答复: [PATCH] sched/cputime: Fix a mostly theoretical divide by zero

[Li,Rongqing]

> 
> Sum of utime and stime can overflow to 0, when a process with many threads
> run over total 2^64 ns
> 
> Signed-off-by: Li RongQing <lirongqing@xxxxxxxxx>


Ping

Thanks

-Li

> ---
>  kernel/sched/cputime.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c index
> 6dab4854..c35fc4c 100644
> --- a/kernel/sched/cputime.c
> +++ b/kernel/sched/cputime.c
> @@ -579,7 +579,8 @@ void cputime_adjust(struct task_cputime *curr, struct
> prev_cputime *prev,
>  		goto update;
>  	}
> 
> -	stime = mul_u64_u64_div_u64(stime, rtime, stime + utime);
> +	if (likely(stime + utime))
> +		stime = mul_u64_u64_div_u64(stime, rtime, stime + utime);
>  	/*
>  	 * Because mul_u64_u64_div_u64() can approximate on some
>  	 * achitectures; enforce the constraint that: a*b/(b+c) <= a.
> --
> 2.9.4