Method wait

lab8/src/6/src/kernel/program.cpp:566–622

}

int ProgramManager::wait(int *retval)
{
    PCB *child;
    ListItem *item;
    bool interrupt, flag;

    while (true)
    {
        interrupt = interruptManager.getInterruptStatus();
        interruptManager.disableInterrupt();

        item = this->allPrograms.head.next;

        // 查找子进程
        flag = true;
        while (item)
        {
            child = ListItem2PCB(item, tagInAllList);
            if (child->parentPid == this->running->pid)
            {
                flag = false;
                if (child->status == ProgramStatus::DEAD)
                {
                    break;
                }
            }
            item = item->next;
        }

        if (item) // 找到一个可返回的子进程
        {
            if (retval)
            {
                *retval = child->retValue;
            }

            int pid = child->pid;
            releasePCB(child);
            interruptManager.setInterruptStatus(interrupt);
            return pid;
        }
        else 
        {
            if (flag) // 子进程已经返回
            {
                
                interruptManager.setInterruptStatus(interrupt);
                return -1;
            }
            else // 存在子进程，但子进程的状态不是DEAD
            {
                interruptManager.setInterruptStatus(interrupt);
                schedule();
            }
        }
    }
}