Jiri,

Thanks a lot for fixing this!

I have two questions:
1. Are these patches also usable on 3.4 and 3.3 or do they depend on 3.5's TTY changes?
2. Why didn't you use tty_port_open()/close()/etc. as Alan suggested my in [1]?

Thanks,
//richard

[1] http://lkml.indiana.edu/hypermail/linux/kernel/1201.3/01705.html

Am 04.06.2012 13:35, schrieb Jiri Slaby:
> This means switching to the tty refcounted model so that we will not
> race with interrupts.
> 
> Signed-off-by: Jiri Slaby <jslaby@suse.cz>
> Cc: Jeff Dike <jdike@addtoit.com>
> Cc: Richard Weinberger <richard@nod.at>
> Cc: user-mode-linux-devel@lists.sourceforge.net
> ---
>  arch/um/drivers/chan_kern.c |    4 +++-
>  arch/um/drivers/line.c      |   25 ++++++++++++++++++-------
>  arch/um/drivers/line.h      |    1 -
>  3 files changed, 21 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
> index 45e248c..87eebfe 100644
> --- a/arch/um/drivers/chan_kern.c
> +++ b/arch/um/drivers/chan_kern.c
> @@ -150,9 +150,11 @@ void chan_enable_winch(struct chan *chan, struct tty_struct *tty)
>  static void line_timer_cb(struct work_struct *work)
>  {
>  	struct line *line = container_of(work, struct line, task.work);
> +	struct tty_struct *tty = tty_port_tty_get(&line->port);
>  
>  	if (!line->throttled)
> -		chan_interrupt(line, line->tty, line->driver->read_irq);
> +		chan_interrupt(line, tty, line->driver->read_irq);
> +	tty_kref_put(tty);
>  }
>  
>  int enable_chan(struct line *line)
> diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
> index 482a7bd..fb6e4ea 100644
> --- a/arch/um/drivers/line.c
> +++ b/arch/um/drivers/line.c
> @@ -19,9 +19,11 @@ static irqreturn_t line_interrupt(int irq, void *data)
>  {
>  	struct chan *chan = data;
>  	struct line *line = chan->line;
> +	struct tty_struct *tty = tty_port_tty_get(&line->port);
>  
>  	if (line)
> -		chan_interrupt(line, line->tty, irq);
> +		chan_interrupt(line, tty, irq);
> +	tty_kref_put(tty);
>  	return IRQ_HANDLED;
>  }
>  
> @@ -333,7 +335,7 @@ 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;
>  	int err;
>  
>  	/*
> @@ -352,10 +354,13 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
>  	}
>  	spin_unlock(&line->lock);
>  
> +	tty = tty_port_tty_get(&line->port);
>  	if (tty == NULL)
>  		return IRQ_NONE;
>  
>  	tty_wakeup(tty);
> +	tty_kref_put(tty);
> +
>  	return IRQ_HANDLED;
>  }
>  
> @@ -409,7 +414,7 @@ int line_open(struct line *lines, struct tty_struct *tty)
>  
>  	BUG_ON(tty->driver_data);
>  	tty->driver_data = line;
> -	line->tty = tty;
> +	tty_port_tty_set(&line->port, tty);
>  
>  	err = enable_chan(line);
>  	if (err) /* line_close() will be called by our caller */
> @@ -449,7 +454,7 @@ void line_close(struct tty_struct *tty, struct file * filp)
>  	if (--line->port.count)
>  		goto out_unlock;
>  
> -	line->tty = NULL;
> +	tty_port_tty_set(&line->port, NULL);
>  	tty->driver_data = NULL;
>  
>  	if (line->sigio) {
> @@ -610,9 +615,15 @@ int line_get_config(char *name, struct line *lines, unsigned int num, char *str,
>  	mutex_lock(&line->count_lock);
>  	if (!line->valid)
>  		CONFIG_CHUNK(str, size, n, "none", 1);
> -	else if (line->tty == NULL)
> -		CONFIG_CHUNK(str, size, n, line->init_str, 1);
> -	else n = chan_config_string(line, str, size, error_out);
> +	else {
> +		struct tty_struct *tty = tty_port_tty_get(&line->port);
> +		if (tty == NULL) {
> +			CONFIG_CHUNK(str, size, n, line->init_str, 1);
> +		} else {
> +			n = chan_config_string(line, str, size, error_out);
> +			tty_kref_put(tty);
> +		}
> +	}
>  	mutex_unlock(&line->count_lock);
>  
>  	return n;
> diff --git a/arch/um/drivers/line.h b/arch/um/drivers/line.h
> index 0e06a1f..5b3d4fb 100644
> --- a/arch/um/drivers/line.h
> +++ b/arch/um/drivers/line.h
> @@ -33,7 +33,6 @@ struct line_driver {
>  
>  struct line {
>  	struct tty_port port;
> -	struct tty_struct *tty;
>  	struct mutex count_lock;
>  	int valid;
>