--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/runtime/vmThread.cpp Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,655 @@
+/*
+ * Copyright 1998-2007 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/_vmThread.cpp.incl"
+
+// Dummy VM operation to act as first element in our circular double-linked list
+class VM_Dummy: public VM_Operation {
+ VMOp_Type type() const { return VMOp_Dummy; }
+ void doit() {};
+};
+
+VMOperationQueue::VMOperationQueue() {
+ // The queue is a circular doubled-linked list, which always contains
+ // one element (i.e., one element means empty).
+ for(int i = 0; i < nof_priorities; i++) {
+ _queue_length[i] = 0;
+ _queue_counter = 0;
+ _queue[i] = new VM_Dummy();
+ _queue[i]->set_next(_queue[i]);
+ _queue[i]->set_prev(_queue[i]);
+ }
+ _drain_list = NULL;
+}
+
+
+bool VMOperationQueue::queue_empty(int prio) {
+ // It is empty if there is exactly one element
+ bool empty = (_queue[prio] == _queue[prio]->next());
+ assert( (_queue_length[prio] == 0 && empty) ||
+ (_queue_length[prio] > 0 && !empty), "sanity check");
+ return _queue_length[prio] == 0;
+}
+
+// Inserts an element to the right of the q element
+void VMOperationQueue::insert(VM_Operation* q, VM_Operation* n) {
+ assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
+ n->set_prev(q);
+ n->set_next(q->next());
+ q->next()->set_prev(n);
+ q->set_next(n);
+}
+
+void VMOperationQueue::queue_add_front(int prio, VM_Operation *op) {
+ _queue_length[prio]++;
+ insert(_queue[prio]->next(), op);
+}
+
+void VMOperationQueue::queue_add_back(int prio, VM_Operation *op) {
+ _queue_length[prio]++;
+ insert(_queue[prio]->prev(), op);
+}
+
+
+void VMOperationQueue::unlink(VM_Operation* q) {
+ assert(q->next()->prev() == q && q->prev()->next() == q, "sanity check");
+ q->prev()->set_next(q->next());
+ q->next()->set_prev(q->prev());
+}
+
+VM_Operation* VMOperationQueue::queue_remove_front(int prio) {
+ if (queue_empty(prio)) return NULL;
+ assert(_queue_length[prio] >= 0, "sanity check");
+ _queue_length[prio]--;
+ VM_Operation* r = _queue[prio]->next();
+ assert(r != _queue[prio], "cannot remove base element");
+ unlink(r);
+ return r;
+}
+
+VM_Operation* VMOperationQueue::queue_drain(int prio) {
+ if (queue_empty(prio)) return NULL;
+ DEBUG_ONLY(int length = _queue_length[prio];);
+ assert(length >= 0, "sanity check");
+ _queue_length[prio] = 0;
+ VM_Operation* r = _queue[prio]->next();
+ assert(r != _queue[prio], "cannot remove base element");
+ // remove links to base element from head and tail
+ r->set_prev(NULL);
+ _queue[prio]->prev()->set_next(NULL);
+ // restore queue to empty state
+ _queue[prio]->set_next(_queue[prio]);
+ _queue[prio]->set_prev(_queue[prio]);
+ assert(queue_empty(prio), "drain corrupted queue")
+#ifdef DEBUG
+ int len = 0;
+ VM_Operation* cur;
+ for(cur = r; cur != NULL; cur=cur->next()) len++;
+ assert(len == length, "drain lost some ops");
+#endif
+ return r;
+}
+
+void VMOperationQueue::queue_oops_do(int queue, OopClosure* f) {
+ VM_Operation* cur = _queue[queue];
+ cur = cur->next();
+ while (cur != _queue[queue]) {
+ cur->oops_do(f);
+ cur = cur->next();
+ }
+}
+
+void VMOperationQueue::drain_list_oops_do(OopClosure* f) {
+ VM_Operation* cur = _drain_list;
+ while (cur != NULL) {
+ cur->oops_do(f);
+ cur = cur->next();
+ }
+}
+
+//-----------------------------------------------------------------
+// High-level interface
+bool VMOperationQueue::add(VM_Operation *op) {
+ // Encapsulates VM queue policy. Currently, that
+ // only involves putting them on the right list
+ if (op->evaluate_at_safepoint()) {
+ queue_add_back(SafepointPriority, op);
+ return true;
+ }
+
+ queue_add_back(MediumPriority, op);
+ return true;
+}
+
+VM_Operation* VMOperationQueue::remove_next() {
+ // Assuming VMOperation queue is two-level priority queue. If there are
+ // more than two priorities, we need a different scheduling algorithm.
+ assert(SafepointPriority == 0 && MediumPriority == 1 && nof_priorities == 2,
+ "current algorithm does not work");
+
+ // simple counter based scheduling to prevent starvation of lower priority
+ // queue. -- see 4390175
+ int high_prio, low_prio;
+ if (_queue_counter++ < 10) {
+ high_prio = SafepointPriority;
+ low_prio = MediumPriority;
+ } else {
+ _queue_counter = 0;
+ high_prio = MediumPriority;
+ low_prio = SafepointPriority;
+ }
+
+ return queue_remove_front(queue_empty(high_prio) ? low_prio : high_prio);
+}
+
+void VMOperationQueue::oops_do(OopClosure* f) {
+ for(int i = 0; i < nof_priorities; i++) {
+ queue_oops_do(i, f);
+ }
+ drain_list_oops_do(f);
+}
+
+
+//------------------------------------------------------------------------------------------------------------------
+// Implementation of VMThread stuff
+
+bool VMThread::_should_terminate = false;
+bool VMThread::_terminated = false;
+Monitor* VMThread::_terminate_lock = NULL;
+VMThread* VMThread::_vm_thread = NULL;
+VM_Operation* VMThread::_cur_vm_operation = NULL;
+VMOperationQueue* VMThread::_vm_queue = NULL;
+PerfCounter* VMThread::_perf_accumulated_vm_operation_time = NULL;
+
+
+void VMThread::create() {
+ assert(vm_thread() == NULL, "we can only allocate one VMThread");
+ _vm_thread = new VMThread();
+
+ // Create VM operation queue
+ _vm_queue = new VMOperationQueue();
+ guarantee(_vm_queue != NULL, "just checking");
+
+ _terminate_lock = new Monitor(Mutex::safepoint, "VMThread::_terminate_lock", true);
+
+ if (UsePerfData) {
+ // jvmstat performance counters
+ Thread* THREAD = Thread::current();
+ _perf_accumulated_vm_operation_time =
+ PerfDataManager::create_counter(SUN_THREADS, "vmOperationTime",
+ PerfData::U_Ticks, CHECK);
+ }
+}
+
+
+VMThread::VMThread() : Thread() {
+ // nothing to do
+}
+
+void VMThread::destroy() {
+ if (_vm_thread != NULL) {
+ delete _vm_thread;
+ _vm_thread = NULL; // VM thread is gone
+ }
+}
+
+void VMThread::run() {
+ assert(this == vm_thread(), "check");
+
+ this->initialize_thread_local_storage();
+ this->record_stack_base_and_size();
+ // Notify_lock wait checks on active_handles() to rewait in
+ // case of spurious wakeup, it should wait on the last
+ // value set prior to the notify
+ this->set_active_handles(JNIHandleBlock::allocate_block());
+
+ {
+ MutexLocker ml(Notify_lock);
+ Notify_lock->notify();
+ }
+ // Notify_lock is destroyed by Threads::create_vm()
+
+ int prio = (VMThreadPriority == -1)
+ ? os::java_to_os_priority[NearMaxPriority]
+ : VMThreadPriority;
+ // Note that I cannot call os::set_priority because it expects Java
+ // priorities and I am *explicitly* using OS priorities so that it's
+ // possible to set the VM thread priority higher than any Java thread.
+ os::set_native_priority( this, prio );
+
+ // Wait for VM_Operations until termination
+ this->loop();
+
+ // Note the intention to exit before safepointing.
+ // 6295565 This has the effect of waiting for any large tty
+ // outputs to finish.
+ if (xtty != NULL) {
+ ttyLocker ttyl;
+ xtty->begin_elem("destroy_vm");
+ xtty->stamp();
+ xtty->end_elem();
+ assert(should_terminate(), "termination flag must be set");
+ }
+
+ // 4526887 let VM thread exit at Safepoint
+ SafepointSynchronize::begin();
+
+ if (VerifyBeforeExit) {
+ HandleMark hm(VMThread::vm_thread());
+ // Among other things, this ensures that Eden top is correct.
+ Universe::heap()->prepare_for_verify();
+ os::check_heap();
+ Universe::verify(true, true); // Silent verification to not polute normal output
+ }
+
+ CompileBroker::set_should_block();
+
+ // wait for threads (compiler threads or daemon threads) in the
+ // _thread_in_native state to block.
+ VM_Exit::wait_for_threads_in_native_to_block();
+
+ // signal other threads that VM process is gone
+ {
+ // Note: we must have the _no_safepoint_check_flag. Mutex::lock() allows
+ // VM thread to enter any lock at Safepoint as long as its _owner is NULL.
+ // If that happens after _terminate_lock->wait() has unset _owner
+ // but before it actually drops the lock and waits, the notification below
+ // may get lost and we will have a hang. To avoid this, we need to use
+ // Mutex::lock_without_safepoint_check().
+ MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
+ _terminated = true;
+ _terminate_lock->notify();
+ }
+
+ // Deletion must be done synchronously by the JNI DestroyJavaVM thread
+ // so that the VMThread deletion completes before the main thread frees
+ // up the CodeHeap.
+
+}
+
+
+// Notify the VMThread that the last non-daemon JavaThread has terminated,
+// and wait until operation is performed.
+void VMThread::wait_for_vm_thread_exit() {
+ { MutexLocker mu(VMOperationQueue_lock);
+ _should_terminate = true;
+ VMOperationQueue_lock->notify();
+ }
+
+ // Note: VM thread leaves at Safepoint. We are not stopped by Safepoint
+ // because this thread has been removed from the threads list. But anything
+ // that could get blocked by Safepoint should not be used after this point,
+ // otherwise we will hang, since there is no one can end the safepoint.
+
+ // Wait until VM thread is terminated
+ // Note: it should be OK to use Terminator_lock here. But this is called
+ // at a very delicate time (VM shutdown) and we are operating in non- VM
+ // thread at Safepoint. It's safer to not share lock with other threads.
+ { MutexLockerEx ml(_terminate_lock, Mutex::_no_safepoint_check_flag);
+ while(!VMThread::is_terminated()) {
+ _terminate_lock->wait(Mutex::_no_safepoint_check_flag);
+ }
+ }
+}
+
+void VMThread::print_on(outputStream* st) const {
+ st->print("\"%s\" ", name());
+ Thread::print_on(st);
+ st->cr();
+}
+
+void VMThread::evaluate_operation(VM_Operation* op) {
+ ResourceMark rm;
+
+ {
+ PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time());
+ op->evaluate();
+ }
+
+ // Last access of info in _cur_vm_operation!
+ bool c_heap_allocated = op->is_cheap_allocated();
+
+ // Mark as completed
+ if (!op->evaluate_concurrently()) {
+ op->calling_thread()->increment_vm_operation_completed_count();
+ }
+ // It is unsafe to access the _cur_vm_operation after the 'increment_vm_operation_completed_count' call,
+ // since if it is stack allocated the calling thread might have deallocated
+ if (c_heap_allocated) {
+ delete _cur_vm_operation;
+ }
+}
+
+
+void VMThread::loop() {
+ assert(_cur_vm_operation == NULL, "no current one should be executing");
+
+ while(true) {
+ VM_Operation* safepoint_ops = NULL;
+ //
+ // Wait for VM operation
+ //
+ // use no_safepoint_check to get lock without attempting to "sneak"
+ { MutexLockerEx mu_queue(VMOperationQueue_lock,
+ Mutex::_no_safepoint_check_flag);
+
+ // Look for new operation
+ assert(_cur_vm_operation == NULL, "no current one should be executing");
+ _cur_vm_operation = _vm_queue->remove_next();
+
+ // Stall time tracking code
+ if (PrintVMQWaitTime && _cur_vm_operation != NULL &&
+ !_cur_vm_operation->evaluate_concurrently()) {
+ long stall = os::javaTimeMillis() - _cur_vm_operation->timestamp();
+ if (stall > 0)
+ tty->print_cr("%s stall: %Ld", _cur_vm_operation->name(), stall);
+ }
+
+ while (!should_terminate() && _cur_vm_operation == NULL) {
+ // wait with a timeout to guarantee safepoints at regular intervals
+ bool timedout =
+ VMOperationQueue_lock->wait(Mutex::_no_safepoint_check_flag,
+ GuaranteedSafepointInterval);
+
+ // Support for self destruction
+ if ((SelfDestructTimer != 0) && !is_error_reported() &&
+ (os::elapsedTime() > SelfDestructTimer * 60)) {
+ tty->print_cr("VM self-destructed");
+ exit(-1);
+ }
+
+ if (timedout && (SafepointALot ||
+ SafepointSynchronize::is_cleanup_needed())) {
+ MutexUnlockerEx mul(VMOperationQueue_lock,
+ Mutex::_no_safepoint_check_flag);
+ // Force a safepoint since we have not had one for at least
+ // 'GuaranteedSafepointInterval' milliseconds. This will run all
+ // the clean-up processing that needs to be done regularly at a
+ // safepoint
+ SafepointSynchronize::begin();
+ #ifdef ASSERT
+ if (GCALotAtAllSafepoints) InterfaceSupport::check_gc_alot();
+ #endif
+ SafepointSynchronize::end();
+ }
+ _cur_vm_operation = _vm_queue->remove_next();
+
+ // If we are at a safepoint we will evaluate all the operations that
+ // follow that also require a safepoint
+ if (_cur_vm_operation != NULL &&
+ _cur_vm_operation->evaluate_at_safepoint()) {
+ safepoint_ops = _vm_queue->drain_at_safepoint_priority();
+ }
+ }
+
+ if (should_terminate()) break;
+ } // Release mu_queue_lock
+
+ //
+ // Execute VM operation
+ //
+ { HandleMark hm(VMThread::vm_thread());
+
+ EventMark em("Executing VM operation: %s", vm_operation()->name());
+ assert(_cur_vm_operation != NULL, "we should have found an operation to execute");
+
+ // Give the VM thread an extra quantum. Jobs tend to be bursty and this
+ // helps the VM thread to finish up the job.
+ // FIXME: When this is enabled and there are many threads, this can degrade
+ // performance significantly.
+ if( VMThreadHintNoPreempt )
+ os::hint_no_preempt();
+
+ // If we are at a safepoint we will evaluate all the operations that
+ // follow that also require a safepoint
+ if (_cur_vm_operation->evaluate_at_safepoint()) {
+
+ if (PrintGCApplicationConcurrentTime) {
+ gclog_or_tty->print_cr("Application time: %3.7f seconds",
+ RuntimeService::last_application_time_sec());
+ }
+
+ _vm_queue->set_drain_list(safepoint_ops); // ensure ops can be scanned
+
+ SafepointSynchronize::begin();
+ evaluate_operation(_cur_vm_operation);
+ // now process all queued safepoint ops, iteratively draining
+ // the queue until there are none left
+ do {
+ _cur_vm_operation = safepoint_ops;
+ if (_cur_vm_operation != NULL) {
+ do {
+ // evaluate_operation deletes the op object so we have
+ // to grab the next op now
+ VM_Operation* next = _cur_vm_operation->next();
+ _vm_queue->set_drain_list(next);
+ evaluate_operation(_cur_vm_operation);
+ _cur_vm_operation = next;
+ if (PrintSafepointStatistics) {
+ SafepointSynchronize::inc_vmop_coalesced_count();
+ }
+ } while (_cur_vm_operation != NULL);
+ }
+ // There is a chance that a thread enqueued a safepoint op
+ // since we released the op-queue lock and initiated the safepoint.
+ // So we drain the queue again if there is anything there, as an
+ // optimization to try and reduce the number of safepoints.
+ // As the safepoint synchronizes us with JavaThreads we will see
+ // any enqueue made by a JavaThread, but the peek will not
+ // necessarily detect a concurrent enqueue by a GC thread, but
+ // that simply means the op will wait for the next major cycle of the
+ // VMThread - just as it would if the GC thread lost the race for
+ // the lock.
+ if (_vm_queue->peek_at_safepoint_priority()) {
+ // must hold lock while draining queue
+ MutexLockerEx mu_queue(VMOperationQueue_lock,
+ Mutex::_no_safepoint_check_flag);
+ safepoint_ops = _vm_queue->drain_at_safepoint_priority();
+ } else {
+ safepoint_ops = NULL;
+ }
+ } while(safepoint_ops != NULL);
+
+ _vm_queue->set_drain_list(NULL);
+
+ // Complete safepoint synchronization
+ SafepointSynchronize::end();
+
+ if (PrintGCApplicationStoppedTime) {
+ gclog_or_tty->print_cr("Total time for which application threads "
+ "were stopped: %3.7f seconds",
+ RuntimeService::last_safepoint_time_sec());
+ }
+
+ } else { // not a safepoint operation
+ if (TraceLongCompiles) {
+ elapsedTimer t;
+ t.start();
+ evaluate_operation(_cur_vm_operation);
+ t.stop();
+ double secs = t.seconds();
+ if (secs * 1e3 > LongCompileThreshold) {
+ // XXX - _cur_vm_operation should not be accessed after
+ // the completed count has been incremented; the waiting
+ // thread may have already freed this memory.
+ tty->print_cr("vm %s: %3.7f secs]", _cur_vm_operation->name(), secs);
+ }
+ } else {
+ evaluate_operation(_cur_vm_operation);
+ }
+
+ _cur_vm_operation = NULL;
+ }
+ }
+
+ //
+ // Notify (potential) waiting Java thread(s) - lock without safepoint
+ // check so that sneaking is not possible
+ { MutexLockerEx mu(VMOperationRequest_lock,
+ Mutex::_no_safepoint_check_flag);
+ VMOperationRequest_lock->notify_all();
+ }
+
+ //
+ // We want to make sure that we get to a safepoint regularly.
+ //
+ if (SafepointALot || SafepointSynchronize::is_cleanup_needed()) {
+ long interval = SafepointSynchronize::last_non_safepoint_interval();
+ bool max_time_exceeded = GuaranteedSafepointInterval != 0 && (interval > GuaranteedSafepointInterval);
+ if (SafepointALot || max_time_exceeded) {
+ HandleMark hm(VMThread::vm_thread());
+ SafepointSynchronize::begin();
+ SafepointSynchronize::end();
+ }
+ }
+ }
+}
+
+void VMThread::execute(VM_Operation* op) {
+ Thread* t = Thread::current();
+
+ if (!t->is_VM_thread()) {
+ // JavaThread or WatcherThread
+ t->check_for_valid_safepoint_state(true);
+
+ // New request from Java thread, evaluate prologue
+ if (!op->doit_prologue()) {
+ return; // op was cancelled
+ }
+
+ // Setup VM_operations for execution
+ op->set_calling_thread(t, Thread::get_priority(t));
+
+ // It does not make sense to execute the epilogue, if the VM operation object is getting
+ // deallocated by the VM thread.
+ bool concurrent = op->evaluate_concurrently();
+ bool execute_epilog = !op->is_cheap_allocated();
+ assert(!concurrent || op->is_cheap_allocated(), "concurrent => cheap_allocated");
+
+ // Get ticket number for non-concurrent VM operations
+ int ticket = 0;
+ if (!concurrent) {
+ ticket = t->vm_operation_ticket();
+ }
+
+ // Add VM operation to list of waiting threads. We are guaranteed not to block while holding the
+ // VMOperationQueue_lock, so we can block without a safepoint check. This allows vm operation requests
+ // to be queued up during a safepoint synchronization.
+ {
+ VMOperationQueue_lock->lock_without_safepoint_check();
+ bool ok = _vm_queue->add(op);
+ op->set_timestamp(os::javaTimeMillis());
+ VMOperationQueue_lock->notify();
+ VMOperationQueue_lock->unlock();
+ // VM_Operation got skipped
+ if (!ok) {
+ assert(concurrent, "can only skip concurrent tasks");
+ if (op->is_cheap_allocated()) delete op;
+ return;
+ }
+ }
+
+ if (!concurrent) {
+ // Wait for completion of request (non-concurrent)
+ // Note: only a JavaThread triggers the safepoint check when locking
+ MutexLocker mu(VMOperationRequest_lock);
+ while(t->vm_operation_completed_count() < ticket) {
+ VMOperationRequest_lock->wait(!t->is_Java_thread());
+ }
+ }
+
+ if (execute_epilog) {
+ op->doit_epilogue();
+ }
+ } else {
+ // invoked by VM thread; usually nested VM operation
+ assert(t->is_VM_thread(), "must be a VM thread");
+ VM_Operation* prev_vm_operation = vm_operation();
+ if (prev_vm_operation != NULL) {
+ // Check the VM operation allows nested VM operation. This normally not the case, e.g., the compiler
+ // does not allow nested scavenges or compiles.
+ if (!prev_vm_operation->allow_nested_vm_operations()) {
+ fatal2("Nested VM operation %s requested by operation %s", op->name(), vm_operation()->name());
+ }
+ op->set_calling_thread(prev_vm_operation->calling_thread(), prev_vm_operation->priority());
+ }
+
+ EventMark em("Executing %s VM operation: %s", prev_vm_operation ? "nested" : "", op->name());
+
+ // Release all internal handles after operation is evaluated
+ HandleMark hm(t);
+ _cur_vm_operation = op;
+
+ if (op->evaluate_at_safepoint() && !SafepointSynchronize::is_at_safepoint()) {
+ SafepointSynchronize::begin();
+ op->evaluate();
+ SafepointSynchronize::end();
+ } else {
+ op->evaluate();
+ }
+
+ // Free memory if needed
+ if (op->is_cheap_allocated()) delete op;
+
+ _cur_vm_operation = prev_vm_operation;
+ }
+}
+
+
+void VMThread::oops_do(OopClosure* f) {
+ Thread::oops_do(f);
+ _vm_queue->oops_do(f);
+}
+
+//------------------------------------------------------------------------------------------------------------------
+#ifndef PRODUCT
+
+void VMOperationQueue::verify_queue(int prio) {
+ // Check that list is correctly linked
+ int length = _queue_length[prio];
+ VM_Operation *cur = _queue[prio];
+ int i;
+
+ // Check forward links
+ for(i = 0; i < length; i++) {
+ cur = cur->next();
+ assert(cur != _queue[prio], "list to short (forward)");
+ }
+ assert(cur->next() == _queue[prio], "list to long (forward)");
+
+ // Check backwards links
+ cur = _queue[prio];
+ for(i = 0; i < length; i++) {
+ cur = cur->prev();
+ assert(cur != _queue[prio], "list to short (backwards)");
+ }
+ assert(cur->prev() == _queue[prio], "list to long (backwards)");
+}
+
+#endif
+
+void VMThread::verify() {
+ oops_do(&VerifyOopClosure::verify_oop);
+}