Expand generic subword atomic primitives

The goal of this change is to make the atomic_load_acq_{8,16},
atomic_testandset{,_acq}_long, and atomic_testandclear_long primitives
available in MI-namespace.

The second goal is to get this draft out of my local tree, as anything that
requires a full tinderbox is a big burden out of tree.  MD specifics can be
refined individually afterwards.

The generic implementations may not be ideal for your architecture; feel
free to implement better versions.  If no subword_atomic definitions are
needed, the include can be removed from your arch's machine/atomic.h.
Generic definitions are guarded by defined macros of the same name.  To
avoid picking up conflicting generic definitions, some macro defines are
added to various MD machine/atomic.h to register an existing implementation.

Include _atomic_subword.h in arm and arm64 machine/atomic.h.

For some odd reason, KCSAN only generates some versions of primitives.
Generate the _acq variants of atomic_load.*_8, atomic_load.*_16, and
atomic_testandset.*_long.  There are other questionably disabled primitives,
but I didn't run into them, so I left them alone.  KCSAN is only built for
amd64 in tinderbox for now.

Add atomic_subword implementations of atomic_load_acq_{8,16} implemented
using masking and atomic_load_acq_32.

Add generic atomic_subword implementations of atomic_testandset_long(),
atomic_testandclear_long(), and atomic_testandset_acq_long(), using
atomic_fcmpset_long() and atomic_fcmpset_acq_long().

On x86, add atomic_testandset_acq_long as an alias for
atomic_testandset_long.

Reviewed by:	kevans, rlibby (previous versions both)
Differential Revision:	https://reviews.freebsd.org/D22963

1 files changed, 1 insertions, 0 deletions

diff --git a/sys/i386/include/atomic.h b/sys/i386/include/atomic.h
index bd6da487e6a9..14fa3040341c 100644
--- a/sys/i386/include/atomic.h
+++ b/sys/i386/include/atomic.h
@@ -808,6 +808,7 @@ u_long	atomic_swap_long(volatile u_long *p, u_long v);
 
 #define	atomic_readandclear_int(p)	atomic_swap_int(p, 0)
 #define	atomic_readandclear_long(p)	atomic_swap_long(p, 0)
+#define	atomic_testandset_acq_long	atomic_testandset_long
 
 /* Operations on 8-bit bytes. */
 #define	atomic_set_8		atomic_set_char