[PATCH 6.12 506/567] sched_ext: Factor out local_dsq_post_enq() from dispatch_enqueue()

Greg Kroah-Hartman
2026-01-06T17:42:13Z

From: Tejun Heo <tj@kernel.org>

[ Upstream commit 530b6637c79e728d58f1d9b66bd4acf4b735b86d ]

Factor out local_dsq_post_enq() which performs post-enqueue handling for
local DSQs - triggering resched_curr() if SCX_ENQ_PREEMPT is specified or if
the current CPU is idle. No functional change.

This will be used by the next patch to fix move_local_task_to_local_dsq().

Cc: stable@vger.kernel.org # v6.12+
Reviewed-by: Andrea Righi <arighi@nvidia.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/sched/ext.c | 34 +++++++++++++++++++---------------
1 file changed, 19 insertions(+), 15 deletions(-)

--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -1676,6 +1676,22 @@ static void dsq_mod_nr(struct scx_dispat
WRITE_ONCE(dsq->nr, dsq->nr + delta);
}

+static void local_dsq_post_enq(struct scx_dispatch_q *dsq, struct task_struct *p,
+ u64 enq_flags)
+{
+ struct rq *rq = container_of(dsq, struct rq, scx.local_dsq);
+ bool preempt = false;
+
+ if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr &&
+ rq->curr->sched_class == &ext_sched_class) {
+ rq->curr->scx.slice = 0;
+ preempt = true;
+ }
+
+ if (preempt || sched_class_above(&ext_sched_class, rq->curr->sched_class))
+ resched_curr(rq);
+}
+
static void dispatch_enqueue(struct scx_dispatch_q *dsq, struct task_struct *p,
u64 enq_flags)
{
@@ -1773,22 +1789,10 @@ static void dispatch_enqueue(struct scx_
if (enq_flags & SCX_ENQ_CLEAR_OPSS)
atomic_long_set_release(&p->scx.ops_state, SCX_OPSS_NONE);

- if (is_local) {
- struct rq *rq = container_of(dsq, struct rq, scx.local_dsq);
- bool preempt = false;
-
- if ((enq_flags & SCX_ENQ_PREEMPT) && p != rq->curr &&
- rq->curr->sched_class == &ext_sched_class) {
- rq->curr->scx.slice = 0;
- preempt = true;
- }
-
- if (preempt || sched_class_above(&ext_sched_class,
- rq->curr->sched_class))
- resched_curr(rq);
- } else {
+ if (is_local)
+ local_dsq_post_enq(dsq, p, enq_flags);
+ else
raw_spin_unlock(&dsq->lock);
- }
}

static void task_unlink_from_dsq(struct task_struct *p,