1/*
2 * Copyright (c) 2014, 2017, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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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).
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24
25#ifndef SHARE_GC_SHARED_SUSPENDIBLETHREADSET_HPP
26#define SHARE_GC_SHARED_SUSPENDIBLETHREADSET_HPP
27
28#include "memory/allocation.hpp"
29
30// A SuspendibleThreadSet is a set of threads that can be suspended.
31// A thread can join and later leave the set, and periodically yield.
32// If some thread (not in the set) requests, via synchronize(), that
33// the threads be suspended, then the requesting thread is blocked
34// until all the threads in the set have yielded or left the set. Threads
35// may not enter the set when an attempted suspension is in progress. The
36// suspending thread later calls desynchronize(), allowing the suspended
37// threads to continue.
38class SuspendibleThreadSet : public AllStatic {
39 friend class SuspendibleThreadSetJoiner;
40 friend class SuspendibleThreadSetLeaver;
41
42private:
43 static uint _nthreads;
44 static uint _nthreads_stopped;
45 static bool _suspend_all;
46 static double _suspend_all_start;
47
48 static bool is_synchronized();
49
50 // Add the current thread to the set. May block if a suspension is in progress.
51 static void join();
52
53 // Removes the current thread from the set.
54 static void leave();
55
56public:
57 // Returns true if an suspension is in progress.
58 static bool should_yield() { return _suspend_all; }
59
60 // Suspends the current thread if a suspension is in progress.
61 static void yield();
62
63 // Returns when all threads in the set are suspended.
64 static void synchronize();
65
66 // Resumes all suspended threads in the set.
67 static void desynchronize();
68};
69
70class SuspendibleThreadSetJoiner : public StackObj {
71private:
72 bool _active;
73
74public:
75 SuspendibleThreadSetJoiner(bool active = true) : _active(active) {
76 if (_active) {
77 SuspendibleThreadSet::join();
78 }
79 }
80
81 ~SuspendibleThreadSetJoiner() {
82 if (_active) {
83 SuspendibleThreadSet::leave();
84 }
85 }
86
87 bool should_yield() {
88 if (_active) {
89 return SuspendibleThreadSet::should_yield();
90 } else {
91 return false;
92 }
93 }
94
95 void yield() {
96 assert(_active, "Thread has not joined the suspendible thread set");
97 SuspendibleThreadSet::yield();
98 }
99};
100
101class SuspendibleThreadSetLeaver : public StackObj {
102private:
103 bool _active;
104
105public:
106 SuspendibleThreadSetLeaver(bool active = true) : _active(active) {
107 if (_active) {
108 SuspendibleThreadSet::leave();
109 }
110 }
111
112 ~SuspendibleThreadSetLeaver() {
113 if (_active) {
114 SuspendibleThreadSet::join();
115 }
116 }
117};
118
119#endif // SHARE_GC_SHARED_SUSPENDIBLETHREADSET_HPP
120