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/*
* Copyright (c) 2017, 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.
*
*/
#ifndef SHARE_VM_RUNTIME_HANDSHAKE_HPP
#define SHARE_VM_RUNTIME_HANDSHAKE_HPP
#include "memory/allocation.hpp"
#include "runtime/flags/flagSetting.hpp"
#include "runtime/semaphore.hpp"
class ThreadClosure;
class JavaThread;
// A handshake operation is a callback that is executed for each JavaThread
// while that thread is in a safepoint safe state. The callback is executed
// either by the thread itself or by the VM thread while keeping the thread
// in a blocked state. A handshake can be performed with a single
// JavaThread as well.
class Handshake : public AllStatic {
public:
// Execution of handshake operation
static void execute(ThreadClosure* thread_cl);
static bool execute(ThreadClosure* thread_cl, JavaThread* target);
};
class HandshakeOperation;
// The HandshakeState keep tracks of an ongoing handshake for one JavaThread.
// VM thread and JavaThread are serialized with the semaphore making sure
// the operation is only done by either VM thread on behalf of the JavaThread
// or the JavaThread itself.
class HandshakeState {
HandshakeOperation* volatile _operation;
Semaphore _semaphore;
bool _thread_in_process_handshake;
bool claim_handshake_for_vmthread();
bool vmthread_can_process_handshake(JavaThread* target);
void clear_handshake(JavaThread* thread);
void cancel_inner(JavaThread* thread);
void process_self_inner(JavaThread* thread);
public:
HandshakeState();
void set_operation(JavaThread* thread, HandshakeOperation* op);
bool has_operation() const {
return _operation != NULL;
}
void cancel(JavaThread* thread) {
if (!_thread_in_process_handshake) {
FlagSetting fs(_thread_in_process_handshake, true);
cancel_inner(thread);
}
}
void process_by_self(JavaThread* thread) {
if (!_thread_in_process_handshake) {
FlagSetting fs(_thread_in_process_handshake, true);
process_self_inner(thread);
}
}
void process_by_vmthread(JavaThread* target);
};
#endif // SHARE_VM_RUNTIME_HANDSHAKE_HPP