On 2022/05/01 17:53, Kalle Valo wrote: > So now the thread is created every time the module loaded, even if > there's no device available. Excuse me, but what thread? alloc_workqueue() without WQ_MEM_RECLAIM flag does not create a thread, and therefore consumes little resource where there's no device available does not matter. > Also I'm not really a fan of global > variables (wfx_wq). I would rather create a workqueue per device in > wfx_probe() or use the workqueue provided by mac80211. Whatever is fine. wfx is the last user of flush_workqueue(system_*_wq) and I want to know whether I can include system_highpri_wq into below patch. Subject: [PATCH] workqueue: wrap flush_workqueue() using a macro While a conversion to stop flushing of kernel-global workqueues is in progress, we can warn users who are not aware of this conversion, by wrapping flush_workqueue() as a macro and injecting BUILD_BUG_ON() tests. --- include/linux/workqueue.h | 27 +++++++++++++++++++++++++++ kernel/workqueue.c | 1 + 2 files changed, 28 insertions(+) diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h index 7b13fae377e2..3eaf19262d19 100644 --- a/include/linux/workqueue.h +++ b/include/linux/workqueue.h @@ -654,4 +654,31 @@ int workqueue_offline_cpu(unsigned int cpu); void __init workqueue_init_early(void); void __init workqueue_init(void); +/* + * Detect attempt to flush system-wide workqueues at compile time when possible. + * See https://lkml.kernel.org/r/49925af7-78a8-a3dd-bce6-cfc02e1a9236@xxxxxxxxxxxxxxxxxxx for + * reasons and steps for converting system-wide workqueues into local workqueues. + * Checks for system_wq and system_highpri_wq will be added after + * all in-tree users stopped flushing these workqueues. + */ +#define flush_workqueue(wq) \ +({ \ + BUILD_BUG_ON_MSG(__builtin_constant_p(&(wq) == &system_long_wq) && \ + &(wq) == &system_long_wq, \ + "Please avoid flushing system_long_wq."); \ + BUILD_BUG_ON_MSG(__builtin_constant_p(&(wq) == &system_unbound_wq) && \ + &(wq) == &system_unbound_wq, \ + "Please avoid flushing system_unbound_wq."); \ + BUILD_BUG_ON_MSG(__builtin_constant_p(&(wq) == &system_freezable_wq) && \ + &(wq) == &system_freezable_wq, \ + "Please avoid flushing system_freezable_wq."); \ + BUILD_BUG_ON_MSG(__builtin_constant_p(&(wq) == &system_power_efficient_wq) && \ + &(wq) == &system_power_efficient_wq, \ + "Please avoid flushing system_power_efficient_wq."); \ + BUILD_BUG_ON_MSG(__builtin_constant_p(&(wq) == &system_freezable_power_efficient_wq) && \ + &(wq) == &system_freezable_power_efficient_wq, \ + "Please avoid flushing system_freezable_power_efficient_wq."); \ + flush_workqueue(wq); \ +}) + #endif diff --git a/kernel/workqueue.c b/kernel/workqueue.c index b447012df177..de53813a92d2 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -2813,6 +2813,7 @@ static void warn_flush_attempt(struct workqueue_struct *wq) * This function sleeps until all work items which were queued on entry * have finished execution, but it is not livelocked by new incoming ones. */ +#undef flush_workqueue void flush_workqueue(struct workqueue_struct *wq) { struct wq_flusher this_flusher = { -- 2.34.1
