Re: Multi-seat X crashes

[Erik W. <om...@vc...>]

Hugo Vanwoerkom wrote:
> The reason for the textconsole is if the crash is a
> kernel panic then that is where the last message will
> show up.
Of course.  But if it's corrupted by the other heads, I'm not sure
whether or not a panic message would even have showed up anyway.  OTOH
kgdb should give me even better results, if/when it happens again.

> I am still not clear on what exactly dies. Is anything
> still running?
> When the crash occurs, everything is dead?
It varies.  The most extreme crash is where everything just locks
exactly where it is, with some heads sleeping and others with a mouse on
its way to some menu somewhere on the screen, whatever is going on.  In
these cases the machine ceases to respond to pings, and I have to
hard-reset the box.

Other cases involve a single head going black, and even shutting down
the CRTC completely.  Yesterday I was actively using one of the heads
and it blanked out from underneath me, then the LCD switched to
displaying "No Cable Attached"...  Thing is, the rest of the machine was
working properly, to the point of the other heads going to sleep and
waking up as expected, before I rebooted the machine later.

Sometimes I get one or more of the heads blanking a la DPMS, the never
waking up, while the machine is otherwise working just fine.
Periodically in this situation attempting to wake a display by moving
the mouse or hitting a key will trigger a *complete* crash a la the
first paragraph above.

And of course once I put a kgdb kernel on the machine, and switched to
xserver-xorg-dbg-6.8.2-1ubuntu, it ran for many hours operating just
fine.  Classic Heisenbug.  I'll be hammering on it continuously for the
remainder of the next two weeks, and if running a debug X server
"solves" the problem, so be it.  I'll have more time to *really* solve
the problem once I get back.