Messages in this thread | | | Date | Fri, 4 Mar 2011 14:05:52 +0530 | Subject | Re: [BUGFIX][PATCH] Fix sched rt group scheduling when hierachy is enabled | From | Balbir Singh <> |
| |
On Fri, Mar 4, 2011 at 2:02 PM, Yong Zhang <yong.zhang0@gmail.com> wrote: > 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. >
For parent of group_rq
> >> , 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*/
Note at some point rt_time becomes 0 and if enqueue is not set, the next do_sched_rt_period_timer() is a NOP and does not enqueue back the group
Balbir -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |