[src/trunk]: src/sys/kern requires memory barrier before IPI ack.

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

details:   https://anonhg.NetBSD.org/src/rev/2a88e6eece5b
branches:  trunk
changeset: 965189:2a88e6eece5b
user:      ryo <ryo%NetBSD.org@localhost>
date:      Thu Sep 05 09:20:05 2019 +0000

description:
requires memory barrier before IPI ack.
Problem was seen on the aarch64 cpus.

Fixes PR/54009

diffstat:

 sys/kern/subr_ipi.c |  7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diffs (28 lines):

diff -r 23860a23a01c -r 2a88e6eece5b sys/kern/subr_ipi.c
--- a/sys/kern/subr_ipi.c       Thu Sep 05 08:06:51 2019 +0000
+++ b/sys/kern/subr_ipi.c       Thu Sep 05 09:20:05 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_ipi.c,v 1.4 2019/04/06 02:59:05 thorpej Exp $     */
+/*     $NetBSD: subr_ipi.c,v 1.5 2019/09/05 09:20:05 ryo Exp $ */
 
 /*-
  * Copyright (c) 2014 The NetBSD Foundation, Inc.
@@ -36,7 +36,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_ipi.c,v 1.4 2019/04/06 02:59:05 thorpej Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_ipi.c,v 1.5 2019/09/05 09:20:05 ryo Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -331,6 +331,9 @@
                msg->func(msg->arg);
 
                /* Ack the request. */
+#ifndef __HAVE_ATOMIC_AS_MEMBAR
+               membar_producer();
+#endif
                atomic_dec_uint(&msg->_pending);
        }
 }