threadstartmultitasking.c

RTEMS (Real-Time Executive for Multiprocessor Systems) is a free open source real-time operating sys

/*
 *  Thread Handler
 *
 *
 *  COPYRIGHT (c) 1989-1999.
 *  On-Line Applications Research Corporation (OAR).
 *
 *  The license and distribution terms for this file may be
 *  found in found in the file LICENSE in this distribution or at
 *  http://www.rtems.com/license/LICENSE.
 *
 *  $Id: threadstartmultitasking.c,v 1.2.6.1 2003/09/04 18:52:48 joel Exp $
 */

#include <rtems/system.h>
#include <rtems/score/apiext.h>
#include <rtems/score/context.h>
#include <rtems/score/interr.h>
#include <rtems/score/isr.h>
#include <rtems/score/object.h>
#include <rtems/score/priority.h>
#include <rtems/score/states.h>
#include <rtems/score/sysstate.h>
#include <rtems/score/thread.h>
#include <rtems/score/threadq.h>
#include <rtems/score/userext.h>
#include <rtems/score/wkspace.h>

/*PAGE
 *
 *  _Thread_Start_multitasking
 *
 *  This kernel routine readies the requested thread, the thread chain
 *  is adjusted.  A new heir thread may be selected.
 *
 *  Input parameters:
 *    system_thread - pointer to system initialization thread control block
 *    idle_thread   - pointer to idle thread control block
 *
 *  Output parameters:  NONE
 *
 *  NOTE:  This routine uses the "blocking" heir selection mechanism.
 *         This insures the correct heir after a thread restart.
 *
 *  INTERRUPT LATENCY:
 *    ready chain
 *    select heir
 */

void _Thread_Start_multitasking( void )
{
  /*
   *  The system is now multitasking and completely initialized.  
   *  This system thread now either "goes away" in a single processor 
   *  system or "turns into" the server thread in an MP system.
   */

  _System_state_Set( SYSTEM_STATE_UP );

  _Context_Switch_necessary = FALSE;

  _Thread_Executing = _Thread_Heir;

   /*
    * Get the init task(s) running.
    *
    * Note: Thread_Dispatch() is normally used to dispatch threads.  As
    *       part of its work, Thread_Dispatch() restores floating point
    *       state for the heir task.
    *
    *       This code avoids Thread_Dispatch(), and so we have to restore
    *       (actually initialize) the floating point state "by hand".
    *
    *       Ignore the CPU_USE_DEFERRED_FP_SWITCH because we must always
    *       switch in the first thread if it is FP.
    */
 

#if ( CPU_HARDWARE_FP == TRUE ) || ( CPU_SOFTWARE_FP == TRUE )
   /*
    *  don't need to worry about saving BSP's floating point state
    */

   if ( _Thread_Heir->fp_context != NULL )
     _Context_Restore_fp( &_Thread_Heir->fp_context );
#endif

  _Context_Switch( &_Thread_BSP_context, &_Thread_Heir->Registers );
}