USB: idmouse: simplify disconnect handling

Since commit d4ead16f50f9 ("USB: prevent char device open/deregister
race") core prevents further calls to open() after usb_deregister_dev()
returns so there's no need to use the interface data for
synchronisation.

This effectively reverts commit 54d2bc068fd2 ("USB: fix locking in
idmouse") with respect to the open-disconnect race.

Note that the driver already uses a present flag to suppress I/O post
disconnect (even if all USB I/O take place at open).

Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://lore.kernel.org/r/20191105103638.4929-2-johan@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/misc/idmouse.c b/drivers/usb/misc/idmouse.c
index 20b0f91..0386bac 100644 (file)
--- a/drivers/usb/misc/idmouse.c
+++ b/drivers/usb/misc/idmouse.c
@@ -60,7 +60,6 @@ static const struct usb_device_id idmouse_table[] = {
        USB_TYPE_VENDOR | USB_RECIP_ENDPOINT | USB_DIR_OUT, value, index, NULL, 0, 1000)
 
 MODULE_DEVICE_TABLE(usb, idmouse_table);
-static DEFINE_MUTEX(open_disc_mutex);
 
 /* structure to hold all of our device specific stuff */
 struct usb_idmouse {
@@ -227,17 +226,13 @@ static int idmouse_open(struct inode *inode, struct file *file)
        if (!interface)
                return -ENODEV;
 
-       mutex_lock(&open_disc_mutex);
        /* get the device information block from the interface */
        dev = usb_get_intfdata(interface);
-       if (!dev) {
-               mutex_unlock(&open_disc_mutex);
+       if (!dev)
                return -ENODEV;
-       }
 
        /* lock this device */
        mutex_lock(&dev->lock);
-       mutex_unlock(&open_disc_mutex);
 
        /* check if already open */
        if (dev->open) {
@@ -280,14 +275,12 @@ static int idmouse_release(struct inode *inode, struct file *file)
        if (dev == NULL)
                return -ENODEV;
 
-       mutex_lock(&open_disc_mutex);
        /* lock our device */
        mutex_lock(&dev->lock);
 
        /* are we really open? */
        if (dev->open <= 0) {
                mutex_unlock(&dev->lock);
-               mutex_unlock(&open_disc_mutex);
                return -ENODEV;
        }
 
@@ -296,11 +289,9 @@ static int idmouse_release(struct inode *inode, struct file *file)
        if (!dev->present) {
                /* the device was unplugged before the file was released */
                mutex_unlock(&dev->lock);
-               mutex_unlock(&open_disc_mutex);
                idmouse_delete(dev);
        } else {
                mutex_unlock(&dev->lock);
-               mutex_unlock(&open_disc_mutex);
        }
        return 0;
 }
@@ -379,7 +370,6 @@ static int idmouse_probe(struct usb_interface *interface,
        if (result) {
                /* something prevented us from registering this device */
                dev_err(&interface->dev, "Unable to allocate minor number.\n");
-               usb_set_intfdata(interface, NULL);
                idmouse_delete(dev);
                return result;
        }
@@ -392,19 +382,13 @@ static int idmouse_probe(struct usb_interface *interface,
 
 static void idmouse_disconnect(struct usb_interface *interface)
 {
-       struct usb_idmouse *dev;
-
-       /* get device structure */
-       dev = usb_get_intfdata(interface);
+       struct usb_idmouse *dev = usb_get_intfdata(interface);
 
        /* give back our minor */
        usb_deregister_dev(interface, &idmouse_class);
 
-       mutex_lock(&open_disc_mutex);
-       usb_set_intfdata(interface, NULL);
        /* lock the device */
        mutex_lock(&dev->lock);
-       mutex_unlock(&open_disc_mutex);
 
        /* prevent device read, write and ioctl */
        dev->present = 0;