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

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Date:   Fri, 24 Apr 2020 02:25:48 +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 v9 6/9] media: tegra: Add Tegra210 Video input driver

24.04.2020 02:20, Sowjanya Komatineni пишет:
> 
> On 4/23/20 4:19 PM, Sowjanya Komatineni wrote:
>>
>> On 4/23/20 4:16 PM, Dmitry Osipenko wrote:
>>> External email: Use caution opening links or attachments
>>>
>>>
>>> 22.04.2020 09:18, 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;
>>>> +
>>>> +     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.