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

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Message-ID: <c6d54885-6f23-f60c-a17b-3481fc4d6adf@gmail.com>
Date:   Thu, 30 Apr 2020 17:13:37 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com, frankc@...dia.com,
        hverkuil@...all.nl, sakari.ailus@....fi, helen.koike@...labora.com
Cc:     sboyd@...nel.org, linux-media@...r.kernel.org,
        devicetree@...r.kernel.org, linux-clk@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v11 6/9] media: tegra: Add Tegra210 Video input driver

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();