score: Add SMP scheduler make/clean sticky

This patch fixes the following broken behaviour:

  While a thread is scheduled on a helping scheduler, while it does not
  own a MrsP semaphore, if it obtains a MrsP semaphore, then no
  scheduler node using an idle thread and the ceiling priority of the
  semaphore is unblocked for the home scheduler.

This could lead to priority inversion issues and is not in line
with the MrsP protocol.

Introduce two new scheduler operations which are only enabled if
RTEMS_SMP is defined.  The operations are used to make the scheduler
node of the home scheduler sticky and to clean the sticky property.
This helps to keep the sticky handing out of the frequently used
priority update operation.

Close #4532.

1 files changed, 75 insertions, 0 deletions

diff --git a/cpukit/include/rtems/score/scheduler.h b/cpukit/include/rtems/score/scheduler.h
index ad9d630023..95b4414bea 100644
--- a/cpukit/include/rtems/score/scheduler.h
+++ b/cpukit/include/rtems/score/scheduler.h
@@ -135,6 +135,61 @@ typedef struct {
   );
 
   /**
+   * @brief Makes the node sticky.
+   *
+   * This operation is used by _Thread_Priority_update_and_make_sticky().  It
+   * is only called for the scheduler node of the home scheduler.
+   *
+   * Uniprocessor schedulers schould provide
+   * _Scheduler_default_Sticky_do_nothing() for this operation.
+   *
+   * SMP schedulers should provide this operation using
+   * _Scheduler_SMP_Make_sticky().
+   *
+   * The make and clean sticky operations are an optimization to simplify the
+   * control flow in the update priority operation.  The update priority
+   * operation is used for all scheduler nodes and not just the scheduler node
+   * of home schedulers.  The update priority operation is a commonly used
+   * operations together with block and unblock.  The make and clean sticky
+   * operations are used only in specific scenarios.
+   *
+   * @param scheduler is the scheduler of the node.
+   *
+   * @param[in, out] the_thread is the thread owning the node.
+   *
+   * @param[in, out] node is the scheduler node to make sticky.
+   */
+  void ( *make_sticky )(
+    const Scheduler_Control *scheduler,
+    Thread_Control          *the_thread,
+    Scheduler_Node          *node
+  );
+
+  /**
+   * @brief Cleans the sticky property from the node.
+   *
+   * This operation is used by _Thread_Priority_update_and_clean_sticky().  It
+   * is only called for the scheduler node of the home scheduler.
+   *
+   * Uniprocessor schedulers schould provide
+   * _Scheduler_default_Sticky_do_nothing() for this operation.
+   *
+   * SMP schedulers should provide this operation using
+   * _Scheduler_SMP_Clean_sticky().
+   *
+   * @param scheduler is the scheduler of the node.
+   *
+   * @param[in, out] the_thread is the thread owning the node.
+   *
+   * @param[in, out] node is the scheduler node to clean the sticky property.
+   */
+  void ( *clean_sticky )(
+    const Scheduler_Control *scheduler,
+    Thread_Control          *the_thread,
+    Scheduler_Node          *node
+  );
+
+  /**
    * @brief Pin thread operation.
    *
    * @param[in] scheduler The scheduler instance of the specified processor.
@@ -400,6 +455,24 @@ Priority_Control _Scheduler_default_Unmap_priority(
   /**
    * @brief Does nothing.
    *
+   * This default implementation for the make and clean sticky operations
+   * should be used by uniprocessor schedulers if SMP support is enabled.
+   *
+   * @param scheduler is an unused parameter.
+   *
+   * @param the_thread is an unused parameter.
+   *
+   * @param node is an unused parameter.
+   */
+  void _Scheduler_default_Sticky_do_nothing(
+    const Scheduler_Control *scheduler,
+    Thread_Control          *the_thread,
+    Scheduler_Node          *node
+  );
+
+  /**
+   * @brief Does nothing.
+   *
    * This default implementation for the thread pin or unpin operations should
    * be used by uniprocessor schedulers if SMP support is enabled.
    *
@@ -459,6 +532,8 @@ Priority_Control _Scheduler_default_Unmap_priority(
     NULL, \
     NULL, \
     NULL, \
+    _Scheduler_default_Sticky_do_nothing, \
+    _Scheduler_default_Sticky_do_nothing, \
     _Scheduler_default_Pin_or_unpin_do_nothing, \
     _Scheduler_default_Pin_or_unpin_do_nothing, \
     NULL, \