spin_rw_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_rw_mutex_H
#define __TBB_spin_rw_mutex_H

#include "tbb_stddef.h"
#include "tbb_machine.h"
#include "tbb_profiling.h"
#include "internal/_mutex_padding.h"

namespace tbb {

#if __TBB_TSX_AVAILABLE
namespace interface8 { namespace internal {
    class x86_rtm_rw_mutex;
}}
#endif

class spin_rw_mutex_v3;
typedef spin_rw_mutex_v3 spin_rw_mutex;


class spin_rw_mutex_v3 : internal::mutex_copy_deprecated_and_disabled {

    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 {
#if __TBB_TSX_AVAILABLE
        friend class tbb::interface8::internal::x86_rtm_rw_mutex;
        // helper methods for x86_rtm_rw_mutex
        spin_rw_mutex *internal_get_mutex() const { return mutex; }
        void internal_set_mutex(spin_rw_mutex* m) { mutex = m; }
#endif
    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() {
            __TBB_ASSERT( mutex, "lock is not acquired" );
            __TBB_ASSERT( is_writer, "not a writer" );
#if TBB_USE_THREADING_TOOLS||TBB_USE_ASSERT
            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();}

protected:
    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;

private:
    void __TBB_EXPORTED_METHOD internal_construct();
};

__TBB_DEFINE_PROFILING_SET_NAME(spin_rw_mutex)

} // namespace tbb

#if __TBB_TSX_AVAILABLE
#include "internal/_x86_rtm_rw_mutex_impl.h"
#endif

namespace tbb {
namespace interface8 {

#if __TBB_TSX_AVAILABLE
typedef interface7::internal::padded_mutex<tbb::interface8::internal::x86_rtm_rw_mutex,true> speculative_spin_rw_mutex;
#else
typedef interface7::internal::padded_mutex<tbb::spin_rw_mutex,true> speculative_spin_rw_mutex;
#endif
}  // namespace interface8

using interface8::speculative_spin_rw_mutex;
__TBB_DEFINE_PROFILING_SET_NAME(speculative_spin_rw_mutex)
} // namespace tbb
#endif /* __TBB_spin_rw_mutex_H */