tcs.c

test file nucleus source

               /* Note that the priority bit map does not need to be
                  modified since there are other active tasks at the
                  same priority.  */
           }
           else
           {

               /* Add the TCB to an empty list.  */
               task -> tc_ready_previous =  task;
               task -> tc_ready_next =      task;
               *(task -> tc_priority_head)= task;

               /* Update the priority group bit map to indicate that this
                  priority now has a task ready.  */
               TCD_Priority_Groups =
                           TCD_Priority_Groups | (task -> tc_priority_group);

               /* Update the sub-priority bit map to show that this priority
                  is ready.  */
               *(task -> tc_sub_priority_ptr) =
                   (*(task -> tc_sub_priority_ptr)) | task -> tc_sub_priority;
           }

           /* Determine the highest priority task in the system.  */
           if (TCD_Priority_Groups & TC_HIGHEST_MASK)

               /* Base of sub-group is 0.  */
               index =  0;

           else if (TCD_Priority_Groups & TC_NEXT_HIGHEST_MASK)

               /* Base of sub-group is 8.  */
               index =  8;

           else if (TCD_Priority_Groups & TC_NEXT_LOWEST_MASK)

               /* Base of sub-group is 16.  */
               index =  16;
           else

               /* Base of sub-group is 24.  */
               index =  24;

           /* Calculate the highest available priority.  */
           index =  index + TCD_Lowest_Set_Bit[(INT)
                   ((TCD_Priority_Groups >> index) & TC_HIGHEST_MASK)];

           /* Get the mask of the priority within the group of 8 priorities.  */
           temp =  TCD_Sub_Priority_Groups[index];

           /* Calculate the actual priority.  */
           TCD_Highest_Priority =  (index << 3) + TCD_Lowest_Set_Bit[temp];

           /* Check for preemption.  */
           if ((TCD_Highest_Priority <= ((INT) TCD_Execute_Task -> tc_priority))
               && (TCD_Execute_Task -> tc_preemption))
           {

               /* Update the current task pointer.  */
               TCT_Set_Execute_Task(TCD_Priority_List[TCD_Highest_Priority]);

               /* Now, check and see if the current thread is a task.
                  If so, return a status that indicates a context
                  switch is needed.  */
               if ((TCD_Current_Thread) &&
                  (((TC_TCB *) TCD_Current_Thread) -> tc_id == TC_TASK_ID))

                   /* Transfer control to the system.  */
                   TCT_Control_To_System();
           }
       }
       else
       {

           /* Just modify the priority.  */
           task -> tc_priority =  new_priority;

           /* Build the other priority information.  */
           task -> tc_priority =      new_priority;
           task -> tc_priority_head = &(TCD_Priority_List[new_priority]);
           task -> tc_sub_priority =  (DATA_ELEMENT) (1 << (new_priority & 7));
           task -> tc_priority_group =   ((UNSIGNED) 1) << (new_priority >> 3);
           task -> tc_sub_priority_ptr =
                   &(TCD_Sub_Priority_Groups[(new_priority >> 3)]);
       }
#ifdef INCLUDE_PROVIEW
        _RTProf_DumpTask(task,RT_PROF_CHANGE_PRIORITY);
#endif
    }

    /* Release the protection of the scheduling list.  */
    TCT_Unprotect();

    /* Return to user mode */
    NU_USER_MODE();

    /* Return the old priority.  */
    return(old_priority);
}


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      TCS_Change_Preemption                                            */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function changes the preemption posture of the calling      */
/*      task.  Preemption for a task may be enabled or disabled.  If     */
/*      it is disabled, the task runs until it suspends or relinquishes. */
/*      If a preemption is pending, a call to this function to enable    */
/*      preemption causes a context switch.                              */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      Application                                                      */
/*      TCSE_Change_Preemption              Error checking function      */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      [HIC_Make_History_Entry]            Make entry in history log    */
/*      [TCT_Check_Stack]                   Stack checking function      */
/*      TCT_Control_To_System               Transfer control to system   */
/*      TCT_Protect                         Protect scheduling info      */
/*      TCT_Set_Execute_Task                Set TCD_Execute_Task pointer */
/*      TCT_Unprotect                       Release protection of info   */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      preempt                             Preempt selection parameter  */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      old_preempt                         Original preempt value       */
/*                                                                       */
/* HISTORY                                                               */
/*                                                                       */
/*        DATE                    REMARKS                                */
/*                                                                       */
/*      03-01-1993      Created initial version 1.0                      */
/*      04-19-1993      Verified version 1.0                             */
/*      03-01-1994      Modified protection logic,                       */
/*                      resulting in version 1.1                         */
/*                                                                       */
/*      03-18-1994      Verified version 1.1                             */
/*                                                                       */
/*************************************************************************/
OPTION   TCS_Change_Preemption(OPTION preempt)
{

TC_TCB         *task;                       /* Pointer to task           */
OPTION          old_preempt;
NU_SUPERV_USER_VARIABLES

    /* Switch to supervisor mode */
    NU_SUPERVISOR_MODE();

#ifdef  NU_ENABLE_STACK_CHECK

    /* Call stack checking function to check for an overflow condition.  */
    TCT_Check_Stack();

#endif

#ifdef  NU_ENABLE_HISTORY

    /* Make an entry that corresponds to this function in the system history
       log.  */
    HIC_Make_History_Entry(NU_CHANGE_PREEMPTION_ID, (UNSIGNED) preempt,
                                        (UNSIGNED) 0, (UNSIGNED) 0);

#endif

    /* Protect the scheduling information.  */
    TCT_Protect(&TCD_System_Protect);

    /* Pickup the current thread and place it in the task pointer.  */
    task =  (TC_TCB *) TCD_Current_Thread;

    /* Save the old preempt value.  */
    if (task -> tc_preemption)

        /* Previously enabled.  */
        old_preempt =  NU_PREEMPT;
    else

        /* Previously disabled.  */
        old_preempt =  NU_NO_PREEMPT;

    /* Process the new value.  */
    if (preempt == NU_NO_PREEMPT)

        /* Disable preemption.  */
        TCD_Execute_Task -> tc_preemption =  NU_FALSE;
    else
    {

        /* Enable preemption.  */
        task -> tc_preemption =  NU_TRUE;

        /* Check for a preemption condition.  */
        if ((task == TCD_Execute_Task) &&
            (TCD_Highest_Priority < ((INT) TCD_Execute_Task -> tc_priority)))
        {

            /* Preempt the current task.  */
            TCT_Set_Execute_Task(TCD_Priority_List[TCD_Highest_Priority]);

            /* Transfer control to the system.  */
            TCT_Control_To_System();
        }
    }

#ifdef INCLUDE_PROVIEW
    _RTProf_DumpTask(task,RT_PROF_CHANGE_PREEMPTION);
#endif

    /* Release protection of information.  */
    TCT_Unprotect();

    /* Return to user mode */
    NU_USER_MODE();

    /* Return the previous preemption posture.  */
    return(old_preempt);
}


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      TCS_Change_Time_Slice                                            */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function changes the time slice of the specified task.  A   */
/*      time slice value of 0 disables time slicing.                     */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      Application                                                      */
/*      TCES_Change_Preemption              Error checking function      */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      [HIC_Make_History_Entry]            Make entry in history log    */
/*      [TCT_Check_Stack]                   Stack checking function      */
/*      TCT_Protect                         Protect scheduling info      */
/*      TCT_Unprotect                       Release protection of info   */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      task_ptr                            Task control block pointer   */
/*      time_slice                          New time slice value         */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      old_time_slice                      Original time slice value    */
/*                                                                       */
/* HISTORY                                                               */
/*                                                                       */
/*         DATE                    REMARKS                               */
/*                                                                       */
/*      03-01-1993      Created initial version 1.0                      */
/*      04-19-1993      Verified version 1.0                             */
/*      03-01-1994      Modified function interface,                     */
/*                      added register optimizations,                    */
/*                      modified protection logic,                       */
/*                      resulting in version 1.1                         */
/*                                                                       */
/*      03-18-1994      Verified version 1.1                             */
/*                                                                       */
/*************************************************************************/
UNSIGNED   TCS_Change_Time_Slice(NU_TASK *task_ptr, UNSIGNED time_slice)
{

TC_TCB         *task;                       /* Task control block ptr    */
UNSIGNED        old_time_slice;             /* Old time slice value      */
NU_SUPERV_USER_VARIABLES

    /* Switch to supervisor mode */
    NU_SUPERVISOR_MODE();

    /* Move input task control block pointer into internal pointer.  */
    task =  (TC_TCB *) task_ptr;