Re: [RFC PATCH v11 6/9] media: tegra: Add Tegra210 Video input driver

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On 4/30/20 9:04 AM, Sowjanya Komatineni wrote:

On 4/30/20 7:13 AM, Dmitry Osipenko wrote:
30.04.2020 17:02, Dmitry Osipenko пишет:
30.04.2020 16:56, Dmitry Osipenko пишет:
30.04.2020 01:00, Sowjanya Komatineni пишет:
+static int chan_capture_kthread_finish(void *data)
+{
+    struct tegra_vi_channel *chan = data;
+    struct tegra_channel_buffer *buf;
+
+    set_freezable();
+
+    while (1) {
+        try_to_freeze();
I guess it won't be great to freeze in the middle of a capture process, so:
        if (list_empty(&chan->done))
            try_to_freeze();
And here should be some locking protection in order not race with the
chan_capture_kthread_start because kthread_finish could freeze before
kthread_start.
Or maybe both start / finish threads should simply be allowed to freeze
only when both capture and done lists are empty.

if (list_empty(&chan->capture) &&
     list_empty(&chan->done))
    try_to_freeze();

good to freeze when not in middle of the frame capture but why should we not allow freeze in between captures?

Other drivers do allow freeze in between frame captures.

I guess we can freeze before dequeue for capture and in finish thread we can freeze after capture done. This also don't need to check for list_empty with freeze to allow between frame captures.

Also if we add check for both lists empty, freeze is not allowed as long as streaming is going on and in case of continuous streaming freeze will never happen.




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