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<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> <298187f6-2425-4813-1ae1-f256c179623e@nvidia.com> <9c942bc9-703e-3bbb-eeab-f37e69dc1ded@nvidia.com> From: Sowjanya Komatineni Message-ID: <668d9b65-9590-cc97-41c3-2c1a5cfbbe61@nvidia.com> Date: Thu, 30 Apr 2020 14:26:24 -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: HQMAIL111.nvidia.com (172.20.187.18) 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=1588281950; bh=lpBGNwJvTkc5gVc4U4e3ZhvJwZ442wb8jxxt/PKOJjI=; 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=kdPUajXkcbvh83WcWp4xtMN/9JAG7Mp8YHms1KxacY1yzRSXF5p9YpCvVwGTXC0BT RWZ4RS4wqheLuwkmWo5zAUDVo86E6w1OGM2EzSSi5ADlRvxXxz175P4fO8AjUzy0vI 10tCJkIUOIo/adWjMczp/bntda1OC/sos0L5cGXkAWaKjdwGLQqCWh9hsjqnabkGb7 4z3jHQtU6NZqcY6YHEqSGC9KfUFKxp73AOj9WWpgIgk6WnDnAzFCsAyIb7md3Wvg3B fi5cmUBK2r86D/Y0tcrphBG2s91hxR+QQKXyl7lSVlJiEZQDlCAsCO5lIsMKhBVTq1 MwklDsee5SGDA== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/30/20 2:17 PM, Dmitry Osipenko wrote: > 30.04.2020 23:02, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> On 4/30/20 12:53 PM, Sowjanya Komatineni wrote: >>> 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 captur= e >>>>>>>>>>>>> process, so: >>>>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (list_em= pty(&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 t= o >>>>>>>>>>> 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 wait_event_interruptible + try_to_free() as it does >>>> freezable_schedule unlike schedule with wait_event_interruptible. >>>> >>>> So using this for capture_start may be ok to allow freeze before >>>> start of frame. But can't use for capture_finish as this is same as >>>> 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 n= ew >>>>> 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-lis= t >>>>> is empty >>>>> >>>>> 6. "start" thread gets FRAME_START, issues another capture and freeze= s >>>> This will not happen as we allow double buffering done list will not >>>> 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 >>> during beginning of stream. >>> >>> Except during beginning frames, done list will not be empty for all >>> subsequent streaming process >> Also to be clear, hardware sees next frame start event prior to previous >> frame mw_ack event as mw_ack event happens after frame end. So once >> initial buffer got queued to done list to finish processes, while >> waiting for mw_ack next frame start happens and pushes next buffer to >> done list. > What about this variant: > > 1. "start" thread wakes up to start capture > > 2. system freezing activates > > 3. "finish" thread wakes up and freezes finish thread will wake up only when done list is not=20 empty/kthread_stop/wake even from capture start thread. Also when I said will allow try_to_free when done list is empty I meant=20 to have this at end of capture_done() in finish thread > > 4. "start" thread issues capture and freezes > > And again, I assume that system's freezing should wake > wait_event_interruptible(), otherwise it won't be possible to freeze > idling threads at all and freezing should fail (IIUC). Based on kernel doc on freezing, looks like when we mark thread as=20 freezable, freeze state happens when we explicitly call try_to_freeze. I don't think its other way where freeze causes wait_event_interruptible=20 to wake up. > And in this case synchronization between start/finish threads should be > needed in regards to freezing. Was thinking to have counter to track outstanding frame w.r.t single=20 shot issue b/w start and finish and allow to freeze only when no=20 outstanding frames in process. This will make sure freeze will not happen when any buffers are in progress > Note that this could be a wrong assumption, I'm not closely familiar > with how freezer works.