[PATCH 2/4] sched/deadline: fix switching to -deadline

[luca abeni <luca.abeni@santannapisa.it>]

Fix a bug introduced in 72f9f3fdc928dc3ecd223e801b32d930b662b6ed:
after that commit, 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For example, a task with its out-of-date deadline in the past will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 | 11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index d05bd94..d7f9e86 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1376,6 +1376,10 @@ 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);
@@ -2267,13 +2271,6 @@ static void switched_to_dl(struct rq *rq, struct task_struct *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
-- 
2.7.4