On Thu, Aug 25, 2022 at 08:09:50AM +0200, Hannes Reinecke wrote:
> > +static bool __sbq_wake_up(struct sbitmap_queue *sbq, int *nr)
>
> Why is '*nr' a pointer? It's always used as a value, so what does promoting
> it to a point buys you?
Not quite, see below:
> > {
> > 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);
> > + sub = min3(wake_batch, *nr, cur);
> > + wait_cnt = cur - sub;
> > + } while (!atomic_try_cmpxchg(&ws->wait_cnt, &cur, wait_cnt));
> > +
> > + *nr -= sub;
Dereferenced here to account for how many bits were considered for this wake
cycle.
