linux-kernel - Re: [PATCH 2/4] sched_ext: Add scx_bpf_task_set_slice() and scx_bpf_task_set_dsq

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Message-ID: <aOVXuGBp7b2kotS9@slm.duckdns.org>
Date: Tue, 7 Oct 2025 08:11:04 -1000
From: Tejun Heo <tj@...nel.org>
To: Changwoo Min <changwoo@...lia.com>
Cc: David Vernet <void@...ifault.com>, Andrea Righi <arighi@...dia.com>,
	linux-kernel@...r.kernel.org, sched-ext@...ts.linux.dev
Subject: Re: [PATCH 2/4] sched_ext: Add scx_bpf_task_set_slice() and
 scx_bpf_task_set_dsq_vtime()

On Wed, Oct 08, 2025 at 01:28:31AM +0900, Changwoo Min wrote:
> 
> On 10/7/25 10:51, Tejun Heo wrote:
> > With the planned hierarchical scheduler support, sub-schedulers will need to
> > be verified for authority before being allowed to modify task->scx.slice and
> > task->scx.dsq_vtime. Add scx_bpf_task_set_slice() and
> > scx_bpf_task_set_dsq_vtime() which will perform the necessary permission
> > checks.
> 
> Is it necessary to distinguish between decreasing the slice and
> increasing the slice? A BPF scheduler (e.g., LAVD) sets the slice to
> zero for passive preemption.

It's going to be a simple "does this scheduler own this task?" test, I don't
think it needs to look at how the value is being changed.

Thanks.

-- 
tejun