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Date:   Wed, 12 Apr 2023 13:32:31 +0200
From:   Peter Zijlstra <peterz@infradead.org>
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>
Subject: Re: [PATCH v2 3/5] locking/arch: Wire up local_try_cmpxchg
Message-ID: <20230412113231.GA628377@hirez.programming.kicks-ass.net>
References: <20230405141710.3551-1-ubizjak@gmail.com>
 <20230405141710.3551-4-ubizjak@gmail.com>
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On Wed, Apr 05, 2023 at 04:17:08PM +0200, Uros Bizjak wrote:
> diff --git a/arch/powerpc/include/asm/local.h b/arch/powerpc/include/asm/local.h
> index bc4bd19b7fc2..45492fb5bf22 100644
> --- a/arch/powerpc/include/asm/local.h
> +++ b/arch/powerpc/include/asm/local.h
> @@ -90,6 +90,17 @@ static __inline__ long local_cmpxchg(local_t *l, long o, long n)
>  	return t;
>  }
>  
> +static __inline__ bool local_try_cmpxchg(local_t *l, long *po, long n)
> +{
> +	long o = *po, r;
> +
> +	r = local_cmpxchg(l, o, n);
> +	if (unlikely(r != o))
> +		*po = r;
> +
> +	return likely(r == o);
> +}
> +

Why is the ppc one different from the rest? Why can't it use the
try_cmpxchg_local() fallback and needs to have it open-coded?