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116 lines
4 KiB
C++
116 lines
4 KiB
C++
/*
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* Copyright (c) 2017, 2020, 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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#ifndef SHARE_RUNTIME_HANDSHAKE_HPP
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#define SHARE_RUNTIME_HANDSHAKE_HPP
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#include "memory/allocation.hpp"
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#include "memory/iterator.hpp"
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#include "runtime/semaphore.hpp"
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#include "utilities/autoRestore.hpp"
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class HandshakeOperation;
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class JavaThread;
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// A handshake closure is a callback that is executed for each JavaThread
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// while that thread is in a safepoint safe state. The callback is executed
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// either by the target JavaThread itself or by the VMThread while keeping
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// the target thread in a blocked state. A handshake can be performed with a
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// single JavaThread as well. In that case, the callback is executed either
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// by the target JavaThread itself or, depending on whether the operation is
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// a direct handshake or not, by the JavaThread that requested the handshake
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// or the VMThread respectively.
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class HandshakeClosure : public ThreadClosure {
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const char* const _name;
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public:
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HandshakeClosure(const char* name) : _name(name) {}
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const char* name() const {
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return _name;
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}
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virtual void do_thread(Thread* thread) = 0;
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};
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class Handshake : public AllStatic {
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public:
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// Execution of handshake operation
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static void execute(HandshakeClosure* hs_cl);
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static bool execute(HandshakeClosure* hs_cl, JavaThread* target);
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static bool execute_direct(HandshakeClosure* hs_cl, JavaThread* target);
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};
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// The HandshakeState keeps track of an ongoing handshake for this JavaThread.
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// VMThread/Handshaker and JavaThread are serialized with semaphore _processing_sem
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// making sure the operation is only done by either VMThread/Handshaker on behalf
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// of the JavaThread or by the target JavaThread itself.
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class HandshakeState {
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JavaThread* _handshakee;
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HandshakeOperation* volatile _operation;
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HandshakeOperation* volatile _operation_direct;
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Semaphore _handshake_turn_sem; // Used to serialize direct handshakes for this JavaThread.
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Semaphore _processing_sem;
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bool _thread_in_process_handshake;
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bool claim_handshake(bool is_direct);
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bool possibly_can_process_handshake();
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bool can_process_handshake();
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void clear_handshake(bool is_direct);
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void process_self_inner();
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public:
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HandshakeState();
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void set_handshakee(JavaThread* thread) { _handshakee = thread; }
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void set_operation(HandshakeOperation* op);
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bool has_operation() const { return _operation != NULL || _operation_direct != NULL; }
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bool has_specific_operation(bool is_direct) const {
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return is_direct ? _operation_direct != NULL : _operation != NULL;
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}
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void process_by_self() {
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if (!_thread_in_process_handshake) {
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AutoModifyRestore<bool> temporarily(_thread_in_process_handshake, true);
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process_self_inner();
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}
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}
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enum ProcessResult {
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_no_operation = 0,
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_not_safe,
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_state_busy,
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_success,
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_number_states
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};
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ProcessResult try_process(HandshakeOperation* op);
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#ifdef ASSERT
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Thread* _active_handshaker;
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Thread* active_handshaker() const { return _active_handshaker; }
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#endif
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};
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#endif // SHARE_RUNTIME_HANDSHAKE_HPP
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