Subj : Re: experimental smr-based 100% lock-free eventcount schema for windows...
To   : comp.programming.threads
From : SenderX
Date : Tue Feb 01 2005 06:19 pm

There a race-condition wrt incrementing the eventcount and signalling...


> typedef struct ac_event_count_
> {
> volatile ac_waitset_t *active_waitset;
> DWORD ec;
>
> } ac_event_count_t;

needs to be modified atomically using dwcas. Here is what I am getting at 
for the waiting side:



DWORD ac_event_count_wait
( ac_event_count_t *_this,
  DWORD ec_cmp,
  DWORD timeout )
{
    register ac_event_count_t cmp, xchg;
    regitser ac_waitset_t *local_waitset = 0;
    void **hazard = ac_lfgc_get_hazard( 1 );

    cmp.ec = _this->ec;
    cmp.active_waitset = _this->active_waitset;

    do
    {
        xchg.cmp = cmp.ec;

        if ( cmp.ec == ec_cmp )
        {
            if ( ! cmp.active_waitset )
            {
                if ( ! local_waitset )
                {
                    local_waitset =
                        ac_waitset_cache_pop( &global_cache );
                }

                xchg.active_waitset = local_waitset;
            }

            else
            {
                xchg.active_waitset = cmp.active_waitset;
            }
        }

        else
        {
            xchg.active_waitset = cmp.active_waitset;
        }

        *hazard = xchg.active_waitset;
    }

    while ( ! np_ac_atomic_dwcas_acq_dep
                ( _this,
                  &cmp,
                  &xchg ) );

    [ ... ]
}



More to come a bit later...

.