Messages in this thread | | | Date | Fri, 4 Mar 2011 16:32:49 +0800 | Subject | Re: [BUGFIX][PATCH] Fix sched rt group scheduling when hierachy is enabled | From | Yong Zhang <> |
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On Fri, Mar 4, 2011 at 3:25 PM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > * Yong Zhang <yong.zhang0@gmail.com> [2011-03-04 11:43:16]: > >> On Thu, Mar 3, 2011 at 11:29 PM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote: >> > No, not really :) It is required, it is a backup check to see if we >> > have queued tasks, rt_time of 0 and the runqueue is not throttled, why >> > should it be dequeued? >> >> But I can't see where that kind of rt_rq is dequeued, mind pointing it out? >> > > So here is what I saw > > 1. sched_dequeue_stack called from the dequeue path dequeues the > queues and sets rt_nr_running to 0 > 2. Enqueuing fails because rt_throttled is set for the group_rq > (parent who is throttled) > 3. This causes further enqueue to fail, since rt_nr_running did > not increment in step 2
Whose rt_nr_running? group_rq's or parent of group_rq? For parent of group_rq, yes. For group_rq's, no, because we don't touch its rt_nr_running.
> , eventually the timer decrements rt_time > to 0 and the task is never picked up.
If I understand correctly, you mean this:
For a group(A) which has one task(b) attached but A is throttled,so A is unqueued now A.throttled == 1 && A.rt_nr_running == 1 deactivate_task(b); /* A.throttled == 1 && A.rt_nr_running == 0 */ do_sched_rt_period_timer(); /* A.run_time == 0 && A.throttled == 0*/ sched_rt_rq_enqueue(A); /* fails due to A.rt_nr_running == 0 */
But this doesn't prevent task readded to group A and eventually group A is added back.
Thanks, Yong
-- Only stand for myself
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