From 780efb246a6679f41ea988290bb2d916de16b23a Mon Sep 17 00:00:00 2001
From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Wed, 12 Jan 2022 16:39:30 +0100
Subject: [PATCH] dnsdist: Avoid a race if one is careless enough to call
 Rings::init() from two threads at once

---
 pdns/dnsdist-rings.cc | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pdns/dnsdist-rings.cc b/pdns/dnsdist-rings.cc
index fe35307922..6b044273a4 100644
--- a/pdns/dnsdist-rings.cc
+++ b/pdns/dnsdist-rings.cc
@@ -35,10 +35,9 @@ void Rings::setCapacity(size_t newCapacity, size_t numberOfShards)
 
 void Rings::init()
 {
-  if (d_initialized) {
+  if (d_initialized.exchange(true)) {
     throw std::runtime_error("Rings::init() should only be called once");
   }
-  d_initialized = true;
 
   if (d_numberOfShards <= 1) {
     d_nbLockTries = 0;
-- 
2.47.2