[ovs-dev] [PATCH] datapath: Don't hold dp_mutex when setting internal devs MTU.

[Jesse Gross]

We currently acquire dp_mutex when we are notified that the MTU
of a device attached to the datapath has changed so that we can
set the internal devices to the minimum MTU.  However, it is not
required to hold dp_mutex because we already have RTNL lock and it
causes a deadlock, so don't do it.
---
 datapath/datapath.c           |    5 ++---
 datapath/dp_notify.c          |    5 +----
 datapath/vport-internal_dev.c |    8 +-------
 3 files changed, 4 insertions(+), 14 deletions(-)

diff --git a/datapath/datapath.c b/datapath/datapath.c
index e1320f2..93a720a 100644
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -423,8 +423,7 @@ got_port_no:
 	if (err)
 		goto out_unlock_dp;
 
-	if (!(port.flags & ODP_PORT_INTERNAL))
-		set_internal_devs_mtu(dp);
+	set_internal_devs_mtu(dp);
 	dp_sysfs_add_if(dp->ports[port_no]);
 
 	err = __put_user(port_no, &portp->port);
@@ -1366,7 +1365,7 @@ int dp_min_mtu(const struct datapath *dp)
 }
 
 /* Sets the MTU of all datapath devices to the minimum of the ports.  Must
- * be called with RTNL lock and dp_mutex. */
+ * be called with RTNL lock. */
 void set_internal_devs_mtu(const struct datapath *dp)
 {
 	struct dp_port *p;
diff --git a/datapath/dp_notify.c b/datapath/dp_notify.c
index 4a16a93..e73a731 100644
--- a/datapath/dp_notify.c
+++ b/datapath/dp_notify.c
@@ -54,11 +54,8 @@ static int dp_device_event(struct notifier_block *unused, unsigned long event,
 		break;
 
 	case NETDEV_CHANGEMTU:
-		if (!is_internal_dev(dev)) {
-			mutex_lock(&dp->mutex);
+		if (!is_internal_dev(dev))
 			set_internal_devs_mtu(dp);
-			mutex_unlock(&dp->mutex);
-		}
 		break;
 	}
 	return NOTIFY_DONE;
diff --git a/datapath/vport-internal_dev.c b/datapath/vport-internal_dev.c
index 39283e0..88b6cc1 100644
--- a/datapath/vport-internal_dev.c
+++ b/datapath/vport-internal_dev.c
@@ -144,13 +144,7 @@ static int internal_dev_change_mtu(struct net_device *netdev, int new_mtu)
 		return -EINVAL;
 
 	if (dp_port) {
-		int min_mtu;
-
-		mutex_lock(&dp_port->dp->mutex);
-		min_mtu = dp_min_mtu(dp_port->dp);
-		mutex_unlock(&dp_port->dp->mutex);
-
-		if (new_mtu > min_mtu)
+		if (new_mtu > dp_min_mtu(dp_port->dp))
 			return -EINVAL;
 	}
 
-- 
1.6.3.3