| Message ID | 9f83cda1d54615e068c20fcadf69a1f09ae50ec1.1515748369.git-series.kieran.bingham@ideasonboard.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@ideasonboard.com> > --- > 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. */ With this and the commit message updated, Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com> > static const struct vb2_ops uvc_queue_qops = {
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@ideasonboard.com> > > --- > > 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@ideasonboard.com> regards Philipp
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); } static const struct vb2_ops uvc_queue_qops = {
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. Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com> --- drivers/media/usb/uvc/uvc_queue.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-)