The following commit has been merged into the sched/urgent branch of tip:

Commit-ID: ddfc710395cccc61247348df9eb18ea50321cbed Gitweb: https://git.kernel.org/tip/ddfc710395cccc61247348df9eb18ea50321cbed Author: Juri Lelli juri.lelli@redhat.com AuthorDate: Thu, 14 Jul 2022 17:19:08 +02:00 Committer: Peter Zijlstra peterz@infradead.org CommitterDate: Thu, 21 Jul 2022 10:35:28 +02:00

sched/deadline: Fix BUG_ON condition for deboosted tasks

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: 64be6f1f5f71 ("sched/deadline: Don't replenish from a !SCHED_DEADLINE entity") Signed-off-by: Juri Lelli juri.lelli@redhat.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Cc: stable@vger.kernel.org Link: https://lkml.kernel.org/r/20220714151908.533052-1-juri.lelli@redhat.com --- kernel/sched/deadline.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index b515296..7bf5612 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1701,7 +1701,10 @@ 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); + if (!(flags & ENQUEUE_REPLENISH)) + printk_deferred_once("sched: DL de-boosted task PID %d: REPLENISH flag missing\n", + task_pid_nr(p)); + return; }