From 403ddccb10e2130fd363fddeb99481d7afb5b03b Mon Sep 17 00:00:00 2001
From: Andrew Turner <andrew@FreeBSD.org>
Date: Sat, 15 Oct 2016 09:54:22 +0000
Subject: [PATCH] Check we are in a critical section when calling vfp_discard.
 As we may call it with a NULL thread pointer only check when it is non-NULL.

Obtained from:	ABT Systems Ltd
Sponsored by:	The FreeBSD Foundation
---
 sys/arm64/arm64/vfp.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sys/arm64/arm64/vfp.c b/sys/arm64/arm64/vfp.c
index 8e648336342..f1fbb56a352 100644
--- a/sys/arm64/arm64/vfp.c
+++ b/sys/arm64/arm64/vfp.c
@@ -79,6 +79,10 @@ void
 vfp_discard(struct thread *td)
 {
 
+#ifdef INVARIANTS
+	if (td != NULL)
+		CRITICAL_ASSERT(td);
+#endif
 	if (PCPU_GET(fpcurthread) == td)
 		PCPU_SET(fpcurthread, NULL);