linux-kernel - Re: [PATCH] seqlock: avoid -Wshadow warnings

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Message-ID: <af5b457c-6615-0b4c-0add-529a28454459@rasmusvillemoes.dk>
Date:   Wed, 28 Oct 2020 08:51:29 +0100
From:   Rasmus Villemoes <linux@...musvillemoes.dk>
To:     Arnd Bergmann <arnd@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        "Ahmed S. Darwish" <a.darwish@...utronix.de>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Marco Elver <elver@...gle.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] seqlock: avoid -Wshadow warnings

On 28/10/2020 00.34, Arnd Bergmann wrote:
> On Mon, Oct 26, 2020 at 5:58 PM Peter Zijlstra <peterz@...radead.org> wrote:
>>
>> On Mon, Oct 26, 2020 at 05:50:38PM +0100, Arnd Bergmann wrote:
>>
>>> -     unsigned seq;                                                   \
>>> +     unsigned __seq;                                                 \
>>
>>> -     unsigned seq = __read_seqcount_begin(s);                        \
>>> +     unsigned _seq = __read_seqcount_begin(s);                       \
>>
>>> -     unsigned seq = __seqcount_sequence(s);                          \
>>> +     unsigned __seq = __seqcount_sequence(s);                        \
>>
>> Can we have a consistent number of leading '_' ?
> 
> Not really ;-)
> 
> The warning comes from raw_read_seqcount_begin() calling
> __read_seqcount_begin() and both using the same variable
> name. I could rename one of them  and use double-underscores
> for both, but I haven't come up with a good alternative name
> that wouldn't make it less consistent in the process.

At least x86's put_user and get_user use _pu/_gu suffixes on their local
variables, so perhaps that could be made a weak default convention?

__seq_rsb
__seq_rrsb
__seq_rrs

Hm, or perhaps not. But it's still better than triplicating each macro
to do a UNIQUE_ID dance.

Rasmus