From: Otto <otto.moerbeek@open-xchange.com>
Date: Wed, 27 Jan 2021 12:36:55 +0000 (+0100)
Subject: Fix race in registerAllStats() by making sure it only returns if the map
X-Git-Tag: dnsdist-1.6.0-alpha2~47^2~2
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=bfddf1e55e9b78cc34935aeccb68e87ae2b7229d;p=thirdparty%2Fpdns.git

Fix race in registerAllStats() by making sure it only returns if the map
has been fully initialized. If another thread is busy initing, we wait a bit.
So it's safe to call getAllStatsMap() after registerAllStats() returns.
Fixes #10021
---

diff --git a/pdns/rec_channel_rec.cc b/pdns/rec_channel_rec.cc
index dce7a12fe5..72192b2b90 100644
--- a/pdns/rec_channel_rec.cc
+++ b/pdns/rec_channel_rec.cc
@@ -1041,9 +1041,14 @@ extern ResponseStats g_rs;
 
 void registerAllStats()
 {
-  static std::atomic_flag s_init = ATOMIC_FLAG_INIT;
-  if(s_init.test_and_set())
+  static std::mutex s_lock;
+  static bool s_inited = false;
+
+  std::lock_guard<std::mutex> lock(s_lock);
+
+  if (s_inited) {
     return;
+  }
 
   addGetStat("questions", &g_stats.qcounter);
   addGetStat("ipv6-questions", &g_stats.ipv6qcounter);
@@ -1247,6 +1252,8 @@ void registerAllStats()
     const std::string name = "ecs-v6-response-bits-" + std::to_string(idx + 1);
     addGetStat(name, &(SyncRes::s_ecsResponsesBySubnetSize6.at(idx)));
   }
+  
+  s_inited = true;
 }
 
 void doExitGeneric(bool nicely)
diff --git a/pdns/ws-recursor.cc b/pdns/ws-recursor.cc
index 6481c7cbd4..a6760bc3c8 100644
--- a/pdns/ws-recursor.cc
+++ b/pdns/ws-recursor.cc
@@ -984,7 +984,6 @@ RecursorWebServer::RecursorWebServer(FDMultiplexer* fdm)
   registerAllStats();
 
 #if CHECK_PROMETHEUS_METRICS
-  // There is a race here if another thread already called registerAllStats(); but it is not ready yet
   validatePrometheusMetrics();
 #endif