Need help in figuring out how a scheduler is assigned to a task

[Sebastian Huber]

On 09/06/2020 08:18, Gedare Bloom wrote:

> Richi,
>
> On Mon, Jun 8, 2020 at 8:52 AM Sebastian Huber
> <sebastian.huber at embedded-brains.de> wrote:
>> On 08/06/2020 16:33, Richi Dubey wrote:
>>
>>> Thanks for telling me about the uniprocessor rule for having a single
>>> scheduler for all the tasks. It makes sense. However I still cannot
>>> find the code which actually links our processor to that scheduler!
>>> Talking on a high level, I cannot find a code anywhere that tells
>>> kernel/processor to use Simple scheduler for all the tasks when we
>>> write #define CONFIGURE_SCHEDULER_SIMPLE inside a testcase(I could not
>>> find anything related in the scheduler.h configuration file too). I
>>> hope my doubt makes sense.
>> Depending on the configuration options, the header file
>> <rtems/confdefs/scheduler.h> defines a couple of data structures. One is
>> the _Scheduler_Table:
>>
>> https://git.rtems.org/rtems/tree/cpukit/include/rtems/confdefs/scheduler.h#n239
>>
>> This is how the scheduler is defined for an application. You can look a
>> the preprocessed header file to see all the data structures.
>>
> You will need to learn some techniques for navigating a large code
> base. I don't know if there is a good tutorial out there, but check
> out information about:
> * ctags
> * cscope
> They can integrate with editors on *nix and provide you with
> identifier/name/text search in an indexed database built from a
> filesystem directory tree. Or you can use them from the command line
> also. This is the best way to find code definitions and to navigate
> code quickly. You can push/pop searches on a stack also, so you can
> easily follow a function's control flow down, and then backtrace up.
>
> UNIX utilities:
> * grep
> * ack (an updated variant of grep)
> * find

To get an overview of the control flow, you can also use 
-finstrument-functions combined with the Event Records:

https://docs.rtems.org/branches/master/user/tracing/eventrecording.html

With the data you can create a flame graph:

http://www.brendangregg.com/flamegraphs.html

It is not a five minute job to set this up.