Re: [PATCH 1/2] ath6kl: add WQ_PERCPU to alloc_workqueue users

[Frederic Weisbecker <frederic@kernel.org>]

Le Thu, Mar 05, 2026 at 05:44:04PM +0100, Marco Crivellari a écrit :
> On Thu, Nov 13, 2025 at 5:12 PM Marco Crivellari
> <marco.crivellari@suse.com> wrote:
> >
> > 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@kernel.org>
> > Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
> > Link: https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/
> > ---
> >  drivers/net/wireless/ath/ath6kl/usb.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/wireless/ath/ath6kl/usb.c b/drivers/net/wireless/ath/ath6kl/usb.c
> > index 38bb501fc553..bfb21725d779 100644
> > --- a/drivers/net/wireless/ath/ath6kl/usb.c
> > +++ b/drivers/net/wireless/ath/ath6kl/usb.c
> > @@ -637,7 +637,7 @@ static struct ath6kl_usb *ath6kl_usb_create(struct usb_interface *interface)
> >         ar_usb = kzalloc(sizeof(struct ath6kl_usb), GFP_KERNEL);
> >         if (ar_usb == NULL)
> >                 return NULL;
> > -       ar_usb->wq = alloc_workqueue("ath6kl_wq", 0, 0);
> > +       ar_usb->wq = alloc_workqueue("ath6kl_wq", WQ_PERCPU, 0);
> >         if (!ar_usb->wq) {
> >                 kfree(ar_usb);
> >                 return NULL;
> 
> [ Cc-ing Andrew Morton ]
> 
> Hello Andrew,
> 
> This file is orphaned. Can you help me in order to have this patch merged?
> 
> Thank you!
>

Reviewed-by: Frederic Weisbecker <frederic@kernel.org>

-- 
Frederic Weisbecker
SUSE Labs