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From: Andrew Turner <andrew@FreeBSD.org>
Date: Mon, 2 Oct 2017 14:22:35 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r324207 - head/sys/arm64/arm64
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Author: andrew
Date: Mon Oct  2 14:22:35 2017
New Revision: 324207
URL: https://svnweb.freebsd.org/changeset/base/324207

Log:
  Add a memory barrier to ensure the atomic write is visible to the other
  CPUs before waking them up.
  
  Sponsored by:	DARPA, AFRL

Modified:
  head/sys/arm64/arm64/mp_machdep.c

Modified: head/sys/arm64/arm64/mp_machdep.c
==============================================================================
--- head/sys/arm64/arm64/mp_machdep.c	Mon Oct  2 14:19:31 2017	(r324206)
+++ head/sys/arm64/arm64/mp_machdep.c	Mon Oct  2 14:22:35 2017	(r324207)
@@ -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");