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From:   Charlemagne Lasse <charlemagnelasse@gmail.com>
Date:   Wed, 17 May 2023 09:41:41 +0200
Message-ID: <CAFGhKbyxtuk=LoW-E3yLXgcmR93m+Dfo5-u9oQA_YC5Fcy_t9g@mail.gmail.com>
Subject: Re: [PATCH v2 3/5] locking/arch: Wire up local_try_cmpxchg
To:     Uros Bizjak <ubizjak@gmail.com>
Cc:     linux-alpha@vger.kernel.org, loongarch@lists.linux.dev,
        linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
        x86@kernel.org, linux-arch@vger.kernel.org,
        linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
        Richard Henderson <richard.henderson@linaro.org>,
        Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
        Matt Turner <mattst88@gmail.com>,
        Huacai Chen <chenhuacai@kernel.org>,
        WANG Xuerui <kernel@xen0n.name>,
        Jiaxun Yang <jiaxun.yang@flygoat.com>,
        Jun Yi <yijun@loongson.cn>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Nicholas Piggin <npiggin@gmail.com>,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>
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> +static __inline__ bool local_try_cmpxchg(local_t *l, long *old, long new)
> +{
> +       typeof(l->a.counter) *__old = (typeof(l->a.counter) *) old;
> +       return try_cmpxchg_local(&l->a.counter, __old, new);
> +}
> +

This patch then causes following sparse errors:

    ./arch/x86/include/asm/local.h:131:16: warning: symbol '__old'
shadows an earlier one
    ./arch/x86/include/asm/local.h:130:30: originally declared here

This is then visible in all kinds of builds - which makes it hard to
find out actual problems with sparse.