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Message-ID: <aLscu4p7hU8HJRkK@slm.duckdns.org>
Date: Fri, 5 Sep 2025 07:24:11 -1000
From: Tejun Heo <tj@...nel.org>
To: Marco Crivellari <marco.crivellari@...e.com>
Cc: linux-kernel@...r.kernel.org, Lai Jiangshan <jiangshanlai@...il.com>,
Frederic Weisbecker <frederic@...nel.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH 2/3] workqueue: replace use of system_wq with
system_percpu_wq
On Fri, Sep 05, 2025 at 11:13:24AM +0200, Marco Crivellari wrote:
> Currently if a user enqueue 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.
>
> This lack of consistentcy cannot be addressed without refactoring the API.
>
> system_wq is a per-CPU worqueue, yet nothing in its name tells about that
> CPU affinity constraint, which is very often not required by users. Make
> it clear by adding a system_percpu_wq.
>
> queue_work() / queue_delayed_work() mod_delayed_work() will now use the
> new per-cpu wq: whether the user still stick on the old name a warn will
> be printed along a wq redirect to the new one.
>
> This patch add the new system_percpu_wq except for mm, fs and net
> subsystem, whom are handled in separated patches.
>
> The old wq will be kept for a few release cylces.
>
> Suggested-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
Applied 1-2 to wq/for-6.18.
Thanks.
--
tejun
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