On Thu, 9 Oct 2014, Andre Wolokita wrote:
> Issuing a modprobe -r g_serial command to the target
> over the gadget serial communications line causes
> modprobe to enter uninterruptable sleep, leaving the
> system in an unstable state.
>
> The associated tty_port.count won't drop to 0 because
> the command is issued over the very line being removed.
>
> Destroying the tty_port will ensure that resources are
> freed and modprobe will not hang.
You know, this last paragraph doesn't explain anything. The existing
code already calls tty_port_destroy; all you did was move that call
down a couple of lines. You need to explain why _moving_ the function
call is important, not why _calling_ the function is important.
Alan Stern
> --- a/drivers/usb/gadget/function/u_serial.c
> +++ b/drivers/usb/gadget/function/u_serial.c
> @@ -1074,10 +1074,10 @@ static int gs_closed(struct gs_port *port)
> static void gserial_free_port(struct gs_port *port)
> {
> tasklet_kill(&port->push);
> + tty_port_destroy(&port->port);
> /* wait for old opens to finish */
> wait_event(port->port.close_wait, gs_closed(port));
> WARN_ON(port->port_usb != NULL);
> - tty_port_destroy(&port->port);
> kfree(port);
> }
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