netdev - Re: [PATCH] net_sched: prio: use qdisc_dequeue

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Message-ID: <1312894585.2371.24.camel@edumazet-HP-Compaq-6005-Pro-SFF-PC>
Date:	Tue, 09 Aug 2011 14:56:25 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Florian Westphal <fw@...len.de>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] net_sched: prio: use qdisc_dequeue_peeked

Le mardi 09 août 2011 à 14:04 +0200, Florian Westphal a écrit :
> commit 07bd8df5df4369487812bf85a237322ff3569b77
> (sch_sfq: fix peek() implementation) changed sfq to use generic
> peek helper.
> 
> This makes HFSC complain about a non-work-conserving child qdisc, if
> prio with sfq child is used within hfsc:
> 
> hfsc peeks into prio qdisc, which will then peek into sfq.
> returned skb is stashed in sch->gso_skb.
> 
> Next, hfsc tries to dequeue from prio, but prio will call sfq dequeue
> directly, which may return NULL instead of previously peeked-at skb.
> 
> Have prio call qdisc_dequeue_peeked, so sfq->dequeue() is
> not called in this case.
> 
> Cc: Eric Dumazet <eric.dumazet@...il.com>
> Signed-off-by: Florian Westphal <fw@...len.de>
> ---
>  Eric, does this look correct to you?
>  I am not sure if sfq needs fixing instead of this patch here.
> 
> diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
> index 2a318f2..b5d56a2 100644
> --- a/net/sched/sch_prio.c
> +++ b/net/sched/sch_prio.c
> @@ -112,7 +112,7 @@ static struct sk_buff *prio_dequeue(struct Qdisc *sch)
>  
>  	for (prio = 0; prio < q->bands; prio++) {
>  		struct Qdisc *qdisc = q->queues[prio];
> -		struct sk_buff *skb = qdisc->dequeue(qdisc);
> +		struct sk_buff *skb = qdisc_dequeue_peeked(qdisc);
>  		if (skb) {
>  			qdisc_bstats_update(sch, skb);
>  			sch->q.qlen--;


Hi Florian

Are you sure this patch is still needed, after commit 
e1738bd9cecc5c867b0e2996470c1ff20f66ba79
(sch_sfq: fix sfq_enqueue())

I am asking before fully reviewing the code, I dont know who
should/shouldnt call qdisc_dequeue_peeked() instead of qdisc->dequeue()

Thanks !






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