From: Wanpeng Li <wanpeng...@hotmail.com>
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 <mi...@redhat.com>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Juri Lelli <juri.le...@arm.com>
Cc: Luca Abeni <luca.ab...@unitn.it>
Cc: Frederic Weisbecker <fweis...@gmail.com>
Signed-off-by: Wanpeng Li <wanpeng...@hotmail.com>
---
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
