20192
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1 /*
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2 * Copyright (c) 2014, Oracle and/or its affiliates. All rights reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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20 * or visit www.oracle.com if you need additional information or have any
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21 * questions.
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22 *
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23 */
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24
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25 #ifndef SHARE_VM_GC_IMPLEMENTATION_SHARED_SUSPENDIBLETHREADSET_HPP
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26 #define SHARE_VM_GC_IMPLEMENTATION_SHARED_SUSPENDIBLETHREADSET_HPP
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27
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28 #include "memory/allocation.hpp"
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29
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30 // A SuspendibleThreadSet is a set of threads that can be suspended.
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31 // A thread can join and later leave the set, and periodically yield.
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32 // If some thread (not in the set) requests, via synchronize(), that
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33 // the threads be suspended, then the requesting thread is blocked
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34 // until all the threads in the set have yielded or left the set. Threads
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35 // may not enter the set when an attempted suspension is in progress. The
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36 // suspending thread later calls desynchronize(), allowing the suspended
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37 // threads to continue.
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38 class SuspendibleThreadSet : public AllStatic {
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39 private:
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40 static uint _nthreads;
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41 static uint _nthreads_stopped;
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42 static bool _suspend_all;
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43 static double _suspend_all_start;
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44
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45 public:
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46 // Add the current thread to the set. May block if a suspension is in progress.
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47 static void join();
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48
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49 // Removes the current thread from the set.
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50 static void leave();
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51
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52 // Returns true if an suspension is in progress.
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53 static bool should_yield() { return _suspend_all; }
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54
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55 // Suspends the current thread if a suspension is in progress.
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56 static void yield();
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57
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58 // Returns when all threads in the set are suspended.
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59 static void synchronize();
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60
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61 // Resumes all suspended threads in the set.
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62 static void desynchronize();
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63 };
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64
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65 class SuspendibleThreadSetJoiner : public StackObj {
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66 public:
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67 SuspendibleThreadSetJoiner() {
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68 SuspendibleThreadSet::join();
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69 }
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70
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71 ~SuspendibleThreadSetJoiner() {
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72 SuspendibleThreadSet::leave();
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73 }
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74
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75 bool should_yield() {
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76 return SuspendibleThreadSet::should_yield();
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77 }
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78
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79 void yield() {
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80 SuspendibleThreadSet::yield();
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81 }
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82 };
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83
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84 #endif // SHARE_VM_GC_IMPLEMENTATION_SHARED_SUSPENDIBLETHREADSET_HPP
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