Re: [PATCH] sched/fair: do not announce throttled next buddy in dequeue_task_fair

[Xunlei Pang]

On 2016/07/11 at 16:22, Xunlei Pang wrote:
> On 2016/07/11 at 15:25, Wanpeng Li wrote:
>> 2016-06-16 20:57 GMT+08:00 Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx>:
>>> Hierarchy could be already throttled at this point. Throttled next
>>> buddy could trigger null pointer dereference in pick_next_task_fair().
>> There is cfs_rq->next check in pick_next_entity(), so how can null
>> pointer dereference happen?
> I guess it's the following code leading to a NULL se returned:

s/NULL/empty-entity cfs_rq se/

> pick_next_entity():
>     if (cfs_rq->next && wakeup_preempt_entity(cfs_rq->next, left) < 1)
>         se = cfs_rq->next;
>
> Regards,
> Xunlei
>
>> Regards,
>> Wanpeng Li