On 4/6/20 1:02 PM, Dmitry Osipenko wrote:
External email: Use caution opening links or attachments
04.04.2020 04:25, Sowjanya Komatineni пишет:
...
+static int chan_capture_kthread_start(void *data)
+{
+ struct tegra_vi_channel *chan = data;
+ struct tegra_channel_buffer *buf;
+ int err = 0;
+ int caps_inflight;
+
+ set_freezable();
+
+ while (1) {
+ try_to_freeze();
+
+ wait_event_interruptible(chan->start_wait,
+ !list_empty(&chan->capture) ||
+ kthread_should_stop());
Is it really okay that list_empty() isn't protected with a lock?
Why wait_event is "interruptible"?
To allow it to sleep until wakeup on thread it to avoid constant
checking for condition even when no buffers are ready, basically to
prevent blocking.
+ /*
+ * Frame start and MW_ACK_DONE syncpoint condition FIFOs are
+ * of max depth 2. So make sure max 2 capture requests are
+ * in process by the hardware at a time.
+ */
+ while (!(kthread_should_stop() || list_empty(&chan->capture))) {
+ caps_inflight = chan->capture_reqs - chan->sequence;
+ /*
+ * Source is not streaming if error is non-zero.
+ * So, do not dequeue buffers on capture error or when
+ * syncpoint requests in FIFO are full.
+ */
+ if (err || caps_inflight >= SYNCPT_FIFO_DEPTH)
+ break;
+
+ /* dequeue the buffer and start capture */
+ spin_lock(&chan->start_lock);
+ if (list_empty(&chan->capture))
+ break;
+ buf = list_entry(chan->capture.next,
+ struct tegra_channel_buffer, queue);
list_first_entry()
+ list_del_init(&buf->queue);
+ spin_unlock(&chan->start_lock);
+
+ err = tegra_channel_capture_frame(chan, buf);
+ if (err)
+ vb2_queue_error(&chan->queue);
+ }
+
+ if (kthread_should_stop())
+ break;
+ }
+
+ return 0;
+}
