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From: Ingo Molnar <mingo@elte.hu>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Andi Kleen <ak@suse.de>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: preempt bug in set_pmd_pfn?
Date: Wed, 5 Mar 2008 07:48:14 +0100	[thread overview]
Message-ID: <20080305064814.GB28398@elte.hu> (raw)
In-Reply-To: <47CDBEDC.1050302@goop.org>


* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> Ingo Molnar wrote:
>> * Jeremy Fitzhardinge <jeremy@goop.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?

no, it's not OK to modify the kernel pagetable without locking - taking 
the pgd_lock should do the trick. Could you send the stacktrace that 
shows the place that is preemptible?

	Ingo

  reply	other threads:[~2008-03-05  6:48 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-04 21:13 Jeremy Fitzhardinge
2008-03-04 21:28 ` Ingo Molnar
2008-03-04 21:27   ` Jeremy Fitzhardinge
2008-03-05  6:48     ` Ingo Molnar [this message]
2008-03-05 14:29       ` Hugh Dickins
2008-03-05 16:48         ` Jeremy Fitzhardinge
2008-03-05 17:38           ` Hugh Dickins
2008-03-05 19:18             ` Jeremy Fitzhardinge
2008-03-05 20:40               ` Hugh Dickins
2008-03-06 12:52               ` Ingo Molnar
2008-03-06 18:19                 ` Jeremy Fitzhardinge
2008-03-05 16:45       ` Jeremy Fitzhardinge
2008-03-05  0:06 ` Andi Kleen
2008-03-05  0:07   ` Jeremy Fitzhardinge
2008-03-05  0:16     ` Andi Kleen
2008-03-05  0:19       ` Jeremy Fitzhardinge
2008-03-05  1:28         ` Andi Kleen

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