temporary commit - need to pull Monty's changes

mysql-test/t/rpl000001.test:
  modified test to break current replicatioin on a large log with a large lag 
  in slave thread between append and read of the relay log
mysys/mf_iocache.c:
  fixed one bug in IO_CACHE but there is another one not fixed yet
sql/slave.cc:
  fixed bug in 3.23 master replication

mysql-test/t/rpl000001.test

@@ -27,21 +27,38 @@ sync_with_master;
 connection master;
 reset master;
 connection slave;
+slave stop;
 reset slave;
 
 connection master;
 drop table if exists t1,t2;
 create table t1(n int);
-let $1=10;
+#we want the log to exceed 16K to test deal with the log that is bigger than
+#IO_SIZE
+let $1=5000;
+disable_query_log;
 while ($1)
 {
- eval insert into t1 values($1);
+ eval insert into t1 values($1+get_lock("hold_slave",10)*0);
  dec $1;
 }
+enable_query_log;
+
+#try to cause a large relay log lag on the slave 
+connection slave;
+select get_lock("hold_slave",10);
+slave start;
+#hope this is long enough for I/O thread to fetch over 16K relay log data
+sleep 1;
+select release_lock("hold_slave");
+unlock tables;
+
+connection master;
 create table t2(id int);
 insert into t2 values(connection_id());
 save_master_pos;
 
+
 connection master1;
 #avoid generating result
 create temporary table t1_temp(n int);
@@ -60,7 +77,7 @@ reap;
 connection slave;
 sync_with_master ;
 #give the slave a chance to exit
-sleep 0.5;
+wait_for_slave_to_stop;
 
 # The following test can't be done because the result of Pos will differ
 # on different computers

mysys/mf_iocache.c

@@ -823,6 +823,7 @@ int my_b_append(register IO_CACHE *info, const byte *Buffer, uint Count)
     }
     Count-=length;
     Buffer+=length;
+    info->end_of_file+=length;
   }
 
 end:

sql/slave.cc

@@ -1999,7 +1999,7 @@ static int queue_old_event(MASTER_INFO* mi, const char* buf,
     mi->master_log_pos += event_len;
   if (unlikely(processed_stop_event))
     mi->ignore_stop_event=1;
-  pthread_mutex_lock(&mi->data_lock);
+  pthread_mutex_unlock(&mi->data_lock);
   return 0;
 }