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From: Hugh Dickins <hugh@veritas.com>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Ingo Molnar <mingo@elte.hu>, "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 17:38:28 +0000 (GMT)	[thread overview]
Message-ID: <Pine.LNX.4.64.0803051721200.13410@blonde.site> (raw)
In-Reply-To: <47CECEE9.3000801@goop.org>

On Wed, 5 Mar 2008, Jeremy Fitzhardinge wrote:
> 
> If a thread goes from processor A -> B -> A, where A is first preempted
> between a pagetable update and a tlb flush, then the second time the thread
> runs on A may run with a stale tlb (if in the meantime A has either been idle
> or only running kernel threads).

Right, thanks, because __flush_tlb_one opts out of the full active_mm
checking which goes on for userspace mms (which covers, for example,
the case of preemption before dup_mmap's flush_tlb_mm).

But is there actually a case where there's a problem?  So far as I can see,
set_pmd_pfn is there solely for discontig_32's __init remap_numa_kva; and
set_pte_pfn is there solely for set_fixmap, which operates on a per-cpu
area of pagetable, which would already be in bigger trouble if preemption
to another cpu were possible.

Hugh

  reply	other threads:[~2008-03-05 17:39 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
2008-03-05 14:29       ` Hugh Dickins
2008-03-05 16:48         ` Jeremy Fitzhardinge
2008-03-05 17:38           ` Hugh Dickins [this message]
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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