Re: [RFC PATCH v9 6/9] media: tegra: Add Tegra210 Video input driver

From: Sowjanya Komatineni
Date: Thu Apr 23 2020 - 19:50:41 EST



On 4/23/20 4:25 PM, Dmitry Osipenko wrote:
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24.04.2020 02:20, Sowjanya Komatineni ÐÐÑÐÑ:
On 4/23/20 4:19 PM, Sowjanya Komatineni wrote:
On 4/23/20 4:16 PM, Dmitry Osipenko wrote:
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22.04.2020 09:18, Sowjanya Komatineni ÐÐÑÐÑ:
+static int chan_capture_kthread_start(void *data)
+{
+ struct tegra_vi_channel *chan = data;
+ struct tegra_channel_buffer *buf;
+ int err = 0;
+
+ set_freezable();
+
+ while (1) {
+ try_to_freeze();
+
+ wait_event_interruptible(chan->start_wait,
+ !list_empty(&chan->capture) ||
+ kthread_should_stop());
+
+ if (kthread_should_stop())
+ break;
+
+ /*
+ * Source is not streaming if error is non-zero.
+ * So, do not dequeue buffers on capture error.
+ */
+ if (err)
+ continue;
This will result in an endless loop, I suppose it wasn't the intention.
no it will not. on error we report vb2_queue_error which will do
streaming stop request.

So thread will be stopped on streaming stop request thru kthread stop
signal
To be clear on error it reports vb2 queue error and waits for stop
streaming to happen
If thread should exit on error, then it should do it on the actual
error. Otherwise it looks very error-prone.
When v4l2 drivers indicate fatal error through vb2_queue_error, queue error flag is set and wakes up all processes waiting on queue along with polling reporting EPOLLERR and also reporting error for queuing and dequeuing buffers. Stream stop will surely happen which stops the thread.