linux-kernel - Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver

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Message-ID: <200bb96e-2d07-764f-9e14-55538dc742fd@gmail.com>
Date:   Mon, 6 Apr 2020 23:45:24 +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 v6 6/9] media: tegra: Add Tegra210 Video input driver

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());
> +		/*
> +		 * 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;

Am I understanding correctly that this thread will take 100% CPU,
spinning here, if more than 2 frame-captures queued?