netdev - Re: [PATCH take 2] pkt_sched: Fix qdisc_watchdog() vs. dev

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Message-ID: <20080913205408.GA2545@ami.dom.local>
Date:	Sat, 13 Sep 2008 22:54:08 +0200
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	kaber@...sh.net
Subject: Re: [PATCH take 2] pkt_sched: Fix qdisc_watchdog() vs.
	dev_deactivate() race

On Fri, Sep 12, 2008 at 06:48:00PM -0700, Herbert Xu wrote:
> On Fri, Sep 12, 2008 at 06:40:08PM -0700, David Miller wrote:
> >
> > My current opinion is that both operations are equally difficult.
> > With the slight advantage for ->requeue() because all the complicated
> > logic is already implemented :-)
> 
> I'd agree with you if you haven't written the peek stuff :)
> 
> Now that peek exists, the dequeue stuff would be a lot simpler
> than requeue because the only non-trivial logic would be in the
> leaf qdiscs.  All the complex/classful qdiscs would be trivial
> as they'd just write down the child qdisc that was peeked and
> then call dequeue on that child.

If I get it right peek + dequeue should do all current dequeue logic
plus additionally write down the child qdisc or skb (leaves) info,
plus, probably, some ifs btw., which looks like a bit of overhead,
if we consider requeuing as something exceptional. Unless we don't -
then of course something like this could be useful.

Jarek P.
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