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Date: Wed, 8 Oct 2025 10:53:20 -1000
From: Tejun Heo <tj@kernel.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: Phil Auld <pauld@redhat.com>, David Vernet <void@manifault.com>,
	Changwoo Min <changwoo@igalia.com>, sched-ext@lists.linux.dev
Subject: Re: sched_ext and large cpu counts
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References: <20251007133523.GA93086@pauld.westford.csb>
 <d1c0eda5206b01fd670e148bd5ea0d56@kernel.org>
 <aOYAV2ZQvMt5aZxu@gpd4>
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In-Reply-To: <aOYAV2ZQvMt5aZxu@gpd4>

On Wed, Oct 08, 2025 at 08:10:31AM +0200, Andrea Righi wrote:
> > @@ -5082,7 +5126,7 @@ static void kick_cpus_irq_workfn(struct irq_work *irq_work)
> >  {
> >  	struct rq *this_rq = this_rq();
> >  	struct scx_rq *this_scx = &this_rq->scx;
> > -	unsigned long *pseqs = this_cpu_ptr(scx_kick_cpus_pnt_seqs);
> > +	unsigned long *pseqs = __this_cpu_read(scx_kick_cpus_pnt_seqs);
> >  	bool should_wait = false;
> >  	s32 cpu;
> 
> Should we add:
> 
> 	if (WARN_ON_ONCE(!pseqs))
> 		return;
> 
> Not sure if we can race with scx_disable_workfn() here.
> But for a test the patch looks fine as it is.

Oh yeah, I think it can. We should probably RCU free the arrays and add a
NULL check here.

Thanks.

-- 
tejun