linux-kernel - Re: [PATCH 14/15] mm: fix TLB flush race between migration, and change_protection

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Message-ID: <52A29278.9000609@redhat.com>
Date:	Fri, 06 Dec 2013 22:14:00 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Christoph Lameter <cl@...ux.com>
CC:	Mel Gorman <mgorman@...e.de>, Alex Thorlton <athorlton@....com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 14/15] mm: fix TLB flush race between migration, and change_protection_range

On 12/06/2013 07:25 PM, Christoph Lameter wrote:
> On Fri, 6 Dec 2013, Rik van Riel wrote:
> 
>>> When you start migrating a page a special page migration entry is
>>> created that will trap all accesses to the page. You can safely flush when
>>> the migration entry is there. Only allow a new PTE/PMD to be put there
>>> *after* the tlb flush.
>>
>> A PROT_NONE or NUMA pte is just as effective as a migration pte.
>> The only problem is, the TLB flush was not always done...
> 
> Ok then what are you trying to fix?

It would help if you had actually read the patch.


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