Re: Latest wireless-testing has broken scan locking.

[Johannes Berg <johannes@sipsolutions.net>]

On Thu, 2010-10-07 at 11:18 +0200, Stanislaw Gruszka wrote:

> > --- wireless-testing.orig/net/mac80211/scan.c	2010-10-07 10:27:37.000000000 +0200
> > +++ wireless-testing/net/mac80211/scan.c	2010-10-07 10:31:19.000000000 +0200
> > @@ -693,8 +693,6 @@ void ieee80211_scan_work(struct work_str
> >  		goto out_complete;
> >  	}
> >  
> > -	mutex_unlock(&local->mtx);
> > -
> >  	/*
> >  	 * as long as no delay is required advance immediately
> >  	 * without scheduling a new work
> > @@ -725,6 +723,7 @@ void ieee80211_scan_work(struct work_str
> >  	} while (next_delay == 0);
> >  
> >  	ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay);
> > +	mutex_unlock(&local->mtx);
> >  	return;
> >  
> >  out_complete:
> 
> We never keep locking inside do { } while (next_delay == 0) loop,
> perhaps below patch is something better:

Yeah, we didn't have that before, but weren't you yourself arguing that
dropping and re-acquiring could lead to issues? :)

FWIW, I've looked at the code and all we do is possibly acquire the
iflist_mtx (which is fine under local->mtx) and do some driver calls,
which should also be fine.

So what do you think?

johannes