CS3 Operating Systems 2013-14, Practical Exercise.

PHASE 3
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The assessed submission for this practical comprises three
installments.

Part 1
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In the directory
/group/teaching/cs3/os/Modules
which you should already have copied into your shared directory,
you will find a module  worker.c  .
This module starts a new kernel thread (i.e. a thread running in
kernel space), which just prints a message every ten seconds.
When it is  rmmod'ed,  it asks the kernel thread to terminate.

You should note the use of a wait queue (basically a semaphore)
to achieve synchronization between rmmod and the kernel thread.
Since the kernel thread is running code from the module, the
thread should terminate before the module is unloaded! Hence
the cleanup_module() routine (which is called before the module is
unloaded) sets a shared flag to ask the kernel thread to terminate,
and then waits until the thread signals to the wait queue (semaphore)
that it has finished.

Thus the expected behaviour is:
  insmod worker.ko
and then get a greeting, followed by a message every ten seconds.
When you do
  rmmod worker
there will be a delay of up to ten seconds before the thread
terminates and the module is removed.

The first part of the assessment simply asks you to verify this.

First, verify that you can compile and run the module, with the
behaviour described above.

Now copy worker.c  to  worker1.c, and adjust the Makefile accordingly.
Edit the messages in worker1.c to something different, preferably
including something unique and witty (but not your name, please).
Compile the module, and then
  insmod worker1.ko
wait for 30 seconds or so, and
  rmmod worker1

Then capture the output of the dmesg command into a file in your
shared directory, e.g. by
  dmesg >/mnt/shared/part1-output .
(For safety, unmount or shut down the VM before assuming that any
files written to your home directory are actually there!)

You should now submit this file using the command
submit os 1 part1-output
(You may re-submit at any time up to the practical deadline.)

That is the end of part 1; it is trivial, but it assures you that
you have successfully understood how to use UML and modules.

Successful completion of this part instantly gets you 30% of the
practical marks!