Andrew Doran writes:
| If you are running amd64 you'll need to compile the kernel with
| -fno-omit-frame-pointer. LOCKDEBUG and DIAGNOSTIC will help to track down
| the problem.

Actually DIAGNOSTIC triggered an assert:
mutex_owned(&l->l_swaplock) failed: file uvm/uvm_glue.c, line 482

I see that the last commit in this file is dated from Aug 18, which is
more or less the date at which I started to have trouble...
 
Since my kernel panic'ed, I was not able to use my keyboard to type
anything in ddb (it was still attached to the X session). I was able to
see the panic message by switching to VT1 before the panic.
Of course I have no serial line on this machine to run kgdb.

Any idea ? :)

-- Anthony