linux-kernel - [PATCH sched_ext/for-6.12-fixes] sched_ext: scx_cgroup_exit() may be called without successful scx_cgroup

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Message-ID: <Zv2uXn0bP-YDCkc_@slm.duckdns.org>
Date: Wed, 2 Oct 2024 10:34:38 -1000
From: Tejun Heo <tj@...nel.org>
To: David Vernet <void@...ifault.com>
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.comm, sched-ext@...a.com
Subject: [PATCH sched_ext/for-6.12-fixes] sched_ext: scx_cgroup_exit() may be
 called without successful scx_cgroup_init()

568894edbe48 ("sched_ext: Add scx_cgroup_enabled to gate cgroup operations
and fix scx_tg_online()") assumed that scx_cgroup_exit() is only called
after scx_cgroup_init() finished successfully. This isn't true.
scx_cgroup_exit() can be called without scx_cgroup_init() being called at
all or after scx_cgroup_init() failed in the middle.

As init state is tracked per cgroup, scx_cgroup_exit() can be used safely to
clean up in all cases. Remove the incorrect WARN_ON_ONCE().

Signed-off-by: Tejun Heo <tj@...nel.org>
Fixes: 568894edbe48 ("sched_ext: Add scx_cgroup_enabled to gate cgroup operations and fix scx_tg_online()")
---
 kernel/sched/ext.c |    1 -
 1 file changed, 1 deletion(-)

--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -4119,7 +4119,6 @@ static void scx_cgroup_exit(void)

 	percpu_rwsem_assert_held(&scx_cgroup_rwsem);

-	WARN_ON_ONCE(!scx_cgroup_enabled);
 	scx_cgroup_enabled = false;

 	/*