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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Mon, 24 Feb 2020 11:01:09 +0100
Message-ID: <CAMuHMdViacgi1W8acma7GhWaaVj92z6pg-g7ByvYOQL-DToacA@mail.gmail.com>
Subject: Re: [GIT] Networking
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     David Miller <davem@davemloft.net>,
        Doug Ledford <dledford@redhat.com>,
        Ira Weiny <ira.weiny@intel.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Network Development <netdev@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Greg KH <gregkh@linuxfoundation.org>
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Hi Linus,

On Thu, Jun 25, 2015 at 1:38 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
> On Wed, Jun 24, 2015 at 6:39 AM, David Miller <davem@davemloft.net> wrote:
> >   git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git master
>
> On the *other* side of the same conflict, I find an even more
> offensive commit, namely commit 4cd7c9479aff ("IB/mad: Add support for
> additional MAD info to/from drivers") which adds a BUG_ON() for a
> sanity check, rather than just returning -EINVAL or something sane
> like that.
>
> I'm getting *real* tired of that BUG_ON() shit. I realize that
> infiniband is a niche market, and those "commercial grade" niche
> markets are more-than-used-to crap code and horrible hacks, but this
> is still the kernel. We don't add random machine-killing debug checks
> when it is *so* simple to just do
>
>         if (WARN_ON_ONCE(..))
>                 return -EINVAL;
>
> instead.

And if we follow that advice, friendly Greg will respond with:
"We really do not want WARN_ON() anywhere, as that causes systems with
 panic-on-warn to reboot."
https://lore.kernel.org/lkml/20191121135743.GA552517@kroah.com/

> Killing the machine for idiotic things like that is truly offensive,
> and truly horrible horrible code. Why do I keep on having to tell
> people off for doing these things? Why do people keep thinking that
> debugging-by-killing-the-machine is a good idea?
>
> Either that BUG_ON() cannot possibly happen, in which case it should
> damn well not exist in the first place. Or it's a valuable debug aid,
> in which case it should damn well not be a BUG_ON. You can't have it
> both ways.

Agreed.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds