question for mac80211 driver maintainers - RCU usage in drivers

[Johannes Berg <johannes@sipsolutions.net>]

Hi all,

Except for iwlmvm, I don't find much RCU usage wrt. stations in drivers.

Is there any other driver that assumes it is safe to delete a station
pointer in the sta_state callback and not use synchronize_rcu()? From
looking at the code, I don't see any, but I can't really be sure that
everyone uses __rcu annotations correctly ... :)

Would anyone object if we changed mac80211 to *immediately* free the
station after calling the driver's sta_state (or sta_remove) callback?
We currently delay this until after an RCU grace period, but that way we
end up having a lot of delay in station freeing ... We'd like to
optimise that.

johannes

PS: I'll probably have to add another callback "sta going away before
RCU" so you can invalidate pointers there ... otherwise I'd have to
synchronize_rcu() in iwlmvm which would kinda defeat the purpose.