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Date:	Sun, 10 Nov 2013 20:42:01 +0100
From:	Michal Nazarewicz <>
To:	Ingo Molnar <>,
	Peter Zijlstra <>
Cc:, Michal Nazarewicz <>
Subject: [PATCH] sched: fair: avoid integer overflow

From: Michal Nazarewicz <>

sa->runnable_avg_sum is of type u32 but after shifting it by NICE_0_SHIFT
bits it is promoted to u64.  This of course makes no sense, since the
result will never be more then 32-bit long.  Casting sa->runnable_avg_sum
to u64 before it is shifted, fixes this problem.

Signed-off-by: Michal Nazarewicz <>
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index df77c60..50f1e170 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2153,7 +2153,7 @@ static inline void __update_tg_runnable_avg(struct sched_avg *sa,
 	long contrib;
 	/* The fraction of a cpu used by this cfs_rq */
-	contrib = div_u64(sa->runnable_avg_sum << NICE_0_SHIFT,
+	contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT,
 			  sa->runnable_avg_period + 1);
 	contrib -= cfs_rq->tg_runnable_contrib;

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