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Date: Mon, 11 Nov 2013 11:46:59 -0800 From: bsegall@...gle.com To: Michal Nazarewicz <mpn@...gle.com> Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org, Michal Nazarewicz <mina86@...a86.com> Subject: Re: [PATCH] sched: fair: avoid integer overflow Michal Nazarewicz <mpn@...gle.com> writes: > From: Michal Nazarewicz <mina86@...a86.com> > > 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 <mina86@...a86.com> Reviewed-by: Ben Segall <bsegall@...gle.com> > --- > 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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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