diff options
authorHans Verkuil <hverkuil@xs4all.nl>2015-02-16 07:49:07 -0300
committerSasha Levin <sasha.levin@oracle.com>2015-04-24 17:14:09 -0400
commitc6aa7146f15eb11c635dbbf48274db04a02241de (patch)
parent71871e8982c315c0fe3ba54c5b385f321135be7e (diff)
[media] vb2: fix 'UNBALANCED' warnings when calling vb2_thread_stop()
[ Upstream commit 0e661006370b7e7fb9ac9d94f9c3500a62cd559b ] Stopping the vb2 thread (as used by several DVB devices) can result in an 'UNBALANCED' warning such as this: vb2: counters for queue ffff880407ee9828: UNBALANCED! vb2: setup: 1 start_streaming: 1 stop_streaming: 1 vb2: wait_prepare: 249333 wait_finish: 249334 This is due to a race condition between stopping the thread and calling vb2_internal_streamoff(). While I have not been able to deduce the exact mechanism how this race condition can produce this warning, I can see that the way the stream is stopped is likely to lead to a race somewhere. This patch simplifies how this is done by first ensuring that the thread is completely stopped before cleaning up the vb2 queue. It does that by setting threadio->stop to true, followed by a call to vb2_queue_error() which will wake up the thread. The thread sees that 'stop' is true and it will exit. The call to kthread_stop() waits until the thread has exited, and only then is the queue cleaned up by calling __vb2_cleanup_fileio(). This is a much cleaner sequence and the warning has now disappeared. Reported-by: Jurgen Kramer <gtmkramer@xs4all.nl> Tested-by: Jurgen Kramer <gtmkramer@xs4all.nl> Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com> Cc: <stable@vger.kernel.org> # for v3.18 and up Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com> Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
1 files changed, 3 insertions, 8 deletions
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index ea36447c74f9..cc9537ef4829 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -3226,18 +3226,13 @@ int vb2_thread_stop(struct vb2_queue *q)
if (threadio == NULL)
return 0;
- call_void_qop(q, wait_finish, q);
threadio->stop = true;
- vb2_internal_streamoff(q, q->type);
- call_void_qop(q, wait_prepare, q);
+ /* Wake up all pending sleeps in the thread */
+ vb2_queue_error(q);
err = kthread_stop(threadio->thread);
- q->fileio = NULL;
- fileio->req.count = 0;
- vb2_reqbufs(q, &fileio->req);
- kfree(fileio);
+ __vb2_cleanup_fileio(q);
threadio->thread = NULL;
- q->fileio = NULL;
q->threadio = NULL;
return err;