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[media] em28xx: fix race on disconnect 

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@yahoo.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Chris Rankin 2011-09-24 11:02:32 -03:00 committed by Mauro Carvalho Chehab
parent bd829e9d1d
commit d7222e7d6f
2 changed files with 8 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
drivers/media/video/em28xx/em28xx-cards.c
View File

@ -2800,9 +2800,9 @@ static void flush_request_modules(struct em28xx *dev)
#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 @@ void em28xx_release_resources(struct em28xx *dev)
em28xx_release_analog_resources(dev);
em28xx_remove_from_devlist(dev);
em28xx_i2c_unregister(dev);
v4l2_device_unregister(&dev->v4l2_dev);
@ -3255,7 +3253,7 @@ err_no_slot:
/*
* 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)

23
drivers/media/video/em28xx/em28xx-core.c
View File

@ -1183,18 +1183,6 @@ void em28xx_wake_i2c(struct em28xx *dev)
static LIST_HEAD(em28xx_devlist);
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_init_extension(struct em28xx *dev)
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);
}