[RFC PATCH 00/12] wifi: AP side locking improvements

[Johannes Berg <johannes@sipsolutions.net>]

This obviously goes on top of my (fixed) RTNL redux series.

The idea here is that wiphy mutex can be held for quite a bit
of time (e.g. waiting for firmware), but beacon updates (e.g.
with the critical update design I had proposed a long while
back) and other things should be fast.

So with this not all things require wiphy mutex. These are:

 - beacon and related template updates
   (this one needs driver opt-in),
 - mgmt frame TX,
 - control port TX, and
 - peer probe.

This does make the implementation slightly more complex, but
the added complexity is almost entirely in mac80211 (and some
in cfg80211), unless a driver wants to opt in to unlocked
beacon/template updates, which it has to implement itself for
obvious reasons.

I think we probably want this even without the critical update
design we're still debating, but I thought I'd throw this out
here because a lot of the discussion has been focused on the
latencies throughout the stack, and I never thought they were
fundamental. QED ;-)

johannes