SERVER-66130 Do not detach from the balancer worker thread on config server stepdown

1 files changed, 10 insertions, 8 deletions

diff --git a/src/mongo/db/s/balancer/balancer.cpp b/src/mongo/db/s/balancer/balancer.cpp
index 9710eae64c2..00923c6732a 100644
--- a/src/mongo/db/s/balancer/balancer.cpp
+++ b/src/mongo/db/s/balancer/balancer.cpp
@@ -293,11 +293,11 @@ void Balancer::initiateBalancer(OperationContext* opCtx) {
 
 void Balancer::interruptBalancer() {
     stdx::lock_guard<Latch> scopedLock(_mutex);
-    if (_state != kRunning)
+    if (_state != kRunning) {
         return;
+    }
 
     _state = kStopping;
-    _thread.detach();
 
     // Interrupt the balancer thread if it has been started. We are guaranteed that the operation
     // context of that thread is still alive, because we hold the balancer mutex.
@@ -312,8 +312,10 @@ void Balancer::interruptBalancer() {
 
 void Balancer::waitForBalancerToStop() {
     stdx::unique_lock<Latch> scopedLock(_mutex);
-
     _joinCond.wait(scopedLock, [this] { return _state == kStopped; });
+    if (_thread.joinable()) {
+        _thread.join();
+    }
 }
 
 void Balancer::joinCurrentRound(OperationContext* opCtx) {
@@ -612,12 +614,12 @@ void Balancer::_consumeActionStreamLoop() {
 
 void Balancer::_mainThread() {
     ON_BLOCK_EXIT([this] {
-        stdx::lock_guard<Latch> scopedLock(_mutex);
-
-        _state = kStopped;
+        {
+            stdx::lock_guard<Latch> scopedLock(_mutex);
+            _state = kStopped;
+            LOGV2_DEBUG(21855, 1, "Balancer thread terminated");
+        }
         _joinCond.notify_all();
-
-        LOGV2_DEBUG(21855, 1, "Balancer thread terminated");
     });
 
     Client::initThread("Balancer");