linux-kernel - Re: [PATCH v2 1/8] asm-generic/io.h: allow barriers in io{read,write}{16,32}be

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Message-ID: <4160174.j7y8ElCmf4@wuerfel>
Date:	Thu, 05 May 2016 18:29:27 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Horia Geantă <horia.geanta@....com>
Cc:	linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/8] asm-generic/io.h: allow barriers in io{read,write}{16,32}be

On Thursday 05 May 2016 18:35:45 Horia Geantă wrote:
> While reviewing the addition of io{read,write}64be accessors, Arnd
> 
> -finds a potential problem:
> "If an architecture overrides readq/writeq to have barriers but does
> not override ioread64be/iowrite64be, this will lack the barriers and
> behave differently from the little-endian version. I think the only
> affected architecture is ARC, since ARM and ARM64 both override the
> big-endian accessors to have the correct barriers, and all others
> don't use barriers at all."
> 
> -suggests a fix for the same problem in existing code (16/32-bit
> accessors); the fix leads "to a double-swap on architectures that
> don't override the io{read,write}{16,32}be accessors, but it will
> work correctly on all architectures without them having to override
> these accessors."
> 
> Suggested-by: Arnd Bergmann <arnd@...db.de>
> Signed-off-by: Horia Geantă <horia.geanta@....com>
> ---

Acked-by: Arnd Bergmann <arnd@...db.de>