[LITMUS^RT] Base_task when executed does not give the correct debug output as rtspin does

[Björn Brandenburg]

> On 14. Mar 2018, at 06:38, Susan S <susanrosethomas2001 at gmail.com> wrote:
> 
> Hi,
> 
> Please do let me know why the st-trace-schedule output does not give the all the cpus actually used for the base_task.
> 
> Regards,
> Susan Rose.

Short answer: st-trace-schedule shows only tasks that are in the SCHED_LITMUS scheduling class (i.e., real-time tasks admitted by LITMUS^RT). 

Slightly longer answer: Your code calls fork in every *job* of the task. This is highly inefficient and not suitable for real-time tasks. Also, under most LITMUS^RT plugins, when a real-time task forks, the forked child is NOT automatically admitted as a LITMUS^RT task — you need to that explicitly from the parent task if you really want the child task to become a real-time task as well. The rationale for this behavior is that one could otherwise easily overload the system with accidental forks. 

However, for what you are trying to accomplish, you should definitely not fork in every job release. If you want tasks on all cores, you should launch the appropriate number of *sequential* tasks from a shell script. If you want a task with real-time threads, you should spawn the threads during initialization of the program, before entering real-time mode, and then transition each thread into real-time mode after it has migrated to the appropriate core. 

- Björn