Re: [PATCH v3 net-next 07/11] net: prep switchdev drivers for concurrent SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS

Vladimir Oltean
2021-02-10T10:36:12Z

On Wed, Feb 10, 2021 at 12:12:57PM +0200, Ido Schimmel wrote:
> On Wed, Feb 10, 2021 at 11:14:41AM +0200, Vladimir Oltean wrote:
> > From: Vladimir Oltean <vladimir.oltean@nxp.com>
> >
> > Because the bridge will start offloading SWITCHDEV_ATTR_ID_PORT_BRIDGE_FLAGS
> > while not serialized by any lock such as the br->lock spinlock, existing
> > drivers that treat that attribute and cache the brport flags might no
> > longer work correctly.
>
> Can you explain the race? This notification is sent from sysfs/netlink
> call path, both of which take rtnl.

Replying here to both you and Nikolay: there isn't any race, sorry, I
missed the fact that brport_store takes the rtnl_mutex and by extension
I thought that RTM_SETLINK runs unlocked too, without really checking.
Well, at least that's good news, the implementation can be a lot more
straightforward then...