yield_task_dl() calls update_curr_dl() which calls start_dl_timer()
to throttle current task. But yield_task_dl() doesn't update the rq
clock which will cause start_dl_timer() to set the wrong dl_timer
which may be much later than current deadline time.
For instance, in systems with 100HZ tick, if there're few dl-tasks,
then rq clock will mainly depend on the tick to update its value.
If we choose the CONFIG_NO_HZ_FULL_ALL feature, things may get even
worse.
Moreover, there're some statistics in update_curr_dl() also relying
on rq clock, like rq_clock_task().
Thus, in yield_task_dl(), we should add update_rq_clock() before
update_curr_dl().
Signed-off-by: Xunlei Pang <pang.xun...@linaro.org>
---
kernel/sched/deadline.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index e5db8c6..5648e62 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -915,7 +915,11 @@ static void yield_task_dl(struct rq *rq)
rq->curr->dl.dl_yielded = 1;
p->dl.runtime = 0;
}
+
+ update_rq_clock(rq);
update_curr_dl(rq);
+ /* Will go to schedule(), to avoid another clock update. */
+ rq->skip_clock_update = 1;
}
#ifdef CONFIG_SMP
--
1.9.1
--
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