MDEV-18353 Shutdown may miss to wait for connection thread

* count CONNECT objects too
* wait for all CONNECT objects to disappear (to be converted to THDs)
  before killing THDs away

1 files changed, 12 insertions, 3 deletions

diff --git a/sql/sql_connect.cc b/sql/sql_connect.cc
index 4d09dab392b..733d281efd5 100644
--- a/sql/sql_connect.cc
+++ b/sql/sql_connect.cc
@@ -1360,6 +1360,14 @@ void do_handle_one_connection(CONNECT *connect)
     return;
   }
 
+  DBUG_EXECUTE_IF("CONNECT_wait",
+  {
+    extern MYSQL_SOCKET unix_sock;
+    DBUG_ASSERT(unix_sock.fd >= 0);
+    while (unix_sock.fd >= 0)
+      my_sleep(1000);
+  });
+
   /*
     If a thread was created to handle this connection:
     increment slow_launch_threads counter if it took more than
@@ -1373,10 +1381,10 @@ void do_handle_one_connection(CONNECT *connect)
     if (launch_time >= slow_launch_time*1000000L)
       statistic_increment(slow_launch_threads, &LOCK_status);
   }
-  delete connect;
 
-  /* Make THD visible in show processlist */
-  server_threads.insert(thd);
+  server_threads.insert(thd); // Make THD visible in show processlist
+
+  delete connect; // must be after server_threads.insert, see close_connections()
   
   thd->thr_create_utime= thr_create_utime;
   /* We need to set this because of time_out_user_resource_limits */
@@ -1482,6 +1490,7 @@ CONNECT::~CONNECT()
 {
   if (vio)
     vio_delete(vio);
+  count--;
 }