From 4869ce0a43a77bfcaa38947bf4fb06d7dffd9f71 Mon Sep 17 00:00:00 2001
From: pgoyette <pgoyette@NetBSD.org>
Date: Tue, 10 Jan 2017 22:08:14 +0000
Subject: [PATCH] Use membar_{producer,consumer}() to ensure proper access to
 the "ready" flag.

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

diff --git a/sys/kern/kern_history.c b/sys/kern/kern_history.c
index 25d37eea37bb..fd96aae1ac61 100644
--- a/sys/kern/kern_history.c
+++ b/sys/kern/kern_history.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: kern_history.c,v 1.13 2017/01/10 00:50:57 pgoyette Exp $	 */
+/*	$NetBSD: kern_history.c,v 1.14 2017/01/10 22:08:14 pgoyette Exp $	 */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -33,7 +33,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_history.c,v 1.13 2017/01/10 00:50:57 pgoyette Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_history.c,v 1.14 2017/01/10 22:08:14 pgoyette Exp $");
 
 #include "opt_ddb.h"
 #include "opt_kernhist.h"
@@ -43,6 +43,7 @@ __KERNEL_RCSID(0, "$NetBSD: kern_history.c,v 1.13 2017/01/10 00:50:57 pgoyette E
 #include "opt_biohist.h"
 #include "opt_sysctl.h"
 
+#include <sys/atomic.h>
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/cpu.h>
@@ -289,6 +290,7 @@ sysctl_kernhist_new(struct kern_history *hist)
 	struct kern_history *h;
 	const struct sysctlnode *rnode = NULL;
 
+	membar_consumer();
 	if (kernhist_sysctl_ready == 0)
 		return;
 
@@ -329,6 +331,7 @@ sysctl_kernhist_init(void)
 	sysctl_hist_node = rnode->sysctl_num;
 
 	kernhist_sysctl_ready = 1;
+	membar_producer();
 
 	sysctl_kernhist_new(NULL);
 }