avoid race in trace messages regarding pending count

1 files changed, 6 insertions, 3 deletions

diff --git a/messagebus/src/vespa/messagebus/sourcesession.cpp b/messagebus/src/vespa/messagebus/sourcesession.cpp
index 0cf7135a1db..d4440b60895 100644
--- a/messagebus/src/vespa/messagebus/sourcesession.cpp
+++ b/messagebus/src/vespa/messagebus/sourcesession.cpp
@@ -75,6 +75,7 @@ SourceSession::send(Message::UP msg)
     if (msg->getTimeRemaining() == 0ms) {
         msg->setTimeRemaining(_timeout);
     }
+    uint32_t my_pending_count = 0;
     {
         std::lock_guard guard(_lock);
         if (_closed) {
@@ -89,12 +90,12 @@ SourceSession::send(Message::UP msg)
         if (_throttlePolicy) {
             _throttlePolicy->processMessage(*msg);
         }
-        ++_pendingCount;
+        my_pending_count = ++_pendingCount;
     }
     if (msg->getTrace().shouldTrace(TraceLevel::COMPONENT)) {
         msg->getTrace().trace(TraceLevel::COMPONENT,
                               make_string("Source session accepted a %d byte message. %d message(s) now pending.",
-                                          msg->getApproxSize(), _pendingCount));
+                                          msg->getApproxSize(), my_pending_count));
     }
     msg->pushHandler(*this);
     _sequencer.handleMessage(std::move(msg));
@@ -105,6 +106,7 @@ void
 SourceSession::handleReply(Reply::UP reply)
 {
     bool done;
+    uint32_t my_pending_count = 0;
     {
         std::lock_guard guard(_lock);
         assert(_pendingCount > 0);
@@ -112,11 +114,12 @@ SourceSession::handleReply(Reply::UP reply)
         if (_throttlePolicy) {
             _throttlePolicy->processReply(*reply);
         }
+        my_pending_count = _pendingCount;
         done = (_closed && _pendingCount == 0);
     }
     if (reply->getTrace().shouldTrace(TraceLevel::COMPONENT)) {
         reply->getTrace().trace(TraceLevel::COMPONENT,
-                                make_string("Source session received reply. %d message(s) now pending.", _pendingCount));
+                                make_string("Source session received reply. %d message(s) now pending.", my_pending_count));
     }
     IReplyHandler &handler = reply->getCallStack().pop(*reply);
     handler.handleReply(std::move(reply));