Re: [PATCH TRIVIAL] mm: Fix build warning in kmem_cache_create()

From: Pekka Enberg <penberg@kernel.org>
To: David Rientjes <rientjes@google.com>
Cc: Shuah Khan <shuah.khan@hp.com>,
	cl@linux.com, glommer@parallels.com, js1304@gmail.com,
	shuahkhan@gmail.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH TRIVIAL] mm: Fix build warning in kmem_cache_create()
Date: Sat, 14 Jul 2012 15:01:40 +0300	[thread overview]
Message-ID: <CAOJsxLE3dDd01WaAp5UAHRb0AiXn_s43M=Gg4TgXzRji_HffEQ@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.00.1207140216040.20297@chino.kir.corp.google.com>

On Sat, Jul 14, 2012 at 12:18 PM, David Rientjes <rientjes@google.com> wrote:
> On Fri, 13 Jul 2012, Shuah Khan wrote:
>
>> diff --git a/mm/slab_common.c b/mm/slab_common.c
>> index 12637ce..aa3ca5b 100644
>> --- a/mm/slab_common.c
>> +++ b/mm/slab_common.c
>> @@ -98,7 +98,9 @@ struct kmem_cache *kmem_cache_create(const char *name, size_t size, size_t align
>>
>>       s = __kmem_cache_create(name, size, align, flags, ctor);
>>
>> +#ifdef CONFIG_DEBUG_VM
>>  oops:
>> +#endif
>>       mutex_unlock(&slab_mutex);
>>       put_online_cpus();
>>
>
> Tip: gcc allows label attributes so you could actually do
>
> oops: __maybe_unused
>
> to silence the warning and do the same for the "out" label later in the
> function.

I'm not exactly loving that either.

It'd probably be better to reshuffle the code so that the debug checks
end up in separate functions that are no-op for !CONFIG_DEBUG_VM. That
way the _labels_ are used unconditionally although there's no actual
code generated.

                        Pekka