Linux设备驱动中的并发控制

schedule(); //调剂其他过程履行

if (signal_pending(current)) //如不雅是因为旌旗灯号唤醒 {

ret = - ERESTARTSYS; goto out2;

}

down(&dev->sem); //获得旌旗灯号量 } /*大年夜用户空间拷贝到内核空间*/

if (count > GLOBALFIFO_SIZE - dev->current_len)

count = GLOBALFIFO_SIZE - dev->current_len; if (copy_from_user(dev->mem + dev->current_len, buf, count))

{

ret = - EFAULT; goto out;

} else

{

dev->current_len += count;

printk(KERN_INFO "written %d bytes(s),current_len:%d\n", count, dev ->current_len);

wake_up_interruptible(&dev->r_wait); //唤醒读等待队列

ret = count;

}

tasklet_schedule(&dev->tlet);

printk("in write jiffies=%ld\n",jiffies); out: up(&dev->sem); //释放旌旗灯号量

out2:remove_wait_queue(&dev->w_wait, &wait); //大年夜从属的等待队列头移除 set_current_state(TASK_RUNNING); return ret;

}/*文件操作构造体*/static const struct file_operations globalfifo_fops ={

.owner = THIS_MODULE,

.read = globalfifo_read,

.write = globalfifo_write,

.ioctl = globalfifo_ioctl,

.poll = globalfifo_poll,

.open = globalfifo_open,

.release = globalfifo_release,

};/*初始化并注册cdev*/static void globalfifo_setup_cdev(struct globalfifo_dev *dev, int index)

{ int err, devno = MKDEV(globalfifo_major, index);

cdev_init(&dev->cdev, &globalfifo_fops);

dev->cdev.owner = THIS_MODULE;

dev->cdev.ops = &globalfifo_fops;

err = cdev_add(&dev->cdev, devno, 1); if (err)

printk(KERN_NOTICE

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