Fix for BUG#2921 "Replication problem on mutex lock in mySQL-4.0.18":

re-using unused LOCK_active_mi to serialize all administrative
commands related to replication:
START SLAVE, STOP SLAVE, RESET SLAVE, CHANGE MASTER, init_slave()
(replication autostart at server startup), end_slave() (replication
autostop at server shutdown), LOAD DATA FROM MASTER.
This protects us against a handful of deadlocks (like BUG#2921
when two START SLAVE, but when two STOP SLAVE too).
Removing unused variables.


sql/item_func.cc:
  We don't need LOCK_active_mi just to MASTER_POS_WAIT().
sql/repl_failsafe.cc:
  no need for macro
sql/set_var.cc:
  no need for macro
sql/slave.cc:
  Re-using unused LOCK_active_mi to serialize all administrative
  commands related to replication:
  START SLAVE, STOP SLAVE, RESET SLAVE, CHANGE MASTER, init_slave()
  (replication autostart at server startup), end_slave() (replication
  autostop at server shutdown), LOAD DATA FROM MASTER.
  This protects us against a handful of deadlocks.
  Removing unused variables.
sql/slave.h:
  Re-using LOCK_active_mi to serialize administrative replication commands.
  Macros unneeded. Removing unneeded variables.
sql/sql_parse.cc:
  found unused variable.
  Replacing macros.
sql/sql_show.cc:
  replacing macros

1 files changed, 0 insertions, 2 deletions

diff --git a/sql/item_func.cc b/sql/item_func.cc
index 656dff63609..ab96915e746 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -1543,13 +1543,11 @@ longlong Item_master_pos_wait::val_int()
   }
   longlong pos = args[1]->val_int();
   longlong timeout = (arg_count==3) ? args[2]->val_int() : 0 ;
-  LOCK_ACTIVE_MI;
   if ((event_count = active_mi->rli.wait_for_pos(thd, log_name, pos, timeout)) == -2)
   {
     null_value = 1;
     event_count=0;
   }
-  UNLOCK_ACTIVE_MI;
   return event_count;
 }