queuing_rw_mutex.h

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/*
    Copyright 2005-2010 Intel Corporation.  All Rights Reserved.

    This file is part of Threading Building Blocks.

    Threading Building Blocks is free software; you can redistribute it
    and/or modify it under the terms of the GNU General Public License
    version 2 as published by the Free Software Foundation.

    Threading Building Blocks 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 for more details.

    You should have received a copy of the GNU General Public License
    along with Threading Building Blocks; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    As a special exception, you may use this file as part of a free software
    library without restriction.  Specifically, if other files instantiate
    templates or use macros or inline functions from this file, or you compile
    this file and link it with other files to produce an executable, this
    file does not by itself cause the resulting executable to be covered by
    the GNU General Public License.  This exception does not however
    invalidate any other reasons why the executable file might be covered by
    the GNU General Public License.
*/

#ifndef __TBB_queuing_rw_mutex_H
#define __TBB_queuing_rw_mutex_H

#include "tbb_config.h"

#if !TBB_USE_EXCEPTIONS && _MSC_VER
    // Suppress "C++ exception handler used, but unwind semantics are not enabled" warning in STL headers
    #pragma warning (push)
    #pragma warning (disable: 4530)
#endif

#include <cstring>

#if !TBB_USE_EXCEPTIONS && _MSC_VER
    #pragma warning (pop)
#endif

#include "atomic.h"
#include "tbb_profiling.h"

namespace tbb {


class queuing_rw_mutex {
public:
    queuing_rw_mutex() {
        q_tail = NULL;
#if TBB_USE_THREADING_TOOLS
        internal_construct();
#endif
    }

    ~queuing_rw_mutex() {
#if TBB_USE_ASSERT
        __TBB_ASSERT( !q_tail, "destruction of an acquired mutex");
#endif
    }

    class scoped_lock;
    friend class scoped_lock;


    class scoped_lock: internal::no_copy {
        void initialize() {
            mutex = NULL;
#if TBB_USE_ASSERT
            state = 0xFF; // Set to invalid state
            internal::poison_pointer(next);
            internal::poison_pointer(prev);
#endif /* TBB_USE_ASSERT */
        }
    public:

        scoped_lock() {initialize();}

        scoped_lock( queuing_rw_mutex& m, bool write=true ) {
            initialize();
            acquire(m,write);
        }

        ~scoped_lock() {
            if( mutex ) release();
        }

        void acquire( queuing_rw_mutex& m, bool write=true );

        bool try_acquire( queuing_rw_mutex& m, bool write=true );

        void release();


        bool upgrade_to_writer();

        bool downgrade_to_reader();

    private:
        queuing_rw_mutex* mutex;

        scoped_lock * prev, * next;

        typedef unsigned char state_t;

        atomic<state_t> state;


        unsigned char going;

        unsigned char internal_lock;

        void acquire_internal_lock();


        bool try_acquire_internal_lock();

        void release_internal_lock();

        void wait_for_release_of_internal_lock();

        void unblock_or_wait_on_internal_lock( uintptr_t );
    };

    void __TBB_EXPORTED_METHOD internal_construct();

    // Mutex traits
    static const bool is_rw_mutex = true;
    static const bool is_recursive_mutex = false;
    static const bool is_fair_mutex = true;

private:
    atomic<scoped_lock*> q_tail;

};

__TBB_DEFINE_PROFILING_SET_NAME(queuing_rw_mutex)

} // namespace tbb

#endif /* __TBB_queuing_rw_mutex_H */