Intermittent system hangs on 7.2-RELEASE-p1

[Linda Messerschmidt]

On Wed, Aug 26, 2009 at 4:42 PM, John Baldwin<jhb at freebsd.org> wrote:
> One thing to note is that ktrace only logs voluntary context switches (i.e.
> call to tsleep or waiting on a condition variable).  It specifically does not
> log preemptions or blocking on a mutex,

I was not aware, thanks.

> so in theory if your machine was
> livelocked temporarily that might explain this.

How would we determine that?

We are now able to reproduce this on a test machine, even after
slipping in a 7.2-STABLE kernel with KTR enabled.  So we have a lot
more options now.

Unfortunately, I don't really "get" KTR yet.  It looks like it has
relevant info, but I was unable to correlate its huge timestamps (e.g.
6795522404430562) to ktrace output times (e.g. 1251387606.225544)
showing problem areas.

What's my best bet from here?