--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/jfr/recorder/service/jfrPostBox.cpp Tue May 15 20:24:34 2018 +0200
@@ -0,0 +1,173 @@
+/*
+ * Copyright (c) 2013, 2018, 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 "jfr/recorder/service/jfrPostBox.hpp"
+#include "jfr/utilities/jfrTryLock.hpp"
+#include "runtime/atomic.hpp"
+#include "runtime/orderAccess.inline.hpp"
+#include "runtime/thread.inline.hpp"
+
+#define MSG_IS_SYNCHRONOUS ( (MSGBIT(MSG_ROTATE)) | \
+ (MSGBIT(MSG_STOP)) | \
+ (MSGBIT(MSG_START)) | \
+ (MSGBIT(MSG_CLONE_IN_MEMORY)) | \
+ (MSGBIT(MSG_VM_ERROR)) \
+ )
+
+static JfrPostBox* _instance = NULL;
+
+JfrPostBox& JfrPostBox::instance() {
+ return *_instance;
+}
+
+JfrPostBox* JfrPostBox::create() {
+ assert(_instance == NULL, "invariant");
+ _instance = new JfrPostBox();
+ return _instance;
+}
+
+void JfrPostBox::destroy() {
+ assert(_instance != NULL, "invariant");
+ delete _instance;
+ _instance = NULL;
+}
+
+JfrPostBox::JfrPostBox() :
+ _msg_read_serial(0),
+ _msg_handled_serial(0),
+ _messages(0),
+ _has_waiters(false) {}
+
+static bool is_thread_lock_aversive() {
+ Thread* const thread = Thread::current();
+ return (thread->is_Java_thread() && ((JavaThread*)thread)->thread_state() != _thread_in_vm) || thread->is_VM_thread();
+}
+
+static bool is_synchronous(int messages) {
+ return ((messages & MSG_IS_SYNCHRONOUS) != 0);
+}
+
+void JfrPostBox::post(JFR_Msg msg) {
+ const int the_message = MSGBIT(msg);
+ if (is_thread_lock_aversive()) {
+ deposit(the_message);
+ return;
+ }
+ if (!is_synchronous(the_message)) {
+ asynchronous_post(the_message);
+ return;
+ }
+ synchronous_post(the_message);
+}
+
+void JfrPostBox::deposit(int new_messages) {
+ while (true) {
+ const int current_msgs = OrderAccess::load_acquire(&_messages);
+ // OR the new message
+ const int exchange_value = current_msgs | new_messages;
+ const int result = Atomic::cmpxchg(exchange_value, &_messages, current_msgs);
+ if (result == current_msgs) {
+ return;
+ }
+ /* Some other thread just set exactly what this thread wanted */
+ if ((result & new_messages) == new_messages) {
+ return;
+ }
+ }
+}
+
+void JfrPostBox::asynchronous_post(int msg) {
+ assert(!is_synchronous(msg), "invariant");
+ deposit(msg);
+ JfrMonitorTryLock try_msg_lock(JfrMsg_lock);
+ if (try_msg_lock.acquired()) {
+ JfrMsg_lock->notify_all();
+ }
+}
+
+void JfrPostBox::synchronous_post(int msg) {
+ assert(is_synchronous(msg), "invariant");
+ assert(!JfrMsg_lock->owned_by_self(), "should not hold JfrMsg_lock here!");
+ MutexLockerEx msg_lock(JfrMsg_lock);
+ deposit(msg);
+ // serial_id is used to check when what we send in has been processed.
+ // _msg_read_serial is read under JfrMsg_lock protection.
+ const uintptr_t serial_id = OrderAccess::load_acquire(&_msg_read_serial) + 1;
+ JfrMsg_lock->notify_all();
+ while (!is_message_processed(serial_id)) {
+ JfrMsg_lock->wait();
+ }
+}
+
+/*
+ * Check if a synchronous message has been processed.
+ * We avoid racing on _msg_handled_serial by ensuring
+ * that we are holding the JfrMsg_lock when checking
+ * completion status.
+ */
+bool JfrPostBox::is_message_processed(uintptr_t serial_id) const {
+ assert(JfrMsg_lock->owned_by_self(), "_msg_handled_serial must be read under JfrMsg_lock protection");
+ return serial_id <= OrderAccess::load_acquire(&_msg_handled_serial);
+}
+
+bool JfrPostBox::is_empty() const {
+ assert(JfrMsg_lock->owned_by_self(), "not holding JfrMsg_lock!");
+ return OrderAccess::load_acquire(&_messages) == 0;
+}
+
+int JfrPostBox::collect() {
+ // get pending and reset to 0
+ const int messages = Atomic::xchg(0, &_messages);
+ if (check_waiters(messages)) {
+ _has_waiters = true;
+ assert(JfrMsg_lock->owned_by_self(), "incrementing _msg_read_serial is protected by JfrMsg_lock");
+ // Update made visible on release of JfrMsg_lock via fence instruction in Monitor::IUnlock.
+ ++_msg_read_serial;
+ }
+ return messages;
+}
+
+bool JfrPostBox::check_waiters(int messages) const {
+ assert(JfrMsg_lock->owned_by_self(), "not holding JfrMsg_lock!");
+ assert(!_has_waiters, "invariant");
+ return is_synchronous(messages);
+}
+
+void JfrPostBox::notify_waiters() {
+ if (!_has_waiters) {
+ return;
+ }
+ _has_waiters = false;
+ assert(JfrMsg_lock->owned_by_self(), "incrementing _msg_handled_serial is protected by JfrMsg_lock.");
+ // Update made visible on release of JfrMsg_lock via fence instruction in Monitor::IUnlock.
+ ++_msg_handled_serial;
+ JfrMsg_lock->notify();
+}
+
+// safeguard to ensure no threads are left waiting
+void JfrPostBox::notify_collection_stop() {
+ MutexLockerEx msg_lock(JfrMsg_lock);
+ JfrMsg_lock->notify_all();
+}