From 1013c0930e11e8a24d66da3dbdea26f72d25cbc2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Sur=C3=BD?= <ondrej@isc.org>
Date: Thu, 11 Jun 2020 13:01:26 +0200
Subject: [PATCH] Add missing acquire memory barrier in isc_nmhandle_unref

The ThreadSanitizer uses system synchronization primitives to check for
data race.  The netmgr handle->references was missing acquire memory
barrier before resetting and reusing the memory occupied by isc_nmhandle_t.
---
 lib/isc/netmgr/netmgr.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/lib/isc/netmgr/netmgr.c b/lib/isc/netmgr/netmgr.c
index 9e4b692f80..35469b6dff 100644
--- a/lib/isc/netmgr/netmgr.c
+++ b/lib/isc/netmgr/netmgr.c
@@ -1156,6 +1156,8 @@ isc_nmhandle_unref(isc_nmhandle_t *handle) {
 	if (isc_refcount_decrement(&handle->references) > 1) {
 		return;
 	}
+	/* We need an acquire memory barrier here */
+	(void)isc_refcount_current(&handle->references);
 
 	sock = handle->sock;
 	handle->sock = NULL;