[PATCH 2/4] Add atomic operations similar to those provided by C11.

[Joseph S. Myers]

On Wed, 29 Oct 2014, Torvald Riegel wrote:

> This patch adds atomic operations similar to C11.
> 
> The function naming is essentially the C11 names, but with the memory
> order argument removed and added as a suffix.  For example, C11's
>   atomic_store_explicit(&foo, 23, memory_order_release)
> becomes
>   atomic_store_relaxed (&foo, 23);

As previously discussed, I'm concerned about the explicit relaxed loads 
and stores being defined in terms of __atomic_* (see 
<https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63273>).  Unless and until 
__atomic_* implements relaxed atomics as plain loads/stores not inhibiting 
optimization (as far as compatible with standard semantics), as evidenced 
by the change not significantly changing code generated for uses in glibc, 
I think the glibc implementation should be using plain loads and stores 
rather than __atomic_*.

-- 
Joseph S. Myers
joseph@codesourcery.com