linux-kernel - Re: [PATCH] ARM: Fix find_next_zero

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Message-id: <alpine.LFD.2.00.1011241412250.9313@xanadu.home>
Date:	Wed, 24 Nov 2010 14:13:05 -0500 (EST)
From:	Nicolas Pitre <nico@...xnic.net>
To:	James Jones <jajones@...dia.com>
Cc:	Stephen Boyd <sboyd@...eaurora.org>,
	Russell King <linux@....linux.org.uk>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] ARM: Fix find_next_zero_bit and related assembly

On Wed, 24 Nov 2010, James Jones wrote:

> On Wednesday 24 November 2010 11:00:12 am Nicolas Pitre wrote:
> > On Wed, 24 Nov 2010, Stephen Boyd wrote:
> > > On 11/23/2010 03:28 PM, James Jones wrote:
> > > > On Tuesday 23 November 2010 13:26:47 Nicolas Pitre wrote:
> > > >> On Thu, 11 Nov 2010, James Jones wrote:
> > > >>> The find_next_bit, find_first_bit, find_next_zero_bit
> > > >>> and find_first_zero_bit functions were not properly
> > > >>> clamping to the maxbit argument at the bit level. They
> > > >>> were instead only checking maxbit at the byte level.
> > > >>> To fix this, add a compare and a conditional move
> > > >>> instruction to the end of the common bit-within-the-
> > > >>> byte code used by all the functions and be sure not to
> > > >>> clobber the maxbit argument before it is used.
> > > >>> 
> > > >>> Signed-off-by: James Jones <jajones@...dia.com>
> > > >>> Tested-by: Stephen Warren <swarren@...dia.com>
> > > >> 
> > > >> Reviewed-by: Nicolas Pitre <nicolas.pitre@...aro.org>
> > > >> 
> > > >> Please send to RMK's patch system.
> > > > 
> > > > Thanks for the review.  It's already in the patch system, but I updated
> > > > the entry to include your reviewed-by line.
> > > 
> > > Should this be sent to the stable tree too?
> > 
> > It could, yes.  This is hardly an urgent fix though, as the bug has been
> > there virtually forever.
> > 
> > 
> > Nicolas
> 
> While ancient, it does cause per-cpu allocations to fail in some situations, 
> which generally causes panics.

That would be a good justification for the stable tree then.


Nicolas
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