isdn/capi: make kcapi use a separate workqueue

flush_scheduled_work() is deprecated and will be removed.  Because
kcapi uses fire-and-forget type works, it's impossible to flush each
work explicitly.  Create and use a dedicated workqueue instead.

Please note that with recent workqueue changes, each workqueue doesn't
reserve a lot of resources and using it as a flush domain is fine.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Jan Kiszka <jan.kiszka@web.de>

drivers/isdn/capi/kcapi.c

@@ -38,6 +38,7 @@
 #include <linux/rcupdate.h>
 
 static int showcapimsgs = 0;
+static struct workqueue_struct *kcapi_wq;
 
 MODULE_DESCRIPTION("CAPI4Linux: kernel CAPI layer");
 MODULE_AUTHOR("Carsten Paeth");
@@ -291,7 +292,7 @@ static int notify_push(unsigned int event_type, u32 controller)
 	event->type = event_type;
 	event->controller = controller;
 
-	schedule_work(&event->work);
+	queue_work(kcapi_wq, &event->work);
 	return 0;
 }
 
@@ -408,7 +409,7 @@ void capi_ctr_handle_message(struct capi_ctr *ctr, u16 appl,
 		goto error;
 	}
 	skb_queue_tail(&ap->recv_queue, skb);
-	schedule_work(&ap->recv_work);
+	queue_work(kcapi_wq, &ap->recv_work);
 	rcu_read_unlock();
 
 	return;
@@ -743,7 +744,7 @@ u16 capi20_release(struct capi20_appl *ap)
 
 	mutex_unlock(&capi_controller_lock);
 
-	flush_scheduled_work();
+	flush_workqueue(kcapi_wq);
 	skb_queue_purge(&ap->recv_queue);
 
 	if (showcapimsgs & 1) {
@@ -1285,21 +1286,30 @@ static int __init kcapi_init(void)
 {
 	int err;
 
+	kcapi_wq = alloc_workqueue("kcapi", 0, 0);
+	if (!kcapi_wq)
+		return -ENOMEM;
+
 	register_capictr_notifier(&capictr_nb);
 
 	err = cdebug_init();
-	if (!err)
-		kcapi_proc_init();
-	return err;
+	if (err) {
+		unregister_capictr_notifier(&capictr_nb);
+		destroy_workqueue(kcapi_wq);
+		return err;
+	}
+
+	kcapi_proc_init();
+	return 0;
 }
 
 static void __exit kcapi_exit(void)
 {
         kcapi_proc_exit();
 
-	/* make sure all notifiers are finished */
-	flush_scheduled_work();
+	unregister_capictr_notifier(&capictr_nb);
 	cdebug_exit();
+	destroy_workqueue(kcapi_wq);
 }
 
 module_init(kcapi_init);