netdev - Re: [PATCH net v3] net/sched: cbs: Fix not adding cbs instance to list

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Date:   Tue, 24 Sep 2019 18:12:41 +0000
From:   "Guedes, Andre" <andre.guedes@...el.com>
To:     "Gomes, Vinicius" <vinicius.gomes@...el.com>
CC:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        "jhs@...atatu.com" <jhs@...atatu.com>,
        "xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
        "jiri@...nulli.us" <jiri@...nulli.us>,
        "davem@...emloft.net" <davem@...emloft.net>
Subject: Re: [PATCH net v3] net/sched: cbs: Fix not adding cbs instance to
 list

Hi Vinicius,

> On Sep 23, 2019, at 10:04 PM, Vinicius Costa Gomes <vinicius.gomes@...el.com> wrote:
> 
> The problem happens because that when offloading is enabled, the cbs
> instance is not added to the list.
> 
> Also, the current code doesn't handle correctly the case when offload
> is disabled without removing the qdisc: if the link speed changes the
> credit calculations will be wrong. When we create the cbs instance
> with offloading enabled, it's not added to the notification list, when
> later we disable offloading, it's not in the list, so link speed
> changes will not affect it.
> 
> The solution for both issues is the same, add the cbs instance being
> created unconditionally to the global list, even if the link state
> notification isn't useful "right now".

I believe we could fix both issues described above and still don’t notify the qdisc about link state if we handled the list insertion/removal in cbs_change() instead.

Reading the cbs code more carefully, it seems it would be beneficial to refactor the offload handling. For example, we currently init the qdisc_watchdog even if it’s not useful when offload is enabled. Now, we’re going to notify the qdisc even if it’s not useful too.

Regards,

Andre