μC/OS-II---互斥信号量管理1（os_mutex.c）

目录

  • 背景：优先级反转问题
  • 互斥信号量管理
    • 互斥信号量创建
    • 互斥信号量删除
    • 互斥信号量获取/等待

在这里插入图片描述

背景：优先级反转问题

  • 在高优先级任务等待低优先级任务释放资源时，第三个中等优先级任务抢占了低优先级任务。阻塞时间是无法预测的，可能导致高优先级任务无法满足deadline。这是需要解决的问题。μC/OS-II采用的办法：优先级继承协议。【实际采用的方法是由互斥信号量先预占一个优先级】

互斥信号量管理

互斥信号量创建

OS_EVENT  *OSMutexCreate (INT8U   prio,INT8U  *perr)
{OS_EVENT  *pevent;
#if OS_CRITICAL_METHOD == 3u                               /* Allocate storage for CPU status register */OS_CPU_SR  cpu_sr = 0u;
#endif
#ifdef OS_SAFETY_CRITICALif (perr == (INT8U *)0){OS_SAFETY_CRITICAL_EXCEPTION();return ((OS_EVENT *)0);}#endif
#ifdef OS_SAFETY_CRITICAL_IEC61508if (OSSafetyCriticalStartFlag == OS_TRUE){OS_SAFETY_CRITICAL_EXCEPTION();return ((OS_EVENT *)0);}#endif
#if OS_ARG_CHK_EN > 0uif (prio != OS_PRIO_MUTEX_CEIL_DIS){if (prio >= OS_LOWEST_PRIO)                        /* Validate PCP                             */{*perr = OS_ERR_PRIO_INVALID;return ((OS_EVENT *)0);}}#endifif (OSIntNesting > 0u)                                 /* See if called from ISR ...               */{*perr = OS_ERR_CREATE_ISR;                         /* ... can't CREATE mutex from an ISR       */return ((OS_EVENT *)0);}OS_ENTER_CRITICAL();if (prio != OS_PRIO_MUTEX_CEIL_DIS){if (OSTCBPrioTbl[prio] != (OS_TCB *)0)             /* Mutex priority must not already exist    */{OS_EXIT_CRITICAL();                            /* Task already exist at priority ...       */*perr = OS_ERR_PRIO_EXIST;                      /* ... ceiling priority                     */return ((OS_EVENT *)0);}OSTCBPrioTbl[prio] = OS_TCB_RESERVED;              /* Reserve the table entry                  */}pevent = OSEventFreeList;                              /* Get next free event control block        */if (pevent == (OS_EVENT *)0)                           /* See if an ECB was available              */{if (prio != OS_PRIO_MUTEX_CEIL_DIS){OSTCBPrioTbl[prio] = (OS_TCB *)0;              /* No, Release the table entry              */}OS_EXIT_CRITICAL();*perr = OS_ERR_PEVENT_NULL;                         /* No more event control blocks             */return (pevent);}OSEventFreeList     = (OS_EVENT *)OSEventFreeList->OSEventPtr; /* Adjust the free list             */OS_EXIT_CRITICAL();pevent->OSEventType = OS_EVENT_TYPE_MUTEX;pevent->OSEventCnt  = (INT16U) ((INT16U)prio << 8u) | OS_MUTEX_AVAILABLE; /* Resource is avail.     */pevent->OSEventPtr  = (void *)0;                       /* No task owning the mutex                 */
#if OS_EVENT_NAME_EN > 0upevent->OSEventName = (INT8U *) (void *)"?";
#endifOS_EventWaitListInit (pevent);*perr = OS_ERR_NONE;return (pevent);
}

互斥信号量删除

#if OS_MUTEX_DEL_EN > 0u
OS_EVENT  *OSMutexDel (OS_EVENT  *pevent,INT8U      opt,INT8U     *perr)
{BOOLEAN    tasks_waiting;OS_EVENT  *pevent_return;INT8U      pcp;                                        /* Priority ceiling priority                */INT8U      prio;OS_TCB    *ptcb;
#if OS_CRITICAL_METHOD == 3u                               /* Allocate storage for CPU status register */OS_CPU_SR  cpu_sr = 0u;
#endif
#ifdef OS_SAFETY_CRITICALif (perr == (INT8U *)0){OS_SAFETY_CRITICAL_EXCEPTION();return ((OS_EVENT *)0);}#endif
#if OS_ARG_CHK_EN > 0uif (pevent == (OS_EVENT *)0)                           /* Validate 'pevent'                        */{*perr = OS_ERR_PEVENT_NULL;return (pevent);}#endifif (pevent->OSEventType != OS_EVENT_TYPE_MUTEX)        /* Validate event block type                */{*perr = OS_ERR_EVENT_TYPE;return (pevent);}if (OSIntNesting > 0u)                                 /* See if called from ISR ...               */{*perr = OS_ERR_DEL_ISR;                             /* ... can't DELETE from an ISR             */return (pevent);}OS_ENTER_CRITICAL();if (pevent->OSEventGrp != 0u)                          /* See if any tasks waiting on mutex        */{tasks_waiting = OS_TRUE;                           /* Yes                                      */}else{tasks_waiting = OS_FALSE;                          /* No                                       */}switch (opt){case OS_DEL_NO_PEND:                               /* DELETE MUTEX ONLY IF NO TASK WAITING --- */if (tasks_waiting == OS_FALSE){
#if OS_EVENT_NAME_EN > 0upevent->OSEventName   = (INT8U *) (void *)"?";
#endifpcp                   = (INT8U) (pevent->OSEventCnt >> 8u);if (pcp != OS_PRIO_MUTEX_CEIL_DIS){OSTCBPrioTbl[pcp] = (OS_TCB *)0;      /* Free up the PCP                          */}pevent->OSEventType   = OS_EVENT_TYPE_UNUSED;pevent->OSEventPtr    = OSEventFreeList;  /* Return Event Control Block to free list  */pevent->OSEventCnt    = 0u;OSEventFreeList       = pevent;OS_EXIT_CRITICAL();*perr                 = OS_ERR_NONE;pevent_return         = (OS_EVENT *)0;    /* Mutex has been deleted                   */}else{OS_EXIT_CRITICAL();*perr                 = OS_ERR_TASK_WAITING;pevent_return         = pevent;}break;case OS_DEL_ALWAYS:                                /* ALWAYS DELETE THE MUTEX ---------------- */pcp  = (INT8U) (pevent->OSEventCnt >> 8u);                      /* Get PCP of mutex       */if (pcp != OS_PRIO_MUTEX_CEIL_DIS){prio = (INT8U) (pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8); /* Get owner's orig prio  */ptcb = (OS_TCB *)pevent->OSEventPtr;if (ptcb != (OS_TCB *)0)                  /* See if any task owns the mutex           */{if (ptcb->OSTCBPrio == pcp)           /* See if original prio was changed         */{OSMutex_RdyAtPrio (ptcb, prio);   /* Yes, Restore the task's original prio    */}}}while (pevent->OSEventGrp != 0u)              /* Ready ALL tasks waiting for mutex        */{(void)OS_EventTaskRdy (pevent, (void *)0, OS_STAT_MUTEX, OS_STAT_PEND_ABORT);}#if OS_EVENT_NAME_EN > 0upevent->OSEventName   = (INT8U *) (void *)"?";
#endifpcp                   = (INT8U) (pevent->OSEventCnt >> 8u);if (pcp != OS_PRIO_MUTEX_CEIL_DIS){OSTCBPrioTbl[pcp] = (OS_TCB *)0;          /* Free up the PCP                          */}pevent->OSEventType   = OS_EVENT_TYPE_UNUSED;pevent->OSEventPtr    = OSEventFreeList;      /* Return Event Control Block to free list  */pevent->OSEventCnt    = 0u;OSEventFreeList       = pevent;               /* Get next free event control block        */OS_EXIT_CRITICAL();if (tasks_waiting == OS_TRUE)                 /* Reschedule only if task(s) were waiting  */{OS_Sched();                               /* Find highest priority task ready to run  */}*perr         = OS_ERR_NONE;pevent_return = (OS_EVENT *)0;                /* Mutex has been deleted                   */break;default:OS_EXIT_CRITICAL();*perr         = OS_ERR_INVALID_OPT;pevent_return = pevent;break;}return (pevent_return);
}
#endif

互斥信号量获取/等待

void  OSMutexPend (OS_EVENT  *pevent,INT32U     timeout,INT8U     *perr)
{INT8U      pcp;                                        /* Priority Ceiling Priority (PCP)          */INT8U      mprio;                                      /* Mutex owner priority                     */BOOLEAN    rdy;                                        /* Flag indicating task was ready           */OS_TCB    *ptcb;OS_EVENT  *pevent2;INT8U      y;
#if OS_CRITICAL_METHOD == 3u                               /* Allocate storage for CPU status register */OS_CPU_SR  cpu_sr = 0u;
#endif
#ifdef OS_SAFETY_CRITICALif (perr == (INT8U *)0){OS_SAFETY_CRITICAL_EXCEPTION();return;}#endif
#if OS_ARG_CHK_EN > 0uif (pevent == (OS_EVENT *)0)                           /* Validate 'pevent'                        */{*perr = OS_ERR_PEVENT_NULL;return;}#endifif (pevent->OSEventType != OS_EVENT_TYPE_MUTEX)        /* Validate event block type                */{*perr = OS_ERR_EVENT_TYPE;return;}if (OSIntNesting > 0u)                                 /* See if called from ISR ...               */{*perr = OS_ERR_PEND_ISR;                           /* ... can't PEND from an ISR               */return;}if (OSLockNesting > 0u)                                /* See if called with scheduler locked ...  */{*perr = OS_ERR_PEND_LOCKED;                        /* ... can't PEND when locked               */return;}/*$PAGE*/OS_ENTER_CRITICAL();pcp = (INT8U) (pevent->OSEventCnt >> 8u);              /* Get PCP from mutex                       *//* Is Mutex available?                      */if ((INT8U) (pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8) == OS_MUTEX_AVAILABLE){pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8;       /* Yes, Acquire the resource                */pevent->OSEventCnt |= OSTCBCur->OSTCBPrio;         /*      Save priority of owning task        */pevent->OSEventPtr  = (void *)OSTCBCur;            /*      Point to owning task's OS_TCB       */if ((pcp != OS_PRIO_MUTEX_CEIL_DIS) &&(OSTCBCur->OSTCBPrio <= pcp))                  /*      PCP 'must' have a SMALLER prio ...  */{OS_EXIT_CRITICAL();                           /*      ... than current task!              */*perr = OS_ERR_PCP_LOWER;}else{OS_EXIT_CRITICAL();*perr = OS_ERR_NONE;}return;}if (pcp != OS_PRIO_MUTEX_CEIL_DIS){mprio = (INT8U) (pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8); /*  Get priority of mutex owner   */ptcb  = (OS_TCB *) (pevent->OSEventPtr);                  /*     Point to TCB of mutex owner   */if (ptcb->OSTCBPrio > pcp)                                /*     Need to promote prio of owner?*/{if (mprio > OSTCBCur->OSTCBPrio){y = ptcb->OSTCBY;if ((OSRdyTbl[y] & ptcb->OSTCBBitX) != 0u)        /*     See if mutex owner is ready   */{OSRdyTbl[y] &= (OS_PRIO)~ptcb->OSTCBBitX;     /*     Yes, Remove owner from Rdy ...*/if (OSRdyTbl[y] == 0u)                        /*          ... list at current prio */{OSRdyGrp &= (OS_PRIO)~ptcb->OSTCBBitY;}rdy = OS_TRUE;}else{pevent2 = ptcb->OSTCBEventPtr;if (pevent2 != (OS_EVENT *)0)                 /* Remove from event wait list       */{y = ptcb->OSTCBY;pevent2->OSEventTbl[y] &= (OS_PRIO)~ptcb->OSTCBBitX;if (pevent2->OSEventTbl[y] == 0u){pevent2->OSEventGrp &= (OS_PRIO)~ptcb->OSTCBBitY;}}rdy = OS_FALSE;                        /* No                                       */}ptcb->OSTCBPrio = pcp;                     /* Change owner task prio to PCP            */
#if OS_LOWEST_PRIO <= 63uptcb->OSTCBY    = (INT8U) ( ptcb->OSTCBPrio >> 3u);ptcb->OSTCBX    = (INT8U) ( ptcb->OSTCBPrio & 0x07u);
#elseptcb->OSTCBY    = (INT8U) ((INT8U) (ptcb->OSTCBPrio >> 4u) & 0xFFu);ptcb->OSTCBX    = (INT8U) ( ptcb->OSTCBPrio & 0x0Fu);
#endifptcb->OSTCBBitY = (OS_PRIO) (1uL << ptcb->OSTCBY);ptcb->OSTCBBitX = (OS_PRIO) (1uL << ptcb->OSTCBX);if (rdy == OS_TRUE)                        /* If task was ready at owner's priority ...*/{OSRdyGrp               |= ptcb->OSTCBBitY; /* ... make it ready at new priority.   */OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;}else{pevent2 = ptcb->OSTCBEventPtr;if (pevent2 != (OS_EVENT *)0)          /* Add to event wait list                   */{pevent2->OSEventGrp               |= ptcb->OSTCBBitY;pevent2->OSEventTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;}}OSTCBPrioTbl[pcp] = ptcb;}}}OSTCBCur->OSTCBStat     |= OS_STAT_MUTEX;         /* Mutex not available, pend current task        */OSTCBCur->OSTCBStatPend  = OS_STAT_PEND_OK;OSTCBCur->OSTCBDly       = timeout;               /* Store timeout in current task's TCB           */OS_EventTaskWait (pevent);                        /* Suspend task until event or timeout occurs    */OS_EXIT_CRITICAL();OS_Sched();                                       /* Find next highest priority task ready         */OS_ENTER_CRITICAL();switch (OSTCBCur->OSTCBStatPend)                  /* See if we timed-out or aborted                */{case OS_STAT_PEND_OK:*perr = OS_ERR_NONE;break;case OS_STAT_PEND_ABORT:*perr = OS_ERR_PEND_ABORT;               /* Indicate that we aborted getting mutex        */break;case OS_STAT_PEND_TO:default:OS_EventTaskRemove (OSTCBCur, pevent);*perr = OS_ERR_TIMEOUT;                  /* Indicate that we didn't get mutex within TO   */break;}OSTCBCur->OSTCBStat          =  OS_STAT_RDY;      /* Set   task  status to ready                   */OSTCBCur->OSTCBStatPend      =  OS_STAT_PEND_OK;  /* Clear pend  status                            */OSTCBCur->OSTCBEventPtr      = (OS_EVENT  *)0;    /* Clear event pointers                          */
#if (OS_EVENT_MULTI_EN > 0u)OSTCBCur->OSTCBEventMultiPtr = (OS_EVENT **)0;
#endifOS_EXIT_CRITICAL();
}

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