On Thu, Jan 06, 2022 at 10:52:47AM +0000, yangx.jy@xxxxxxxxxxx wrote: > On 2022/1/6 7:53, Jason Gunthorpe wrote: > > On Thu, Dec 30, 2021 at 04:39:01PM -0500, Tom Talpey wrote: > > > >> Because RXE is a software provider, I believe the most natural approach > >> here is to use an atomic64_set(dst, *src). > > A smp_store_release() is most likely sufficient. > Hi Jason, Tom > > Is smp_store_mb() better here? It calls WRITE_ONCE + smb_mb/barrier(). > I think the semantics of 'atomic write' is to do atomic write and make > the 8-byte data reach the memory. No, it is not 'data reach memory' it is a 'release' in that if the CPU later does an 'acquire' on the written data it is guarenteed to see all the preceeding writes. Memory barriers are always paired with read and write, it is important to understand what the read half of the pair is. Jason
