schedulerimpl.h

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/*
 *  Copyright (C) 2010 Gedare Bloom.
 *  Copyright (C) 2011 On-Line Applications Research Corporation (OAR).
 *  Copyright (c) 2014, 2017 embedded brains GmbH
 *
 *  The license and distribution terms for this file may be
 *  found in the file LICENSE in this distribution or at
 *  http://www.rtems.org/license/LICENSE.
 */

#ifndef _RTEMS_SCORE_SCHEDULERIMPL_H
#define _RTEMS_SCORE_SCHEDULERIMPL_H

#include <rtems/score/scheduler.h>
#include <rtems/score/assert.h>
#include <rtems/score/priorityimpl.h>
#include <rtems/score/smpimpl.h>
#include <rtems/score/status.h>
#include <rtems/score/threadimpl.h>

#ifdef __cplusplus
extern "C" {
#endif

void _Scheduler_Handler_initialization( void );

RTEMS_INLINE_ROUTINE Scheduler_Context *_Scheduler_Get_context(
  const Scheduler_Control *scheduler
)
{
  return scheduler->context;
}

RTEMS_INLINE_ROUTINE const Scheduler_Control *_Scheduler_Get_by_CPU(
  const Per_CPU_Control *cpu
)
{
#if defined(RTEMS_SMP)
  return cpu->Scheduler.control;
#else
  (void) cpu;
  return &_Scheduler_Table[ 0 ];
#endif
}

RTEMS_INLINE_ROUTINE void _Scheduler_Acquire_critical(
  const Scheduler_Control *scheduler,
  ISR_lock_Context        *lock_context
)
{
#if defined(RTEMS_SMP)
  Scheduler_Context *context;

  context = _Scheduler_Get_context( scheduler );
  _ISR_lock_Acquire( &context->Lock, lock_context );
#else
  (void) scheduler;
  (void) lock_context;
#endif
}

RTEMS_INLINE_ROUTINE void _Scheduler_Release_critical(
  const Scheduler_Control *scheduler,
  ISR_lock_Context        *lock_context
)
{
#if defined(RTEMS_SMP)
  Scheduler_Context *context;

  context = _Scheduler_Get_context( scheduler );
  _ISR_lock_Release( &context->Lock, lock_context );
#else
  (void) scheduler;
  (void) lock_context;
#endif
}

#if defined(RTEMS_SMP)

RTEMS_INLINE_ROUTINE bool _Scheduler_Is_non_preempt_mode_supported(
  const Scheduler_Control *scheduler
)
{
  return scheduler->is_non_preempt_mode_supported;
}
#endif

#if defined(RTEMS_SMP)
void _Scheduler_Request_ask_for_help( Thread_Control *the_thread );

RTEMS_INLINE_ROUTINE void _Scheduler_Ask_for_help( Thread_Control *the_thread )
{
  _Assert( _Thread_State_is_owner( the_thread ) );

  if ( the_thread->Scheduler.helping_nodes > 0 ) {
    _Scheduler_Request_ask_for_help( the_thread );
  }
}
#endif

/*
 * Passing the Scheduler_Control* to these functions allows for multiple
 * scheduler's to exist simultaneously, which could be useful on an SMP
 * system.  Then remote Schedulers may be accessible.  How to protect such
 * accesses remains an open problem.
 */

RTEMS_INLINE_ROUTINE void _Scheduler_Schedule( Thread_Control *the_thread )
{
  const Scheduler_Control *scheduler;
  ISR_lock_Context         lock_context;

  scheduler = _Thread_Scheduler_get_home( the_thread );
  _Scheduler_Acquire_critical( scheduler, &lock_context );

  ( *scheduler->Operations.schedule )( scheduler, the_thread );

  _Scheduler_Release_critical( scheduler, &lock_context );
}

RTEMS_INLINE_ROUTINE void _Scheduler_Yield( Thread_Control *the_thread )
{
  const Scheduler_Control *scheduler;
  ISR_lock_Context         lock_context;

  scheduler = _Thread_Scheduler_get_home( the_thread );
  _Scheduler_Acquire_critical( scheduler, &lock_context );
  ( *scheduler->Operations.yield )(
    scheduler,
    the_thread,
    _Thread_Scheduler_get_home_node( the_thread )
  );
  _Scheduler_Release_critical( scheduler, &lock_context );
}

RTEMS_INLINE_ROUTINE void _Scheduler_Block( Thread_Control *the_thread )
{
#if defined(RTEMS_SMP)
  Chain_Node              *node;
  const Chain_Node        *tail;
  Scheduler_Node          *scheduler_node;
  const Scheduler_Control *scheduler;
  ISR_lock_Context         lock_context;

  node = _Chain_First( &the_thread->Scheduler.Scheduler_nodes );
  tail = _Chain_Immutable_tail( &the_thread->Scheduler.Scheduler_nodes );

  scheduler_node = SCHEDULER_NODE_OF_THREAD_SCHEDULER_NODE( node );
  scheduler = _Scheduler_Node_get_scheduler( scheduler_node );

  _Scheduler_Acquire_critical( scheduler, &lock_context );
  ( *scheduler->Operations.block )(
    scheduler,
    the_thread,
    scheduler_node
  );
  _Scheduler_Release_critical( scheduler, &lock_context );

  node = _Chain_Next( node );

  while ( node != tail ) {
    scheduler_node = SCHEDULER_NODE_OF_THREAD_SCHEDULER_NODE( node );
    scheduler = _Scheduler_Node_get_scheduler( scheduler_node );

    _Scheduler_Acquire_critical( scheduler, &lock_context );
    ( *scheduler->Operations.withdraw_node )(
      scheduler,
      the_thread,
      scheduler_node,
      THREAD_SCHEDULER_BLOCKED
    );
    _Scheduler_Release_critical( scheduler, &lock_context );

    node = _Chain_Next( node );
  }
#else
  const Scheduler_Control *scheduler;

  scheduler = _Thread_Scheduler_get_home( the_thread );
  ( *scheduler->Operations.block )(
    scheduler,
    the_thread,
    _Thread_Scheduler_get_home_node( the_thread )
  );
#endif
}

RTEMS_INLINE_ROUTINE void _Scheduler_Unblock( Thread_Control *the_thread )
{
  Scheduler_Node          *scheduler_node;
  const Scheduler_Control *scheduler;
  ISR_lock_Context         lock_context;

#if defined(RTEMS_SMP)
  scheduler_node = SCHEDULER_NODE_OF_THREAD_SCHEDULER_NODE(
    _Chain_First( &the_thread->Scheduler.Scheduler_nodes )
  );
  scheduler = _Scheduler_Node_get_scheduler( scheduler_node );
#else
  scheduler_node = _Thread_Scheduler_get_home_node( the_thread );
  scheduler = _Thread_Scheduler_get_home( the_thread );
#endif

  _Scheduler_Acquire_critical( scheduler, &lock_context );
  ( *scheduler->Operations.unblock )( scheduler, the_thread, scheduler_node );
  _Scheduler_Release_critical( scheduler, &lock_context );
}

RTEMS_INLINE_ROUTINE void _Scheduler_Update_priority( Thread_Control *the_thread )
{
#if defined(RTEMS_SMP)
  Chain_Node       *node;
  const Chain_Node *tail;

  _Thread_Scheduler_process_requests( the_thread );

  node = _Chain_First( &the_thread->Scheduler.Scheduler_nodes );
  tail = _Chain_Immutable_tail( &the_thread->Scheduler.Scheduler_nodes );

  do {
    Scheduler_Node          *scheduler_node;
    const Scheduler_Control *scheduler;
    ISR_lock_Context         lock_context;

    scheduler_node = SCHEDULER_NODE_OF_THREAD_SCHEDULER_NODE( node );
    scheduler = _Scheduler_Node_get_scheduler( scheduler_node );

    _Scheduler_Acquire_critical( scheduler, &lock_context );
    ( *scheduler->Operations.update_priority )(
      scheduler,
      the_thread,
      scheduler_node
    );
    _Scheduler_Release_critical( scheduler, &lock_context );

    node = _Chain_Next( node );
  } while ( node != tail );
#else
  const Scheduler_Control *scheduler;

  scheduler = _Thread_Scheduler_get_home( the_thread );
  ( *scheduler->Operations.update_priority )(
    scheduler,
    the_thread,
    _Thread_Scheduler_get_home_node( the_thread )
  );
#endif
}

#if defined(RTEMS_SMP)

RTEMS_INLINE_ROUTINE void _Scheduler_Priority_and_sticky_update(
  Thread_Control *the_thread,
  int             sticky_level_change
)
{
  Chain_Node              *node;
  const Chain_Node        *tail;
  Scheduler_Node          *scheduler_node;
  const Scheduler_Control *scheduler;
  ISR_lock_Context         lock_context;

  _Thread_Scheduler_process_requests( the_thread );

  node = _Chain_First( &the_thread->Scheduler.Scheduler_nodes );
  scheduler_node = SCHEDULER_NODE_OF_THREAD_SCHEDULER_NODE( node );
  scheduler = _Scheduler_Node_get_scheduler( scheduler_node );

  _Scheduler_Acquire_critical( scheduler, &lock_context );

  scheduler_node->sticky_level += sticky_level_change;
  _Assert( scheduler_node->sticky_level >= 0 );

  ( *scheduler->Operations.update_priority )(
    scheduler,
    the_thread,
    scheduler_node
  );

  _Scheduler_Release_critical( scheduler, &lock_context );

  tail = _Chain_Immutable_tail( &the_thread->Scheduler.Scheduler_nodes );
  node = _Chain_Next( node );

  while ( node != tail ) {
    scheduler_node = SCHEDULER_NODE_OF_THREAD_SCHEDULER_NODE( node );
    scheduler = _Scheduler_Node_get_scheduler( scheduler_node );

    _Scheduler_Acquire_critical( scheduler, &lock_context );
    ( *scheduler->Operations.update_priority )(
      scheduler,
      the_thread,
      scheduler_node
    );
    _Scheduler_Release_critical( scheduler, &lock_context );

    node = _Chain_Next( node );
  }
}
#endif

RTEMS_INLINE_ROUTINE Priority_Control _Scheduler_Map_priority(
  const Scheduler_Control *scheduler,
  Priority_Control         priority
)
{
  return ( *scheduler->Operations.map_priority )( scheduler, priority );
}

RTEMS_INLINE_ROUTINE Priority_Control _Scheduler_Unmap_priority(
  const Scheduler_Control *scheduler,
  Priority_Control         priority
)
{
  return ( *scheduler->Operations.unmap_priority )( scheduler, priority );
}

RTEMS_INLINE_ROUTINE void _Scheduler_Node_initialize(
  const Scheduler_Control *scheduler,
  Scheduler_Node          *node,
  Thread_Control          *the_thread,
  Priority_Control         priority
)
{
  ( *scheduler->Operations.node_initialize )(
    scheduler,
    node,
    the_thread,
    priority
  );
}

RTEMS_INLINE_ROUTINE void _Scheduler_Node_destroy(
  const Scheduler_Control *scheduler,
  Scheduler_Node          *node
)
{
  ( *scheduler->Operations.node_destroy )( scheduler, node );
}

RTEMS_INLINE_ROUTINE void _Scheduler_Release_job(
  Thread_Control       *the_thread,
  Priority_Node        *priority_node,
  uint64_t              deadline,
  Thread_queue_Context *queue_context
)
{
  const Scheduler_Control *scheduler = _Thread_Scheduler_get_home( the_thread );

  _Thread_queue_Context_clear_priority_updates( queue_context );
  ( *scheduler->Operations.release_job )(
    scheduler,
    the_thread,
    priority_node,
    deadline,
    queue_context
  );
}

RTEMS_INLINE_ROUTINE void _Scheduler_Cancel_job(
  Thread_Control       *the_thread,
  Priority_Node        *priority_node,
  Thread_queue_Context *queue_context
)
{
  const Scheduler_Control *scheduler = _Thread_Scheduler_get_home( the_thread );

  _Thread_queue_Context_clear_priority_updates( queue_context );
  ( *scheduler->Operations.cancel_job )(
    scheduler,
    the_thread,
    priority_node,
    queue_context
  );
}

RTEMS_INLINE_ROUTINE void _Scheduler_Tick( const Per_CPU_Control *cpu )
{
  const Scheduler_Control *scheduler = _Scheduler_Get_by_CPU( cpu );
  Thread_Control *executing = cpu->executing;

  if ( scheduler != NULL && executing != NULL ) {
    ( *scheduler->Operations.tick )( scheduler, executing );
  }
}

RTEMS_INLINE_ROUTINE void _Scheduler_Start_idle(
  const Scheduler_Control *scheduler,
  Thread_Control          *the_thread,
  Per_CPU_Control         *cpu
)
{
  ( *scheduler->Operations.start_idle )( scheduler, the_thread, cpu );
}

RTEMS_INLINE_ROUTINE bool _Scheduler_Has_processor_ownership(
  const Scheduler_Control *scheduler,
  uint32_t                 cpu_index
)
{
#if defined(RTEMS_SMP)
  const Per_CPU_Control   *cpu;
  const Scheduler_Control *scheduler_of_cpu;

  cpu = _Per_CPU_Get_by_index( cpu_index );
  scheduler_of_cpu = _Scheduler_Get_by_CPU( cpu );

  return scheduler_of_cpu == scheduler;
#else
  (void) scheduler;
  (void) cpu_index;

  return true;
#endif
}

RTEMS_INLINE_ROUTINE const Processor_mask *_Scheduler_Get_processors(
  const Scheduler_Control *scheduler
)
{
#if defined(RTEMS_SMP)
  return &_Scheduler_Get_context( scheduler )->Processors;
#else
  return &_Processor_mask_The_one_and_only;
#endif
}

bool _Scheduler_Get_affinity(
  Thread_Control *the_thread,
  size_t          cpusetsize,
  cpu_set_t      *cpuset
);

RTEMS_INLINE_ROUTINE bool _Scheduler_default_Set_affinity_body(
  const Scheduler_Control *scheduler,
  Thread_Control          *the_thread,
  Scheduler_Node          *node,
  const Processor_mask    *affinity
)
{
  (void) scheduler;
  (void) the_thread;
  (void) node;
  return _Processor_mask_Is_subset( affinity, _SMP_Get_online_processors() );
}

bool _Scheduler_Set_affinity(
  Thread_Control  *the_thread,
  size_t           cpusetsize,
  const cpu_set_t *cpuset
);

RTEMS_INLINE_ROUTINE void _Scheduler_Generic_block(
  const Scheduler_Control *scheduler,
  Thread_Control          *the_thread,
  Scheduler_Node          *node,
  void                  ( *extract )(
                             const Scheduler_Control *,
                             Thread_Control *,
                             Scheduler_Node *
                        ),
  void                  ( *schedule )(
                             const Scheduler_Control *,
                             Thread_Control *,
                             bool
                        )
)
{
  ( *extract )( scheduler, the_thread, node );

  /* TODO: flash critical section? */

  if ( _Thread_Is_executing( the_thread ) || _Thread_Is_heir( the_thread ) ) {
    ( *schedule )( scheduler, the_thread, true );
  }
}

RTEMS_INLINE_ROUTINE uint32_t _Scheduler_Get_processor_count(
  const Scheduler_Control *scheduler
)
{
#if defined(RTEMS_SMP)
  const Scheduler_Context *context = _Scheduler_Get_context( scheduler );

  return _Processor_mask_Count( &context->Processors );
#else
  (void) scheduler;

  return 1;
#endif
}

RTEMS_INLINE_ROUTINE Objects_Id _Scheduler_Build_id( uint32_t scheduler_index )
{
  return _Objects_Build_id(
    OBJECTS_FAKE_OBJECTS_API,
    OBJECTS_FAKE_OBJECTS_SCHEDULERS,
    _Objects_Local_node,
    (uint16_t) ( scheduler_index + 1 )
  );
}

RTEMS_INLINE_ROUTINE uint32_t _Scheduler_Get_index_by_id( Objects_Id id )
{
  uint32_t minimum_id = _Scheduler_Build_id( 0 );

  return id - minimum_id;
}

RTEMS_INLINE_ROUTINE const Scheduler_Control *_Scheduler_Get_by_id(
  Objects_Id id
)
{
  uint32_t index;

  index = _Scheduler_Get_index_by_id( id );

  if ( index >= _Scheduler_Count ) {
    return NULL;
  }

  return &_Scheduler_Table[ index ];
}

RTEMS_INLINE_ROUTINE uint32_t _Scheduler_Get_index(
  const Scheduler_Control *scheduler
)
{
  return (uint32_t) (scheduler - &_Scheduler_Table[ 0 ]);
}

#if defined(RTEMS_SMP)

typedef Thread_Control *( *Scheduler_Get_idle_thread )(
  Scheduler_Context *context
);

typedef void ( *Scheduler_Release_idle_thread )(
  Scheduler_Context *context,
  Thread_Control    *idle
);

RTEMS_INLINE_ROUTINE void _Scheduler_Thread_change_state(
  Thread_Control         *the_thread,
  Thread_Scheduler_state  new_state
)
{
  _Assert(
    _ISR_lock_Is_owner( &the_thread->Scheduler.Lock )
      || the_thread->Scheduler.state == THREAD_SCHEDULER_BLOCKED
      || !_System_state_Is_up( _System_state_Get() )
  );

  the_thread->Scheduler.state = new_state;
}

RTEMS_INLINE_ROUTINE void _Scheduler_Set_idle_thread(
  Scheduler_Node *node,
  Thread_Control *idle
)
{
  _Assert( _Scheduler_Node_get_idle( node ) == NULL );
  _Assert(
    _Scheduler_Node_get_owner( node ) == _Scheduler_Node_get_user( node )
  );

  _Scheduler_Node_set_user( node, idle );
  node->idle = idle;
}

RTEMS_INLINE_ROUTINE Thread_Control *_Scheduler_Use_idle_thread(
  Scheduler_Context         *context,
  Scheduler_Node            *node,
  Per_CPU_Control           *cpu,
  Scheduler_Get_idle_thread  get_idle_thread
)
{
  Thread_Control *idle = ( *get_idle_thread )( context );

  _Scheduler_Set_idle_thread( node, idle );
  _Thread_Set_CPU( idle, cpu );
  return idle;
}

typedef enum {
  SCHEDULER_TRY_TO_SCHEDULE_DO_SCHEDULE,
  SCHEDULER_TRY_TO_SCHEDULE_DO_IDLE_EXCHANGE,
  SCHEDULER_TRY_TO_SCHEDULE_DO_BLOCK
} Scheduler_Try_to_schedule_action;

RTEMS_INLINE_ROUTINE Scheduler_Try_to_schedule_action
_Scheduler_Try_to_schedule_node(
  Scheduler_Context         *context,
  Scheduler_Node            *node,
  Thread_Control            *idle,
  Scheduler_Get_idle_thread  get_idle_thread
)
{
  ISR_lock_Context                  lock_context;
  Scheduler_Try_to_schedule_action  action;
  Thread_Control                   *owner;

  action = SCHEDULER_TRY_TO_SCHEDULE_DO_SCHEDULE;
  owner = _Scheduler_Node_get_owner( node );
  _Assert( _Scheduler_Node_get_user( node ) == owner );
  _Assert( _Scheduler_Node_get_idle( node ) == NULL );

  _Thread_Scheduler_acquire_critical( owner, &lock_context );

  if ( owner->Scheduler.state == THREAD_SCHEDULER_READY ) {
    _Thread_Scheduler_cancel_need_for_help( owner, _Thread_Get_CPU( owner ) );
    _Scheduler_Thread_change_state( owner, THREAD_SCHEDULER_SCHEDULED );
  } else if (
    owner->Scheduler.state == THREAD_SCHEDULER_SCHEDULED
      && node->sticky_level <= 1
  ) {
    action = SCHEDULER_TRY_TO_SCHEDULE_DO_BLOCK;
  } else if ( node->sticky_level == 0 ) {
    action = SCHEDULER_TRY_TO_SCHEDULE_DO_BLOCK;
  } else if ( idle != NULL ) {
    action = SCHEDULER_TRY_TO_SCHEDULE_DO_IDLE_EXCHANGE;
  } else {
    _Scheduler_Use_idle_thread(
      context,
      node,
      _Thread_Get_CPU( owner ),
      get_idle_thread
    );
  }

  _Thread_Scheduler_release_critical( owner, &lock_context );
  return action;
}

RTEMS_INLINE_ROUTINE Thread_Control *_Scheduler_Release_idle_thread(
  Scheduler_Context             *context,
  Scheduler_Node                *node,
  Scheduler_Release_idle_thread  release_idle_thread
)
{
  Thread_Control *idle = _Scheduler_Node_get_idle( node );

  if ( idle != NULL ) {
    Thread_Control *owner = _Scheduler_Node_get_owner( node );

    node->idle = NULL;
    _Scheduler_Node_set_user( node, owner );
    ( *release_idle_thread )( context, idle );
  }

  return idle;
}

RTEMS_INLINE_ROUTINE void _Scheduler_Exchange_idle_thread(
  Scheduler_Node *needs_idle,
  Scheduler_Node *uses_idle,
  Thread_Control *idle
)
{
  uses_idle->idle = NULL;
  _Scheduler_Node_set_user(
    uses_idle,
    _Scheduler_Node_get_owner( uses_idle )
  );
  _Scheduler_Set_idle_thread( needs_idle, idle );
}

RTEMS_INLINE_ROUTINE Per_CPU_Control *_Scheduler_Block_node(
  Scheduler_Context         *context,
  Thread_Control            *thread,
  Scheduler_Node            *node,
  bool                       is_scheduled,
  Scheduler_Get_idle_thread  get_idle_thread
)
{
  int               sticky_level;
  ISR_lock_Context  lock_context;
  Per_CPU_Control  *thread_cpu;

  sticky_level = node->sticky_level;
  --sticky_level;
  node->sticky_level = sticky_level;
  _Assert( sticky_level >= 0 );

  _Thread_Scheduler_acquire_critical( thread, &lock_context );
  thread_cpu = _Thread_Get_CPU( thread );
  _Thread_Scheduler_cancel_need_for_help( thread, thread_cpu );
  _Scheduler_Thread_change_state( thread, THREAD_SCHEDULER_BLOCKED );
  _Thread_Scheduler_release_critical( thread, &lock_context );

  if ( sticky_level > 0 ) {
    if ( is_scheduled && _Scheduler_Node_get_idle( node ) == NULL ) {
      Thread_Control *idle;

      idle = _Scheduler_Use_idle_thread(
        context,
        node,
        thread_cpu,
        get_idle_thread
      );
      _Thread_Dispatch_update_heir( _Per_CPU_Get(), thread_cpu, idle );
    }

    return NULL;
  }

  _Assert( thread == _Scheduler_Node_get_user( node ) );
  return thread_cpu;
}

RTEMS_INLINE_ROUTINE void _Scheduler_Discard_idle_thread(
  Scheduler_Context             *context,
  Thread_Control                *the_thread,
  Scheduler_Node                *node,
  Scheduler_Release_idle_thread  release_idle_thread
)
{
  Thread_Control  *idle;
  Thread_Control  *owner;
  Per_CPU_Control *cpu;

  idle = _Scheduler_Node_get_idle( node );
  owner = _Scheduler_Node_get_owner( node );

  node->idle = NULL;
  _Assert( _Scheduler_Node_get_user( node ) == idle );
  _Scheduler_Node_set_user( node, owner );
  ( *release_idle_thread )( context, idle );

  cpu = _Thread_Get_CPU( idle );
  _Thread_Set_CPU( the_thread, cpu );
  _Thread_Dispatch_update_heir( _Per_CPU_Get(), cpu, the_thread );
}

RTEMS_INLINE_ROUTINE bool _Scheduler_Unblock_node(
  Scheduler_Context             *context,
  Thread_Control                *the_thread,
  Scheduler_Node                *node,
  bool                           is_scheduled,
  Scheduler_Release_idle_thread  release_idle_thread
)
{
  bool unblock;

  ++node->sticky_level;
  _Assert( node->sticky_level > 0 );

  if ( is_scheduled ) {
    _Scheduler_Discard_idle_thread(
      context,
      the_thread,
      node,
      release_idle_thread
    );
    _Scheduler_Thread_change_state( the_thread, THREAD_SCHEDULER_SCHEDULED );
    unblock = false;
  } else {
    _Scheduler_Thread_change_state( the_thread, THREAD_SCHEDULER_READY );
    unblock = true;
  }

  return unblock;
}
#endif

RTEMS_INLINE_ROUTINE void _Scheduler_Update_heir(
  Thread_Control *new_heir,
  bool            force_dispatch
)
{
  Thread_Control *heir = _Thread_Heir;

  if ( heir != new_heir && ( heir->is_preemptible || force_dispatch ) ) {
#if defined(RTEMS_SMP)
    /*
     * We need this state only for _Thread_Get_CPU_time_used().  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;
  }
}

RTEMS_INLINE_ROUTINE Status_Control _Scheduler_Set(
  const Scheduler_Control *new_scheduler,
  Thread_Control          *the_thread,
  Priority_Control         priority
)
{
  Scheduler_Node          *new_scheduler_node;
  Scheduler_Node          *old_scheduler_node;
#if defined(RTEMS_SMP)
  ISR_lock_Context         lock_context;
  const Scheduler_Control *old_scheduler;

#endif

  if ( the_thread->Wait.queue != NULL ) {
    return STATUS_RESOURCE_IN_USE;
  }

  old_scheduler_node = _Thread_Scheduler_get_home_node( the_thread );
  _Priority_Plain_extract(
    &old_scheduler_node->Wait.Priority,
    &the_thread->Real_priority
  );

  if (
    !_Priority_Is_empty( &old_scheduler_node->Wait.Priority )
#if defined(RTEMS_SMP)
      || !_Chain_Has_only_one_node( &the_thread->Scheduler.Wait_nodes )
      || the_thread->Scheduler.pin_level != 0
#endif
  ) {
    _Priority_Plain_insert(
      &old_scheduler_node->Wait.Priority,
      &the_thread->Real_priority,
      the_thread->Real_priority.priority
    );
    return STATUS_RESOURCE_IN_USE;
  }

#if defined(RTEMS_SMP)
  old_scheduler = _Thread_Scheduler_get_home( the_thread );
  new_scheduler_node = _Thread_Scheduler_get_node_by_index(
    the_thread,
    _Scheduler_Get_index( new_scheduler )
  );

  _Scheduler_Acquire_critical( new_scheduler, &lock_context );

  if (
    _Scheduler_Get_processor_count( new_scheduler ) == 0
      || !( *new_scheduler->Operations.set_affinity )(
        new_scheduler,
        the_thread,
        new_scheduler_node,
        &the_thread->Scheduler.Affinity
      )
  ) {
    _Scheduler_Release_critical( new_scheduler, &lock_context );
    _Priority_Plain_insert(
      &old_scheduler_node->Wait.Priority,
      &the_thread->Real_priority,
      the_thread->Real_priority.priority
    );
    return STATUS_UNSATISFIED;
  }

  _Assert( the_thread->Scheduler.pinned_scheduler == NULL );
  the_thread->Scheduler.home_scheduler = new_scheduler;

  _Scheduler_Release_critical( new_scheduler, &lock_context );

  _Thread_Scheduler_process_requests( the_thread );
#else
  new_scheduler_node = old_scheduler_node;
#endif

  the_thread->Start.initial_priority = priority;
  _Priority_Node_set_priority( &the_thread->Real_priority, priority );
  _Priority_Initialize_one(
    &new_scheduler_node->Wait.Priority,
    &the_thread->Real_priority
  );

#if defined(RTEMS_SMP)
  if ( old_scheduler != new_scheduler ) {
    States_Control current_state;

    current_state = the_thread->current_state;

    if ( _States_Is_ready( current_state ) ) {
      _Scheduler_Block( the_thread );
    }

    _Assert( old_scheduler_node->sticky_level == 0 );
    _Assert( new_scheduler_node->sticky_level == 0 );

    _Chain_Extract_unprotected( &old_scheduler_node->Thread.Wait_node );
    _Assert( _Chain_Is_empty( &the_thread->Scheduler.Wait_nodes ) );
    _Chain_Initialize_one(
      &the_thread->Scheduler.Wait_nodes,
      &new_scheduler_node->Thread.Wait_node
    );
    _Chain_Extract_unprotected(
      &old_scheduler_node->Thread.Scheduler_node.Chain
    );
    _Assert( _Chain_Is_empty( &the_thread->Scheduler.Scheduler_nodes ) );
    _Chain_Initialize_one(
      &the_thread->Scheduler.Scheduler_nodes,
      &new_scheduler_node->Thread.Scheduler_node.Chain
    );

    _Scheduler_Node_set_priority( new_scheduler_node, priority, false );

    if ( _States_Is_ready( current_state ) ) {
      _Scheduler_Unblock( the_thread );
    }

    return STATUS_SUCCESSFUL;
  }
#endif

  _Scheduler_Node_set_priority( new_scheduler_node, priority, false );
  _Scheduler_Update_priority( the_thread );
  return STATUS_SUCCESSFUL;
}

#ifdef __cplusplus
}
#endif

#endif
/* end of include file */