[PATCH] Fix x86 atomic_fetch_xor_release.

[Torvald Riegel]

On Mon, 2016-10-17 at 23:18 -0400, Carlos O'Donell wrote:
> Torvald,
> 
> No code uses atomic_fetch_xor_release except for the upcoming conditional
> variable rewrite. Therefore there is no user visible bug here.
> 
> The use of atomic_compare_and_exchange_bool_rel is removed (since it doesn't
> exist anymore), and is replaced by atomic_compare_exchange_weak_release.
> 
> We use weak_release because it provides better performance in the loop
> (the weak semantic) and because the xor is release MO (the release semantic).
> 
> We don't reload expected in the loop because atomic_compare_and_exchange_weak_release
> does this for us as part of the CAS failure.
> 
> It is otherwise a fairly plain conversion that fixes building the new condvar
> for 32-bit x86.
> 
> I have pushed the new condvar into Fedora Rawhide for testing.
> 
> OK to checkin?

OK.