From: Vladimir Oltean <olteanv@xxxxxxxxx> Date: Wed, 10 Feb 2021 11:14:41 +0200 > From: Vladimir Oltean <vladimir.oltean@xxxxxxx> > > 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. > > The issue is that the brport flags are a single unsigned long bitmask, > and the bridge only guarantees the validity of the changed bits, not the > full state. So when offloading two concurrent switchdev attributes, such > as one for BR_LEARNING and another for BR_FLOOD, it might happen that > the flags having BR_FLOOD are written into the cached value, and this in > turn disables the BR_LEARNING bit which was set previously. > > We can fix this across the board by keeping individual boolean variables > for each brport flag. Note that mlxsw and prestera were setting the > BR_LEARNING_SYNC flag too, but that appears to be just dead code, so I > removed it. > > Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx> This needs updating because, as discussed, there is no race.
