A follow-up for 5.5 version of fix for bug#54360 "Deadlock

DROP/ALTER/CREATE DATABASE with open HANDLER".

Remove wait_for_condition() which became unused after 
database locks were replaced with MDL scoped locks.
If one needs functionality provided by this call one can 
always use THD::enter_cond()/exit_cond() methods.

Also removed an unused include from sql_db.cc and updated 
comment describing one of used includes to reflect current
situation.

sql/sql_base.cc

@@ -2412,51 +2412,6 @@ void drop_open_table(THD *thd, TABLE *table, const char *db_name,
 }
 
 
-/*
-   Wait for condition but allow the user to send a kill to mysqld
-
-   SYNOPSIS
-     wait_for_condition()
-     thd	Thread handler
-     mutex	mutex that is currently hold that is associated with condition
-	        Will be unlocked on return     
-     cond	Condition to wait for
-*/
-
-void wait_for_condition(THD *thd, mysql_mutex_t *mutex, mysql_cond_t *cond)
-{
-  /* Wait until the current table is up to date */
-  const char *proc_info;
-  thd->mysys_var->current_mutex= mutex;
-  thd->mysys_var->current_cond= cond;
-  proc_info=thd->proc_info;
-  thd_proc_info(thd, "Waiting for table");
-  DBUG_ENTER("wait_for_condition");
-  DEBUG_SYNC(thd, "waiting_for_table");
-  if (!thd->killed)
-    mysql_cond_wait(cond, mutex);
-
-  /*
-    We must unlock mutex first to avoid deadlock becasue conditions are
-    sent to this thread by doing locks in the following order:
-    lock(mysys_var->mutex)
-    lock(mysys_var->current_mutex)
-
-    One by effect of this that one can only use wait_for_condition with
-    condition variables that are guranteed to not disapper (freed) even if this
-    mutex is unlocked
-  */
-    
-  mysql_mutex_unlock(mutex);
-  mysql_mutex_lock(&thd->mysys_var->mutex);
-  thd->mysys_var->current_mutex= 0;
-  thd->mysys_var->current_cond= 0;
-  thd_proc_info(thd, proc_info);
-  mysql_mutex_unlock(&thd->mysys_var->mutex);
-  DBUG_VOID_RETURN;
-}
-
-
 /**
     Check that table exists in table definition cache, on disk
     or in some storage engine.

sql/sql_base.h

@@ -203,8 +203,6 @@ int setup_conds(THD *thd, TABLE_LIST *tables, TABLE_LIST *leaves,
 		COND **conds);
 int setup_ftfuncs(SELECT_LEX* select);
 int init_ftfuncs(THD *thd, SELECT_LEX* select, bool no_order);
-void wait_for_condition(THD *thd, mysql_mutex_t *mutex,
-                        mysql_cond_t *cond);
 bool lock_table_names(THD *thd, TABLE_LIST *table_list,
                       TABLE_LIST *table_list_end, ulong lock_wait_timeout,
                       uint flags);

sql/sql_db.cc

@@ -21,14 +21,12 @@
 #include "unireg.h"
 #include "sql_db.h"
 #include "sql_cache.h"                   // query_cache_*
-#include "lock.h"                        // wait_if_global_read_lock,
-                                         // start_waiting_global_read_lock
+#include "lock.h"                        // lock_schema_name
 #include "sql_table.h"                   // build_table_filename,
                                          // filename_to_tablename
 #include "sql_rename.h"                  // mysql_rename_tables
 #include "sql_acl.h"                     // SELECT_ACL, DB_ACLS,
                                          // acl_get, check_grant_db
-#include "sql_base.h"                    // wait_for_condition
 #include "log_event.h"                   // Query_log_event
 #include <mysys_err.h>
 #include "sp.h"