Re: [PATCH] interrupt driven hvc_console as vio device

[Ryan Arnold <rsa@us.ibm.com>]

On Tue, 2004-08-24 at 23:46, Andrew Morton wrote:
> >  static void hvc_close(struct tty_struct *tty, struct file * filp)
> >   {
> > ...
> >  +		while (hp->n_outbuf) {
> >  +			spin_unlock_irqrestore(&hp->lock, flags);
> >  +			yield();
> >  +			spin_lock_irqsave(&hp->lock, flags);
> >  +		}
> 
> ick.
> 
> I suspect that if the caller of hvc_close() has realtime scheduling policy,
> this locks up.  Unless it's waiting for interrupt activity.
> 
> Really, a real sleep/wakeup would be tons better.

Paulus suggested that tty_wait_until_sent() would be most appropriate
since it actually does a sleep/wakeup.  I think I'll rearrange this
function a bit so that I won't have to drop the spin_lock and then grab
it again as well.  Thanks for the suggestion.

Ryan S. Arnold
IBM Linux Technology Center