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/*
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* Copyright (c) 2013, 2018, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include "precompiled.hpp"
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#include "jfr/recorder/service/jfrPostBox.hpp"
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#include "jfr/utilities/jfrTryLock.hpp"
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#include "runtime/atomic.hpp"
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#include "runtime/orderAccess.inline.hpp"
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#include "runtime/thread.inline.hpp"
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#define MSG_IS_SYNCHRONOUS ( (MSGBIT(MSG_ROTATE)) | \
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(MSGBIT(MSG_STOP)) | \
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(MSGBIT(MSG_START)) | \
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(MSGBIT(MSG_CLONE_IN_MEMORY)) | \
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(MSGBIT(MSG_VM_ERROR)) \
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)
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static JfrPostBox* _instance = NULL;
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JfrPostBox& JfrPostBox::instance() {
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return *_instance;
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}
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JfrPostBox* JfrPostBox::create() {
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assert(_instance == NULL, "invariant");
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_instance = new JfrPostBox();
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return _instance;
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}
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void JfrPostBox::destroy() {
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assert(_instance != NULL, "invariant");
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delete _instance;
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_instance = NULL;
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}
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JfrPostBox::JfrPostBox() :
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_msg_read_serial(0),
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_msg_handled_serial(0),
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_messages(0),
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_has_waiters(false) {}
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static bool is_thread_lock_aversive() {
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Thread* const thread = Thread::current();
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return (thread->is_Java_thread() && ((JavaThread*)thread)->thread_state() != _thread_in_vm) || thread->is_VM_thread();
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}
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static bool is_synchronous(int messages) {
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return ((messages & MSG_IS_SYNCHRONOUS) != 0);
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}
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void JfrPostBox::post(JFR_Msg msg) {
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const int the_message = MSGBIT(msg);
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if (is_thread_lock_aversive()) {
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deposit(the_message);
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return;
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}
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if (!is_synchronous(the_message)) {
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asynchronous_post(the_message);
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return;
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}
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synchronous_post(the_message);
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}
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void JfrPostBox::deposit(int new_messages) {
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while (true) {
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const int current_msgs = OrderAccess::load_acquire(&_messages);
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// OR the new message
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const int exchange_value = current_msgs | new_messages;
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const int result = Atomic::cmpxchg(exchange_value, &_messages, current_msgs);
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if (result == current_msgs) {
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return;
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}
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/* Some other thread just set exactly what this thread wanted */
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if ((result & new_messages) == new_messages) {
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return;
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}
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}
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}
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void JfrPostBox::asynchronous_post(int msg) {
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assert(!is_synchronous(msg), "invariant");
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deposit(msg);
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JfrMonitorTryLock try_msg_lock(JfrMsg_lock);
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if (try_msg_lock.acquired()) {
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JfrMsg_lock->notify_all();
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}
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}
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void JfrPostBox::synchronous_post(int msg) {
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assert(is_synchronous(msg), "invariant");
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assert(!JfrMsg_lock->owned_by_self(), "should not hold JfrMsg_lock here!");
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MutexLockerEx msg_lock(JfrMsg_lock);
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deposit(msg);
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// serial_id is used to check when what we send in has been processed.
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// _msg_read_serial is read under JfrMsg_lock protection.
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const uintptr_t serial_id = OrderAccess::load_acquire(&_msg_read_serial) + 1;
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JfrMsg_lock->notify_all();
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while (!is_message_processed(serial_id)) {
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JfrMsg_lock->wait();
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}
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}
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/*
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* Check if a synchronous message has been processed.
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* We avoid racing on _msg_handled_serial by ensuring
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* that we are holding the JfrMsg_lock when checking
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* completion status.
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*/
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bool JfrPostBox::is_message_processed(uintptr_t serial_id) const {
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assert(JfrMsg_lock->owned_by_self(), "_msg_handled_serial must be read under JfrMsg_lock protection");
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return serial_id <= OrderAccess::load_acquire(&_msg_handled_serial);
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}
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bool JfrPostBox::is_empty() const {
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assert(JfrMsg_lock->owned_by_self(), "not holding JfrMsg_lock!");
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return OrderAccess::load_acquire(&_messages) == 0;
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}
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int JfrPostBox::collect() {
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// get pending and reset to 0
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const int messages = Atomic::xchg(0, &_messages);
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if (check_waiters(messages)) {
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_has_waiters = true;
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assert(JfrMsg_lock->owned_by_self(), "incrementing _msg_read_serial is protected by JfrMsg_lock");
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// Update made visible on release of JfrMsg_lock via fence instruction in Monitor::IUnlock.
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++_msg_read_serial;
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}
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return messages;
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}
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bool JfrPostBox::check_waiters(int messages) const {
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assert(JfrMsg_lock->owned_by_self(), "not holding JfrMsg_lock!");
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assert(!_has_waiters, "invariant");
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return is_synchronous(messages);
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}
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void JfrPostBox::notify_waiters() {
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if (!_has_waiters) {
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return;
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}
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_has_waiters = false;
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assert(JfrMsg_lock->owned_by_self(), "incrementing _msg_handled_serial is protected by JfrMsg_lock.");
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// Update made visible on release of JfrMsg_lock via fence instruction in Monitor::IUnlock.
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++_msg_handled_serial;
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JfrMsg_lock->notify();
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}
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// safeguard to ensure no threads are left waiting
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void JfrPostBox::notify_collection_stop() {
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MutexLockerEx msg_lock(JfrMsg_lock);
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JfrMsg_lock->notify_all();
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}
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