V4L/DVB (11852): saa7134-video.c: poll method lose race condition

saa7134-video.c: poll method lose race condition

Signed-off-by: Figo Zhang <figo.zhang@kolorific.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

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 493cad941460..ceae3c88f93e 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;
+                goto err;
 
         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);