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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
d4ead16f50 ("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: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20190926091228.24634-8-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johan Hovold 2019-09-26 11:12:26 +02:00 committed by Greg Kroah-Hartman
parent eb7f5a490c
commit 61991d02fd
1 changed files with 1 additions and 17 deletions
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18
drivers/usb/misc/usblcd.c
View File

@ -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);