[media] dvb_usb_v2: do not free resources until delayed init is done

It was possible to free resources by unloading module while
initialization was still ongoing on delayed work.

Use PID to make decision on .disconnect() if caller is our
work or some other as work also calls .disconnect() in error
case. There could be better solution still...
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/dvb-usb/dvb_usb.h

@@ -322,6 +322,7 @@ struct dvb_usb_device {
 	struct dvb_usb_rc rc;
 	struct usb_device *udev;
 	struct work_struct probe_work;
+	pid_t work_pid;
 	struct usb_interface *intf;
 
 #define DVB_USB_STATE_INIT        0x000

drivers/media/dvb/dvb-usb/dvb_usb_init.c

@@ -266,10 +266,6 @@ int dvb_usb_device_power_ctrl(struct dvb_usb_device *d, int onoff)
 	return 0;
 }
 
-/*
- * USB
- */
-
 /*
  * udev, which is used for the firmware downloading, requires we cannot
  * block during module_init(). module_init() calls USB probe() which
@@ -284,7 +280,9 @@ static void dvb_usbv2_init_work(struct work_struct *work)
 			container_of(work, struct dvb_usb_device, probe_work);
 	bool cold = false;
 
-	pr_debug("%s:\n", __func__);
+	d->work_pid = current->pid;
+
+	pr_debug("%s: work_pid=%d\n", __func__, d->work_pid);
 
 	if (d->props.size_of_priv) {
 		d->priv = kzalloc(d->props.size_of_priv, GFP_KERNEL);
@@ -405,15 +403,12 @@ void dvb_usbv2_disconnect(struct usb_interface *intf)
 	struct dvb_usb_device *d = usb_get_intfdata(intf);
 	const char *name = "generic DVB-USB module";
 
-	pr_debug("%s:\n", __func__);
+	pr_debug("%s: pid=%d work_pid=%d\n", __func__, current->pid,
+			d->work_pid);
 
-	/*
-	 * FIXME: We should ensure initialization work is finished
-	 * until exit from this routine (cancel_work_sync / flush_work).
-	 * Unfortunately usb_driver_release_interface() call finally goes
-	 * here too and in that case we endup deadlock. How to perform
-	 * operation conditionally only on disconned / unload?
-	 */
+	/* ensure initialization work is finished until release resources */
+	if (d->work_pid != current->pid)
+		cancel_work_sync(&d->probe_work);
 
 	usb_set_intfdata(intf, NULL);
 	if (d) {