/*

 * Copyright (c) 2001, 2010, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#ifndef SHARE_VM_RUNTIME_THREADCRITICAL_HPP

#define SHARE_VM_RUNTIME_THREADCRITICAL_HPP

#include "memory/allocation.hpp"

// ThreadCritical is used to protect short non-blocking critical sections.

// This class must use no vm facilities that require initialization.

// It is used very early in the vm's initialization, in allocation

// code and other areas. ThreadCritical regions are reentrant.

//

// Due to race conditions during vm exit, some of the os level

// synchronization primitives may not be deallocated at exit. It

// is a good plan to implement the platform dependent sections of

// code with resources that are recoverable during process

// cleanup by the os. Calling the initialize method before use

// is also problematic, it is best to use preinitialized primitives

// if possible. As an example:

//

// mutex_t  mp  =  DEFAULTMUTEX;

//

// Also note that this class is declared as a StackObj to enforce

// block structured short locks. It cannot be declared a ResourceObj

// or CHeapObj, due to initialization issues.

class ThreadCritical : public StackObj {

 friend class os;

 private:

  static void initialize();

  static void release();

 public:

  ThreadCritical();

  ~ThreadCritical();

};

#endif // SHARE_VM_RUNTIME_THREADCRITICAL_HPP