[PATCH v2] tracing: Replace use of system_wq with system_dfl_wq

[PATCH v2] tracing: Replace use of system_wq with system_dfl_wq

[Marco Crivellari]

This patch continues the effort to refactor workqueue APIs, which has begun
with the changes introducing new workqueues and a new alloc_workqueue flag:

   commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
   commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag")

The point of the refactoring is to eventually alter the default behavior of
workqueues to become unbound by default so that their workload placement is
optimized by the scheduler.

Before that to happen after a careful review and conversion of each individual
case, workqueue users must be converted to the better named new workqueues with
no intended behaviour changes:

   system_wq -> system_percpu_wq
   system_unbound_wq -> system_dfl_wq

This specific workflow has no benefits being per-cpu, so instead of
system_percpu_wq the new unbound workqueue has been used (system_dfl_wq).

This way the old obsolete workqueues (system_wq, system_unbound_wq) can be
removed in the future.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
---
Changes in v2:
- use system_dfl_wq instead of system_percpu_wq because this workload has no
  benefits being per-cpu.

- rebase on v6.19-rc3.

 kernel/trace/trace_events_filter.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
index 385af8405392..7001e34476ee 100644
--- a/kernel/trace/trace_events_filter.c
+++ b/kernel/trace/trace_events_filter.c
@@ -1375,7 +1375,7 @@ static void free_filter_list_tasks(struct rcu_head *rhp)
 	struct filter_head *filter_list = container_of(rhp, struct filter_head, rcu);
 
 	INIT_RCU_WORK(&filter_list->rwork, free_filter_list_work);
-	queue_rcu_work(system_wq, &filter_list->rwork);
+	queue_rcu_work(system_dfl_wq, &filter_list->rwork);
 }
 
 /*
-- 
2.52.0

Re: [PATCH v2] tracing: Replace use of system_wq with system_dfl_wq

[Steven Rostedt]

On Tue, 30 Dec 2025 15:28:20 +0100
Marco Crivellari <marco.crivellari@suse.com> wrote:

> This patch continues the effort to refactor workqueue APIs, which has begun
> with the changes introducing new workqueues and a new alloc_workqueue flag:
> 
>    commit 128ea9f6ccfb ("workqueue: Add system_percpu_wq and system_dfl_wq")
>    commit 930c2ea566af ("workqueue: Add new WQ_PERCPU flag")
> 
> The point of the refactoring is to eventually alter the default behavior of
> workqueues to become unbound by default so that their workload placement is
> optimized by the scheduler.
> 
> Before that to happen after a careful review and conversion of each individual
> case, workqueue users must be converted to the better named new workqueues with
> no intended behaviour changes:
> 
>    system_wq -> system_percpu_wq
>    system_unbound_wq -> system_dfl_wq
> 
> This specific workflow has no benefits being per-cpu, so instead of
> system_percpu_wq the new unbound workqueue has been used (system_dfl_wq).
> 
> This way the old obsolete workqueues (system_wq, system_unbound_wq) can be
> removed in the future.
> 
> Suggested-by: Tejun Heo <tj@kernel.org>
> Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
> ---
> Changes in v2:
> - use system_dfl_wq instead of system_percpu_wq because this workload has no
>   benefits being per-cpu.

Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>

-- Steve

Re: [PATCH v2] tracing: Replace use of system_wq with system_dfl_wq

[Steven Rostedt]

On Tue, 30 Dec 2025 09:42:36 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> > Suggested-by: Tejun Heo <tj@kernel.org>
> > Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
> > ---
> > Changes in v2:
> > - use system_dfl_wq instead of system_percpu_wq because this workload has no
> >   benefits being per-cpu.  
> 
> Acked-by: Steven Rostedt (Google) <rostedt@goodmis.org>

I guess I'll take this through my tree, as I'm pulling in patches now to
base off of -rc5.

-- Steve

Re: [PATCH v2] tracing: Replace use of system_wq with system_dfl_wq

[Marco Crivellari]

On Fri, Jan 9, 2026 at 8:27 PM Steven Rostedt <rostedt@goodmis.org> wrote:
> [...]
> I guess I'll take this through my tree, as I'm pulling in patches now to
> base off of -rc5.

Many thanks Steven!

-- 

Marco Crivellari

L3 Support Engineer