spstat->_time_to_wait_to_block; + } + + // Records the end time of sync which will be used to calculate the total + // vm operation time. Again, the real time spending in syncing will be deducted + // from the start of the sync time later when end_statistics is called. + spstat->_time_to_sync = end_time - _last_safepoint; + if (spstat->_time_to_sync > _max_sync_time) { + _max_sync_time = spstat->_time_to_sync; + } + sync_end_time = end_time; +} + +void SafepointSynchronize::end_statistics(jlong vmop_end_time) { + SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; + + // Update the vm operation time. + spstat->_time_to_exec_vmop = vmop_end_time - sync_end_time; + // Only the sync time longer than the specified + // PrintSafepointStatisticsTimeout will be printed out right away. + // By default, it is -1 meaning all samples will be put into the list. + if ( PrintSafepointStatisticsTimeout > 0) { + if (spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { + print_statistics(); + } + } else { + // The safepoint statistics will be printed out when the _safepoin_stats + // array fills up. + if (_cur_stat_index != PrintSafepointStatisticsCount - 1) { + _cur_stat_index ++; + } else { + print_statistics(); + _cur_stat_index = 0; + tty->print_cr(""); + } + } +} + +void SafepointSynchronize::print_statistics() { + int index; + SafepointStats* sstats = _safepoint_stats; + + for (index = 0; index <= _cur_stat_index; index++) { + sstats = &_safepoint_stats[index]; + tty->print("%-28s [" + INT32_FORMAT_W(8)INT32_FORMAT_W(11)INT32_FORMAT_W(15) + "] ", + sstats->_vmop_type == -1 ? "no vm operation" : + VM_Operation::name(sstats->_vmop_type), + sstats->_nof_total_threads, + sstats->_nof_initial_running_threads, + sstats->_nof_threads_wait_to_block); + // "/ MICROUNITS " is to convert the unit from nanos to millis. + tty->print(" [" + INT64_FORMAT_W(6)INT64_FORMAT_W(6)INT64_FORMAT_W(6) + "] " + "["INT64_FORMAT_W(6)INT64_FORMAT_W(9) "] ", + sstats->_time_to_spin / MICROUNITS, + sstats->_time_to_wait_to_block / MICROUNITS, + sstats->_time_to_sync / MICROUNITS, + sstats->_time_to_exec_vmop / MICROUNITS, + sstats->_time_elapsed_since_last_safepoint / MICROUNITS); + + if (need_to_track_page_armed_status) { + tty->print(INT32_FORMAT" ", sstats->_page_armed); + } + tty->print_cr(INT32_FORMAT" ", sstats->_nof_threads_hit_page_trap); + } +} + +// This method will be called when VM exits. It will first call +// print_statistics to print out the rest of the sampling. Then +// it tries to summarize the sampling. +void SafepointSynchronize::print_stat_on_exit() { + if (_safepoint_stats == NULL) return; + + SafepointStats *spstat = &_safepoint_stats[_cur_stat_index]; + + // During VM exit, end_statistics may not get called and in that + // case, if the sync time is less than PrintSafepointStatisticsTimeout, + // don't print it out. + // Approximate the vm op time. + _safepoint_stats[_cur_stat_index]._time_to_exec_vmop = + os::javaTimeNanos() - sync_end_time; + + if ( PrintSafepointStatisticsTimeout < 0 || + spstat->_time_to_sync > PrintSafepointStatisticsTimeout * MICROUNITS) { + print_statistics(); + } + tty->print_cr(""); + + // Print out polling page sampling status. + if (!need_to_track_page_armed_status) { + if (UseCompilerSafepoints) { + tty->print_cr("Polling page always armed"); + } + } else { + tty->print_cr("Defer polling page loop count = %d\n", + DeferPollingPageLoopCount); + } + + for (int index = 0; index < VM_Operation::VMOp_Terminating; index++) { + if (_safepoint_reasons[index] != 0) { + tty->print_cr("%-26s"UINT64_FORMAT_W(10), VM_Operation::name(index), + _safepoint_reasons[index]); + } + } + + tty->print_cr(UINT64_FORMAT_W(5)" VM operations coalesced during safepoint", + _coalesced_vmop_count); + tty->print_cr("Maximum sync time "INT64_FORMAT_W(5)" ms", + _max_sync_time / MICROUNITS); +} + +// ------------------------------------------------------------------------------------------------ +// Non-product code + +#ifndef PRODUCT + +void SafepointSynchronize::print_state() { + if (_state == _not_synchronized) { + tty->print_cr("not synchronized"); + } else if (_state == _synchronizing || _state == _synchronized) { + tty->print_cr("State: %s", (_state == _synchronizing) ? "synchronizing" : + "synchronized"); + + for(JavaThread *cur = Threads::first(); cur; cur = cur->next()) { + cur->safepoint_state()->print(); + } + } +} + +void SafepointSynchronize::safepoint_msg(const char* format, ...) { + if (ShowSafepointMsgs) { + va_list ap; + va_start(ap, format); + tty->vprint_cr(format, ap); + va_end(ap); + } +} + +#endif // !PRODUCT