linux-kernel - Re: [PATCH 1/2] dma/pool: trivial: add semicolon after label attributes

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Date:   Tue, 29 Aug 2023 16:28:05 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Christoph Hellwig <hch@....de>
Cc:     Chunhui He <hchunhui@...l.ustc.edu.cn>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dma/pool: trivial: add semicolon after label
 attributes

On 29/08/2023 4:12 pm, Christoph Hellwig wrote:
> On Tue, Aug 29, 2023 at 03:22:22PM +0100, Robin Murphy wrote:
>> AFAICS, what that clearly says is that *C++* label attributes can be
>> ambiguous. This is not C++ code. Even in C11, declarations still cannot be
>> labelled, so it should still be the case that, per the same GCC
>> documentation, "the ambiguity does not arise". And even if the language did
>> allow it, an inline declaration at that point at the end of a function
>> would be downright weird and against the kernel coding style anyway.
>>
>> So, I don't really see what's "better" about cluttering up C code with
>> unnecessary C++isms; it's just weird noise to me. The only thing I think it
>> *does* achieve is introduce the chance that the static checker brigade
>> eventually identifies a redundant semicolon and we get more patches to
>> remove it again.
> 
> Agreed.  Even more importantly that attribute looks rather questionable
> to start with as it can be dropped by just moving the #endif a little:
> 
> diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
> index 1acec2e228273f..da03c4a57cebe3 100644
> --- a/kernel/dma/pool.c
> +++ b/kernel/dma/pool.c
> @@ -135,8 +135,8 @@ static int atomic_pool_expand(struct gen_pool *pool, size_t pool_size,
>   remove_mapping:
>   #ifdef CONFIG_DMA_DIRECT_REMAP
>   	dma_common_free_remap(addr, pool_size);
> +free_page:
>   #endif
> -free_page: __maybe_unused
>   	__free_pages(page, order);
>   out:
>   	return ret;

Oh, indeed - I hadn't really looked at the context itself. My 
non-exhaustive grep skills show a couple of hundred instances of 
label-above-#endif vs. three (!) instances of __maybe_unused, so ack to 
making that cleanup to just remove the question entirely.

Cheers,
Robin.