Received: by 2002:a25:1985:0:0:0:0:0 with SMTP id 127csp2208051ybz; Thu, 30 Apr 2020 12:50:11 -0700 (PDT) X-Google-Smtp-Source: APiQypJqzHq0zlkqY2uNmrbWnXPOf8SD+qfYCj3h1Ebz/48Uj6KHH4uP4fCvkVw2DCbXXT7toBRD X-Received: by 2002:aa7:db41:: with SMTP id n1mr622002edt.314.1588276210868; Thu, 30 Apr 2020 12:50:10 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1588276210; cv=none; d=google.com; s=arc-20160816; b=mKyxSpZsTxSRPOgniwSskaPP4KT1hykwsGpv5D6PzPki61Tx0EkxdS6wW1/IUgzfXE BxgBLPrc6Rj1QlKNmfX5fsX0Y5Ypc92/QPn5gWnCvHbZcvBTKHgsAQ7h2lh72EoFI0Qo 1xuWb0jLCPwHixOC89H19mGoQVuFn5XDtZqNDpsyuFkLCD6V6QwWdRpuHjRaO7Ouxhq1 94eGf5OTwYu3uJOr3IOUF4oS+3HLbBmZS457yXMWUcNEkPSSQuhEf5o8RdDYKXroMiaS MGInJI2lrSSSmSHFOO8krDwy/JfUiKpsibgNqPHwrITQCDp8IpHNBqHPVnj5YBuHg4gq AHoQ== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=list-id:precedence:sender:dkim-signature:content-language :content-transfer-encoding:in-reply-to:mime-version:user-agent:date :message-id:from:references:cc:to:subject; bh=LFtJPl2MR0AiX6258PUQppdEd8eLbOAvI5VJBjgGH9g=; b=ErXOgNCuMMSIi4ZWAzfrnnMD0cfXw+aD3b39gHGd5bwIJS3jpi1ULYCuRaaBWN3C4u QVbUv+gYTCDsNS/TpDJ6sajxkeNkql3VCOClcFRRu3dMpR7uBQiUZgHLQvZDiEI5fvtH Twv80l2krud8RzRltibiR3kQekEvjiGyKOa+7h9Z+m8DJ0XeV4ealLEBrtw/ORkDhOrY 1o75xqxwaNzyFKPduTVgoXYS4mOXd33s3F09vbyiko6jr4r1H4A8YcMbR4e8A2M+2+70 fQIU2hrkUKd5i5ErdWgJnhlywQ/pBRiUczUZIHbeSpfwu9/sZt0hcwiy33syjoXtJOMp 13rg== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=eUHo0YmG; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Return-Path: Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18]) by mx.google.com with ESMTP id p32si304293edb.535.2020.04.30.12.49.47; Thu, 30 Apr 2020 12:50:10 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=eUHo0YmG; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726781AbgD3Trn (ORCPT + 99 others); Thu, 30 Apr 2020 15:47:43 -0400 Received: from hqnvemgate24.nvidia.com ([216.228.121.143]:12925 "EHLO hqnvemgate24.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726272AbgD3Trn (ORCPT ); Thu, 30 Apr 2020 15:47:43 -0400 Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate24.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 30 Apr 2020 12:45:38 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 30 Apr 2020 12:47:42 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 30 Apr 2020 12:47:42 -0700 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 30 Apr 2020 19:47:42 +0000 Received: from [10.2.165.152] (10.124.1.5) by DRHQMAIL107.nvidia.com (10.27.9.16) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 30 Apr 2020 19:47:41 +0000 Subject: Re: [RFC PATCH v11 6/9] media: tegra: Add Tegra210 Video input driver To: Dmitry Osipenko , , , , , , CC: , , , , , References: <1588197606-32124-1-git-send-email-skomatineni@nvidia.com> <1588197606-32124-7-git-send-email-skomatineni@nvidia.com> <4da289e6-036f-853b-beb4-379d6462adb0@gmail.com>

<7d31d24f-f353-7e82-3ff9-cdba8b773d1e@nvidia.com> <06a4a067-8d54-4322-b2a6-14e82eaeda29@nvidia.com> <47873bbd-cf90-4595-5a99-7e9113327ecc@nvidia.com> <71532440-f455-cc24-74f7-9ccad5947099@gmail.com> From: Sowjanya Komatineni Message-ID: Date: Thu, 30 Apr 2020 12:46:13 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <71532440-f455-cc24-74f7-9ccad5947099@gmail.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL105.nvidia.com (172.20.187.12) 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=1588275938; bh=LFtJPl2MR0AiX6258PUQppdEd8eLbOAvI5VJBjgGH9g=; h=X-PGP-Universal:Subject:To:CC:References:From:Message-ID:Date: User-Agent:MIME-Version:In-Reply-To:X-Originating-IP: X-ClientProxiedBy:Content-Type:Content-Transfer-Encoding: Content-Language; b=eUHo0YmGx9MVTjHCuaf0rRHK356SAAoY7t2g7NlB5sRu0G58FMNaweMLmuxhWq1a8 7j30zDua+ErzaQQYE7y4fgrbbXCzzeq3XXjOtZ7SRSzN81ZctWiWNKX0yCOjfRcmJh FwVH/uFGFRWw2JZB+rIqFTDd+Ga01nJZz0LbsjIw/AnMxVqQ+E3u9heYElVMe6qupL mLXDMf6FmQpxSUMm4HD+qJ/KxWy7u+YXc4H66TzZtHcS/HKn3KlikWEUd9yQGF6bJC NZ/x4JZXdPP5mguxapxvrNj48L3QdJI3RsZ6Qh3Rew6tC9FfQj+KxNd50nQjnDPx4v lRfC1wQfkjWiQ== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/30/20 12:33 PM, Dmitry Osipenko wrote: > 30.04.2020 22:09, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> On 4/30/20 11:18 AM, Sowjanya Komatineni wrote: >>> On 4/30/20 10:06 AM, Sowjanya Komatineni wrote: >>>> On 4/30/20 9:29 AM, Sowjanya Komatineni wrote: >>>>> On 4/30/20 9:04 AM, Sowjanya Komatineni wrote: >>>>>> On 4/30/20 7:13 AM, Dmitry Osipenko wrote: >>>>>>> 30.04.2020 17:02, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>>>>>> 30.04.2020 16:56, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>>>>>>> 30.04.2020 01:00, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1= =82: >>>>>>>>>> +static int chan_capture_kthread_finish(void *data) >>>>>>>>>> +{ >>>>>>>>>> +=C2=A0=C2=A0=C2=A0 struct tegra_vi_channel *chan =3D data; >>>>>>>>>> +=C2=A0=C2=A0=C2=A0 struct tegra_channel_buffer *buf; >>>>>>>>>> + >>>>>>>>>> +=C2=A0=C2=A0=C2=A0 set_freezable(); >>>>>>>>>> + >>>>>>>>>> +=C2=A0=C2=A0=C2=A0 while (1) { >>>>>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 try_to_freeze(); >>>>>>>>> I guess it won't be great to freeze in the middle of a capture >>>>>>>>> process, so: >>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (list_empty(&chan-= >done)) >>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0 try_to_freeze(); >>>>>>>> And here should be some locking protection in order not race with >>>>>>>> the >>>>>>>> chan_capture_kthread_start because kthread_finish could freeze >>>>>>>> before >>>>>>>> kthread_start. >>>>>>> Or maybe both start / finish threads should simply be allowed to >>>>>>> freeze >>>>>>> only when both capture and done lists are empty. >>>>>>> >>>>>>> if (list_empty(&chan->capture) && >>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0 list_empty(&chan->done)) >>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0try_to_freeze(); >>>>>> good to freeze when not in middle of the frame capture but why >>>>>> should we not allow freeze in between captures? >>>>>> >>>>>> Other drivers do allow freeze in between frame captures. >>>>>> >>>>>> I guess we can freeze before dequeue for capture and in finish >>>>>> thread we can freeze after capture done. This also don't need to >>>>>> check for list_empty with freeze to allow between frame captures. >>>>>> >>>>> Also if we add check for both lists empty, freeze is not allowed as >>>>> long as streaming is going on and in case of continuous streaming >>>>> freeze will never happen. >>> To allow freeze b/w frames (but not in middle of a frame), >>> >>> for capture_start thread, probably we can do unconditional >>> try_to_freeze() > Is it possible to use wait_event_freezable()? > > https://www.kernel.org/doc/Documentation/power/freezing-of-tasks.txt > > Will the wait_event_interruptible() be woken up when system freezes? Based on wait_event_freezable implementation, looks like it similar to=20 wait_event_interruptible + try_to_free() as it does freezable_schedule=20 unlike schedule with wait_event_interruptible. So using this for capture_start may be ok to allow freeze before start=20 of frame. But can't use for capture_finish as this is same as=20 wait_event_interruptible followed by unconditional try_to_freeze. > >>> for capture_finish thread, at end of capture done we can do >>> try_to_freeze() only when done list is empty > This doesn't prevent situation where the done-list is empty and the > "finish" thread freezes, in the same time the "start" thread issues new > capture and then freezes too. > > 1. "start" thread issues capture > > 2. "finish" thread wakes and waits for the capture to complete > > 3. "start" thread begins another capture, waits for FRAME_START > > 4. system freezing activates > > 5. "finish" thread completes the capture and freezes because done-list > is empty > > 6. "start" thread gets FRAME_START, issues another capture and freezes This will not happen as we allow double buffering done list will not be=20 empty till stream stop happens There will always be 1 outstanding frame in done list >> My understanding is buffer updates/release should not happen after >> frozen state. So we should let frame capture of outstanding buffer to >> finish before freezing in capture_finish thread. >> >> But for capture_start thread we can unconditionally freeze before >> dequeuing next buffer for capture. >> >> With this when both threads are in frozen state and no buffer >> updates/captures will happen after frozen state. >> >> I think its not required to finish streaming of all frames completely to >> let threads to enter frozen state as streaming can be continuous as well= . > Yes, only freezing in the middle of IO should be avoided. > > https://lwn.net/Articles/705269/ > >>>> Hi Dmitry, >>>> >>>> Will update in v12 to not allow freeze in middle of a frame capture. >>>> >>>> Can you please confirm on above if you agree to allow freeze to >>>> happen in b/w frame captures? >>>> >>>> Also as most feedback has been received from you by now, appreciate >>>> if you can provide all in this v11 if you have anything else so we >>>> will not have any new changes after v12. > I'll take another look tomorrow / during weekend and let you know.