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From: Tejun Heo <tj@kernel.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: David Vernet <void@manifault.com>,
	Changwoo Min <changwoo@igalia.com>,
	Emil Tsalapatis <emil@etsalapatis.com>,
	sched-ext@lists.linux.dev, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched_ext: Fix NULL pointer deref and warnings during scx teardown
Date: Mon, 2 Feb 2026 07:10:02 -1000	[thread overview]
Message-ID: <aYDaao9Xb_Bkv0NH@slm.duckdns.org> (raw)
In-Reply-To: <20260202151341.796959-1-arighi@nvidia.com>

Hello,

On Mon, Feb 02, 2026 at 04:13:41PM +0100, Andrea Righi wrote:
> @@ -2619,6 +2619,9 @@ static void set_cpus_allowed_scx(struct task_struct *p,
>  
>  	set_cpus_allowed_common(p, ac);
>  
> +	if (unlikely(!sch))
> +		return;
> +

I don't quite understand how this would happen. set_cpu_allowed_scx() is
called from do_set_cpus_allowed() with task_rq locked. ie. the task *has* to
be on sched_ext for it to be called. It's straightforward task rq lock
synchronization, so there's no race window.

Combined with the failures in switching_to_scx() and switched_form_scx(), I
wonder whether what's actually broken is more something like the disable
path missing some tasks?

Thanks.

-- 
tejun

  reply	other threads:[~2026-02-02 17:10 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-02-02 15:13 Andrea Righi
2026-02-02 17:10 ` Tejun Heo [this message]
2026-02-02 18:54   ` Andrea Righi
2026-02-02 20:52     ` Tejun Heo
2026-02-02 22:50       ` Andrea Righi
2026-02-03 14:01         ` Andrea Righi
2026-02-04 20:08           ` Tejun Heo

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