V4L/DVB (12004): poll method lose race condition

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>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 10 insertions, 4 deletions

diff --git a/drivers/media/video/cx88/cx88-video.c b/drivers/media/video/cx88/cx88-video.c
index d6d6d13a6a6b..0ccac702bea4 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 = POLLERR;
 
         if (V4L2_BUF_TYPE_VBI_CAPTURE == fh->type) {
                 if (!res_get(fh->dev,fh,RESOURCE_VBI))
@@ -876,22 +877,27 @@ 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 done;
                 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 done;
         }
         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;
+        else
+                rc = 0;
+done:
+        mutex_unlock(&fh->vidq.vb_lock);
+        return rc;
 }
 
 static int video_release(struct file *file)