linux-kernel - Re: [PATCH] kernel/params.c: make use of unused but set variable

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Date:	Sun, 7 Jun 2015 17:17:20 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Tejun Heo <htejun@...il.com>
Cc:	Louis Langholtz <lou_langholtz@...com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	trivial@...nel.org, Rusty Russell <rusty@...tcorp.com.au>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] kernel/params.c: make use of unused but set variable

On Sun, Jun 7, 2015 at 5:00 PM, Tejun Heo <htejun@...il.com> wrote:
> On Sun, Jun 07, 2015 at 05:54:30PM -0600, Louis Langholtz wrote:
>> @@ -853,6 +853,7 @@ static void __init version_sysfs_builtin(void)
>>               mk = locate_module_kobject(vattr->module_name);
>>               if (mk) {
>>                       err = sysfs_create_file(&mk->kobj, &vattr->mattr.attr);
>> +                     BUG_ON(err);
>
> Maybe BUG_ON(sysfs_create_file(...)); is simpler?  Other than that,

Hell no.

Stop with the random BUG_ON() additions.

I have said this before, and apparently I need to sat this again, and
probably I will have to say it in the future.

We don't add BUG_ON's for random reasons.

The *ONLY* acceptable reason for a BUG_ON() is if the machine is dead
anyway because of some major internal corruption.

We have too many BUG_ON's. We've had people add BUG_ON's because "this
cannot happen", and then it turns out they were wrong, and they just
killed the machine.

Dammit, there's no reason to add a BUG_ON() here in the first place,
and the reason of "but but it's an unused error return": is f*cking
retarded.

Stop this idiocy. We don't write crap code just to satisfy some random
coding standard or shut up a compiler error.

At most, it could be a "WARN_ON_ONCE()". Maybe even just silently
ignore the error. But BUG_ON()? Hell no.

NO NO NO.

Quite frankly, if you want to add error handling, then dammit, add it
right. And no, BUG_ON() is _never_ proper error handling.

BUG_ON() is for things like "uhhuh, somebody is trying to free a page
that is already free". That is some serious internal corruption.

BUG_ON() is _not_ for "I'm not doing any error handling, so I'll
sprinkle random lines of BUG_ON() like fairy dust to make the compiler
happen".

Really.  I'm getting very tired indeed of people adding BUG_ON's like
that. Stop it.

                Linus
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