Re: [PATCH]: jiffies wrap in ll_rw_blk.c

From: Luben Tuikov (luben@splentec.com)
Date: Wed Nov 20 2002 - 16:00:44 EST

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Alan Cox wrote:
>
> On Wed, 2002-11-20 at 20:44, Luben Tuikov wrote:
> > --- ll_rw_blk.c.old Wed Nov 20 15:32:50 2002
> > +++ ll_rw_blk.c Wed Nov 20 15:33:06 2002
> > @@ -2092,7 +2092,7 @@
> > complete(req->waiting);
> >
> > if (disk) {
> > - unsigned long duration = jiffies - req->start_time;
> > + unsigned long duration = (signed) jiffies - (signed) req->start_time;
> > switch (rq_data_dir(req)) {
>
> It was right before. Your patch breaks it. Think about it in unsigned
> maths
>
> 0x00000002 - 0xFFFFFFFF = 0x00000003

0x2 - (-0x1) = 0x2 + 0x1 = 0x3

Right! I thought (signed) does the job. I actually tried
it both ways and works all right. I guess either way works fine.

-- 
Luben
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