linux-kernel - Re: [PATCH v3 3/3] mm/armv6: work around armv6 cmpxchg support issue

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Date:   Tue, 1 Sep 2020 14:17:49 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Alex Shi <alex.shi@...ux.alibaba.com>
Cc:     Anshuman Khandual <anshuman.khandual@....com>,
        David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Russell King <linux@...linux.org.uk>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 3/3] mm/armv6: work around armv6 cmpxchg support issue

On Tue, Sep 01, 2020 at 02:30:51PM +0800, Alex Shi wrote:
> seems there are couples archs can not do cmpxchg1
> So update the patch here. And it's easy to fix if more arch issue find here.

> +/*
> + * cmpxchg only support 32-bits operands on the following archs ARMv6, SPARC32
> + * sh2, XTENSA.
> + */
> +#if defined(CONFIG_CPU_V6) || defined(CONFIG_CPU_SH2) || \
> +	defined(CONFIG_SPARC32) || defined(CONFIG_XTENSA)

Looks like we need a HAVE_CMPXCHG_BYTE in Kconfig to parallel
HAVE_CMPXCHG_DOUBLE.