netdev - Re: [PATCH net-next 4/8] net: use DEBUG_NET_WARN_ON_ONCE() in sk_stream_kill

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Date:   Wed, 08 Jun 2022 10:11:02 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <eric.dumazet@...il.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH net-next 4/8] net: use DEBUG_NET_WARN_ON_ONCE() in
 sk_stream_kill_queues()

On Tue, 2022-06-07 at 21:10 -0700, Jakub Kicinski wrote:
> On Tue,  7 Jun 2022 10:17:28 -0700 Eric Dumazet wrote:
> > sk_stream_kill_queues() has three checks which have been
> > useful to detect kernel bugs in the past.
> > 
> > However they are potentially a problem because they
> > could flood the syslog, and really only a developper
> > can make sense of them.
> > 
> > Keep the checks for CONFIG_DEBUG_NET=y builds,
> > and issue them once only.
> 
> I feel like 3 & 4 had caught plenty of bugs which triggered only 
> in production / at scale. 
> 
I have a somewhat similar experience: I hit a few races spotted by the
warnings in patches 3 and 4 observable only in non-debug build.

The checks in patch 4 are almost rendundant with the ones in patch 3 -
at least in my experience I could not trigger the first without hitting
the latter. Perhaps we could use WARN_ON_ONCE only in patch 3?

Thanks!

Paolo