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From: Kumar Gala <galak@kernel.crashing.org>
Subject: Re: Fix small race in 44x tlbie function
Date: Thu, 9 Aug 2007 00:28:20 -0500
To: Josh Boyer <jwboyer@linux.vnet.ibm.com>
Cc: linuxppc-dev@ozlabs.org, Volkmar Uhlig <vuhlig@us.ibm.com>,
	Paul Mackerras <paulus@samba.org>, Todd Inglett <tinglett@us.ibm.com>,
	David Gibson <david@gibson.dropbear.id.au>
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On Aug 8, 2007, at 11:00 AM, Josh Boyer wrote:

> On Wed, 8 Aug 2007 10:20:45 -0500
> Kumar Gala <galak@kernel.crashing.org> wrote:
>
>>
>> On Aug 6, 2007, at 11:20 PM, David Gibson wrote:
>>
>>> The 440 family of processors don't have a tlbie instruction.  So, we
>>> implement TLB invalidates by explicitly searching the TLB with  
>>> tlbsx.,
>>> then clobbering the relevant entry, if any.  Unfortunately the  
>>> PID for
>>> the search needs to be stored in the MMUCR register, which is also
>>> used by the TLB miss handler.  Interrupts were enabled in _tlbie 
>>> (), so
>>> an interrupt between loading the MMUCR and the tlbsx could cause
>>> incorrect search results, and thus a failure to invalide TLB entries
>>> which needed to be invalidated.
>>>
>>> This patch fixes the problem in both arch/ppc and arch/powerpc by
>>> inhibiting interrupts (even critical and debug interrupts) across  
>>> the
>>> relevant instructions.
>>>
>>> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
>>> ---
>>> Paul, this one's a bugfix, which I think should go into 2.6.23.
>>
>> Did you actually see this happen?
>
> Yes.

When?

We don't have critical wired to anything, I don't expect watchdog to  
cause another fault.. so just wondering.

- k