On 10/03/2015 3:04 PM, Martin Buchholz wrote:
?? I mentally map Java volatile operations to C11 seq_cst because of the total order over all operations on volatile variables. Volatile reads and writes do not just have acquire/release semantics.
You may be right. The synchronization order (not just operations on volatiles) is a total order. I tend to only think about the acquire/release semantics of volatile accesses - or more specifically the allowed reorderings with respect to other stores and loads. I confess I don't know what having a total order requires beyond the barriers we utilize for the volatile read/write actions ?? The fact we have two different orderings in C11 suggests something extra is required by the implementation to achieve seq_cst.
David
The java memory model does not (yet) have C11-style relaxed atomics (like acquire or release) On Mon, Mar 9, 2015 at 6:38 PM, David Holmes <david.hol...@oracle.com <mailto:david.hol...@oracle.com>> wrote: PS. You state: "Corresponds to C11 atomic_compare_exchange___strong." Yet that would match with the full bi-directional fences of the VM implementation (due to memory_order_seq_cst), not a volatile read followed by a volatile write (which would be memory_order_acq_rel).
