On Fri, Nov 10, 2023 at 09:49:06PM +0000, John Morris wrote: > Most out-of-order machines include “read acquire” and “write release” > which are pretty close to what you’re suggesting. With the current > routines, we only have “read relaxed” and “write relaxed”. I think > implementing acquire/release semantics is a very good idea,
We do have both pg_atomic_write_u32() and pg_atomic_unlocked_write_u32() (see commit b0779ab), but AFAICT those only differ in the fallback/spinlock implementations. I suppose there could be an unlocked 64-bit write on platforms that have 8-byte single-copy atomicity but still need to use the fallback/spinlock implementation for some reason, but that might be a bit of a stretch, and the use-cases might be few and far between... > I would also like to clarify the properties of atomics. One very > important question: Are atomics also volatile? The PostgreSQL atomics support appears to ensure they are volatile. -- Nathan Bossart Amazon Web Services: https://aws.amazon.com
