On Wed, 2016-06-08 at 11:05 +0800, Wanpeng Li wrote:
> 
> @@ -681,12 +681,17 @@ static cputime_t vtime_delta(struct task_struct
> *tsk)
>  static cputime_t get_vtime_delta(struct task_struct *tsk)
>  {
>       unsigned long now = READ_ONCE(jiffies);
> -     unsigned long delta = now - tsk->vtime_snap;
> +     cputime_t delta_time, steal_time;
>  
> +     steal_time =
> jiffies_to_cputime(steal_account_process_tick());
> +     delta_time = jiffies_to_cputime(now - tsk->vtime_snap);
>       WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE);
>       tsk->vtime_snap = now;
>  
> -     return jiffies_to_cputime(delta);
> +     if (steal_time < delta_time)
> +             delta_time -= steal_time;
> +
> +     return delta_time;
>  }

This isn't right.

If steal_time is equal to or larger than delta_time,
get_vtime_delta needs to return 0, not delta_time.

Otherwise the same time will be counted twice.

-- 
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