linux-kernel - Re: [PATCH] wifi: wfx: add WQ_PERCPU to alloc

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: <2530603.TnzJ9iJZxx@nb0018864>
Date: Thu, 13 Nov 2025 17:57:40 +0100
From: Jérôme Pouiller <jerome.pouiller@...abs.com>
To: linux-kernel@...r.kernel.org, linux-wireless@...r.kernel.org,
        Marco Crivellari <marco.crivellari@...e.com>
Cc: Tejun Heo <tj@...nel.org>, Lai Jiangshan <jiangshanlai@...il.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Marco Crivellari <marco.crivellari@...e.com>,
        Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH] wifi: wfx: add WQ_PERCPU to alloc_workqueue users

On Thursday 13 November 2025 17:08:25 Central European Standard Time Marco Crivellari wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
> 
> 
> Currently 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.
> This lack of consistency cannot be addressed without refactoring the API.
> For more details see the Link tag below.
> 
> alloc_workqueue() treats all queues as per-CPU by default, while unbound
> workqueues must opt-in via WQ_UNBOUND.
> 
> This default is suboptimal: most workloads benefit from unbound queues,
> allowing the scheduler to place worker threads where they’re needed and
> reducing noise when CPUs are isolated.
> 
> This continues the effort to refactor workqueue APIs, which began with
> the introduction of new workqueues and a new alloc_workqueue flag in:
> 
> commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
> commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag")
> 
> This change adds a new WQ_PERCPU flag to explicitly request
> alloc_workqueue() to be per-cpu when WQ_UNBOUND has not been specified.
> 
> With the introduction of the WQ_PERCPU flag (equivalent to !WQ_UNBOUND),
> any alloc_workqueue() caller that doesn’t explicitly specify WQ_UNBOUND
> must now use WQ_PERCPU.
> 
> Once migration is complete, WQ_UNBOUND can be removed and unbound will
> become the implicit default.
> 
> Suggested-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
> Link: https://urldefense.com/v3/__https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/__;!!N30Cs7Jr!XKe1YoeqdRNkCRNrXBDpd3dyHXefzYb-3Cpd2WmhtEb9vvp1pYw6DF7umzTJlLkLvSdeRGYOrAZAgyS9L-15V9i67-I_-g$
> ---
>  drivers/net/wireless/silabs/wfx/main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/silabs/wfx/main.c b/drivers/net/wireless/silabs/wfx/main.c
> index a61128debbad..dda36e41eed1 100644
> --- a/drivers/net/wireless/silabs/wfx/main.c
> +++ b/drivers/net/wireless/silabs/wfx/main.c
> @@ -364,7 +364,7 @@ int wfx_probe(struct wfx_dev *wdev)
>         wdev->pdata.gpio_wakeup = NULL;
>         wdev->poll_irq = true;
> 
> -       wdev->bh_wq = alloc_workqueue("wfx_bh_wq", WQ_HIGHPRI, 0);
> +       wdev->bh_wq = alloc_workqueue("wfx_bh_wq", WQ_HIGHPRI | WQ_PERCPU, 0);
>         if (!wdev->bh_wq)
>                 return -ENOMEM;
> 
> --
> 2.51.1
> 
> 

Reviewed-by: Jérôme Pouiller <jerome.pouiller@...abs.com>

BTW, this workqueue has changed multiple times. I though it was already
unbound (and I believe it should).

I also think the HIGHPRI is not required (the device perform better
with HIGHPRI, but this is only because we steal the CPU of the other
tasks).

(Anyway, these changes are out of the scope of your PR).


-- 
Jérôme Pouiller