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<492dafac-42aa-3caf-4d32-ba0e434b19c3@gmail.com> <39402a49-f39f-256c-31e7-afaa25d55664@nvidia.com> Message-ID: <8f01724e-95d4-e6d8-9e2d-bce4b8dd0177@nvidia.com> Date: Thu, 23 Apr 2020 18:08:27 -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: <39402a49-f39f-256c-31e7-afaa25d55664@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=1587690392; bh=0VcoRgXJ0ZnT5wCxcL+1oZjS8xuQ825bdiGOnGN6ldI=; 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=KmrFXbTCpgHZzv0NUHaUfJjgUNF+0du/q8tLCI0Nu3o44g8QCH0DVWNGTie17IZC2 gajOyou6UNclIWBlJYhCTpwvpEVeibc4EtQ1IZm/Wua+r/qQZGDaZ92KnyUugqbCFB qcpzhn0uoMW6fT0FYcVGipG1WoOu8KOhE7QkltxI9wJi3ynkD5SmSNQmhM8uJjgHLv dzX+H3rmEHPBTFWf4kiswfWAkx47BpgPH+K+XdcUtvalBwEglpx9sQj2szf8xdfCNw J7W4PVy83N1FNXByAPPJI62nUVR5Au9+tFUo1QtUX5Z58WsGiXVIVUryPodVGZ+ZQM qsBPB2SEp79AQ== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/23/20 5:51 PM, Sowjanya Komatineni wrote: > > 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) >>>>>>>> +{ >>>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 struct tegra_vi_channel *chan =3D data; >>>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 struct tegra_channel_buffer *buf; >>>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 int err =3D 0; >>>>>>>> + >>>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 set_freezable(); >>>>>>>> + >>>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 while (1) { >>>>>>>> +=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(); >>>>>>>> + >>>>>>>> + wait_event_interruptible(chan->start_wait, >>>>>>>> + !list_empty(&chan->capture) || >>>>>>>> + kthread_should_stop()); >>>>>>>> + >>>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 if (kthread_should_stop()) >>>>>>>> +=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=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 break; >>>>>>>> + >>>>>>>> +=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=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0=C2=A0 * Source is not streaming if error is non-zero. >>>>>>>> +=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 * So, do not dequeue buffers on capture error. >>>>>>>> +=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 */ >>>>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0=C2=A0 if (err) >>>>>>>> +=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=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 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=20 >>>>>> 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=C2=A0 is set and wakes up all processes waiting on queue alo= ng >>> with polling reporting=C2=A0 EPOLLERR and also reporting error for queu= ing >>> 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=20 > stop capture_start thread immediately but capture_finish thread will=20 > still 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 > Also there will be an issue if we break on error immediately during=20 stop_streaming -> kthread_stop() As stop streaming can happen any time, we do kthread_stop and in case of=20 error if we stop thread and on stop streaming kthread_stop might crash=20 as kthread_stop can only be called on running thread