linux-kernel - Re: [patch] x86, UV: integer wrap bug in uv_hub_ipi

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Date:	Tue, 20 Nov 2012 07:28:56 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Russ Anderson <rja@....com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Jack Steiner <steiner@....com>,
	Dimitri Sivanich <sivanich@....com>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	rja@...ricas.sgi.com
Subject: Re: [patch] x86, UV: integer wrap bug in uv_hub_ipi_value()

On Mon, Nov 19, 2012 at 06:48:34PM -0600, Russ Anderson wrote:
> On Sat, Nov 17, 2012 at 06:16:11PM +0300, Dan Carpenter wrote:
> > This is a static checker fix.  The problem is that we store the bits
> > from "uv_apicid_hibits" into "apicid" (the high 16 bits) but then we
> > shift it 16 bit to the left.  "apicid" is an int so it wraps and we lose
> > them.
> 
> Is this the complete patch?  phys_apicid is an int, but gets
> cast as unsigned long.  Doesn't phys_apicid also have to be
> changed to unsigned long?  And why ulong instead of uint (on x86_64)?

Uint is 32bit across all arches in linux and unix, according to
wikipedia.  The wakeup_secondary_cpu() function pointer takes an int
so I couldn't change the parameter.

> 
> I agree with changing signed to unsigned where appropriate, but
> this looks like a partial fix.  Am I missing something?
> 

I do feel a little embarrassed that I didn't use "unsigned long"
consistently.  I just used ulong to make the line a bit shorter, but
I could redo it with "unsigned long" if you want.

regards,
dan carpenter


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