This patch closes the race on the device and extension lists at USB disconnect
time. Previously, the device was removed from the device list during
em28xx_release_resources(), and then passed to the em28xx_close_extension()
function so that all extensions could run their fini() operations. However, this
left a (brief, theoretical, highly unlikely ;-)) window between these two calls
during which a new module could call em28xx_register_extension(). The result
would have been that the em28xx_usb_disconnect() function would also have passed
the device to the new extension's fini() function, despite never having called
the extension's init() function.
This patch also restores em28xx_close_extension()'s symmetry with
em28xx_init_extension(), and establishes the property that every device in the
device list must have been initialised for every extension in the extension list.
Signed-off-by: Chris Rankin <rankincj@xxxxxxxxx>
--- linux/drivers/media/video/em28xx/em28xx-core.c.orig 2011-09-24 14:56:05.000000000 +0100
+++ linux/drivers/media/video/em28xx/em28xx-core.c 2011-09-24 15:01:23.000000000 +0100
@@ -1184,18 +1184,6 @@
static DEFINE_MUTEX(em28xx_devlist_mutex);
/*
- * em28xx_realease_resources()
- * unregisters the v4l2,i2c and usb devices
- * called when the device gets disconected or at module unload
-*/
-void em28xx_remove_from_devlist(struct em28xx *dev)
-{
- mutex_lock(&em28xx_devlist_mutex);
- list_del(&dev->devlist);
- mutex_unlock(&em28xx_devlist_mutex);
-};
-
-/*
* Extension interface
*/
@@ -1245,14 +1233,13 @@
void em28xx_close_extension(struct em28xx *dev)
{
- struct em28xx_ops *ops = NULL;
+ const struct em28xx_ops *ops = NULL;
mutex_lock(&em28xx_devlist_mutex);
- if (!list_empty(&em28xx_extension_devlist)) {
- list_for_each_entry(ops, &em28xx_extension_devlist, next) {
- if (ops->fini)
- ops->fini(dev);
- }
+ list_for_each_entry(ops, &em28xx_extension_devlist, next) {
+ if (ops->fini)
+ ops->fini(dev);
}
+ list_del(&dev->devlist);
mutex_unlock(&em28xx_devlist_mutex);
}
--- linux/drivers/media/video/em28xx/em28xx-cards.c.orig 2011-09-24 15:19:28.000000000 +0100
+++ linux/drivers/media/video/em28xx/em28xx-cards.c 2011-09-24 15:19:33.000000000 +0100
@@ -2800,9 +2800,9 @@
#endif /* CONFIG_MODULES */
/*
- * em28xx_realease_resources()
+ * em28xx_release_resources()
* unregisters the v4l2,i2c and usb devices
- * called when the device gets disconected or at module unload
+ * called when the device gets disconnected or at module unload
*/
void em28xx_release_resources(struct em28xx *dev)
{
@@ -2816,8 +2816,6 @@
em28xx_release_analog_resources(dev);
- em28xx_remove_from_devlist(dev);
-
em28xx_i2c_unregister(dev);
v4l2_device_unregister(&dev->v4l2_dev);
@@ -3255,7 +3253,7 @@
/*
* em28xx_usb_disconnect()
- * called when the device gets diconencted
+ * called when the device gets disconnected
* video device will be unregistered on v4l2_close in case it is still open
*/
static void em28xx_usb_disconnect(struct usb_interface *interface)
