linux-kernel - Re: [PATCH v1 1/3] coding-style.rst: document BUG() and WARN() rules ("do not crash the kernel")

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Message-ID: <87leq64m20.fsf@kernel.org>
Date:   Mon, 26 Sep 2022 10:44:23 +0300
From:   Kalle Valo <kvalo@...nel.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        David Laight <David.Laight@...LAB.COM>,
        Jonathan Corbet <corbet@....net>,
        Andy Whitcroft <apw@...onical.com>,
        Joe Perches <joe@...ches.com>,
        Dwaipayan Ray <dwaipayanray1@...il.com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        Baoquan He <bhe@...hat.com>, Vivek Goyal <vgoyal@...hat.com>,
        Dave Young <dyoung@...hat.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>
Subject: Re: [PATCH v1 1/3] coding-style.rst: document BUG() and WARN() rules ("do not crash the kernel")

David Hildenbrand <david@...hat.com> writes:

>>> +Use WARN_ON_ONCE() rather than WARN() or WARN_ON()
>>> +**************************************************
>>> +
>>> +WARN_ON_ONCE() is generally preferred over WARN() or WARN_ON(), because it
>>> +is common for a given warning condition, if it occurs at all, to occur
>>> +multiple times. This can fill up and wrap the kernel log, and can even slow
>>> +the system enough that the excessive logging turns into its own, additional
>>> +problem.
>>
>> FWIW I have had cases where WARN() messages caused a reboot, maybe
>> mention that here? In my case the logging was so excessive that the
>> watchdog wasn't updated and in the end the device was forcefully
>> rebooted.
>>
>
> That should be covered by the last part, no? What would be your suggestion?

I was just thinking that maybe make it more obvious that even WARN_ON()
can crash the system, something along these lines:

"..., additional problem like stalling the system so much that it causes
a reboot."

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