linux-kernel - Re: [PATCH v4 1/3] sched_ext: Introduce scx_bpf_cpu_rq

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Message-ID: <aJp-2TPbNKO3k_lq@slm.duckdns.org>
Date: Mon, 11 Aug 2025 13:38:01 -1000
From: Tejun Heo <tj@...nel.org>
To: Christian Loehle <christian.loehle@....com>
Cc: arighi@...dia.com, void@...ifault.com, linux-kernel@...r.kernel.org,
	sched-ext@...ts.linux.dev, changwoo@...lia.com, hodgesd@...a.com,
	mingo@...hat.com, peterz@...radead.org, jake@...lion.co.uk
Subject: Re: [PATCH v4 1/3] sched_ext: Introduce scx_bpf_cpu_rq_locked()

Hello,

On Mon, Aug 11, 2025 at 10:21:48PM +0100, Christian Loehle wrote:
> +/**
> + * scx_bpf_cpu_rq_locked - Fetch the locked rq of a CPU
> + * @cpu: CPU of the rq
> + */
> +__bpf_kfunc struct rq *scx_bpf_cpu_rq_locked(s32 cpu)
> +{
> +	struct rq *rq;
> +
> +	if (!kf_cpu_valid(cpu, NULL))
> +		return NULL;
> +
> +	preempt_disable();
> +	rq = cpu_rq(cpu);
> +	if (rq != scx_locked_rq()) {
> +		scx_kf_error("Accessing not locked rq %d", cpu);
> +		rq = NULL;
> +	}
> +	preempt_enable();
> +	return rq;
> +}

Do we need @cpu? What do you think about making the function not take any
arguments and just return the locked rq?

Thanks.

-- 
tejun