1 /*
   2  * Copyright (c) 2018, 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_UTILITIES_WAITBARRIER_HPP
  26 #define SHARE_UTILITIES_WAITBARRIER_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "utilities/waitBarrier_generic.hpp"
  30 
  31 #if defined(LINUX)
  32 #include "waitBarrier_linux.hpp"
  33 typedef LinuxWaitBarrier WaitBarrierDefault;
  34 #else
  35 typedef GenericWaitBarrier WaitBarrierDefault;
  36 #endif
  37 
  38 // Platform independent WaitBarrier API.
  39 // The WaitBarrier primary objective is to wake threads waiting in wait() fast.
  40 // It can be arm with any int, the tag, that is not 0.
  41 // - After arm() returns any thread calling wait(tag) with the correct tag will be blocked.
  42 // - After disarm() is called any thread calling wait(...) will never block.
  43 // - When wake() returns no threads are blocked any more, if it was disarmed before.
  44 // - After calling disarm() and wake() it my be re-armed immediately.
  45 // Wake thread:
  46 //  - arm(tag)
  47 //  - *work*
  48 //  - disarm()
  49 //  - wake()
  50 // Wait thread:
  51 //  - wait(tag)
  52 template <typename WaitBarrierImpl>
  53 class WaitBarrierType : public CHeapObj<mtInternal> {
  54   WaitBarrierImpl _impl;
  55 
  56   // Prevent copying and assignment of WaitBarrier instances.
  57   WaitBarrierType(const WaitBarrierDefault&);
  58   WaitBarrierType& operator=(const WaitBarrierDefault&);
  59 
  60  public:
  61   WaitBarrierType() : _impl() {}
  62   ~WaitBarrierType() {}
  63 
  64   // Returns implementation type.
  65   const char* description()    { return _impl.description(); }
  66 
  67   // Guarantees any thread calling wait() with same tag will be blocked.
  68   // Provides a trailing fence.
  69   void arm(int barrier_tag)    { _impl.arm(barrier_tag); }
  70 
  71   // Guarantees any thread calling wait() with any tag will not be blocked.
  72   // Provides a trailing fence.
  73   void disarm()                { _impl.disarm(); }
  74 
  75   // Guarantees any thread called wait() will be awake when it returns.
  76   // Provides a trailing fence.
  77   void wake()                  { _impl.wake(); }
  78 
  79   // Guarantees to return if disarm() and wake() is called.
  80   // Provides a trailing fence.
  81   void wait(int barrier_tag)   { _impl.wait(barrier_tag); }
  82 };
  83 
  84 typedef WaitBarrierType<WaitBarrierDefault> WaitBarrier;
  85 
  86 #endif // SHARE_UTILITIES_WAITBARRIER_HPP