wireless : use a dedicated workqueue for cfg80211.

This patch moves the works cleanup, scan and events to a cfg80211
dedicated workqueue.

Platform driver like eeepc-laptop ought to use works to rfkill (as
new rfkill does lock in rfkill_unregister and the platform driver is
called from rfkill_switch_all which also lock the same mutex).
This raise a new issue in itself that the work scheduled by the platform
driver to the global worqueue calls wiphy_unregister which flush_work
scan and event works (which thus flush works on the global workqueue inside
a work on the global workqueue) and also put on hold the wdev_cleanup_work
(which prevents the dev_put on netdev thus indefinite Usage count error on
wifi device).

Signed-off-by: Johannes Berg <[e-mail]>
Signed-off-by: Alban Browaeys <[e-mail]>
Signed-off-by: John W. Linville <[e-mail]>

net/wireless/core.c

···
 /* for debugfs */
 static struct dentry *ieee80211_debugfs_dir;
 
+/* for the cleanup, scan and event works */
+struct workqueue_struct *cfg80211_wq;
+
 /* requires cfg80211_mutex to be held! */
 struct cfg80211_registered_device *cfg80211_rdev_by_wiphy_idx(int wiphy_idx)
 {
···
 		break;
 	case NETDEV_DOWN:
 		dev_hold(dev);
-		schedule_work(&wdev->cleanup_work);
+		queue_work(cfg80211_wq, &wdev->cleanup_work);
 		break;
 	case NETDEV_UP:
 		/*
···
 	if (err)
 		goto out_fail_reg;
 
+	cfg80211_wq = create_singlethread_workqueue("cfg80211");
+	if (!cfg80211_wq)
+		goto out_fail_wq;
+
 	return 0;
 
+out_fail_wq:
+	regulatory_exit();
 out_fail_reg:
 	debugfs_remove(ieee80211_debugfs_dir);
 out_fail_nl80211:
···
 	wiphy_sysfs_exit();
 	regulatory_exit();
 	unregister_pernet_device(&cfg80211_pernet_ops);
+	destroy_workqueue(cfg80211_wq);
 }
 module_exit(cfg80211_exit);

net/wireless/core.h

···
 	return (wiphy_idx >= 0);
 }
 
+
+extern struct workqueue_struct *cfg80211_wq;
 extern struct mutex cfg80211_mutex;
 extern struct list_head cfg80211_rdev_list;
 extern int cfg80211_rdev_list_generation;

net/wireless/ibss.c

···
 	spin_lock_irqsave(&wdev->event_lock, flags);
 	list_add_tail(&ev->list, &wdev->event_list);
 	spin_unlock_irqrestore(&wdev->event_lock, flags);
-	schedule_work(&rdev->event_work);
+	queue_work(cfg80211_wq, &rdev->event_work);
 }
 EXPORT_SYMBOL(cfg80211_ibss_joined);
 

net/wireless/scan.c

···
 	WARN_ON(request != wiphy_to_dev(request->wiphy)->scan_req);
 
 	request->aborted = aborted;
-	schedule_work(&wiphy_to_dev(request->wiphy)->scan_done_wk);
+	queue_work(cfg80211_wq, &wiphy_to_dev(request->wiphy)->scan_done_wk);
 }
 EXPORT_SYMBOL(cfg80211_scan_done);
 

net/wireless/sme.c

···
 	spin_lock_irqsave(&wdev->event_lock, flags);
 	list_add_tail(&ev->list, &wdev->event_list);
 	spin_unlock_irqrestore(&wdev->event_lock, flags);
-	schedule_work(&rdev->event_work);
+	queue_work(cfg80211_wq, &rdev->event_work);
 }
 EXPORT_SYMBOL(cfg80211_connect_result);
 
···
 	spin_lock_irqsave(&wdev->event_lock, flags);
 	list_add_tail(&ev->list, &wdev->event_list);
 	spin_unlock_irqrestore(&wdev->event_lock, flags);
-	schedule_work(&rdev->event_work);
+	queue_work(cfg80211_wq, &rdev->event_work);
 }
 EXPORT_SYMBOL(cfg80211_roamed);
 
···
 	spin_lock_irqsave(&wdev->event_lock, flags);
 	list_add_tail(&ev->list, &wdev->event_list);
 	spin_unlock_irqrestore(&wdev->event_lock, flags);
-	schedule_work(&rdev->event_work);
+	queue_work(cfg80211_wq, &rdev->event_work);
 }
 EXPORT_SYMBOL(cfg80211_disconnected);