From: Marco Crivellari Date: Wed, 17 Sep 2025 15:38:57 +0000 (+0200) Subject: s390/tape: Add WQ_PERCPU to alloc_workqueue users X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=f707d2f7a0c7793406daf0e223bad01bb748343e;p=users%2Fhch%2Fmisc.git s390/tape: Add WQ_PERCPU to alloc_workqueue users 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. 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 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. 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. All existing users have been updated accordingly. Suggested-by: Tejun Heo Signed-off-by: Marco Crivellari Acked-by: Alexander Gordeev Acked-by: Heiko Carstens Signed-off-by: Alexander Gordeev --- diff --git a/drivers/s390/char/tape_3590.c b/drivers/s390/char/tape_3590.c index a1bafaf73f87..2a2931d303cb 100644 --- a/drivers/s390/char/tape_3590.c +++ b/drivers/s390/char/tape_3590.c @@ -1671,7 +1671,7 @@ tape_3590_init(void) DBF_EVENT(3, "3590 init\n"); - tape_3590_wq = alloc_workqueue("tape_3590", 0, 0); + tape_3590_wq = alloc_workqueue("tape_3590", WQ_PERCPU, 0); if (!tape_3590_wq) return -ENOMEM;