spin_mutex.h

/*
    Copyright 2005-2016 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_spin_mutex_H
#define __TBB_spin_mutex_H

#include <cstddef>
#include <new>
#include "aligned_space.h"
#include "tbb_stddef.h"
#include "tbb_machine.h"
#include "tbb_profiling.h"
#include "internal/_mutex_padding.h"

namespace tbb {


class spin_mutex : internal::mutex_copy_deprecated_and_disabled {
    __TBB_atomic_flag flag;

public:

    spin_mutex() : flag(0) {
#if TBB_USE_THREADING_TOOLS
        internal_construct();
#endif
    }

    class scoped_lock : internal::no_copy {
    private:
        spin_mutex* my_mutex;


        __TBB_Flag my_unlock_value;

        void __TBB_EXPORTED_METHOD internal_acquire( spin_mutex& m );

        bool __TBB_EXPORTED_METHOD internal_try_acquire( spin_mutex& m );

        void __TBB_EXPORTED_METHOD internal_release();

        friend class spin_mutex;

    public:
        scoped_lock() : my_mutex(NULL), my_unlock_value(0) {}

        scoped_lock( spin_mutex& m ) : my_unlock_value(0) {
            internal::suppress_unused_warning(my_unlock_value);
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
            my_mutex=NULL;
            internal_acquire(m);
#else
            my_mutex=&m;
            __TBB_LockByte(m.flag);
#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/
        }

        void acquire( spin_mutex& m ) {
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
            internal_acquire(m);
#else
            my_mutex = &m;
            __TBB_LockByte(m.flag);
#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/
        }


        bool try_acquire( spin_mutex& m ) {
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
            return internal_try_acquire(m);
#else
            bool result = __TBB_TryLockByte(m.flag);
            if( result )
                my_mutex = &m;
            return result;
#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT*/
        }

        void release() {
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
            internal_release();
#else
            __TBB_UnlockByte(my_mutex->flag);
            my_mutex = NULL;
#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
        }

        ~scoped_lock() {
            if( my_mutex ) {
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
                internal_release();
#else
                __TBB_UnlockByte(my_mutex->flag);
#endif /* TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT */
            }
        }
    };

    void __TBB_EXPORTED_METHOD internal_construct();

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

    // ISO C++0x compatibility methods

    void lock() {
#if TBB_USE_THREADING_TOOLS
        aligned_space<scoped_lock> tmp;
        new(tmp.begin()) scoped_lock(*this);
#else
        __TBB_LockByte(flag);
#endif /* TBB_USE_THREADING_TOOLS*/
    }


    bool try_lock() {
#if TBB_USE_THREADING_TOOLS
        aligned_space<scoped_lock> tmp;
        return (new(tmp.begin()) scoped_lock)->internal_try_acquire(*this);
#else
        return __TBB_TryLockByte(flag);
#endif /* TBB_USE_THREADING_TOOLS*/
    }

    void unlock() {
#if TBB_USE_THREADING_TOOLS
        aligned_space<scoped_lock> tmp;
        scoped_lock& s = *tmp.begin();
        s.my_mutex = this;
        s.internal_release();
#else
        __TBB_store_with_release(flag, 0);
#endif /* TBB_USE_THREADING_TOOLS */
    }

    friend class scoped_lock;
}; // end of spin_mutex

__TBB_DEFINE_PROFILING_SET_NAME(spin_mutex)

} // namespace tbb

#if ( __TBB_x86_32 || __TBB_x86_64 )
#include "internal/_x86_eliding_mutex_impl.h"
#endif

namespace tbb {

#if ( __TBB_x86_32 || __TBB_x86_64 )
typedef interface7::internal::padded_mutex<interface7::internal::x86_eliding_mutex,false> speculative_spin_mutex;
#else
typedef interface7::internal::padded_mutex<spin_mutex,false> speculative_spin_mutex;
#endif
__TBB_DEFINE_PROFILING_SET_NAME(speculative_spin_mutex)

} // namespace tbb

#endif /* __TBB_spin_mutex_H */