[media] gspca: Don't set gspca_dev->dev to NULL before stop0
authorHans de Goede <hdegoede@redhat.com>
Sun, 9 Sep 2012 09:30:02 +0000 (06:30 -0300)
committerMauro Carvalho Chehab <mchehab@redhat.com>
Thu, 13 Sep 2012 20:42:17 +0000 (17:42 -0300)
commit345321dc9c52b774f42c934339f9b3e2f0a39395
treea86e8fde0d50634c467c0c9d75b37776037e27d7
parent8c96f0a207bedb6f06089fde9adc7abe8136a087
[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>
drivers/media/usb/gspca/finepix.c
drivers/media/usb/gspca/gspca.c
drivers/media/usb/gspca/jl2005bcd.c
drivers/media/usb/gspca/sq905.c
drivers/media/usb/gspca/sq905c.c
drivers/media/usb/gspca/vicam.c
drivers/media/usb/gspca/xirlink_cit.c
drivers/media/usb/gspca/zc3xx.c