/**
 * @file
 * 
 * @brief Dispatch Thread
 * @ingroup ScoreThread
 */

/*
 *  COPYRIGHT (c) 1989-2009.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  Copyright (c) 2014, 2016 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.
 */

#if HAVE_CONFIG_H
#include "config.h"
#endif

#include <rtems/score/threaddispatch.h>
#include <rtems/score/assert.h>
#include <rtems/score/isr.h>
#include <rtems/score/threadimpl.h>
#include <rtems/score/todimpl.h>
#include <rtems/score/userextimpl.h>
#include <rtems/score/wkspace.h>
#include <rtems/config.h>

#if __RTEMS_ADA__
void *rtems_ada_self;
#endif

#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
Thread_Control *_Thread_Allocated_fp;
#endif

CHAIN_DEFINE_EMPTY( _User_extensions_Switches_list );

static Thread_Action *_Thread_Get_post_switch_action(
  Thread_Control *executing
)
{
  Chain_Control *chain = &executing->Post_switch_actions.Chain;

  return (Thread_Action *) _Chain_Get_unprotected( chain );
}

static void _Thread_Run_post_switch_actions( Thread_Control *executing )
{
  ISR_lock_Context  lock_context;
  Thread_Action    *action;

  _Thread_State_acquire( executing, &lock_context );
  action = _Thread_Get_post_switch_action( executing );

  while ( action != NULL ) {
    _Chain_Set_off_chain( &action->Node );

    ( *action->handler )( executing, action, &lock_context );

    _Thread_State_acquire( executing, &lock_context );
    action = _Thread_Get_post_switch_action( executing );
  }

  _Thread_State_release( executing, &lock_context );
}

void _Thread_Do_dispatch( Per_CPU_Control *cpu_self, ISR_Level level )
{
  Thread_Control *executing;

  _Assert( cpu_self->thread_dispatch_disable_level == 1 );

  executing = cpu_self->executing;

  do {
    Thread_Control *heir = _Thread_Get_heir_and_make_it_executing( cpu_self );

    /*
     *  When the heir and executing are the same, then we are being
     *  requested to do the post switch dispatching.  This is normally
     *  done to dispatch signals.
     */
    if ( heir == executing )
      goto post_switch;

    /*
     *  Since heir and executing are not the same, we need to do a real
     *  context switch.
     */
#if __RTEMS_ADA__
    executing->rtems_ada_self = rtems_ada_self;
    rtems_ada_self = heir->rtems_ada_self;
#endif
    if ( heir->budget_algorithm == THREAD_CPU_BUDGET_ALGORITHM_RESET_TIMESLICE )
      heir->cpu_time_budget = rtems_configuration_get_ticks_per_timeslice();

    /*
     * On SMP the complete context switch must be atomic with respect to one
     * processor.  See also _Thread_Handler() since _Context_switch() may branch
     * to this function.
     */
#if !defined( RTEMS_SMP )
    _ISR_Local_enable( level );
#endif

    _User_extensions_Thread_switch( executing, heir );
    _Thread_Save_fp( executing );
    _Context_Switch( &executing->Registers, &heir->Registers );
    _Thread_Restore_fp( executing );

    /*
     * We have to obtain this value again after the context switch since the
     * heir thread may have migrated from another processor.  Values from the
     * stack or non-volatile registers reflect the old execution environment.
     */
    cpu_self = _Per_CPU_Get();

#if !defined( RTEMS_SMP )
    _ISR_Local_disable( level );
#endif
  } while (
#if defined( RTEMS_SMP )
    false
#else
    cpu_self->dispatch_necessary
#endif
  );

post_switch:
  _Assert( cpu_self->thread_dispatch_disable_level == 1 );
  cpu_self->thread_dispatch_disable_level = 0;
  _Profiling_Thread_dispatch_enable( cpu_self, 0 );

  _ISR_Local_enable( level );

  _Thread_Run_post_switch_actions( executing );
}

void _Thread_Dispatch( void )
{
  ISR_Level        level;
  Per_CPU_Control *cpu_self;

  _ISR_Local_disable( level );

  cpu_self = _Per_CPU_Get();

  if ( cpu_self->dispatch_necessary ) {
    _Profiling_Thread_dispatch_disable( cpu_self, 0 );
    cpu_self->thread_dispatch_disable_level = 1;
    _Thread_Do_dispatch( cpu_self, level );
  } else {
    _ISR_Local_enable( level );
  }
}