netdev - Re: [PATCH] NET: Fix sch_prio to detect the root qdisc loading

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Date:	Sun, 22 Jul 2007 18:32:32 +0200
From:	Patrick McHardy <kaber@...sh.net>
To:	PJ Waskiewicz <peter.p.waskiewicz.jr@...el.com>
CC:	davem@...emloft.net, netdev@...r.kernel.org, jeff@...zik.org
Subject: Re: [PATCH] NET: Fix sch_prio to detect the root qdisc loading

PJ Waskiewicz wrote:
> The sch->parent handle will be NULL for the scheduler that is TC_H_ROOT.
> Change this check in prio_tune() so that only the root qdisc can be
> multiqueue-enabled.
> 
> Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>
> ---
> 
>  net/sched/sch_prio.c |    6 ++++--
>  1 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/sched/sch_prio.c b/net/sched/sch_prio.c
> index 2d8c084..271051e 100644
> --- a/net/sched/sch_prio.c
> +++ b/net/sched/sch_prio.c
> @@ -239,11 +239,13 @@ static int prio_tune(struct Qdisc *sch, struct rtattr *opt)
>  	/* If we're multiqueue, make sure the number of incoming bands
>  	 * matches the number of queues on the device we're associating with.
>  	 * If the number of bands requested is zero, then set q->bands to
> -	 * dev->egress_subqueue_count.
> +	 * dev->egress_subqueue_count.  Also, the root qdisc must be the
> +	 * only one that is enabled for multiqueue, since it's the only one
> +	 * that interacts with the underlying device.
>  	 */
>  	q->mq = RTA_GET_FLAG(tb[TCA_PRIO_MQ - 1]);
>  	if (q->mq) {
> -		if (sch->handle != TC_H_ROOT)
> +		if (sch->parent != NULL)


As explained in my last mail, sch->parent is an integer. And it is
set when grafting the qdisc, not on initilization, so it is always
0 here when coming from prio_init.

This untested patch should make sure its always set correctly.

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