linux-kernel - Re: [PATCH 1/2] sched_ext: Fix ops.dequeue() semantics

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Message-ID: <aYvFP4T-TQHuez3X@slm.duckdns.org>
Date: Tue, 10 Feb 2026 13:54:39 -1000
From: Tejun Heo <tj@...nel.org>
To: Andrea Righi <arighi@...dia.com>
Cc: David Vernet <void@...ifault.com>, Changwoo Min <changwoo@...lia.com>,
	Kuba Piecuch <jpiecuch@...gle.com>,
	Emil Tsalapatis <emil@...alapatis.com>,
	Christian Loehle <christian.loehle@....com>,
	Daniel Hodges <hodgesd@...a.com>, sched-ext@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] sched_ext: Fix ops.dequeue() semantics

One more comment.

On Tue, Feb 10, 2026 at 10:26:04PM +0100, Andrea Righi wrote:
> @@ -1407,13 +1446,19 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
>  	 * dequeue may be waiting. The store_release matches their load_acquire.
>  	 */
>  	atomic_long_set_release(&p->scx.ops_state, SCX_OPSS_QUEUED | qseq);
> +
> +	/*
> +	 * Task is now in BPF scheduler's custody. Set %SCX_TASK_IN_CUSTODY
> +	 * so ops.dequeue() is called when it leaves custody.
> +	 */
> +	p->scx.flags |= SCX_TASK_IN_CUSTODY;

As this is protected by task's rq lock, doing it here is okay but can you
move this above atomic_long_set_release()? That's conceptually more
straightforward as that set_release() is supposed to be the "I'm done with
this task" point.

Thanks.

-- 
tejun