[media] gspca: Switch to V4L2 core locking, except for the buffer queuing ioctls

Due to latency concerns the VIDIOC_QBUF, DQBUF and QUERYBUF do not use the
core lock, instead they rely only on queue_lock.

Changes by HdG:
1) Change release from the video_device to the v4l2_device, to avoid a
race on disconnect.
2) Adjust for the V4L2 core changes which cause non ioctl fops to no longer
take the V4L2 core lock.

[mchehab@redhat.com: fix a merge conflict]
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/gspca/gspca.c

@@ -850,14 +850,6 @@ static int gspca_init_transfer(struct gspca_dev *gspca_dev)
 	struct ep_tb_s ep_tb[MAX_ALT];
 	int n, ret, xfer, alt, alt_idx;
 
-	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-		return -ERESTARTSYS;
-
-	if (!gspca_dev->present) {
-		ret = -ENODEV;
-		goto unlock;
-	}
-
 	/* reset the streaming variables */
 	gspca_dev->image = NULL;
 	gspca_dev->image_len = 0;
@@ -872,7 +864,7 @@ static int gspca_init_transfer(struct gspca_dev *gspca_dev)
 	if (gspca_dev->sd_desc->isoc_init) {
 		ret = gspca_dev->sd_desc->isoc_init(gspca_dev);
 		if (ret < 0)
-			goto unlock;
+			return ret;
 	}
 	xfer = gspca_dev->cam.bulk ? USB_ENDPOINT_XFER_BULK
 				   : USB_ENDPOINT_XFER_ISOC;
@@ -883,8 +875,7 @@ static int gspca_init_transfer(struct gspca_dev *gspca_dev)
 		ep = alt_xfer(&intf->altsetting[gspca_dev->alt], xfer);
 		if (ep == NULL) {
 			pr_err("bad altsetting %d\n", gspca_dev->alt);
-			ret = -EIO;
-			goto out;
+			return -EIO;
 		}
 		ep_tb[0].alt = gspca_dev->alt;
 		alt_idx = 1;
@@ -895,8 +886,7 @@ static int gspca_init_transfer(struct gspca_dev *gspca_dev)
 		alt_idx = build_isoc_ep_tb(gspca_dev, intf, ep_tb);
 		if (alt_idx <= 0) {
 			pr_err("no transfer endpoint found\n");
-			ret = -EIO;
-			goto unlock;
+			return -EIO;
 		}
 	}
 
@@ -991,8 +981,6 @@ static int gspca_init_transfer(struct gspca_dev *gspca_dev)
 	}
 out:
 	gspca_input_create_urb(gspca_dev);
-unlock:
-	mutex_unlock(&gspca_dev->usb_lock);
 	return ret;
 }
 
@@ -1062,7 +1050,6 @@ static int gspca_get_mode(struct gspca_dev *gspca_dev,
 static int vidioc_g_register(struct file *file, void *priv,
 			struct v4l2_dbg_register *reg)
 {
-	int ret;
 	struct gspca_dev *gspca_dev = video_drvdata(file);
 
 	if (!gspca_dev->sd_desc->get_chip_ident)
@@ -1071,22 +1058,13 @@ static int vidioc_g_register(struct file *file, void *priv,
 	if (!gspca_dev->sd_desc->get_register)
 		return -ENOTTY;
 
-	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-		return -ERESTARTSYS;
 	gspca_dev->usb_err = 0;
-	if (gspca_dev->present)
-		ret = gspca_dev->sd_desc->get_register(gspca_dev, reg);
-	else
-		ret = -ENODEV;
-	mutex_unlock(&gspca_dev->usb_lock);
-
-	return ret;
+	return gspca_dev->sd_desc->get_register(gspca_dev, reg);
 }
 
 static int vidioc_s_register(struct file *file, void *priv,
 			struct v4l2_dbg_register *reg)
 {
-	int ret;
 	struct gspca_dev *gspca_dev = video_drvdata(file);
 
 	if (!gspca_dev->sd_desc->get_chip_ident)
@@ -1095,38 +1073,21 @@ static int vidioc_s_register(struct file *file, void *priv,
 	if (!gspca_dev->sd_desc->set_register)
 		return -ENOTTY;
 
-	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-		return -ERESTARTSYS;
 	gspca_dev->usb_err = 0;
-	if (gspca_dev->present)
-		ret = gspca_dev->sd_desc->set_register(gspca_dev, reg);
-	else
-		ret = -ENODEV;
-	mutex_unlock(&gspca_dev->usb_lock);
-
-	return ret;
+	return gspca_dev->sd_desc->set_register(gspca_dev, reg);
 }
 #endif
 
 static int vidioc_g_chip_ident(struct file *file, void *priv,
 			struct v4l2_dbg_chip_ident *chip)
 {
-	int ret;
 	struct gspca_dev *gspca_dev = video_drvdata(file);
 
 	if (!gspca_dev->sd_desc->get_chip_ident)
 		return -ENOTTY;
 
-	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-		return -ERESTARTSYS;
 	gspca_dev->usb_err = 0;
-	if (gspca_dev->present)
-		ret = gspca_dev->sd_desc->get_chip_ident(gspca_dev, chip);
-	else
-		ret = -ENODEV;
-	mutex_unlock(&gspca_dev->usb_lock);
-
-	return ret;
+	return gspca_dev->sd_desc->get_chip_ident(gspca_dev, chip);
 }
 
 static int vidioc_enum_fmt_vid_cap(struct file *file, void  *priv,
@@ -1321,9 +1282,10 @@ static int vidioc_enum_frameintervals(struct file *filp, void *priv,
 	return -EINVAL;
 }
 
-static void gspca_release(struct video_device *vfd)
+static void gspca_release(struct v4l2_device *v4l2_device)
 {
-	struct gspca_dev *gspca_dev = container_of(vfd, struct gspca_dev, vdev);
+	struct gspca_dev *gspca_dev =
+		container_of(v4l2_device, struct gspca_dev, v4l2_dev);
 
 	PDEBUG(D_PROBE, "%s released",
 		video_device_node_name(&gspca_dev->vdev));
@@ -1339,8 +1301,6 @@ static int dev_open(struct file *file)
 	struct gspca_dev *gspca_dev = video_drvdata(file);
 
 	PDEBUG(D_STREAM, "[%s] open", current->comm);
-	if (!gspca_dev->present)
-		return -ENODEV;
 
 	/* protect the subdriver against rmmod */
 	if (!try_module_get(gspca_dev->module))
@@ -1363,21 +1323,27 @@ static int dev_close(struct file *file)
 	struct gspca_dev *gspca_dev = video_drvdata(file);
 
 	PDEBUG(D_STREAM, "[%s] close", current->comm);
-	if (mutex_lock_interruptible(&gspca_dev->queue_lock))
+
+	/* Needed for gspca_stream_off, always lock before queue_lock! */
+	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
 		return -ERESTARTSYS;
 
+	if (mutex_lock_interruptible(&gspca_dev->queue_lock)) {
+		mutex_unlock(&gspca_dev->usb_lock);
+		return -ERESTARTSYS;
+	}
+
 	/* if the file did the capture, free the streaming resources */
 	if (gspca_dev->capt_file == file) {
 		if (gspca_dev->streaming) {
-			mutex_lock(&gspca_dev->usb_lock);
 			gspca_dev->usb_err = 0;
 			gspca_stream_off(gspca_dev);
-			mutex_unlock(&gspca_dev->usb_lock);
 		}
 		frame_free(gspca_dev);
 	}
 	module_put(gspca_dev->module);
 	mutex_unlock(&gspca_dev->queue_lock);
+	mutex_unlock(&gspca_dev->usb_lock);
 
 	PDEBUG(D_STREAM, "close done");
 
@@ -1388,15 +1354,7 @@ static int vidioc_querycap(struct file *file, void  *priv,
 			   struct v4l2_capability *cap)
 {
 	struct gspca_dev *gspca_dev = video_drvdata(file);
-	int ret;
 
-	/* protect the access to the usb device */
-	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-		return -ERESTARTSYS;
-	if (!gspca_dev->present) {
-		ret = -ENODEV;
-		goto out;
-	}
 	strlcpy((char *) cap->driver, gspca_dev->sd_desc->name,
 			sizeof cap->driver);
 	if (gspca_dev->dev->product != NULL) {
@@ -1414,10 +1372,7 @@ static int vidioc_querycap(struct file *file, void  *priv,
 			  | V4L2_CAP_STREAMING
 			  | V4L2_CAP_READWRITE;
 	cap->capabilities = cap->device_caps | V4L2_CAP_DEVICE_CAPS;
-	ret = 0;
-out:
-	mutex_unlock(&gspca_dev->usb_lock);
-	return ret;
+	return 0;
 }
 
 static int get_ctrl(struct gspca_dev *gspca_dev,
@@ -1486,7 +1441,7 @@ static int vidioc_s_ctrl(struct file *file, void *priv,
 	struct gspca_dev *gspca_dev = video_drvdata(file);
 	const struct ctrl *ctrls;
 	struct gspca_ctrl *gspca_ctrl;
-	int idx, ret;
+	int idx;
 
 	idx = get_ctrl(gspca_dev, ctrl->id);
 	if (idx < 0)
@@ -1506,27 +1461,16 @@ static int vidioc_s_ctrl(struct file *file, void *priv,
 			return -ERANGE;
 	}
 	PDEBUG(D_CONF, "set ctrl [%08x] = %d", ctrl->id, ctrl->value);
-	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-		return -ERESTARTSYS;
-	if (!gspca_dev->present) {
-		ret = -ENODEV;
-		goto out;
-	}
 	gspca_dev->usb_err = 0;
-	if (ctrls->set != NULL) {
-		ret = ctrls->set(gspca_dev, ctrl->value);
-		goto out;
-	}
+	if (ctrls->set != NULL)
+		return ctrls->set(gspca_dev, ctrl->value);
 	if (gspca_ctrl != NULL) {
 		gspca_ctrl->val = ctrl->value;
 		if (ctrls->set_control != NULL
 		 && gspca_dev->streaming)
 			ctrls->set_control(gspca_dev);
 	}
-	ret = gspca_dev->usb_err;
-out:
-	mutex_unlock(&gspca_dev->usb_lock);
-	return ret;
+	return gspca_dev->usb_err;
 }
 
 static int vidioc_g_ctrl(struct file *file, void *priv,
@@ -1534,30 +1478,19 @@ static int vidioc_g_ctrl(struct file *file, void *priv,
 {
 	struct gspca_dev *gspca_dev = video_drvdata(file);
 	const struct ctrl *ctrls;
-	int idx, ret;
+	int idx;
 
 	idx = get_ctrl(gspca_dev, ctrl->id);
 	if (idx < 0)
 		return -EINVAL;
 	ctrls = &gspca_dev->sd_desc->ctrls[idx];
 
-	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-		return -ERESTARTSYS;
-	if (!gspca_dev->present) {
-		ret = -ENODEV;
-		goto out;
-	}
 	gspca_dev->usb_err = 0;
-	if (ctrls->get != NULL) {
-		ret = ctrls->get(gspca_dev, &ctrl->value);
-		goto out;
-	}
+	if (ctrls->get != NULL)
+		return ctrls->get(gspca_dev, &ctrl->value);
 	if (gspca_dev->cam.ctrls != NULL)
 		ctrl->value = gspca_dev->cam.ctrls[idx].val;
-	ret = 0;
-out:
-	mutex_unlock(&gspca_dev->usb_lock);
-	return ret;
+	return 0;
 }
 
 static int vidioc_querymenu(struct file *file, void *priv,
@@ -1640,10 +1573,8 @@ static int vidioc_reqbufs(struct file *file, void *priv,
 	/* stop streaming */
 	streaming = gspca_dev->streaming;
 	if (streaming) {
-		mutex_lock(&gspca_dev->usb_lock);
 		gspca_dev->usb_err = 0;
 		gspca_stream_off(gspca_dev);
-		mutex_unlock(&gspca_dev->usb_lock);
 
 		/* Don't restart the stream when switching from read
 		 * to mmap mode */
@@ -1748,13 +1679,8 @@ static int vidioc_streamoff(struct file *file, void *priv,
 	}
 
 	/* stop streaming */
-	if (mutex_lock_interruptible(&gspca_dev->usb_lock)) {
-		ret = -ERESTARTSYS;
-		goto out;
-	}
 	gspca_dev->usb_err = 0;
 	gspca_stream_off(gspca_dev);
-	mutex_unlock(&gspca_dev->usb_lock);
 	/* In case another thread is waiting in dqbuf */
 	wake_up_interruptible(&gspca_dev->wq);
 
@@ -1772,38 +1698,22 @@ static int vidioc_g_jpegcomp(struct file *file, void *priv,
 			struct v4l2_jpegcompression *jpegcomp)
 {
 	struct gspca_dev *gspca_dev = video_drvdata(file);
-	int ret;
 
 	if (!gspca_dev->sd_desc->get_jcomp)
 		return -ENOTTY;
-	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-		return -ERESTARTSYS;
 	gspca_dev->usb_err = 0;
-	if (gspca_dev->present)
-		ret = gspca_dev->sd_desc->get_jcomp(gspca_dev, jpegcomp);
-	else
-		ret = -ENODEV;
-	mutex_unlock(&gspca_dev->usb_lock);
-	return ret;
+	return gspca_dev->sd_desc->get_jcomp(gspca_dev, jpegcomp);
 }
 
 static int vidioc_s_jpegcomp(struct file *file, void *priv,
 			struct v4l2_jpegcompression *jpegcomp)
 {
 	struct gspca_dev *gspca_dev = video_drvdata(file);
-	int ret;
 
 	if (!gspca_dev->sd_desc->set_jcomp)
 		return -ENOTTY;
-	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-		return -ERESTARTSYS;
 	gspca_dev->usb_err = 0;
-	if (gspca_dev->present)
-		ret = gspca_dev->sd_desc->set_jcomp(gspca_dev, jpegcomp);
-	else
-		ret = -ENODEV;
-	mutex_unlock(&gspca_dev->usb_lock);
-	return ret;
+	return gspca_dev->sd_desc->set_jcomp(gspca_dev, jpegcomp);
 }
 
 static int vidioc_g_parm(struct file *filp, void *priv,
@@ -1814,21 +1724,10 @@ static int vidioc_g_parm(struct file *filp, void *priv,
 	parm->parm.capture.readbuffers = gspca_dev->nbufread;
 
 	if (gspca_dev->sd_desc->get_streamparm) {
-		int ret;
-
-		if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-			return -ERESTARTSYS;
-		if (gspca_dev->present) {
 		gspca_dev->usb_err = 0;
 		gspca_dev->sd_desc->get_streamparm(gspca_dev, parm);
-			ret = gspca_dev->usb_err;
-		} else {
-			ret = -ENODEV;
-		}
-		mutex_unlock(&gspca_dev->usb_lock);
-		return ret;
+		return gspca_dev->usb_err;
 	}
-
 	return 0;
 }
 
@@ -1845,19 +1744,9 @@ static int vidioc_s_parm(struct file *filp, void *priv,
 		gspca_dev->nbufread = n;
 
 	if (gspca_dev->sd_desc->set_streamparm) {
-		int ret;
-
-		if (mutex_lock_interruptible(&gspca_dev->usb_lock))
-			return -ERESTARTSYS;
-		if (gspca_dev->present) {
 		gspca_dev->usb_err = 0;
 		gspca_dev->sd_desc->set_streamparm(gspca_dev, parm);
-			ret = gspca_dev->usb_err;
-		} else {
-			ret = -ENODEV;
-		}
-		mutex_unlock(&gspca_dev->usb_lock);
-		return ret;
+		return gspca_dev->usb_err;
 	}
 
 	return 0;
@@ -1877,10 +1766,6 @@ static int dev_mmap(struct file *file, struct vm_area_struct *vma)
 
 	if (mutex_lock_interruptible(&gspca_dev->queue_lock))
 		return -ERESTARTSYS;
-	if (!gspca_dev->present) {
-		ret = -ENODEV;
-		goto out;
-	}
 	if (gspca_dev->capt_file != file) {
 		ret = -EINVAL;
 		goto out;
@@ -2008,14 +1893,6 @@ static int vidioc_dqbuf(struct file *file, void *priv,
 
 	gspca_dev->fr_o = (i + 1) % GSPCA_MAX_FRAMES;
 
-	if (gspca_dev->sd_desc->dq_callback) {
-		mutex_lock(&gspca_dev->usb_lock);
-		gspca_dev->usb_err = 0;
-		if (gspca_dev->present)
-			gspca_dev->sd_desc->dq_callback(gspca_dev);
-		mutex_unlock(&gspca_dev->usb_lock);
-	}
-
 	frame->v4l2_buf.flags &= ~V4L2_BUF_FLAG_DONE;
 	memcpy(v4l2_buf, &frame->v4l2_buf, sizeof *v4l2_buf);
 	PDEBUG(D_FRAM, "dqbuf %d", j);
@@ -2032,6 +1909,15 @@ static int vidioc_dqbuf(struct file *file, void *priv,
 	}
 out:
 	mutex_unlock(&gspca_dev->queue_lock);
+
+	if (ret == 0 && gspca_dev->sd_desc->dq_callback) {
+		mutex_lock(&gspca_dev->usb_lock);
+		gspca_dev->usb_err = 0;
+		if (gspca_dev->present)
+			gspca_dev->sd_desc->dq_callback(gspca_dev);
+		mutex_unlock(&gspca_dev->usb_lock);
+	}
+
 	return ret;
 }
 
@@ -2103,6 +1989,10 @@ static int read_alloc(struct gspca_dev *gspca_dev,
 	int i, ret;
 
 	PDEBUG(D_STREAM, "read alloc");
+
+	if (mutex_lock_interruptible(&gspca_dev->usb_lock))
+		return -ERESTARTSYS;
+
 	if (gspca_dev->nframes == 0) {
 		struct v4l2_requestbuffers rb;
 
@@ -2113,7 +2003,7 @@ static int read_alloc(struct gspca_dev *gspca_dev,
 		ret = vidioc_reqbufs(file, gspca_dev, &rb);
 		if (ret != 0) {
 			PDEBUG(D_STREAM, "read reqbuf err %d", ret);
-			return ret;
+			goto out;
 		}
 		memset(&v4l2_buf, 0, sizeof v4l2_buf);
 		v4l2_buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
@@ -2123,16 +2013,17 @@ static int read_alloc(struct gspca_dev *gspca_dev,
 			ret = vidioc_qbuf(file, gspca_dev, &v4l2_buf);
 			if (ret != 0) {
 				PDEBUG(D_STREAM, "read qbuf err: %d", ret);
-				return ret;
+				goto out;
 			}
 		}
-		gspca_dev->memory = GSPCA_MEMORY_READ;
 	}
 
 	/* start streaming */
 	ret = vidioc_streamon(file, gspca_dev, V4L2_BUF_TYPE_VIDEO_CAPTURE);
 	if (ret != 0)
 		PDEBUG(D_STREAM, "read streamon err %d", ret);
+out:
+	mutex_unlock(&gspca_dev->usb_lock);
 	return ret;
 }
 
@@ -2177,8 +2068,6 @@ static ssize_t dev_read(struct file *file, char __user *data,
 	int n, ret, ret2;
 
 	PDEBUG(D_FRAM, "read (%zd)", count);
-	if (!gspca_dev->present)
-		return -ENODEV;
 	if (gspca_dev->memory == GSPCA_MEMORY_NO) { /* first time ? */
 		ret = read_alloc(gspca_dev, file);
 		if (ret != 0)
@@ -2280,7 +2169,7 @@ static const struct video_device gspca_template = {
 	.name = "gspca main driver",
 	.fops = &dev_fops,
 	.ioctl_ops = &dev_ioctl_ops,
-	.release = gspca_release,
+	.release = video_device_release_empty, /* We use v4l2_dev.release */
 };
 
 /* initialize the controls */
@@ -2352,6 +2241,7 @@ int gspca_dev_probe2(struct usb_interface *intf,
 		}
 	}
 
+	gspca_dev->v4l2_dev.release = gspca_release;
 	ret = v4l2_device_register(&intf->dev, &gspca_dev->v4l2_dev);
 	if (ret)
 		goto out;
@@ -2366,6 +2256,7 @@ int gspca_dev_probe2(struct usb_interface *intf,
 	gspca_dev->present = 1;
 
 	mutex_init(&gspca_dev->usb_lock);
+	gspca_dev->vdev.lock = &gspca_dev->usb_lock;
 	mutex_init(&gspca_dev->queue_lock);
 	init_waitqueue_head(&gspca_dev->wq);
 
@@ -2388,6 +2279,15 @@ int gspca_dev_probe2(struct usb_interface *intf,
 	if (ret)
 		goto out;
 
+	/*
+	 * Don't take usb_lock for these ioctls. This improves latency if
+	 * usb_lock is taken for a long time, e.g. when changing a control
+	 * value, and a new frame is ready to be dequeued.
+	 */
+	v4l2_dont_use_lock(&gspca_dev->vdev, VIDIOC_DQBUF);
+	v4l2_dont_use_lock(&gspca_dev->vdev, VIDIOC_QBUF);
+	v4l2_dont_use_lock(&gspca_dev->vdev, VIDIOC_QUERYBUF);
+
 	/* init video stuff */
 	ret = video_register_device(&gspca_dev->vdev,
 				  VFL_TYPE_GRABBER,
@@ -2455,11 +2355,13 @@ void gspca_disconnect(struct usb_interface *intf)
 
 	PDEBUG(D_PROBE, "%s disconnect",
 		video_device_node_name(&gspca_dev->vdev));
+
 	mutex_lock(&gspca_dev->usb_lock);
 
+	usb_set_intfdata(intf, NULL);
+	gspca_dev->dev = NULL;
 	gspca_dev->present = 0;
 	wake_up_interruptible(&gspca_dev->wq);
-
 	destroy_urbs(gspca_dev);
 
 #if defined(CONFIG_INPUT) || defined(CONFIG_INPUT_MODULE)
@@ -2471,18 +2373,13 @@ void gspca_disconnect(struct usb_interface *intf)
 	}
 #endif
 
-	/* the device is freed at exit of this function */
-	gspca_dev->dev = NULL;
 	v4l2_device_disconnect(&gspca_dev->v4l2_dev);
-	mutex_unlock(&gspca_dev->usb_lock);
+	video_unregister_device(&gspca_dev->vdev);
 
-	usb_set_intfdata(intf, NULL);
+	mutex_unlock(&gspca_dev->usb_lock);
 
-	/* release the device */
 	/* (this will call gspca_release() immediately or on last close) */
-	video_unregister_device(&gspca_dev->vdev);
-
-/*	PDEBUG(D_PROBE, "disconnect complete"); */
+	v4l2_device_put(&gspca_dev->v4l2_dev);
 }
 EXPORT_SYMBOL(gspca_disconnect);
 
@@ -2493,17 +2390,16 @@ int gspca_suspend(struct usb_interface *intf, pm_message_t message)
 
 	if (!gspca_dev->streaming)
 		return 0;
+	mutex_lock(&gspca_dev->usb_lock);
 	gspca_dev->frozen = 1;		/* avoid urb error messages */
 	if (gspca_dev->sd_desc->stopN)
 		gspca_dev->sd_desc->stopN(gspca_dev);
 	destroy_urbs(gspca_dev);
 	gspca_input_destroy_urb(gspca_dev);
 	gspca_set_alt0(gspca_dev);
-	if (gspca_dev->sd_desc->stop0) {
-		mutex_lock(&gspca_dev->usb_lock);
+	if (gspca_dev->sd_desc->stop0)
 		gspca_dev->sd_desc->stop0(gspca_dev);
 	mutex_unlock(&gspca_dev->usb_lock);
-	}
 	return 0;
 }
 EXPORT_SYMBOL(gspca_suspend);
@@ -2513,6 +2409,7 @@ int gspca_resume(struct usb_interface *intf)
 	struct gspca_dev *gspca_dev = usb_get_intfdata(intf);
 	int streaming, ret = 0;
 
+	mutex_lock(&gspca_dev->usb_lock);
 	gspca_dev->frozen = 0;
 	gspca_dev->sd_desc->init(gspca_dev);
 	gspca_input_create_urb(gspca_dev);
@@ -2524,11 +2421,9 @@ int gspca_resume(struct usb_interface *intf)
 	streaming = gspca_dev->streaming;
 	gspca_dev->streaming = 0;
 	v4l2_ctrl_handler_setup(gspca_dev->vdev.ctrl_handler);
-	if (streaming) {
-		mutex_lock(&gspca_dev->queue_lock);
+	if (streaming)
 		ret = gspca_init_transfer(gspca_dev);
-		mutex_unlock(&gspca_dev->queue_lock);
-	}
+	mutex_unlock(&gspca_dev->usb_lock);
 	return ret;
 }
 EXPORT_SYMBOL(gspca_resume);

drivers/media/video/gspca/gspca.h

@@ -163,6 +163,7 @@ struct gspca_dev {
 	struct v4l2_device v4l2_dev;
 	struct usb_device *dev;
 	struct file *capt_file;		/* file doing video capture */
+					/* protected by queue_lock */
 #if defined(CONFIG_INPUT) || defined(CONFIG_INPUT_MODULE)
 	struct input_dev *input_dev;
 	char phys[64];			/* physical device path */
@@ -192,7 +193,7 @@ struct gspca_dev {
 	u8 fr_o;				/* next frame to dequeue */
 	__u8 last_packet_type;
 	__s8 empty_packet;		/* if (-1) don't check empty packets */
-	__u8 streaming;
+	__u8 streaming;			/* protected by both mutexes (*) */
 
 	__u8 curr_mode;			/* current camera mode */
 	__u32 pixfmt;			/* current mode parameters */
@@ -214,6 +215,10 @@ struct gspca_dev {
 	__u8 iface;			/* USB interface number */
 	__u8 alt;			/* USB alternate setting */
 	u8 audio;			/* presence of audio device */
+
+	/* (*) These variables are proteced by both usb_lock and queue_lock,
+	   that is any code setting them is holding *both*, which means that
+	   any code getting them needs to hold at least one of them */
 };
 
 int gspca_dev_probe(struct usb_interface *intf,