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tty: Fix close races in USB serial

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USB serial has always had races where the tty port usage count can hit zero
during a receive event. The internal locking is a mutex so we can't use
that in the IRQ handlers.

With krefs we can tackle this differently but we still need to be careful.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Alan Cox 2009-01-02 13:44:04 +00:00 committed by Linus Torvalds
parent 7e94b1d9bf
commit 4bd43f2c31
1 changed files with 10 additions and 5 deletions
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15
drivers/usb/serial/usb-serial.c
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@ -269,15 +269,19 @@ static void serial_close(struct tty_struct *tty, struct file *filp)
return;
}
--port->port.count;
if (port->port.count == 0)
if (port->port.count == 1)
/* only call the device specific close if this
* port is being closed by the last owner */
* port is being closed by the last owner. Ensure we do
* this before we drop the port count. The call is protected
* by the port mutex
*/
port->serial->type->close(tty, port, filp);
if (port->port.count == (port->console? 1 : 0)) {
if (port->port.count == (port->console ? 2 : 1)) {
struct tty_struct *tty = tty_port_tty_get(&port->port);
if (tty) {
/* We must do this before we drop the port count to
zero. */
if (tty->driver_data)
tty->driver_data = NULL;
tty_port_tty_set(&port->port, NULL);
@ -285,13 +289,14 @@ static void serial_close(struct tty_struct *tty, struct file *filp)
}
}
if (port->port.count == 0) {
if (port->port.count == 1) {
mutex_lock(&port->serial->disc_mutex);
if (!port->serial->disconnected)
usb_autopm_put_interface(port->serial->interface);
mutex_unlock(&port->serial->disc_mutex);
module_put(port->serial->type->driver.owner);
}
--port->port.count;
mutex_unlock(&port->mutex);
usb_serial_put(port->serial);