diff options
| author | Hans Verkuil <hverkuil@xs4all.nl> | 2015-02-16 07:49:07 -0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2015-04-19 10:10:26 +0200 |
| commit | 4858bcfdbcddd3e319f7621bb8044ebec2bacbeb (patch) | |
| tree | a50938f07a72e91520ead8c99650b8f7e255396f /drivers/media | |
| parent | 52c681ce5ea8a05624957824601a2eaa97125132 (diff) | |
vb2: fix 'UNBALANCED' warnings when calling vb2_thread_stop()
commit 0e661006370b7e7fb9ac9d94f9c3500a62cd559b upstream.
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>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/media')
| -rw-r--r-- | drivers/media/v4l2-core/videobuf2-core.c | 11 |
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 bc08a829bc13..cc16e76a2493 100644 --- a/drivers/media/v4l2-core/videobuf2-core.c +++ b/drivers/media/v4l2-core/videobuf2-core.c @@ -3230,18 +3230,13 @@ 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; kfree(threadio); - q->fileio = NULL; q->threadio = NULL; return err; } |