From: Marco Crivellari Date: Mon, 9 Mar 2026 13:15:28 +0000 (+0100) Subject: workqueue: Add system_dfl_long_wq for long unbound works X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c116737e972ea74f4468a1bd0703d623a3c0ee4a;p=thirdparty%2Fkernel%2Flinux.git workqueue: Add system_dfl_long_wq for long unbound works Currently there are users of queue_delayed_work() who specify system_long_wq, the per-cpu workqueue. This workqueue should be used for long per-cpu works, but queue_delayed_work() queue the work using: queue_delayed_work_on(WORK_CPU_UNBOUND, ...); This would end up calling __queue_delayed_work() that does: if (housekeeping_enabled(HK_TYPE_TIMER)) { // [....] } else { if (likely(cpu == WORK_CPU_UNBOUND)) add_timer_global(timer); else add_timer_on(timer, cpu); } So when cpu == WORK_CPU_UNBOUND the timer is global and is not using a specific CPU. Later, when __queue_work() is called: if (req_cpu == WORK_CPU_UNBOUND) { if (wq->flags & WQ_UNBOUND) cpu = wq_select_unbound_cpu(raw_smp_processor_id()); else cpu = raw_smp_processor_id(); } Because the wq is not unbound, it takes the CPU where the timer fired and enqueue the work on that CPU. The consequence of all of this is that the work can run anywhere, depending on where the timer fired. Introduce system_dfl_long_wq in order to change, in a future step, users that are still calling: queue_delayed_work(system_long_wq, ...); with the new system_dfl_long_wq instead, so that the work may benefit from scheduler task placement. Signed-off-by: Marco Crivellari Signed-off-by: Tejun Heo --- diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index fc5744402a669..8e0855d56e740 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -440,6 +440,9 @@ enum wq_consts { * system_long_wq is similar to system_percpu_wq but may host long running * works. Queue flushing might take relatively long. * + * system_dfl_long_wq is similar to system_dfl_wq but it may host long running + * works. + * * system_dfl_wq is unbound workqueue. Workers are not bound to * any specific CPU, not concurrency managed, and all queued works are * executed immediately as long as max_active limit is not reached and @@ -468,6 +471,7 @@ extern struct workqueue_struct *system_power_efficient_wq; extern struct workqueue_struct *system_freezable_power_efficient_wq; extern struct workqueue_struct *system_bh_wq; extern struct workqueue_struct *system_bh_highpri_wq; +extern struct workqueue_struct *system_dfl_long_wq; void workqueue_softirq_action(bool highpri); void workqueue_softirq_dead(unsigned int cpu); @@ -783,6 +787,8 @@ 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_dfl_long_wq) && \ + _wq == system_dfl_long_wq) || \ (__builtin_constant_p(_wq == system_dfl_wq) && \ _wq == system_dfl_wq) || \ (__builtin_constant_p(_wq == system_freezable_wq) && \ diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 2f95cb0d2f1b8..2d8ff903f1134 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -530,6 +530,8 @@ struct workqueue_struct *system_bh_wq; EXPORT_SYMBOL_GPL(system_bh_wq); struct workqueue_struct *system_bh_highpri_wq; EXPORT_SYMBOL_GPL(system_bh_highpri_wq); +struct workqueue_struct *system_dfl_long_wq __ro_after_init; +EXPORT_SYMBOL_GPL(system_dfl_long_wq); static int worker_thread(void *__worker); static void workqueue_sysfs_unregister(struct workqueue_struct *wq); @@ -7954,11 +7956,12 @@ void __init workqueue_init_early(void) system_bh_wq = alloc_workqueue("events_bh", WQ_BH | WQ_PERCPU, 0); system_bh_highpri_wq = alloc_workqueue("events_bh_highpri", WQ_BH | WQ_HIGHPRI | WQ_PERCPU, 0); + system_dfl_long_wq = alloc_workqueue("events_dfl_long", WQ_UNBOUND, WQ_MAX_ACTIVE); BUG_ON(!system_wq || !system_percpu_wq|| !system_highpri_wq || !system_long_wq || !system_unbound_wq || !system_freezable_wq || !system_dfl_wq || !system_power_efficient_wq || !system_freezable_power_efficient_wq || - !system_bh_wq || !system_bh_highpri_wq); + !system_bh_wq || !system_bh_highpri_wq || !system_dfl_long_wq); } static void __init wq_cpu_intensive_thresh_init(void)