cfg80211: vastly simplify locking

Virtually all code paths in cfg80211 already (need to) hold
the RTNL. As such, there's little point in having another
four mutexes for various parts of the code, they just cause
lock ordering issues (and much of the time, the RTNL and a
few of the others need thus be held.)

Simplify all this by getting rid of the extra four mutexes
and just use the RTNL throughout. Only a few code changes
were needed to do this and we can get rid of a work struct
for bonus points.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 30 insertions, 136 deletions

diff --git a/net/wireless/core.c b/net/wireless/core.c
index 9416b8f..5fc642d 100644
--- a/net/wireless/core.c
+++ b/net/wireless/core.c
@@ -36,12 +36,10 @@ MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("wireless configuration support");
 MODULE_ALIAS_GENL_FAMILY(NL80211_GENL_NAME);
 
-/* RCU-protected (and cfg80211_mutex for writers) */
+/* RCU-protected (and RTNL for writers) */
 LIST_HEAD(cfg80211_rdev_list);
 int cfg80211_rdev_list_generation;
 
-DEFINE_MUTEX(cfg80211_mutex);
-
 /* for debugfs */
 static struct dentry *ieee80211_debugfs_dir;
 
@@ -53,12 +51,11 @@ module_param(cfg80211_disable_40mhz_24ghz, bool, 0644);
 MODULE_PARM_DESC(cfg80211_disable_40mhz_24ghz,
 		 "Disable 40MHz support in the 2.4GHz band");
 
-/* requires cfg80211_mutex to be held! */
 struct cfg80211_registered_device *cfg80211_rdev_by_wiphy_idx(int wiphy_idx)
 {
 	struct cfg80211_registered_device *result = NULL, *rdev;
 
-	assert_cfg80211_lock();
+	ASSERT_RTNL();
 
 	list_for_each_entry(rdev, &cfg80211_rdev_list, list) {
 		if (rdev->wiphy_idx == wiphy_idx) {
@@ -77,12 +74,11 @@ int get_wiphy_idx(struct wiphy *wiphy)
 	return rdev->wiphy_idx;
 }
 
-/* requires cfg80211_rdev_mutex to be held! */
 struct wiphy *wiphy_idx_to_wiphy(int wiphy_idx)
 {
 	struct cfg80211_registered_device *rdev;
 
-	assert_cfg80211_lock();
+	ASSERT_RTNL();
 
 	rdev = cfg80211_rdev_by_wiphy_idx(wiphy_idx);
 	if (!rdev)
@@ -90,14 +86,13 @@ struct wiphy *wiphy_idx_to_wiphy(int wiphy_idx)
 	return &rdev->wiphy;
 }
 
-/* requires cfg80211_mutex to be held */
 int cfg80211_dev_rename(struct cfg80211_registered_device *rdev,
 			char *newname)
 {
 	struct cfg80211_registered_device *rdev2;
 	int wiphy_idx, taken = -1, result, digits;
 
-	assert_cfg80211_lock();
+	ASSERT_RTNL();
 
 	/* prohibit calling the thing phy%d when %d is not its number */
 	sscanf(newname, PHY_NAME "%d%n", &wiphy_idx, &taken);
@@ -195,8 +190,7 @@ static void cfg80211_rfkill_poll(struct rfkill *rfkill, void *data)
 void cfg80211_stop_p2p_device(struct cfg80211_registered_device *rdev,
 			      struct wireless_dev *wdev)
 {
-	lockdep_assert_held(&rdev->devlist_mtx);
-	lockdep_assert_held(&rdev->sched_scan_mtx);
+	ASSERT_RTNL();
 
 	if (WARN_ON(wdev->iftype != NL80211_IFTYPE_P2P_DEVICE))
 		return;
@@ -235,8 +229,6 @@ static int cfg80211_rfkill_set_block(void *data, bool blocked)
 
 	rtnl_lock();
 
-	/* read-only iteration need not hold the devlist_mtx */
-
 	list_for_each_entry(wdev, &rdev->wdev_list, list) {
 		if (wdev->netdev) {
 			dev_close(wdev->netdev);
@@ -245,12 +237,7 @@ static int cfg80211_rfkill_set_block(void *data, bool blocked)
 		/* otherwise, check iftype */
 		switch (wdev->iftype) {
 		case NL80211_IFTYPE_P2P_DEVICE:
-			/* but this requires it */
-			mutex_lock(&rdev->devlist_mtx);
-			mutex_lock(&rdev->sched_scan_mtx);
 			cfg80211_stop_p2p_device(rdev, wdev);
-			mutex_unlock(&rdev->sched_scan_mtx);
-			mutex_unlock(&rdev->devlist_mtx);
 			break;
 		default:
 			break;
@@ -278,10 +265,7 @@ static void cfg80211_event_work(struct work_struct *work)
 			    event_work);
 
 	rtnl_lock();
-	cfg80211_lock_rdev(rdev);
-
 	cfg80211_process_rdev_events(rdev);
-	cfg80211_unlock_rdev(rdev);
 	rtnl_unlock();
 }
 
@@ -323,9 +307,6 @@ struct wiphy *wiphy_new(const struct cfg80211_ops *ops, int sizeof_priv)
 	/* give it a proper name */
 	dev_set_name(&rdev->wiphy.dev, PHY_NAME "%d", rdev->wiphy_idx);
 
-	mutex_init(&rdev->mtx);
-	mutex_init(&rdev->devlist_mtx);
-	mutex_init(&rdev->sched_scan_mtx);
 	INIT_LIST_HEAD(&rdev->wdev_list);
 	INIT_LIST_HEAD(&rdev->beacon_registrations);
 	spin_lock_init(&rdev->beacon_registrations_lock);
@@ -573,11 +554,11 @@ int wiphy_register(struct wiphy *wiphy)
 	/* check and set up bitrates */
 	ieee80211_set_bitrate_flags(wiphy);
 
-	mutex_lock(&cfg80211_mutex);
+	rtnl_lock();
 
 	res = device_add(&rdev->wiphy.dev);
 	if (res) {
-		mutex_unlock(&cfg80211_mutex);
+		rtnl_unlock();
 		return res;
 	}
 
@@ -606,25 +587,18 @@ int wiphy_register(struct wiphy *wiphy)
 	}
 
 	cfg80211_debugfs_rdev_add(rdev);
-	mutex_unlock(&cfg80211_mutex);
 
-	/*
-	 * due to a locking dependency this has to be outside of the
-	 * cfg80211_mutex lock
-	 */
 	res = rfkill_register(rdev->rfkill);
 	if (res) {
 		device_del(&rdev->wiphy.dev);
 
-		mutex_lock(&cfg80211_mutex);
 		debugfs_remove_recursive(rdev->wiphy.debugfsdir);
 		list_del_rcu(&rdev->list);
 		wiphy_regulatory_deregister(wiphy);
-		mutex_unlock(&cfg80211_mutex);
+		rtnl_unlock();
 		return res;
 	}
 
-	rtnl_lock();
 	rdev->wiphy.registered = true;
 	rtnl_unlock();
 	return 0;
@@ -654,25 +628,19 @@ void wiphy_unregister(struct wiphy *wiphy)
 {
 	struct cfg80211_registered_device *rdev = wiphy_to_dev(wiphy);
 
-	rtnl_lock();
-	rdev->wiphy.registered = false;
-	rtnl_unlock();
-
-	rfkill_unregister(rdev->rfkill);
-
-	/* protect the device list */
-	mutex_lock(&cfg80211_mutex);
-
 	wait_event(rdev->dev_wait, ({
 		int __count;
-		mutex_lock(&rdev->devlist_mtx);
+		rtnl_lock();
 		__count = rdev->opencount;
-		mutex_unlock(&rdev->devlist_mtx);
+		rtnl_unlock();
 		__count == 0; }));
 
-	mutex_lock(&rdev->devlist_mtx);
+	rtnl_lock();
+	rdev->wiphy.registered = false;
+
+	rfkill_unregister(rdev->rfkill);
+
 	BUG_ON(!list_empty(&rdev->wdev_list));
-	mutex_unlock(&rdev->devlist_mtx);
 
 	/*
 	 * First remove the hardware from everywhere, this makes
@@ -683,20 +651,6 @@ void wiphy_unregister(struct wiphy *wiphy)
 	synchronize_rcu();
 
 	/*
-	 * Try to grab rdev->mtx. If a command is still in progress,
-	 * hopefully the driver will refuse it since it's tearing
-	 * down the device already. We wait for this command to complete
-	 * before unlinking the item from the list.
-	 * Note: as codified by the BUG_ON above we cannot get here if
-	 * a virtual interface is still present. Hence, we can only get
-	 * to lock contention here if userspace issues a command that
-	 * identified the hardware by wiphy index.
-	 */
-	cfg80211_lock_rdev(rdev);
-	/* nothing */
-	cfg80211_unlock_rdev(rdev);
-
-	/*
 	 * If this device got a regulatory hint tell core its
 	 * free to listen now to a new shiny device regulatory hint
 	 */
@@ -705,7 +659,7 @@ void wiphy_unregister(struct wiphy *wiphy)
 	cfg80211_rdev_list_generation++;
 	device_del(&rdev->wiphy.dev);
 
-	mutex_unlock(&cfg80211_mutex);
+	rtnl_unlock();
 
 	flush_work(&rdev->scan_done_wk);
 	cancel_work_sync(&rdev->conn_work);
@@ -723,9 +677,6 @@ void cfg80211_dev_free(struct cfg80211_registered_device *rdev)
 	struct cfg80211_internal_bss *scan, *tmp;
 	struct cfg80211_beacon_registration *reg, *treg;
 	rfkill_destroy(rdev->rfkill);
-	mutex_destroy(&rdev->mtx);
-	mutex_destroy(&rdev->devlist_mtx);
-	mutex_destroy(&rdev->sched_scan_mtx);
 	list_for_each_entry_safe(reg, treg, &rdev->beacon_registrations, list) {
 		list_del(&reg->list);
 		kfree(reg);
@@ -750,36 +701,6 @@ void wiphy_rfkill_set_hw_state(struct wiphy *wiphy, bool blocked)
 }
 EXPORT_SYMBOL(wiphy_rfkill_set_hw_state);
 
-static void wdev_cleanup_work(struct work_struct *work)
-{
-	struct wireless_dev *wdev;
-	struct cfg80211_registered_device *rdev;
-
-	wdev = container_of(work, struct wireless_dev, cleanup_work);
-	rdev = wiphy_to_dev(wdev->wiphy);
-
-	mutex_lock(&rdev->sched_scan_mtx);
-
-	if (WARN_ON(rdev->scan_req && rdev->scan_req->wdev == wdev)) {
-		rdev->scan_req->aborted = true;
-		___cfg80211_scan_done(rdev, true);
-	}
-
-	if (WARN_ON(rdev->sched_scan_req &&
-		    rdev->sched_scan_req->dev == wdev->netdev)) {
-		__cfg80211_stop_sched_scan(rdev, false);
-	}
-
-	mutex_unlock(&rdev->sched_scan_mtx);
-
-	mutex_lock(&rdev->devlist_mtx);
-	rdev->opencount--;
-	mutex_unlock(&rdev->devlist_mtx);
-	wake_up(&rdev->dev_wait);
-
-	dev_put(wdev->netdev);
-}
-
 void cfg80211_unregister_wdev(struct wireless_dev *wdev)
 {
 	struct cfg80211_registered_device *rdev = wiphy_to_dev(wdev->wiphy);
@@ -789,8 +710,6 @@ void cfg80211_unregister_wdev(struct wireless_dev *wdev)
 	if (WARN_ON(wdev->netdev))
 		return;
 
-	mutex_lock(&rdev->devlist_mtx);
-	mutex_lock(&rdev->sched_scan_mtx);
 	list_del_rcu(&wdev->list);
 	rdev->devlist_generation++;
 
@@ -802,8 +721,6 @@ void cfg80211_unregister_wdev(struct wireless_dev *wdev)
 		WARN_ON_ONCE(1);
 		break;
 	}
-	mutex_unlock(&rdev->sched_scan_mtx);
-	mutex_unlock(&rdev->devlist_mtx);
 }
 EXPORT_SYMBOL(cfg80211_unregister_wdev);
 
@@ -822,7 +739,7 @@ void cfg80211_update_iface_num(struct cfg80211_registered_device *rdev,
 }
 
 void cfg80211_leave(struct cfg80211_registered_device *rdev,
-		   struct wireless_dev *wdev)
+		    struct wireless_dev *wdev)
 {
 	struct net_device *dev = wdev->netdev;
 
@@ -832,9 +749,7 @@ void cfg80211_leave(struct cfg80211_registered_device *rdev,
 		break;
 	case NL80211_IFTYPE_P2P_CLIENT:
 	case NL80211_IFTYPE_STATION:
-		mutex_lock(&rdev->sched_scan_mtx);
 		__cfg80211_stop_sched_scan(rdev, false);
-		mutex_unlock(&rdev->sched_scan_mtx);
 
 		wdev_lock(wdev);
 #ifdef CONFIG_CFG80211_WEXT
@@ -887,13 +802,11 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 		 * are added with nl80211.
 		 */
 		mutex_init(&wdev->mtx);
-		INIT_WORK(&wdev->cleanup_work, wdev_cleanup_work);
 		INIT_LIST_HEAD(&wdev->event_list);
 		spin_lock_init(&wdev->event_lock);
 		INIT_LIST_HEAD(&wdev->mgmt_registrations);
 		spin_lock_init(&wdev->mgmt_registrations_lock);
 
-		mutex_lock(&rdev->devlist_mtx);
 		wdev->identifier = ++rdev->wdev_id;
 		list_add_rcu(&wdev->list, &rdev->wdev_list);
 		rdev->devlist_generation++;
@@ -906,7 +819,6 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 		}
 		wdev->netdev = dev;
 		wdev->sme_state = CFG80211_SME_IDLE;
-		mutex_unlock(&rdev->devlist_mtx);
 #ifdef CONFIG_CFG80211_WEXT
 		wdev->wext.default_key = -1;
 		wdev->wext.default_mgmt_key = -1;
@@ -932,26 +844,22 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 		break;
 	case NETDEV_DOWN:
 		cfg80211_update_iface_num(rdev, wdev->iftype, -1);
-		dev_hold(dev);
-		queue_work(cfg80211_wq, &wdev->cleanup_work);
+		if (rdev->scan_req && rdev->scan_req->wdev == wdev) {
+			if (WARN_ON(!rdev->scan_req->notified))
+				rdev->scan_req->aborted = true;
+			___cfg80211_scan_done(rdev, true);
+		}
+
+		if (WARN_ON(rdev->sched_scan_req &&
+			    rdev->sched_scan_req->dev == wdev->netdev)) {
+			__cfg80211_stop_sched_scan(rdev, false);
+		}
+
+		rdev->opencount--;
+		wake_up(&rdev->dev_wait);
 		break;
 	case NETDEV_UP:
-		/*
-		 * If we have a really quick DOWN/UP succession we may
-		 * have this work still pending ... cancel it and see
-		 * if it was pending, in which case we need to account
-		 * for some of the work it would have done.
-		 */
-		if (cancel_work_sync(&wdev->cleanup_work)) {
-			mutex_lock(&rdev->devlist_mtx);
-			rdev->opencount--;
-			mutex_unlock(&rdev->devlist_mtx);
-			dev_put(dev);
-		}
 		cfg80211_update_iface_num(rdev, wdev->iftype, 1);
-		cfg80211_lock_rdev(rdev);
-		mutex_lock(&rdev->devlist_mtx);
-		mutex_lock(&rdev->sched_scan_mtx);
 		wdev_lock(wdev);
 		switch (wdev->iftype) {
 #ifdef CONFIG_CFG80211_WEXT
@@ -983,10 +891,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 			break;
 		}
 		wdev_unlock(wdev);
-		mutex_unlock(&rdev->sched_scan_mtx);
 		rdev->opencount++;
-		mutex_unlock(&rdev->devlist_mtx);
-		cfg80211_unlock_rdev(rdev);
 
 		/*
 		 * Configure power management to the driver here so that its
@@ -1003,12 +908,6 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 		break;
 	case NETDEV_UNREGISTER:
 		/*
-		 * NB: cannot take rdev->mtx here because this may be
-		 * called within code protected by it when interfaces
-		 * are removed with nl80211.
-		 */
-		mutex_lock(&rdev->devlist_mtx);
-		/*
 		 * It is possible to get NETDEV_UNREGISTER
 		 * multiple times. To detect that, check
 		 * that the interface is still on the list
@@ -1024,7 +923,6 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 			kfree(wdev->wext.keys);
 #endif
 		}
-		mutex_unlock(&rdev->devlist_mtx);
 		/*
 		 * synchronise (so that we won't find this netdev
 		 * from other code any more) and then clear the list
@@ -1044,9 +942,7 @@ static int cfg80211_netdev_notifier_call(struct notifier_block *nb,
 			return notifier_from_errno(-EOPNOTSUPP);
 		if (rfkill_blocked(rdev->rfkill))
 			return notifier_from_errno(-ERFKILL);
-		mutex_lock(&rdev->devlist_mtx);
 		ret = cfg80211_can_add_interface(rdev, wdev->iftype);
-		mutex_unlock(&rdev->devlist_mtx);
 		if (ret)
 			return notifier_from_errno(ret);
 		break;
@@ -1064,12 +960,10 @@ static void __net_exit cfg80211_pernet_exit(struct net *net)
 	struct cfg80211_registered_device *rdev;
 
 	rtnl_lock();
-	mutex_lock(&cfg80211_mutex);
 	list_for_each_entry(rdev, &cfg80211_rdev_list, list) {
 		if (net_eq(wiphy_net(&rdev->wiphy), net))
 			WARN_ON(cfg80211_switch_netns(rdev, &init_net));
 	}
-	mutex_unlock(&cfg80211_mutex);
 	rtnl_unlock();
 }