Re: [PATCH v3 net-next 08/12] net: dsa: replay port and host-joined mdb entries when joining the bridge
From: Vladimir Oltean <olteanv@gmail.com>
Date: 2021-03-22 16:56:56
Also in:
linux-omap, lkml
On Mon, Mar 22, 2021 at 06:35:10PM +0200, Nikolay Aleksandrov wrote:
quoted
+ hlist_for_each_entry(mp, &br->mdb_list, mdb_node) {You cannot walk over these lists without the multicast lock or RCU. RTNL is not enough because of various timers and leave messages that can alter both the mdb_list and the port group lists. I'd prefer RCU to avoid blocking the bridge mcast.
The trouble is that I need to emulate the calling context that is provided to SWITCHDEV_OBJ_ID_HOST_MDB and SWITCHDEV_OBJ_ID_PORT_MDB, and that means blocking context. So if I hold rcu_read_lock(), I need to queue up the mdb entries, and notify the driver only after I leave the RCU critical section. The memory footprint may temporarily blow up. In fact this is what I did in v1: https://patchwork.kernel.org/project/netdevbpf/patch/20210224114350.2791260-15-olteanv@gmail.com/ I just figured I could get away with rtnl_mutex protection, but it looks like I can't. So I guess you prefer my v1?