Re: [PATCH] mmc: omap: add WQ_PERCPU to alloc_workqueue users

[Ulf Hansson]

On Fri, 7 Nov 2025 at 15:19, Marco Crivellari <marco.crivellari@xxxxxxxx> 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.
>
> 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@xxxxxxxxxx>
> Signed-off-by: Marco Crivellari <marco.crivellari@xxxxxxxx>

Applied for next, thanks!

Kind regards
Uffe


> ---
>  drivers/mmc/host/omap.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/mmc/host/omap.c b/drivers/mmc/host/omap.c
> index 52ac3f128a1c..4a13111e1698 100644
> --- a/drivers/mmc/host/omap.c
> +++ b/drivers/mmc/host/omap.c
> @@ -1477,7 +1477,7 @@ static int mmc_omap_probe(struct platform_device *pdev)
>         host->nr_slots = pdata->nr_slots;
>         host->reg_shift = (mmc_omap7xx() ? 1 : 2);
>
> -       host->mmc_omap_wq = alloc_workqueue("mmc_omap", 0, 0);
> +       host->mmc_omap_wq = alloc_workqueue("mmc_omap", WQ_PERCPU, 0);
>         if (!host->mmc_omap_wq) {
>                 ret = -ENOMEM;
>                 goto err_plat_cleanup;
> --
> 2.51.1
>