fasync_helper kill_fasync

最新推荐文章于 2025-10-06 20:42:58 发布

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最新推荐文章于 2025-10-06 20:42:58 发布 · 654 阅读

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CC 4.0 BY-SA版权

这篇博客详细介绍了Linux内核中用于字符设备驱动的异步通知机制，包括fasync_helper函数的使用，它用于初始化fasync_queue，以及kill_fasync函数，用于发送SIGIO信号到应用层。通过fcntl设置FASYNC标志，当设备状态改变时，驱动会调用.fasync方法，实现异步通知。

static struct fasync_struct *button_async;

static int fifth_drv_fasync (int fd, struct file *filp, int on)
{
return fasync_helper (fd, filp, on, &button_async); // 主要用于初始化button_async
}

/*
* fasync_helper() is used by some character device drivers (mainly mice)
* to set up the fasync queue. It returns negative on error, 0 if it did
* no changes and positive if it added/deleted the entry.
*/
int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
{
   struct fasync_struct *fa, **fp;
   struct fasync_struct *new = NULL;
   int result = 0;

   if (on) {
       new = kmem_cache_alloc(fasync_cache, GFP_KERNEL);