From: Rik van Riel <riel@redhat.com>
To: Nadav Amit <namit@vmware.com>, linux-mm@kvack.org
Cc: nadav.amit@gmail.com, mgorman@suse.de, luto@kernel.org,
Minchan Kim <minchan@kernel.org>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: Re: [PATCH v5 3/3] Revert "mm: numa: defer TLB flush for THP migration as long as possible"
Date: Tue, 01 Aug 2017 07:05:45 -0400 [thread overview]
Message-ID: <1501585545.4073.81.camel@redhat.com> (raw)
In-Reply-To: <20170731164325.235019-4-namit@vmware.com>
On Mon, 2017-07-31 at 09:43 -0700, Nadav Amit wrote:
> While deferring TLB flushes is a good practice, the reverted patch
> caused pending TLB flushes to be checked while the page-table lock is
> not taken. As a result, in architectures with weak memory model
> (PPC),
> Linux may miss a memory-barrier, miss the fact TLB flushes are
> pending,
> and cause (in theory) a memory corruption.
>
> Since the alternative of using smp_mb__after_unlock_lock() was
> considered a bit open-coded, and the performance impact is expected
> to
> be small, the previous patch is reverted.
>
> This reverts commit b0943d61b8fa420180f92f64ef67662b4f6cc493.
>
> Suggested-by: Mel Gorman <mgorman@suse.de>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> Cc: Andy Lutomirski <luto@kernel.org>
> Cc: Rik van Riel <riel@redhat.com>
> Signed-off-by: Nadav Amit <namit@vmware.com>
>
Acked-by: Rik van Riel <riel@redhat.com>
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prev parent reply other threads:[~2017-08-01 11:05 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-31 16:43 [PATCH v5 0/3] mm: fixes of tlb_flush_pending Nadav Amit
2017-07-31 16:43 ` [PATCH v5 1/3] mm: migrate: prevent racy access to tlb_flush_pending Nadav Amit
2017-07-31 16:43 ` Nadav Amit
2017-08-01 6:01 ` Minchan Kim
2017-07-31 16:43 ` [PATCH v5 2/3] mm: migrate: fix barriers around tlb_flush_pending Nadav Amit
2017-08-01 11:05 ` Rik van Riel
2017-07-31 16:43 ` [PATCH v5 3/3] Revert "mm: numa: defer TLB flush for THP migration as long as possible" Nadav Amit
2017-08-01 10:06 ` Mel Gorman
2017-08-01 11:05 ` Rik van Riel [this message]
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