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. 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 21 * questions. 22 * 23 */ 24 25 #ifndef SHARE_GC_COMMON_SUSPENDIBLETHREADSET_HPP 26 #define SHARE_GC_COMMON_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. 38 class SuspendibleThreadSet : public AllStatic { 39 friend class SuspendibleThreadSetJoiner; 40 friend class SuspendibleThreadSetLeaver; 41 42 private: 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 56 public: 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 70 class SuspendibleThreadSetJoiner : public StackObj { 71 private: 72 bool _active; 73 74 public: 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 }; 100 101 class SuspendibleThreadSetLeaver : public StackObj { 102 private: 103 bool _active; 104 105 public: 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_COMMON_SUSPENDIBLETHREADSET_HPP