[PATCH] score: Document _Scheduler_Try_to_schedule_node()

[Richi Dubey]

>
> + * @retval SCHEDULER_TRY_TO_SCHEDULE_DO_BLOCK The node shall be blocked.
> This
> + *   action is returned, if the owner thread is already scheduled by
> another
> + *   scheduler.

When would this happen? When a thread is getting help from a
different processor that is using a different scheduler, right?
A thread has a node for it in each scheduler, right? ( I saw this in
threadinitialize.c)

  If a node requires an executing thread
> + * due to some locking protocol and the owner thread is already scheduled
> by
> + * another scheduler, then an idle thread shall be attached to the node.

What purpose does this serve?



On Wed, Aug 5, 2020 at 7:02 PM Richi Dubey <richidubey at gmail.com> wrote:

> Thanks for the explanation. I do not understand it right now, but I'm
> hoping it'd make sense some time in the future :p
>
> On Wed, Aug 5, 2020 at 12:50 PM Sebastian Huber <
> sebastian.huber at embedded-brains.de> wrote:
>
>> ---
>>  cpukit/include/rtems/score/schedulerimpl.h | 44 +++++++++++++++++-----
>>  1 file changed, 34 insertions(+), 10 deletions(-)
>>
>> diff --git a/cpukit/include/rtems/score/schedulerimpl.h
>> b/cpukit/include/rtems/score/schedulerimpl.h
>> index e7fbb8b166..8f5e1ba7b8 100644
>> --- a/cpukit/include/rtems/score/schedulerimpl.h
>> +++ b/cpukit/include/rtems/score/schedulerimpl.h
>> @@ -929,6 +929,10 @@ RTEMS_INLINE_ROUTINE Thread_Control
>> *_Scheduler_Use_idle_thread(
>>    return idle;
>>  }
>>
>> +/**
>> + * @brief This enumeration defines what a scheduler should do with a
>> node which
>> + * could be scheduled.
>> + */
>>  typedef enum {
>>    SCHEDULER_TRY_TO_SCHEDULE_DO_SCHEDULE,
>>    SCHEDULER_TRY_TO_SCHEDULE_DO_IDLE_EXCHANGE,
>> @@ -936,21 +940,41 @@ typedef enum {
>>  } Scheduler_Try_to_schedule_action;
>>
>>  /**
>> - * @brief Tries to schedule this scheduler node.
>> - *
>> - * @param context The scheduler instance context.
>> - * @param[in, out] node The node which wants to get scheduled.
>> - * @param idle A potential idle thread used by a potential victim node.
>> - * @param get_idle_thread Function to get an idle thread.
>> - *
>> - * @retval true This node can be scheduled.
>> - * @retval false This node cannot be scheduled.
>> + * @brief Tries to schedule the scheduler node.
>> + *
>> + * When a scheduler needs to schedule a node, it shall use this function
>> to
>> + * determine what it shall do with the node.  The node replaces a victim
>> node if
>> + * it can be scheduled.
>> + *
>> + * This function uses the state of the node and the scheduler state of
>> the owner
>> + * thread to determine what shall be done.  Each scheduler maintains its
>> nodes
>> + * independent of other schedulers.  This function ensures that a thread
>> is
>> + * scheduled by at most one scheduler.  If a node requires an executing
>> thread
>> + * due to some locking protocol and the owner thread is already
>> scheduled by
>> + * another scheduler, then an idle thread shall be attached to the node.
>> + *
>> + * @param[in, out] context is the scheduler instance context.
>> + * @param[in, out] node is the node which could be scheduled.
>> + * @param idle is an idle thread used by the victim node or NULL.
>> + * @param get_idle_thread points to a function to get an idle thread.
>> + *
>> + * @retval SCHEDULER_TRY_TO_SCHEDULE_DO_SCHEDULE The node shall be
>> scheduled.
>> + *
>> + * @retval SCHEDULER_TRY_TO_SCHEDULE_DO_IDLE_EXCHANGE The node shall be
>> + *   scheduled and the provided idle thread shall be attached to the
>> node.  This
>> + *   action is returned, if the node cannot use the owner thread and
>> shall use
>> + *   an idle thread instead.  In this case, the idle thread is provided
>> by the
>> + *   victim node.
>> + *
>> + * @retval SCHEDULER_TRY_TO_SCHEDULE_DO_BLOCK The node shall be
>> blocked.  This
>> + *   action is returned, if the owner thread is already scheduled by
>> another
>> + *   scheduler.
>>   */
>>  RTEMS_INLINE_ROUTINE Scheduler_Try_to_schedule_action
>>  _Scheduler_Try_to_schedule_node(
>>    Scheduler_Context         *context,
>>    Scheduler_Node            *node,
>> -  Thread_Control            *idle,
>> +  const Thread_Control      *idle,
>>    Scheduler_Get_idle_thread  get_idle_thread
>>  )
>>  {
>> --
>> 2.26.2
>>
>> _______________________________________________
>> devel mailing list
>> devel at rtems.org
>> http://lists.rtems.org/mailman/listinfo/devel
>>
>
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