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

[Xunlei Pang]

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

Regards,
Xunlei

> Regards,
> Wanpeng Li