On Thu, 17 Mar 2016, Jens Axboe wrote:
> On 03/17/2016 09:42 AM, Jens Axboe wrote:
> > On 03/17/2016 05:01 AM, Thomas Gleixner wrote:
> > > On Thu, 17 Mar 2016, Peter Zijlstra wrote:
> > > > On Thu, Mar 17, 2016 at 12:39:46PM +0100, Thomas Gleixner wrote:
> > > > > But we have to clarify and document whether holes in
> > > > > cpu_possible_mask are not
> > > > > allowed at all or if code like the above is simply broken.
> > > >
> > > > So the general rule is that cpumasks can have holes, and exempting one
> > > > just muddles the water.
> > > >
> > > > Therefore I'd call the code just plain broken.
> > >
> > > Agreed.
> > >
> > > That macro is not really helping the readability of the code at all. So a
> > > simple for_each_possible_cpu() loop would have avoided that wreckage.
> >
> > Does the attached work? The rest of blk-mq should deal with holes just
Bah. Attachements ...
> > fine, we found some of those issues on sparc. Not sure why this one
> > slipped through the cracks.
>
> This might be better, we need to start at -1 to not miss the first one...
> Still untested.
> +static inline struct blk_mq_ctx *next_ctx(struct request_queue *q, int *i)
> +{
> + do {
> + (*i)++;
> + if (*i < q->nr_queues) {
> + if (cpu_possible(*i))
> + return per_cpu_ptr(q->queue_ctx, *i);
> + continue;
> + }
> + break;
> + } while (1);
> +
> + return NULL;
> +}
> +
> +#define queue_for_each_ctx(q, ctx, i)
> \
> + for ((i) = -1; (ctx = next_ctx((q), &(i))) != NULL;)
> +
What's wrong with
for_each_possible_cpu(cpu) {
ctx = per_cpu_ptr(q->queue_ctx, cpu);
....
}
instead of hiding it behind an incomprehensible macro mess?
Thanks,
tglx
