From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B05A8C2BB1D for ; Mon, 6 Apr 2020 22:00:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7E4D120857 for ; Mon, 6 Apr 2020 22:00:48 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="QOAyP0Pr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726370AbgDFWAr (ORCPT ); Mon, 6 Apr 2020 18:00:47 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:11924 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725933AbgDFWAr (ORCPT ); Mon, 6 Apr 2020 18:00:47 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Mon, 06 Apr 2020 14:59:04 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Mon, 06 Apr 2020 15:00:46 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Mon, 06 Apr 2020 15:00:46 -0700 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL105.nvidia.com (172.20.187.12) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Mon, 6 Apr 2020 22:00:45 +0000 Received: from [10.2.164.193] (172.20.13.39) by DRHQMAIL107.nvidia.com (10.27.9.16) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Mon, 6 Apr 2020 22:00:44 +0000 Subject: Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver From: Sowjanya Komatineni To: Dmitry Osipenko , , , , , , CC: , , , , , References: <1585963507-12610-1-git-send-email-skomatineni@nvidia.com> <1585963507-12610-7-git-send-email-skomatineni@nvidia.com> <200bb96e-2d07-764f-9e14-55538dc742fd@gmail.com> <23bfab09-b464-6e51-9843-06d13000e9b9@nvidia.com> <08cd31d5-e8b9-4d3a-fb0e-0e4462947d96@nvidia.com> <12a834ac-52b1-6dc0-7d3a-3e6a1fa85a2a@gmail.com>

Message-ID: Date: Mon, 6 Apr 2020 15:00:43 -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: 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=1586210344; bh=q7GFnHqZjAtzTcVPeHp4RlPWhzeFozGIhEb3Mm0HjqM=; 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=QOAyP0PrWhtADDdqD4e3AsyTO8sFWG6Pb1/DQaH0lLQPwAmoEUhFhun0bpPT8h8KN /tWMGyNwBY719AQa/vPoyUpVFCjsGHVMr1sK9oSO8FE5R82fEH9p/c89f55dzLqn5H 4T0kXuD4Tdil2bKlbZjMreEcvBFpGGS3jegRaAO1MkSZjW7nFWHoklQmHbEJKOovf8 c6RfTptGMNgtv+yt03yBmAJvHXQ8qnqSfSSoaWfqI4j0CT7eZL6cWT342h6vRVQ+/t elGVor36c051hh0ZdSXC/1DNSM/N/iUzGq+eyP+moWYt7IQexOtoJjORiz30vFahGg DrKTLCR3LYN0w== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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=20 >>>>>>>> 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#L= 462=20 >>>>> >>>> process is put to sleep until the condition evaluates to true or=20 >>>> 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=20 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=20 the buffers. >> >> when every buffer is available as long as we are in streaming, we=20 >> should process it. >> >> So if wake up happens when list has buffer, it will be processed but=20 >> 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,=20 > we should process it. > > So capture thread processes as long as buffers are available from user=20 > space limiting 2 simultaneous trigger of captures and thread will be=20 > in sleep when capture buffers list is empty or no stop thread is=20 > signaled.