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Re: [PATCH 2/4] Add atomic operations similar to those provided by C11.
- From: "Joseph S. Myers" <joseph at codesourcery dot com>
- To: Torvald Riegel <triegel at redhat dot com>
- Cc: GLIBC Devel <libc-alpha at sourceware dot org>
- Date: Wed, 29 Oct 2014 22:00:37 +0000
- Subject: Re: [PATCH 2/4] Add atomic operations similar to those provided by C11.
- Authentication-results: sourceware.org; auth=none
- References: <1414617613 dot 10085 dot 23 dot camel at triegel dot csb> <1414619416 dot 10085 dot 46 dot camel at triegel dot csb>
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