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Message-ID: <20250905091325.112168-2-marco.crivellari@suse.com>
Date: Fri, 5 Sep 2025 11:13:23 +0200
From: Marco Crivellari <marco.crivellari@...e.com>
To: linux-kernel@...r.kernel.org
Cc: Tejun Heo <tj@...nel.org>,
Lai Jiangshan <jiangshanlai@...il.com>,
Frederic Weisbecker <frederic@...nel.org>,
Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
Marco Crivellari <marco.crivellari@...e.com>,
Michal Hocko <mhocko@...e.com>
Subject: [PATCH 1/3] workqueue: replace use of system_unbound_wq with system_dfl_wq
Currently if a user enqueue 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 consistentcy 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.
Adding system_dfl_wq to encourage its use when unbound work should be used.
queue_work() / queue_delayed_work() / mod_delayed_work() will now use the
new unbound wq: whether the user still use the old wq a warn will be
printed along with a wq redirect to the new one.
The old system_unbound_wq will be kept for a few release cycles.
Suggested-by: Tejun Heo <tj@...nel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@...e.com>
---
include/linux/workqueue.h | 4 ++--
kernel/workqueue.c | 2 +-
2 files changed, 3 insertions(+), 3 deletions(-)
diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index f19072605faa..0e14d78fb970 100644
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -779,8 +779,8 @@ extern void __warn_flushing_systemwide_wq(void)
_wq == system_highpri_wq) || \
(__builtin_constant_p(_wq == system_long_wq) && \
_wq == system_long_wq) || \
- (__builtin_constant_p(_wq == system_unbound_wq) && \
- _wq == system_unbound_wq) || \
+ (__builtin_constant_p(_wq == system_dfl_wq) && \
+ _wq == system_dfl_wq) || \
(__builtin_constant_p(_wq == system_freezable_wq) && \
_wq == system_freezable_wq) || \
(__builtin_constant_p(_wq == system_power_efficient_wq) && \
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 62f020050de1..687285701655 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2936,7 +2936,7 @@ static void idle_worker_timeout(struct timer_list *t)
raw_spin_unlock_irq(&pool->lock);
if (do_cull)
- queue_work(system_unbound_wq, &pool->idle_cull_work);
+ queue_work(system_dfl_wq, &pool->idle_cull_work);
}
/**
--
2.51.0
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