Re: your mail

Al Viro
2012-02-12T19:11:37Z

On Sun, Feb 12, 2012 at 01:21:10AM +0100, Richard Weinberger wrote:

> @@ -343,7 +267,7 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
> {
> struct chan *chan = data;
> struct line *line = chan->line;
> - struct tty_struct *tty = line->tty;
> + struct tty_struct *tty = tty_port_tty_get(&line->port);
> int err;
>
> /*
> @@ -354,6 +278,9 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
> spin_lock(&line->lock);
> err = flush_buffer(line);
> if (err == 0) {
> + tty_kref_put(tty);
> +
> + spin_unlock(&line->lock);
> return IRQ_NONE;
> } else if (err < 0) {
> line->head = line->buffer;
> @@ -365,9 +292,12 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
> return IRQ_NONE;
>
> tty_wakeup(tty);
> + tty_kref_put(tty);
> return IRQ_HANDLED;
> }

That, BTW, smells ugly. Note that return before the last one has no
tty_kref_put() for a very good reason - it's under if (!tty). And
just as line->tty, port->tty can become NULL, so tty_port_tty_get()
can, indeed, return NULL here. Which makes the first tty_kref_put()
oopsable...