轉自：csshuke
ucos V2.52
OSTimeTick()函數解析
調用處：os_cpu_a.asm裏_OSTickISR
函數所有源文件：os_core.c
代碼：
void OSTimeTick (void)
{
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
#endif
OS_TCB *ptcb;
OSTimeTickHook(); /* Call user definable hook */
#if OS_TIME_GET_SET_EN > 0
OS_ENTER_CRITICAL(); /* Update the 32-bit tick counter */
OSTime++; //(1)
OS_EXIT_CRITICAL();
#endif
if (OSRunning == TRUE) { //(2)
ptcb = OSTCBList; /* Point at first TCB in TCB list */
while (ptcb->OSTCBPrio != OS_IDLE_PRIO)
{ /* Go through all TCBs in TCB list */ //(3)
OS_ENTER_CRITICAL(); //(4)
if (ptcb->OSTCBDly != 0)
{ /* Delayed or waiting for event with TO */ //(5)
if (--ptcb->OSTCBDly == 0)
{ /* Decrement nbr of ticks to end of delay */ //(6)
if ((ptcb->OSTCBStat & OS_STAT_SUSPEND) == OS_STAT_RDY)
{ /* Is task suspended? */ //(7)
/* No, Make task R-to-R (timed out)*/
OSRdyGrp |= ptcb->OSTCBBitY;
OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX; //(8)
} else { /* Yes, Leave 1 tick to prevent loosing the task when the suspension is removed.*/
ptcb->OSTCBDly = 1; //(9)
}
}
}
ptcb = ptcb->OSTCBNext; /* Point at next TCB in TCB list */ //(10)
OS_EXIT_CRITICAL(); //(11)
}
}
}
{
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
#endif
OS_TCB *ptcb;
OSTimeTickHook(); /* Call user definable hook */
#if OS_TIME_GET_SET_EN > 0
OS_ENTER_CRITICAL(); /* Update the 32-bit tick counter */
OSTime++; //(1)
OS_EXIT_CRITICAL();
#endif
if (OSRunning == TRUE) { //(2)
ptcb = OSTCBList; /* Point at first TCB in TCB list */
while (ptcb->OSTCBPrio != OS_IDLE_PRIO)
{ /* Go through all TCBs in TCB list */ //(3)
OS_ENTER_CRITICAL(); //(4)
if (ptcb->OSTCBDly != 0)
{ /* Delayed or waiting for event with TO */ //(5)
if (--ptcb->OSTCBDly == 0)
{ /* Decrement nbr of ticks to end of delay */ //(6)
if ((ptcb->OSTCBStat & OS_STAT_SUSPEND) == OS_STAT_RDY)
{ /* Is task suspended? */ //(7)
/* No, Make task R-to-R (timed out)*/
OSRdyGrp |= ptcb->OSTCBBitY;
OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX; //(8)
} else { /* Yes, Leave 1 tick to prevent loosing the task when the suspension is removed.*/
ptcb->OSTCBDly = 1; //(9)
}
}
}
ptcb = ptcb->OSTCBNext; /* Point at next TCB in TCB list */ //(10)
OS_EXIT_CRITICAL(); //(11)
}
}
}
內容解釋：
(1)進入臨界段， OSTime++;
(2)如果os已開始運行（OSStart()已執行，則執行if裏面的語句;
(3)遍歷OSTCBList，直到idle task;
(4)進入臨界段
(5)如果ptcb->OSTCBDly不爲0，則需要處理
(6)--ptcb->OSTCBDly，如果自減後爲0
(7)如果任務不是由OSTaskSuspend()掛起的，由event掛起或只是OSTimeDly()掛起
(8)使該優先級的任務處於就緒態
(9)如果任務是由OSTaskSuspend()掛起的，則 ptcb->OSTCBDly重新置爲1.
(10)得OSTCBList鏈表的下一個os_tcb項。
(11)退出臨界段
1，重點解釋(9)，爲什麼的馬OSTaskSuspend()掛起的任務的ptcb->OSTCBDly重新置爲1呢？
對OSTimeTick()函數來說，ptcb->OSTCBDly=0的task它不處理。
被OSTackSuspend()掛起的任務，可以被OSTaskResume()解除掛狀態，所以OSTimeTick()有義務持續檢測被掛起的任務，所以要保持ptcb->OSTCBDly>0。
而對於非OSTackSuspend()掛起的任務，不管是由event掛起或只是OSTimeDly()掛起，既然設置了超時時間，當ptcb->OSTCBDly=0時就要置爲就緒態。
2，(8)是如何使任務進入就緒態的呢？
首先，通過OSRdyGrp和OSRdyTbl[ptcb->OSTCBY]賦值，告知OS此優先級的任務已經準備就緒；
然後，在OS_Sched()裏尋找最高優先級任務，做任務切換。
3，(5)，ptcb->OSTCBDly!=0人有一種情況，此任務是等待狀態的任務。可是是因爲event掛起或只是OSTimeDly()掛起。
ptcb->OSTCBDly=0有三種情況，一種是此任務是運行態的任務；第二種是此任務是就緒態的任務；第三種是此任務是等待狀態的任務，等待某個event，且timeout設置爲0.