[ECOS] Re: how to implement EDF scheduling in eCos

[Nodir Kodirov]

Hello John and all!

I think finally I got out of previous problem, facing another one...
But, John, I thank you very much, for being together all the time!

Now I have more interesting picture and one *puzzle*.
Let me explain picture first, next I will explain *puzzle*.

As the last time In ktypes.h I have:

> typedef cyg_count32     cyg_priority;   // priority value
> typedef struct cyg_edf_info_t
> {
>       cyg_count32 deadline;
>       cyg_count32 wcet;
>       cyg_count32 period;
> };

In kapidata.h I added:

> #elif defined(CYGSEM_KERNEL_SCHED_EDF)
> # define CYG_SCHEDTHREAD_SCHEDIMP_MEMBERS                                    \
>    cyg_thread *next;                                                        \
>    cyg_thread *prev;                                                        \
>    cyg_priority_t      priority;             /* current thread priority */  \
>    struct cyg_sched_edf_info_t *edf_info;                                     \
>    CYG_SCHEDTHREAD_CPU_MEMBER                          \
>    CYG_SCHEDTHREAD_TIMESLICE_MEMBER                    \
>    CYG_SCHEDTHREAD_TIMESLICE_ENABLED_MEMBER
> #else ...

In Cyg_SchedThread_Implementation class of edf.hxx I added *edf_info*:

> class Cyg_SchedThread_Implementation
>    : public Cyg_DNode_T<Cyg_Thread>
> {
>    friend class Cyg_Scheduler_Implementation;
>    friend class Cyg_ThreadQueue_Implementation;

> protected:
>    cyg_priority        priority;       // current thread priority
>    struct cyg_sched_edf_info_t *edf_info; // added by me
> ...
> }

In my eCos application I am passing arguments in this way:

> #include <cyg/kernel/ktypes.h>
> ...
> void cyg_user_start(void)
> {
>       struct cyg_edf_info_t my_edf_info_A = {4, 11, 12};
>
>       cyg_thread_create((cyg_addrword_t) &my_edf_info_A, simple_program, (cyg_addrword_t) 0,
>               "Thread A", (void *) stack[0], 4096,
>                &simple_threadA, &thread_s[0]);
>       printf("Threads are created\n");
>       cyg_thread_resume(simple_threadA);
> }

Now, *puzzle*. Depending on my code in the constructor of the
Cyg_SchedThread_Implementation class at edf.cxx I have two different
outputs.

In the first scenario (result is the same as in the previous post,
*priority* with *edf_info->deadline* value):
> Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation
> (
>    CYG_ADDRWORD sched_info
> )
> {
>    edf_info = (cyg_sched_edf_info_t *) sched_info;
>    CYG_TRACE1(1, "deadline = %d", edf_info->deadline);
>    CYG_TRACE1(1, "wcet = %d", edf_info->wcet);
>    CYG_TRACE1(1, "period = %d", edf_info->period);
>    priority = (cyg_priority) edf_info->deadline; // important
>    CYG_TRACE1(1, "Priority = %d ", priority);
> ...	
> }

Output is:
> TRACE: edf.cxx [590] Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation()   'deadline = 16688624'
> TRACE: edf.cxx [591] Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation()   'wcet = 15304688'
> TRACE: edf.cxx [592] Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation()   'period = 15691760'
> TRACE: edf.cxx [594] Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation()   'priority = 16688624'
> ASSERT FAIL: <1> edf.cxx [211] Cyg_Scheduler_Implementation::add_thread()  Priority out of range!

In the second scenario (just changing *priority* assign value to *sched_info*):

> Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation
> (
>    CYG_ADDRWORD sched_info
> ) {
>    edf_info = (cyg_sched_edf_info_t *) sched_info;
>    CYG_TRACE1(1, "deadline= %d", edf_info->deadline);
>    CYG_TRACE1(1, "wcet = %d", edf_info->wcet);
>    CYG_TRACE1(1, "period = %d", edf_info->period);
>    priority = (cyg_priority) sched_info; // important
>    CYG_TRACE1(1, "Priority = %d ", priority);
> ...	
> }

Output is:
> TRACE: prestart.cxx [77] void cyg_prestart()  'This is the system default cyg_prestart()'
> TRACE: pkgstart.cxx [87] void cyg_package_start()  'This is the system default cyg_package_start()'
> TRACE: edf.cxx [590] Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation()   'deadline = 4'
> TRACE: edf.cxx [591] Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation()   'wcet = 11'
> TRACE: edf.cxx [592] Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation()   'period = 12'
> TRACE: edf.cxx [594] Cyg_SchedThread_Implementation::Cyg_SchedThread_Implementation()   'priority = 1162644'
> Threads are created
> ASSERT FAIL: <1> edf.cxx [211] Cyg_Scheduler_Implementation::add_thread()  Priority out of range!

I think, the value to which *edf_info->deadline* pointing is changing
depending on which value has the *priority*. But, I don't no why?

Can anyone help me to find an answer?

Regards,
Nodir.

--
Before posting, please read the FAQ: http://ecos.sourceware.org/fom/ecos
and search the list archive: http://ecos.sourceware.org/ml/ecos-discuss