Not able to get crash dump

Hi All, I have loaded the linux crashdump on ubuntu machine. I can manually generate the crashdump by the 'echo c > /proc/sysrq-trigger'. However, i am having a panic in a module i have written, which is not generating a core dump. I simply see the stack in the console and it kind of hangs there. I have to manually power it off and power it on ... Can someone explain why this happens? Is it because the kernel has gone into such a state that it cannot even follow the procedure for crash dump. Regards, Neha