How to diagnose system freezes?

[Garrett Cooper]

On Tue, Jul 31, 2012 at 5:02 PM, Yuri <yuri at rawbw.com> wrote:
> One of my 9.1-BETA1 systems periodically freezes. If sound was playing, it
> would usually cycle with a very short period. And system stops being
> sensitive to keyboard/mouse. Also ping of this system doesn't get a
> response.
> I would normally think that this is the faulty memory. But memory was
> recently replaced and tested with memtest+ for hours both before and after
> freezes and it passes all tests.
> One out of the ordinary thing that is running on this system is nvidia
> driver. But the freezes happen even when there is no graphics activity.
> Another out of the ordinary thing is that the kernel is built for DTrace.
> But DTrace was never used in the sessions that had a freeze.
>
> What is the way to diagnose this problem?

    As an aside, where do you see things lockup (Xorg, Firefox, etc)?
Can you remain sshed into the box or not? What sound driver are you
using and how are you playing sound/video?
Thanks,
-Garrett