[PATCH] sched/deadline: Fix BUG_ON condition for deboosted tasks

Juri Lelli
2022-07-13T07:50:52Z

Tasks the are being deboosted from SCHED_DEADLINE might enter
enqueue_task_dl() one last time and hit an erroneous BUG_ON condition:
since they are not boosted anymore, the if (is_dl_boosted()) branch is
not taken, but the else if (!dl_prio) is and inside this one we
BUG_ON(!is_dl_boosted), which is of course false (BUG_ON triggered)
otherwise we had entered the if branch above. Long story short, the
current condition doesn't make sense and always leads to triggering of a
BUG.

Fix this by only checking enqueue flags, properly: ENQUEUE_REPLENISH has
to be present, but additional flags are not a problem.

Fixes: 2279f540ea7d ("sched/deadline: Fix priority inheritance with multiple scheduling classes")
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
---
kernel/sched/deadline.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 5867e186c39a..0447d46f4718 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1703,7 +1703,7 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
* the throttle.
*/
p->dl.dl_throttled = 0;
- BUG_ON(!is_dl_boosted(&p->dl) || flags != ENQUEUE_REPLENISH);
+ BUG_ON(!(flags & ENQUEUE_REPLENISH));
return;
}

--
2.36.1