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Date: Wed, 20 Nov 2002 17:20:54 -0500
From: Olivier Galibert <galibert@pobox.com>
To: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH]: jiffies wrap in ll_rw_blk.c
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References: <3DDBF413.C06DAF2E@splentec.com> <1037827173.3267.78.camel@irongate.swansea.linux.org.uk>
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In-Reply-To: <1037827173.3267.78.camel@irongate.swansea.linux.org.uk>; from alan@lxorguk.ukuu.org.uk on Wed, Nov 20, 2002 at 09:19:33PM +0000
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On Wed, Nov 20, 2002 at 09:19:33PM +0000, 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

Signed vs. unsigned is actually irrelevant in two-complement systems
as long as you don't compare.  Only the int/long issue has an actual
effect.

  OG.

-
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