linux-kernel - Re: [PATCH] media: synopsys: hdmirx: replace use of system_unbound_wq with system_dfl

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Message-ID: <CAAofZF7k7LDxGoXENBtrpP-xokGoCJCqouGX-qumGTPwipAwVw@mail.gmail.com>
Date: Tue, 4 Nov 2025 17:44:14 +0100
From: Marco Crivellari <marco.crivellari@...e.com>
To: Dmitry Osipenko <dmitry.osipenko@...labora.com>
Cc: linux-kernel@...r.kernel.org, linux-media@...r.kernel.org, 
	kernel@...labora.com, 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>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>
Subject: Re: [PATCH] media: synopsys: hdmirx: replace use of system_unbound_wq
 with system_dfl_wq

Hi,

On Tue, Nov 4, 2025 at 1:46 PM Dmitry Osipenko
<dmitry.osipenko@...labora.com> wrote:
>
> Hi,
>[...]
> Took me a minute to find what "dfl" stands for. Would be great if the
> name was self-explanatory as system_default_wq. Even then, not clear to
> me what's the point of this remaining, the system_dfl_wq naming feels
> very obscure compared to the explicit system_unbound_wq.
>
> Could you please explain the logic behind the new naming? Doesn't it
> create more confusion than remove?

Yes, dfl it is just the abbreviation of default.

The reason is to suggest the use of the unbound workqueue
instead of the per-cpu, unless this is really needed, of course.

There are parts of the code who just used system_wq thinking it was the
unbound workqueue (the "general" wq to use), so to make explicit the
"default" is the unbound (system_dfl_wq) I think it is appropriate.

I saw this myself also in this conversion round: there are maintainers
who are asking
to change the wq they were using from system_wq to system_dfl_wq.

Let me share also where the API change (and other stuff) have been discussed:

https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/

On Tue, Nov 4, 2025 at 1:46 PM Dmitry Osipenko
<dmitry.osipenko@...labora.com> wrote:
> AFAICS, right now system_dfl_wq duplicates system_unbound_wq. Suppose,
> instead, the default wq could alias the system_unbound_wq.

The idea was just give 1 choice, so remove system_unbound_wq (and
system_wq) in future.
Personally I don't have a strong opinion, but I think it's easier to
have just 1 unbound wq, and 1
per-cpu wq.

But if Tejun has other suggestions, based on your observation, I'm fine with it!

Thanks!

--

Marco Crivellari

L3 Support Engineer, Technology & Product