On Tue, 2018-01-16 at 19:23 +0200, Laurent Pinchart wrote:
> Hi Kieran,
>
> Thank you for the patch.
>
> On Friday, 12 January 2018 11:19:26 EET Kieran Bingham wrote:
> > Both uvc_start_streaming(), and uvc_stop_streaming() are called from
> > userspace context. As such, they do not need to save the IRQ state, and
> > can use spin_lock_irq() and spin_unlock_irq() respectively.
>
> Note that userspace context isn't enough, the key part is that they're called
> with interrupts enabled. If they were called from userspace context but under
> a spin_lock_irq() you couldn't use spin_unlock_irq() in those functions.
>
> > Signed-off-by: Kieran Bingham <kieran.bingham@xxxxxxxxxxxxxxxx>
> > ---
> > drivers/media/usb/uvc/uvc_queue.c | 10 ++++------
> > 1 file changed, 4 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_queue.c
> > b/drivers/media/usb/uvc/uvc_queue.c index 4a581d631525..ddac4d89a291 100644
> > --- a/drivers/media/usb/uvc/uvc_queue.c
> > +++ b/drivers/media/usb/uvc/uvc_queue.c
> > @@ -158,7 +158,6 @@ static int uvc_start_streaming(struct vb2_queue *vq,
> > unsigned int count) {
> > struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
> > struct uvc_streaming *stream = uvc_queue_to_stream(queue);
> > - unsigned long flags;
> > int ret;
> >
> > queue->buf_used = 0;
> > @@ -167,9 +166,9 @@ static int uvc_start_streaming(struct vb2_queue *vq,
> > unsigned int count) if (ret == 0)
> > return 0;
> >
> > - spin_lock_irqsave(&queue->irqlock, flags);
> > + spin_lock_irq(&queue->irqlock);
> > uvc_queue_return_buffers(queue, UVC_BUF_STATE_QUEUED);
> > - spin_unlock_irqrestore(&queue->irqlock, flags);
> > + spin_unlock_irq(&queue->irqlock);
> >
> > return ret;
> > }
> > @@ -178,13 +177,12 @@ static void uvc_stop_streaming(struct vb2_queue *vq)
> > {
> > struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
> > struct uvc_streaming *stream = uvc_queue_to_stream(queue);
> > - unsigned long flags;
> >
> > uvc_video_enable(stream, 0);
> >
> > - spin_lock_irqsave(&queue->irqlock, flags);
> > + spin_lock_irq(&queue->irqlock);
> > uvc_queue_return_buffers(queue, UVC_BUF_STATE_ERROR);
> > - spin_unlock_irqrestore(&queue->irqlock, flags);
> > + spin_unlock_irq(&queue->irqlock);
> > }
>
> Please add a one-line comment above both functions to state
>
> /* Must be called with interrupts enabled. */
You could add lockdep_assert_irqs_enabled() as well.
> With this and the commit message updated,
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
regards
Philipp
