workqueue: Add warnings and fallback if system_{unbound}_wq is used

Currently many users transitioned already to the new introduced workqueue
(system_percpu_wq, system_dfl_wq), but there are new users who still use the
older system_wq and system_unbound_wq.

This change try to push this transition forward, by warning whether the old
workqueues are used.

Link: https://lore.kernel.org/all/20250221112003.1dSuoGyc@linutronix.de/
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/include/linux/workqueue.h b/include/linux/workqueue.h
index 6177624539b3b35027ef4900eb0fa3490be392c9..a283766a192aafe07620de77819ad8daf54c22e7 100644 (file)
--- a/include/linux/workqueue.h
+++ b/include/linux/workqueue.h
@@ -409,6 +409,7 @@ enum wq_flags {
        __WQ_DRAINING           = 1 << 16, /* internal: workqueue is draining */
        __WQ_ORDERED            = 1 << 17, /* internal: workqueue is ordered */
        __WQ_LEGACY             = 1 << 18, /* internal: create*_workqueue() */
+       __WQ_DEPRECATED         = 1 << 19, /* internal: workqueue is deprecated */
 
        /* BH wq only allows the following flags */
        __WQ_BH_ALLOWS          = WQ_BH | WQ_HIGHPRI | WQ_PERCPU,

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 35b0c8f4f10f202909465e207c7e06c96571ddab..088cd9b70fca3800ed60f7c3fc2a9c623d74066a 100644 (file)
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2280,6 +2280,14 @@ static void __queue_work(int cpu, struct workqueue_struct *wq,
        unsigned int work_flags;
        unsigned int req_cpu = cpu;
 
+       /*
+        * NOTE: Check whether the used workqueue is deprecated and warn
+        */
+       if (unlikely(wq->flags & __WQ_DEPRECATED))
+               pr_warn_once("workqueue: work func %ps enqueued on deprecated workqueue. "
+                       "Use system_{percpu|dfl}_wq instead.\n",
+                       work->func);
+
        /*
         * While a work item is PENDING && off queue, a task trying to
         * steal the PENDING will busy-loop waiting for it to either get
@@ -8013,12 +8021,12 @@ void __init workqueue_init_early(void)
                ordered_wq_attrs[i] = attrs;
        }
 
-       system_wq = alloc_workqueue("events", WQ_PERCPU, 0);
+       system_wq = alloc_workqueue("events", WQ_PERCPU | __WQ_DEPRECATED, 0);
        system_percpu_wq = alloc_workqueue("events", WQ_PERCPU, 0);
        system_highpri_wq = alloc_workqueue("events_highpri",
                                            WQ_HIGHPRI | WQ_PERCPU, 0);
        system_long_wq = alloc_workqueue("events_long", WQ_PERCPU, 0);
-       system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, WQ_MAX_ACTIVE);
+       system_unbound_wq = alloc_workqueue("events_unbound", WQ_UNBOUND | __WQ_DEPRECATED, WQ_MAX_ACTIVE);
        system_dfl_wq = alloc_workqueue("events_unbound", WQ_UNBOUND, WQ_MAX_ACTIVE);
        system_freezable_wq = alloc_workqueue("events_freezable",
                                              WQ_FREEZABLE | WQ_PERCPU, 0);