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=-2.4 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,URIBL_BLOCKED,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 EF761C47247 for ; Thu, 30 Apr 2020 19:54:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CABBD20731 for ; Thu, 30 Apr 2020 19:54:57 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=nvidia.com header.i=@nvidia.com header.b="r5+Ev1Uh" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726905AbgD3Ty5 (ORCPT ); Thu, 30 Apr 2020 15:54:57 -0400 Received: from hqnvemgate25.nvidia.com ([216.228.121.64]:10214 "EHLO hqnvemgate25.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726272AbgD3Ty4 (ORCPT ); Thu, 30 Apr 2020 15:54:56 -0400 Received: from hqpgpgate102.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 30 Apr 2020 12:53:48 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate102.nvidia.com (PGP Universal service); Thu, 30 Apr 2020 12:54:56 -0700 X-PGP-Universal: processed; by hqpgpgate102.nvidia.com on Thu, 30 Apr 2020 12:54:56 -0700 Received: from DRHQMAIL107.nvidia.com (10.27.9.16) by HQMAIL111.nvidia.com (172.20.187.18) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Thu, 30 Apr 2020 19:54:55 +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 19:54:54 +0000 Subject: Re: [RFC PATCH v11 6/9] media: tegra: Add Tegra210 Video input driver From: Sowjanya Komatineni 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> Message-ID: <298187f6-2425-4813-1ae1-f256c179623e@nvidia.com> Date: Thu, 30 Apr 2020 12:53:26 -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: 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=1588276429; bh=iLEsNONYtUM83I/6rf3F7v6izbOK0RTRNROBYHEGAAQ=; 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=r5+Ev1UhHhPKTT6YLWXAlcCSn/0IBWM6ybo5P01BmkDfIEGWufH9uGnK2uJVsd5KJ fDr0eUn0qOJN/Ch9HhHKs5sq/Xw9AlNlR8G5KwufehiZz3hRALEdzYmgQnkgTW5y35 A3COQbAn3OLbRmevjUAMeqxGvLwaxsbRzHK9X/itKwqZ7IH2PJ8B4xYP01pLCQK2IV v6kq+gnXR5sXdVz4kfAvVl7u+8p1ELXEmKgYuWhUQzayvTD0Bk0jgL2Rk9FVrEAAsz fUbwcJzFavjUgNbKtmHEo+GQxAyVpVa2eBuEd62+O3YTX2x0KOSdezcXtmNTmdC3ua Tq5roq9RTNi5Q== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/30/20 12:46 PM, Sowjanya Komatineni wrote: > > 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=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=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=C2=A0 list_empty(&chan->done)) >>>>>>>> =C2=A0=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=20 > be empty till stream stop happens > > There will always be 1 outstanding frame in done list Correction, there will always be 1 outstanding buffer except beginning=20 during beginning of stream. Except during beginning frames, done list will not be empty for all=20 subsequent streaming process > >>> 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=20 >>> completely to >>> let threads to enter frozen state as streaming can be continuous as=20 >>> 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.