linux-kernel - Re: [PATCH 2/2] sched/ext: Add BPF functions for uclamp inc and dec

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Message-ID: <ZoWVKQ7sD5uz66w5@slm.duckdns.org>
Date: Wed, 3 Jul 2024 08:15:05 -1000
From: Tejun Heo <tj@...nel.org>
To: Hongyan Xia <hongyan.xia2@....com>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] sched/ext: Add BPF functions for uclamp inc and dec

Hello.

On Wed, Jul 03, 2024 at 11:07:48AM +0100, Hongyan Xia wrote:
> +__bpf_kfunc void scx_bpf_uclamp_rq_inc(s32 cpu, struct task_struct *p)
> +{
> +	uclamp_rq_inc(cpu_rq(cpu), p);
> +}
> +
> +__bpf_kfunc void scx_bpf_uclamp_rq_dec(s32 cpu, struct task_struct *p)
> +{
> +	uclamp_rq_dec(cpu_rq(cpu), p);
> +}

So, I don't think we can expose these functions directly to the BPF
scheduler. The BPF schedulers shouldn't be able to break system integrity no
matter what they do and with the above it'd be trivial to get the bucket
counters unbalanced, right?

Thanks.

-- 
tejun