Message-ID: <4abd97fe-412d-4e3e-9efc-cf3092d66e57@collabora.com>
Date: Thu, 21 Aug 2025 17:31:21 +0500
From: Muhammad Usama Anjum <usama.anjum@...labora.com>
To: Kevin Brodsky <kevin.brodsky@....com>,
 Andrew Morton <akpm@...ux-foundation.org>
Cc: usama.anjum@...labora.com, kernel@...labora.com,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 Vlastimil Babka <vbabka@...e.cz>, Albert Ou <aou@...s.berkeley.edu>,
 Zi Yan <ziy@...dia.com>, David Hildenbrand <david@...hat.com>,
 Suren Baghdasaryan <surenb@...gle.com>,
 "Liam R. Howlett" <Liam.Howlett@...cle.com>,
 Baolin Wang <baolin.wang@...ux.alibaba.com>, Mike Rapoport
 <rppt@...nel.org>, Peter Xu <peterx@...hat.com>,
 Jason Gunthorpe <jgg@...pe.ca>, Palmer Dabbelt <palmer@...belt.com>,
 Ryan Roberts <ryan.roberts@....com>, Leon Romanovsky <leon@...nel.org>,
 Shuah Khan <shuah@...nel.org>, Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Alexandre Ghiti <alex@...ti.fr>, Barry Song <baohua@...nel.org>,
 Dev Jain <dev.jain@....com>, linux-kselftest@...r.kernel.org,
 Paul Walmsley <paul.walmsley@...ive.com>, linux-mm@...ck.org,
 Nico Pache <npache@...hat.com>, John Hubbard <jhubbard@...dia.com>,
 Michal Hocko <mhocko@...e.com>
Subject: Re: [PATCH v2 4/8] selftests/mm: Add -Wunused family of flags

On 8/21/25 3:43 PM, Kevin Brodsky wrote:
> On 21/08/2025 08:28, Muhammad Usama Anjum wrote:
>>> As to -Wunused-parameter I am frankly not convinced it's worth the
>>> hassle. We're getting 90 lines changed in patch 6-8 just to mark
>>> parameters as unused, in other words noise to keep the compiler happy.
>>> It is not enabled by default in the kernel proper precisely because it
>>> is so noisy when callbacks are involved.
>>>
>>> Patch 5 is clearly an improvement, but I'd rather take it without
>>> actually enabling -Wunused-parameter. The rest of this patch isn't that
>>> useful either IMHO.
>> Patch 5 removes genuinely unused parameters flagged by the compiler. If we
>> drop the -Wunused-parameter option, however, new unused parameters will
>> continue to creep in with future patches. The goal of enabling this warning
>> is to surface such issues early so developers can address them during
>> development, rather than later during review or debugging.
>>
>> Long term, I’d like us to rely more on compiler and static analysis just like
>> kernel to catch these kinds of problems proactively, instead of waiting until
>> they’re reported or someone fixes them later. While it may feel like noise
>> initially, this is largely a one-time cleanup—once done, developers will
>> simply fix warnings as they arise, keeping the codebase cleaner going forward.
> 
> Agreed on the general principle, but I think the hassle is just too big
> for what we're getting in return here (see also Andrew's reply). New
> code may also introduce a bunch of unused parameters for legitimate
> reasons and it's easy to imagine contributors ignoring such seemingly
> harmless/irrelevant warnings instead of sprinkling __unused all over.


> My
> feeling is that unused parameters are expected to be allowed in the
> kernel and it isn't helpful to go against that expectation in just a
> small subset of kselftests.
I thought kernel must be giving error for unused parameters as well (from
my memory). But just checked and it doesn't seem like it. I'm okay with
dropping -Wunused-parameters.

We need to drop patch 6/7 and in Patch 4 should have only:

-CFLAGS += -Wunused  -Wunused-parameter -Wunused-function -Wunused-label -Wunused-variable -Wunused-value
+CFLAGS += -Wunused

@Andrew, Should I resend the entire series or would you can make the change?

> 
> - Kevin


-- 
---
Thanks,
Usama

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