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USB: serial: fix potential runtime pm imbalance at device remove 

Only call usb_autopm_put_interface() if the corresponding
usb_autopm_get_interface() was successful.

This prevents a potential runtime PM counter imbalance should
usb_autopm_get_interface() fail. Note that the USB PM usage counter is
reset when the interface is unbound, but that the runtime PM counter may
be left unbalanced.

Also add comment on why we don't need to worry about racing
resume/suspend on autopm_get failures.

Fixes: d5fd650cfc ("usb: serial: prevent suspend/resume from racing
against probe/remove")

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2014-05-26 19:23:33 +02:00 committed by Greg Kroah-Hartman
parent b0a9aa6da8
commit c14829fad8
1 changed files with 11 additions and 3 deletions
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14
drivers/usb/serial/bus.c
View File

@ -97,13 +97,19 @@ static int usb_serial_device_remove(struct device *dev)
struct usb_serial_port *port;
int retval = 0;
int minor;
int autopm_err;
port = to_usb_serial_port(dev);
if (!port)
return -ENODEV;
/* make sure suspend/resume doesn't race against port_remove */
usb_autopm_get_interface(port->serial->interface);
/*
* Make sure suspend/resume doesn't race against port_remove.
*
* Note that no further runtime PM callbacks will be made if
* autopm_get fails.
*/
autopm_err = usb_autopm_get_interface(port->serial->interface);
minor = port->minor;
tty_unregister_device(usb_serial_tty_driver, minor);
@ -117,7 +123,9 @@ static int usb_serial_device_remove(struct device *dev)
dev_info(dev, "%s converter now disconnected from ttyUSB%d\n",
driver->description, minor);
usb_autopm_put_interface(port->serial->interface);
if (!autopm_err)
usb_autopm_put_interface(port->serial->interface);
return retval;
}