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[media] vb2: fix 'UNBALANCED' warnings when calling vb2_thread_stop()
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>
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@ -3230,18 +3230,13 @@ int vb2_thread_stop(struct vb2_queue *q)
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if (threadio == NULL)
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if (threadio == NULL)
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return 0;
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return 0;
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call_void_qop(q, wait_finish, q);
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threadio->stop = true;
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threadio->stop = true;
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vb2_internal_streamoff(q, q->type);
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/* Wake up all pending sleeps in the thread */
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call_void_qop(q, wait_prepare, q);
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vb2_queue_error(q);
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err = kthread_stop(threadio->thread);
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err = kthread_stop(threadio->thread);
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q->fileio = NULL;
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__vb2_cleanup_fileio(q);
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fileio->req.count = 0;
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vb2_reqbufs(q, &fileio->req);
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kfree(fileio);
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threadio->thread = NULL;
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threadio->thread = NULL;
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kfree(threadio);
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kfree(threadio);
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q->fileio = NULL;
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q->threadio = NULL;
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q->threadio = NULL;
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return err;
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return err;
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}
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}
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