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Subject: Re: svn commit: r324926 - head/share/man/man9
From: Ian Lepore <ian@freebsd.org>
To: Konstantin Belousov <kib@FreeBSD.org>, src-committers@freebsd.org,
 svn-src-all@freebsd.org, svn-src-head@freebsd.org
Date: Mon, 23 Oct 2017 10:28:22 -0600
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On Mon, 2017-10-23 at 16:14 +0000, Konstantin Belousov wrote:
> Author: kib
> Date: Mon Oct 23 16:14:55 2017
> New Revision: 324926
> URL: https://svnweb.freebsd.org/changeset/base/324926
> 
> Log:
>   Expand explanation of atomicity.
>   
>   Mention per-location total order, out of thin air, and torn writes
>   guarantees.  Mention C11 standard' memory model and one most important
>   FreeBSD additional requirement, that is aligned ordinary loads and
>   stores are atomic on processors.
>   
> [...]
> 
> +On all architectures supported by
> +.Fx ,
> +ordinary loads and stores of naturally aligned integer types
> +are atomic, as executed by the processor.

This is not true on arm{v6,v7}.  64-bit integer types can be atomically
loaded and stored with the appropriate functions from atomic.h, but are
not ordinarily so, regardless of alignment.  Smaller integer types do
meet this requirement.

-- Ian