here's a simple procedure that reproduces this problem my sparc1:

run a -current kernel with a lengthy printf() added to
the beginning of your favorite system call (I used chroot()).
then do:

perl -e 'for(;;) { print "foofoofoofoofoofoofoofoofoofoofoofoo\n"; $q = "/tmp"; syscall(61, $q); }'

the crazy interrupts panic happens almost immediately.

-Chuck