Ping Juri, Frederic, could I get your Acked?
2016-08-12 17:24 GMT+08:00 Wanpeng Li <kernellwp@xxxxxxxxx>:
> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
>
> The dl task will be replenished after dl task timer fire and start a
> new period. It will be enqueued and to re-evaluate its dependency on
> the tick in order to restart it. However, if cpu is hot-unplug,
> irq_work_queue will splash since the target cpu is offline.
>
> As a result:
>
> WARNING: CPU: 2 PID: 0 at kernel/irq_work.c:69 irq_work_queue_on+0xad/0xe0
> Call Trace:
> dump_stack+0x99/0xd0
> __warn+0xd1/0xf0
> warn_slowpath_null+0x1d/0x20
> irq_work_queue_on+0xad/0xe0
> tick_nohz_full_kick_cpu+0x44/0x50
> tick_nohz_dep_set_cpu+0x74/0xb0
> enqueue_task_dl+0x226/0x480
> activate_task+0x5c/0xa0
> dl_task_timer+0x19b/0x2c0
> ? push_dl_task.part.31+0x190/0x190
>
> This can be triggered by hot-unplug the full dynticks cpu which dl
> task is running on.
>
> We enqueue the dl task on the offline CPU, because we need to do
> replenish for start_dl_timer(). So, as Juri pointed out, we would
> need to do is calling replenish_dl_entity() directly, instead of
> enqueue_task_dl(). pi_se shouldn't be a problem as the task shouldn't
> be boosted if it was throttled.
>
> This patch fix it by just replenish dl entity to avoid the intention
> to re-evaluate tick dependency if the cpu is offline.
>
> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: Juri Lelli <juri.lelli@xxxxxxx>
> Cc: Luca Abeni <luca.abeni@xxxxxxxx>
> Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
> Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
> ---
> v2 -> v3:
> * move rq->online check under CONFIG_SMP
> v1 -> v2:
> * replenish dl entity
>
> kernel/sched/deadline.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index d091f4a..ce0fb00 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -641,6 +641,11 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
> goto unlock;
> }
>
> +#ifdef CONFIG_SMP
> + if (unlikely(!rq->online))
> + goto offline;
> +#endif
> +
> enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
> if (dl_task(rq->curr))
> check_preempt_curr_dl(rq, p, 0);
> @@ -648,6 +653,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
> resched_curr(rq);
>
> #ifdef CONFIG_SMP
> +offline:
> /*
> * Perform balancing operations here; after the replenishments. We
> * cannot drop rq->lock before this, otherwise the assertion in
> @@ -659,6 +665,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
> * XXX figure out if select_task_rq_dl() deals with offline cpus.
> */
> if (unlikely(!rq->online)) {
> + replenish_dl_entity(dl_se, dl_se);
> lockdep_unpin_lock(&rq->lock, rf.cookie);
> rq = dl_task_offline_migration(rq, p);
> rf.cookie = lockdep_pin_lock(&rq->lock);
> --
> 1.9.1
>
--
Regards,
Wanpeng Li
--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
