[PATCH net-next] net: devlink: remove redundant rtnl lock assert

[PATCH net-next] net: devlink: remove redundant rtnl lock assert

[Vlad Buslov]

It is enough for caller of devlink_compat_switch_id_get() to hold the net
device to guarantee that devlink port is not destroyed concurrently. Remove
rtnl lock assertion and modify comment to warn user that they must hold
either rtnl lock or reference to net device. This is necessary to
accommodate future implementation of rtnl-unlocked TC offloads driver
callbacks.

Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
---
 net/core/devlink.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/core/devlink.c b/net/core/devlink.c
index e8f0b891f000..e98e7bd9740b 100644
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -6938,11 +6938,10 @@ int devlink_compat_switch_id_get(struct net_device *dev,
 {
 	struct devlink_port *devlink_port;
 
-	/* RTNL mutex is held here which ensures that devlink_port
-	 * instance cannot disappear in the middle. No need to take
+	/* Caller must hold RTNL mutex or reference to dev, which ensures that
+	 * devlink_port instance cannot disappear in the middle. No need to take
 	 * any devlink lock as only permanent values are accessed.
 	 */
-	ASSERT_RTNL();
 	devlink_port = netdev_to_devlink_port(dev);
 	if (!devlink_port || !devlink_port->attrs.switch_port)
 		return -EOPNOTSUPP;
-- 
2.21.0

Re: [PATCH net-next] net: devlink: remove redundant rtnl lock assert

[Jakub Kicinski]

On Mon, 12 Aug 2019 20:02:02 +0300, Vlad Buslov wrote:
> It is enough for caller of devlink_compat_switch_id_get() to hold the net
> device to guarantee that devlink port is not destroyed concurrently. Remove
> rtnl lock assertion and modify comment to warn user that they must hold
> either rtnl lock or reference to net device. This is necessary to
> accommodate future implementation of rtnl-unlocked TC offloads driver
> callbacks.
> 
> Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
> Acked-by: Jiri Pirko <jiri@mellanox.com>

Looks good, applied.