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_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.

    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_SHARED_SUSPENDIBLETHREADSET_HPP