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diff --git a/cpukit/include/rtems/score/scheduleruniimpl.h b/cpukit/include/rtems/score/scheduleruniimpl.h
new file mode 100644
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+++ b/cpukit/include/rtems/score/scheduleruniimpl.h
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+/* SPDX-License-Identifier: BSD-2-Clause */
+
+/**
+ * @file
+ *
+ * @ingroup RTEMSScoreScheduler
+ *
+ * @brief This header file provides interfaces of the supporting the
+ *   implementation of uniprocessor schedulers.
+ */
+
+/*
+ *  Copyright (C) 2010 Gedare Bloom.
+ *  Copyright (C) 2011 On-Line Applications Research Corporation (OAR).
+ *  Copyright (C) 2014, 2022 embedded brains GmbH & Co. KG
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef _RTEMS_SCORE_SCHEDULERUNIIMPL_H
+#define _RTEMS_SCORE_SCHEDULERUNIIMPL_H
+
+#include <rtems/score/schedulerimpl.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @addtogroup RTEMSScoreScheduler
+ *
+ * @{
+ */
+
+/**
+ * @brief Updates the heir thread of the processor.
+ *
+ * @param[in, out] heir is the current heir thread.
+ * @param[in, out] new_heir is the new heir thread.
+ */
+static inline void _Scheduler_uniprocessor_Update_heir(
+  Thread_Control *heir,
+  Thread_Control *new_heir
+)
+{
+  _Assert( heir != new_heir );
+#if defined(RTEMS_SMP)
+  /*
+   * We need this state only for _Thread_Get_CPU_time_used_locked().  Cannot
+   * use _Scheduler_Thread_change_state() since THREAD_SCHEDULER_BLOCKED to
+   * THREAD_SCHEDULER_BLOCKED state changes are illegal for the real SMP
+   * schedulers.
+   */
+  heir->Scheduler.state = THREAD_SCHEDULER_BLOCKED;
+  new_heir->Scheduler.state = THREAD_SCHEDULER_SCHEDULED;
+#endif
+  _Thread_Update_CPU_time_used( heir, _Thread_Get_CPU( heir ) );
+  _Thread_Heir = new_heir;
+  _Thread_Dispatch_necessary = true;
+}
+
+/**
+ * @brief Updates the heir thread of the processor if the current heir is
+ *   not equal to the new heir thread.
+ *
+ * The update takes place even if the current heir thread is not preemptible.
+ *
+ * @param[in, out] new_heir is the new heir thread.
+ */
+static inline void _Scheduler_uniprocessor_Update_heir_if_necessary(
+  Thread_Control *new_heir
+)
+{
+  Thread_Control *heir = _Thread_Heir;
+
+  if ( heir != new_heir ) {
+    _Scheduler_uniprocessor_Update_heir( heir, new_heir );
+  }
+}
+
+/**
+ * @brief Updates the heir thread of the processor if the current heir thread
+ *   is preemptible.
+ *
+ * @param[in, out] heir is the current heir thread.
+ * @param[in, out] new_heir is the new heir thread.
+ */
+static inline void _Scheduler_uniprocessor_Update_heir_if_preemptible(
+  Thread_Control *heir,
+  Thread_Control *new_heir
+)
+{
+  if ( heir != new_heir && heir->is_preemptible ) {
+    _Scheduler_uniprocessor_Update_heir( heir, new_heir );
+  }
+}
+
+/**
+ * @brief Blocks the thread.
+ *
+ * @param scheduler is the scheduler.
+ * @param the_thread is the thread to block.
+ * @param node is the scheduler node of the thread.
+ * @param extract is the handler to extract the thread.
+ * @param get_highest_ready is the handler to get the highest ready thread.
+ */
+static inline void _Scheduler_uniprocessor_Block(
+  const Scheduler_Control *scheduler,
+  Thread_Control          *the_thread,
+  Scheduler_Node          *node,
+  void                  ( *extract )(
+                             const Scheduler_Control *,
+                             Thread_Control *,
+                             Scheduler_Node *
+                        ),
+  Thread_Control       *( *get_highest_ready )( const Scheduler_Control * )
+)
+{
+  ( *extract )( scheduler, the_thread, node );
+
+  /* TODO: flash critical section? */
+
+  if ( _Thread_Is_heir( the_thread ) ) {
+    Thread_Control *highest_ready;
+
+    highest_ready = ( *get_highest_ready )( scheduler );
+    _Scheduler_uniprocessor_Update_heir( _Thread_Heir, highest_ready );
+  }
+}
+
+/**
+ * @brief Schedule the unblocked thread if it is the highest ready thread.
+ *
+ * @param scheduler is the scheduler.
+ * @param the_thread is the thread.
+ * @param priority is the priority of the thread.
+ */
+static inline void _Scheduler_uniprocessor_Unblock(
+  const Scheduler_Control *scheduler,
+  Thread_Control          *the_thread,
+  Priority_Control         priority
+)
+{
+  Thread_Control *heir;
+
+  heir = _Thread_Heir;
+
+  /*
+   * If the thread is more important than the heir, then we have a new heir.
+   * This may or may not result in a context switch.  If the current heir
+   * thread is preemptible, then we need to do a context switch.
+   */
+  if ( priority < _Thread_Get_priority( heir ) ) {
+    _Scheduler_uniprocessor_Update_heir_if_preemptible( heir, the_thread );
+  }
+}
+
+/**
+ * @brief Schedules the highest ready thread if the current heir thread of the
+ * processor is preemptible.
+ *
+ * @param scheduler is the scheduler.
+ * @param get_highest_ready is the handler to get the highest ready thread.
+ */
+static inline void _Scheduler_uniprocessor_Schedule(
+  const Scheduler_Control *scheduler,
+  Thread_Control       *( *get_highest_ready )( const Scheduler_Control * )
+)
+{
+  Thread_Control *highest_ready;
+
+  highest_ready = ( *get_highest_ready )( scheduler );
+  _Scheduler_uniprocessor_Update_heir_if_preemptible(
+    _Thread_Heir,
+    highest_ready
+  );
+}
+
+/**
+ * @brief Yields to the highest ready thread.
+ *
+ * @param scheduler is the scheduler.
+ * @param get_highest_ready is the handler to get the highest ready thread.
+ */
+static inline void _Scheduler_uniprocessor_Yield(
+  const Scheduler_Control *scheduler,
+  Thread_Control       *( *get_highest_ready )( const Scheduler_Control * )
+)
+{
+  Thread_Control *highest_ready;
+
+  highest_ready = ( *get_highest_ready )( scheduler );
+  _Scheduler_uniprocessor_Update_heir_if_necessary( highest_ready );
+}
+
+/** @} */
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTEMS_SCORE_SCHEDULERUNIIMPL_H */