[B.A.T.M.A.N.] [PATCH 2/2] batman-adv: Avoid deadlock between rtnl_lock and s_active

[Sven Eckelmann <sven@narfation.org>]

The hard_if_event is called by the notifier with rtnl_lock and tries to
remove sysfs entries when a NETDEV_UNREGISTER event is received. This
will automatically take the s_active lock.

The s_active lock is also used when a new interface is added to a meshif
through sysfs. In that situation we cannot wait for the rntl_lock before
creating the actual batman-adv interface to prevent a deadlock. It is
still possible to try to get the rtnl_lock and immediately abort the
current operation when the trylock call failed.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
---
 bat_sysfs.c      |   13 ++++++++-----
 soft-interface.c |    2 +-
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/bat_sysfs.c b/bat_sysfs.c
index e449bf6..908ed5f 100644
--- a/bat_sysfs.c
+++ b/bat_sysfs.c
@@ -488,22 +488,25 @@ static ssize_t store_mesh_iface(struct kobject *kobj, struct attribute *attr,
 	    (strncmp(hard_iface->soft_iface->name, buff, IFNAMSIZ) == 0))
 		goto out;
 
+	if (!rtnl_trylock()) {
+		ret = -ERESTARTSYS;
+		goto out;
+	}
+
 	if (status_tmp == IF_NOT_IN_USE) {
-		rtnl_lock();
 		hardif_disable_interface(hard_iface);
-		rtnl_unlock();
-		goto out;
+		goto unlock;
 	}
 
 	/* if the interface already is in use */
 	if (hard_iface->if_status != IF_NOT_IN_USE) {
-		rtnl_lock();
 		hardif_disable_interface(hard_iface);
-		rtnl_unlock();
 	}
 
 	ret = hardif_enable_interface(hard_iface, buff);
 
+unlock:
+	rtnl_unlock();
 out:
 	hardif_free_ref(hard_iface);
 	return ret;
diff --git a/soft-interface.c b/soft-interface.c
index f4d80ad..bf53aa3 100644
--- a/soft-interface.c
+++ b/soft-interface.c
@@ -613,7 +613,7 @@ struct net_device *softif_create(char *name)
 		goto out;
 	}
 
-	ret = register_netdev(soft_iface);
+	ret = register_netdevice(soft_iface);
 	if (ret < 0) {
 		pr_err("Unable to register the batman interface '%s': %i\n",
 		       name, ret);
-- 
1.7.4.4