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Subject[PATCH] sched/deadline: fix switching to -deadline
Date
From: Luca Abeni <luca.abeni@santannapisa.it>

When switching to -deadline, if the scheduling deadline of a task is
in the past then switched_to_dl() calls setup_new_entity() to properly
initialize the scheduling deadline and runtime.

The problem is that the task is enqueued _before_ having its parameters
initialized by setup_new_entity(), and this can cause problems.
For example, a task with its out-of-date deadline in the past will
potentially be enqueued as the highest priority one; however, its
adjusted deadline may not be the earliest one.

This patch fixes the problem by initializing the task's parameters before
enqueuing it.

Signed-off-by: Luca Abeni <luca.abeni@santannapisa.it>
Reviewed-by: Daniel Bristot de Oliveira <bristot@redhat.com>
---
kernel/sched/deadline.c | 12 ++++--------
1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index a2ce590..ec53d24 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -950,6 +950,10 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se,
update_dl_entity(dl_se, pi_se);
else if (flags & ENQUEUE_REPLENISH)
replenish_dl_entity(dl_se, pi_se);
+ else if ((flags & ENQUEUE_RESTORE) &&
+ dl_time_before(dl_se->deadline,
+ rq_clock(rq_of_dl_rq(dl_rq_of_se(dl_se)))))
+ setup_new_dl_entity(dl_se);

__enqueue_dl_entity(dl_se);
}
@@ -1767,14 +1771,6 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
if (!task_on_rq_queued(p))
return;

- /*
- * If p is boosted we already updated its params in
- * rt_mutex_setprio()->enqueue_task(..., ENQUEUE_REPLENISH),
- * p's deadline being now already after rq_clock(rq).
- */
- if (dl_time_before(p->dl.deadline, rq_clock(rq)))
- setup_new_dl_entity(&p->dl);
-
if (rq->curr != p) {
#ifdef CONFIG_SMP
if (p->nr_cpus_allowed > 1 && rq->dl.overloaded)
--
2.7.4
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