linux-kernel - [PATCH 12/12] sched_ext: Clean up SCX_EXIT_NONE handling in scx_disable

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Message-ID: <20250423234542.1890867-13-tj@kernel.org>
Date: Wed, 23 Apr 2025 13:44:50 -1000
From: Tejun Heo <tj@...nel.org>
To: David Vernet <void@...ifault.com>,
	Andrea Righi <arighi@...dia.com>,
	Changwoo Min <changwoo@...lia.com>,
	linux-kernel@...r.kernel.org
Cc: Tejun Heo <tj@...nel.org>
Subject: [PATCH 12/12] sched_ext: Clean up SCX_EXIT_NONE handling in scx_disable_workfn()

With the global states and disable machinery moved into scx_sched,
scx_disable_workfn() can only be scheduled and run for the specific
scheduler instance. This makes it impossible for scx_disable_workfn() to see
SCX_EXIT_NONE. Turn that condition into WARN_ON_ONCE().

Signed-off-by: Tejun Heo <tj@...nel.org>
---
 kernel/sched/ext.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index d27193010b6a..d963aa5c99e1 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4749,13 +4749,9 @@ static void scx_disable_workfn(struct kthread_work *work)
 
 	kind = atomic_read(&sch->exit_kind);
 	while (true) {
-		/*
-		 * NONE indicates that a new scx_ops has been registered since
-		 * disable was scheduled - don't kill the new ops. DONE
-		 * indicates that the ops has already been disabled.
-		 */
-		if (kind == SCX_EXIT_NONE || kind == SCX_EXIT_DONE)
+		if (kind == SCX_EXIT_DONE)	/* already disabled? */
 			return;
+		WARN_ON_ONCE(kind == SCX_EXIT_NONE);
 		if (atomic_try_cmpxchg(&sch->exit_kind, &kind, SCX_EXIT_DONE))
 			break;
 	}
-- 
2.49.0