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

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Date:   Fri, 3 Apr 2020 07:36:11 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        itayav@...lanox.com
Subject: Re: [PATCH net] net/sched: Don't print dump stack in event of
 transmission timeout

On Thu, Apr 02, 2020 at 09:30:15PM -0700, Cong Wang wrote:
> On Thu, Apr 2, 2020 at 6:02 PM David Miller <davem@...emloft.net> wrote:
> >
> > From: Leon Romanovsky <leon@...nel.org>
> > Date: Thu,  2 Apr 2020 18:23:36 +0300
> >
> > > In event of transmission timeout, the drivers are given an opportunity
> > > to recover and continue to work after some in-house cleanups.
> > >
> > > Such event can be caused by HW bugs, wrong congestion configurations
> > > and many more other scenarios. In such case, users are interested to
> > > get a simple  "NETDEV WATCHDOG ... " print, which points to the relevant
> > > netdevice in trouble.
> > >
> > > The dump stack printed later was added in the commit b4192bbd85d2
> > > ("net: Add a WARN_ON_ONCE() to the transmit timeout function") to give
> > > extra information, like list of the modules and which driver is involved.
> > >
> > > While the latter is already printed in "NETDEV WATCHDOG ... ", the list
> > > of modules rarely needed and can be collected later.
> > >
> > > So let's remove the WARN_ONCE() and make dmesg look more user-friendly in
> > > large cluster setups.
> >
> > Software bugs play into these situations and on at least two or three
> > occasions I know that the backtrace hinted at the cause of the bug.
> >
>
> I don't see how a timer stack trace could help to debug this issue
> in any scenario, the messages out of this stack trace are indeed
> helpful.
>
> On the other hand, a stack trace does help to get some attention
> via ABRT, but at least for us we now use rasdaemon to capture
> this, so I am 100% fine to remove this stack trace.

Thanks

>
> Thanks.