linux-kernel - Re: [PATCH v2] drm/sched: Replace use of system_wq with system_percpu

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: <CAAofZF7L4-0v0qpw3TSXp8ccYTf-+k6gJOOYsnCJptRicvDsMg@mail.gmail.com>
Date: Thu, 6 Nov 2025 16:54:44 +0100
From: Marco Crivellari <marco.crivellari@...e.com>
To: phasta@...nel.org
Cc: linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org, 
	Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>, 
	Frederic Weisbecker <frederic@...nel.org>, Sebastian Andrzej Siewior <bigeasy@...utronix.de>, 
	Michal Hocko <mhocko@...e.com>, Matthew Brost <matthew.brost@...el.com>, 
	Danilo Krummrich <dakr@...nel.org>, Christian Konig <ckoenig.leichtzumerken@...il.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>
Subject: Re: [PATCH v2] drm/sched: Replace use of system_wq with system_percpu_wq

On Thu, Nov 6, 2025 at 4:37 PM Philipp Stanner <phasta@...lbox.org> wrote:
>
> On Thu, 2025-11-06 at 16:01 +0100, Marco Crivellari wrote:
> > In the general workqueue implementation, if a user enqueues a work item
> > using schedule_delayed_work() the used wq is "system_wq" (per-cpu wq)
> > while queue_delayed_work() use WORK_CPU_UNBOUND (used when a cpu is not
> > specified). The same applies to schedule_work() that is using system_wq
> > and queue_work(), that makes use again of WORK_CPU_UNBOUND.
>
> Alright, just to be sure:
> Behavior doesn't change and system_percpu_wq is then still a workqueue
> where we can submit normal delayed_work?
>
> The scheduler's timeout mechanism relies on scheduling and canceling
> delayed work items.

Correct, system_percpu_wq is the replacement of system_wq. They are the same.
We chosen to add a new workqueue instead of rename system_wq, to make the
transition process smooth, but you can look at all of this as a rename
of system_wq
into system_percpu_wq, basically.

You can confirm by looking at the header file
"include/linux/workqueue.h", and search for
system_wq. There is only its definition, everything has been replaced
with system_percpu_wq.

> Thanks for the updated commit message, looks great.

Perfect! :-)

Thanks!

-- 

Marco Crivellari

L3 Support Engineer, Technology & Product