From: Dmitry Osipenko <digetx@gmail.com>
To: Sowjanya Komatineni <skomatineni@nvidia.com>,
thierry.reding@gmail.com, jonathanh@nvidia.com,
frankc@nvidia.com, hverkuil@xs4all.nl, sakari.ailus@iki.fi,
helen.koike@collabora.com
Cc: sboyd@kernel.org, linux-media@vger.kernel.org,
devicetree@vger.kernel.org, linux-clk@vger.kernel.org,
linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver
Date: Tue, 7 Apr 2020 02:18:04 +0300 [thread overview]
Message-ID: <9e317f65-8a02-3b15-cfec-8e0d8374130e@gmail.com> (raw)
In-Reply-To: <760d071e-0cbc-b3eb-9231-fb9f9ecb44a6@nvidia.com>
07.04.2020 01:07, Sowjanya Komatineni пишет:
>
> On 4/6/20 3:00 PM, Sowjanya Komatineni wrote:
>>
>> On 4/6/20 2:39 PM, Sowjanya Komatineni wrote:
>>>
>>> On 4/6/20 2:15 PM, Sowjanya Komatineni wrote:
>>>>
>>>> On 4/6/20 2:11 PM, Dmitry Osipenko wrote:
>>>>> External email: Use caution opening links or attachments
>>>>>
>>>>>
>>>>> 07.04.2020 00:02, Sowjanya Komatineni пишет:
>>>>>>>>>>> Am I understanding correctly that this thread will take 100%
>>>>>>>>>>> CPU,
>>>>>>>>>>> spinning here, if more than 2 frame-captures queued?
>>>>>>>>>> on more than 2 frames captures, it breaks thread and on next
>>>>>>>>>> wakeup it
>>>>>>>>>> continues
>>>>>>>>> The wait_event() won't wait if condition is true.
>>>>>>>> condition is checked when waitqueue is woken up
>>>>>>> https://elixir.bootlin.com/linux/v5.6.2/source/include/linux/wait.h#L462
>>>>>>>
>>>>>> process is put to sleep until the condition evaluates to true or
>>>>>> signal
>>>>>> is received.
>>>>>>
>>>>>> condition is checked each time the waitqueue head is woken up.
>>>>> This is a wrong assumption in accordance to the code.
>>
>> process is in sleep until the condition is evaluated and when
>> condition is true wakeup still happens only when wake_up on waitqueue
>> is called
>>
>> This is the reason for using this to prevent blocking while waiting
>> for the buffers.
>
> w.r.t capture list update, wakeup happens when wake_up on waitqueue is
> called.
>
> wakeup also happens on kthread stop signal event.
>
>>
>>
>>>>
>>>> when every buffer is available as long as we are in streaming, we
>>>> should process it.
>>>>
>>>> So if wake up happens when list has buffer, it will be processed but
>>>> at a time we limit processing 2 simultaneous buffer capture starts
>>>> only.
>>>>
>>> Fixing typo.
>>>
>>> I meant when ever buffer is available as long as we are in streaming,
>>> we should process it.
>>>
>>> So capture thread processes as long as buffers are available from
>>> user space limiting 2 simultaneous trigger of captures and thread
>>> will be in sleep when capture buffers list is empty or no stop thread
>>> is signaled.
IIUC, the waiting won't happen if more than 2 captures are queued and
thread will be spinning until captures are processed.
I think you need a semaphore with resource count = 2.
next prev parent reply other threads:[~2020-04-06 23:18 UTC|newest]
Thread overview: 80+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-04 1:24 [RFC PATCH v6 0/9] Add Tegra driver for video capture Sowjanya Komatineni
2020-04-04 1:24 ` [RFC PATCH v6 1/9] arm64: tegra: Fix sor powergate clocks and reset Sowjanya Komatineni
2020-04-04 1:25 ` [RFC PATCH v6 2/9] arm64: tegra: Add reset-cells to mc Sowjanya Komatineni
2020-04-04 1:25 ` [RFC PATCH v6 3/9] dt-bindings: clock: tegra: Add clk id for CSI TPG clock Sowjanya Komatineni
2020-04-14 18:12 ` Rob Herring
2020-04-04 1:25 ` [RFC PATCH v6 4/9] clk: tegra: Add Tegra210 CSI TPG clock gate Sowjanya Komatineni
2020-04-04 1:25 ` [RFC PATCH v6 5/9] dt-binding: tegra: Add VI and CSI bindings Sowjanya Komatineni
2020-04-14 18:14 ` Rob Herring
2020-04-04 1:25 ` [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver Sowjanya Komatineni
2020-04-05 19:37 ` Dmitry Osipenko
2020-04-06 18:58 ` Sowjanya Komatineni
2020-04-05 19:45 ` Dmitry Osipenko
2020-04-05 19:57 ` Dmitry Osipenko
2020-04-05 19:51 ` Dmitry Osipenko
2020-04-05 20:35 ` Dmitry Osipenko
2020-04-06 15:35 ` Sowjanya Komatineni
2020-04-06 16:05 ` Dmitry Osipenko
2020-04-06 16:12 ` Sowjanya Komatineni
2020-04-06 16:29 ` Dmitry Osipenko
2020-04-06 16:37 ` Sowjanya Komatineni
2020-04-06 17:02 ` Sowjanya Komatineni
2020-04-06 19:53 ` Dmitry Osipenko
2020-04-06 20:05 ` Sowjanya Komatineni
2020-04-06 20:28 ` Dmitry Osipenko
2020-04-06 20:30 ` Sowjanya Komatineni
2020-04-05 20:54 ` Dmitry Osipenko
2020-04-05 21:11 ` Dmitry Osipenko
2020-04-06 15:41 ` Sowjanya Komatineni
2020-04-06 16:11 ` Dmitry Osipenko
2020-04-07 19:05 ` Sowjanya Komatineni
2020-04-06 19:48 ` Dmitry Osipenko
2020-04-06 20:00 ` Sowjanya Komatineni
2020-04-06 20:02 ` Dmitry Osipenko
2020-04-06 20:20 ` Sowjanya Komatineni
2020-04-06 20:37 ` Dmitry Osipenko
2020-04-06 20:38 ` Sowjanya Komatineni
2020-04-06 20:43 ` Sowjanya Komatineni
2020-04-06 20:54 ` Dmitry Osipenko
2020-04-06 21:18 ` Sowjanya Komatineni
2020-04-06 20:45 ` Dmitry Osipenko
2020-04-06 20:50 ` Sowjanya Komatineni
2020-04-06 20:53 ` Dmitry Osipenko
2020-04-06 20:55 ` Sowjanya Komatineni
2020-04-06 20:56 ` Dmitry Osipenko
2020-04-06 21:02 ` Sowjanya Komatineni
2020-04-06 21:11 ` Dmitry Osipenko
2020-04-06 21:15 ` Sowjanya Komatineni
2020-04-06 21:39 ` Sowjanya Komatineni
2020-04-06 22:00 ` Sowjanya Komatineni
2020-04-06 22:07 ` Sowjanya Komatineni
2020-04-06 23:18 ` Dmitry Osipenko [this message]
2020-04-06 23:48 ` Sowjanya Komatineni
2020-04-06 23:50 ` Sowjanya Komatineni
2020-04-07 21:08 ` Sowjanya Komatineni
2020-04-07 22:08 ` Dmitry Osipenko
2020-04-07 22:14 ` Dmitry Osipenko
2020-04-07 22:22 ` Sowjanya Komatineni
2020-04-07 23:12 ` Dmitry Osipenko
[not found] ` <1a31cd60-739f-0660-1c45-31487d2f2128@nvidia.com>
2020-04-07 23:38 ` Sowjanya Komatineni
2020-04-07 23:56 ` Sowjanya Komatineni
2020-04-07 23:57 ` Sowjanya Komatineni
2020-04-07 23:59 ` Sowjanya Komatineni
2020-04-08 0:00 ` Sowjanya Komatineni
2020-04-08 14:21 ` Dmitry Osipenko
2020-04-08 17:45 ` Sowjanya Komatineni
2020-04-08 18:58 ` Sowjanya Komatineni
2020-04-08 19:38 ` Sowjanya Komatineni
2020-04-09 3:38 ` Sowjanya Komatineni
2020-04-09 14:50 ` Dmitry Osipenko
2020-04-09 18:28 ` Sowjanya Komatineni
2020-04-10 18:47 ` Dmitry Osipenko
2020-04-10 18:59 ` Sowjanya Komatineni
2020-04-10 19:45 ` Dmitry Osipenko
2020-04-07 19:39 ` Dmitry Osipenko
2020-04-07 19:42 ` Sowjanya Komatineni
2020-04-10 19:47 ` Dmitry Osipenko
2020-04-04 1:25 ` [RFC PATCH v6 7/9] MAINTAINERS: Add Tegra Video driver section Sowjanya Komatineni
2020-04-04 1:25 ` [RFC PATCH v6 8/9] dt-bindings: reset: Add ID for Tegra210 VI reset Sowjanya Komatineni
2020-04-14 18:14 ` Rob Herring
2020-04-04 1:25 ` [RFC PATCH v6 9/9] arm64: tegra: Add Tegra VI CSI support in device tree Sowjanya Komatineni
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