Messages in this thread | | | Subject | Re: [RFC PATCH v3 4/6] media: tegra: Add Tegra210 Video input driver | From | Sowjanya Komatineni <> | Date | Wed, 18 Mar 2020 09:25:12 -0700 |
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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...
> >>>>> 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
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