linux-kernel - Re: 5.18 missing /proc/sys/kernel/sched_autogroup

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Date:   Mon, 30 May 2022 09:45:38 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Ivan Kozik <ivan@...ios.org>
Cc:     linux-kernel@...r.kernel.org, nizhen@...ontech.com,
        mingo@...nel.org
Subject: Re: 5.18 missing /proc/sys/kernel/sched_autogroup_enabled?

On Sun, May 29, 2022 at 11:52:42PM +0000, Ivan Kozik wrote:
> Hello,
> 
> I noticed that /proc/sys/kernel/sched_autogroup_enabled seems to have
> gone missing in 5.18. Am I doing something wrong, or is this a
> regression?
> 
> I also noticed that booting 5.18 with "noautogroup" results in a
> "kernel: failed when register_sysctl sched_autogroup_sysctls to
> kernel" message.  Because of the error and the missing
> /proc/sys/kernel/sched_autogroup_enabled, it is unclear whether
> autogroup is enabled or not.

*sigh*, I think this is yet another one of the sysctl move patches gone
bad :/ Specifically:

 c8eaf6ac76f4 ("sched: move autogroup sysctls into its own file")

Does something like the below help?

---

diff --git a/kernel/sched/autogroup.c b/kernel/sched/autogroup.c
index 16092b49ff6a..4ebaf97f7bd8 100644
--- a/kernel/sched/autogroup.c
+++ b/kernel/sched/autogroup.c
@@ -36,6 +36,7 @@ void __init autogroup_init(struct task_struct *init_task)
 	kref_init(&autogroup_default.kref);
 	init_rwsem(&autogroup_default.lock);
 	init_task->signal->autogroup = &autogroup_default;
+	sched_autogroup_sysctl_init();
 }
 
 void autogroup_free(struct task_group *tg)
@@ -219,7 +220,6 @@ void sched_autogroup_exit(struct signal_struct *sig)
 static int __init setup_autogroup(char *str)
 {
 	sysctl_sched_autogroup_enabled = 0;
-	sched_autogroup_sysctl_init();
 
 	return 1;
 }