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    Subject[PATCH 39/79] tty: USB can now use the shutdown method for kref based freeing of ports
    Date
    From: Alan Cox <alan@linux.intel.com>

    Signed-off-by: Alan Cox <alan@linux.intel.com>
    Cc: stable <stable@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
    ---
    drivers/usb/serial/usb-serial.c | 28 +++++++---------------------
    1 files changed, 7 insertions(+), 21 deletions(-)

    diff --git a/drivers/usb/serial/usb-serial.c b/drivers/usb/serial/usb-serial.c
    index 21dd72a..31c7a09 100644
    --- a/drivers/usb/serial/usb-serial.c
    +++ b/drivers/usb/serial/usb-serial.c
    @@ -316,16 +316,19 @@ static void serial_do_down(struct usb_serial_port *port)
    *
    * Do the resource freeing and refcount dropping for the port. We must
    * be careful about ordering and we must avoid freeing up the console.
    + *
    + * Called when the last tty kref is dropped.
    */

    -static void serial_do_free(struct usb_serial_port *port)
    +static void serial_do_free(struct tty_struct *tty)
    {
    + struct usb_serial_port *port = tty->driver_data;
    struct usb_serial *serial;
    struct module *owner;

    /* The console is magical, do not hang up the console hardware
    or there will be tears */
    - if (port->console)
    + if (port == NULL || port->console)
    return;

    serial = port->serial;
    @@ -350,30 +353,12 @@ static void serial_close(struct tty_struct *tty, struct file *filp)

    dbg("%s - port %d", __func__, port->number);

    - /* FIXME:
    - This leaves a very narrow race. Really we should do the
    - serial_do_free() on tty->shutdown(), but tty->shutdown can
    - be called from IRQ context and serial_do_free can sleep.
    -
    - The right fix is probably to make the tty free (which is rare)
    - and thus tty->shutdown() occur via a work queue and simplify all
    - the drivers that use it.
    - */
    - if (tty_hung_up_p(filp)) {
    - /* serial_hangup already called serial_down at this point.
    - Another user may have already reopened the port but
    - serial_do_free is refcounted */
    - serial_do_free(port);
    - return;
    - }
    -
    if (tty_port_close_start(&port->port, tty, filp) == 0)
    return;
    -
    serial_do_down(port);
    tty_port_close_end(&port->port, tty);
    tty_port_tty_set(&port->port, NULL);
    - serial_do_free(port);
    +
    }

    static void serial_hangup(struct tty_struct *tty)
    @@ -1243,6 +1228,7 @@ static const struct tty_operations serial_ops = {
    .chars_in_buffer = serial_chars_in_buffer,
    .tiocmget = serial_tiocmget,
    .tiocmset = serial_tiocmset,
    + .shutdown = serial_do_free,
    .proc_fops = &serial_proc_fops,
    };

    --
    1.6.4.2


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