Re: [PATCH 6/6] cfg80211: move regulatory hints to workqueue

[Johannes Berg <johannes@sipsolutions.net>]

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On Thu, 2009-02-12 at 23:35 -0800, Luis R. Rodriguez wrote:

> > Well, regardless of regulatory, we now have two paths:
> >
> > nl80211: cfg80211_mutex  -->  drv->mutex  -->  rtnl
> > wext:    rtnl  -->  cfg80211_mutex  -->  drv->mutex
> >
> > which is clearly not a good plan.
> >
> > Therefore, I'll probably have to implement solution (1) from what I sent
> > you, and invert the locking in nl80211. That would fix your the
> > immediate problem with regulatory as well, because that was:
> >
> > rtnl  --->  (regulatory_hint) --->  cfg80211_mutex  -->  drv->mutex
> 
> Yup I see. So as it stands in this patch user reg hint now is:
> 
> reg_mutex --> cfg80211_mutex

I don't really care about reg_mutex much, and it probably doesn't matter
as long as its use is limited. Question is whether we need it, but
that's a different question.

> Driver hint also does the same so it seems your fix on nl80211 would
> probably just tap this series on the nl80211_req_set_reg().

Yeah, I think I'll work on top of your series anyway so I don't clash
with the cleanups.

> I also think using a workqueue would be good here anyway, the only
> negative thing I've seen is loading takes a bit longer.

Indeed, it's a good thing because a path like this:

driver_open
 -> regulatory_hint
  -> cfg80211 stuff
   -> driver_reg_notifier

is always deadlock prone since you call into the driver from itself.

johannes

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