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Date:   Wed, 16 May 2018 08:07:22 +0200
From:   Christoph Hellwig <hch@lst.de>
To:     Bart Van Assche <bart.vanassche@wdc.com>
Cc:     Jens Axboe <axboe@kernel.dk>, linux-block@vger.kernel.org,
        linux-kernel@vger.kernel.org, Christoph Hellwig <hch@lst.de>,
        Catalin Marinas <catalin.marinas@arm.com>,
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        Fenghua Yu <fenghua.yu@intel.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>,
        "James E.J. Bottomley" <jejb@parisc-linux.org>,
        Helge Deller <deller@gmx.de>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
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        Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v9 1/2] arch/*: Add CONFIG_ARCH_HAVE_CMPXCHG64
Message-ID: <20180516060722.GA24855@lst.de>
References: <20180515225124.20428-1-bart.vanassche@wdc.com> <20180515225124.20428-5-bart.vanassche@wdc.com>
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> +config ARCH_HAVE_CMPXCHG64
> +	bool

64-bit architectures must support this as long is 64-bits wide.

So this should have a

	default y if 64BIT

which also means you only need to explicitly select in on 32-bit
architectures that support 64-bit cmpxchg.