spin_rw_mutex.h

/*
    Copyright 2005-2011 Intel Corporation.  All Rights Reserved.

    The source code contained or described herein and all documents related
    to the source code ("Material") are owned by Intel Corporation or its
    suppliers or licensors.  Title to the Material remains with Intel
    Corporation or its suppliers and licensors.  The Material is protected
    by worldwide copyright laws and treaty provisions.  No part of the
    Material may be used, copied, reproduced, modified, published, uploaded,
    posted, transmitted, distributed, or disclosed in any way without
    Intel's prior express written permission.

    No license under any patent, copyright, trade secret or other
    intellectual property right is granted to or conferred upon you by
    disclosure or delivery of the Materials, either expressly, by
    implication, inducement, estoppel or otherwise.  Any license under such
    intellectual property rights must be express and approved by Intel in
    writing.
*/

#ifndef __TBB_spin_rw_mutex_H
#define __TBB_spin_rw_mutex_H

#include "tbb_stddef.h"
#include "tbb_machine.h"
#include "tbb_profiling.h"

namespace tbb {

class spin_rw_mutex_v3;
typedef spin_rw_mutex_v3 spin_rw_mutex;


class spin_rw_mutex_v3 {

    bool __TBB_EXPORTED_METHOD internal_acquire_writer();


    void __TBB_EXPORTED_METHOD internal_release_writer();

    void __TBB_EXPORTED_METHOD internal_acquire_reader();

    bool __TBB_EXPORTED_METHOD internal_upgrade();


    void __TBB_EXPORTED_METHOD internal_downgrade();

    void __TBB_EXPORTED_METHOD internal_release_reader();

    bool __TBB_EXPORTED_METHOD internal_try_acquire_writer();

    bool __TBB_EXPORTED_METHOD internal_try_acquire_reader();

public:
    spin_rw_mutex_v3() : state(0) {
#if TBB_USE_THREADING_TOOLS
        internal_construct();
#endif
    }

#if TBB_USE_ASSERT
    ~spin_rw_mutex_v3() {
        __TBB_ASSERT( !state, "destruction of an acquired mutex");
    };
#endif /* TBB_USE_ASSERT */


    class scoped_lock : internal::no_copy {
    public:

        scoped_lock() : mutex(NULL), is_writer(false) {}

        scoped_lock( spin_rw_mutex& m, bool write = true ) : mutex(NULL) {
            acquire(m, write);
        }

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

        void acquire( spin_rw_mutex& m, bool write = true ) {
            __TBB_ASSERT( !mutex, "holding mutex already" );
            is_writer = write; 
            mutex = &m;
            if( write ) mutex->internal_acquire_writer();
            else        mutex->internal_acquire_reader();
        }


        bool upgrade_to_writer() {
            __TBB_ASSERT( mutex, "lock is not acquired" );
            __TBB_ASSERT( !is_writer, "not a reader" );
            is_writer = true; 
            return mutex->internal_upgrade();
        }

        void release() {
            __TBB_ASSERT( mutex, "lock is not acquired" );
            spin_rw_mutex *m = mutex; 
            mutex = NULL;
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
            if( is_writer ) m->internal_release_writer();
            else            m->internal_release_reader();
#else
            if( is_writer ) __TBB_AtomicAND( &m->state, READERS ); 
            else            __TBB_FetchAndAddWrelease( &m->state, -(intptr_t)ONE_READER);
#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
        }

        bool downgrade_to_reader() {
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
            __TBB_ASSERT( mutex, "lock is not acquired" );
            __TBB_ASSERT( is_writer, "not a writer" );
            mutex->internal_downgrade();
#else
            __TBB_FetchAndAddW( &mutex->state, ((intptr_t)ONE_READER-WRITER));
#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
            is_writer = false;

            return true;
        }

        bool try_acquire( spin_rw_mutex& m, bool write = true ) {
            __TBB_ASSERT( !mutex, "holding mutex already" );
            bool result;
            is_writer = write; 
            result = write? m.internal_try_acquire_writer()
                          : m.internal_try_acquire_reader();
            if( result ) 
                mutex = &m;
            return result;
        }

    protected:
        spin_rw_mutex* mutex;


        bool is_writer;
    };

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

    // ISO C++0x compatibility methods

    void lock() {internal_acquire_writer();}


    bool try_lock() {return internal_try_acquire_writer();}

    void unlock() {
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
        if( state&WRITER ) internal_release_writer();
        else               internal_release_reader();
#else
        if( state&WRITER ) __TBB_AtomicAND( &state, READERS ); 
        else               __TBB_FetchAndAddWrelease( &state, -(intptr_t)ONE_READER);
#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
    }

    // Methods for reader locks that resemble ISO C++0x compatibility methods.

    void lock_read() {internal_acquire_reader();}


    bool try_lock_read() {return internal_try_acquire_reader();}

private:
    typedef intptr_t state_t;
    static const state_t WRITER = 1;
    static const state_t WRITER_PENDING = 2;
    static const state_t READERS = ~(WRITER | WRITER_PENDING);
    static const state_t ONE_READER = 4;
    static const state_t BUSY = WRITER | READERS;

    state_t state;

    void __TBB_EXPORTED_METHOD internal_construct();
};

__TBB_DEFINE_PROFILING_SET_NAME(spin_rw_mutex)

} // namespace tbb

#endif /* __TBB_spin_rw_mutex_H */

---

Copyright © 2005-2011 Intel Corporation. All Rights Reserved.

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