linux-kernel - Re: preempt bug in set_pmd

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Message-ID: <47CDBEDC.1050302@goop.org>
Date:	Tue, 04 Mar 2008 13:27:56 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <ak@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: preempt bug in set_pmd_pfn?

Ingo Molnar wrote:
> * Jeremy Fitzhardinge <jeremy@...p.org> wrote:
>
>   
>> I think set_pmd_pfn, which is only called by __set_fixmap, might have 
>> a preempt bug in it.
>>     
>
> yes, and we had similar preemption bugs in the past. I guess most places 
> are either infrequent or have some natural atomicity anyway. Wanna send 
> a patch?
>   

Sure.  Should it just disable preemption, or take a lock?  It calls 
set_pte_at without holding any pte locks; that seems to be relatively 
common.  Is it OK when you're operating on init_mm?

    J
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