tree a10dc9146f9a5d2d4bb1e0696238911b43230e7a
parent a477150fd7ceba3af3d4db64bcf924f8a8f2da6c
author Willy Tarreau <w@1wt.eu> 1617703061 +0200
committer Willy Tarreau <w@1wt.eu> 1617812317 +0200
encoding latin1

CLEANUP: atomic: add a fetch-and-xxx variant for common operations

The fetch_and_xxx variant is often missing for add/sub/and/or. In fact
it was only provided for ADD under the name XADD which corresponds to
the x86 instruction name. But for destructive operations like AND and
OR it's missing even more as it's not possible to know the value before
modifying it.

This patch explicitly adds HA_ATOMIC_FETCH_{OR,AND,ADD,SUB} which
cover these standard operations, and renames XADD to FETCH_ADD (there
were only 6 call places).

In the future, backport of fixes involving such operations could simply
remap FETCH_ADD(x) to XADD(x), FETCH_SUB(x) to XADD(-x), and for the
OR/AND if needed, these could possibly be done using BTS/BTR.

It's worth noting that xchg could have been renamed to fetch_and_store()
but xchg already has well understood semantics and it wasn't needed to
go further.