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

Mel Gorman · torvalds · commit af2c1401e6f9 · 2013-12-18T19:04:51.000-08:00
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 &lt;mgorman@suse.de&gt;
Acked-by: Paul E. McKenney &lt;paulmck@linux.vnet.ibm.com&gt;
Reviewed-by: Rik van Riel &lt;riel@redhat.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
diff --git 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)

Original file line number	Diff line number	Diff line change
`@@ -482,7 +482,12 @@ static inline bool mm_tlb_flush_pending(struct mm_struct *mm)`
`482`	`482`	`static inline void set_tlb_flush_pending(struct mm_struct *mm)`
`483`	`483`	`{`
`484`	`484`	`mm->tlb_flush_pending = true;`
`485`		`- barrier();`
	`485`	`+`
	`486`	`+ /*`
	`487`	`+ * Guarantee that the tlb_flush_pending store does not leak into the`
	`488`	`+ * critical section updating the page tables`
	`489`	`+ */`
	`490`	`+ smp_mb__before_spinlock();`
`486`	`491`	`}`
`487`	`492`	`/* Clearing is done after a TLB flush, which also provides a barrier. */`
`488`	`493`	`static inline void clear_tlb_flush_pending(struct mm_struct *mm)`