Re: Status of 64 bit atomics

Hi,

On 2016-05-27 11:00:42 -0400, John Gorman wrote:
> Someone recently told me that the postgresql atomics library was incomplete
> for 64 bit operations such as pg_atomic_fetch_add_u64() and should not be
> used.

There's currently no fallback for 32bit platforms without 64bit atomics
support. I posted a patch adding that fallback, which I plan to commit
soon after the start of the 9.7 development window opens.

> Can someone definitively confirm whether it is okay to rely on the 64
> bit atomics or whether it is better to protect 64 bit operations with
> a spinlock?

For current versions 64bit atomics are working, but you'll get
compilation errors if the platform doesn't have 64bit atomics
support. That's not actually many CPUs these days; most prominent are
probably older arm CPUs.

Andres