[PATCH 3.12 114/144] mm: numa: guarantee that tlb_flush_pending updates are visible before page table updates

From: Greg Kroah-Hartman
Date: Mon Jan 06 2014 - 18:50:27 EST

3.12-stable review patch. If anyone has any objections, please let me know.


From: Mel Gorman <mgorman@xxxxxxx>

commit af2c1401e6f9177483be4fad876d0073669df9df upstream.

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

Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

include/linux/mm_types.h | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -478,7 +478,12 @@ static inline bool mm_tlb_flush_pending(
static inline void set_tlb_flush_pending(struct mm_struct *mm)
mm->tlb_flush_pending = true;
- barrier();
+ /*
+ * Guarantee that the tlb_flush_pending store does not leak into the
+ * critical section updating the page tables
+ */
+ smp_mb__before_spinlock();
/* Clearing is done after a TLB flush, which also provides a barrier. */
static inline void clear_tlb_flush_pending(struct mm_struct *mm)

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