From 930c2ea566aff59e962c50b2421d5fcc3b98b8be Mon Sep 17 00:00:00 2001 From: Marco Crivellari Date: Sat, 14 Jun 2025 15:35:30 +0200 Subject: [PATCH] workqueue: Add new WQ_PERCPU flag 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. This patch adds a new WQ_PERCPU flag to explicitly request the use of the per-CPU behavior. Both flags coexist for one release cycle to allow callers to transition their calls. Once migration is complete, WQ_UNBOUND can be removed and unbound will become the implicit default. tj: Merged doc patch. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari Signed-off-by: Tejun Heo --- Documentation/core-api/workqueue.rst | 6 ++++++ include/linux/workqueue.h | 1 + 2 files changed, 7 insertions(+) diff --git a/Documentation/core-api/workqueue.rst b/Documentation/core-api/workqueue.rst index e295835fc1164..165ca73e83514 100644 --- a/Documentation/core-api/workqueue.rst +++ b/Documentation/core-api/workqueue.rst @@ -183,6 +183,12 @@ resources, scheduled and executed. BH work items cannot sleep. All other features such as delayed queueing, flushing and canceling are supported. +``WQ_PERCPU`` + Work items queued to a per-cpu wq are bound to a specific CPU. + This flag is the right choice when cpu locality is important. + + This flag is the complement of ``WQ_UNBOUND``. + ``WQ_UNBOUND`` Work items queued to an unbound wq are served by the special worker-pools which host workers which are not bound to any diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 74b0042709cd1..f19072605faaf 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -401,6 +401,7 @@ enum wq_flags { * http://thread.gmane.org/gmane.linux.kernel/1480396 */ WQ_POWER_EFFICIENT = 1 << 7, + WQ_PERCPU = 1 << 8, /* bound to a specific cpu */ __WQ_DESTROYING = 1 << 15, /* internal: workqueue is destroying */ __WQ_DRAINING = 1 << 16, /* internal: workqueue is draining */ -- 2.47.2