linux-kernel - Re: [PATCH 2/2] sched_ext/idle: Make scx_bpf_select_cpu

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Message-ID: <aCJTU1yuc61zdxVA@slm.duckdns.org>
Date: Mon, 12 May 2025 10:00:19 -1000
From: Tejun Heo <tj@...nel.org>
To: Andrea Righi <arighi@...dia.com>
Cc: David Vernet <void@...ifault.com>, Changwoo Min <changwoo@...lia.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] sched_ext/idle: Make scx_bpf_select_cpu_and() usable
 from any context

Hello,

On Mon, May 12, 2025 at 09:07:49PM +0200, Andrea Righi wrote:
...
> 	if (scx_kf_allowed_if_unlocked())
> 		rq = task_rq_lock(p, &rf);
> 	...
> 	if (scx_kf_allowed_if_unlocked())
> 		task_rq_unlock(rq, p, &rf);
> 
> Or at least it should cover all current use cases. The tricky one is
> scx_bpf_select_cpu_and() being called via BPF test_run from a user-space
> task (scx_rustland_core).
> 
> If we had a way to clearly identify a test_run context, we could restrict
> this to BPF_PROG_TYPE_STRUCT_OPS and BPF_PROG_TYPE_TEST_RUN (but as far as
> I can tell, the latter doesn't exist).

Shouldn't that work as-is? TEST_RUN isn't gonna set any kf_mask, so the same
condition would work?

Thanks.

-- 
tejun