The uvcvideo driver has a driver-wide lock and a reference count to protect
against a disconnect/open race. Now that videodev handles the race itself,
reference-counting in the driver can be removed.
This is a backport from the v4l-dvb tree.
Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
--- a/linux/drivers/media/video/uvc/uvc_driver.c Wed Sep 02 08:12:26 2009 +0200
+++ b/linux/drivers/media/video/uvc/uvc_driver.c Wed Sep 30 02:07:19 2009 +0200
@@ -1531,22 +1531,92 @@
*/
/*
+ * Delete the UVC device.
+ *
+ * Called by the kernel when the last reference to the uvc_device structure
+ * is released.
+ *
+ * As this function is called after or during disconnect(), all URBs have
+ * already been canceled by the USB core. There is no need to kill the
+ * interrupt URB manually.
+ */
+static void uvc_delete(struct uvc_device *dev)
+{
+ struct list_head *p, *n;
+
+ usb_put_intf(dev->intf);
+ usb_put_dev(dev->udev);
+
+ uvc_status_cleanup(dev);
+ uvc_ctrl_cleanup_device(dev);
+
+ list_for_each_safe(p, n, &dev->chains) {
+ struct uvc_video_chain *chain;
+ chain = list_entry(p, struct uvc_video_chain, list);
+ kfree(chain);
+ }
+
+ list_for_each_safe(p, n, &dev->entities) {
+ struct uvc_entity *entity;
+ entity = list_entry(p, struct uvc_entity, list);
+ kfree(entity);
+ }
+
+ list_for_each_safe(p, n, &dev->streams) {
+ struct uvc_streaming *streaming;
+ streaming = list_entry(p, struct uvc_streaming, list);
+ usb_driver_release_interface(&uvc_driver.driver,
+ streaming->intf);
+ usb_put_intf(streaming->intf);
+ kfree(streaming->format);
+ kfree(streaming->header.bmaControls);
+ kfree(streaming);
+ }
+
+ kfree(dev);
+}
+
+static void uvc_release(struct video_device *vdev)
+{
+ struct uvc_streaming *stream = video_get_drvdata(vdev);
+ struct uvc_device *dev = stream->dev;
+
+ video_device_release(vdev);
+
+ /* Decrement the registered streams count and delete the device when it
+ * reaches zero.
+ */
+ if (atomic_dec_and_test(&dev->nstreams))
+ uvc_delete(dev);
+}
+
+/*
* Unregister the video devices.
*/
static void uvc_unregister_video(struct uvc_device *dev)
{
struct uvc_streaming *stream;
+ /* Unregistering all video devices might result in uvc_delete() being
+ * called from inside the loop if there's no open file handle. To avoid
+ * that, increment the stream count before iterating over the streams
+ * and decrement it when done.
+ */
+ atomic_inc(&dev->nstreams);
+
list_for_each_entry(stream, &dev->streams, list) {
if (stream->vdev == NULL)
continue;
- if (stream->vdev->minor == -1)
- video_device_release(stream->vdev);
- else
- video_unregister_device(stream->vdev);
+ video_unregister_device(stream->vdev);
stream->vdev = NULL;
}
+
+ /* Decrement the stream count and call uvc_delete explicitly if there
+ * are no stream left.
+ */
+ if (atomic_dec_and_test(&dev->nstreams))
+ uvc_delete(dev);
}
static int uvc_register_video(struct uvc_device *dev,
@@ -1580,7 +1650,7 @@
vdev->parent = &dev->intf->dev;
vdev->minor = -1;
vdev->fops = &uvc_fops;
- vdev->release = video_device_release;
+ vdev->release = uvc_release;
strlcpy(vdev->name, dev->name, sizeof vdev->name);
/* Set the driver data before calling video_register_device, otherwise
@@ -1598,6 +1668,7 @@
return ret;
}
+ atomic_inc(&dev->nstreams);
return 0;
}
@@ -1653,61 +1724,6 @@
* USB probe, disconnect, suspend and resume
*/
-/*
- * Delete the UVC device.
- *
- * Called by the kernel when the last reference to the uvc_device structure
- * is released.
- *
- * Unregistering the video devices is done here because every opened instance
- * must be closed before the device can be unregistered. An alternative would
- * have been to use another reference count for uvc_v4l2_open/uvc_release, and
- * unregister the video devices on disconnect when that reference count drops
- * to zero.
- *
- * As this function is called after or during disconnect(), all URBs have
- * already been canceled by the USB core. There is no need to kill the
- * interrupt URB manually.
- */
-void uvc_delete(struct kref *kref)
-{
- struct uvc_device *dev = container_of(kref, struct uvc_device, kref);
- struct list_head *p, *n;
-
- /* Unregister the video devices. */
- uvc_unregister_video(dev);
- usb_put_intf(dev->intf);
- usb_put_dev(dev->udev);
-
- uvc_status_cleanup(dev);
- uvc_ctrl_cleanup_device(dev);
-
- list_for_each_safe(p, n, &dev->chains) {
- struct uvc_video_chain *chain;
- chain = list_entry(p, struct uvc_video_chain, list);
- kfree(chain);
- }
-
- list_for_each_safe(p, n, &dev->entities) {
- struct uvc_entity *entity;
- entity = list_entry(p, struct uvc_entity, list);
- kfree(entity);
- }
-
- list_for_each_safe(p, n, &dev->streams) {
- struct uvc_streaming *streaming;
- streaming = list_entry(p, struct uvc_streaming, list);
- usb_driver_release_interface(&uvc_driver.driver,
- streaming->intf);
- usb_put_intf(streaming->intf);
- kfree(streaming->format);
- kfree(streaming->header.bmaControls);
- kfree(streaming);
- }
-
- kfree(dev);
-}
-
static int uvc_probe(struct usb_interface *intf,
const struct usb_device_id *id)
{
@@ -1730,7 +1746,7 @@
INIT_LIST_HEAD(&dev->entities);
INIT_LIST_HEAD(&dev->chains);
INIT_LIST_HEAD(&dev->streams);
- kref_init(&dev->kref);
+ atomic_set(&dev->nstreams, 0);
atomic_set(&dev->users, 0);
dev->udev = usb_get_dev(udev);
@@ -1792,7 +1808,7 @@
return 0;
error:
- kref_put(&dev->kref, uvc_delete);
+ uvc_unregister_video(dev);
return -ENODEV;
}
@@ -1809,21 +1825,9 @@
UVC_SC_VIDEOSTREAMING)
return;
- /* uvc_v4l2_open() might race uvc_disconnect(). A static driver-wide
- * lock is needed to prevent uvc_disconnect from releasing its
- * reference to the uvc_device instance after uvc_v4l2_open() received
- * the pointer to the device (video_devdata) but before it got the
- * chance to increase the reference count (kref_get).
- *
- * Note that the reference can't be released with the lock held,
- * otherwise a AB-BA deadlock can occur with videodev_lock that
- * videodev acquires in videodev_open() and video_unregister_device().
- */
- mutex_lock(&uvc_driver.open_mutex);
dev->state |= UVC_DEV_DISCONNECTED;
- mutex_unlock(&uvc_driver.open_mutex);
- kref_put(&dev->kref, uvc_delete);
+ uvc_unregister_video(dev);
}
static int uvc_suspend(struct usb_interface *intf, pm_message_t message)
@@ -2165,7 +2169,6 @@
INIT_LIST_HEAD(&uvc_driver.devices);
INIT_LIST_HEAD(&uvc_driver.controls);
- mutex_init(&uvc_driver.open_mutex);
mutex_init(&uvc_driver.ctrl_mutex);
uvc_ctrl_init();
--- a/linux/drivers/media/video/uvc/uvc_v4l2.c Wed Sep 02 08:12:26 2009 +0200
+++ b/linux/drivers/media/video/uvc/uvc_v4l2.c Wed Sep 30 02:07:19 2009 +0200
@@ -376,25 +376,18 @@
*/
static int uvc_acquire_privileges(struct uvc_fh *handle)
{
- int ret = 0;
-
/* Always succeed if the handle is already privileged. */
if (handle->state == UVC_HANDLE_ACTIVE)
return 0;
/* Check if the device already has a privileged handle. */
- mutex_lock(&uvc_driver.open_mutex);
if (atomic_inc_return(&handle->stream->active) != 1) {
atomic_dec(&handle->stream->active);
- ret = -EBUSY;
- goto done;
+ return -EBUSY;
}
handle->state = UVC_HANDLE_ACTIVE;
-
-done:
- mutex_unlock(&uvc_driver.open_mutex);
- return ret;
+ return 0;
}
static void uvc_dismiss_privileges(struct uvc_fh *handle)
@@ -421,18 +414,15 @@
int ret = 0;
uvc_trace(UVC_TRACE_CALLS, "uvc_v4l2_open\n");
- mutex_lock(&uvc_driver.open_mutex);
stream = video_drvdata(file);
- if (stream->dev->state & UVC_DEV_DISCONNECTED) {
- ret = -ENODEV;
- goto done;
- }
+ if (stream->dev->state & UVC_DEV_DISCONNECTED)
+ return -ENODEV;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 19)
ret = usb_autopm_get_interface(stream->dev->intf);
if (ret < 0)
- goto done;
+ return ret;
#endif
/* Create the device handle. */
@@ -441,8 +431,7 @@
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 19)
usb_autopm_put_interface(stream->dev->intf);
#endif
- ret = -ENOMEM;
- goto done;
+ return -ENOMEM;
}
if (atomic_inc_return(&stream->dev->users) == 1) {
@@ -453,7 +442,7 @@
#endif
atomic_dec(&stream->dev->users);
kfree(handle);
- goto done;
+ return ret;
}
}
@@ -462,11 +451,7 @@
handle->state = UVC_HANDLE_PASSIVE;
file->private_data = handle;
- kref_get(&stream->dev->kref);
-
-done:
- mutex_unlock(&uvc_driver.open_mutex);
- return ret;
+ return 0;
}
static int uvc_v4l2_release(struct file *file)
@@ -498,7 +483,6 @@
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 19)
usb_autopm_put_interface(stream->dev->intf);
#endif
- kref_put(&stream->dev->kref, uvc_delete);
return 0;
}
--- a/linux/drivers/media/video/uvc/uvcvideo.h Wed Sep 02 08:12:26 2009 +0200
+++ b/linux/drivers/media/video/uvc/uvcvideo.h Wed Sep 30 02:07:19 2009 +0200
@@ -476,7 +476,6 @@
char name[32];
enum uvc_device_state state;
- struct kref kref;
struct list_head list;
atomic_t users;
@@ -489,6 +488,7 @@
/* Video Streaming interfaces */
struct list_head streams;
+ atomic_t nstreams;
/* Status Interrupt Endpoint */
struct usb_host_endpoint *int_ep;
@@ -512,8 +512,6 @@
struct uvc_driver {
struct usb_driver driver;
- struct mutex open_mutex; /* protects from open/disconnect race */
-
struct list_head devices; /* struct uvc_device list */
struct list_head controls; /* struct uvc_control_info list */
struct mutex ctrl_mutex; /* protects controls and devices
@@ -572,7 +570,6 @@
/* Core driver */
extern struct uvc_driver uvc_driver;
-extern void uvc_delete(struct kref *kref);
/* Video buffers queue management. */
extern void uvc_queue_init(struct uvc_video_queue *queue,
--
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