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<492dafac-42aa-3caf-4d32-ba0e434b19c3@gmail.com> From: Sowjanya Komatineni Message-ID: <39402a49-f39f-256c-31e7-afaa25d55664@nvidia.com> Date: Thu, 23 Apr 2020 17:51:47 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <492dafac-42aa-3caf-4d32-ba0e434b19c3@gmail.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=1587689498; bh=GqevmKFeruTWerk0fVnbYo2UecOfTyPj1DGoVK9JAfM=; 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=lH4nj+WYYCRcuwprODPNnVi9lgpM+R7mnlqKWtU3Z0FzAJ/FkWZReXMDT6q/7s5Hc ctc2GHlC53N70o84nvfNVF0w5+8Rbyg4TJeR9iZ7aqLrcsZaP1VtRgaPETfFgpyG+k WZPVz79yFBVUvd3qenZsKTpxUd0Ql6T4/XJ2JZDjVk/4NpbUoXn0VHp498hWQua47z rdRWbbQSgz58VZ/gHX7QdyyDBg/Zx3yuwIOLueN9S6YtJjgaP1l9Q0eQHjDRLnd7iO f45KQe4oWJiLtwoFDiZRJO8yX0VJH4JicPySCguzTkOzb2GsW5j81Oo5qlrzkOCmKD Vw2JnNAoDjmVw== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/23/20 5:42 PM, Dmitry Osipenko wrote: > External email: Use caution opening links or attachments > > > 24.04.2020 02:50, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >> On 4/23/20 4:25 PM, Dmitry Osipenko wrote: >>> External email: Use caution opening links or attachments >>> >>> >>> 24.04.2020 02:20, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>> On 4/23/20 4:19 PM, Sowjanya Komatineni wrote: >>>>> On 4/23/20 4:16 PM, Dmitry Osipenko wrote: >>>>>> External email: Use caution opening links or attachments >>>>>> >>>>>> >>>>>> 22.04.2020 09:18, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82= : >>>>>>> +static int chan_capture_kthread_start(void *data) >>>>>>> +{ >>>>>>> + struct tegra_vi_channel *chan =3D data; >>>>>>> + struct tegra_channel_buffer *buf; >>>>>>> + int err =3D 0; >>>>>>> + >>>>>>> + set_freezable(); >>>>>>> + >>>>>>> + while (1) { >>>>>>> + try_to_freeze(); >>>>>>> + >>>>>>> + wait_event_interruptible(chan->start_wait, >>>>>>> + !list_empty(&chan->capture) || >>>>>>> + kthread_should_stop()); >>>>>>> + >>>>>>> + if (kthread_should_stop()) >>>>>>> + break; >>>>>>> + >>>>>>> + /* >>>>>>> + * Source is not streaming if error is non-zero. >>>>>>> + * So, do not dequeue buffers on capture error. >>>>>>> + */ >>>>>>> + if (err) >>>>>>> + continue; >>>>>> This will result in an endless loop, I suppose it wasn't the >>>>>> intention. >>>>> no it will not. on error we report vb2_queue_error which will do >>>>> streaming stop request. >>>>> >>>>> So thread will be stopped on streaming stop request thru kthread stop >>>>> signal >>>> To be clear on error it reports vb2 queue error and waits for stop >>>> streaming to happen >>> If thread should exit on error, then it should do it on the actual >>> error. Otherwise it looks very error-prone. >> When v4l2 drivers indicate fatal error through vb2_queue_error, queue >> error flag is set and wakes up all processes waiting on queue along >> with polling reporting EPOLLERR and also reporting error for queuing >> and dequeuing buffers. Stream stop will surely happen which stops the >> thread. > This doesn't explain what is the point of continuing to loop instead of > exiting immediately on error. We are using 2 threads and when capture start error happens, we can stop=20 capture_start thread immediately but capture_finish thread will still=20 run for any outstanding buffers. So, as it makes no diff stopping both threads during stream stop which=20 will definitely happen on error and when we don't dequeue buffers