Commit 61991d02 authored by Johan Hovold's avatar Johan Hovold Committed by Greg Kroah-Hartman
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USB: usblcd: drop redundant disconnect mutex 



Drop the redundant disconnect mutex which was introduced after the
open-disconnect race had been addressed generally in USB core by commit
d4ead16f ("USB: prevent char device open/deregister race").

Specifically, the rw-semaphore in core guarantees that all calls to
open() will have completed and that no new calls to open() will occur
after usb_deregister_dev() returns. Hence there is no need use the
driver data as an inverted disconnected flag.

Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20190926091228.24634-8-johan@kernel.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent eb7f5a49

drivers/usb/misc/usblcd.c

+1 −17
Original line number Diff line number Diff line
@@ -37,9 +37,6 @@ static const struct usb_device_id id_table[] = { 
};

MODULE_DEVICE_TABLE(usb, id_table);



static DEFINE_MUTEX(open_disc_mutex);





struct usb_lcd {

	struct usb_device	*udev;			/* init: probe_lcd */

	struct usb_interface	*interface;		/* the interface for
@@ -95,17 +92,10 @@ static int lcd_open(struct inode *inode, struct file *file) 
		return -ENODEV;

	}



	mutex_lock(&open_disc_mutex);

	dev = usb_get_intfdata(interface);

	if (!dev) {

		mutex_unlock(&open_disc_mutex);

		mutex_unlock(&lcd_mutex);

		return -ENODEV;

	}



	/* increment our usage count for the device */

	kref_get(&dev->kref);

	mutex_unlock(&open_disc_mutex);



	/* grab a power reference */

	r = usb_autopm_get_interface(interface);
@@ -388,7 +378,6 @@ static int lcd_probe(struct usb_interface *interface, 
		/* something prevented us from registering this driver */

		dev_err(&interface->dev,

			"Not able to get a minor for this device.\n");

		usb_set_intfdata(interface, NULL);

		goto error;

	}
@@ -434,14 +423,9 @@ static int lcd_resume(struct usb_interface *intf) 


static void lcd_disconnect(struct usb_interface *interface)

{

	struct usb_lcd *dev;

	struct usb_lcd *dev = usb_get_intfdata(interface);

	int minor = interface->minor;



	mutex_lock(&open_disc_mutex);

	dev = usb_get_intfdata(interface);

	usb_set_intfdata(interface, NULL);

	mutex_unlock(&open_disc_mutex);



	/* give back our minor */

	usb_deregister_dev(interface, &lcd_class);

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