Hi Figo Zhang,
On Monday 18 of May 2009 at 04:13:13, figo.zhang wrote:
> saa7134-video.c: poll method lose race condition
>
>
> Signed-off-by: Figo.zhang <figo.zhang@xxxxxxxxxxxxx>
> ---
> drivers/media/video/saa7134/saa7134-video.c | 9 ++++++---
> 1 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/video/saa7134/saa7134-video.c
> b/drivers/media/video/saa7134/saa7134-video.c index 493cad9..95733df 100644
> --- a/drivers/media/video/saa7134/saa7134-video.c
> +++ b/drivers/media/video/saa7134/saa7134-video.c
> @@ -1423,11 +1423,13 @@ video_poll(struct file *file, struct
> poll_table_struct *wait) {
> struct saa7134_fh *fh = file->private_data;
> struct videobuf_buffer *buf = NULL;
> + unsigned int rc = 0;
>
> if (V4L2_BUF_TYPE_VBI_CAPTURE == fh->type)
> return videobuf_poll_stream(file, &fh->vbi, wait);
>
> if (res_check(fh,RESOURCE_VIDEO)) {
> + mutex_lock(&fh->cap.vb_lock);
> if (!list_empty(&fh->cap.stream))
> buf = list_entry(fh->cap.stream.next, struct videobuf_buffer, stream);
> } else {
> @@ -1446,13 +1448,14 @@ video_poll(struct file *file, struct
> poll_table_struct *wait) }
>
> if (!buf)
> - return POLLERR;
> + rc = POLLERR;
Just one note (I don't know the future and meaning of this patch). The line
above will change the meaning of the buf==NULL check. It will not return
immediately, but call poll_wait with buf->done instead - NULL pointer access.
Cheers,
Oldrich.
>
> poll_wait(file, &buf->done, wait);
> if (buf->state == VIDEOBUF_DONE ||
> buf->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);
>
>
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