linux-kernel - [PATCH v2 3/3] sched/deadline: Cleanup on_dl

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Date:   Fri,  2 Aug 2019 15:59:45 +0100
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>
Cc:     Luca Abeni <luca.abeni@...tannapisa.it>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <valentin.schneider@....com>,
        Qais Yousef <qais.yousef@....com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/3] sched/deadline: Cleanup on_dl_rq() handling

Remove BUG_ON() in __enqueue_dl_entity() since there is already one in
enqueue_dl_entity().

Move the check that the dl_se is not on the dl_rq from
__dequeue_dl_entity() to dequeue_dl_entity() to align with the enqueue
side and use the on_dl_rq() helper function.

BUG_ON in dequeue_dl_entity() instead of silently return. Make this
possible by checking for !p->dl_throttled in dequeue_task_dl() before
calling __dequeue_task_dl(). update_curr_dl() will set
p->dl_throttled=1 in case it already calls __dequeue_task_dl().
The condition !p->dl_throttled && !on_dl_rq() is a BUG.

Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
---
 kernel/sched/deadline.c | 11 +++++------
 1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index c34e35e7ac23..2add54c8be8a 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1407,8 +1407,6 @@ static void __enqueue_dl_entity(struct sched_dl_entity *dl_se)
 	struct sched_dl_entity *entry;
 	int leftmost = 1;
 
-	BUG_ON(!RB_EMPTY_NODE(&dl_se->rb_node));
-
 	while (*link) {
 		parent = *link;
 		entry = rb_entry(parent, struct sched_dl_entity, rb_node);
@@ -1430,9 +1428,6 @@ static void __dequeue_dl_entity(struct sched_dl_entity *dl_se)
 {
 	struct dl_rq *dl_rq = dl_rq_of_se(dl_se);
 
-	if (RB_EMPTY_NODE(&dl_se->rb_node))
-		return;
-
 	rb_erase_cached(&dl_se->rb_node, &dl_rq->root);
 	RB_CLEAR_NODE(&dl_se->rb_node);
 
@@ -1466,6 +1461,8 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se,
 
 static void dequeue_dl_entity(struct sched_dl_entity *dl_se)
 {
+	BUG_ON(!on_dl_rq(dl_se));
+
 	__dequeue_dl_entity(dl_se);
 }
 
@@ -1544,7 +1541,9 @@ static void __dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 static void dequeue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 {
 	update_curr_dl(rq);
-	__dequeue_task_dl(rq, p, flags);
+
+	if (!p->dl.dl_throttled)
+		__dequeue_task_dl(rq, p, flags);
 
 	if (p->on_rq == TASK_ON_RQ_MIGRATING || flags & DEQUEUE_SAVE) {
 		sub_running_bw(&p->dl, &rq->dl);
-- 
2.17.1