8151601: Cleanup locking of the Reference pending list
Reviewed-by: brutisso, stefank
/*
* Copyright (c) 2016, 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
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#include "precompiled.hpp"
#include "classfile/javaClasses.hpp"
#include "classfile/systemDictionary.hpp"
#include "gc/shared/collectedHeap.hpp"
#include "gc/shared/referencePendingListLocker.hpp"
#include "memory/universe.hpp"
#include "runtime/javaCalls.hpp"
#include "utilities/preserveException.hpp"
ReferencePendingListLockerThread::ReferencePendingListLockerThread() :
JavaThread(&start),
_monitor(Monitor::nonleaf, "ReferencePendingListLocker", false, Monitor::_safepoint_check_sometimes),
_message(NONE) {}
ReferencePendingListLockerThread* ReferencePendingListLockerThread::create(TRAPS) {
// Create Java thread objects
instanceKlassHandle thread_klass = SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true, CHECK_NULL);
instanceHandle thread_object = thread_klass->allocate_instance_handle(CHECK_NULL);
Handle thread_name = java_lang_String::create_from_str("Reference Pending List Locker", CHECK_NULL);
Handle thread_group = Universe::system_thread_group();
JavaValue result(T_VOID);
JavaCalls::call_special(&result,
thread_object,
thread_klass,
vmSymbols::object_initializer_name(),
vmSymbols::threadgroup_string_void_signature(),
thread_group,
thread_name,
CHECK_NULL);
{
MutexLocker ml(Threads_lock);
// Allocate thread
ReferencePendingListLockerThread* thread = new ReferencePendingListLockerThread();
if (thread == NULL || thread->osthread() == NULL) {
vm_exit_during_initialization("java.lang.OutOfMemoryError",
os::native_thread_creation_failed_msg());
}
// Initialize thread
java_lang_Thread::set_thread(thread_object(), thread);
java_lang_Thread::set_priority(thread_object(), NearMaxPriority);
java_lang_Thread::set_daemon(thread_object());
thread->set_threadObj(thread_object());
// Start thread
Threads::add(thread);
Thread::start(thread);
return thread;
}
}
void ReferencePendingListLockerThread::start(JavaThread* thread, TRAPS) {
ReferencePendingListLockerThread* locker_thread = static_cast<ReferencePendingListLockerThread*>(thread);
locker_thread->receive_and_handle_messages();
}
bool ReferencePendingListLockerThread::is_hidden_from_external_view() const {
return true;
}
void ReferencePendingListLockerThread::send_message(Message message) {
assert(message != NONE, "Should not be none");
MonitorLockerEx ml(&_monitor, Monitor::_no_safepoint_check_flag);
// Wait for completion of current message
while (_message != NONE) {
ml.wait(Monitor::_no_safepoint_check_flag);
}
// Send new message
_message = message;
ml.notify_all();
// Wait for completion of new message
while (_message != NONE) {
ml.wait(Monitor::_no_safepoint_check_flag);
}
}
void ReferencePendingListLockerThread::receive_and_handle_messages() {
ReferencePendingListLocker pending_list_locker;
MonitorLockerEx ml(&_monitor);
// Main loop, never terminates
for (;;) {
// Wait for message
while (_message == NONE) {
ml.wait();
}
// Handle message
if (_message == LOCK) {
pending_list_locker.lock();
} else if (_message == UNLOCK) {
pending_list_locker.unlock();
} else {
ShouldNotReachHere();
}
// Clear message
_message = NONE;
ml.notify_all();
}
}
void ReferencePendingListLockerThread::lock() {
send_message(LOCK);
}
void ReferencePendingListLockerThread::unlock() {
send_message(UNLOCK);
}
bool ReferencePendingListLocker::_is_initialized = false;
ReferencePendingListLockerThread* ReferencePendingListLocker::_locker_thread = NULL;
void ReferencePendingListLocker::initialize(bool needs_locker_thread, TRAPS) {
if (needs_locker_thread) {
_locker_thread = ReferencePendingListLockerThread::create(CHECK);
}
_is_initialized = true;
}
bool ReferencePendingListLocker::is_initialized() {
return _is_initialized;
}
bool ReferencePendingListLocker::is_locked_by_self() {
oop pending_list_lock = java_lang_ref_Reference::pending_list_lock();
if (pending_list_lock == NULL) {
return false;
}
JavaThread* thread = JavaThread::current();
Handle handle(thread, pending_list_lock);
return ObjectSynchronizer::current_thread_holds_lock(thread, handle);
}
void ReferencePendingListLocker::lock() {
assert(!Heap_lock->owned_by_self(), "Heap_lock must not be owned by requesting thread");
if (Thread::current()->is_Java_thread()) {
assert(java_lang_ref_Reference::pending_list_lock() != NULL, "Not initialized");
// We may enter this with a pending exception
PRESERVE_EXCEPTION_MARK;
HandleMark hm;
Handle handle(THREAD, java_lang_ref_Reference::pending_list_lock());
assert(!is_locked_by_self(), "Should not be locked by self");
// Lock
ObjectSynchronizer::fast_enter(handle, &_basic_lock, false, THREAD);
assert(is_locked_by_self(), "Locking failed");
if (HAS_PENDING_EXCEPTION) {
CLEAR_PENDING_EXCEPTION;
}
} else {
// Delegate operation to locker thread
assert(_locker_thread != NULL, "Locker thread not created");
_locker_thread->lock();
}
}
void ReferencePendingListLocker::unlock() {
if (Thread::current()->is_Java_thread()) {
assert(java_lang_ref_Reference::pending_list_lock() != NULL, "Not initialized");
// We may enter this with a pending exception
PRESERVE_EXCEPTION_MARK;
HandleMark hm;
Handle handle(THREAD, java_lang_ref_Reference::pending_list_lock());
assert(is_locked_by_self(), "Should be locked by self");
// Notify waiters if the pending list is non-empty
if (java_lang_ref_Reference::pending_list() != NULL) {
ObjectSynchronizer::notifyall(handle, THREAD);
}
// Unlock
ObjectSynchronizer::fast_exit(handle(), &_basic_lock, THREAD);
assert(!is_locked_by_self(), "Unlocking failed");
if (HAS_PENDING_EXCEPTION) {
CLEAR_PENDING_EXCEPTION;
}
} else {
// Delegate operation to locker thread
assert(_locker_thread != NULL, "Locker thread not created");
_locker_thread->unlock();
}
}