linux-kernel - Re: [PATCH 6/6] sched_ext: idle: Deprecate scx_bpf_select_cpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <Z-sQsqt6kKLqJfJf@slm.duckdns.org>
Date: Mon, 31 Mar 2025 12:01:22 -1000
From: Tejun Heo <tj@...nel.org>
To: Andrea Righi <arighi@...dia.com>
Cc: David Vernet <void@...ifault.com>, Changwoo Min <changwoo@...lia.com>,
	Joel Fernandes <joelagnelf@...dia.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] sched_ext: idle: Deprecate scx_bpf_select_cpu_dfl()

Hello,

On Fri, Mar 21, 2025 at 11:10:52PM +0100, Andrea Righi wrote:
> With the introduction of scx_bpf_select_cpu_and(), we can deprecate
> scx_bpf_select_cpu_dfl(), as it offers only a subset of features and
> it's also more consistent with other idle-related APIs (returning a
> negative value when no idle CPU is found).
> 
> Therefore, mark scx_bpf_select_cpu_dfl() as deprecated (printing a
> warning when it's used), update all the scheduler examples and
> kselftests to adopt the new API, and ensure backward (source and binary)
> compatibility by providing the necessary macros and hooks.
> 
> Support for scx_bpf_select_cpu_dfl() can be maintained until v6.17.

Do we need to deprecate it?

...
> @@ -43,10 +39,13 @@ s32 BPF_STRUCT_OPS(select_cpu_dfl_nodispatch_select_cpu, struct task_struct *p,
>  		return -ESRCH;
>  	}
>  
> -	cpu = scx_bpf_select_cpu_dfl(p, prev_cpu, wake_flags,
> -				     &tctx->force_local);
> +	cpu = scx_bpf_select_cpu_and(p, prev_cpu, wake_flags, p->cpus_ptr, 0);
> +	if (cpu >= 0) {
> +		tctx->force_local = true;
> +		return cpu;
> +	}
>  
> -	return cpu;
> +	return prev_cpu;
>  }

scx_bpf_select_cpu_dfl() is simpler for simple cases. I don't see a pressing
need to convert everybody to _and().

Thanks.

-- 
tejun