From: Dave Chinner <dchinner@redhat.com>
To: Dan Carpenter <error27@gmail.com>
Cc: "open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>
Subject: Re: vmscan: shrinker->nr updates race and go wrong
Date: Wed, 20 Jul 2011 13:53:32 +1000 [thread overview]
Message-ID: <20110720035332.GC24009@devil.redhat.com> (raw)
In-Reply-To: <20110719200826.GC6445@shale.localdomain>
On Tue, Jul 19, 2011 at 11:08:26PM +0300, Dan Carpenter wrote:
> Hi Dave,
>
> There is a sign error in e5b94d7463e0 "vmscan: shrinker->nr updates
> race and go wrong"
>
> mm/vmscan.c +274 shrink_slab(41)
> warn: unsigned 'total_scan' is never less than zero.
>
> 268 total_scan = nr;
> 269 max_pass = do_shrinker_shrink(shrinker, shrink, 0);
> 270 delta = (4 * nr_pages_scanned) / shrinker->seeks;
> 271 delta *= max_pass;
> 272 do_div(delta, lru_pages + 1);
> 273 total_scan += delta;
> 274 if (total_scan < 0) {
> ^^^^^^^^^^^^^^
> total_scan is unsigned so it's never less than zero here.
Obviously. You'd think a kernel build would warn about that given
that it's almost always a bug, wouldn't you?
I'll send a patch to fix it up....
Cheers,
Dave.
--
Dave Chinner
dchinner@redhat.com
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prev parent reply other threads:[~2011-07-20 3:53 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-07-19 20:08 vmscan: shrinker->nr updates race and go wrong Dan Carpenter
2011-07-20 3:53 ` Dave Chinner [this message]
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