Re: 4.5.0+ panic when setup loop device

[Jens Axboe]

On 03/17/2016 01:30 PM, Thomas Gleixner wrote:
> On Thu, 17 Mar 2016, Jens Axboe wrote:
> > On 03/17/2016 01:20 PM, Thomas Gleixner wrote:
> > > > 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?
> >
> > We might not have mapped all of them.
>
> blk_mq_init_cpu_queues() tells a different story and q->queue_ctx is a per_cpu
> allocation.

Yeah my bad, I mistook the possible for online. So we can do the easier fix.

--
Jens Axboe