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Skip the warning when core scheduling > is enabled. > > v2: Reworded the description per Kuba Piecuch's review. No code change. > > Fixes: 7c65ae81ea86 ("sched_ext: Don't call put_prev_task_scx() before picking the next task") > Signed-off-by: Tejun Heo > --- > kernel/sched/ext/ext.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c > index 9c9cb9d08bca..503c4d2105ee 100644 > --- a/kernel/sched/ext/ext.c > +++ b/kernel/sched/ext/ext.c > @@ -3092,7 +3092,9 @@ static void put_prev_task_scx(struct rq *rq, struct task_struct *p, > * which should trigger an explicit follow-up scheduling event. > */ > if (next && sched_class_above(&ext_sched_class, next->sched_class)) { > - WARN_ON_ONCE(!(sch->ops.flags & SCX_OPS_ENQ_LAST)); > + /* core-sched can force cpu idle while @p is runnable */ > + if (!sched_core_enabled(rq)) > + WARN_ON_ONCE(!(sch->ops.flags & SCX_OPS_ENQ_LAST)); I was wondering if this could be a better check: WARN_ON_ONCE(sched_cpu_cookie_match(rq, p) && !(sch->ops.flags & SCX_OPS_ENQ_LAST)); With this: - the surrounding branch establishes that runnable p is being replaced by idle (class below sched_ext), - the core picker has already stored the selected cookie, - if p does not match that cookie, this CPU is being forced idle by core scheduling, - when core scheduling is disabled, sched_cpu_cookie_match() returns true, so we preserve the warning - when core scheduling is enabled and the cookies match the warning is also preserved. In theory it should work, unless I'm missing some other edge cases. Thanks, -Andrea > do_enqueue_task(rq, p, SCX_ENQ_LAST, -1); > } else { > do_enqueue_task(rq, p, 0, -1);