diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/runtime/vmThread.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/hotspot/share/runtime/vmThread.cpp Tue Sep 12 19:03:39 2017 +0200 @@ -0,0 +1,710 @@ +/* + * Copyright (c) 1998, 2017, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA + * or visit www.oracle.com if you need additional information or have any + * questions. + * + */ + +#include "precompiled.hpp" +#include "compiler/compileBroker.hpp" +#include "gc/shared/collectedHeap.hpp" +#include "logging/log.hpp" +#include "logging/logConfiguration.hpp" +#include "memory/resourceArea.hpp" +#include "oops/method.hpp" +#include "oops/oop.inline.hpp" +#include "oops/verifyOopClosure.hpp" +#include "runtime/interfaceSupport.hpp" +#include "runtime/mutexLocker.hpp" +#include "runtime/os.hpp" +#include "runtime/safepoint.hpp" +#include "runtime/thread.inline.hpp" +#include "runtime/vmThread.hpp" +#include "runtime/vm_operations.hpp" +#include "services/runtimeService.hpp" +#include "trace/tracing.hpp" +#include "utilities/dtrace.hpp" +#include "utilities/events.hpp" +#include "utilities/vmError.hpp" +#include "utilities/xmlstream.hpp" + +// 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 ASSERT + 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) { + + HOTSPOT_VMOPS_REQUEST( + (char *) op->name(), strlen(op->name()), + op->evaluation_mode()); + + // 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; +const char* VMThread::_no_op_reason = 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, + Monitor::_safepoint_check_never); + + 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() : NamedThread() { + set_name("VM Thread"); +} + +void VMThread::destroy() { + _vm_thread = NULL; // VM thread is gone +} + +void VMThread::run() { + assert(this == vm_thread(), "check"); + + this->initialize_named_thread(); + 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 + _no_op_reason = "Halt"; + SafepointSynchronize::begin(); + + if (VerifyBeforeExit) { + HandleMark hm(VMThread::vm_thread()); + // Among other things, this ensures that Eden top is correct. + Universe::heap()->prepare_for_verify(); + // Silent verification so as not to pollute normal output, + // unless we really asked for it. + Universe::verify(); + } + + 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(); + } + + // We are now racing with the VM termination being carried out in + // another thread, so we don't "delete this". Numerous threads don't + // get deleted when the VM terminates + +} + + +// 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::evaluate_operation(VM_Operation* op) { + ResourceMark rm; + + { + PerfTraceTime vm_op_timer(perf_accumulated_vm_operation_time()); + HOTSPOT_VMOPS_BEGIN( + (char *) op->name(), strlen(op->name()), + op->evaluation_mode()); + + EventExecuteVMOperation event; + + op->evaluate(); + + if (event.should_commit()) { + const bool is_concurrent = op->evaluate_concurrently(); + const bool evaluate_at_safepoint = op->evaluate_at_safepoint(); + event.set_operation(op->type()); + event.set_safepoint(evaluate_at_safepoint); + event.set_blocking(!is_concurrent); + // Only write caller thread information for non-concurrent vm operations. + // For concurrent vm operations, the thread id is set to 0 indicating thread is unknown. + // This is because the caller thread could have exited already. + event.set_caller(is_concurrent ? 0 : THREAD_TRACE_ID(op->calling_thread())); + event.set_safepointId(evaluate_at_safepoint ? SafepointSynchronize::safepoint_counter() : 0); + event.commit(); + } + + HOTSPOT_VMOPS_END( + (char *) op->name(), strlen(op->name()), + op->evaluation_mode()); + } + + // 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; + } +} + +bool VMThread::no_op_safepoint_needed(bool check_time) { + if (SafepointALot) { + _no_op_reason = "SafepointALot"; + return true; + } + if (!SafepointSynchronize::is_cleanup_needed()) { + return false; + } + if (check_time) { + long interval = SafepointSynchronize::last_non_safepoint_interval(); + bool max_time_exceeded = GuaranteedSafepointInterval != 0 && + (interval > GuaranteedSafepointInterval); + if (!max_time_exceeded) { + return false; + } + } + _no_op_reason = "Cleanup"; + return true; +} + +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) && !VMError::is_error_reported() && + (os::elapsedTime() > (double)SelfDestructTimer * 60.0)) { + tty->print_cr("VM self-destructed"); + exit(-1); + } + + if (timedout && VMThread::no_op_safepoint_needed(false)) { + 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()) { + log_debug(vmthread)("Evaluating safepoint VM operation: %s", _cur_vm_operation->name()); + + _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 { + log_debug(vmthread)("Evaluating coalesced safepoint VM operation: %s", _cur_vm_operation->name()); + // 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(); + + } else { // not a safepoint operation + log_debug(vmthread)("Evaluating non-safepoint VM operation: %s", _cur_vm_operation->name()); + 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 (VMThread::no_op_safepoint_needed(true)) { + HandleMark hm(VMThread::vm_thread()); + SafepointSynchronize::begin(); + SafepointSynchronize::end(); + } + } +} + +void VMThread::execute(VM_Operation* op) { + Thread* t = Thread::current(); + + if (!t->is_VM_thread()) { + SkipGCALot sgcalot(t); // avoid re-entrant attempts to gc-a-lot + // JavaThread or WatcherThread + bool concurrent = op->evaluate_concurrently(); + // only blocking VM operations need to verify the caller's safepoint state: + if (!concurrent) { + 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 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(); + log_debug(vmthread)("Adding VM operation: %s", op->name()); + 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()) { + fatal("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, CodeBlobClosure* cf) { + Thread::oops_do(f, cf); + _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, NULL); +}