Tested run/demo on nova: liquid_fb tried to call an invalid object

Norman Feske norman.feske at ...1...
Mon Jan 21 19:31:59 CET 2013

Hi Paul,

thanks for your feedback about running Genode with the park of your
machines. :-)

For accommodating older machines, you may give one of the other kernels
a try, i.e., OKL4.

Regarding NOVA, some of the stability glitches that you observed may
stem from the fact that dynamic system scenarios (scenarios where
programs are repeatedly started and stopped) are not yet fully supported
for base-nova. In fact, the official kernel version is not complete in
this respect. For this reason, there is currently rapid progress to
enable such work load. This involves us to complement the kernel with
prior missing functionality, adding support for destroying kernel
objects. So this issue is actively being worked on. If you are
interested in this line of work, please follow the branches created by
Alexander (https://github.com/alex-ab) at GitHub.

The messages "tried to call an invalid object:..." are not always a
reason to get worried. There are situations where they are actually
expected. For example, let us assume there is a program that enters a
main loop like this:

  static Timer::Connection timer;
  for (;;) {

The program will periodically wake up every 20ms, do some work, and
sleep again by doing an RPC call to the timer service. Now, when the
parent decides to kill the program (e.g., the user presses the X-button
on launchpad), the parent will close all the program's sessions in
reverse order as they had been created. So it will close the timer
session before closing the other basic sessions like CPU, RM, and PD.
After the parent closed the timer session, the main thread is still
running and may attempt just another call of 'timer.msleep(20)'. Because
the timer session does not exist anymore, you will see the message about
the attempt to call an invalid object.

Best regards

Dr.-Ing. Norman Feske
Genode Labs

http://www.genode-labs.com · http://genode.org

Genode Labs GmbH · Amtsgericht Dresden · HRB 28424 · Sitz Dresden
Geschäftsführer: Dr.-Ing. Norman Feske, Christian Helmuth

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