[UCOS III source code analysis] - wait for multiple kernel objects

One 、 Wait for multiple kernel objects

here ucos There are certain restrictions on waiting for multiple kernel objects , And this function also has some disadvantages

1、 Waiting for multiple kernel objects can only be semaphores or message queues , Cannot be another kernel object , But there are many .

2、 Waiting for multiple kernel objects will release the wait because one of them is released , It doesn't need to wait until all kernel objects are released .

Wait function ：OSPendMulti It mainly contains these contents

valid = OS_PendMultiValidate(p_pend_data_tbl,           /* -------- Validate objects to be OS_SEM or OS_Q ------- */
                                 tbl_size);


//------------------------------------------------------------------------------
CPU_BOOLEAN  OS_PendMultiValidate (OS_PEND_DATA  *p_pend_data_tbl,
                                   OS_OBJ_QTY     tbl_size)
{
    OS_OBJ_QTY  i;
    OS_OBJ_QTY  ctr;
#if OS_CFG_SEM_EN  > 0u
    OS_SEM      *p_sem;
#endif
#if OS_CFG_Q_EN > 0u
    OS_Q        *p_q;
#endif


    for (i = 0u; i < tbl_size; i++) {
        if (p_pend_data_tbl->PendObjPtr == (OS_PEND_OBJ *)0) {   /* All .PendObjPtr in the table MUST be non NULL     */
            return (DEF_FALSE);
        }

        ctr = 0u;
#if OS_CFG_SEM_EN  > 0u
        p_sem = (OS_SEM *)((void *)p_pend_data_tbl->PendObjPtr); /* All objects to pend on must be of type OS_SEM ... */
        if (p_sem->Type == OS_OBJ_TYPE_SEM) {
            ctr++;
        }
#endif

#if OS_CFG_Q_EN > 0u
        p_q = (OS_Q *)((void *)p_pend_data_tbl->PendObjPtr);     /* ... or of type OS_Q                               */
        if (p_q->Type == OS_OBJ_TYPE_Q) {
            ctr++;
        }
#endif

        if (ctr == (OS_OBJ_QTY)0) {
            return (DEF_FALSE);                                  /* Found at least one invalid object type            */
        }
        p_pend_data_tbl++;
    }
    return (DEF_TRUE);
}

In addition to routine parameter checking, the first one is the function called , There will be a cycle to check which array you have set to wait, and whether the waiting object in it has been set , If it is not set, return directly . The next step is to check how many semaphores or message queues are in your settings , Yes, once ++ once , So you go to the last if When you are ctr Definitely not 0, Because the multiple kernel objects you set that need to wait will definitely meet the above two if bring ctr++ A few times . Return to the correct definition .

Then call this

 nbr_obj_rdy = OS_PendMultiGetRdy(p_pend_data_tbl,       /* --------- SEE IF OBJECT(s) HAVE BEEN POSTED ---------- */
                                     tbl_size);

//--------------------------------------------------------------------------------------
OS_OBJ_QTY  OS_PendMultiGetRdy (OS_PEND_DATA  *p_pend_data_tbl,
                                OS_OBJ_QTY     tbl_size)
{
    OS_OBJ_QTY   i;
    OS_OBJ_QTY   nbr_obj_rdy;
#if OS_CFG_Q_EN > 0u
    OS_ERR       err;
    OS_MSG_SIZE  msg_size;
    OS_Q        *p_q;
    void        *p_void;
    CPU_TS       ts;
#endif
#if OS_CFG_SEM_EN  > 0u
    OS_SEM      *p_sem;
#endif



    nbr_obj_rdy = (OS_OBJ_QTY)0;
    for (i = 0u; i < tbl_size; i++) {
        p_pend_data_tbl->RdyObjPtr  = (void         *)0;         /* Clear all fields                                  */
        p_pend_data_tbl->RdyMsgPtr  = (void         *)0;
        p_pend_data_tbl->RdyMsgSize = (OS_MSG_SIZE   )0;
        p_pend_data_tbl->RdyTS      = (CPU_TS        )0;
        p_pend_data_tbl->NextPtr    = (OS_PEND_DATA *)0;
        p_pend_data_tbl->PrevPtr    = (OS_PEND_DATA *)0;
        p_pend_data_tbl->TCBPtr     = (OS_TCB       *)0;
#if OS_CFG_Q_EN > 0u
        p_q = (OS_Q *)((void *)p_pend_data_tbl->PendObjPtr);     /* Assume we are pointing to a message queue object  */
        if (p_q->Type == OS_OBJ_TYPE_Q) {                        /* Is it a message queue?                            */
            p_void = OS_MsgQGet(&p_q->MsgQ,                      /* Yes, Any message waiting in the message queue?    */
                                &msg_size,
                                &ts,
                                &err);
            if (err == OS_ERR_NONE) {
                p_pend_data_tbl->RdyObjPtr  = p_pend_data_tbl->PendObjPtr;
                p_pend_data_tbl->RdyMsgPtr  = p_void;            /*      Yes, save the message received               */
                p_pend_data_tbl->RdyMsgSize = msg_size;
                p_pend_data_tbl->RdyTS      = ts;
                nbr_obj_rdy++;
            }
        }
#endif

#if OS_CFG_SEM_EN > 0u
        p_sem = (OS_SEM *)((void *)p_pend_data_tbl->PendObjPtr); /* Assume we are pointing to a semaphore object      */
        if (p_sem->Type == OS_OBJ_TYPE_SEM) {                    /* Is it a semaphore?                                */
            if (p_sem->Ctr > 0u) {                               /* Yes, Semaphore has been signaled?                 */
                p_sem->Ctr--;                                    /*      Yes, caller may proceed                      */
                p_pend_data_tbl->RdyObjPtr  = p_pend_data_tbl->PendObjPtr;
                p_pend_data_tbl->RdyTS      = p_sem->TS;
                nbr_obj_rdy++;
            }
        }
#endif

        p_pend_data_tbl++;
    }
    return (nbr_obj_rdy);
}

The words here can be roughly divided into three parts , Set initial value 0, Get whether it is a message queue. If yes , fill , Get whether it is a semaphore , If yes, fill ,nbr_obj_rdy This variable represents how many kernel objects you get that need to wait .

It is to use the return value just now to judge again , Did you get the kernel object , At this time, there are two kinds

1、 Got it , This is very simple, just return directly , Just finish the function

if (nbr_obj_rdy > (OS_OBJ_QTY)0) {
        CPU_CRITICAL_EXIT();
        *p_err = OS_ERR_NONE;
        return ((OS_OBJ_QTY)nbr_obj_rdy);
    }

2、 Didn't get , At this time, it depends on whether you are blocking or non blocking

Non blocking ： Exit back 0

Blocking ： call OS_PendMultiWait, Explained below

 if ((opt & OS_OPT_PEND_NON_BLOCKING) != (OS_OPT)0) {    /* Caller wants to block if not available?                */
        CPU_CRITICAL_EXIT();
        *p_err = OS_ERR_PEND_WOULD_BLOCK;                   /* No                                                     */
        return ((OS_OBJ_QTY)0);
    } else {
        if (OSSchedLockNestingCtr > (OS_NESTING_CTR)0) {    /* Can't pend when the scheduler is locked                */
            CPU_CRITICAL_EXIT();
            *p_err = OS_ERR_SCHED_LOCKED;
            return ((OS_OBJ_QTY)0);
        }
    }
    OS_CRITICAL_ENTER_CPU_CRITICAL_EXIT();                  /* Lock the scheduler/re-enable interrupts                */
                                                            /* ------ NO OBJECT READY, PEND ON MULTIPLE OBJECTS ----- */
    OS_PendMultiWait(p_pend_data_tbl,                       /* Suspend task until object posted or timeout occurs     */
                     tbl_size,
                     timeout);

    OS_CRITICAL_EXIT_NO_SCHED();

OS_PendMultiWait(p_pend_data_tbl,                       /* Suspend task until object posted or timeout occurs     */
                     tbl_size,
                     timeout);
//------------------------------------------------------------------------------------
void  OS_PendMultiWait (OS_PEND_DATA  *p_pend_data_tbl,
                        OS_OBJ_QTY     tbl_size,
                        OS_TICK        timeout)
{
    OS_OBJ_QTY      i;
    OS_PEND_LIST   *p_pend_list;

#if OS_CFG_Q_EN > 0u
    OS_Q           *p_q;
#endif

#if OS_CFG_SEM_EN > 0u
    OS_SEM         *p_sem;
#endif



    OSTCBCurPtr->PendOn             = OS_TASK_PEND_ON_MULTI;   /* Resource not available, wait until it is            */
    OSTCBCurPtr->PendStatus         = OS_STATUS_PEND_OK;
    OSTCBCurPtr->PendDataTblEntries = tbl_size;
    OSTCBCurPtr->PendDataTblPtr     = p_pend_data_tbl;

    OS_TaskBlock(OSTCBCurPtr,                                  /* Block the task waiting for object to be posted ...  */
                 timeout);                                     /* ... but with a timeout if not                       */

    for (i = 0u; i < tbl_size; i++) {
        p_pend_data_tbl->TCBPtr = OSTCBCurPtr;                 /* Every entry points back to the TCB of the task      */

#if OS_CFG_SEM_EN > 0u
        p_sem = (OS_SEM *)((void *)p_pend_data_tbl->PendObjPtr);
        if (p_sem->Type == OS_OBJ_TYPE_SEM) {
            p_pend_list = &p_sem->PendList;
            OS_PendListInsertPrio(p_pend_list,
                                  p_pend_data_tbl);
        }
#endif

#if OS_CFG_Q_EN > 0u
        p_q = (OS_Q *)((void *)p_pend_data_tbl->PendObjPtr);
        if (p_q->Type == OS_OBJ_TYPE_Q) {
            p_pend_list = &p_q->PendList;
            OS_PendListInsertPrio(p_pend_list,
                                  p_pend_data_tbl);
        }
#endif

        p_pend_data_tbl++;
    }
}

Here is the function mentioned above , It is to save the current task status that needs to be suspended and waited （ Wait for multiple kernel objects , Number of waits , Actively suspend ） If there is a timeout, it will be added to the clock reference list , Remove... From the ready list , Remove from the ready list . Follow up on , The kernel objects your task is waiting for , Insert them into the corresponding waiting list respectively （ Pointer auto increment cycle ）.

3、 Task scheduling , Here, if you wait for any one, you will return here to continue running , Then the whole function returns a 1, Then the function ends .

OSSched();                                              /* Find next highest priority task ready                  */

    CPU_CRITICAL_ENTER();
    switch (OSTCBCurPtr->PendStatus) {
        case OS_STATUS_PEND_OK:                             /* We got one of the objects posted to                    */
             *p_err = OS_ERR_NONE;
             break;

        case OS_STATUS_PEND_ABORT:                          /* Indicate that the multi-pend was aborted               */
             *p_err = OS_ERR_PEND_ABORT;
             break;

        case OS_STATUS_PEND_TIMEOUT:                        /* Indicate that we didn't get semaphore within timeout   */
             *p_err = OS_ERR_TIMEOUT;
             break;

        case OS_STATUS_PEND_DEL:                            /* Indicate that an object pended on has been deleted     */
             *p_err = OS_ERR_OBJ_DEL;
            break;

        default:
             *p_err = OS_ERR_STATUS_INVALID;
             break;
    }

    OSTCBCurPtr->PendStatus = OS_STATUS_PEND_OK;
    CPU_CRITICAL_EXIT();

    return ((OS_OBJ_QTY)1);