when to remount sysfs ?

[ishare]

 Hi:
   
   As i know , when kernel is  booting , sysfs is mounted at /sys before the real root fs is mounted .
  
   Then , after the real root fs is mounted , when does i need to remount sysfs at the new /sys location ?
  
   I know the devfs is remounted by do_mount ("none", "/dev", "devfs", 0, "") , so how is that for sysfs?

 Thanks!