[PATCH 10/12] scheduler: Simplify simple scheduler

[Sebastian Huber]

On 13/06/13 20:45, Gedare Bloom wrote:
> On Thu, Jun 13, 2013 at 2:35 PM, Sebastian Huber
> <sebastian.huber at embedded-brains.de>  wrote:
>> >On 13/06/13 20:21, Sebastian Huber wrote:
>>> >>
>>> >>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.
>>> >>
>> >
>> >Now I think that the LIFO/FIFO talks to much about a particular use case.
>> >What about
>> >
>> >_Scheduler_simple_Insert_as_first_of_priority_group()
>> >
> That would be acceptable if you prefer. It is usual to specify whether
> ties are broken by lifo/fifo. A priority queue that breaks ties with
> FIFO is called "stable".
>

Ok, the name is also a bit long.  Is it useful to change the scheduler 
operation methods as well, e.g. _Scheduler_Enqueue() -> 
_Scheduler_Enqueue_fifo()?

-- 
Sebastian Huber, embedded brains GmbH

Address : Dornierstr. 4, D-82178 Puchheim, Germany
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E-Mail  : sebastian.huber at embedded-brains.de
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