From 3fbea485bd3a4997362a5927337cdb558ae3e5a9 Mon Sep 17 00:00:00 2001
From: Remi Gacogne <remi.gacogne@powerdns.com>
Date: Wed, 19 Oct 2022 22:23:01 +0200
Subject: [PATCH] dnsdist: Suppress a TSAN report about a TCP latency-related
 race

The race is real but we do not care much as this is only to provide
a rough metric.
---
 pdns/dnsdist.hh                            | 7 +++++++
 pdns/dnsdistdist/dnsdist-nghttp2.cc        | 2 +-
 pdns/dnsdistdist/dnsdist-tcp-downstream.cc | 2 +-
 pdns/dnsdistdist/dnsdist-tsan.supp         | 1 +
 4 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/pdns/dnsdist.hh b/pdns/dnsdist.hh
index adc7e5c9b1..7b8a0d2212 100644
--- a/pdns/dnsdist.hh
+++ b/pdns/dnsdist.hh
@@ -914,12 +914,14 @@ public:
     upStatus = newStatus;
     if (!upStatus) {
       latencyUsec = 0.0;
+      latencyUsecTCP = 0.0;
     }
   }
   void setDown()
   {
     d_config.availability = Availability::Down;
     latencyUsec = 0.0;
+    latencyUsecTCP = 0.0;
   }
   void setAuto() {
     d_config.availability = Availability::Auto;
@@ -971,6 +973,11 @@ public:
     tcpAvgConnectionDuration = (99.0 * tcpAvgConnectionDuration / 100.0) + (durationMs / 100.0);
   }
 
+  void updateTCPLatency(double udiff)
+  {
+    latencyUsecTCP = (127.0 * latencyUsecTCP / 128.0) + udiff / 128.0;
+  }
+
   void incQueriesCount()
   {
     ++queries;
diff --git a/pdns/dnsdistdist/dnsdist-nghttp2.cc b/pdns/dnsdistdist/dnsdist-nghttp2.cc
index 4288dc95a0..f9311b8da2 100644
--- a/pdns/dnsdistdist/dnsdist-nghttp2.cc
+++ b/pdns/dnsdistdist/dnsdist-nghttp2.cc
@@ -137,7 +137,7 @@ void DoHConnectionToBackend::handleResponse(PendingRequest&& request)
   try {
     if (!d_healthCheckQuery) {
       const double udiff = request.d_query.d_idstate.sentTime.udiff();
-      d_ds->latencyUsecTCP = (127.0 * d_ds->latencyUsecTCP / 128.0) + udiff / 128.0;
+      d_ds->updateTCPLatency(udiff);
     }
 
     request.d_sender->handleResponse(now, TCPResponse(std::move(request.d_buffer), std::move(request.d_query.d_idstate), shared_from_this()));
diff --git a/pdns/dnsdistdist/dnsdist-tcp-downstream.cc b/pdns/dnsdistdist/dnsdist-tcp-downstream.cc
index 72809fbbe7..eb8d8f45e6 100644
--- a/pdns/dnsdistdist/dnsdist-tcp-downstream.cc
+++ b/pdns/dnsdistdist/dnsdist-tcp-downstream.cc
@@ -668,7 +668,7 @@ IOState TCPConnectionToBackend::handleResponse(std::shared_ptr<TCPConnectionToBa
   --conn->d_ds->outstanding;
   auto ids = std::move(it->second.d_query.d_idstate);
   const double udiff = ids.sentTime.udiff();
-  conn->d_ds->latencyUsecTCP = (127.0 * conn->d_ds->latencyUsecTCP / 128.0) + udiff / 128.0;
+  conn->d_ds->updateTCPLatency(udiff);
 
   d_pendingResponses.erase(it);
   /* marking as idle for now, so we can accept new queries if our queues are empty */
diff --git a/pdns/dnsdistdist/dnsdist-tsan.supp b/pdns/dnsdistdist/dnsdist-tsan.supp
index e860b72b3e..f76eb6390e 100644
--- a/pdns/dnsdistdist/dnsdist-tsan.supp
+++ b/pdns/dnsdistdist/dnsdist-tsan.supp
@@ -5,6 +5,7 @@ race:updateTCPLatency
 race:handleStats
 race:ClientState::updateTCPMetrics
 race:DownstreamState::updateTCPMetrics
+race:DownstreamState::updateTCPLatency
 # There is a race when we update the status of a backend,
 # but eventual consistency is fine there
 race:DownstreamState::setDown
-- 
2.47.2