novice question: unable to kldunload netgraph.ko

[Cheng Jin]

Hi,
 
I have started to play around with netgraph this weekend, and I am finding a very strange problem of not being able to kldunload any of the ng*.ko modules, as well
as netgraph.ko itself.
 
I tried on two systems running 5.4-RELEASE and 7.0-RELEASE, and the result is the same.  On both systems, I compiled netgraph after the main kernel compilation by specifying netgraph on the MODULES_OVERRIDE line in /etc/make.conf.  Not sure if I left some component that netgraph depends on inside the kernel?
 
I have tried the following with regard to netgraph.ko on both systems.
 
1. plain kldload and following by kldunload.  The error message is device busy.
 
2. sitting in front of the console with no active network connections, i brought down all ethernet interfaces, tried kldunload, same device busy error.  I tried on a freshly booted system, same problem.
 
3. in front of the console, brought down all ethernet interfaces, tried kldload followed by kldunload.  Same problem.
 
I think at some point, I didnt get the device-busy error message with kldunload, but netgraph.ko wasnt unloaded either.
 
I tried googling around and looked through all the netgraph related man pages and netgraph related examples, and it seems that I am the only one having this problem so I wonder if there was something really simple thing that I overlooked?
 
Thanks,
 
Cheng
 
---
 
On the 5.4 system, kldstat shows the following once netgraph.ko is loaded.  It has three ethernet interfaces bge0, bge1, and em0
 
Id Refs Address    Size     Name
 1    4 0xc0400000 4dd4a8   kernel
 2    1 0xc08de000 6d90     dummynet.ko
 3    1 0xc2a79000 12000    netgraph.ko
 
On the 7.0 system with fxp0 and em0
 
Id Refs Address            Size     Name
 1    2 0xffffffff80100000 5e4560   kernel
 2    1 0xffffffffc221c000 87d4     netgraph.ko
 
If I try to look at details with ngctl, it loads ng_socket.ko, which only makes the unloading problem harder!  Not sure why the ref count is 1 almost right away.