From: Sowjanya Komatineni <skomatineni@nvidia.com> To: Hans Verkuil <hverkuil@xs4all.nl>, <thierry.reding@gmail.com>, <jonathanh@nvidia.com>, <frankc@nvidia.com>, <helen.koike@collabora.com>, <sboyd@kernel.org> Cc: <linux-media@vger.kernel.org>, <devicetree@vger.kernel.org>, <linux-clk@vger.kernel.org>, <linux-tegra@vger.kernel.org>, <linux-kernel@vger.kernel.org> Subject: Re: [RFC PATCH v3 4/6] media: tegra: Add Tegra210 Video input driver Date: Wed, 18 Mar 2020 10:17:12 -0700 Message-ID: <a5377068-3c70-1af4-6398-630d205e794b@nvidia.com> (raw) In-Reply-To: <061eabf1-4b6f-83c0-6851-df8a193a84e8@nvidia.com> On 3/18/20 9:25 AM, Sowjanya Komatineni wrote: > > On 3/18/20 9:14 AM, Sowjanya Komatineni wrote: >> >> 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? > > Tried unbind when node is open with v4l2-ctl --sleep 10 as well and > bind back. > > I don't see crash. Will confirm on doing unbind/bind with stream-mmap... > Able to repro when unbind/bind happens while stream-mmap. Will look and have fix in v5. Thanks Hans. >> >>>>>> 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
next prev parent reply index Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-02-14 18:23 [RFC PATCH v3 0/6] Add Tegra driver for video capture Sowjanya Komatineni 2020-02-14 18:23 ` [RFC PATCH v3 1/6] dt-bindings: clock: tegra: Add clk id for CSI TPG clock Sowjanya Komatineni 2020-02-14 18:23 ` [RFC PATCH v3 2/6] clk: tegra: Add Tegra210 CSI TPG clock gate Sowjanya Komatineni 2020-02-14 18:23 ` [RFC PATCH v3 3/6] dt-binding: tegra: Add VI and CSI bindings Sowjanya Komatineni 2020-02-18 23:15 ` Rob Herring 2020-02-19 3:28 ` Sowjanya Komatineni 2020-02-20 19:45 ` Rob Herring 2020-02-20 20:39 ` Sowjanya Komatineni 2020-02-14 18:23 ` [RFC PATCH v3 4/6] media: tegra: Add Tegra210 Video input driver Sowjanya Komatineni 2020-02-16 11:03 ` Hans Verkuil 2020-02-16 19:54 ` Sowjanya Komatineni 2020-02-16 20:11 ` Sowjanya Komatineni 2020-02-16 20:22 ` Sowjanya Komatineni 2020-02-17 8:04 ` Hans Verkuil 2020-02-18 0:59 ` Sowjanya Komatineni 2020-02-18 1:04 ` Sowjanya Komatineni 2020-02-18 3:19 ` Sowjanya Komatineni 2020-02-19 15:08 ` Hans Verkuil 2020-02-19 16:22 ` Sowjanya Komatineni 2020-02-20 0:09 ` Sowjanya Komatineni 2020-02-20 9:29 ` Hans Verkuil 2020-02-20 16:21 ` Sowjanya Komatineni 2020-02-20 12:44 ` Hans Verkuil 2020-02-20 13:33 ` Hans Verkuil 2020-02-20 17:29 ` Sowjanya Komatineni 2020-02-20 19:11 ` Sowjanya Komatineni 2020-02-24 4:45 ` Sowjanya Komatineni 2020-03-18 11:48 ` Hans Verkuil 2020-03-18 16:14 ` Sowjanya Komatineni 2020-03-18 16:25 ` Sowjanya Komatineni 2020-03-18 17:17 ` Sowjanya Komatineni [this message] 2020-03-19 14:29 ` Hans Verkuil 2020-03-19 18:49 ` Sowjanya Komatineni 2020-02-26 4:49 ` Sowjanya Komatineni 2020-02-26 5:50 ` Sowjanya Komatineni 2020-02-14 18:23 ` [RFC PATCH v3 5/6] MAINTAINERS: Add Tegra Video driver section Sowjanya Komatineni 2020-02-14 18:23 ` [RFC PATCH v3 6/6] arm64: tegra: Add Tegra VI CSI support in device tree Sowjanya Komatineni 2020-02-17 14:26 ` [RFC PATCH v3 0/6] Add Tegra driver for video capture Hans Verkuil
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