Hi Nik, Thanks for the review. Sounds reasonable to me and I will look into it.
Julius Am So., 4. Okt. 2026 um 13:44 Uhr schrieb Nikolay Aleksandrov <[email protected]>: > > On 04/10/2026 15:42, Julius Bairaktaris wrote: > > br_fdb_update() lets an entry roam to a new port without holding > > hash_lock. It notifies switchdev that the entry left the old port, > > writes the new port, then notifies the addition. When two CPUs receive > > the same source address on different ports, these steps interleave: a > > driver sees two deletions for one addition, or an addition for the port > > the other CPU wrote. > > > > DSA counts references to a host address on the CPU port. The extra > > deletion fails and the extra addition is never released: > > > > qca-ppe 3a000000.ppe: port 5 failed to delete 02:5a:0b:a2:1a:46 vid 0 > > from fdb: -2 > > > > With one address roaming between a DSA user port and a Wi-Fi AP port of > > the same bridge, the error appears 3-6 times per address when the two > > ports receive on different CPUs, and not at all when they share one CPU > > (4 runs each). With this change it does not appear (6 runs, different > > CPUs). > > > > Take hash_lock when the entry roams or its flags change, and send both > > notifications under it. The common case, where the entry neither roams > > nor changes, stays lockless. > > > > Fixes: 90dc8fd36078 ("net: bridge: notify switchdev of disappearance of old > > FDB entry upon migration") > > Assisted-by: Claude:claude-opus-5-5 > > Signed-off-by: Julius Bairaktaris <[email protected]> > > --- > > > > Notes: > > net-next 941056f91907 ("net: bridge: fdb: factor out existing entry > > updates") > > moves this code into __fdb_update(); the same change applies there. > > > > net/bridge/br_fdb.c | 14 ++++++++++++-- > > 1 file changed, 12 insertions(+), 2 deletions(-) > > > > Absolutely not, this was made intentionally. Taking the hash_lock would > further kill learning > and roaming scaling. Surely switchdev drivers must have dealt with this for > some time > now, if you'd like to fix it do it so the software path isn't affected. > > Cheers, > Nik > > >
