Subject: Re: [PATCH][NET_SCHED] sch_api: fix qdisc_tree_decrease_qlen() loop

From: Jarek Poplawski <[email-masked]>
Date: Tue, 15 Apr 2008 21:29:24 +0200

On Tue, Apr 15, 2008 at 08:25:41PM +0200, Jarek Poplawski wrote:
> On Tue, Apr 15, 2008 at 07:41:44PM +0200, Jarek Poplawski wrote:
> > On Tue, Apr 15, 2008 at 03:09:53PM +0200, Patrick McHardy wrote:
...
> > > diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
> > > index fc8708a..c486e9d 100644
> > > --- a/net/sched/sch_api.c
> > > +++ b/net/sched/sch_api.c
> > > @@ -386,7 +386,7 @@ void qdisc_tree_decrease_qlen(struct Qdisc *sch, unsigned int n)
> > >  	if (n == 0)
> > >  		return;
> > >  	while ((parentid = sch->parent)) {
> > > -		if (TC_H_MAJ(parentid) == TC_H_MAJ(TC_H_INGRESS))
> > > +		if (parentid == TC_H_INGRESS)
> > 
> > Maybe like this?:
> >  +		if (parentid == TC_H_ROOT || parentid == TC_H_INGRESS)
> 
> Still wrong! Rather this:
> 
>   	while ((parentid = sch->parent)) {
>   		if (parentid == TC_H_ROOT)
>   			return;

...Hmm... it seems to be enough?! (At least with current ingress
functionality.)

> 
>   		sch = qdisc_lookup(sch->dev, TC_H_MAJ(parentid));
> 		if (!sch || sch->parentid == TC_H_INGRESS) {
> 			...

...and here WARN_ON() instead of if (): root is never looked up, so we
can't get NULL nor ingress here; if we have non-ingress ffff:0000
we'll get it (and ingress can't co-exist).

Jarek P.