linux-kernel - Re: [PATCHSET v2 sched_ext/for-6.16] sched_ext: Extend usability of 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] [day] [month] [year] [list]

Message-ID: <aCtyLLvETdgjxa5e@slm.duckdns.org>
Date: Mon, 19 May 2025 08:02:20 -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: [PATCHSET v2 sched_ext/for-6.16] sched_ext: Extend usability of
 scx_bpf_select_cpu_and()

On Thu, May 15, 2025 at 09:11:41PM +0200, Andrea Righi wrote:
> Many scx schedulers implement their own idle CPU selection policy, which
> may be invoked from different contexts, not just from ops.select_cpu().
> 
> For example, some schedulers may need to trigger a proactive CPU wakeup
> from ops.enqueue() after enqueuing a task, while others may expose this
> functionality to user space, relying on a BPF test_run call to pick an idle
> CPU.
> 
> To maintain a consistent selection policy, these schedulers often implement
> their own idle CPU selection logic, since the built-in one is only usable
> from ops.select_cpu(), leading to unnecessary code duplication and
> fragmentation.
> 
> To address this, allow scx_bpf_select_cpu_and() to be called not only from
> ops.select_cpu() and ops.enqueue(), but also from unlocked contexts (e.g.,
> when triggered from user space via a BPF test_run call).
> 
> This allows scx schedulers to consistently leverage the built-in idle CPU
> selection logic, helping reduce code duplication and fragmentation.
> 
> This patchset is also available in the following git branch:
> 
>  git://git.kernel.org/pub/scm/linux/kernel/git/arighi/linux.git scx-select-cpu-and
> 
> Changes in v2:
>  - Enable scx_bpf_select_cpu_and() to be called from ops.enqueue()
>    ops.select_cpu() and unlocked context
>  - Add locking validation to ensure safe access to p->cpus_ptr and
>    p->nr_cpus_allowed
>  - Extend selftest to cover scx_bpf_select_cpu_and() when invoked from user
>    space
>  - Link to v1: https://lore.kernel.org/all/20250512151743.42988-1-arighi@nvidia.com/
> 
> Andrea Righi (4):
>       sched_ext: Make scx_kf_allowed_if_unlocked() available outside ext.c
>       sched_ext: idle: Validate locking correctness in scx_bpf_select_cpu_and()
>       sched_ext: idle: Allow scx_bpf_select_cpu_and() from unlocked context
>       selftests/sched_ext: Add test for scx_bpf_select_cpu_and() via test_run

Applied to sched_ext/for-6.16.

Thanks.

-- 
tejun