if (task == NU_NULL)
    
        /* Error, suspend request probably from initialization.  */
        status =  NU_TRUE;
        
    else if (task -> tc_id != TC_TASK_ID)

        /* Control block is probably an HISR not a task.  */
        status =  NU_TRUE;

    else if (task -> tc_signal_active)
    
        /* Called from a signal handler.  */
        status =  NU_TRUE;
        
    /* Return status to caller.  */
    return(status);
}


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      TCCE_Activate_HISR                                               */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function performs error checking on the parameters supplied */
/*      to the activate HISR function.                                   */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      Application                                                      */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      TCT_Activate_HISR                   Actual HISR activate call    */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      hisr_ptr                            HISR control block pointer   */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      NU_INVALID_HISR                     Invalid HISR pointer         */
/*                                                                       */
/* 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,                  */
/*                        resulting in version 1.1                       */
/*                                                                       */
/*      03-18-1994      Verified version 1.1                             */
/*                                                                       */
/*************************************************************************/
STATUS  TCCE_Activate_HISR(NU_HISR *hisr_ptr)
{

TC_HCB         *hisr;                       /* HISR control block ptr    */
STATUS          status;                     /* Completion status         */
NU_SUPERV_USER_VARIABLES

    NU_SUPERVISOR_MODE();
    /* Move input HISR control block pointer into internal pointer.  */
    hisr =  (TC_HCB *) hisr_ptr;

    /* Check each parameter.  */
    if (hisr == NU_NULL)
    
        /* Invalid HISR control block pointer.  */
        status =  NU_INVALID_HISR;

    else if (hisr -> tc_id != TC_HISR_ID)
    
        /* Invalid HISR control block pointer.  */
        status =  NU_INVALID_HISR;
        
    else
    
        /* Call the routine to activate the HISR.  */
        status =  TCT_Activate_HISR(hisr_ptr);

    /* Return to user mode */
    NU_USER_MODE();
        
    /* Return completion status.  */
    return(status);
}


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      TCCE_Validate_Resume                                             */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function validates the resume service and resume driver     */
/*      calls with scheduling protection around the examination of the   */
/*      task status.                                                     */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      IOCE_Resume_Driver                  Driver error checking funct. */
/*      TCCE_Resume_Service                 Error checking function      */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      TCT_Set_Current_Protect             Setup current protect pointer*/
/*      TCT_System_Protect                  Protect from system access   */
/*      TCT_System_Unprotect                Release system protection    */
/*      TCT_Unprotect                       Release current protection   */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      resume_type                         Type of resume request       */
/*      task_ptr                            Task control block pointer   */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      NU_TRUE                             Invalid resume               */
/*      NU_FALSE                            Valid resume                 */
/*                                                                       */
/* HISTORY                                                               */
/*                                                                       */
/*         DATE                    REMARKS                               */
/*                                                                       */
/*      03-01-1994      Created initial version of                       */
/*                        function for version 1.0g                      */
/*      03-01-1994      Verified version 1.0g                            */
/*      03-01-1994      Modified function interface,                     */
/*                        added register optimizations,                  */
/*                        added system protection logic,                 */
/*                        moved to TCCE since it is an                   */
/*                        error interface function,                      */
/*                        resulting in version 1.1                       */
/*                                                                       */
/*      03-18-1994      Verified version 1.1                             */
/*      10-16-1996      Modified to save the current                     */
/*                        thread's protection rather                     */
/*                        than that of the task being                    */
/*                        resumed (SPR212)(SPR268)                       */
/*                                                                       */
/*************************************************************************/
STATUS  TCCE_Validate_Resume(OPTION resume_type, NU_TASK *task_ptr)
{

R1 TC_TCB      *task;                       /* Task control block ptr    */
TC_PROTECT     *save_protect;               /* Save current protection   */
STATUS          status;                     /* Return status variable    */
NU_SUPERV_USER_VARIABLES

    NU_SUPERVISOR_MODE();

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

    /* Save current protection.  */
    if (TCD_Current_Thread != NU_NULL)
    {
        save_protect = TCT_Get_Current_Protect();
    }
    else
    {
        save_protect = NU_NULL;
    }

    /* Protect the scheduling structures from multiple access.  */
    TCT_System_Protect();
    
    /* Does the resume type match the current status?  */
    if (task -> tc_status == resume_type)

        /* Indicate that there is no error.  */
        status =  NU_FALSE;
    
    /* Check for a resumption of a delayed pure suspend.  */
    else if ((resume_type == NU_PURE_SUSPEND) && (task -> tc_delayed_suspend))
        
        /* Indicate that there is no error.  */
        status =  NU_FALSE;
            
    /* Check for a signal active and the saved status the same as
       the resume request.  */
    else if ((resume_type == task -> tc_saved_status) &&
            (task -> tc_signal_active))

        /* Indicate that there is no error.  */
        status =  NU_FALSE;
        
    else
    
        /* Indicate that there is an error.  */
        status =  NU_TRUE;

    /* Determine how to get out of protection.  */
    if (save_protect)
    {

        /* Restore current protection.  */
        TCT_Set_Current_Protect(save_protect);

        /* Release system protect.  */
        TCT_System_Unprotect();
    }
    else

        /* Release protection of system structures.  */
        TCT_Unprotect();
            
    /* Return to user mode */
    NU_USER_MODE();
    
    /* Return status to caller.  */
    return(status);
}