Re: [PATCH 20/35] autonuma: avoid CFS select_task_rq_fair to return-1

[Peter Zijlstra]

On Fri, 2012-05-25 at 19:02 +0200, Andrea Arcangeli wrote:
> Fix to avoid -1 retval.
> 
> Includes fixes from Hillf Danton <dhillf@xxxxxxxxx>.

This changelog is very much insufficient. It fails to mention why your
solution is the right one or if there's something else wrong with that
code.

> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> ---
>  kernel/sched/fair.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 940e6d1..137119f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -2789,6 +2789,9 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
>  		if (new_cpu == -1 || new_cpu == cpu) {
>  			/* Now try balancing at a lower domain level of cpu */
>  			sd = sd->child;
> +			if (new_cpu < 0)
> +				/* Return prev_cpu is find_idlest_cpu failed */
> +				new_cpu = prev_cpu;
>  			continue;
>  		}
>  
> @@ -2807,6 +2810,7 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
>  unlock:
>  	rcu_read_unlock();
>  
> +	BUG_ON(new_cpu < 0);
>  	return new_cpu;
>  }
>  #endif /* CONFIG_SMP */

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