Re: [alsa-devel] snd_mixart_send_msg / snd_mixart_send_msg_wait_notif

At Tue, 18 Sep 2007 13:54:23 +0200, Rene Herman wrote:

Hi.

While looking through ALSA for schedule_timeout() calls, I ran into:

int snd_mixart_send_msg(...) {

[ ... ]

     set_current_state(TASK_UNINTERRUPTIBLE);
     add_wait_queue(&mgr->msg_sleep, &wait);
     spin_unlock_irq(&mgr->msg_lock);
     timeout = schedule_timeout(MSG_TIMEOUT_JIFFIES);
     remove_wait_queue(&mgr->msg_sleep, &wait);

     if (! timeout) {
             /* error - no ack */
             mutex_unlock(&mgr->msg_mutex);
             snd_printk(KERN_ERR "error: no reponse on msg %x\n", 

msg_frame); return -EIO; }

[ ... ]

}

and the same in snd_mixart_send_msg_wait_notif().

I believe there to be something wrong with this code. A schedule_timeout() in TASK_UNINTERRUPTIBLE is always going to return 0.

No, it returns the time left at the point it's woken up. *_uninterruptible() ignores signals but not wake_up() itself (otherwise it makes no sense). The description in the kernel comment is misleading indeed.

Takashi