1/*
2 * Copyright (c) 2017, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
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23 */
24
25#ifndef SHARE_RUNTIME_HANDSHAKE_HPP
26#define SHARE_RUNTIME_HANDSHAKE_HPP
27
28#include "memory/allocation.hpp"
29#include "runtime/flags/flagSetting.hpp"
30#include "runtime/semaphore.hpp"
31
32class ThreadClosure;
33class JavaThread;
34
35// A handshake operation is a callback that is executed for each JavaThread
36// while that thread is in a safepoint safe state. The callback is executed
37// either by the thread itself or by the VM thread while keeping the thread
38// in a blocked state. A handshake can be performed with a single
39// JavaThread as well.
40class Handshake : public AllStatic {
41 public:
42 // Execution of handshake operation
43 static void execute(ThreadClosure* thread_cl);
44 static bool execute(ThreadClosure* thread_cl, JavaThread* target);
45};
46
47class HandshakeOperation;
48
49// The HandshakeState keep tracks of an ongoing handshake for one JavaThread.
50// VM thread and JavaThread are serialized with the semaphore making sure
51// the operation is only done by either VM thread on behalf of the JavaThread
52// or the JavaThread itself.
53class HandshakeState {
54 HandshakeOperation* volatile _operation;
55
56 Semaphore _semaphore;
57 bool _thread_in_process_handshake;
58
59 bool claim_handshake_for_vmthread();
60 bool vmthread_can_process_handshake(JavaThread* target);
61
62 void clear_handshake(JavaThread* thread);
63
64 void process_self_inner(JavaThread* thread);
65public:
66 HandshakeState();
67
68 void set_operation(JavaThread* thread, HandshakeOperation* op);
69
70 bool has_operation() const {
71 return _operation != NULL;
72 }
73
74 void process_by_self(JavaThread* thread) {
75 if (!_thread_in_process_handshake) {
76 FlagSetting fs(_thread_in_process_handshake, true);
77 process_self_inner(thread);
78 }
79 }
80
81 void process_by_vmthread(JavaThread* target);
82};
83
84#endif // SHARE_RUNTIME_HANDSHAKE_HPP
85