Re: [PATCH sched_ext/for-7.3-fixes] sched_ext: Unlink pending local reenqueues before freeing scheduler

[Cheng-Yang Chou]

Hi Andrea,

On Wed, Sep 16, 2026 at 04:58:07PM +0200, Andrea Righi wrote:
[...]

> @@ -5380,13 +5380,20 @@ static void scx_sched_free_rcu_work(struct work_struct *work)
>  
>  	for_each_possible_cpu(cpu) {
>  		struct scx_sched_pcpu *pcpu = per_cpu_ptr(sch->pcpu, cpu);
> +		struct rq *rq = cpu_rq(cpu);
>  
>  		/*
> -		 * $sch would have entered bypass mode before the RCU grace
> -		 * period. As that blocks new deferrals, all
> -		 * deferred_reenq_local_node's must be off-list by now.
> +		 * Bypass blocks new deferrals, but a request queued before bypass
> +		 * may still be pending. As run_deferred() runs under the rq lock,
> +		 * take it to wait for any in-flight processing before unlinking the
> +		 * now-obsolete request.
>  		 */
> -		WARN_ON_ONCE(!list_empty(&pcpu->deferred_reenq_local.node));
> +		scoped_guard (rq_lock_irqsave, rq) {
> +			guard(raw_spinlock)(&rq->scx.deferred_reenq_lock);
> +
> +			if (!list_empty(&pcpu->deferred_reenq_local.node))
> +				list_del_init(&pcpu->deferred_reenq_local.node);
> +		}
>  
>  		/* remove the queued ecaps sync so the pcpu can be freed */
>  		scx_discard_ecaps_to_sync(cpu, pcpu);
> @@ -5395,7 +5402,7 @@ static void scx_sched_free_rcu_work(struct work_struct *work)
>  		 * Bypass blocks new kicks. Flush the kick irq_work so this
>  		 * pcpu's to_kick_node is off the list before it is freed.
>  		 */
> -		irq_work_sync(&cpu_rq(cpu)->scx.kick_cpus_irq_work);
> +		irq_work_sync(&rq->scx.kick_cpus_irq_work);
>  		WARN_ON_ONCE(!list_empty(&pcpu->to_kick_node));
>  		free_cpumask_var(pcpu->cpus_to_kick);
>  		free_cpumask_var(pcpu->cpus_to_kick_if_idle);
> -- 
> 2.55.0
> 

Though I couldn't reproduce the issue on my end, the fix lgtm. Thanks!

Acked-by: Cheng-Yang Chou <yphbchou0911@xxxxxxxxx>

-- 
Cheers,
Cheng-Yang