linux-kernel - [PATCH 2/3] sched_ext: Factor out reenq_local() from scx_bpf_reenqueue

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Message-ID: <20251025001849.1915635-3-tj@kernel.org>
Date: Fri, 24 Oct 2025 14:18:48 -1000
From: Tejun Heo <tj@...nel.org>
To: David Vernet <void@...ifault.com>,
	Andrea Righi <andrea.righi@...ux.dev>,
	Changwoo Min <changwoo@...lia.com>
Cc: linux-kernel@...r.kernel.org,
	sched-ext@...ts.linux.dev,
	Peter Zijlstra <peterz@...radead.org>,
	Wen-Fang Liu <liuwenfang@...or.com>,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 2/3] sched_ext: Factor out reenq_local() from scx_bpf_reenqueue_local()

Factor out the core re-enqueue logic from scx_bpf_reenqueue_local() into a
new reenq_local() helper function. scx_bpf_reenqueue_local() now handles the
BPF kfunc checks and calls reenq_local() to perform the actual work.

This is a prep patch to allow reenq_local() to be called from other contexts.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/ext.c | 50 +++++++++++++++++++++++++++++---------------------
 1 file changed, 29 insertions(+), 21 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 111111111111..222222222222 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -5881,32 +5881,12 @@ static const struct btf_kfunc_id_set scx_kfunc_set_dispatch = {
 	.set			= &scx_kfunc_ids_dispatch,
 };

-__bpf_kfunc_start_defs();
-
-/**
- * scx_bpf_reenqueue_local - Re-enqueue tasks on a local DSQ
- *
- * Iterate over all of the tasks currently enqueued on the local DSQ of the
- * caller's CPU, and re-enqueue them in the BPF scheduler. Returns the number of
- * processed tasks. Can only be called from ops.cpu_release().
- */
-__bpf_kfunc u32 scx_bpf_reenqueue_local(void)
+static u32 reenq_local(struct rq *rq)
 {
-	struct scx_sched *sch;
 	LIST_HEAD(tasks);
 	u32 nr_enqueued = 0;
-	struct rq *rq;
 	struct task_struct *p, *n;

-	guard(rcu)();
-	sch = rcu_dereference(scx_root);
-	if (unlikely(!sch))
-		return 0;
-
-	if (!scx_kf_allowed(sch, SCX_KF_CPU_RELEASE))
-		return 0;
-
-	rq = cpu_rq(smp_processor_id());
 	lockdep_assert_rq_held(rq);

 	/*
@@ -5943,6 +5923,34 @@ __bpf_kfunc u32 scx_bpf_reenqueue_local(void)
 	return nr_enqueued;
 }

+__bpf_kfunc_start_defs();
+
+/**
+ * scx_bpf_reenqueue_local - Re-enqueue tasks on a local DSQ
+ *
+ * Iterate over all of the tasks currently enqueued on the local DSQ of the
+ * caller's CPU, and re-enqueue them in the BPF scheduler. Returns the number of
+ * processed tasks. Can only be called from ops.cpu_release().
+ */
+__bpf_kfunc u32 scx_bpf_reenqueue_local(void)
+{
+	struct scx_sched *sch;
+	struct rq *rq;
+
+	guard(rcu)();
+	sch = rcu_dereference(scx_root);
+	if (unlikely(!sch))
+		return 0;
+
+	if (!scx_kf_allowed(sch, SCX_KF_CPU_RELEASE))
+		return 0;
+
+	rq = cpu_rq(smp_processor_id());
+	lockdep_assert_rq_held(rq);
+
+	return reenq_local(rq);
+}
+
 __bpf_kfunc_end_defs();

 BTF_KFUNCS_START(scx_kfunc_ids_cpu_release)
--
2.47.1