_x86_eliding_mutex_impl.h

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/*
    Copyright (c) 2005-2020 Intel Corporation

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

        http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
*/

#ifndef __TBB__x86_eliding_mutex_impl_H
#define __TBB__x86_eliding_mutex_impl_H

#ifndef __TBB_spin_mutex_H
#error Do not #include this internal file directly; use public TBB headers instead.
#endif

#if ( __TBB_x86_32 || __TBB_x86_64 )

namespace tbb {
namespace interface7 {
namespace internal {

template<typename Mutex, bool is_rw>
class padded_mutex;


class x86_eliding_mutex : tbb::internal::mutex_copy_deprecated_and_disabled {
    __TBB_atomic_flag flag;

    friend class padded_mutex<x86_eliding_mutex, false>;

public:

    x86_eliding_mutex() : flag(0) {}

// bug in gcc 3.x.x causes syntax error in spite of the friend declaration above.
// Make the scoped_lock public in that case.
#if __TBB_USE_X86_ELIDING_MUTEX || __TBB_GCC_VERSION < 40000
#else
    // by default we will not provide the scoped_lock interface.  The user
    // should use the padded version of the mutex.  scoped_lock is used in
    // padded_mutex template.
private:
#endif
    // scoped_lock in padded_mutex<> is the interface to use.
    class scoped_lock : tbb::internal::no_copy {
    private:
        x86_eliding_mutex* my_mutex;

    public:
        scoped_lock() : my_mutex(NULL) {}

        scoped_lock( x86_eliding_mutex& m ) : my_mutex(NULL) { acquire(m); }

        void acquire( x86_eliding_mutex& m ) {
            __TBB_ASSERT( !my_mutex, "already holding a lock" );

            my_mutex=&m;
            my_mutex->lock();
        }


        bool try_acquire( x86_eliding_mutex& m ) {
            __TBB_ASSERT( !my_mutex, "already holding a lock" );

            bool result = m.try_lock();
            if( result ) {
                my_mutex = &m;
            }
            return result;
        }

        void release() {
            __TBB_ASSERT( my_mutex, "release on scoped_lock that is not holding a lock" );

            my_mutex->unlock();
            my_mutex = NULL;
        }

        ~scoped_lock() {
            if( my_mutex ) {
                release();
            }
        }
    };
#if __TBB_USE_X86_ELIDING_MUTEX || __TBB_GCC_VERSION < 40000
#else
public:
#endif  /* __TBB_USE_X86_ELIDING_MUTEX */

    // 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() {
        __TBB_LockByteElided(flag);
    }


    bool try_lock() {
        return __TBB_TryLockByteElided(flag);
    }

    void unlock() {
        __TBB_UnlockByteElided( flag );
    }
}; // end of x86_eliding_mutex

} // namespace internal
} // namespace interface7
} // namespace tbb

#endif /* ( __TBB_x86_32 || __TBB_x86_64 ) */

#endif /* __TBB__x86_eliding_mutex_impl_H */