Re: [RFC/T][PATCH 1/3] rc80211-pid: introduce rate behaviour learning algorithm

[Stefano Brivio <stefano.brivio@polimi.it>]

On Sun, 09 Dec 2007 23:25:50 +0100
Mattias Nissler <mattias.nissler@gmx.de> wrote:

> >  static void *rate_control_pid_alloc(struct ieee80211_local *local)
> >  {
> >  	struct rc_pid_info *pinfo;
> > +	struct rc_pid_rateinfo *rinfo;
> > +	struct ieee80211_hw_mode *mode;
> > +	int i, j, tmp;
> > +	bool s;
> >  
> >  	pinfo = kmalloc(sizeof(*pinfo), GFP_ATOMIC);
> > +	if (!pinfo)
> > +		return NULL;
> > +
> > +	mode = local->oper_hw_mode;
> > +	rinfo = kmalloc(sizeof(*rinfo) * mode->num_rates, GFP_ATOMIC);
> > +	if (!rinfo) {
> > +		kfree(pinfo);
> > +		return NULL;
> > +	}
> 
> What if the mode is changed? Have you checked the rate control algorithm
> gets reinitialized? If not, we're scheduling a crash here, when
> mode->num_rates changes.

After a discussion on IRC with Michael (Wu), we came to the conclusion that
it doesn't make sense for mode->num_rates to change, because:
1) if the AP drops supported rates, it'll drop the association as well,
then everything here will be destroyed and created again;
2) that can be changed in userspace, but we couldn't figure out a scenario
where it would make any sense. Johannes, any comments? Wouldn't it make
sense to just forbid to change this in userspace?


--
Ciao
Stefano