rmmod of ipv6 is not working.Help!

[Sharmila <shard@intoto.com>]

Hi all,	
	When I try to unload the ipv6 module from my Linux(kernel version 
2.4.18-14) PC using
rmmod ipv6 ,it is giving the following message:

"Device or resource busy"

lsmod shows ipv6 under modules but the "used by " shows -1.
Why is it like this?Is it expected?If so, how should I unload ipv6 module? 
Is "reboot" the only option we are left with?
Please let me know the info.

Thanks in advance,
Sharmila