mm: numa: guarantee that tlb_flush_pending updates are visible before page table updates

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.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index e5c49c30460f..ad0616f2fe2c 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -482,7 +482,12 @@ static inline bool mm_tlb_flush_pending(struct mm_struct *mm)
 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)