linux-kernel - Re: [PATCH 01/16] sched_ext: Exit early on hotplug events during attach

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Message-ID: <aLiaoEvjBfBsp-tR@slm.duckdns.org>
Date: Wed, 3 Sep 2025 09:44:32 -1000
From: Tejun Heo <tj@...nel.org>
To: Andrea Righi <arighi@...dia.com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	David Vernet <void@...ifault.com>,
	Changwoo Min <changwoo@...lia.com>, Shuah Khan <shuah@...nel.org>,
	sched-ext@...ts.linux.dev, bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/16] sched_ext: Exit early on hotplug events during
 attach

Hello,

On Wed, Sep 03, 2025 at 11:33:27AM +0200, Andrea Righi wrote:
>  static int validate_ops(struct scx_sched *sch, const struct sched_ext_ops *ops)
> @@ -5627,11 +5630,15 @@ static int scx_enable(struct sched_ext_ops *ops, struct bpf_link *link)
>  		if (((void (**)(void))ops)[i])
>  			set_bit(i, sch->has_op);
>  
> -	check_hotplug_seq(sch, ops);
> -	scx_idle_update_selcpu_topology(ops);
> +	ret = check_hotplug_seq(sch, ops);
> +	if (!ret)
> +		scx_idle_update_selcpu_topology(ops);
>  
>  	cpus_read_unlock();
>  
> +	if (ret)
> +		goto err_disable;

The double testing is a bit jarring. Maybe just add cpus_read_unlock() in
the error block so that error return can take place right after
check_hotplug_seq()? Alternatively, create a new error jump target - e.g.
err_disable_unlock_cpus and share it between here and the init failure path?

Thanks.

-- 
tejun