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

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Message-ID: <356a3c25-9c7c-41a5-a88e-ceeaf8405641@arm.com>
Date: Tue, 12 Aug 2025 10:07:46 +0100
From: Christian Loehle <christian.loehle@....com>
To: Tejun Heo <tj@...nel.org>
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()

On 8/12/25 00:38, Tejun Heo wrote:
> 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?

Indeed now that this no longer has to be a drop-in replacement.