1 /*
   2  * Copyright (c) 2001, 2010, 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
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  24 
  25 #ifndef SHARE_VM_RUNTIME_THREADCRITICAL_HPP
  26 #define SHARE_VM_RUNTIME_THREADCRITICAL_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 
  30 // ThreadCritical is used to protect short non-blocking critical sections.
  31 // This class must use no vm facilities that require initialization.
  32 // It is used very early in the vm's initialization, in allocation
  33 // code and other areas. ThreadCritical regions are reentrant.
  34 //
  35 // Due to race conditions during vm exit, some of the os level
  36 // synchronization primitives may not be deallocated at exit. It
  37 // is a good plan to implement the platform dependent sections of
  38 // code with resources that are recoverable during process
  39 // cleanup by the os. Calling the initialize method before use
  40 // is also problematic, it is best to use preinitialized primitives
  41 // if possible. As an example:
  42 //
  43 // mutex_t  mp  =  DEFAULTMUTEX;
  44 //
  45 // Also note that this class is declared as a StackObj to enforce
  46 // block structured short locks. It cannot be declared a ResourceObj
  47 // or CHeapObj, due to initialization issues.
  48 
  49 class ThreadCritical : public StackObj {
  50  friend class os;
  51  private:
  52   static void initialize();
  53   static void release();
  54 
  55  public:
  56   ThreadCritical();
  57   ~ThreadCritical();
  58 };
  59 
  60 #endif // SHARE_VM_RUNTIME_THREADCRITICAL_HPP