Need help in understanding some of the existing code in RTEMS

[Richi Dubey]

Another quick question:
typedef struct {

#if defined(RTEMS_SMP)
...
  Chain_Control Scheduler_nodes;

#endif
/**
   * @brief The scheduler nodes of this thread.
   *
   * Each thread has a scheduler node for each scheduler instance.
   */
  Scheduler_Node *nodes;
} Thread_Scheduler_control;

Why do we have a Scheduler_Node *nodes? What does it indicate? Since the
pointer can point to a single value, why is it being called nodes?


On Wed, Jul 15, 2020 at 5:57 PM Richi Dubey <richidubey at gmail.com> wrote:

> Hi,
>
> I had a small question. The scheduler struct inside percpu.h looks like:
>
> ------------------------------------------------------------------------------------------------------
>     struct {
>       /**
>        * @brief The scheduler control of the scheduler owning this
> processor.
>        *
>        * This pointer is NULL in case this processor is currently not used
> by a
>        * scheduler instance.
>        */
>       const struct _Scheduler_Control *control;
>
>       /**
>        * @brief The scheduler context of the scheduler owning this
> processor.
>        *
>        * This pointer is NULL in case this processor is currently not used
> by a
>        * scheduler instance.
>        */
>       const struct Scheduler_Context *context;
>
>       /**
>        * @brief The idle thread for this processor in case it is online and
>        * currently not used by a scheduler instance.
>        */
>       struct _Thread_Control *idle_if_online_and_unused;
>     } Scheduler;
>
> ------------------------------------------------------------------------------------------------------
> So, does this mean a CPU when active is always either executing an idle
> thread and is not being used by a scheduler (so has a thread attribute in
> the idle_if_online_and_unused), or is used by a scheduler and is executing
> a task ( which can not be an idle task)? Another equivalent question is do
> we have an idle scheduler node, like we have idle predefined threads that
> run on a CPU?
>
> Please let me know,
> Thanks.
>
> On Tue, Jul 14, 2020 at 8:28 PM Richi Dubey <richidubey at gmail.com> wrote:
>
>> I understand. Thank you.
>>
>> On Tue, Jul 14, 2020 at 7:05 PM Sebastian Huber <
>> sebastian.huber at embedded-brains.de> wrote:
>>
>>> On 14/07/2020 13:37, Richi Dubey wrote:
>>>
>>> >     Here we remove the affine ready queue if it
>>> >     exists from the chain of affine queues since now an affine thread
>>> is
>>> >     scheduled on a processor.
>>> >
>>> > Why are we removing the entire affine queue corresponding to a
>>> > CPU when a single node of the queue gets scheduled?
>>> Because the highest priority affine thread is now a schedule one.
>>>
>>
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