[PATCH v4] Pre-Release Strong-APA

Richi Dubey richidubey at gmail.com
Wed Aug 26 21:06:49 UTC 2020


Please review this version of my patch. This still gives a data-exception
error because of the earlier discussed issue while trying to scheduled Init
task.

This patch resolves issues from
https://github.com/richidubey/rtems/pull/7/files and patch v3.

Thanks,
Richi.

On Thu, Aug 27, 2020 at 2:32 AM Richi Dubey <richidubey at gmail.com> wrote:

> ---
>  cpukit/include/rtems/scheduler.h              |   6 +-
>  .../include/rtems/score/schedulerstrongapa.h  | 152 ++-
>  cpukit/score/src/schedulerstrongapa.c         | 886 ++++++++++++++----
>  3 files changed, 813 insertions(+), 231 deletions(-)
>
> diff --git a/cpukit/include/rtems/scheduler.h
> b/cpukit/include/rtems/scheduler.h
> index 955a83cfb4..6a05c2798a 100644
> --- a/cpukit/include/rtems/scheduler.h
> +++ b/cpukit/include/rtems/scheduler.h
> @@ -257,16 +257,14 @@
>    #define RTEMS_SCHEDULER_STRONG_APA( name, prio_count ) \
>      static struct { \
>        Scheduler_strong_APA_Context Base; \
> -      Chain_Control                Ready[ ( prio_count ) ]; \
> +      Scheduler_strong_APA_CPU CPU[ CONFIGURE_MAXIMUM_PROCESSORS ]; \
>      } SCHEDULER_STRONG_APA_CONTEXT_NAME( name )
>
>    #define RTEMS_SCHEDULER_TABLE_STRONG_APA( name, obj_name ) \
>      { \
>        &SCHEDULER_STRONG_APA_CONTEXT_NAME( name ).Base.Base.Base, \
>        SCHEDULER_STRONG_APA_ENTRY_POINTS, \
> -      RTEMS_ARRAY_SIZE( \
> -        SCHEDULER_STRONG_APA_CONTEXT_NAME( name ).Ready \
> -      ) - 1, \
> +      SCHEDULER_STRONG_APA_MAXIMUM_PRIORITY, \
>        ( obj_name ) \
>        SCHEDULER_CONTROL_IS_NON_PREEMPT_MODE_SUPPORTED( false ) \
>      }
> diff --git a/cpukit/include/rtems/score/schedulerstrongapa.h
> b/cpukit/include/rtems/score/schedulerstrongapa.h
> index 0ac28cb439..cfd79e932a 100644
> --- a/cpukit/include/rtems/score/schedulerstrongapa.h
> +++ b/cpukit/include/rtems/score/schedulerstrongapa.h
> @@ -6,31 +6,47 @@
>   * @brief Strong APA Scheduler API
>   */
>
> -/*
> - * Copyright (c) 2013, 2018 embedded brains GmbH.  All rights reserved.
> +/* SPDX-License-Identifier: BSD-2-Clause
>   *
> - *  embedded brains GmbH
> - *  Dornierstr. 4
> - *  82178 Puchheim
> - *  Germany
> - *  <rtems at embedded-brains.de>
> + * Copyright (C) 2020 Richi Dubey
> + * Copyright (c) 2013, 2018 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.
> + * 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_SCHEDULERSTRONGAPA_H
>  #define _RTEMS_SCORE_SCHEDULERSTRONGAPA_H
>
>  #include <rtems/score/scheduler.h>
> -#include <rtems/score/schedulerpriority.h>
>  #include <rtems/score/schedulersmp.h>
> +#include <rtems/score/percpu.h>
>
>  #ifdef __cplusplus
>  extern "C" {
>  #endif /* __cplusplus */
>
> +#define STRONG_SCHEDULER_NODE_OF_CHAIN( node ) \
> +  RTEMS_CONTAINER_OF( node, Scheduler_strong_APA_Node, Ready_node )
> +
>  /**
>   * @defgroup RTEMSScoreSchedulerStrongAPA Strong APA Scheduler
>   *
> @@ -38,42 +54,96 @@ extern "C" {
>   *
>   * @brief Strong APA Scheduler
>   *
> - * This is an implementation of the global fixed priority scheduler
> (G-FP).  It
> - * uses one ready chain per priority to ensure constant time insert
> operations.
> - * The scheduled chain uses linear insert operations and has at most
> processor
> - * count entries.  Since the processor and priority count are constants
> all
> - * scheduler operations complete in a bounded execution time.
> - *
> - * The the_thread preempt mode will be ignored.
> + * This is an implementation of the Strong APA scheduler defined by
> + * Cerqueira et al. in Linux's Processor Affinity API, Refined:
> + * Shifting Real-Time Tasks Towards Higher Schedulability.
>   *
> + * The scheduled and ready nodes are accessed via the
> + * Scheduler_strong_APA_Context::Ready which helps in backtracking when a
> + * node which is executing on a CPU gets blocked. New node is allocated to
> + * the cpu by checking all the executing nodes in the affinity set of the
> + * node and the subsequent nodes executing on the processors in its
> + * affinity set.
>   * @{
>   */
>
>  /**
> - * @brief Scheduler context specialization for Strong APA
> - * schedulers.
> + * @brief Scheduler node specialization for Strong APA schedulers.
>   */
>  typedef struct {
> -  Scheduler_SMP_Context    Base;
> -  Priority_bit_map_Control Bit_map;
> -  Chain_Control            Ready[ RTEMS_ZERO_LENGTH_ARRAY ];
> -} Scheduler_strong_APA_Context;
> +  /**
> +   * @brief SMP scheduler node.
> +   */
> +  Scheduler_SMP_Node Base;
> +
> + /**
> +   * @brief Chain node for Scheduler_strong_APA_Context::Ready.
> +   */
> +  Chain_Node Ready_node;
> +
> +  /**
> +   * @brief CPU that this node would preempt in the backtracking part of
> +   * _Scheduler_strong_APA_Get_highest_ready and
> +   * _Scheduler_strong_APA_Do_Enqueue.
> +   */
> +  Per_CPU_Control *cpu_to_preempt;
> +
> +  /**
> +   * @brief The associated affinity set of this node.
> +   */
> +  Processor_mask Affinity;
> +} Scheduler_strong_APA_Node;
> +
>
>  /**
> - * @brief Scheduler node specialization for Strong APA
> - * schedulers.
> + * @brief CPU related variables and a CPU_Control to implement BFS.
> + */
> +typedef struct
> +{
> +   /**
> +   * @brief CPU in a queue.
> +   */
> +  Per_CPU_Control *cpu;
> +
> +  /**
> +   * @brief The node that would preempt this CPU.
> +   */
> +  Scheduler_Node *preempting_node;
> +
> +   /**
> +   * @brief Whether or not this cpu has been added to the queue
> +   * (visited in BFS).
> +   */
> +  bool visited;
> +
> +  /**
> +   * @brief The node currently executing on this cpu.
> +   */
> +   Scheduler_Node *executing;
> +} Scheduler_strong_APA_CPU;
> +
> + /**
> + * @brief Scheduler context and node definition for Strong APA scheduler.
>   */
>  typedef struct {
> + /**
> +   * @brief @see Scheduler_SMP_Context.
> +   */
> +  Scheduler_SMP_Context Base;
> +
>    /**
> -   * @brief SMP scheduler node.
> +   * @brief Chain of all the ready and scheduled nodes present in
> +   * the Strong APA scheduler.
>     */
> -  Scheduler_SMP_Node Base;
> +  Chain_Control Ready;
>
>    /**
> -   * @brief The associated ready queue of this node.
> +   * @brief Struct with important variables for each cpu.
>     */
> -  Scheduler_priority_Ready_queue Ready_queue;
> -} Scheduler_strong_APA_Node;
> +  Scheduler_strong_APA_CPU CPU[ RTEMS_ZERO_LENGTH_ARRAY ];
> +} Scheduler_strong_APA_Context;
> +
> +#define SCHEDULER_STRONG_APA_MAXIMUM_PRIORITY 255
>
>  /**
>   * @brief Entry points for the Strong APA Scheduler.
> @@ -100,8 +170,8 @@ typedef struct {
>      _Scheduler_default_Release_job, \
>      _Scheduler_default_Cancel_job, \
>      _Scheduler_default_Tick, \
> -    _Scheduler_SMP_Start_idle \
> -    SCHEDULER_OPERATION_DEFAULT_GET_SET_AFFINITY \
> +    _Scheduler_SMP_Start_idle, \
> +    _Scheduler_strong_APA_Set_affinity \
>    }
>
>  /**
> @@ -168,7 +238,7 @@ void _Scheduler_strong_APA_Update_priority(
>  /**
>   * @brief Asks for help.
>   *
> - * @param  scheduler The scheduler control instance.
> + * @param scheduler The scheduler control instance.
>   * @param the_thread The thread that asks for help.
>   * @param node The node of @a the_thread.
>   *
> @@ -246,6 +316,20 @@ void _Scheduler_strong_APA_Yield(
>    Scheduler_Node          *node
>  );
>
> +/**
> + * @brief Sets the affinity .
> + *
> + * @param scheduler The scheduler control instance.
> + * @param the_thread The thread to yield.
> + * @param[in, out] node The node of @a the_thread.
> + */
> +bool _Scheduler_strong_APA_Set_affinity(
> +  const Scheduler_Control *scheduler,
> +  Thread_Control          *thread,
> +  Scheduler_Node          *node_base,
> +  const Processor_mask    *affinity
> +);
> +
>  /** @} */
>
>  #ifdef __cplusplus
> diff --git a/cpukit/score/src/schedulerstrongapa.c
> b/cpukit/score/src/schedulerstrongapa.c
> index 924cd86412..2c623f3cb3 100644
> --- a/cpukit/score/src/schedulerstrongapa.c
> +++ b/cpukit/score/src/schedulerstrongapa.c
> @@ -6,18 +6,31 @@
>   * @brief Strong APA Scheduler Implementation
>   */
>
> -/*
> - * Copyright (c) 2013, 2016 embedded brains GmbH.  All rights reserved.
> +/* SPDX-License-Identifier: BSD-2-Clause
> + *
> + * Copyright (C) 2020 Richi Dubey
> + * Copyright (c) 2013, 2018 embedded brains GmbH
>   *
> - *  embedded brains GmbH
> - *  Dornierstr. 4
> - *  82178 Puchheim
> - *  Germany
> - *  <rtems at embedded-brains.de>
> + * 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.
>   *
> - * 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.
> + * 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.
>   */
>
>  #ifdef HAVE_CONFIG_H
> @@ -25,301 +38,739 @@
>  #endif
>
>  #include <rtems/score/schedulerstrongapa.h>
> -#include <rtems/score/schedulerpriorityimpl.h>
>  #include <rtems/score/schedulersmpimpl.h>
> +#include <rtems/score/assert.h>
>
> -static Scheduler_strong_APA_Context *_Scheduler_strong_APA_Get_self(
> -  Scheduler_Context *context
> -)
> +static inline Scheduler_strong_APA_Context *
> +_Scheduler_strong_APA_Get_context( const Scheduler_Control *scheduler )
> +{
> +  return (Scheduler_strong_APA_Context *) _Scheduler_Get_context(
> scheduler );
> +}
> +
> +static inline Scheduler_strong_APA_Context *
> +_Scheduler_strong_APA_Get_self( Scheduler_Context *context )
>  {
>    return (Scheduler_strong_APA_Context *) context;
>  }
>
> -static Scheduler_strong_APA_Node *
> +static inline Scheduler_strong_APA_Node *
>  _Scheduler_strong_APA_Node_downcast( Scheduler_Node *node )
>  {
>    return (Scheduler_strong_APA_Node *) node;
>  }
>
> -static void _Scheduler_strong_APA_Move_from_scheduled_to_ready(
> +static inline void _Scheduler_strong_APA_Do_update(
>    Scheduler_Context *context,
> -  Scheduler_Node    *scheduled_to_ready
> +  Scheduler_Node    *node,
> +  Priority_Control   new_priority
>  )
>  {
> -  Scheduler_strong_APA_Context *self =
> -    _Scheduler_strong_APA_Get_self( context );
> -  Scheduler_strong_APA_Node *node =
> -    _Scheduler_strong_APA_Node_downcast( scheduled_to_ready );
> -
> -  _Chain_Extract_unprotected( &node->Base.Base.Node.Chain );
> -  _Scheduler_priority_Ready_queue_enqueue_first(
> -    &node->Base.Base.Node.Chain,
> -    &node->Ready_queue,
> -    &self->Bit_map
> -  );
> +  Scheduler_SMP_Node *smp_node;
> +  (void) context;
> +
> +  smp_node = _Scheduler_SMP_Node_downcast( node );
> +  _Scheduler_SMP_Node_update_priority( smp_node, new_priority );
>  }
>
> -static void _Scheduler_strong_APA_Move_from_ready_to_scheduled(
> +/*
> + * Returns true if the Strong APA scheduler has ready nodes
> + * available for scheduling.
> + */
> +static inline bool
> +    _Scheduler_strong_APA_Has_ready( Scheduler_Context *context )
> +{
> +  Scheduler_strong_APA_Context *self;
> +  const Chain_Node             *tail;
> +  Chain_Node                   *next;
> +  Scheduler_strong_APA_Node    *node;
> +
> +  self = _Scheduler_strong_APA_Get_self( context );
> +  tail = _Chain_Immutable_tail( &self->Ready );
> +  next = _Chain_First( &self->Ready );
> +
> +  while ( next != tail ) {
> +    node = (Scheduler_strong_APA_Node *) STRONG_SCHEDULER_NODE_OF_CHAIN(
> next );
> +
> +    if (
> +      _Scheduler_SMP_Node_state( &node->Base.Base ) ==
> +      SCHEDULER_SMP_NODE_READY
> +    ) {
> +      return true;
> +    }
> +
> +    next = _Chain_Next( next );
> +  }
> +
> +  return false;
> +}
> +
> +static inline void _Scheduler_strong_APA_Allocate_processor(
>    Scheduler_Context *context,
> -  Scheduler_Node    *ready_to_scheduled
> +  Scheduler_Node    *scheduled_base,
> +  Scheduler_Node    *victim_base,
> +  Per_CPU_Control   *victim_cpu
>  )
>  {
> +  Scheduler_strong_APA_Node    *scheduled;
>    Scheduler_strong_APA_Context *self;
> -  Scheduler_strong_APA_Node    *node;
> -  Priority_Control              insert_priority;
>
> +  (void) victim_base;
> +
> +  scheduled = _Scheduler_strong_APA_Node_downcast( scheduled_base );
>    self = _Scheduler_strong_APA_Get_self( context );
> -  node = _Scheduler_strong_APA_Node_downcast( ready_to_scheduled );
>
> -  _Scheduler_priority_Ready_queue_extract(
> -    &node->Base.Base.Node.Chain,
> -    &node->Ready_queue,
> -    &self->Bit_map
> +  self->CPU[ _Per_CPU_Get_index( victim_cpu ) ].executing =
> scheduled_base;
> +
> +  _Scheduler_SMP_Allocate_processor_exact(
> +    context,
> +    &( scheduled->Base.Base ),
> +    NULL,
> +    victim_cpu
>    );
> -  insert_priority = _Scheduler_SMP_Node_priority( &node->Base.Base );
> +}
> +
> +/*
> + * Finds and returns the highest ready node present by accessing the
> + * _Strong_APA_Context->CPU with front and rear values.
> + */
> +static inline Scheduler_Node * _Scheduler_strong_APA_Find_highest_ready(
> +  Scheduler_strong_APA_Context *self,
> +  uint32_t                      front,
> +  uint32_t                      rear
> +)
> +{
> +  Scheduler_Node              *highest_ready;
> +  Scheduler_strong_APA_CPU    *CPU;
> +  const Chain_Node            *tail;
> +  Chain_Node                  *next;
> +  uint32_t                     index_assigned_cpu;
> +  uint32_t                     index_curr_cpu;
> +  Scheduler_strong_APA_Node   *node;
> +  Priority_Control             min_priority_num;
> +  Priority_Control             curr_priority;
> +  Per_CPU_Control             *assigned_cpu;
> +  Scheduler_SMP_Node_state     curr_state;
> +  Per_CPU_Control             *curr_CPU;
> +  bool                         first_task;
> +
> +  CPU = self->CPU;
> +   /*
> +    * When the first task accessed has nothing to compare its priority
> against
> +    * So, it is the task with the highest priority witnessed so far.
> +   */
> +  first_task = true;
> +
> +  _Assert( rear < CONFIGURE_MAXIMUM_PROCESSOR );
> +
> +  while( front <= rear ) {
> +    curr_CPU = CPU[ front ].cpu;
> +    front = front + 1;
> +
> +    tail = _Chain_Immutable_tail( &self->Ready );
> +    next = _Chain_First( &self->Ready );
> +
> +    while ( next != tail ) {
> +      node = (Scheduler_strong_APA_Node*) STRONG_SCHEDULER_NODE_OF_CHAIN(
> next );
> +      //Check if the curr_CPU is in the affinity set of the node.
> +      index_curr_cpu = _Per_CPU_Get_index( curr_CPU );
> +      if (
> +        _Processor_mask_Is_set( &node->Affinity, index_curr_cpu )
> +      ) {
> +        curr_state = _Scheduler_SMP_Node_state( &node->Base.Base );
> +
> +        if ( curr_state == SCHEDULER_SMP_NODE_SCHEDULED ) {
> +          assigned_cpu = _Thread_Get_CPU( node->Base.Base.user );
> +          index_assigned_cpu =  _Per_CPU_Get_index( assigned_cpu );
> +
> +          if ( CPU[ index_assigned_cpu ].visited == false ) {
> +            rear = rear + 1;
> +            CPU[ rear ].cpu = assigned_cpu;
> +            CPU[ index_assigned_cpu ].visited = true;
> +            /*
> +             * The curr CPU of the queue invoked this node to add its CPU
> +             * that it is executing on to the queue. So this node might
> get
> +             * preempted because of the invoker curr_CPU and this curr_CPU
> +             * is the CPU that node should preempt in case this node
> +             * gets preempted.
> +             */
> +            node->cpu_to_preempt = curr_CPU;
> +          }
> +        }
> +        else if ( curr_state == SCHEDULER_SMP_NODE_READY ) {
> +          curr_priority = _Scheduler_Node_get_priority( &node->Base.Base
> );
> +          curr_priority = SCHEDULER_PRIORITY_PURIFY( curr_priority );
> +
> +          if ( first_task == true || curr_priority < min_priority_num ) {
> +            min_priority_num = curr_priority;
> +           highest_ready = &node->Base.Base;
> +           first_task = false;
> +           /*
> +            * In case curr_CPU is filter_CPU, we need to store the
> +            * cpu_to_preempt value so that we go back to SMP_*
> +            * function, rather than preempting the node ourselves.
> +            */
> +           node->cpu_to_preempt = curr_CPU;
> +         }
> +        }
> +      }
> +    next = _Chain_Next( next );
> +    }
> +  }
> +
> +  return highest_ready;
> +}
> +
> +static inline void  _Scheduler_strong_APA_Move_from_ready_to_scheduled(
> +  Scheduler_Context *context,
> +  Scheduler_Node    *ready_to_scheduled
> +)
> +{
> +  Priority_Control insert_priority;
> +
> +  insert_priority = _Scheduler_SMP_Node_priority( ready_to_scheduled );
>    insert_priority = SCHEDULER_PRIORITY_APPEND( insert_priority );
> -  _Chain_Insert_ordered_unprotected(
> -    &self->Base.Scheduled,
> -    &node->Base.Base.Node.Chain,
> -    &insert_priority,
> -    _Scheduler_SMP_Priority_less_equal
> +  _Scheduler_SMP_Insert_scheduled(
> +    context,
> +    ready_to_scheduled,
> +    insert_priority
>    );
>  }
>
> -static void _Scheduler_strong_APA_Insert_ready(
> +/*
> + * Implement the BFS Algorithm for task departure to get the highest
> ready task
> + * for a particular CPU, returns the highest ready Scheduler_Node
> + * Scheduler_Node filter here pointst to the victim node that is blocked
> + * resulting which this function is called.
> + */
> +static inline Scheduler_Node *_Scheduler_strong_APA_Get_highest_ready(
>    Scheduler_Context *context,
> -  Scheduler_Node    *node_base,
> -  Priority_Control   insert_priority
> +  Scheduler_Node    *filter
>  )
>  {
>    Scheduler_strong_APA_Context *self;
> +  Per_CPU_Control              *filter_cpu;
>    Scheduler_strong_APA_Node    *node;
> +  Scheduler_Node               *highest_ready;
> +  Scheduler_Node               *curr_node;
> +  Scheduler_Node               *next_node;
> +  Scheduler_strong_APA_CPU     *CPU;
> +  uint32_t                     front;
> +  uint32_t                     rear;
> +  uint32_t                     cpu_max;
> +  uint32_t                             cpu_index;
>
>    self = _Scheduler_strong_APA_Get_self( context );
> -  node = _Scheduler_strong_APA_Node_downcast( node_base );
> +  //Denotes front and rear of the queue.
> +  front = 0;
> +  rear = -1;
>
> -  if ( SCHEDULER_PRIORITY_IS_APPEND( insert_priority ) ) {
> -    _Scheduler_priority_Ready_queue_enqueue(
> -      &node->Base.Base.Node.Chain,
> -      &node->Ready_queue,
> -      &self->Bit_map
> -    );
> -  } else {
> -    _Scheduler_priority_Ready_queue_enqueue_first(
> -      &node->Base.Base.Node.Chain,
> -      &node->Ready_queue,
> -      &self->Bit_map
> -    );
> +  filter_cpu = _Thread_Get_CPU( filter->user );
> +  CPU = self->CPU;
> +  cpu_max = _SMP_Get_processor_maximum();
> +
> +  for ( cpu_index = 0 ; cpu_index < cpu_max ; ++cpu_index ) {
> +    CPU[ cpu_index ].visited = false;
>    }
> +
> +  rear = rear + 1;
> +  CPU[ rear ].cpu = filter_cpu;
> +  CPU[ _Per_CPU_Get_index( filter_cpu ) ].visited = true;
> +
> +  highest_ready = _Scheduler_strong_APA_Find_highest_ready(
> +                    self,
> +                    front,
> +                    rear
> +                  );
> +
> +  if ( highest_ready != filter ) {
> +    /*
> +     * Backtrack on the path from
> +     * filter_cpu to highest_ready, shifting along every task.
> +     */
> +
> +    node = _Scheduler_strong_APA_Node_downcast( highest_ready );
> +    /*
> +     * Highest ready is not just directly reachable from the victim cpu
> +     * So there is need for task shifting .
> +     */
> +    while ( node->cpu_to_preempt !=  filter_cpu ) {
> +      curr_node = &node->Base.Base;
> +      next_node = CPU[ _Per_CPU_Get_index( node->cpu_to_preempt )
> ].executing;
> +
> +      _Scheduler_SMP_Preempt(
> +        context,
> +        curr_node,
> +        next_node,
> +        _Scheduler_strong_APA_Allocate_processor
> +      );
> +
> +      if( curr_node == highest_ready ) {
> +        _Scheduler_strong_APA_Move_from_ready_to_scheduled( context,
> curr_node );
> +      }
> +
> +      node = _Scheduler_strong_APA_Node_downcast( next_node );
> +    }
> +    /*
> +     * To save the last node so that the caller SMP_* function
> +     * can do the allocation
> +     */
> +      curr_node = &node->Base.Base;
> +      highest_ready = curr_node;
> +    }
> +
> +  return highest_ready;
>  }
>
> -static void _Scheduler_strong_APA_Extract_from_ready(
> +/*
> + * Checks the lowest scheduled directly reachable task
> + */
> +static inline Scheduler_Node *_Scheduler_strong_APA_Get_lowest_scheduled(
>    Scheduler_Context *context,
> -  Scheduler_Node    *the_thread
> +  Scheduler_Node    *filter_base
>  )
>  {
> -  Scheduler_strong_APA_Context *self =
> -    _Scheduler_strong_APA_Get_self( context );
> -  Scheduler_strong_APA_Node *node =
> -    _Scheduler_strong_APA_Node_downcast( the_thread );
> -
> -  _Scheduler_priority_Ready_queue_extract(
> -    &node->Base.Base.Node.Chain,
> -    &node->Ready_queue,
> -    &self->Bit_map
> -  );
> +  uint32_t                     cpu_max;
> +  uint32_t                     cpu_index;
> +  Scheduler_Node               *curr_node;
> +  Scheduler_Node               *lowest_scheduled;
> +  Priority_Control              max_priority_num;
> +  Priority_Control              curr_priority;
> +  Scheduler_strong_APA_Node    *filter_strong_node;
> +  Scheduler_strong_APA_Context *self;
> +
> +  self = _Scheduler_strong_APA_Get_self( context );
> +  lowest_scheduled = NULL; // To remove compiler warning.
> +  max_priority_num = 0;    // Max (Lowest) priority encountered so far.
> +  filter_strong_node = _Scheduler_strong_APA_Node_downcast( filter_base );
> +
> +  //lowest_scheduled is NULL if affinty of a node is 0
> +  _Assert( !_Processor_mask_Zero( &filter_strong_node->Affinity ) );
> +  cpu_max = _SMP_Get_processor_maximum();
> +
> +  for ( cpu_index = 0 ; cpu_index < cpu_max ; ++cpu_index ) {
> +    //Checks if the CPU is in the affinity set of filter_strong_node
> +    if ( _Processor_mask_Is_set( &filter_strong_node->Affinity, cpu_index
> ) ) {
> +      Per_CPU_Control *cpu = _Per_CPU_Get_by_index( cpu_index );
> +
> +      if ( _Per_CPU_Is_processor_online( cpu ) ) {
> +        curr_node = self->CPU[ _Per_CPU_Get_index( cpu ) ].executing;
> +        curr_priority = _Scheduler_Node_get_priority( curr_node );
> +        curr_priority = SCHEDULER_PRIORITY_PURIFY( curr_priority );
> +
> +        if ( curr_priority > max_priority_num ) {
> +          lowest_scheduled = curr_node;
> +          max_priority_num = curr_priority;
> +        }
> +      }
> +    }
> +  }
> +
> +  _Assert( lowest_scheduled != NULL );
> +  return lowest_scheduled;
>  }
>
> -static void _Scheduler_strong_APA_Do_update(
> +static inline void _Scheduler_strong_APA_Extract_from_scheduled(
>    Scheduler_Context *context,
> -  Scheduler_Node *node_to_update,
> -  Priority_Control new_priority
> +  Scheduler_Node    *node_to_extract
>  )
>  {
> -  Scheduler_strong_APA_Context *self =
> -    _Scheduler_strong_APA_Get_self( context );
> -  Scheduler_strong_APA_Node *node =
> -    _Scheduler_strong_APA_Node_downcast( node_to_update );
> -
> -  _Scheduler_SMP_Node_update_priority( &node->Base, new_priority );
> -  _Scheduler_priority_Ready_queue_update(
> -    &node->Ready_queue,
> -    SCHEDULER_PRIORITY_UNMAP( new_priority ),
> -    &self->Bit_map,
> -    &self->Ready[ 0 ]
> -  );
> +  Scheduler_strong_APA_Context *self;
> +  Scheduler_strong_APA_Node    *node;
> +
> +  self = _Scheduler_strong_APA_Get_self( context );
> +  node = _Scheduler_strong_APA_Node_downcast( node_to_extract );
> +
> +  _Scheduler_SMP_Extract_from_scheduled( &self->Base.Base,
> &node->Base.Base );
> +  //Not removing it from Ready since the node could go in the READY state.
>  }
>
> -static Scheduler_strong_APA_Context *
> -_Scheduler_strong_APA_Get_context( const Scheduler_Control *scheduler )
> +static inline void _Scheduler_strong_APA_Extract_from_ready(
> +  Scheduler_Context *context,
> +  Scheduler_Node    *node_to_extract
> +)
>  {
> -  return (Scheduler_strong_APA_Context *) _Scheduler_Get_context(
> scheduler );
> +  Scheduler_strong_APA_Context *self;
> +  Scheduler_strong_APA_Node    *node;
> +
> +  self = _Scheduler_strong_APA_Get_self( context );
> +  node = _Scheduler_strong_APA_Node_downcast( node_to_extract );
> +
> +  _Assert( !_Chain_Is_empty( self->Ready ) );
> +  _Assert( !_Chain_Is_node_off_chain( &node->Ready_node ) );
> +
> +   _Chain_Extract_unprotected( &node->Ready_node );
> +   _Chain_Set_off_chain( &node->Ready_node );
>  }
>
> -void _Scheduler_strong_APA_Initialize( const Scheduler_Control *scheduler
> )
> +static inline void _Scheduler_strong_APA_Insert_ready(
> +  Scheduler_Context *context,
> +  Scheduler_Node    *node_base,
> +  Priority_Control   insert_priority
> +)
>  {
> -  Scheduler_strong_APA_Context *self =
> -    _Scheduler_strong_APA_Get_context( scheduler );
> +  Scheduler_strong_APA_Context *self;
> +  Scheduler_strong_APA_Node    *node;
>
> -  _Scheduler_SMP_Initialize( &self->Base );
> -  _Priority_bit_map_Initialize( &self->Bit_map );
> -  _Scheduler_priority_Ready_queue_initialize(
> -    &self->Ready[ 0 ],
> -    scheduler->maximum_priority
> -  );
> +  self = _Scheduler_strong_APA_Get_self( context );
> +  node = _Scheduler_strong_APA_Node_downcast( node_base );
> +
> +  if( _Chain_Is_node_off_chain( &node->Ready_node ) ) {
> +    _Chain_Append_unprotected( &self->Ready, &node->Ready_node );
> +  }
>  }
>
> -void _Scheduler_strong_APA_Node_initialize(
> -  const Scheduler_Control *scheduler,
> -  Scheduler_Node          *node,
> -  Thread_Control          *the_thread,
> -  Priority_Control         priority
> +static inline void _Scheduler_strong_APA_Move_from_scheduled_to_ready(
> +  Scheduler_Context *context,
> +  Scheduler_Node    *scheduled_to_ready
>  )
>  {
> -  Scheduler_Context            *context;
> -  Scheduler_strong_APA_Context *self;
> -  Scheduler_strong_APA_Node    *the_node;
> +  Priority_Control insert_priority;
>
> -  the_node = _Scheduler_strong_APA_Node_downcast( node );
> -  _Scheduler_SMP_Node_initialize(
> -    scheduler,
> -    &the_node->Base,
> -    the_thread,
> -    priority
> -  );
> +  _Scheduler_SMP_Extract_from_scheduled( context, scheduled_to_ready );
> +  insert_priority = _Scheduler_SMP_Node_priority( scheduled_to_ready );
>
> -  context = _Scheduler_Get_context( scheduler );
> -  self = _Scheduler_strong_APA_Get_self( context );
> -  _Scheduler_priority_Ready_queue_update(
> -    &the_node->Ready_queue,
> -    SCHEDULER_PRIORITY_UNMAP( priority ),
> -    &self->Bit_map,
> -    &self->Ready[ 0 ]
> +  _Scheduler_strong_APA_Insert_ready(
> +    context,
> +    scheduled_to_ready,
> +    insert_priority
>    );
>  }
>
> -static bool _Scheduler_strong_APA_Has_ready( Scheduler_Context *context )
> +static inline Scheduler_Node* _Scheduler_strong_APA_Get_lowest_reachable(
> +  Scheduler_strong_APA_Context *self,
> +  uint32_t                      front,
> +  uint32_t                      rear,
> +  Per_CPU_Control             **cpu_to_preempt
> +)
>  {
> -  Scheduler_strong_APA_Context *self =
> -    _Scheduler_strong_APA_Get_self( context );
> +  Scheduler_Node              *lowest_reachable;
> +  Priority_Control             max_priority_num;
> +  uint32_t                    cpu_max;
> +  uint32_t                    cpu_index;
> +  Thread_Control              *curr_thread;
> +  Per_CPU_Control             *curr_CPU;
> +  Priority_Control             curr_priority;
> +  Scheduler_Node              *curr_node;
> +  Scheduler_strong_APA_Node   *curr_strong_node; //Current Strong_APA_Node
> +  Scheduler_strong_APA_CPU    *CPU;
> +
> +  max_priority_num = 0; //Max (Lowest) priority encountered so far.
> +  CPU = self->CPU;
> +  cpu_max = _SMP_Get_processor_maximum();
> +
> +  while( front <= rear ) {
> +    curr_CPU = CPU[ front ].cpu;
> +    front = front + 1;
> +
> +    curr_node = CPU[ _Per_CPU_Get_index( curr_CPU ) ].executing;
> +    curr_thread = curr_node->user;
> +
> +    curr_priority = _Scheduler_Node_get_priority( curr_node );
> +    curr_priority = SCHEDULER_PRIORITY_PURIFY( curr_priority );
> +
> +    curr_strong_node = _Scheduler_strong_APA_Node_downcast( curr_node );
> +
> +    if ( curr_priority > max_priority_num ) {
> +      lowest_reachable = curr_node;
> +      max_priority_num = curr_priority;
> +      *cpu_to_preempt = curr_CPU;
> +    }
> +
> +    if ( !curr_thread->is_idle ) {
> +      for ( cpu_index = 0 ; cpu_index < cpu_max ; ++cpu_index ) {
> +        if ( _Processor_mask_Is_set( &curr_strong_node->Affinity,
> cpu_index ) ) {
> +          //Checks if the thread_CPU is in the affinity set of the node
> +          Per_CPU_Control *cpu = _Per_CPU_Get_by_index( cpu_index );
> +          if ( _Per_CPU_Is_processor_online( cpu ) && CPU[ cpu_index
> ].visited == false ) {
> +            rear = rear + 1;
> +            CPU[ rear ].cpu = cpu;
> +            CPU[ cpu_index ].visited = true;
> +            CPU[ cpu_index ].preempting_node = curr_node;
> +          }
> +        }
> +      }
> +    }
> +  }
>
> -  return !_Priority_bit_map_Is_empty( &self->Bit_map );
> +  return lowest_reachable;
>  }
>
> -static Scheduler_Node *_Scheduler_strong_APA_Get_highest_ready(
> +static inline bool _Scheduler_strong_APA_Do_enqueue(
>    Scheduler_Context *context,
> -  Scheduler_Node    *node
> +  Scheduler_Node    *lowest_reachable,
> +  Scheduler_Node    *node,
> +  Priority_Control  insert_priority,
> +  Per_CPU_Control  *cpu_to_preempt
>  )
>  {
> -  Scheduler_strong_APA_Context *self =
> -    _Scheduler_strong_APA_Get_self( context );
> +  bool                          needs_help;
> +  Priority_Control              node_priority;
> +  Priority_Control              lowest_priority;
> +  Scheduler_strong_APA_CPU     *CPU;
> +  Scheduler_Node               *curr_node;
> +  Scheduler_strong_APA_Node    *curr_strong_node; //Current
> Strong_APA_Node
> +  Per_CPU_Control              *curr_CPU;
> +  Scheduler_strong_APA_Context *self;
> +  Scheduler_Node               *next_node;
>
> -  (void) node;
> +  self = _Scheduler_strong_APA_Get_self( context );
> +  CPU = self->CPU;
> +
> +  node_priority = _Scheduler_Node_get_priority( node );
> +  node_priority = SCHEDULER_PRIORITY_PURIFY( node_priority );
> +
> +  lowest_priority =  _Scheduler_Node_get_priority( lowest_reachable );
> +  lowest_priority = SCHEDULER_PRIORITY_PURIFY( lowest_priority );
> +
> +  if( lowest_priority > node_priority ) {
> +    //Backtrack on the path from
> +    //_Thread_Get_CPU(lowest_reachable->user) to lowest_reachable,
> shifting
> +    //along every task
> +
> +    curr_node = CPU[ _Per_CPU_Get_index( cpu_to_preempt )
> ].preempting_node;
> +    curr_strong_node = _Scheduler_strong_APA_Node_downcast( curr_node );
> +    curr_strong_node->cpu_to_preempt = cpu_to_preempt;
> +
> +    //Save which cpu to preempt in cpu_to_preempt value of the node
> +    while ( curr_node != node ) {
> +      curr_CPU = _Thread_Get_CPU( curr_node->user );
> +      curr_node = CPU[ _Per_CPU_Get_index( curr_CPU ) ].preempting_node;
> +      curr_strong_node = _Scheduler_strong_APA_Node_downcast( curr_node );
> +      curr_strong_node->cpu_to_preempt =  curr_CPU;
> +     }
> +
> +    curr_CPU = curr_strong_node->cpu_to_preempt;
> +    next_node = CPU[ _Per_CPU_Get_index( curr_CPU ) ].executing;
> +
> +    node_priority = _Scheduler_Node_get_priority( curr_node );
> +    node_priority = SCHEDULER_PRIORITY_PURIFY( node_priority );
> +
> +    _Scheduler_SMP_Enqueue_to_scheduled(
> +      context,
> +      curr_node,
> +      node_priority,
> +      next_node,
> +      _Scheduler_SMP_Insert_scheduled,
> +      _Scheduler_strong_APA_Move_from_scheduled_to_ready,
> +      _Scheduler_strong_APA_Allocate_processor
> +    );
>
> -  return (Scheduler_Node *) _Scheduler_priority_Ready_queue_first(
> -    &self->Bit_map,
> -    &self->Ready[ 0 ]
> -  );
> +    curr_node = next_node;
> +    curr_strong_node = _Scheduler_strong_APA_Node_downcast( curr_node );
> +
> +    while ( curr_node !=  lowest_reachable ) {
> +      curr_CPU = curr_strong_node->cpu_to_preempt;
> +      next_node = CPU[ _Per_CPU_Get_index( curr_CPU ) ].executing;
> +      //curr_node preempts the next_node;
> +      _Scheduler_SMP_Preempt(
> +       context,
> +       curr_node,
> +       next_node,
> +       _Scheduler_strong_APA_Allocate_processor
> +      );
> +
> +      curr_node = next_node;
> +      curr_strong_node = _Scheduler_strong_APA_Node_downcast( curr_node );
> +    }
> +
> +    _Scheduler_strong_APA_Move_from_scheduled_to_ready( context,
> lowest_reachable );
> +
> +    needs_help = false;
> +  } else {
> +    needs_help = true;
> +  }
> +
> +  //Add it to Ready chain since it is now either scheduled or just ready.
> +  _Scheduler_strong_APA_Insert_ready( context,node, insert_priority );
> +
> +  return needs_help;
>  }
>
> -void _Scheduler_strong_APA_Block(
> -  const Scheduler_Control *scheduler,
> -  Thread_Control          *the_thread,
> -  Scheduler_Node          *node
> +/*
> + * BFS Algorithm for task arrival
> + * Enqueue node either in the scheduled chain or in the ready chain.
> + * node is the newly arrived node and is currently not scheduled.
> + */
> +static inline bool _Scheduler_strong_APA_Enqueue(
> +  Scheduler_Context *context,
> +  Scheduler_Node    *node,
> +  Priority_Control   insert_priority
>  )
>  {
> -  Scheduler_Context *context = _Scheduler_Get_context( scheduler );
> +  Scheduler_strong_APA_Context *self;
> +  Scheduler_strong_APA_CPU     *CPU;
> +  uint32_t                     cpu_max;
> +  uint32_t                     cpu_index;
> +  Per_CPU_Control              *cpu_to_preempt;
> +  Scheduler_Node               *lowest_reachable;
> +  Scheduler_strong_APA_Node    *strong_node;
>
> -  _Scheduler_SMP_Block(
> +  //Denotes front and rear of the queue
> +  uint32_t     front;
> +  uint32_t     rear;
> +
> +  front = 0;
> +  rear = -1;
> +
> +  self = _Scheduler_strong_APA_Get_self( context );
> +  strong_node = _Scheduler_strong_APA_Node_downcast( node );
> +  cpu_max = _SMP_Get_processor_maximum();
> +  CPU = self->CPU;
> +
> +  for ( cpu_index = 0 ; cpu_index < cpu_max ; ++cpu_index ) {
> +    CPU[ cpu_index ].visited = false;
> +
> +    //Checks if the thread_CPU is in the affinity set of the node
> +    if ( _Processor_mask_Is_set( &strong_node->Affinity, cpu_index ) ) {
> +      Per_CPU_Control *cpu = _Per_CPU_Get_by_index( cpu_index );
> +
> +      if ( _Per_CPU_Is_processor_online( cpu ) ) {
> +        rear = rear + 1;
> +        CPU[ rear ].cpu = cpu;
> +        CPU[ cpu_index ].visited = true;
> +        CPU[ cpu_index ].preempting_node = node;
> +      }
> +    }
> +  }
> +
> +  //This assert makes sure that there always exist an element in the
> +  // Queue when we start the queue traversal.
> +  _Assert( !_Processor_mask_Zero( &strong_node->Affinity ) );
> +
> +  lowest_reachable = _Scheduler_strong_APA_Get_lowest_reachable(
> +                       self,
> +                       front,
> +                       rear,
> +                       &cpu_to_preempt
> +                     );
> +
> +  return _Scheduler_strong_APA_Do_enqueue(
> +           context,
> +           lowest_reachable,
> +           node,
> +           insert_priority,
> +           cpu_to_preempt
> +         );
> +}
> +
> +static inline bool _Scheduler_strong_APA_Enqueue_scheduled(
> +  Scheduler_Context *context,
> +  Scheduler_Node    *node,
> +  Priority_Control   insert_priority
> +)
> +{
> +  return _Scheduler_SMP_Enqueue_scheduled(
>      context,
> -    the_thread,
>      node,
> -    _Scheduler_SMP_Extract_from_scheduled,
> +    insert_priority,
> +    _Scheduler_SMP_Priority_less_equal,
>      _Scheduler_strong_APA_Extract_from_ready,
>      _Scheduler_strong_APA_Get_highest_ready,
> +    _Scheduler_strong_APA_Insert_ready,
> +    _Scheduler_SMP_Insert_scheduled,
>      _Scheduler_strong_APA_Move_from_ready_to_scheduled,
> -    _Scheduler_SMP_Allocate_processor_exact
> +    _Scheduler_strong_APA_Allocate_processor
>    );
>  }
>
> -static bool _Scheduler_strong_APA_Enqueue(
> +static inline bool _Scheduler_strong_APA_Do_ask_for_help(
>    Scheduler_Context *context,
> -  Scheduler_Node    *node,
> -  Priority_Control   insert_priority
> +  Thread_Control    *the_thread,
> +  Scheduler_Node    *node
>  )
>  {
> -  return _Scheduler_SMP_Enqueue(
> +  return _Scheduler_SMP_Ask_for_help(
>      context,
> +    the_thread,
>      node,
> -    insert_priority,
>      _Scheduler_SMP_Priority_less_equal,
>      _Scheduler_strong_APA_Insert_ready,
>      _Scheduler_SMP_Insert_scheduled,
>      _Scheduler_strong_APA_Move_from_scheduled_to_ready,
> -    _Scheduler_SMP_Get_lowest_scheduled,
> -    _Scheduler_SMP_Allocate_processor_exact
> +    _Scheduler_strong_APA_Get_lowest_scheduled,
> +    _Scheduler_strong_APA_Allocate_processor
>    );
>  }
>
> -static bool _Scheduler_strong_APA_Enqueue_scheduled(
> +static inline  void  _Scheduler_strong_APA_Do_set_affinity(
>    Scheduler_Context *context,
> -  Scheduler_Node    *node,
> -  Priority_Control  insert_priority
> +  Scheduler_Node    *node_base,
> +  void              *arg
>  )
>  {
> -  return _Scheduler_SMP_Enqueue_scheduled(
> +  Scheduler_strong_APA_Node *node;
> +
> +  node = _Scheduler_strong_APA_Node_downcast( node_base );
> +  node->Affinity = *( (const Processor_mask *) arg );
> +}
> +
> +void _Scheduler_strong_APA_Initialize( const Scheduler_Control *scheduler
> )
> +{
> +  Scheduler_strong_APA_Context *self =
> +      _Scheduler_strong_APA_Get_context( scheduler );
> +
> +  _Scheduler_SMP_Initialize( &self->Base );
> +  _Chain_Initialize_empty( &self->Ready );
> +}
> +
> +void _Scheduler_strong_APA_Yield(
> +  const Scheduler_Control *scheduler,
> +  Thread_Control          *thread,
> +  Scheduler_Node          *node
> +)
> +{
> +  Scheduler_Context *context = _Scheduler_Get_context( scheduler );
> +
> +  _Scheduler_SMP_Yield(
>      context,
> +    thread,
>      node,
> -    insert_priority,
> -    _Scheduler_SMP_Priority_less_equal,
>      _Scheduler_strong_APA_Extract_from_ready,
> -    _Scheduler_strong_APA_Get_highest_ready,
> -    _Scheduler_strong_APA_Insert_ready,
> -    _Scheduler_SMP_Insert_scheduled,
> -    _Scheduler_strong_APA_Move_from_ready_to_scheduled,
> -    _Scheduler_SMP_Allocate_processor_exact
> +    _Scheduler_strong_APA_Enqueue,
> +    _Scheduler_strong_APA_Enqueue_scheduled
>    );
>  }
>
> -void _Scheduler_strong_APA_Unblock(
> +void _Scheduler_strong_APA_Block(
>    const Scheduler_Control *scheduler,
> -  Thread_Control          *the_thread,
> +  Thread_Control          *thread,
>    Scheduler_Node          *node
>  )
>  {
>    Scheduler_Context *context = _Scheduler_Get_context( scheduler );
> -
> -  _Scheduler_SMP_Unblock(
> +  //The extract from ready automatically removes the node from Ready
> chain.
> +  _Scheduler_SMP_Block(
>      context,
> -    the_thread,
> +    thread,
>      node,
> -    _Scheduler_strong_APA_Do_update,
> -    _Scheduler_strong_APA_Enqueue
> +    _Scheduler_strong_APA_Extract_from_scheduled,
> +    _Scheduler_strong_APA_Extract_from_ready,
> +    _Scheduler_strong_APA_Get_highest_ready,
> +    _Scheduler_strong_APA_Move_from_ready_to_scheduled,
> +    _Scheduler_strong_APA_Allocate_processor
>    );
>  }
>
> -static bool _Scheduler_strong_APA_Do_ask_for_help(
> -  Scheduler_Context *context,
> -  Thread_Control    *the_thread,
> -  Scheduler_Node    *node
> +void _Scheduler_strong_APA_Unblock(
> +  const Scheduler_Control *scheduler,
> +  Thread_Control          *thread,
> +  Scheduler_Node          *node
>  )
>  {
> -  return _Scheduler_SMP_Ask_for_help(
> +  Scheduler_Context *context = _Scheduler_Get_context( scheduler );
> +
> +  _Scheduler_SMP_Unblock(
>      context,
> -    the_thread,
> +    thread,
>      node,
> -    _Scheduler_SMP_Priority_less_equal,
> -    _Scheduler_strong_APA_Insert_ready,
> -    _Scheduler_SMP_Insert_scheduled,
> -    _Scheduler_strong_APA_Move_from_scheduled_to_ready,
> -    _Scheduler_SMP_Get_lowest_scheduled,
> -    _Scheduler_SMP_Allocate_processor_lazy
> +    _Scheduler_strong_APA_Do_update,
> +    _Scheduler_strong_APA_Enqueue
>    );
>  }
>
>  void _Scheduler_strong_APA_Update_priority(
>    const Scheduler_Control *scheduler,
> -  Thread_Control          *the_thread,
> +  Thread_Control          *thread,
>    Scheduler_Node          *node
>  )
>  {
> @@ -327,7 +778,7 @@ void _Scheduler_strong_APA_Update_priority(
>
>    _Scheduler_SMP_Update_priority(
>      context,
> -    the_thread,
> +    thread,
>      node,
>      _Scheduler_strong_APA_Extract_from_ready,
>      _Scheduler_strong_APA_Do_update,
> @@ -345,7 +796,11 @@ bool _Scheduler_strong_APA_Ask_for_help(
>  {
>    Scheduler_Context *context = _Scheduler_Get_context( scheduler );
>
> -  return _Scheduler_strong_APA_Do_ask_for_help( context, the_thread, node
> );
> +  return _Scheduler_strong_APA_Do_ask_for_help(
> +    context,
> +    the_thread,
> +    node
> +  );
>  }
>
>  void _Scheduler_strong_APA_Reconsider_help_request(
> @@ -381,7 +836,7 @@ void _Scheduler_strong_APA_Withdraw_node(
>      _Scheduler_strong_APA_Extract_from_ready,
>      _Scheduler_strong_APA_Get_highest_ready,
>      _Scheduler_strong_APA_Move_from_ready_to_scheduled,
> -    _Scheduler_SMP_Allocate_processor_lazy
> +    _Scheduler_strong_APA_Allocate_processor
>    );
>  }
>
> @@ -416,20 +871,65 @@ Thread_Control
> *_Scheduler_strong_APA_Remove_processor(
>    );
>  }
>
> -void _Scheduler_strong_APA_Yield(
> +void _Scheduler_strong_APA_Node_initialize(
>    const Scheduler_Control *scheduler,
> +  Scheduler_Node          *node,
>    Thread_Control          *the_thread,
> -  Scheduler_Node          *node
> +  Priority_Control         priority
>  )
>  {
> -  Scheduler_Context *context = _Scheduler_Get_context( scheduler );
> +  Scheduler_SMP_Node *smp_node;
> +  Scheduler_strong_APA_Node *strong_node;
>
> -  _Scheduler_SMP_Yield(
> -    context,
> -    the_thread,
> -    node,
> -    _Scheduler_strong_APA_Extract_from_ready,
> -    _Scheduler_strong_APA_Enqueue,
> -    _Scheduler_strong_APA_Enqueue_scheduled
> +  smp_node = _Scheduler_SMP_Node_downcast( node );
> +  strong_node = _Scheduler_strong_APA_Node_downcast( node );
> +
> +  _Scheduler_SMP_Node_initialize( scheduler, smp_node, the_thread,
> priority );
> +
> +  _Processor_mask_Assign(
> +    &strong_node->Affinity,
> +   _SMP_Get_online_processors()
>    );
>  }
> +
> +bool _Scheduler_strong_APA_Set_affinity(
> +  const Scheduler_Control *scheduler,
> +  Thread_Control          *thread,
> +  Scheduler_Node          *node_base,
> +  const Processor_mask    *affinity
> +)
> +{
> +  Scheduler_Context         *context;
> +  Scheduler_strong_APA_Node *node;
> +  Processor_mask             local_affinity;
> +
> +  context = _Scheduler_Get_context( scheduler );
> +  _Processor_mask_And( &local_affinity, &context->Processors, affinity );
> +
> +  if ( _Processor_mask_Is_zero( &local_affinity ) ) {
> +    return false;
> +  }
> +
> +  node = _Scheduler_strong_APA_Node_downcast( node_base );
> +
> +  if ( _Processor_mask_Is_equal( &node->Affinity, affinity ) )
> +    return true;       //Nothing to do. Return true.
> +
> + _Processor_mask_Assign( &node->Affinity, &local_affinity );
> +
> + _Scheduler_SMP_Set_affinity(
> +   context,
> +   thread,
> +   node_base,
> +   &local_affinity,
> +   _Scheduler_strong_APA_Do_set_affinity,
> +   _Scheduler_strong_APA_Extract_from_ready,
> +   _Scheduler_strong_APA_Get_highest_ready,
> +   _Scheduler_strong_APA_Move_from_ready_to_scheduled,
> +   _Scheduler_strong_APA_Enqueue,
> +   _Scheduler_strong_APA_Allocate_processor
> + );
> +
> +  return true;
> +}
> +
> --
> 2.17.1
>
>
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