[media] gspca: Don't set gspca_dev->dev to NULL before stop0

In commit a3d6e8cc0e6ddc8b3cfdeb3c979f07ed1aa528b3 gspca_dev->dev is set
to NULL on disconnect, before calling stop0. The plan was to get rid of
gspca_dev->present and instead simply check for gspca_dev->dev everywhere
where we were checking for present. This should be race free since all users
of gspca_dev->dev hold the usb_lock, or so I thought.

But I was wrong, drivers which use a work-queue + synchronous bulk transfers
to get the video data don't hold the usb_lock while doing so, their stop0
callbacks stop the workqueue, so they won't be using gspca_dev->dev anymore
after the stop0 call, but they might be dereferincing it before, so we should
not set gspca_dev->dev to NULL on disconnect before calling stop0.

This also means that the workqueue functions in these drivers cannot
use gspca_dev->dev to check if they need to stop because of disconnection,
so we will need to keep gspca_dev->present around, and set that to 0 on
disconnect, before calling stop0. Unfortunately as part of the plan to remove
gspca_dev->present, these workqueues where already moved over to checking
for gspca_dev->dev instead of gspca_dev->present as part of commit
254902b01d2acc6aced99ec17caa4c6cd890cdea, so this patch also reverts those
parts of that commit.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 1 insertions, 2 deletions

diff --git a/drivers/media/usb/gspca/gspca.c b/drivers/media/usb/gspca/gspca.c
index d4e8343f5b10..7cce0f201d70 100644
--- a/drivers/media/usb/gspca/gspca.c
+++ b/drivers/media/usb/gspca/gspca.c
@@ -2358,8 +2358,6 @@ void gspca_disconnect(struct usb_interface *intf)
 
 	mutex_lock(&gspca_dev->usb_lock);
 
-	usb_set_intfdata(intf, NULL);
-	gspca_dev->dev = NULL;
 	gspca_dev->present = 0;
 	destroy_urbs(gspca_dev);
 
@@ -2375,6 +2373,7 @@ void gspca_disconnect(struct usb_interface *intf)
 	if (gspca_dev->sd_desc->stop0 && gspca_dev->streaming)
 		gspca_dev->sd_desc->stop0(gspca_dev);
 	gspca_dev->streaming = 0;
+	gspca_dev->dev = NULL;
 	wake_up_interruptible(&gspca_dev->wq);
 
 	v4l2_device_disconnect(&gspca_dev->v4l2_dev);