linux-kernel - Re: [patch] x86, mm: avoid stale tlb entries by clearing prev mm

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Message-ID: <4D4A2D9C.2040803@zytor.com>
Date:	Wed, 02 Feb 2011 20:22:52 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Andi Kleen <andi@...stfloor.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"Mallick, Asit K" <asit.k.mallick@...el.com>
Subject: Re: [patch] x86, mm: avoid stale tlb entries by clearing prev mm_cpumask
 after switching mm

On 02/02/2011 08:12 PM, Linus Torvalds wrote:
> 
> So right now, we pretty much depend on "asm volatile" (a) not being
> re-ordered wrt other asm volatiles and (b) having that dependency on
> memory.
> 
> Iirc, the gcc people even agreed on this. Peter may remember details better..
> 

Yes, IIRC an "asm volatile" is assumed to be a universal consumer of
memory (it is only a universal producer if the "memory" clobber is
used), as well as being ordered with respect to other volatile operations.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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