linux-kernel - Re: [PATCH 2/2] net: sched: convert qdisc linked list to hashtable

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Date:	Fri, 12 Aug 2016 16:36:01 +0200 (CEST)
From:	Jiri Kosina <jikos@...nel.org>
To:	Daniel Borkmann <daniel@...earbox.net>
cc:	Eric Dumazet <eric.dumazet@...il.com>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Phil Sutter <phil@....cc>,
	Cong Wang <xiyou.wangcong@...il.com>,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] net: sched: convert qdisc linked list to hashtable

On Fri, 12 Aug 2016, Daniel Borkmann wrote:

> > I was thinking about something like the patch below (the reasong being 
> > that ->dev would be NULL only in cases of singletonish qdiscs) ... 
> > wouldn't that also fix the issue you're seeing? Have to think it 
> > through a little bit more ..
> 
> Ahh, so this has the same effect as previously observed with the other fix.

Thanks a lot for confirming that this fixes the panic. I still have to 
think a little bit more about this though.

> Perhaps it's just a dumping issue, but to the below clsact, there shouldn't
> be pfifo_fast instances appearing.
> 
> # tc qdisc show dev wlp2s0b1
> qdisc mq 0: root
> qdisc pfifo_fast 0: parent :4 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> qdisc pfifo_fast 0: parent :3 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> qdisc pfifo_fast 0: parent :2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> qdisc pfifo_fast 0: parent :1 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> # tc qdisc add dev wlp2s0b1 clsact
> # tc qdisc show dev wlp2s0b1
> qdisc mq 0: root
> qdisc pfifo_fast 0: parent :4 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> qdisc pfifo_fast 0: parent :3 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> qdisc pfifo_fast 0: parent :2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> qdisc pfifo_fast 0: parent :1 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> qdisc clsact ffff: parent ffff:fff1
> qdisc pfifo_fast 0: parent :4 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> qdisc pfifo_fast 0: parent :3 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> qdisc pfifo_fast 0: parent :2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
> qdisc pfifo_fast 0: parent :1 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1

Hmm, no immediate idea where those are coming from, we'll have to figure 
it out. The mq device used here has 4 queues, right?

-- 
Jiri Kosina
SUSE Labs