linux-kernel - Re: [PATCH v3] Add kernel config option for tweaking kernel behavior.

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Message-ID: <20200414214301.126ada20@oasis.local.home>
Date:   Tue, 14 Apr 2020 21:43:01 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Garrett <mjg59@...gle.com>,
        Andi Kleen <ak@...ux.intel.com>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Arnd Bergmann <arnd@...db.de>, Jiri Slaby <jslaby@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] Add kernel config option for tweaking kernel
 behavior.

On Tue, 14 Apr 2020 18:14:51 -0700
Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> If that WARN_ON() is a problem, then the people behind it should be
> appraised of it, and it should probably be removed. I'm assuming it
> was some kind of "I don't think this can happen, so if it does, I want
> to see how it happened" WARN_ON.

What I do (and feel everyone should too), is I only add a WARN_ON()
when I check something that I believe *can't* happen. If the WARN_ON()
triggers, it either means that there's a bug in the code (and needs a
fix), or the code design changed, in which case the WARN_ON() should be
either removed, or that code updated to handle the new change.

In any case, a WARN_ON() should always be investigated when hit.

The only time I've had issues with people is when I have some hardware
(i915) that triggers a WARN_ON() and I'm told that my hardware is buggy
(or I need a firmware update). In which case, I just manually remove
the WARN_ON() because the machine that triggers it is a test machine I
don't have the time to waste updating firmware on.

-- Steve