How to find out what a process has been doing on a PPC-440 system

Hi,
   I have a list of processes running in a linux system (2.6.11 kernel).
One of the processes invokes send() system call and does not return.
The command "ps" shows that the process is in "RUNNING" state. With an ICE
I could dump each process structures and all the fields, but can't find a way to get the stack trace for each process. Not sure how contexts are saved on ppc-4xx kernel. It seems that they are saved in kernel stack. How do we
get the top of the stack from the task_struct pointers? How to find out
where in kernel send() blocks (not sleeping/scheduled)?

Kallol