[v3,1/3] media: uvcvideo: Always use uvc_status_stop()

uvc_status_stop() handles properly the race conditions with the
asynchronous worker.
Let's use uvc_status_stop() for all the code paths that require stopping
it.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
---
 drivers/media/usb/uvc/uvc_ctrl.c   | 4 ----
 drivers/media/usb/uvc/uvc_status.c | 2 +-
 2 files changed, 1 insertion(+), 5 deletions(-)

Hi Sergey

On Wed, 22 Nov 2023 at 08:21, Sergey Senozhatsky
<senozhatsky@chromium.org> wrote:
>
> On (23/11/21 19:53), Ricardo Ribalda wrote:
> > uvc_status_stop() handles properly the race conditions with the
> > asynchronous worker.
> > Let's use uvc_status_stop() for all the code paths that require stopping
> > it.
> >
> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > ---
> >  drivers/media/usb/uvc/uvc_ctrl.c   | 4 ----
> >  drivers/media/usb/uvc/uvc_status.c | 2 +-
> >  2 files changed, 1 insertion(+), 5 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > index e59a463c2761..8e22a07e3e7b 100644
> > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > @@ -2765,10 +2765,6 @@ void uvc_ctrl_cleanup_device(struct uvc_device *dev)
> >       struct uvc_entity *entity;
> >       unsigned int i;
> >
> > -     /* Can be uninitialized if we are aborting on probe error. */
> > -     if (dev->async_ctrl.work.func)
> > -             cancel_work_sync(&dev->async_ctrl.work);
> > -
> >       /* Free controls and control mappings for all entities. */
> >       list_for_each_entry(entity, &dev->entities, list) {
> >               for (i = 0; i < entity->ncontrols; ++i) {
> > diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
> > index a78a88c710e2..0208612a9f12 100644
> > --- a/drivers/media/usb/uvc/uvc_status.c
> > +++ b/drivers/media/usb/uvc/uvc_status.c
> > @@ -292,7 +292,7 @@ int uvc_status_init(struct uvc_device *dev)
> >
> >  void uvc_status_unregister(struct uvc_device *dev)
> >  {
> > -     usb_kill_urb(dev->int_urb);
> > +     uvc_status_stop(dev);
>
> Sort of feels like this needs dev->lock somewhere here. Should we move 3/3
> to the head of the series?
>
> The question is, can this be called in parallel with uvc_v4l2_release(),
> for instance?

I can be called in parallel with uvc_v4l2_release(), but
uvc_status_stop() is thread-safe and does not take any locks after:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=619d9b710cf06f7a00a17120ca92333684ac45a8

So this "should" be good. key-word here is should :P


>
> >       uvc_input_unregister(dev);
> >  }

Hi Sergey

On Wed, 22 Nov 2023 at 08:35, Ricardo Ribalda <ribalda@chromium.org> wrote:
>
> Hi Sergey
>
> On Wed, 22 Nov 2023 at 08:21, Sergey Senozhatsky
> <senozhatsky@chromium.org> wrote:
> >
> > On (23/11/21 19:53), Ricardo Ribalda wrote:
> > > uvc_status_stop() handles properly the race conditions with the
> > > asynchronous worker.
> > > Let's use uvc_status_stop() for all the code paths that require stopping
> > > it.
> > >
> > > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> > > ---
> > >  drivers/media/usb/uvc/uvc_ctrl.c   | 4 ----
> > >  drivers/media/usb/uvc/uvc_status.c | 2 +-
> > >  2 files changed, 1 insertion(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/media/usb/uvc/uvc_ctrl.c b/drivers/media/usb/uvc/uvc_ctrl.c
> > > index e59a463c2761..8e22a07e3e7b 100644
> > > --- a/drivers/media/usb/uvc/uvc_ctrl.c
> > > +++ b/drivers/media/usb/uvc/uvc_ctrl.c
> > > @@ -2765,10 +2765,6 @@ void uvc_ctrl_cleanup_device(struct uvc_device *dev)
> > >       struct uvc_entity *entity;
> > >       unsigned int i;
> > >
> > > -     /* Can be uninitialized if we are aborting on probe error. */
> > > -     if (dev->async_ctrl.work.func)
> > > -             cancel_work_sync(&dev->async_ctrl.work);
> > > -
> > >       /* Free controls and control mappings for all entities. */
> > >       list_for_each_entry(entity, &dev->entities, list) {
> > >               for (i = 0; i < entity->ncontrols; ++i) {
> > > diff --git a/drivers/media/usb/uvc/uvc_status.c b/drivers/media/usb/uvc/uvc_status.c
> > > index a78a88c710e2..0208612a9f12 100644
> > > --- a/drivers/media/usb/uvc/uvc_status.c
> > > +++ b/drivers/media/usb/uvc/uvc_status.c
> > > @@ -292,7 +292,7 @@ int uvc_status_init(struct uvc_device *dev)
> > >
> > >  void uvc_status_unregister(struct uvc_device *dev)
> > >  {
> > > -     usb_kill_urb(dev->int_urb);
> > > +     uvc_status_stop(dev);
> >
> > Sort of feels like this needs dev->lock somewhere here. Should we move 3/3
> > to the head of the series?
> >
> > The question is, can this be called in parallel with uvc_v4l2_release(),
> > for instance?
>
> I can be called in parallel with uvc_v4l2_release(), but
> uvc_status_stop() is thread-safe and does not take any locks after:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=619d9b710cf06f7a00a17120ca92333684ac45a8
>
> So this "should" be good. key-word here is should :P

To be on the safe side I am not going to run the async work on the
release path. will send a new revision

>
>
> >
> > >       uvc_input_unregister(dev);
> > >  }
>
>
>
> --
> Ricardo Ribalda

Hi Sakari

On Wed, 22 Nov 2023 at 10:58, Sakari Ailus <sakari.ailus@iki.fi> wrote:
>
> Hi Ricardo,
>
> On Tue, Nov 21, 2023 at 07:53:48PM +0000, Ricardo Ribalda wrote:
> > uvc_status_stop() handles properly the race conditions with the
> > asynchronous worker.
> > Let's use uvc_status_stop() for all the code paths that require stopping
> > it.
> >
> > Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
>
> Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Thanks! I have slightly changed the code in v3 and kept your tag, hope
that it is fine.

Regards!

>
> --
> Sakari Ailus