1 /* 2 * Copyright (c) 2014, 2015, 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_VM_GC_IMPLEMENTATION_SHARED_SUSPENDIBLETHREADSET_HPP 26 #define SHARE_VM_GC_IMPLEMENTATION_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. 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 // Add the current thread to the set. May block if a suspension is in progress. 49 static void join(); 50 51 // Removes the current thread from the set. 52 static void leave(); 53 54 public: 55 // Returns true if an suspension is in progress. 56 static bool should_yield() { return _suspend_all; } 57 58 // Suspends the current thread if a suspension is in progress. 59 static void yield(); 60 61 // Returns when all threads in the set are suspended. 62 static void synchronize(); 63 64 // Resumes all suspended threads in the set. 65 static void desynchronize(); 66 }; 67 68 class SuspendibleThreadSetJoiner : public StackObj { 69 private: 70 bool _active; 71 72 public: 73 SuspendibleThreadSetJoiner(bool active = true) : _active(active) { 74 if (_active) { 75 SuspendibleThreadSet::join(); 76 } 77 } 78 79 ~SuspendibleThreadSetJoiner() { 80 if (_active) { 81 SuspendibleThreadSet::leave(); 82 } 83 } 84 85 bool should_yield() { 86 if (_active) { 87 return SuspendibleThreadSet::should_yield(); 88 } else { 89 return false; 90 } 91 } 92 93 void yield() { 94 assert(_active, "Thread has not joined the suspendible thread set"); 95 SuspendibleThreadSet::yield(); 96 } 97 }; 98 99 class SuspendibleThreadSetLeaver : public StackObj { 100 private: 101 bool _active; 102 103 public: 104 SuspendibleThreadSetLeaver(bool active = true) : _active(active) { 105 if (_active) { 106 SuspendibleThreadSet::leave(); 107 } 108 } 109 110 ~SuspendibleThreadSetLeaver() { 111 if (_active) { 112 SuspendibleThreadSet::join(); 113 } 114 } 115 }; 116 117 #endif // SHARE_VM_GC_IMPLEMENTATION_SHARED_SUSPENDIBLETHREADSET_HPP