diff mbox

[v4,4/6] media: uvcvideo: queue: Simplify spin-lock usage

Message ID ec54c7e1cfc4d1846c3dc09f27f609e7cf82b45c.1522168131.git-series.kieran.bingham@ideasonboard.com (mailing list archive)
State New, archived
Headers show

Commit Message

Kieran Bingham March 27, 2018, 4:46 p.m. UTC 
Both uvc_start_streaming(), and uvc_stop_streaming() are called from
userspace context, with interrupts enabled. 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>

---

v4:
 - Rebase to v4.16 (linux-media/master)

 drivers/media/usb/uvc/uvc_queue.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

Comments

Laurent Pinchart July 30, 2018, 7:57 p.m. UTC | #1 
Hi Kieran,

Thank you for the patch.

On Tuesday, 27 March 2018 19:46:01 EEST Kieran Bingham wrote:
> Both uvc_start_streaming(), and uvc_stop_streaming() are called from
> userspace context, with interrupts enabled. 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>
> 
> ---
> 
> v4:
>  - Rebase to v4.16 (linux-media/master)
> 
>  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 adcc4928fae4..698d9a5a5aae 100644
> --- a/drivers/media/usb/uvc/uvc_queue.c
> +++ b/drivers/media/usb/uvc/uvc_queue.c
> @@ -169,7 +169,6 @@ 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;
> @@ -178,9 +177,9 @@ 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;
>  }
> @@ -188,14 +187,13 @@ static int uvc_start_streaming(struct vb2_queue *vq,
> unsigned int count) static void uvc_stop_streaming(struct vb2_queue *vq)
>  {
>  	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
> -	unsigned long flags;
> 
>  	if (vq->type != V4L2_BUF_TYPE_META_CAPTURE)
>  		uvc_video_enable(uvc_queue_to_stream(queue), 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);
>  }

I think you missed my comment that stated

> Please add a one-line comment above both functions to state
>
> /* Must be called with interrupts enabled. */

Philipp Zabel commented that you could also add lockdep_assert_irqs_enabled(), 
and I think that's a good idea. I'll let you decide whether to do both, or 
only add lockdep_assert_irqs_enabled(), I'm fine with either option.

With this fixed,

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

>  static const struct vb2_ops uvc_queue_qops = {
Kieran Bingham Nov. 6, 2018, 3:10 p.m. UTC | #2 
Hi Laurent,

On 30/07/2018 20:57, Laurent Pinchart wrote:
> Hi Kieran,
> 
> Thank you for the patch.
> 
> On Tuesday, 27 March 2018 19:46:01 EEST Kieran Bingham wrote:
>> Both uvc_start_streaming(), and uvc_stop_streaming() are called from
>> userspace context, with interrupts enabled. 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>
>>
>> ---
>>
>> v4:
>>  - Rebase to v4.16 (linux-media/master)
>>
>>  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 adcc4928fae4..698d9a5a5aae 100644
>> --- a/drivers/media/usb/uvc/uvc_queue.c
>> +++ b/drivers/media/usb/uvc/uvc_queue.c
>> @@ -169,7 +169,6 @@ 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;
>> @@ -178,9 +177,9 @@ 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;
>>  }
>> @@ -188,14 +187,13 @@ static int uvc_start_streaming(struct vb2_queue *vq,
>> unsigned int count) static void uvc_stop_streaming(struct vb2_queue *vq)
>>  {
>>  	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
>> -	unsigned long flags;
>>
>>  	if (vq->type != V4L2_BUF_TYPE_META_CAPTURE)
>>  		uvc_video_enable(uvc_queue_to_stream(queue), 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);
>>  }
> 
> I think you missed my comment that stated
> 
>> Please add a one-line comment above both functions to state
>>
>> /* Must be called with interrupts enabled. */
> 
> Philipp Zabel commented that you could also add lockdep_assert_irqs_enabled(), 
> and I think that's a good idea. I'll let you decide whether to do both, or 
> only add lockdep_assert_irqs_enabled(), I'm fine with either option.
> 
> With this fixed,

I think code should talk louder than comments (especially as it provides
runtime verification and assertions when lockdep is enabled) - so I've
gone for Philipp's suggestion here.

> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> 

Collected, thanks.


>>  static const struct vb2_ops uvc_queue_qops = {
>
diff mbox

Patch

diff --git a/drivers/media/usb/uvc/uvc_queue.c b/drivers/media/usb/uvc/uvc_queue.c
index adcc4928fae4..698d9a5a5aae 100644
--- a/drivers/media/usb/uvc/uvc_queue.c
+++ b/drivers/media/usb/uvc/uvc_queue.c
@@ -169,7 +169,6 @@  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;
@@ -178,9 +177,9 @@  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;
 }
@@ -188,14 +187,13 @@  static int uvc_start_streaming(struct vb2_queue *vq, unsigned int count)
 static void uvc_stop_streaming(struct vb2_queue *vq)
 {
 	struct uvc_video_queue *queue = vb2_get_drv_priv(vq);
-	unsigned long flags;
 
 	if (vq->type != V4L2_BUF_TYPE_META_CAPTURE)
 		uvc_video_enable(uvc_queue_to_stream(queue), 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 = {