On Thu, Aug 25, 2022 at 01:48:43PM +0200, Pankaj Raghav wrote:
> On Wed, Aug 24, 2022 at 01:14:40PM -0700, Keith Busch wrote:
> >
> > -static bool __sbq_wake_up(struct sbitmap_queue *sbq)
> > +static bool __sbq_wake_up(struct sbitmap_queue *sbq, int *nr)
> > {
> > struct sbq_wait_state *ws;
> > - unsigned int wake_batch;
> > - int wait_cnt;
> > + int wake_batch, wait_cnt, sub, cur;
> >
> > ws = sbq_wake_ptr(sbq);
> > if (!ws)
> > return false;
> >
> > - wait_cnt = atomic_dec_return(&ws->wait_cnt);
> > + wake_batch = READ_ONCE(sbq->wake_batch);
> > + do {
> > + cur = atomic_read(&ws->wait_cnt);
>
> I think the above statement is not needed if we use atomic_try_cmpxchg
> as the old value is updated in that function itself.
> https://docs.kernel.org/staging/index.html?highlight=atomic_try_cmpxchg#atomic-types
I mean after moving the cur = atomic_read(..) above the do statement:
wake_batch = READ_ONCE(sbq->wake_batch);
cur = atomic_read(&ws->wait_cnt);
do {
sub = min3(wake_batch, *nr, cur);
wait_cnt = cur - sub;
} while (!atomic_try_cmpxchg(&ws->wait_cnt, &cur, wait_cnt));
--
Pankaj Raghav
