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SubjectRe: [PATCH v2 7/7] sched/rt: reschedule if stop/dl task slip in after pull operations

On 5/29/15 10:34 PM, Peter Zijlstra wrote:
> On Wed, May 13, 2015 at 02:01:07PM +0800, Wanpeng Li wrote:
>> pull_rt_task() can drop (and re-acquire) rq->lock, this means a dl
>> or stop task can slip in, in which case need to reschedule. This
>> patch add the reschedule when the scenario occurs.
>>
>> Signed-off-by: Wanpeng Li <wanpeng.li@linux.intel.com>
>> ---
>> kernel/sched/rt.c | 19 ++++++++++++++++++-
>> 1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
>> index 560d2fa..8c948bf 100644
>> --- a/kernel/sched/rt.c
>> +++ b/kernel/sched/rt.c
>> @@ -2136,7 +2136,14 @@ static void switched_from_rt(struct rq *rq, struct task_struct *p)
>> if (!task_on_rq_queued(p) || rq->rt.rt_nr_running)
>> return;
>>
>> - if (pull_rt_task(rq))
>> + /*
>> + * pull_rt_task() can drop (and re-acquire) rq->lock; this
>> + * means a dl or stop task can slip in, in which case we need
>> + * to reschedule.
>> + */
>> + if (pull_rt_task(rq) ||
>> + (unlikely((rq->stop && task_on_rq_queued(rq->stop)) ||
>> + rq->dl.dl_nr_running)))
>> resched_curr(rq);
>> }
> Same as before; why is the normal wakeup preemption check not working?

I will drop these two patches and send out v3. :)

Regards,
Wanpeng Li

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