Shrinking LDF File - Query Running Indefinitely

My intention is to include a sql job to schedule for shrinking log files to half of its original log file size (if half of their original size is greater than 5MB)

The code is below. But while executing the code it is keeps on running indefinitely. can somebody throw some light what cause it to go into an indefinite loop.

Thanks
Babu

code:
====
DECLARE db_file_name CURSOR FOR
SELECT name , ceiling(size/128.0) * 0.5
FROM master..sysaltfiles
Where rtrim(lower(filename)) like '%.ldf'

DECLARE @f_name varchar(128), @new_f_size int

OPEN db_file_name
FETCH NEXT FROM db_file_name INTO @f_name,@new_f_size
WHILE @@FETCH_STATUS = 0
BEGIN
If ( @new_f_size > 5)
BEGIN
DBCC SHRINKFILE ( @f_name, @new_f_size )
FETCH NEXT FROM db_file_name INTO @f_name,@new_f_size
END
END
CLOSE db_file_name
deallocate db_file_name