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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> <289d9c92-383f-3257-de7b-46179724285a@nvidia.com> <9aa64f21-7b23-7228-b5eb-d2ff092682ad@nvidia.com> Message-ID: <668cc4a0-2c81-0d87-b801-9fbf64e19137@nvidia.com> Date: Thu, 30 Apr 2020 15:16:12 -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: <9aa64f21-7b23-7228-b5eb-d2ff092682ad@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=1588284996; bh=tT4tpk5q1LIrhIEUSs8RviCWIdUHSHN2gR4OajypV9g=; 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=XNBkcN7I/kCiLvx4PN/yqzek2LOontcrs6klOTPcT03S6TAi899rSqRK6cCa0XqEw mf123b40dUJoVpTNNfEpghtt3tbst7ko9pTbJPFUZ7pDp4UWrqCRpyGMrPs9atj68I l65eOQu2qxNNtqNoBWQtrz1+CyV0jDo8ZoUEJbtwDuF4Q0W62ISnL6RMyYTh2od4NE vQ/nwaL1K9YKeuV3MImwDFrgPrw5L1bnIhexJUa2ykG7s0Tmo16gPQ8z1DPw4/RmPz Y34KUqS3LDO28RazFh+GvwJVOe0S3tyzqfFpxwSa+TXfZ82S30yZ9AjT1cI81hngwU 0pxe/FUrk8uyg== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/30/20 2:53 PM, Sowjanya Komatineni wrote: > > On 4/30/20 2:37 PM, Sowjanya Komatineni wrote: >> >> 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 dat= a; >>>>>>>>>>>>>>>>> +=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 = (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=C2=A0 try_to_freeze(); >>>>>>>>>>>>>>> And here should be some locking protection in order not=20 >>>>>>>>>>>>>>> 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=20 >>>>>>>>>>>>> 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=20 >>>>>>>>>>>>> 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.t= xt=20 >>>>>>>> >>>>>>>> >>>>>>>> Will the wait_event_interruptible() be woken up when system=20 >>>>>>>> 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=20 >>>>>>>> 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=20 >>>>>>> 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=20 >>>>>> 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. > > Based on my understanding when we mark thread as freezable, > > with wait_event_freezable() - after wait event, it invokes=20 > try_to_freeze(). So frozen state enters unconditionally with this. > > with wait_event_interruptible - we do try_to_freeze when its safe to=20 > enter frozen state. > > https://www.kernel.org/doc/Documentation/power/freezing-of-tasks.txt > Sorry correction. When system tries to freeze tasks looks like it will=20 sending signal to thread and wake up happens when signal is sent to=20 thread and freezable thread should invoke try_to_free when its safe to free > >>> >>>> And in this case synchronization between start/finish threads=20 >>>> 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=20 >> capture start and finished frames by kthread_finish and allow=20 >> kthread_finish to freeze only when captures inflight is 0. >> >> This allows freeze to happen b/w frames but not in middle of frame >> >>