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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> <668d9b65-9590-cc97-41c3-2c1a5cfbbe61@nvidia.com> Message-ID: <289d9c92-383f-3257-de7b-46179724285a@nvidia.com> Date: Thu, 30 Apr 2020 14:37:00 -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: <668d9b65-9590-cc97-41c3-2c1a5cfbbe61@nvidia.com> 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=1588282644; bh=hookx+pyYqTHGImeQX3FFZEfY65VPxDRIYlWFYqHMWQ=; 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=nMUJp0KKq8J5b8+r2/CpGELtyX2yHzwoh6c1qPomTI4DmZyYuo77qa2Qftz2UW4un y377YQRZOcI0Mp1m2rly/d66pEhLNLujMuNHw4SmYx/HT2oJWT/3hN6Q0W3dhLwT2V IvEMH8xWkhITS1r42gd0p9c5IWQdo26ZW1Pdg6WVBc91f2u8uNnQ9dkESLwdMzM6AA D2GQV1Yoi1APmrzvcO4jjfkNgaLSRnYPB2NMrdTE1cDT+Jj64Az3mPi9DmMbche+RI hiCGuLffsbTFtxRZHllXBnl2AREHxvYg9gIs1NOpV18lD8Im+1CDX45kWFzm0VpnQc dUVF1JdoefQtg== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/30/20 2:26 PM, Sowjanya Komatineni wrote: > > 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=20 >>>>>>>>>>>>>> capture >>>>>>>>>>>>>> process, so: >>>>>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 if (l= ist_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=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=20 >>>>>>>>>>>>> freeze >>>>>>>>>>>>> before >>>>>>>>>>>>> kthread_start. >>>>>>>>>>>> Or maybe both start / finish threads should simply be=20 >>>>>>>>>>>> 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=C2=A0 list_empty(&chan->done)) >>>>>>>>>>>> =C2=A0=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=20 >>>>>>>>>>> need to >>>>>>>>>>> check for list_empty with freeze to allow between frame=20 >>>>>>>>>>> captures. >>>>>>>>>>> >>>>>>>>>> Also if we add check for both lists empty, freeze is not=20 >>>>>>>>>> allowed as >>>>>>>>>> long as streaming is going on and in case of continuous=20 >>>>>>>>>> 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=20 >>>>>> 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=20 >>>>>> done-list >>>>>> is empty >>>>>> >>>>>> 6. "start" thread gets FRAME_START, issues another capture and=20 >>>>>> freezes >>>>> 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=20 >>> 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=20 > meant 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=20 > wait_event_interruptible 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=20 > progress > >> Note that this could be a wrong assumption, I'm not closely familiar >> with how freezer works. kthread_start can unconditionally allow try_to_freeze before start of=20 frame capture We can compute captures inflight w.r.t single shot issued during capture=20 start and finished frames by kthread_finish and allow kthread_finish to=20 freeze only when captures inflight is 0. This allows freeze to happen b/w frames but not in middle of frame