The following commit has been merged into the sched/urgent branch of tip:
Commit-ID: 17e3e88ed0b6318fde0d1c14df1a804711cab1b5
Gitweb: https://git.kernel.org/tip/17e3e88ed0b6318fde0d1c14df1a804711cab1b5
Author: Vincent Guittot <vincent.guittot@linaro.org>
AuthorDate: Wed, 08 Oct 2025 15:12:14 +02:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 14 Oct 2025 13:43:08 +02:00
sched/fair: Fix pelt lost idle time detection
The check for some lost idle pelt time should be always done when
pick_next_task_fair() fails to pick a task and not only when we call it
from the fair fast-path.
The case happens when the last running task on rq is a RT or DL task. When
the latter goes to sleep and the /Sum of util_sum of the rq is at the max
value, we don't account the lost of idle time whereas we should.
Fixes: 67692435c411 ("sched: Rework pick_next_task() slow-path")
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/sched/fair.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index bc0b7ce..cee1793 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8920,21 +8920,21 @@ simple:
return p;
idle:
- if (!rf)
- return NULL;
-
- new_tasks = sched_balance_newidle(rq, rf);
+ if (rf) {
+ new_tasks = sched_balance_newidle(rq, rf);
- /*
- * Because sched_balance_newidle() releases (and re-acquires) rq->lock, it is
- * possible for any higher priority task to appear. In that case we
- * must re-start the pick_next_entity() loop.
- */
- if (new_tasks < 0)
- return RETRY_TASK;
+ /*
+ * Because sched_balance_newidle() releases (and re-acquires)
+ * rq->lock, it is possible for any higher priority task to
+ * appear. In that case we must re-start the pick_next_entity()
+ * loop.
+ */
+ if (new_tasks < 0)
+ return RETRY_TASK;
- if (new_tasks > 0)
- goto again;
+ if (new_tasks > 0)
+ goto again;
+ }
/*
* rq is about to be idle, check if we need to update the