Re: [PATCH] interrupt driven hvc_console as vio device

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

On Tue, 2004-08-24 at 23:49, Andrew Morton wrote:

> >  +	spin_lock_irqsave(&hp->lock, flags);
> >  +	retval = N_OUTBUF - hp->n_outbuf;
> >  +	spin_unlock_irqrestore(&hp->lock, flags);

> The new locking in these functions doesn't really do anything, apart from
> adding memory barriers.  If that's what you really want, I suggest you
> simply add (commented) memory barriers.

Since chars_in_buffer() can be called from the tty write task and the
n_outbuf value is changed from the hvc_console task I didn't want there
to be any confusion as to the real value of the variable when
chars_in_buffer() was reading it.  Is this the proper scenario for a
memory barrier?

Ryan S. Arnold
IBM Linux Technology Center