netdev - Re: [PATCH net v1] net/sched: Don't print dump stack in event of transmission timeout

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Date:   Mon, 13 Apr 2020 13:20:53 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Jose Abreu <Jose.Abreu@...opsys.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net v1] net/sched: Don't print dump stack in event of
 transmission timeout

On Mon, Apr 13, 2020 at 09:01:32AM +0000, Jose Abreu wrote:
> From: Leon Romanovsky <leon@...nel.org>
> Date: Apr/12/2020, 07:08:54 (UTC+00:00)
>
> > [  281.170584] ------------[ cut here ]------------
>
> Not objecting to the patch it-self (because usually stack trace is
> useless), but just FYI we use this marker in our CI to track for timeouts
> or crashes. I'm not sure if anyone else is using it.

I didn't delete the "NETDEV WATCHDOG .." message and it will be still
visible as a marker.

>
> And actually, can you please explain why BQL is not suppressing your
> timeouts ?

Driver can't distinguish between "real" timeout and "mixed traffic" timeout,
so we don't want to completely disable "dev->netdev_ops->ndo_tx_timeout(dev, i);"
call in watchdog [1]. The goal is to leave functionality in place and
simply remove stack trace to be similar to other BUG prints in that file [2].

[1] https://elixir.bootlin.com/linux/latest/source/net/sched/sch_generic.c#L444
[2] https://elixir.bootlin.com/linux/latest/source/net/sched/sch_generic.c#L328

>
> ---
> Thanks,
> Jose Miguel Abreu