Re: es1371 driver

[Jaroslav Kysela <perex@suse.cz>]

On Thu, 21 Feb 2002, Wilmer van der Gaast wrote:

> (I found two addresses for Thomas, which one is the right one?)
>
> Hello,
>
> My computer has a SB PCI128 card and works perfectly with it. But, one
> strange thing with the current Linux driver for it. Here a piece from
> es1381_open:
>
> 	/* wait for device to become free */
> 	down(&s->open_sem);
> 	while (s->open_mode & file->f_mode) {
> 		if (file->f_flags & O_NONBLOCK) {
> 			up(&s->open_sem);
> 			return -EBUSY;
> 		}
> 		add_wait_queue(&s->open_wait, &wait);
> 		__set_current_state(TASK_INTERRUPTIBLE);
> 		up(&s->open_sem);
> 		schedule();
> 		remove_wait_queue(&s->open_wait, &wait);
> 		set_current_state(TASK_RUNNING);
> 		if (signal_pending(current))
> 			return -ERESTARTSYS;
> 		down(&s->open_sem);
> 	}
>
> Why does it wait? When I play an MP3 and meanwhile accidentally visit a
> website which uses Flash, the whole Mozilla process freezes because it can't
> get /dev/dsp. Maybe all programs should be blamed for opening /dev/dsp
> without O_NONBLOCK, but for me altering this piece of kernel code worked a
> lot better. Now any open() is handled as O_NONBLOCK and I don't get those
> crashes anymore.
>
> Anyway, why this crashy behaviour by default? :-/

Applications are ignoring standards. For further defails see:

http://www.unix-systems.org/onlinepubs/7908799/xsh/open.html

Especially this sentence:

If O_NONBLOCK is clear:
	The open() function will block the calling thread until the device
is ready or available before returning.

						Jaroslav

-----
Jaroslav Kysela <perex@suse.cz>
Linux Kernel Sound Maintainer
ALSA Project  http://www.alsa-project.org
SuSE Linux    http://www.suse.com