Re: [PATCH v5 2/3] mm: migrate: fix barriers around tlb_flush_pending

On Mon, 2017-07-31 at 09:43 -0700, Nadav Amit wrote:

Reading tlb_flush_pending while the page-table lock is taken does not
require a barrier, since the lock/unlock already acts as a barrier.
Removing the barrier in mm_tlb_flush_pending() to address this issue.

However, migrate_misplaced_transhuge_page() calls
mm_tlb_flush_pending()
while the page-table lock is already released, which may present a
problem on architectures with weak memory model (PPC). To deal with
this
case, a new parameter is added to mm_tlb_flush_pending() to indicate
if it is read without the page-table lock taken, and calling
smp_mb__after_unlock_lock() in this case.

Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <redacted>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <redacted>

Signed-off-by: Nadav Amit <redacted>

Acked-by: Rik van Riel <redacted>

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