Always call mysql_cond_broadcast(&rli->data_cond) under data_lock

This is a safetly fix to try to fix random failures in
parallel_backup_xa_debug reported as:
sync_slave_with_master failed:
'select master_pos_wait('master-bin.000001', 1034, 300, '')' returned -1

One possible reason could be lost signals, which this patch fixes.

Author: montywi

sql/rpl_parallel.cc

@@ -124,8 +124,8 @@ handle_queued_pos_update(THD *thd, rpl_parallel_thread::queued_event *qev)
   else if (cmp == 0
            && rli->group_master_log_pos < qev->future_event_master_log_pos)
     rli->group_master_log_pos= qev->future_event_master_log_pos;
-  mysql_mutex_unlock(&rli->data_lock);
   mysql_cond_broadcast(&rli->data_cond);
+  mysql_mutex_unlock(&rli->data_lock);
 }
 
 

sql/slave.cc

@@ -5897,9 +5897,9 @@ pthread_handler_t handle_slave_sql(void *arg)
   rli->relay_log.description_event_for_exec= 0;
   rli->reset_inuse_relaylog();
   /* Wake up master_pos_wait() */
-  mysql_mutex_unlock(&rli->data_lock);
   DBUG_PRINT("info",("Signaling possibly waiting master_pos_wait() functions"));
   mysql_cond_broadcast(&rli->data_cond);
+  mysql_mutex_unlock(&rli->data_lock);
   rli->ignore_log_space_limit= 0; /* don't need any lock */
   /* we die so won't remember charset - re-update them on next thread start */
   thd->system_thread_info.rpl_sql_info->cached_charset_invalidate();