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, 7 insertions, 4 deletions

diff --git a/drivers/media/video/bt8xx/bttv-driver.c b/drivers/media/video/bt8xx/bttv-driver.c
index 7c1f82661ee..5eb1464af67 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 = POLLERR;
 
         if (V4L2_BUF_TYPE_VBI_CAPTURE == fh->type) {
                 if (!check_alloc_btres(fh->btv,fh,RESOURCE_VBI))
@@ -3160,9 +3161,10 @@ 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;
+                        goto err;
                 buf = list_entry(fh->cap.stream.next,struct bttv_buffer,vb.stream);
         } else {
                 /* read() capture */
@@ -3191,11 +3193,12 @@ 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;
+        else
+                rc = 0;
 err:
         mutex_unlock(&fh->cap.vb_lock);
-        return POLLERR;
+        return rc;
 }
 
 static int bttv_open(struct file *file)