PFDEV Device busy

[sam wun]

Hi,

I know this is going to be difficult to help, anyway I'll give it a shoot to see if any can help me out...
I tried to incorporate DIOCADDRULE in this plugins by making 2 different changes:
 //rule.action = PF_CHANGE_GET_TICKET;
 rule.action = PF_RULESET_FILTER;
 //if(ioctl(pfdev, DIOCCHANGERULE, &rule)<0)
 if(ioctl(pfdev, DIOCADDRULE, &rule)<0)
 {
    snprintf(msg, sizeof(msg) - 1, "Error: DIOCADDRULE 1 (auto=1) : %s. PF plugin disabled.", strerror(errno));
    ....
 }

By executing the program, I got the following error message:
Error: DIOCADDRULE 1: Device busy. PF plugin disabled.

I m not sure how to debug this error. 
Any idea?

Thanks
Sam