1 files changed, 29 insertions, 5 deletions

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 3862a28cd05d..6d93f4518734 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1525,14 +1525,38 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
 	 */
 	if (pi_task && dl_prio(pi_task->normal_prio) && p->dl.dl_boosted) {
 		pi_se = &pi_task->dl;
+		/*
+		 * Because of delays in the detection of the overrun of a
+		 * thread's runtime, it might be the case that a thread
+		 * goes to sleep in a rt mutex with negative runtime. As
+		 * a consequence, the thread will be throttled.
+		 *
+		 * While waiting for the mutex, this thread can also be
+		 * boosted via PI, resulting in a thread that is throttled
+		 * and boosted at the same time.
+		 *
+		 * In this case, the boost overrides the throttle.
+		 */
+		if (p->dl.dl_throttled) {
+			/*
+			 * The replenish timer needs to be canceled. No
+			 * problem if it fires concurrently: boosted threads
+			 * are ignored in dl_task_timer().
+			 */
+			hrtimer_try_to_cancel(&p->dl.dl_timer);
+			p->dl.dl_throttled = 0;
+		}
 	} else if (!dl_prio(p->normal_prio)) {
 		/*
-		 * Special case in which we have a !SCHED_DEADLINE task
-		 * that is going to be deboosted, but exceeds its
-		 * runtime while doing so. No point in replenishing
-		 * it, as it's going to return back to its original
-		 * scheduling class after this.
+		 * Special case in which we have a !SCHED_DEADLINE task that is going
+		 * to be deboosted, but exceeds its runtime while doing so. No point in
+		 * replenishing it, as it's going to return back to its original
+		 * scheduling class after this. If it has been throttled, we need to
+		 * clear the flag, otherwise the task may wake up as throttled after
+		 * being boosted again with no means to replenish the runtime and clear
+		 * the throttle.
 		 */
+		p->dl.dl_throttled = 0;
 		BUG_ON(!p->dl.dl_boosted || flags != ENQUEUE_REPLENISH);
 		return;
 	}