linux-kernel - [PATCH] mm: numa: Guarantee that tlb_flush_pending updates are visible before page table updates

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Message-ID: <20131211132109.GB24125@suse.de>
Date:	Wed, 11 Dec 2013 13:21:09 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Alex Thorlton <athorlton@....com>,
	Rik van Riel <riel@...hat.com>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] 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.

Cc: stable@...r.kernel.org
Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 include/linux/mm_types.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index c122bb1..a12f2ab 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -482,7 +482,12 @@ static inline bool 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)
--
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