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...

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