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<760d071e-0cbc-b3eb-9231-fb9f9ecb44a6@nvidia.com> <9e317f65-8a02-3b15-cfec-8e0d8374130e@gmail.com> <97b35910-4c93-123a-43a0-eb14476ed0f3@nvidia.com> Message-ID: <84ad4e2d-6ac1-e1f4-1c55-5edaae850631@nvidia.com> Date: Tue, 7 Apr 2020 14:08:36 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <97b35910-4c93-123a-43a0-eb14476ed0f3@nvidia.com> X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) To DRHQMAIL107.nvidia.com (10.27.9.16) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Content-Language: en-US DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1586293666; bh=p0/DWg6pW/GsSUz9X/po1THsEzzlpWiq+7OgvqVf1NM=; h=X-PGP-Universal:Subject:From:To:CC:References:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Transfer-Encoding: Content-Language; b=DSq+wk/V3vmE+OZKgrneo9QUGwCD2UhnoTfktGp0A8ZbgG8rvMFFD1PxmZ3QNra9x BpkKprgB69xcX2I6V087N4bEiXFF5pUZUvYVZsbDM3Fav0CS8kVt7Atz2Gd8es02Uj ymYRt1oWbK36galxrWt0IBJ4BjEP2a5tXdqzhi5sg+ZY71xVP6LtoLDYCObeTrZzf8 4FbiznmIgevIsI0xYXLA1VHS6VzaceTCVkHhkyP1sDKbrlNH0Rq+v48FDhg2N8ibwP 9j6sJ9T1wzbOzdwSYrRHsvfzzeNHO1tBE5SaAR2bRlyxlRtSTeHw7ZHp85fBRl3qw4 yoOjVnObn7/5w== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/6/20 4:48 PM, Sowjanya Komatineni wrote: > > On 4/6/20 4:18 PM, Dmitry Osipenko wrote: >> External email: Use caution opening links or attachments >> >> >> 07.04.2020 01:07, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>> 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 =D0=BF=D0=B8=D1=88=D0=B5=D1= =82: >>>>>>>>>>>>> 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=20 >>>>>>>>> >>>>>>>>> >>>>>>>> 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 =3D 2. > we hold on to issuing capture if more than 2 buffers are queued and it=20 > continues only after fifo has min 1 slot empty Just want to close on this part of feedback. Hope above explanation is=20 clear regarding triggering/issuing at max 2 frame capture to VI HW and=20 also regarding capture threads where they use wait_event_interruptible=20 to prevent blocking waiting for buffers to be available for captures. So no changes related to this part are needed in v7.