[PATCH v1 1/2] Input: sur40 - don't wait for buffers nothing will complete

[Nguyen Ngoc Thang]

sur40_stop_streaming() calls vb2_wait_for_all_buffers() before handing
the queued buffers back. Those buffers are only completed from the input
poll callback, which is gone once the device is unplugged. Closing a
video node that is still streaming after a disconnect then sleeps
forever in vb2_wait_for_all_buffers():

  vb2_wait_for_all_buffers+0x20f/0x330
  sur40_stop_streaming+0x45/0x310
  __vb2_queue_cancel+0xc5/0xf70
  vb2_core_streamoff+0x5d/0x180
  __vb2_cleanup_fileio+0x6e/0x190
  vb2_core_queue_release+0x1f/0x190
  _vb2_fop_release+0xe8/0x280
  v4l2_release+0x280/0x430

It has not been noticed so far because sur40_disconnect() frees the
device state under the open file, and the close then crashes earlier.

Return the queued buffers first. A buffer that sur40_process_video()
has already taken off the list still completes by itself, so the wait
afterwards only covers that one.

Fixes: 6a8588156657 ("[media] sur40: fix occasional oopses on device close")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Nguyen Ngoc Thang <ngocthang2710.1999@xxxxxxxxx>
---
 drivers/input/touchscreen/sur40.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/input/touchscreen/sur40.c b/drivers/input/touchscreen/sur40.c
index 09d8c5f8d09f..7020bcf9b81a 100644
--- a/drivers/input/touchscreen/sur40.c
+++ b/drivers/input/touchscreen/sur40.c
@@ -929,11 +929,11 @@ static int sur40_start_streaming(struct vb2_queue *vq, unsigned int count)
 static void sur40_stop_streaming(struct vb2_queue *vq)
 {
 	struct sur40_state *sur40 = vb2_get_drv_priv(vq);
-	vb2_wait_for_all_buffers(vq);
-	sur40->sequence = -1;
 
-	/* Release all active buffers */
+	/* Release queued buffers first: nothing completes them after unplug */
 	return_all_buffers(sur40, VB2_BUF_STATE_ERROR);
+	vb2_wait_for_all_buffers(vq);
+	sur40->sequence = -1;
 }
 
 /* V4L ioctl */
-- 
2.43.0