Re: [PATCH 3/3] mac80211: make csa_currnet_counter atomic

[Johannes Berg <johannes@sipsolutions.net>]

typo in subject.

On Thu, 2014-05-22 at 15:28 +0200, Michal Kazior wrote:
> Even it ieee80211_beacon_get() and
> ieee80211_csa_update_counter() were to be
> guaranteed to be serialized by drivers it still
> couldn't be guaranteed to be safe on SMP systems.

We had this debate internally as well, but I don't see where issues
should be. The only place updating the counter is
ieee80211_csa_update_counter(), and that should only be called either by
the driver, or by ieee80211_beacon_get[_tim]() [*]. If the driver wants
to have the counter update by ieee80211_beacon_get() then it must call
the function once every beacon interval, if it uses the _template()
version then it must call ieee80211_csa_update_counter() every beacon
interval, so no races seem possible.

johannes

[*] the driver shouldn't call ieee80211_beacon_get[_tim] and
ieee80211_csa_update_counter() in a mixed fashion anyway as that'd lead
to CSA counter bugs, and ieee80211_beacon_get_template() doesn't change
the counter