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

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Message-ID: <aLi13oYFKMOe1GuD@gpd4>
Date: Wed, 3 Sep 2025 23:40:46 +0200
From: Andrea Righi <arighi@...dia.com>
To: Tejun Heo <tj@...nel.org>
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

On Wed, Sep 03, 2025 at 09:44:32AM -1000, Tejun Heo wrote:
> 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?

Makes sense, I'll adjust this in the next version.

Actually, this patch doesn't necessarily need to be part of this series,
I'll probably submit it separately.

Thanks,
-Andrea