linux-kernel - Re: [PATCH 14/31] sched_ext: Implement BPF extensible scheduler class

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Date:   Mon, 12 Dec 2022 13:31:11 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     torvalds@...ux-foundation.org, mingo@...hat.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        mgorman@...e.de, bristot@...hat.com, vschneid@...hat.com,
        ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        martin.lau@...nel.org, joshdon@...gle.com, brho@...gle.com,
        pjt@...gle.com, derkling@...gle.com, haoluo@...gle.com,
        dvernet@...a.com, dschatzberg@...a.com, dskarlat@...cmu.edu,
        riel@...riel.com, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, kernel-team@...a.com
Subject: Re: [PATCH 14/31] sched_ext: Implement BPF extensible scheduler class

On Tue, Nov 29, 2022 at 10:22:56PM -1000, Tejun Heo wrote:
> @@ -11242,3 +11268,38 @@ void call_trace_sched_update_nr_running(struct rq *rq, int count)
>  {
>          trace_sched_update_nr_running_tp(rq, count);
>  }
> +
> +#ifdef CONFIG_SCHED_CLASS_EXT
> +void sched_deq_and_put_task(struct task_struct *p, int queue_flags,
> +			    struct sched_enq_and_set_ctx *ctx)
> +{
> +	struct rq *rq = task_rq(p);
> +
> +	lockdep_assert_rq_held(rq);
> +
> +	*ctx = (struct sched_enq_and_set_ctx){
> +		.p = p,
> +		.queue_flags = queue_flags | DEQUEUE_NOCLOCK,
> +		.queued = task_on_rq_queued(p),
> +		.running = task_current(rq, p),
> +	};
> +
> +	update_rq_clock(rq);
> +	if (ctx->queued)
> +		dequeue_task(rq, p, queue_flags);
> +	if (ctx->running)
> +		put_prev_task(rq, p);
> +}
> +
> +void sched_enq_and_set_task(struct sched_enq_and_set_ctx *ctx)
> +{
> +	struct rq *rq = task_rq(ctx->p);
> +
> +	lockdep_assert_rq_held(rq);
> +
> +	if (ctx->queued)
> +		enqueue_task(rq, ctx->p, ctx->queue_flags);
> +	if (ctx->running)
> +		set_next_task(rq, ctx->p);
> +}
> +#endif	/* CONFIG_SCHED_CLASS_EXT */

So no. Like the whole __setscheduler_prio() thing, this doesn't make
sense outside of the core code, policy/class code should never need to
do this.

Also: https://lkml.kernel.org/r/20220330162228.GH14330@worktop.programming.kicks-ass.net