truffle: src/share/vm/runtime/safepoint.cpp comparison

comparison src/share/vm/runtime/safepoint.cpp @ 0:a61af66fc99e jdk7-b24

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author	duke
date	Sat, 01 Dec 2007 00:00:00 +0000
parents
children	2328d1d3f8cf

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--1:000000000000
+:a61af66fc99e
+/*
+* 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

Mercurial > hg > truffle

comparison src/share/vm/runtime/safepoint.cpp @ 0:a61af66fc99e jdk7-b24