debug bpha

[Hua Qin <qinhua@xxxxxxxxxxxxxxxxxxxxx>]

The "bpha" command is not working properly on my building kernel. so I
just want to know where is the code I should look at.

The problem is I set breakpoint "ip_defrag" by using bpha, and then send
bigger packets to this machine. The ip_defrag should be caught and the
machine should drop to kdb, but nothing happened. If I use "bp" command,
it can drop to the kdb on the break point.

I did some debug, it seems "do_debug" (traps.c) was not be called by using
"bpha".
Does someone know a little bit deeper, how "do_debug" be called ?

Thanks!
Hua