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<12a36c2a-593c-e555-d44e-e2e6c4c1a562@nvidia.com> <5f54c018-5670-8193-7c68-969f9bde92f6@xs4all.nl> From: Sowjanya Komatineni Message-ID: <19081d90-62cc-e6eb-0337-f108fb6ca9bc@nvidia.com> Date: Wed, 18 Mar 2020 09:14:13 -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: <5f54c018-5670-8193-7c68-969f9bde92f6@xs4all.nl> X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1584547890; bh=tIHZbQLtSkJ53RrtKu9vilUV11m0jEsmcYMmUk3NErg=; 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=MkFrRgcrqQAzQJcI2+1Q40+Pr9qGESvro4Iislxt2Izw1pDw9+uxYindJKOuhauPP 9TnHwD3EhYiI9hppup43ZWHvkPwGzWf67CXtKZSkssNgDM3QHbkyRu4XknC4xIkJy7 0VRO3RaUv2p+fnA2Kajs5enDYxis8R1g8z7tPlWDF3k7kRjOE3LkpGyu+5G8+/bdcC ueokh3NujrDWrfILfiHFTGU7F7JTdXIZY/aE/vkbfUQBaLofWMZ6Dbm81SZRzCUkjt LbstXrBXFK4BuI8wySVdDQHWo/JL1vu0Nq7eKTKkHG4j+nzsKG8kZDPLJ05SKHrEMk jVKoZVqhUP0IQ== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 3/18/20 4:48 AM, Hans Verkuil wrote: > External email: Use caution opening links or attachments > > > On 2/24/20 5:45 AM, Sowjanya Komatineni wrote: >> On 2/20/20 11:11 AM, Sowjanya Komatineni wrote: >>> On 2/20/20 5:33 AM, Hans Verkuil wrote: >>>> External email: Use caution opening links or attachments >>>> >>>> >>>> (Replying to myself so I can explain this a bit more) >>>> >>>> On 2/20/20 1:44 PM, Hans Verkuil wrote: >>>>>> + >>>>>> +static int tegra_csi_tpg_channels_alloc(struct tegra_csi *csi) >>>>>> +{ >>>>>> + struct device_node *node = csi->dev->of_node; >>>>>> + unsigned int port_num; >>>>>> + int ret; >>>>>> + struct tegra_csi_channel *item; >>>>>> + unsigned int tpg_channels = csi->soc->csi_max_channels; >>>>>> + >>>>>> + /* allocate CSI channel for each CSI x2 ports */ >>>>>> + for (port_num = 0; port_num < tpg_channels; port_num++) { >>>>>> + item = devm_kzalloc(csi->dev, sizeof(*item), GFP_KERNEL); >>>>> Using devm_*alloc can be dangerous. If someone unbinds the driver, then >>>>> all memory allocated with devm_ is immediately freed. But if an >>>>> application >>>>> still has a filehandle open, then when it closes it it might still >>>>> reference >>>>> this already-freed memory. >>>>> >>>>> I recommend that you avoid using devm_*alloc for media drivers. >>>> A good test is to unbind & bind the driver: >>>> >>>> cd /sys/devices/platform/50000000.host1x/54080000.vi/driver >>>> echo -n 54080000.vi >unbind >>>> echo -n 54080000.vi >bind >>>> >>>> First just do this without the driver being used. That already >>>> gives me 'list_del corruption' kernel messages (list debugging >>>> is turned on in my kernel). >> Will fix in v4 to use kzalloc and also proper release v4l2 to make sure >> unbind/bind works properly. >> >> BTW, tegra vi and csi are registered as clients to host1x video driver. >> >> So, unbind and bind should be done with host1x video driver "tegra-video" >> >> cd /sys/devices/platform/50000000.host1x/tegra-video/driver >> echo -n tegra-video > unbind >> echo -n tegra-video > bind > This still crashes with v4, at least if I am streaming with v4l2-ctl --stream-mmap. > Is that known? > > It's not a big deal at this moment, just want to know if this will be looked > at later. > > Regards, > > Hans Weird, I tested streaming after unbind and bind as well and don't see crash. Did below steps and tried several times unbind/bind as well. ./v4l2-ctl --stream-mmap --stream-count=1 -d /dev/video3 cd /sys/devices/platform/50000000.host1x/tegra-video/driver echo -n tegra-video > unbind sleep 1 echo -n tegra-video > bind cd /home/ubuntu ./v4l2-ctl --stream-mmap --stream-count=1 -d /dev/video3 Can you post call trace when you saw crash? >>>> Note that this first test is basically identical to a rmmod/modprobe >>>> of the driver. But when I compiled the driver as a module it didn't >>>> create any video device nodes! Nor did I see any errors in the kernel >>>> log. I didn't pursue this, and perhaps I did something wrong, but it's >>>> worth taking a look at. >>>> >>>> The next step would be to have a video node open with: >>>> >>>> v4l2-ctl --sleep 10 >>>> >>>> then while it is sleeping unbind the driver and see what happens >>>> when v4l2-ctl exits. >>>> >>>> Worst case is when you are streaming: >>>> >>>> v4l2-ctl --stream-mmap >>>> >>>> and then unbind. >>>> >>>> In general, the best way to get this to work correctly is: >>>> >>>> 1) don't use devm_*alloc >>>> 2) set the release callback of struct v4l2_device and do all freeing >>>> there. >>>> 3) in the platform remove() callback you call media_device_unregister() >>>> and video_unregister_device(). >>> Reg 3, in current patch, media_device_unregister is called in >>> host1x_video_remove >>> video_unregister_device happens during host1x_video_remove -> >>> host1x_device_exit -> tegra_vi_exit -> tegra_vi_channels_cleanup >>> >>>> It's worth getting this right in this early stage, rather than fixing it >>>> in the future. >>>> >>>> Regards, >>>> >>>> Hans