Invalidate bmqu::SharedResource<DomainManager> self explicitly

Signed-off-by: Emelia Lei <[email protected]>

src/groups/mqb/mqba/mqba_domainmanager.cpp

@@ -566,17 +566,21 @@ void DomainManager::stop()
                        << k_MAX_WAIT_SECONDS_AT_SHUTDOWN
                        << " seconds while shutting down"
                        << " bmqbrkr. rc:  " << rc << ".";
-
-        // Note that 'self' variable will get invalidated when this function
-        // returns, which will ensure that any pending 'onDomainClosed'
-        // callbacks are not invoked.  So there is no need to explicitly call
-        // 'self.invalidate()' here.
     }
 
     if (d_domainResolver_mp) {
         d_domainResolver_mp->stop();
         d_domainResolver_mp.clear();
     }
+
+    // Notice that this invalidation is necessary.
+    // Without this explicit call, `self` will be invalidated
+    // when the function returns, which will ensure that any pending
+    // `onDomainClosed` callbacks are not invoked. But this is not enough
+    // since we want to prevent a (tiny) possibility where `latch` is
+    // destructed before `self` and `onDomainClosed` would be called on an
+    // invalid `latch`.
+    self.invalidate();
 }
 
 int DomainManager::locateDomain(DomainSp*          domain,
@@ -769,8 +773,12 @@ int DomainManager::processCommand(mqbcmd::DomainsResult*        result,
                 BALL_LOG_ERROR << "DOMAINS REMOVE fail to finish in "
                                << k_MAX_WAIT_SECONDS_AT_DOMAIN_REMOVE
                                << " seconds. rc:  " << rc << ".";
-                return rc;
             }
+
+            // Refer to `DomainManager::stop` to see why we need to invalidate
+            // `self` explicitly.
+            self.invalidate();
+            return rc;  // RETURN
         }
         // Second pass
         else {
@@ -807,8 +815,6 @@ int DomainManager::processCommand(mqbcmd::DomainsResult*        result,
             result->makeSuccess();
             return 0;  // RETURN
         }
-
-        return 0;
     }
 
     bmqu::MemOutStream os;