Re: [PATCH 1/5] ath9k_htc: Lock sta_notify() callback

[<Sujith.Manoharan@atheros.com>]

Johannes Berg wrote:
> On Tue, 2010-05-11 at 16:24 +0530, Sujith.Manoharan@atheros.com wrote:
> > Since ->sta_notify() can sleep, protect
> > the callback with a mutex.
> 
> While this may be a correct change, it's not a correct description :)
> 
> You should be locking _data_, not _code_, and due to mac80211 the
> callback cannot be invoked twice at the same time anyway.

It protects all the binary data between lock and unlock. :-)

I encountered a problem with sta_notify() with a script doing
a load/scan/connect/unload cycle and NetworkManager also running,
doing its own scan/connect processing. And at some point,
ath9k_htc_remove_station() failed. Which led me to suspect overlapping
calls to sta_notify().

I do see sta_mtx being taken at all the places where sta_remove() is called
in mac80211, so am not sure how I managed to hit it.

Sujith