From f41bee4766077b89957032ea329d642342017a54 Mon Sep 17 00:00:00 2001
From: Otto Moerbeek <otto.moerbeek@open-xchange.com>
Date: Wed, 6 Nov 2019 11:15:30 +0100
Subject: [PATCH] Avoid mthread race when using the set of rootNSZones.

---
 pdns/reczones.cc | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/pdns/reczones.cc b/pdns/reczones.cc
index 505a18402e..98a34b9bea 100644
--- a/pdns/reczones.cc
+++ b/pdns/reczones.cc
@@ -126,7 +126,11 @@ void primeRootNSZones(bool dnssecmode)
     sr.setDoDNSSEC(true);
     sr.setDNSSECValidationRequested(true);
   }
-  for (const auto & qname: t_rootNSZones) {
+
+  // beginResolve() can yield to another mthread that could trigger t_rootNSZones updates,
+  // so make a local copy
+  set<DNSName> copy(t_rootNSZones);  
+  for (const auto & qname: copy) {
     t_RC->doWipeCache(qname, false, QType::NS);
     vector<DNSRecord> ret;
     sr.beginResolve(qname, QType(QType::NS), QClass::IN, ret);
-- 
2.47.2