On Wed, Jul 15, 2020 at 6:55 AM Richi Dubey <richidu...@gmail.com> wrote:
>
> 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?
>
See cpukit/score/src/threadinitialize.c +153
>
> On Wed, Jul 15, 2020 at 5:57 PM Richi Dubey <richidu...@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?
>>
Not exactly. What I understand is that:
* When a processor is online (active), but not used by a scheduler,
then it executes an idle task.
* When a processor is online and used by a scheduler, it may be
executing any task including an idle task.
You can find the relevant code in cpukit/include/rtems/score/schedulersmpimpl.h
The idle threads are specially handled when processors are
added/removed from scheduler contexts. A scheduler keeps a chain of
its idle threads:
cpukit/include/rtems/score/schedulersmp.h +64
>> Please let me know,
>> Thanks.
>>
>> On Tue, Jul 14, 2020 at 8:28 PM Richi Dubey <richidu...@gmail.com> wrote:
>>>
>>> I understand. Thank you.
>>>
>>> On Tue, Jul 14, 2020 at 7:05 PM Sebastian Huber
>>> <sebastian.hu...@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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