linux-kernel - Re: [PATCH 2/2] usb: typec: anx7411: add WQ_PERCPU to alloc

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Message-ID: <aRrcjCIeu6cjE6Og@kuha.fi.intel.com>
Date: Mon, 17 Nov 2025 10:27:56 +0200
From: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To: Marco Crivellari <marco.crivellari@...e.com>
Cc: linux-kernel@...r.kernel.org, linux-usb@...r.kernel.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>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH 2/2] usb: typec: anx7411: add WQ_PERCPU to
 alloc_workqueue users

Fri, Nov 07, 2025 at 04:37:31PM +0100, Marco Crivellari kirjoitti:
> 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.
> 
> 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.
> 
> Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> Suggested-by: Tejun Heo <tj@...nel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>

Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>

> ---
>  drivers/usb/typec/anx7411.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/anx7411.c b/drivers/usb/typec/anx7411.c
> index 0ae0a5ee3fae..2e8ae1d2faf9 100644
> --- a/drivers/usb/typec/anx7411.c
> +++ b/drivers/usb/typec/anx7411.c
> @@ -1516,8 +1516,7 @@ static int anx7411_i2c_probe(struct i2c_client *client)
>  
>  	INIT_WORK(&plat->work, anx7411_work_func);
>  	plat->workqueue = alloc_workqueue("anx7411_work",
> -					  WQ_FREEZABLE |
> -					  WQ_MEM_RECLAIM,
> +					  WQ_FREEZABLE | WQ_MEM_RECLAIM | WQ_PERCPU,
>  					  1);
>  	if (!plat->workqueue) {
>  		dev_err(dev, "fail to create work queue\n");
> -- 
> 2.51.1

-- 
heikki