[src/trunk]: src/sys/external/bsd/common/include/asm linux: Define mb/wmb/rmb...

[riastradh <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/9d3687644cf2
branches:  trunk
changeset: 1028892:9d3687644cf2
user:      riastradh <riastradh%NetBSD.org@localhost>
date:      Sun Dec 19 12:25:05 2021 +0000

description:
linux: Define mb/wmb/rmb for x86.

These are _not_ SMP barriers; on Linux they specifically mean
mfence/sfence/lfence.  Although membar_sync and mb agree, and
membar_consumer and rmb agree, membar_producer and wmb _do not_ agree
on x86 -- Linux's wmb is specifically sfence, which is important only
for unusual memory types, whereas our membar_producer is limited to
ordinary memory.

diffstat:

 sys/external/bsd/common/include/asm/barrier.h |  7 ++++++-
 1 files changed, 6 insertions(+), 1 deletions(-)

diffs (21 lines):

diff -r caf2e349f482 -r 9d3687644cf2 sys/external/bsd/common/include/asm/barrier.h
--- a/sys/external/bsd/common/include/asm/barrier.h     Sun Dec 19 12:24:57 2021 +0000
+++ b/sys/external/bsd/common/include/asm/barrier.h     Sun Dec 19 12:25:05 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: barrier.h,v 1.8 2021/12/19 11:02:54 riastradh Exp $    */
+/*     $NetBSD: barrier.h,v 1.9 2021/12/19 12:25:05 riastradh Exp $    */
 
 /*-
  * Copyright (c) 2013 The NetBSD Foundation, Inc.
@@ -46,6 +46,11 @@
 #define        mb()    __asm __volatile ("dsb sy" ::: "memory")
 #define        wmb()   __asm __volatile ("dsb st" ::: "memory")
 #define        rmb()   __asm __volatile ("dsb ld" ::: "memory")
+#elif defined(__x86_64__)
+#include <x86/cpufunc.h>
+#define        mb()    x86_mfence()
+#define        wmb()   x86_sfence()
+#define        rmb()   x86_lfence()
 #else
 #define        mb      membar_sync
 #define        wmb     membar_producer