Re: [Starpu-devel] Heft/dmda: locking in compute_all_performance_predictions.

[Samuel Thibault <samuel.thibault@ens-lyon.org>]

Cyril Roelandt, le Thu 22 Nov 2012 18:26:15 +0100, a écrit :
> On 11/22/2012 06:08 PM, Samuel Thibault wrote:
> >Cyril Roelandt, le Thu 22 Nov 2012 17:16:36 +0100, a écrit :
> >>if (exp_end[worker][nimpl]>  max_exp_end)
> >>         max_exp_end = exp_end[worker][nimpl];
> >>_STARPU_PTHREAD_MUTEX_UNLOCK(&sched_mutex[worker])
> >>
> >>
> >>The exact same code can be found in compute_all_performance_predictions() 
> >>in
> >>dmda, except that we do not lock the worker's mutex. Why is that ?
> >
> >I believe it's simply a bug. One should indeed take the lock, to make
> >sure to be getting a coherent set of {exp_start, exp_len} values. It
> >might be useful to only read those in the critical section, or even turn
> >the mutex into an rwlock.
> >
> 
> OK. I'll keep using a mutex for now. While we are at it, do we really need
> to keep this:
> 
> if (exp_end[worker][nimpl]>  max_exp_end)
>          max_exp_end = exp_end[worker][nimpl];
> 
> in the critical section ?

No. max_exp_end used to be queue->exp_end, but it isn't any more.

Samuel