linux-kernel - Re: [PATCH] arm64: fix unreachable code issue with cmpxchg

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Message-ID: <20190910074606.45k5m2pkztlpj4nj@willie-the-truck>
Date:   Tue, 10 Sep 2019 08:46:07 +0100
From:   Will Deacon <will@...nel.org>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Andrew Murray <andrew.murray@....com>,
        Mark Rutland <mark.rutland@....com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com
Subject: Re: [PATCH] arm64: fix unreachable code issue with cmpxchg

On Mon, Sep 09, 2019 at 10:21:35PM +0200, Arnd Bergmann wrote:
> On arm64 build with clang, sometimes the __cmpxchg_mb is not inlined
> when CONFIG_OPTIMIZE_INLINING is set.

Hmm. Given that CONFIG_OPTIMIZE_INLINING has also been shown to break
assignment of local 'register' variables on GCC, perhaps we should just
disable that option for arm64 (at least) since we don't have any toolchains
that seem to like it very much! I'd certainly prefer that over playing
whack-a-mole with __always_inline.

Will