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| author | Hans Verkuil <hverkuil@xs4all.nl> | 2015-02-16 13:49:07 +0300 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2015-04-25 00:14:09 +0300 |
| commit | c6aa7146f15eb11c635dbbf48274db04a02241de (patch) | |
| tree | 5a507217b603230341e25329f3e645748425999b /drivers/media | |
| parent | 71871e8982c315c0fe3ba54c5b385f321135be7e (diff) | |
| download | linux-c6aa7146f15eb11c635dbbf48274db04a02241de.tar.xz | |
[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>
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 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; kfree(threadio); - q->fileio = NULL; q->threadio = NULL; return err; } |