建议楼主看下UCOS源码，里面写的很清楚，如果当前指定优先级的任务之前不是挂起状态，则直接返回，否则，会清除挂起标志，并判断是否进入就绪状态，接着继续判断多任务调度标志是否置位，如果已经置位，那么发生任务调度！！
#if OS_TASK_SUSPEND_EN > 0
INT8U OSTaskResume (INT8U prio)
{
OS_TCB *ptcb;
#if OS_CRITICAL_METHOD == 3 /* Storage for CPU status register */
OS_CPU_SR cpu_sr = 0;
#endif
#if OS_ARG_CHK_EN > 0
if (prio >= OS_LOWEST_PRIO) { /* Make sure task priority is valid */
return (OS_ERR_PRIO_INVALID);
}
#endif
OS_ENTER_CRITICAL();
ptcb = OSTCBPrioTbl[prio];
if (ptcb == (OS_TCB *)0) { /* Task to suspend must exist */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_RESUME_PRIO);
}
if (ptcb == OS_TCB_RESERVED) { /* See if assigned to Mutex */
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_NOT_EXIST);
}
if ((ptcb->OSTCBStat & OS_STAT_SUSPEND) != OS_STAT_RDY) { /* Task must be suspended */
ptcb->OSTCBStat &= ~(INT8U)OS_STAT_SUSPEND; /* Remove suspension */
if (ptcb->OSTCBStat == OS_STAT_RDY) { /* See if task is now ready */
if (ptcb->OSTCBDly == 0) {
OSRdyGrp |= ptcb->OSTCBBitY; /* Yes, Make task ready to run */
OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
OS_EXIT_CRITICAL();
if (OSRunning == OS_TRUE) {
OS_Sched(); /* Find new highest priority task */
}
} else {
OS_EXIT_CRITICAL();
}
} else { /* Must be pending on event */
OS_EXIT_CRITICAL();
}
return (OS_ERR_NONE);
}
OS_EXIT_CRITICAL();
return (OS_ERR_TASK_NOT_SUSPENDED);
}
#endif
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楼主
