diff options
| author | Tejun Heo <tj@kernel.org> | 2026-06-29 12:55:48 -1000 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2026-06-30 04:08:18 -1000 |
| commit | b7d9c359e5cf867f7eb23df3bb1c6b9e58af24da (patch) | |
| tree | 56707ce20012f201df7df2b83fd9e205b145387a /kernel/sched | |
| parent | cb36d81e751173c4b59b5e561c596c925144ea48 (diff) | |
sched_ext: Don't warn on core-sched forced idle in put_prev_task_scx()
put_prev_task_scx() warns when a runnable task drops to a lower sched_class
without SCX_OPS_ENQ_LAST, on the assumption that balance_one() would have
kept it running. Core scheduling breaks that: a forced-idle SMT sibling
reschedules through the core_pick fast path in pick_next_task(), which skips
pick_task_scx() and thus balance_one(), so a runnable task can drop to idle
with ENQ_LAST unset.
Gate the warning on sched_cpu_cookie_match(): a cookie mismatch means core
scheduling forced the idle, while a match (or core scheduling off) still
catches a genuine missing-ENQ_LAST drop.
Fixes: 7c65ae81ea86 ("sched_ext: Don't call put_prev_task_scx() before picking the next task")
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/ext/ext.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c index 3b2e13bc924b..e75e2fd5ab7e 100644 --- a/kernel/sched/ext/ext.c +++ b/kernel/sched/ext/ext.c @@ -3090,9 +3090,14 @@ static void put_prev_task_scx(struct rq *rq, struct task_struct *p, * sched_class, %SCX_OPS_ENQ_LAST must be set. Tell * ops.enqueue() that @p is the only one available for this cpu, * which should trigger an explicit follow-up scheduling event. + * + * Core scheduling can force this CPU idle while @p stays + * runnable. @p's cookie then won't match the core's, so skip + * the warning in that case. */ if (next && sched_class_above(&ext_sched_class, next->sched_class)) { - WARN_ON_ONCE(!(sch->ops.flags & SCX_OPS_ENQ_LAST)); + WARN_ON_ONCE(sched_cpu_cookie_match(rq, p) && + !(sch->ops.flags & SCX_OPS_ENQ_LAST)); do_enqueue_task(rq, p, SCX_ENQ_LAST, -1); } else { do_enqueue_task(rq, p, 0, -1); |