[PATCH 5/5] score: Update priority only if necessary

[Gedare Bloom]

ok, just the one note about doxygen. thanks!

On Tue, Aug 31, 2021 at 5:24 AM Sebastian Huber
<sebastian.huber at embedded-brains.de> wrote:
>
> In _Thread_queue_Flush_critical(), update the priority of the thread
> queue owner only if necessary.  The scheduler update priority operation
> could be expensive.
> ---
>  cpukit/include/rtems/score/threadqimpl.h |  4 ++--
>  cpukit/score/src/threadchangepriority.c  |  2 +-
>  cpukit/score/src/threadqflush.c          | 22 +++++++++++++---------
>  3 files changed, 16 insertions(+), 12 deletions(-)
>
> diff --git a/cpukit/include/rtems/score/threadqimpl.h b/cpukit/include/rtems/score/threadqimpl.h
> index f42c67cc47..33cdb3058d 100644
> --- a/cpukit/include/rtems/score/threadqimpl.h
> +++ b/cpukit/include/rtems/score/threadqimpl.h
> @@ -366,8 +366,8 @@ RTEMS_INLINE_ROUTINE void _Thread_queue_Context_clear_priority_updates(
>   *
>   * @return The priority update count of @a queue_context.
>   */
> -RTEMS_INLINE_ROUTINE size_t _Thread_queue_Context_save_priority_updates(
> -  Thread_queue_Context *queue_context
> +RTEMS_INLINE_ROUTINE size_t _Thread_queue_Context_get_priority_updates(
> +  const Thread_queue_Context *queue_context
>  )
>  {
>    return queue_context->Priority.update_count;
> diff --git a/cpukit/score/src/threadchangepriority.c b/cpukit/score/src/threadchangepriority.c
> index ac2e9a6d0c..613d0cd7af 100644
> --- a/cpukit/score/src/threadchangepriority.c
> +++ b/cpukit/score/src/threadchangepriority.c
> @@ -212,7 +212,7 @@ void _Thread_Priority_perform_actions(
>     */
>
>    the_thread = start_of_path;
> -  update_count = _Thread_queue_Context_save_priority_updates( queue_context );
> +  update_count = _Thread_queue_Context_get_priority_updates( queue_context );
>
>    while ( true ) {
>      Thread_queue_Queue *queue;
> diff --git a/cpukit/score/src/threadqflush.c b/cpukit/score/src/threadqflush.c
> index 357e3d696e..42b35a499b 100644
> --- a/cpukit/score/src/threadqflush.c
> +++ b/cpukit/score/src/threadqflush.c
> @@ -71,15 +71,15 @@ size_t _Thread_queue_Flush_critical(
>    Thread_queue_Context          *queue_context
>  )
>  {
> -  size_t          flushed;
> -  Chain_Control   unblock;
> -  Thread_Control *owner;
> -  Chain_Node     *node;
> -  Chain_Node     *tail;
> +  size_t        flushed;
> +  size_t        priority_updates;
> +  Chain_Control unblock;
> +  Chain_Node   *node;
> +  Chain_Node   *tail;
>
>    flushed = 0;
> +  priority_updates = 0;
>    _Chain_Initialize_empty( &unblock );
> -  owner = queue->owner;
>
>    while ( true ) {
>      Thread_queue_Heads *heads;
> @@ -99,8 +99,7 @@ size_t _Thread_queue_Flush_critical(
>
>      /*
>       * We do not have enough space in the queue context to collect all priority
> -     * updates, so clear it each time.  We unconditionally do the priority
> -     * update for the owner later if it exists.
> +     * updates, so clear it each time and accumulate the priority updates.
>       */
>      _Thread_queue_Context_clear_priority_updates( queue_context );
>
> @@ -120,6 +119,8 @@ size_t _Thread_queue_Flush_critical(
>        );
>      }
>
> +    priority_updates +=
> +      _Thread_queue_Context_get_priority_updates( queue_context );
>      ++flushed;
>    }
>
> @@ -145,9 +146,12 @@ size_t _Thread_queue_Flush_critical(
>        node = next;
>      } while ( node != tail );
>
> -    if ( owner != NULL ) {
> +    if ( priority_updates != 0 ) {
> +      Thread_Control  *owner;
>        ISR_lock_Context lock_context;
>
> +      owner = queue->owner;
> +      _Assert( owner != NULL );
>        _Thread_State_acquire( owner, &lock_context );
>        _Scheduler_Update_priority( owner );
>        _Thread_State_release( owner, &lock_context );
> --
> 2.26.2
>
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