Removed possible deadlock betwen LOCK_log and LOCK_global_system_variables

The lock order of the mutex must be LOCK_log followed by LOCK_global_system_variables as InnoDB can lock LOCK_global_system_variables during a transaction commit when LOCK_log is hold. Fix is to temporarly unlock LOCK_global_system_variables when setting global binlog variables that needs to use LOCK_log.

Author: montywi

sql/log.cc

@@ -3784,7 +3784,6 @@ void MYSQL_BIN_LOG::init_pthread_objects()
  mysql_cond_init(key_BINLOG_COND_binlog_background_thread_end,
  &COND_binlog_background_thread_end, 0);
 
- /* Fix correct mutex order to catch violations quicker (MDEV-35197). */
  mysql_mutex_record_order(&LOCK_log, &LOCK_global_system_variables);
 }
 

sql/sys_vars.cc

@@ -1847,9 +1847,8 @@ Sys_max_binlog_stmt_cache_size(
 
 static bool fix_max_binlog_size(sys_var *self, THD *thd, enum_var_type type)
 {
- ulong saved= max_binlog_size;
  mysql_mutex_unlock(&LOCK_global_system_variables);
- mysql_bin_log.set_max_size(saved);
+ mysql_bin_log.set_max_size(max_binlog_size);
  mysql_mutex_lock(&LOCK_global_system_variables);
  return false;
 }