Subj : Re: Optimization to Jeffrey Richter's COptex (Windows)?
To   : comp.programming.threads
From : SenderX
Date : Wed Jan 26 2005 06:44 pm


"SenderX" <xxx@xxx.com> wrote in message 
news:q7Gdnd5ISYrPhmXcRVn-2w@comcast.com...
>> http://www.microsoft.com/msj/0198/win320198.aspx
>> http://www.microsoft.com/msj/0198/win32textfigs.htm#fig2
>
> This is crap. Use the mutex logic that Alex suggested.
>
>


typedef struct optex_
{
    volatile ac_uatomic_t state;
    HANDLE waitset;
    int recurse;
    ac_thread_t owner;

}    optex_t;


void optex_lock( optex_t *_this )
{
    register ac_uatomic_t cmp, xchg, old;

    ac_thread_t thisthread = ac_thread_self();

    if ( ! ac_thread_equal( _this->owner, thisthread ) )
    {
        ++_this->recurse;
        return;
    }

    old = _this->state;

    for ( ;; )
    {
        if ( ! ( old & 0x80000000 ) )
        {
            xchg = old | 0x80000000;
        }

        else { xchg = old + 1; }

        cmp = old;

        old = ac_atomic_cas_acq_dep( &_this->state, old, xchg );

        if ( cmp == old )
        {
            if ( ! ( old & 0x80000000 ) ) { break; }

            WaitForSingleObject( _this->waitset, INFINITE );

            old = _this->state;
        }
    };

    _this->owner = thisthread;
}


void optex_unlock( optex_t *_this )
{
    register ac_uatomic_t cmp, xchg, old;

    if ( _this->recurse )
    {
        --_this->recurse;
        return;
    }

    _this->owner = AC_THREAD_NULL;

    old = _this->state;

    do
    {
        xchg = old & 0x0FFFFFFF;

        if ( xchg ) { --xchg; }

        cmp = old;

        old = ac_atomic_cas_rel( &_this->state, old, xchg );
    }

    while ( old != cmp );

    if ( old & 0x0FFFFFFF )
    {
        ReleaseSemaphore( _this->waitset, 1, 0 );
    }
}

.