[ltp] Re: cannot resume after hotplugging an ultrabay battery in T61p

[Henrique de Moraes Holschuh]

On Mon, 16 Feb 2009, Marc MERLIN wrote:
> Were you able to find any config options that don't look good to you?

Sorry, no :(  But you have some heavy duty debugging stuff that you should
disable if you don't use them, like kprobes.  I'd also disable cgroup and
the group scheduler if you don't use them.

> Similarly, I have a nagging but annoying problem where my laptop will
> occasionally hard deadlock when I plug the power back in while it was
> running on batteries.

If you are using either nVidia or ATI proprietary drivers (sorry, I forgot
the details), they react to power management events like AC
connected/disconnected, and so I suppose a bug there might cause hangs.  If
it is a hard-to-hit race, the hangs would not happen very often.

I don't think the open drivers do this (i.e. they're not advanced enough for
that yet :p), though.  Maybe Intel's do, they're big on the PM stuff.  The
X.org server also wants to listen to acpi events nowadays (and does so,
probably through HAL), so it gets difficult to know for sure what might be
reacting to the AC connected event and causing a hang.

It could also be the BIOS fighting X.org.  Try telling the BIOS to not touch
the screen brightness level when you plug/unplug AC, and see if that stops
the hangs...

> I just upgraded to 2.6.28.4 so we'll see what happens, but if you have
> recommendations on kernel options, debugging, or other ideas, I'm all ears.
> (like can I debug on usb serial, or do I need real serial?)

No idea, sorry :(  Never tried it over serial, let alone usb-serial.  I'd
expect a real serial to work better, but the only way to know for sure is to
try.

There is a hideous hack to log data to the RTC (will scramble the time,
though, so it is not good if you cannot reproduce the problem easily as you
cannot really have that thing enabled all the time) that does work almost
always.

> > I take it that usb-serial won't work, but I think the docking station has
> > serial on it. I might be able to borrow one.
> > If I do and do serial console, would I get some output on that serial port
> > at resume time you think?

Here, when I last needed to use an ethernet console, it did work enough to
get the data.  But it was on 2.6.21 or thereabouts :(

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh