linux-kernel - [PATCH 22/46] sched_ext: Factor out scx_claim_exit() from scx

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Message-ID: <20250920005931.2753828-23-tj@kernel.org>
Date: Fri, 19 Sep 2025 14:58:45 -1000
From: Tejun Heo <tj@...nel.org>
To: void@...ifault.com,
	arighi@...dia.com,
	multics69@...il.com
Cc: linux-kernel@...r.kernel.org,
	sched-ext@...ts.linux.dev,
	memxor@...il.com,
	bpf@...r.kernel.org,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 22/46] sched_ext: Factor out scx_claim_exit() from scx_disable()

Both scx_disable() and scx_vexit() use cmpxchg on sch->exit_kind to claim
exit ownership but the latter lacks some sanity checks. Factor out
scx_claim_exit() from scx_disable() and use it in both places. This will
also be used to implement sub-sched disabling.

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/ext.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 54f65a196d94..b608c2c04730 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4086,15 +4086,20 @@ static void scx_disable_workfn(struct kthread_work *work)
 	scx_root_disable(sch);
 }
 
-static void scx_disable(struct scx_sched *sch, enum scx_exit_kind kind)
+static bool scx_claim_exit(struct scx_sched *sch, enum scx_exit_kind kind)
 {
 	int none = SCX_EXIT_NONE;
 
 	if (WARN_ON_ONCE(kind == SCX_EXIT_NONE || kind == SCX_EXIT_DONE))
 		kind = SCX_EXIT_ERROR;
 
-	atomic_try_cmpxchg(&sch->exit_kind, &none, kind);
-	kthread_queue_work(sch->helper, &sch->disable_work);
+	return atomic_try_cmpxchg(&sch->exit_kind, &none, kind);
+}
+
+static void scx_disable(struct scx_sched *sch, enum scx_exit_kind kind)
+{
+	if (scx_claim_exit(sch, kind))
+		kthread_queue_work(sch->helper, &sch->disable_work);
 }
 
 static void dump_newline(struct seq_buf *s)
@@ -4412,9 +4417,8 @@ static void scx_vexit(struct scx_sched *sch,
 		      const char *fmt, va_list args)
 {
 	struct scx_exit_info *ei = sch->exit_info;
-	int none = SCX_EXIT_NONE;
 
-	if (!atomic_try_cmpxchg(&sch->exit_kind, &none, kind))
+	if (!scx_claim_exit(sch, kind))
 		return;
 
 	ei->exit_code = exit_code;
-- 
2.51.0