Merge tag 'sched_urgent_for_v6.17_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

torvalds · torvalds · commit fe3ad7a58b58 · 2025-08-31T09:13:00.000-07:00
Pull scheduler fixes from Borislav Petkov:

 - Fix a stall on the CPU offline path due to mis-counting a deadline
   server task twice as part of the runqueue's running tasks count

 - Fix a realtime tasks starvation case where failure to enqueue a timer
   whose expiration time is already in the past would cause repeated
   attempts to re-enqueue a deadline server task which leads to starving
   the former, realtime one

 - Prevent a delayed deadline server task stop from breaking the
   per-runqueue bandwidth tracking

 - Have a function checking whether the deadline server task has
   stopped, return the correct value

* tag 'sched_urgent_for_v6.17_rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/deadline: Don't count nr_running for dl_server proxy tasks
  sched/deadline: Fix RT task potential starvation when expiry time passed
  sched/deadline: Always stop dl-server before changing parameters
  sched/deadline: Fix dl_server_stopped()
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
@@ -1496,10 +1496,12 @@ static void update_curr_dl_se(struct rq *rq, struct sched_dl_entity *dl_se, s64
 		}
 
 		if (unlikely(is_dl_boosted(dl_se) || !start_dl_timer(dl_se))) {
-			if (dl_server(dl_se))
-				enqueue_dl_entity(dl_se, ENQUEUE_REPLENISH);
-			else
+			if (dl_server(dl_se)) {
+				replenish_dl_new_period(dl_se, rq);
+				start_dl_timer(dl_se);
+			} else {
 				enqueue_task_dl(rq, dl_task_of(dl_se), ENQUEUE_REPLENISH);
+			}
 		}
 
 		if (!is_leftmost(dl_se, &rq->dl))
@@ -1611,7 +1613,7 @@ void dl_server_stop(struct sched_dl_entity *dl_se)
 static bool dl_server_stopped(struct sched_dl_entity *dl_se)
 {
 	if (!dl_se->dl_server_active)
-		return false;
+		return true;
 
 	if (dl_se->dl_server_idle) {
 		dl_server_stop(dl_se);
@@ -1849,7 +1851,9 @@ void inc_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 	u64 deadline = dl_se->deadline;
 
 	dl_rq->dl_nr_running++;
-	add_nr_running(rq_of_dl_rq(dl_rq), 1);
+
+	if (!dl_server(dl_se))
+		add_nr_running(rq_of_dl_rq(dl_rq), 1);
 
 	inc_dl_deadline(dl_rq, deadline);
 }
@@ -1859,7 +1863,9 @@ void dec_dl_tasks(struct sched_dl_entity *dl_se, struct dl_rq *dl_rq)
 {
 	WARN_ON(!dl_rq->dl_nr_running);
 	dl_rq->dl_nr_running--;
-	sub_nr_running(rq_of_dl_rq(dl_rq), 1);
+
+	if (!dl_server(dl_se))
+		sub_nr_running(rq_of_dl_rq(dl_rq), 1);
 
 	dec_dl_deadline(dl_rq, dl_se->deadline);
 }
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
@@ -376,10 +376,8 @@ static ssize_t sched_fair_server_write(struct file *filp, const char __user *ubu
 			return  -EINVAL;
 		}
 
-		if (rq->cfs.h_nr_queued) {
-			update_rq_clock(rq);
-			dl_server_stop(&rq->fair_server);
-		}
+		update_rq_clock(rq);
+		dl_server_stop(&rq->fair_server);
 
 		retval = dl_server_apply_params(&rq->fair_server, runtime, period, 0);
 		if (retval)
