[PATCH 10/12] scheduler: Simplify simple scheduler

[Sebastian Huber]

On 13/06/13 18:06, Gedare Bloom wrote:
> On Thu, Jun 13, 2013 at 12:01 PM, Gedare Bloom <gedare at rtems.org> wrote:
>> On Wed, Jun 12, 2013 at 11:29 AM, Sebastian Huber
>> <sebastian.huber at embedded-brains.de> wrote:
>>> Add and use _Scheduler_simple_Insert_as_first_order(),
>>> _Scheduler_simple_Insert_as_last_order(),
>>> _Scheduler_simple_Insert_as_first() and
>>> _Scheduler_simple_Insert_as_last().
>>> ---
>>>   .../score/inline/rtems/score/schedulersimple.inl   |   46 ++++++++++++++++++++
>>>   .../score/src/schedulersimplereadyqueueenqueue.c   |   21 +--------
>>>   .../src/schedulersimplereadyqueueenqueuefirst.c    |   26 +----------
>>>   3 files changed, 50 insertions(+), 43 deletions(-)
>>>
>>> diff --git a/cpukit/score/inline/rtems/score/schedulersimple.inl b/cpukit/score/inline/rtems/score/schedulersimple.inl
>>> index e67fc3c..1b58c85 100644
>>> --- a/cpukit/score/inline/rtems/score/schedulersimple.inl
>>> +++ b/cpukit/score/inline/rtems/score/schedulersimple.inl
>>> @@ -48,6 +48,52 @@ RTEMS_INLINE_ROUTINE void _Scheduler_simple_Ready_queue_requeue(
>>>     _Scheduler_simple_Ready_queue_enqueue( the_thread );
>>>   }
>>>
>>> +RTEMS_INLINE_ROUTINE bool _Scheduler_simple_Insert_as_first_order(
>>> +  const Chain_Node *to_insert,
>>> +  const Chain_Node *next
>>> +)
>>> +{
>>> +  const Thread_Control *thread_to_insert = (const Thread_Control *) to_insert;
>>> +  const Thread_Control *thread_next = (const Thread_Control *) next;
>>> +
>>> +  return thread_to_insert->current_priority <= thread_next->current_priority;
>>> +}
>>> +
>>> +RTEMS_INLINE_ROUTINE bool _Scheduler_simple_Insert_as_last_order(
>>> +  const Chain_Node *to_insert,
>>> +  const Chain_Node *next
>>> +)
>>> +{
>>> +  const Thread_Control *thread_to_insert = (const Thread_Control *) to_insert;
>>> +  const Thread_Control *thread_next = (const Thread_Control *) next;
>>> +
>>> +  return thread_to_insert->current_priority < thread_next->current_priority;
>>> +}
>>> +
>>> +RTEMS_INLINE_ROUTINE void _Scheduler_simple_Insert_as_first(
>>> +  Chain_Control *chain,
>>> +  Thread_Control *to_insert
>>> +)
>>> +{
>>> +  _Chain_Insert_ordered_unprotected(
>>> +    chain,
>>> +    &to_insert->Object.Node,
>>> +    _Scheduler_simple_Insert_as_first_order
>>> +  );
>>> +}
>>> +
>>> +RTEMS_INLINE_ROUTINE void _Scheduler_simple_Insert_as_last(
>>> +  Chain_Control *chain,
>>> +  Thread_Control *to_insert
>>> +)
>>> +{
>>> +  _Chain_Insert_ordered_unprotected(
>>> +    chain,
>>> +    &to_insert->Object.Node,
>>> +    _Scheduler_simple_Insert_as_last_order
>>> +  );
>>> +}
>> For these functions _Scheduler_simple_Insert_as_first() and
>> _Scheduler_simple_Insert_as_last() the name means they break priority
>> ties by FIFO and LIFO semantics? Before I read the code, I thought it
>> meant break ties by inserting to the first or last position of ties,
>> which is the opposite. I would prefer to have
>> _Scheduler_simple_Insert_as_fifo()/lifo() instead for added clarity.
>>
> I guess saying fifo/lifo could be confusing also, since the insert is
> not fifo/lifo, just how priority ties are broken. So maybe
> _Scheduler_simple_Insert_priority_fifo()/lifo()?

Suppose we have 0 < 5_0 <= 5_1 < 10, then insert 5_2 as first will yield

0 < 5_2 <= 5_0 <= 5_1 < 10

and insert 5_2 as last will yield

0 < 5_0 <= 5_1 <= 5_2 < 10

I will use your suggestions.

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone   : +49 89 189 47 41-16
Fax     : +49 89 189 47 41-09
E-Mail  : sebastian.huber at embedded-brains.de
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