MDEV-5804: If same GTID is received on multiple master connections in multi-source replication, the event is double-executed causing corruption or replication failure

Some fixes, mainly to make it work in non-parallel replication mode also
(--slave-parallel-threads=0).

Patch should be fairly complete now.

1 files changed, 1 insertions, 5 deletions

diff --git a/sql/sys_vars.cc b/sql/sys_vars.cc
index 8aa202b381b..c9f1055d17a 100644
--- a/sql/sys_vars.cc
+++ b/sql/sys_vars.cc
@@ -1839,18 +1839,14 @@ static bool
 fix_gtid_ignore_duplicates(sys_var *self, THD *thd, enum_var_type type)
 {
   bool running;
-  bool err= false;
 
   mysql_mutex_unlock(&LOCK_global_system_variables);
   mysql_mutex_lock(&LOCK_active_mi);
   running= master_info_index->give_error_if_slave_running();
   mysql_mutex_unlock(&LOCK_active_mi);
-  if (running)
-    err= true;
   mysql_mutex_lock(&LOCK_global_system_variables);
 
-  /* ToDo: Isn't there a race here? I need to change the variable only under the LOCK_active_mi, and only if running is false. */
-  return err;
+  return running ? true : false;
 }