[PATCH 1/8] score: Update _Thread_Heir only if necessary

[Joel Sherrill]

On 3/4/2015 9:07 AM, Sebastian Huber wrote:
> Previously, the _Thread_Heir was updated unconditionally in case a new
> heir was determined.  The _Thread_Dispatch_necessary was only updated in
> case the executing thread was preemptible or an internal thread was
> unblocked.  Change this to update the _Thread_Heir and
> _Thread_Dispatch_necessary only in case the currently selected heir
> thread is preemptible or a dispatch is forced.  Move the schedule
> decision into the change priority operation and use the schedule
> operation only in rtems_task_mode() in case preemption is enabled or an
> ASR dispatch is necessary.  This is a behaviour change.  Previously, the
> RTEMS_NO_PREEMPT also prevented signal delivery in certain cases (not
> always).  Now, signal delivery is no longer influenced by
> RTEMS_NO_PREEMPT.  Since the currently selected heir thread is used to
> determine if a new heir is chosen, non-preemptible heir threads
> currently not executing now prevent a new heir.  This may have an
> application impact, see change test tm04.  Document this change in sp04.
>
> Update #2273.
...
> diff --git a/cpukit/score/src/schedulercbsunblock.c b/cpukit/score/src/schedulercbsunblock.c
> index 688253c..bd27aff 100644
> --- a/cpukit/score/src/schedulercbsunblock.c
> +++ b/cpukit/score/src/schedulercbsunblock.c
> @@ -79,10 +79,10 @@ Scheduler_Void_or_thread _Scheduler_CBS_Unblock(
>         _Thread_Heir->current_priority
>      )
>    ) {
> -    _Thread_Heir = the_thread;
> -    if ( _Thread_Executing->is_preemptible ||
> -         the_thread->current_priority == 0 )
> -      _Thread_Dispatch_necessary = true;
> +    _Scheduler_Update_heir(
> +      the_thread,
> +      the_thread->current_priority == 0
> +    );
The use of an expression without parentheses seems inconsistent
style-wise. I don't think this type of code is used often but could
you please put parentheses around this?

This same pattern is in other places so please do it globally across
this patch.
I think I spotted a total of four places.

Also since this indicates that the thread is at the pseudo-interrupt
priority,
maybe a macro/static inline with a meaningful name would be even
better.

-- 
Joel Sherrill, Ph.D.             Director of Research & Development
joel.sherrill at OARcorp.com        On-Line Applications Research
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