How do I put this?

512mb PPC Ti500, head of 1.5 userland, currentish kernel from ~apr 30, 
tmpfs.

When running constant builds (FSF toolchain code) I'm noticing that an 
SH process occasionally gets stuck chewing up CPU time.

First few times this happend, I tried killing the SH process but with 
tragic consequences - the machine locked up.

The most recent time this happened I decided it is likely better to just 
reboot the machine.  So I started quitting everything and, to my 
suprize, quitting mozilla unwedged the SH process and my build resumed.

I guess the SH is busy waiting on some sort of resource that mozilla was 
hogging.  Any hints as to how to figure out what that resource is?

Andrew