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

From: Louis Langholtz <lou_langholtz@me.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Tejun Heo <htejun@gmail.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	trivial@kernel.org, Rusty Russell <rusty@rustcorp.com.au>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH] kernel/params.c: make use of unused but set variable
Date: Sun, 07 Jun 2015 23:46:35 -0600	[thread overview]
Message-ID: <1FDBC3D2-5147-4D2F-B503-AD9596705A99@me.com> (raw)
In-Reply-To: <CA+55aFwmOGaP1DN3frkfP+Df=jCwURqO22A6-5GqpMnZXkvMXA@mail.gmail.com>

On Jun 7, 2015, at 6:17 PM, Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Sun, Jun 7, 2015 at 5:00 PM, Tejun Heo <htejun@gmail.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.
> ...
> The *ONLY* acceptable reason for a BUG_ON() is if the machine is dead
> anyway because of some major internal corruption.
> ...
> At most, it could be a "WARN_ON_ONCE()"...
> 
>                Linus

Agreed. The comments in the bug.h file say this clearly too - to not use
BUG_ON "unless there's really no way out".

I originally just wanted a light-weight message to be issued on failure so
at least there's some notice that something unexpected happened (and
to have the must-check value used). I've submitted a second version
now as you probably saw (that instead uses WARN_ON_ONCE).