problem in upgrade from 5.0.22(mysql) to 5.5.21(percona)

[justlooks]

yesterday i try to upgrade my DB from mysql5.0.22 to percona5.5.21
first i backup the data,and remove mysql5.0.22,install percona5.5.21,after start up ,i run mysql_upgrade to update system table,but failed

trade_lead_bak.trade1 OK
Running ‘mysql_fix_privilege_tables’…
ERROR 1370 (42000) at line 1111: alter routine command denied to user ‘root’@‘localhost’ for routine ‘mysql.die’
ERROR 1044 (42000) at line 1112: Access denied for user ‘root’@‘localhost’ to database ‘mysql’
ERROR 1370 (42000) at line 1125: alter routine command denied to user ‘root’@‘localhost’ for routine ‘mysql.die’
FATAL ERROR: Upgrade failed

but root@localhost can visit mysql,why???

mysql> use mysql
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed

i try this but failed

mysql> create procedure mysql.die() signal sqlstate ‘HY000’ set message_text=‘Unexpected content found in the performance_schema database.’;
ERROR 1044 (42000): Access denied for user ‘root’@‘localhost’ to database ‘mysql’

[xaprb]

You may have anonymous user accounts in your database. Connect again and type SHOW GRANTS. Note whom it reports the grants are given to!

[justlooks]

the reason is root user has no privileges of create routine
and question is how can root user grant privileges which he is not own ??

ok i figured it out, start mysql with --skip-grant-tables,then
reset the privileges

mysql> select * from mysql.user where user=‘root’\G
*************************** 1. row ***************************
Host: localhost
User: root
Password: 134c99b462c6a90b
Select_priv: Y
Insert_priv: Y
Update_priv: Y
Delete_priv: Y
Create_priv: Y
Drop_priv: Y
Reload_priv: Y
Shutdown_priv: Y
Process_priv: Y
File_priv: Y
Grant_priv: Y
References_priv: Y
Index_priv: Y
Alter_priv: Y
Show_db_priv: Y
Super_priv: Y
Create_tmp_table_priv: Y
Lock_tables_priv: Y
Execute_priv: Y
Repl_slave_priv: Y
Repl_client_priv: Y
Create_view_priv:
Show_view_priv:
Create_routine_priv:
Alter_routine_priv:
Create_user_priv:
Event_priv: Y
Trigger_priv: Y
Create_tablespace_priv: Y
ssl_type:
ssl_cipher: 0
x509_issuer:
x509_subject:
max_questions: 0
max_updates: 0
max_connections: 0
max_user_connections: 0
plugin:
authentication_string: NULL

mysql> grant all on . to ‘root’@‘localhost’;
ERROR 1045 (28000): Access denied for user ‘root’@‘localhost’ (using password: NO)