[LITMUS^RT] [starting LITMUS]

[Björn Brandenburg]

> On 28 May 2015, at 04:34, Dhanny R <dhanker2626 at gmail.com> wrote:
> 
> hello, 
> i just finish install LITMUS^RT n patch liblitmus n ft_tools too, and i want to starting my experiment.
> 
> using ubuntu 12.04LTS 64bit, Xen 4.5, kernel 3.10.41 pyGRUB V0.6 
> 
> i'm following the instruction from :
> https://wiki.litmus-rt.org/litmus/UserspaceTools
> 
> when starting "setched" the dialog box show the choice of Plugin, and when i choose one of them like "PSN-EDF" the command show error message :
> 
> Error: Cannot write to /proc/litmus/active_plugin. Do you have root privileges?
> Error: Setting new plugin failed.
> Are there any active real-time tasks?
> 
> i'm in root, 
> 
> my question are : 
> 
> 1. did i missing something before using setched?

If you are running a LITMUS^RT kernel, the steps you mentioned should work.

> 2. what the 1st i must do or setting before this step?

Hard to say. It should work out of the box, and we’ve not seen any problems surrounding plugin activation in quite a while. 

What’s the output of the following commands?

1) ls -lR /proc/litmus

2) cat /proc/litmus/plugins/loaded

3) echo PSN-EDF > /proc/litmus/active_plugin; cat /proc/litmus/active_plugin

If step 3 fails, are there any debug messages in the kernel log?

4) setsched Linux; setsched GSN-EDF; setsched Linux; setsched PSN-EDF

> 3. when i want to write my coding in base_mt_task, the message error are :
> 
> ~/liblitmus# ./base_mt_task
> RT Thread 0 active.
> init_rt_thread() ok.
> set_rt_task_param(gettid(), &param) ok.
> [  387.033665] LITMUS^RT: Linux plugin rejects base_mt_task/1605.
> task_mode(LITMUS_RT_TASK) failed: Invalid argument

That’s expected. It just means that you cannot run a real-time task until you’ve configured a valid real-time scheduling policy. The “Linux” plugin serves as a dummy plugin and simply rejects all tasks during admission control.

- Björn