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Subject: Re: [RFC PATCH v11 6/9] media: tegra: Add Tegra210 Video input driver
To:     Dmitry Osipenko <digetx@gmail.com>, <thierry.reding@gmail.com>,
        <jonathanh@nvidia.com>, <frankc@nvidia.com>, <hverkuil@xs4all.nl>,
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From:   Sowjanya Komatineni <skomatineni@nvidia.com>
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On 4/30/20 7:13 AM, Dmitry Osipenko wrote:
> 30.04.2020 17:02, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>> 30.04.2020 16:56, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>>> 30.04.2020 01:00, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>>>> +static int chan_capture_kthread_finish(void *data)
>>>> +{
>>>> +	struct tegra_vi_channel *chan =3D 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=20
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=20
can freeze after capture done. This also don't need to check for=20
list_empty with freeze to allow between frame captures.