Re: kernel BUG and freeze on cat /proc/tty/driver/serial

[Alan Cox]

> -       struct tty_ldisc *ld = tty_ldisc_ref(port->tty);
> +       struct tty_ldisc *ld = port ? tty_ldisc_ref(port->tty) : NULL;
>         struct pps_event_time ts;
> 
>         if (ld && ld->ops->dcd_change)
> @@ -2465,7 +2465,7 @@ void uart_handle_dcd_change(struct uart_port
> *uport, unsigned int status)
>                 hardpps();
>  #endif
> 
> -       if (port->flags & ASYNC_CHECK_CD) {
> +       if (port && port->flags & ASYNC_CHECK_CD) {
>                 if (status)
>                         wake_up_interruptible(&port->open_wait);
>                 else if (port->tty)

Probably should be using tty krefs for this

	tty = tty_port_tty_get( ..) /  tty_kref_put

etc, and yes the NULL check is needed. The reference is needed so the tty
can't be freed under you.



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