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Subject: Re: [RFC PATCH] printk: Use ACCESS_ONCE() instead of a volatile type
From: Joe Perches <joe@perches.com>
To: Pranith Kumar <bobby.prani@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Petr Mladek <pmladek@suse.cz>,
        Jan Kara <jack@suse.cz>, "Luis R. Rodriguez" <mcgrof@suse.com>,
        Alex Elder <elder@linaro.org>, Steven Rostedt <rostedt@goodmis.org>,
        open list <linux-kernel@vger.kernel.org>, paulmck@linux.vnet.ibm.com
Date: Thu, 13 Nov 2014 19:41:00 -0800
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References: <1415935283-19198-1-git-send-email-bobby.prani@gmail.com>
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On Thu, 2014-11-13 at 22:21 -0500, Pranith Kumar wrote:
> Remove volatile type qualifier and use ACCESS_ONCE() in its place for each
> access. Using volatile is not recommended as documented in
> Documentation/volatile-considered-harmful.txt.
> 
> Here logbuf_cpu is a local variable and it is not clear how it is being accessed
> concurrently. We should remove volatile accesses entirely here, but for now make
> a safer change of using ACCESS_ONCE().

Not recommended does not mean "don't ever use".

Forcing the volatile at each use site instead
of the declaration isn't necessarily better.

I think the code is more readable as-is but I'm
not going to object if Andrew picks this up...