smc.c

test file nucleus source

                /* FIFO suspension is required.  Link the suspend block into
                   the list of suspended tasks on this semaphore.  */
                CSC_Place_On_List((CS_NODE **)
                        &(semaphore -> sm_suspension_list),
                                        &(suspend_ptr -> sm_suspend_link));
            }
            else
            {

                /* Get the priority of the current thread so the suspend block
                   can be placed in the appropriate place.  */
                suspend_ptr -> sm_suspend_link.cs_priority =
                                                    TCC_Task_Priority(task);

                CSC_Priority_Place_On_List((CS_NODE **)
                        &(semaphore -> sm_suspension_list),
                                        &(suspend_ptr -> sm_suspend_link));
            }

            /* Finally, suspend the calling task. Note that the suspension call
               automatically clears the protection on the semaphore.  */
            TCC_Suspend_Task((NU_TASK *) task, NU_SEMAPHORE_SUSPEND,
                                        SMC_Cleanup, suspend_ptr, suspend);

            /* Pickup the return status.  */
            status =  suspend_ptr -> sm_return_status;
        }
        else
        {
            /* No suspension requested.  Simply return an error status.  */
            status =  NU_UNAVAILABLE;

#ifdef INCLUDE_PROVIEW
            _RTProf_DumpSema(RT_PROF_OBTAIN_SEMAPHORE, semaphore,RT_PROF_FAIL);
#endif
        }
    }

    /* Release protection against access to the semaphore.  */
    TCT_Unprotect();

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

    /* Return the completion status.  */
    return(status);
}


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      SMC_Release_Semaphore                                            */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function releases a previously obtained semaphore.  If one  */
/*      or more tasks are waiting, the first task is given the released  */
/*      instance of the semaphore.  Otherwise, the semaphore instance    */
/*      counter is simply incremented.                                   */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      Application                                                      */
/*      SMCE_Release_Semaphore              Error checking shell         */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      CSC_Remove_From_List                Remove from suspend list     */
/*      [HIC_Make_History_Entry]            Make entry in history log    */
/*      TCC_Resume_Task                     Resume a suspended task      */
/*      [TCT_Check_Stack]                   Stack checking function      */
/*      TCT_Control_To_System               Transfer control to system   */
/*      TCT_System_Protect                  Protect semaphore            */
/*      TCT_Unprotect                       Release protection           */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      semaphore_ptr                       Semaphore control block ptr  */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      NU_SUCCESS                                                       */
/*                                                                       */
/* HISTORY                                                               */
/*                                                                       */
/*        DATE                    REMARKS                                */
/*                                                                       */
/*      03-01-1993      Created initial version 1.0                      */
/*      04-19-1993      Verified version 1.0                             */
/*      03-01-1994      Changed function interfaces to                   */
/*                      match those in prototype,                        */
/*                      added register options, changed                  */
/*                      protection logic to reduce                       */
/*                      overhead, resulting in                           */
/*                      version 1.1                                      */
/*                                                                       */
/*      03-18-1994      Verified version 1.1                             */
/*                                                                       */
/*************************************************************************/
STATUS  SMC_Release_Semaphore(NU_SEMAPHORE *semaphore_ptr)
{

R1 SM_SCB      *semaphore;                  /* Semaphore control blk ptr */
R2 SM_SUSPEND  *suspend_ptr;                /* Pointer to suspend block  */
STATUS          preempt;                    /* Preemption flag           */
STATUS          status;                     /* Completion status         */
NU_SUPERV_USER_VARIABLES

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

    /* Move input semaphore pointer into internal pointer.  */
    semaphore =  (SM_SCB *) semaphore_ptr;


#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_RELEASE_SEMAPHORE_ID, (UNSIGNED) semaphore,
                                        (UNSIGNED) 0, (UNSIGNED) 0);

#endif

    /* Initialize the status as successful.  */
    status =  NU_SUCCESS;

    /* Protect against simultaneous access to the semaphore.  */
    TCT_System_Protect();

    /* Determine if another task is waiting on the semaphore.  */
    if (semaphore -> sm_tasks_waiting)
    {

        /* Yes, another task is waiting for an instance of the semaphore.  */

        /* Decrement the number of tasks waiting counter.  */
        semaphore -> sm_tasks_waiting--;

#ifdef INCLUDE_PROVIEW
        _RTProf_DumpSema(RT_PROF_RELEASE_SEMAPHORE, semaphore,RT_PROF_OK);
#endif

        /* Remove the first suspended block from the list.  */
        suspend_ptr =  semaphore -> sm_suspension_list;
        CSC_Remove_From_List((CS_NODE **) &(semaphore -> sm_suspension_list),
                                &(suspend_ptr -> sm_suspend_link));

        /* Setup the appropriate return value.  */
        suspend_ptr -> sm_return_status =  NU_SUCCESS;

        /* Resume the suspended task.  */
        preempt =
            TCC_Resume_Task((NU_TASK *) suspend_ptr -> sm_suspended_task,
                                                       NU_SEMAPHORE_SUSPEND);

        /* Determine if a preempt condition is present.  */
        if (preempt)

            /* Transfer control to the system if the resumed task function
               detects a preemption condition.  */
            TCT_Control_To_System();
    }
    else
    {

        /* Increment the semaphore instance counter.  */
        semaphore -> sm_semaphore_count++;

#ifdef INCLUDE_PROVIEW
        _RTProf_DumpSema(RT_PROF_RELEASE_SEMAPHORE, semaphore,RT_PROF_OK);
#endif
    }

    /* Release protection against access to the semaphore.  */
    TCT_Unprotect();

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

    /* Return the completion status.  */
    return(status);
}


/*************************************************************************/
/*                                                                       */
/* FUNCTION                                                              */
/*                                                                       */
/*      SMC_Cleanup                                                      */
/*                                                                       */
/* DESCRIPTION                                                           */
/*                                                                       */
/*      This function is responsible for removing a suspension block     */
/*      from a semaphore.  It is not called unless a timeout or a task   */
/*      terminate is in progress.  Note that protection is already in    */
/*      effect - the same protection at suspension time.  This routine   */
/*      must be called from Supervisor mode in Supervisor/User mode      */
/*      switching kernels.                                               */
/*                                                                       */
/* CALLED BY                                                             */
/*                                                                       */
/*      TCC_Timeout                         Task timeout                 */
/*      TCC_Terminate                       Task terminate               */
/*                                                                       */
/* CALLS                                                                 */
/*                                                                       */
/*      CSC_Remove_From_List                Remove suspend block from    */
/*                                            the suspension list        */
/*                                                                       */
/* INPUTS                                                                */
/*                                                                       */
/*      information                         Pointer to suspend block     */
/*                                                                       */
/* OUTPUTS                                                               */
/*                                                                       */
/*      None                                                             */
/*                                                                       */
/* HISTORY                                                               */
/*                                                                       */
/*         DATE                    REMARKS                               */
/*                                                                       */
/*      03-01-1993      Created initial version 1.0                      */
/*      04-19-1993      Verified version 1.0                             */
/*                                                                       */
/*************************************************************************/
VOID  SMC_Cleanup(VOID *information)
{

SM_SUSPEND      *suspend_ptr;               /* Suspension block pointer  */
NU_SUPERV_USER_VARIABLES

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

    /* Use the information pointer as a suspend pointer.  */
    suspend_ptr =  (SM_SUSPEND *) information;

    /* By default, indicate that the service timed-out.  It really does not
       matter if this function is called from a terminate request since
       the task does not resume.  */
    suspend_ptr -> sm_return_status =  NU_TIMEOUT;

    /* Decrement the number of tasks waiting counter.  */
    (suspend_ptr -> sm_semaphore) -> sm_tasks_waiting--;

    /* Unlink the suspend block from the suspension list.  */
    CSC_Remove_From_List((CS_NODE **)
                &((suspend_ptr -> sm_semaphore) -> sm_suspension_list),
                                &(suspend_ptr -> sm_suspend_link));

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