Messages in this thread | | | From | bsegall@google ... | Subject | Re: [PATCH] sched: fair: avoid integer overflow | Date | Mon, 11 Nov 2013 11:46:59 -0800 |
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Michal Nazarewicz <mpn@google.com> writes:
> From: Michal Nazarewicz <mina86@mina86.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@mina86.com> Reviewed-by: Ben Segall <bsegall@google.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;
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