From: Christoph Lameter <cl@linux.com>
To: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>, Alex Thorlton <athorlton@sgi.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 14/15] mm: fix TLB flush race between migration, and change_protection_range
Date: Fri, 6 Dec 2013 20:32:56 +0000 [thread overview]
Message-ID: <00000142c99cf5b0-69cc9987-aa36-4889-af6a-1a45032d0d13-000000@email.amazonses.com> (raw)
In-Reply-To: <20131206141331.10880d2b@annuminas.surriel.com>
On Fri, 6 Dec 2013, Rik van Riel wrote:
>
> The basic race looks like this:
>
> CPU A CPU B CPU C
>
> load TLB entry
> make entry PTE/PMD_NUMA
> fault on entry
> read/write old page
> start migrating page
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.
> change PTE/PMD to new page
Dont do that. We have migration entries for a reason.
> read/write old page [*]
Should cause a page fault which should put the process to sleep. Process
will safely read the page after the migration entry is removed.
> flush TLB
Establish the new PTE/PMD after the flush removing the migration pte
entry and thereby avoiding the race.
> reload TLB from new entry
> read/write new page
> lose data
>
> [*] the old page may belong to a new user at this point!
>
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next prev parent reply other threads:[~2013-12-06 20:33 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-03 8:51 [PATCH 00/14] NUMA balancing segmentation faults candidate fix on large machines Mel Gorman
2013-12-03 8:51 ` [PATCH 01/15] mm: numa: Do not batch handle PMD pages Mel Gorman
2013-12-03 8:51 ` [PATCH 02/15] mm: hugetlbfs: fix hugetlbfs optimization Mel Gorman
2013-12-03 8:51 ` [PATCH 03/15] mm: thp: give transparent hugepage code a separate copy_page Mel Gorman
2013-12-04 16:59 ` Alex Thorlton
2013-12-05 13:35 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 04/15] mm: numa: Serialise parallel get_user_page against THP migration Mel Gorman
2013-12-03 23:07 ` Rik van Riel
2013-12-03 23:54 ` Mel Gorman
2013-12-03 8:51 ` [PATCH 05/15] mm: numa: Call MMU notifiers on " Mel Gorman
2013-12-03 8:51 ` [PATCH 06/15] mm: Clear pmd_numa before invalidating Mel Gorman
2013-12-03 8:51 ` [PATCH 07/15] mm: numa: Do not clear PMD during PTE update scan Mel Gorman
2013-12-03 8:51 ` [PATCH 08/15] mm: numa: Do not clear PTE for pte_numa update Mel Gorman
2013-12-03 8:51 ` [PATCH 09/15] mm: numa: Ensure anon_vma is locked to prevent parallel THP splits Mel Gorman
2013-12-03 8:51 ` [PATCH 10/15] mm: numa: Avoid unnecessary work on the failure path Mel Gorman
2013-12-03 8:51 ` [PATCH 11/15] sched: numa: Skip inaccessible VMAs Mel Gorman
2013-12-03 8:51 ` [PATCH 12/15] Clear numa on mprotect Mel Gorman
2013-12-03 8:52 ` [PATCH 13/15] mm: numa: Avoid unnecessary disruption of NUMA hinting during migration Mel Gorman
2013-12-03 8:52 ` [PATCH 14/15] mm: numa: Flush TLB if NUMA hinting faults race with PTE scan update Mel Gorman
2013-12-03 23:07 ` Rik van Riel
2013-12-03 23:46 ` Mel Gorman
2013-12-04 14:33 ` Rik van Riel
2013-12-04 16:07 ` Mel Gorman
2013-12-05 15:40 ` Rik van Riel
2013-12-05 19:54 ` Mel Gorman
2013-12-05 20:05 ` Rik van Riel
2013-12-06 9:24 ` Mel Gorman
2013-12-06 17:38 ` Alex Thorlton
2013-12-06 18:32 ` Mel Gorman
2013-12-06 19:13 ` [PATCH 14/15] mm: fix TLB flush race between migration, and change_protection_range Rik van Riel
2013-12-06 20:32 ` Christoph Lameter [this message]
2013-12-06 21:21 ` Rik van Riel
2013-12-07 0:25 ` Christoph Lameter
2013-12-07 3:14 ` Rik van Riel
2013-12-09 16:00 ` Christoph Lameter
2013-12-09 16:27 ` Mel Gorman
2013-12-09 16:59 ` Christoph Lameter
2013-12-09 21:01 ` Rik van Riel
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