diff mbox

bttv-driver.c :poll method lose race condition for capture video

Message ID 1243751538.3425.6.camel@myhost (mailing list archive)
State Superseded
Headers show

Commit Message

Figo.zhang May 31, 2009, 6:32 a.m. UTC 
bttv-driver.c,cx23885-video.c,cx88-video.c: poll method lose race condition for capture video.

Signed-off-by: Figo.zhang <figo1802@gmail.com>
--- 
 drivers/media/video/bt8xx/bttv-driver.c     |    7 +++++--
 drivers/media/video/cx23885/cx23885-video.c |   15 +++++++++++----
 drivers/media/video/cx88/cx88-video.c       |   13 ++++++++++---
 3 files changed, 26 insertions(+), 9 deletions(-)



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Comments

Trent Piepho May 31, 2009, 9:29 p.m. UTC | #1 
On Sun, 31 May 2009, Figo.zhang wrote:

> bttv-driver.c,cx23885-video.c,cx88-video.c: poll method lose race condition for capture video.

Please use patch titles that are not so long.  It would be nice if you
could describe this race condition.

>
> Signed-off-by: Figo.zhang <figo1802@gmail.com>
> ---
>  drivers/media/video/bt8xx/bttv-driver.c     |    7 +++++--
>  drivers/media/video/cx23885/cx23885-video.c |   15 +++++++++++----
>  drivers/media/video/cx88/cx88-video.c       |   13 ++++++++++---
>  3 files changed, 26 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/media/video/bt8xx/bttv-driver.c b/drivers/media/video/bt8xx/bttv-driver.c
> index 23b7499..9cadfcc 100644
> --- a/drivers/media/video/bt8xx/bttv-driver.c
> +++ b/drivers/media/video/bt8xx/bttv-driver.c
> @@ -3152,6 +3152,7 @@ static unsigned int bttv_poll(struct file *file, poll_table *wait)
>  	struct bttv_fh *fh = file->private_data;
>  	struct bttv_buffer *buf;
>  	enum v4l2_field field;
> +	unsigned int rc = 0;
>
>  	if (V4L2_BUF_TYPE_VBI_CAPTURE == fh->type) {
>  		if (!check_alloc_btres(fh->btv,fh,RESOURCE_VBI))
> @@ -3160,6 +3161,7 @@ static unsigned int bttv_poll(struct file *file, poll_table *wait)
>  	}
>
>  	if (check_btres(fh,RESOURCE_VIDEO_STREAM)) {
> +		mutex_lock(&fh->cap.vb_lock);
>  		/* streaming capture */
>  		if (list_empty(&fh->cap.stream))
>  			return POLLERR;

Won't you return with the mutex held here?

> @@ -3191,8 +3193,9 @@ static unsigned int bttv_poll(struct file *file, poll_table *wait)
>  	poll_wait(file, &buf->vb.done, wait);
>  	if (buf->vb.state == VIDEOBUF_DONE ||
>  	    buf->vb.state == VIDEOBUF_ERROR)
> -		return POLLIN|POLLRDNORM;
> -	return 0;
> +		rc = POLLIN|POLLRDNORM;
> +	mutex_unlock(&fh->cap.vb_lock);
> +	return rc;
>  err:
>  	mutex_unlock(&fh->cap.vb_lock);
>  	return POLLERR;

I think the logic for these changes will be cleaner to do something like this:

{
	unsigned int rc = POLLERR;

	if (some error);
		goto done;
	if (other error)
		goto done;

	if (buf->vb.state == VIDEOBUF_DONE ||
            buf->vb.state == VIDEOBUF_ERROR)
		rc = POLLIN|POLLRDNORM;
	else
		rc = 0;

done:
	mutex_unlock(&fh->vidq.vb_lock);
	return rc;
}
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diff mbox

Patch

diff --git a/drivers/media/video/bt8xx/bttv-driver.c b/drivers/media/video/bt8xx/bttv-driver.c
index 23b7499..9cadfcc 100644
--- a/drivers/media/video/bt8xx/bttv-driver.c
+++ b/drivers/media/video/bt8xx/bttv-driver.c
@@ -3152,6 +3152,7 @@  static unsigned int bttv_poll(struct file *file, poll_table *wait)
 	struct bttv_fh *fh = file->private_data;
 	struct bttv_buffer *buf;
 	enum v4l2_field field;
+	unsigned int rc = 0;
 
 	if (V4L2_BUF_TYPE_VBI_CAPTURE == fh->type) {
 		if (!check_alloc_btres(fh->btv,fh,RESOURCE_VBI))
@@ -3160,6 +3161,7 @@  static unsigned int bttv_poll(struct file *file, poll_table *wait)
 	}
 
 	if (check_btres(fh,RESOURCE_VIDEO_STREAM)) {
+		mutex_lock(&fh->cap.vb_lock);
 		/* streaming capture */
 		if (list_empty(&fh->cap.stream))
 			return POLLERR;
@@ -3191,8 +3193,9 @@  static unsigned int bttv_poll(struct file *file, poll_table *wait)
 	poll_wait(file, &buf->vb.done, wait);
 	if (buf->vb.state == VIDEOBUF_DONE ||
 	    buf->vb.state == VIDEOBUF_ERROR)
-		return POLLIN|POLLRDNORM;
-	return 0;
+		rc = POLLIN|POLLRDNORM;
+	mutex_unlock(&fh->cap.vb_lock);
+	return rc;
 err:
 	mutex_unlock(&fh->cap.vb_lock);
 	return POLLERR;
diff --git a/drivers/media/video/cx23885/cx23885-video.c b/drivers/media/video/cx23885/cx23885-video.c
index 68068c6..386ad86 100644
--- a/drivers/media/video/cx23885/cx23885-video.c
+++ b/drivers/media/video/cx23885/cx23885-video.c
@@ -796,6 +796,7 @@  static unsigned int video_poll(struct file *file,
 {
 	struct cx23885_fh *fh = file->private_data;
 	struct cx23885_buffer *buf;
+	unsigned int rc = 0;
 
 	if (V4L2_BUF_TYPE_VBI_CAPTURE == fh->type) {
 		if (!res_get(fh->dev, fh, RESOURCE_VBI))
@@ -803,23 +804,29 @@  static unsigned int video_poll(struct file *file,
 		return videobuf_poll_stream(file, &fh->vbiq, wait);
 	}
 
+	mutex_lock(&fh->vidq.vb_lock);
 	if (res_check(fh, RESOURCE_VIDEO)) {
 		/* streaming capture */
 		if (list_empty(&fh->vidq.stream))
-			return POLLERR;
+			goto err;
 		buf = list_entry(fh->vidq.stream.next,
 			struct cx23885_buffer, vb.stream);
 	} else {
 		/* read() capture */
 		buf = (struct cx23885_buffer *)fh->vidq.read_buf;
 		if (NULL == buf)
-			return POLLERR;
+			goto err;
 	}
 	poll_wait(file, &buf->vb.done, wait);
 	if (buf->vb.state == VIDEOBUF_DONE ||
 	    buf->vb.state == VIDEOBUF_ERROR)
-		return POLLIN|POLLRDNORM;
-	return 0;
+		rc = POLLIN|POLLRDNORM;
+	mutex_unlock(&fh->vidq.vb_lock);
+	return rc;
+
+err:
+	mutex_unlock(&fh->vidq.vb_lock);
+	return POLLERR;
 }
 
 static int video_release(struct file *file)
diff --git a/drivers/media/video/cx88/cx88-video.c b/drivers/media/video/cx88/cx88-video.c
index b993d42..f778d15 100644
--- a/drivers/media/video/cx88/cx88-video.c
+++ b/drivers/media/video/cx88/cx88-video.c
@@ -869,6 +869,7 @@  video_poll(struct file *file, struct poll_table_struct *wait)
 {
 	struct cx8800_fh *fh = file->private_data;
 	struct cx88_buffer *buf;
+	unsigned int rc = 0;
 
 	if (V4L2_BUF_TYPE_VBI_CAPTURE == fh->type) {
 		if (!res_get(fh->dev,fh,RESOURCE_VBI))
@@ -876,22 +877,28 @@  video_poll(struct file *file, struct poll_table_struct *wait)
 		return videobuf_poll_stream(file, &fh->vbiq, wait);
 	}
 
+	mutex_lock(&fh->vidq.vb_lock);
 	if (res_check(fh,RESOURCE_VIDEO)) {
 		/* streaming capture */
 		if (list_empty(&fh->vidq.stream))
-			return POLLERR;
+			goto err;
 		buf = list_entry(fh->vidq.stream.next,struct cx88_buffer,vb.stream);
 	} else {
 		/* read() capture */
 		buf = (struct cx88_buffer*)fh->vidq.read_buf;
 		if (NULL == buf)
-			return POLLERR;
+			goto err;
 	}
 	poll_wait(file, &buf->vb.done, wait);
 	if (buf->vb.state == VIDEOBUF_DONE ||
 	    buf->vb.state == VIDEOBUF_ERROR)
-		return POLLIN|POLLRDNORM;
+		rc = POLLIN|POLLRDNORM;
+	mutex_unlock(&fh->vidq.vb_lock);
 	return 0;
+
+err:
+	mutex_unlock(&fh->vidq.vb_lock);
+	return POLLERR;
 }
 
 static int video_release(struct file *file)