From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Alex Thorlton <athorlton@sgi.com>, Rik van Riel <riel@redhat.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: numa: Guarantee that tlb_flush_pending updates are visible before page table updates
Date: Wed, 11 Dec 2013 08:56:20 -0800 [thread overview]
Message-ID: <20131211165620.GU4208@linux.vnet.ibm.com> (raw)
In-Reply-To: <20131211164052.GB11295@suse.de>
On Wed, Dec 11, 2013 at 04:40:52PM +0000, Mel Gorman wrote:
> On Wed, Dec 11, 2013 at 06:44:47AM -0800, Paul E. McKenney wrote:
> > On Wed, Dec 11, 2013 at 01:21:09PM +0000, Mel Gorman wrote:
> > > According to documentation on barriers, stores issued before a LOCK can
> > > complete after the lock implying that it's possible tlb_flush_pending can
> > > be visible after a page table update. As per revised documentation, this patch
> > > adds a smp_mb__before_spinlock to guarantee the correct ordering.
> > >
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Mel Gorman <mgorman@suse.de>
> >
> > Assuming that there is a lock acquisition after calls to
> > set_tlb_flush_pending():
> >
> > Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> >
> > (I don't see set_tlb_flush_pending() in mainline.)
> >
>
> It's introduced by a patch flight that is currently sitting in Andrew's
> tree. In the case where we care about the value of tlb_flush_pending, a
> spinlock will be taken. PMD or PTE split spinlocks or the mm->page_table_lock
> depending on whether it is 3.13 or 3.12-stable and earlier kernels. I
> pushed the relevant patches to this tree and branch
>
> git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux-balancenuma.git numab-instrument-serialise-v5r1
>
> There is no guarantee the lock will be taken if there are no pages populated
> in the region but we also do not care about flushing the TLB in that case
> either. Does it matter that there is no guarantee a lock will be taken
> after smp_mb__before_spinlock, just very likely that it will be?
If you do smp_mb__before_spinlock() without a lock acquisition, no harm
will be done, other than possibly a bit of performance loss. So you
should be OK.
Thanx, Paul
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next prev parent reply other threads:[~2013-12-11 16:56 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-10 15:51 [PATCH 00/17] NUMA balancing segmentation fault fixes and misc followups v4 Mel Gorman
2013-12-10 15:51 ` [PATCH 01/18] mm: numa: Serialise parallel get_user_page against THP migration Mel Gorman
2013-12-10 15:51 ` [PATCH 02/18] mm: numa: Call MMU notifiers on " Mel Gorman
2013-12-10 15:51 ` [PATCH 03/18] mm: Clear pmd_numa before invalidating Mel Gorman
2013-12-10 15:51 ` [PATCH 04/18] mm: numa: Do not clear PMD during PTE update scan Mel Gorman
2013-12-10 15:51 ` [PATCH 05/18] mm: numa: Do not clear PTE for pte_numa update Mel Gorman
2013-12-16 23:15 ` [PATCH 19/18] mm,numa: write pte_numa pte back to the page tables Rik van Riel
2013-12-10 15:51 ` [PATCH 06/18] mm: numa: Ensure anon_vma is locked to prevent parallel THP splits Mel Gorman
2013-12-10 15:51 ` [PATCH 07/18] mm: numa: Avoid unnecessary work on the failure path Mel Gorman
2013-12-10 15:51 ` [PATCH 08/18] sched: numa: Skip inaccessible VMAs Mel Gorman
2013-12-10 15:51 ` [PATCH 09/18] mm: numa: Clear numa hinting information on mprotect Mel Gorman
2013-12-10 15:51 ` [PATCH 10/18] mm: numa: Avoid unnecessary disruption of NUMA hinting during migration Mel Gorman
2013-12-17 22:53 ` Sasha Levin
2013-12-19 11:59 ` Mel Gorman
2013-12-19 12:00 ` [PATCH] mm: Remove bogus warning in copy_huge_pmd Mel Gorman
2013-12-19 18:36 ` Rik van Riel
2013-12-10 15:51 ` [PATCH 11/18] mm: fix TLB flush race between migration, and change_protection_range Mel Gorman
2013-12-11 19:12 ` [PATCH] mm: fix TLB flush race between migration, and change_protection_range -fix Mel Gorman
2013-12-10 15:51 ` [PATCH 12/18] mm: numa: Defer TLB flush for THP migration as long as possible Mel Gorman
2013-12-10 16:56 ` Rik van Riel
2013-12-10 15:51 ` [PATCH 13/18] mm: numa: Make NUMA-migrate related functions static Mel Gorman
2013-12-10 15:51 ` [PATCH 14/18] mm: numa: Limit scope of lock for NUMA migrate rate limiting Mel Gorman
2013-12-10 15:51 ` [PATCH 15/18] mm: numa: Trace tasks that fail migration due to " Mel Gorman
2013-12-10 15:51 ` [PATCH 16/18] mm: numa: Do not automatically migrate KSM pages Mel Gorman
2013-12-10 15:51 ` [PATCH 17/18] sched: Add tracepoints related to NUMA task migration Mel Gorman
2013-12-10 22:22 ` Andrew Morton
2013-12-11 8:37 ` Mel Gorman
2013-12-10 15:56 ` [PATCH 00/17] NUMA balancing segmentation fault fixes and misc followups v4 Mel Gorman
2013-12-11 13:21 ` [PATCH] mm: numa: Guarantee that tlb_flush_pending updates are visible before page table updates Mel Gorman
2013-12-11 14:44 ` Paul E. McKenney
2013-12-11 16:40 ` Mel Gorman
2013-12-11 16:56 ` Paul E. McKenney [this message]
2013-12-11 15:21 ` Rik van Riel
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