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SubjectRe: Problems with the block-layer timeouts
From
On Mon, 3 Nov 2008 09:52:48 +0100
Jens Axboe <jens.axboe@oracle.com> wrote:

> > In blk_del_timer(), there's no reason to test q->rq_timed_out_fn. If
> > the method pointer is NULL then req->deadline would be 0 anyway. In
> > addition, req->deadline should be set to 0 and the end of the routine,
> > just in case req gets requeued.
> >
> > In blk_add_timer(), the line
> >
> > expiry = round_jiffies(req->deadline);
> >
> > is not optimal. round_jiffies() will sometimes round a value _down_ to
> > the nearest second. But blk_rq_timed_out_timer() tests whether
> > req->deadline is in the past -- and if the deadline was rounded down
> > then this won't be true the first time through. You wind up getting an
> > unnecessary timer interrupt. Instead there should be a
> > round_jiffies_up() utility routine, and it should be used in both
> > blk_add_timer() and blk_rq_timed_out_timer().
>
> Very good point, we do indeed want a round_jiffies_up() for this!

Just out of curiosity, why do we need to use round_jiffies here? We
didn't do that for SCSI, right?


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