From 57fa69eee6769e5e70233dc623478b48de7b07c9 Mon Sep 17 00:00:00 2001
From: andrew <andrew@FreeBSD.org>
Date: Mon, 2 Oct 2017 14:22:35 +0000
Subject: [PATCH] Add a memory barrier to ensure the atomic write is visible to
 the other CPUs before waking them up.

Sponsored by:	DARPA, AFRL
---
 sys/arm64/arm64/mp_machdep.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/sys/arm64/arm64/mp_machdep.c b/sys/arm64/arm64/mp_machdep.c
index 99c0a745eaaf..2b2d7f8fbe2c 100644
--- a/sys/arm64/arm64/mp_machdep.c
+++ b/sys/arm64/arm64/mp_machdep.c
@@ -236,7 +236,10 @@ release_aps(void *dummy __unused)
 
 	atomic_store_rel_int(&aps_ready, 1);
 	/* Wake up the other CPUs */
-	__asm __volatile("sev");
+	__asm __volatile(
+	    "dsb ishst	\n"
+	    "sev	\n"
+	    ::: "memory");
 
 	printf("Release APs\n");