linux-kernel - Re: [PATCH] debug: Deprecate BUG_ON() use in new code, introduce CRASH

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Date:	Mon, 08 Jun 2015 10:42:54 +0200
From:	Alexander Holler <holler@...oftware.de>
To:	Richard Weinberger <richard.weinberger@...il.com>
CC:	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Tejun Heo <htejun@...il.com>,
	Louis Langholtz <lou_langholtz@...com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Trivial patch monkey <trivial@...nel.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] debug: Deprecate BUG_ON() use in new code, introduce
 CRASH_ON()

Am 08.06.2015 um 10:08 schrieb Richard Weinberger:
> On Mon, Jun 8, 2015 at 9:40 AM, Alexander Holler <holler@...oftware.de> wrote:
>> Am 08.06.2015 um 09:12 schrieb Ingo Molnar:
>>>
>>>
>>> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>>>
>>>> Stop with the random BUG_ON() additions.
>>>
>>>
>>> Yeah, so I propose the attached patch which attempts to resist new
>>> BUG_ON()
>>> additions.
>>
>>
>> As this reminded me at flame I received once from a maintainer because I
>> wanted to avoid a desastrous memory corruption by using a BUG_ON().
>
> Reference?

https://lkml.org/lkml/2013/5/17/254

To explain: The bug already existed for several releases and the memory 
corruption was that desatrous that it even leaded here to hard resets of 
systems without any oops. And fixing it needed several more releases 
(another year).

And in the above mentioned case and the kernel config settings I use(d), 
only the wronggoing thread was killed by the BUG_ON (I proposed) before 
it had the chance to corrupt the memory.

Maybe someone could clarify what Greg meant with "something _really_ 
bad", because in my humble opionion there aren't much more worse things 
than memory corruptions (e.g. by wrong pointers, use after free or 
similiar stuff) if that happens inside the kernel. The consequences of 
such are almost always unpredictable and therefor I would and likely 
will ever prefer a controlled shutdown, reset or similiar instead of 
leaving a system running with corrupted memory. Regardless what any 
maintainer will say.

Regards,

Alexander Holler
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