[PATCH v2] umh: replace use of system_unbound_wq with system_dfl_wq

[PATCH v2] umh: replace use of system_unbound_wq with system_dfl_wq

[Marco Crivellari]

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.

system_unbound_wq should be the default workqueue so as not to enforce
locality constraints for random work whenever it's not required.

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")

Switch to using system_dfl_wq because system_unbound_wq is going away as
part of a workqueue restructuring.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
Changes in v2:
- improved commit log
- rebased on v6.18-rc4
---
 kernel/umh.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/umh.c b/kernel/umh.c
index b4da45a3a7cf..cda899327952 100644
--- a/kernel/umh.c
+++ b/kernel/umh.c
@@ -430,7 +430,7 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
 	sub_info->complete = (wait == UMH_NO_WAIT) ? NULL : &done;
 	sub_info->wait = wait;
 
-	queue_work(system_unbound_wq, &sub_info->work);
+	queue_work(system_dfl_wq, &sub_info->work);
 	if (wait == UMH_NO_WAIT)	/* task has freed sub_info */
 		goto unlock;
 
-- 
2.51.1

Re: [PATCH v2] umh: replace use of system_unbound_wq with system_dfl_wq

[Marco Crivellari]

On Fri, Nov 7, 2025 at 5:06 PM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> [...]
> ---
>  kernel/umh.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/umh.c b/kernel/umh.c
> index b4da45a3a7cf..cda899327952 100644
> --- a/kernel/umh.c
> +++ b/kernel/umh.c
> @@ -430,7 +430,7 @@ int call_usermodehelper_exec(struct subprocess_info *sub_info, int wait)
>         sub_info->complete = (wait == UMH_NO_WAIT) ? NULL : &done;
>         sub_info->wait = wait;
>
> -       queue_work(system_unbound_wq, &sub_info->work);
> +       queue_work(system_dfl_wq, &sub_info->work);
>         if (wait == UMH_NO_WAIT)        /* task has freed sub_info */
>                 goto unlock;

Gentle ping.

Thanks!


-- 

Marco Crivellari

L3 Support Engineer

Re: [PATCH v2] umh: replace use of system_unbound_wq with system_dfl_wq

[Marco Crivellari]

On Fri, Nov 7, 2025 at 5:06 PM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> [...]
>  kernel/umh.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Gentle ping.

Thanks!


-- 

Marco Crivellari

L3 Support Engineer

Re: [PATCH v2] umh: replace use of system_unbound_wq with system_dfl_wq

[Marco Crivellari]

On Fri, Nov 7, 2025 at 5:06 PM Marco Crivellari
<marco.crivellari@suse.com> wrote:
>  kernel/umh.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Gentle ping.

Thanks!
--

Marco Crivellari

L3 Support Engineer

Re: [PATCH v2] umh: replace use of system_unbound_wq with system_dfl_wq

[Frederic Weisbecker]

Le Fri, Nov 07, 2025 at 05:06:38PM +0100, Marco Crivellari a écrit :
> 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.
> 
> system_unbound_wq should be the default workqueue so as not to enforce
> locality constraints for random work whenever it's not required.
> 
> 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")
> 
> Switch to using system_dfl_wq because system_unbound_wq is going away as
> part of a workqueue restructuring.
> 
> Suggested-by: Tejun Heo <tj@kernel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>

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

-- 
Frederic Weisbecker
SUSE Labs

Re: [PATCH v2] umh: replace use of system_unbound_wq with system_dfl_wq

[Marco Crivellari]

Hi,

On Fri, Nov 7, 2025 at 5:06 PM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> [...]
>  kernel/umh.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Gentle ping.

Thanks.

-- 

Marco Crivellari

L3 Support Engineer

Re: [PATCH v2] umh: replace use of system_unbound_wq with system_dfl_wq

[Marco Crivellari]

Hi,

On Fri, Nov 7, 2025 at 5:06 PM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> [...]
> Changes in v2:
> - improved commit log
> - rebased on v6.18-rc4
> ---
>  kernel/umh.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Gentle ping.

Thanks!

-- 

Marco Crivellari

SUSE Labs

Re: [PATCH v2] umh: replace use of system_unbound_wq with system_dfl_wq

[Marco Crivellari]

On Fri, Nov 7, 2025 at 5:06 PM Marco Crivellari
<marco.crivellari@suse.com> wrote:
> [...]
>  kernel/umh.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Hi,

Gentle ping.

Thanks!

-- 

Marco Crivellari

SUSE Labs