From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sowjanya Komatineni Subject: Re: [RFC PATCH v7 6/9] media: tegra: Add Tegra210 Video input driver Date: Wed, 15 Apr 2020 11:39:44 -0700 Message-ID: References: <1586919463-30542-1-git-send-email-skomatineni@nvidia.com> <1586919463-30542-7-git-send-email-skomatineni@nvidia.com> <4118112f-f865-5460-6319-d71271fd78d1@gmail.com> <6afa951e-d904-f3c0-053f-82a02fb18979@nvidia.com> <5954a7e1-910e-7f48-56d3-e671b56ead74@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <5954a7e1-910e-7f48-56d3-e671b56ead74-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Content-Language: en-US Sender: devicetree-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Dmitry Osipenko , thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, jonathanh-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, frankc-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org, hverkuil-qWit8jRvyhVmR6Xm/wNWPw@public.gmane.org, sakari.ailus-X3B1VOXEql0@public.gmane.org, helen.koike-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org Cc: sboyd-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, linux-media-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-clk-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-tegra@vger.kernel.org On 4/15/20 10:48 AM, Sowjanya Komatineni wrote: > > On 4/15/20 10:47 AM, Sowjanya Komatineni wrote: >> >> On 4/15/20 10:21 AM, Sowjanya Komatineni wrote: >>> >>> On 4/15/20 9:54 AM, Sowjanya Komatineni wrote: >>>> >>>> On 4/15/20 7:22 AM, Dmitry Osipenko wrote: >>>>> External email: Use caution opening links or attachments >>>>> >>>>> >>>>> 15.04.2020 05:57, Sowjanya Komatineni =D0=BF=D0=B8=D1=88=D0=B5=D1=82: >>>>>> +static int tegra_csi_remove(struct platform_device *pdev) >>>>>> +{ >>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 struct tegra_csi *csi =3D platform_get_drv= data(pdev); >>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 int err; >>>>>> + >>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 err =3D host1x_client_unregister(&csi->cli= ent); >>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 if (err < 0) { >>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0= =C2=A0 dev_err(csi->dev, >>>>>> +=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 "failed to unregiste= r host1x client: %d\n",=20 >>>>>> 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 return err; >>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 } >>>>>> + >>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 pm_runtime_disable(csi->dev); >>>>>> +=C2=A0=C2=A0=C2=A0=C2=A0 kfree(csi); >>>>> IIRC, the driver removal is invoked on the unbinding. Hence, I'm not >>>>> sure how moving away from the resource-managed API helps here.=20 >>>>> Could you >>>>> please explain in a more details? >>>>> >>>>> Have you tried to test this driver under KASAN? I suspect that you=20 >>>>> just >>>>> masked the problem, instead of fixing it. >>>> Using devm_kzalloc for vi/csi structures based on prior feedback=20 >>>> request to switch to use kzalloc all over this driver. >>>> >>>> Hi Hans, >>>> >>>> video devices lifetime is till video device nodes are released. So,=20 >>>> v4l2 device release callback does the release of tegra channel=20 >>>> allocation which hold video device. >>>> >>>> Below are the 3 possible cases of unbind/unload, >>>> >>>> 1. during tegra-video module unload, if v4l2 device refcnt is not 0=20 >>>> which is the case when any of video device node handle is kept=20 >>>> opened then unloading module will not happen and module refcnt is=20 >>>> also non-zero and unloading tegra-video module reports module in use. v4l2 device is associated with host1x device where during=20 v4l2_device_register get_device causes refcnt of tegra video host1x=20 device to increase and prevents allowing module unload/load till v4l2=20 device release happens. >>>> 2. during tegra-video driver unbind, tegra-video driver removal=20 >>>> will do vi/csi clients exit ops which unregisters video device=20 >>>> allocated memory during release callback of v4l2 device. vi/csi=20 >>>> structure allocation remains same as vi/csi driver removal will not=20 >>>> happen in this case. >>>> >>>> >>>> 3. during direct host1x client drivers vi/csi unbind, both=20 >>>> host1x_clients vi/csi gets unregistered, deletes host1x logical=20 >>>> device which executes tegra-video driver removal() -> vi/csi exit()=20 >>>> before vi/csi memory gets freed in vi/csi driver remove(). >>>> >>>> So, any active streaming will stop and video devices are=20 >>>> unregistered during direct client driver unbind prior to freeing=20 >>>> vi/csi memory. >>>> >>>> Also vi/csi driver remove does explicit free vi/csi as its=20 >>>> allocated with kzalloc. So not sure how using kzalloc is different=20 >>>> to devm_kzalloc for vi/csi structure in terms of when vi/csi memory=20 >>>> gets freed? >>>> >>>> Except for channel allocation which holds video device and as video=20 >>>> device life time is beyond tegra-video module unbind->vi exit(),=20 >>>> looks like we can use devm_kzalloc for vi/csi. >>>> >>>> >>>> Can you please comment if you still think we need to use kzalloc=20 >>>> rather than devm_kzalloc for vi/csi structure allocation? >>>> >>>> Thanks >>>> >>>> Sowjanya >>>> >>> One more case is when video device node is kept opened with v4l2-ctl=20 >>> sleep (rather than streaming), where it will keep device node open=20 >>> for specified time and if direct vi client driver unbind happens=20 >>> then vi driver remove() will free vi memory before v4l2 device=20 >>> release happens. >>> >>> But I don't see any crash or errors with this case. In the above case, channels allocated memory release may not happen in=20 this case as list head pointer will be gone when vi memory is freed=20 during direct client unbind and by the time v4l2 device release callback=20 gets executed vi channels list head is gone. Also, freeing vi structure memory can't be done in v4l2 device release=20 callback either. >>> >>> Also if we allow direct client driver unbind, then vi structure=20 >>> memory lifetime should also be till v4l2 device release happens. >>> >>> But we can free vi in v4l2 device release callback as in case when=20 >>> device node is not kept opened, video device release happens=20 >>> immediate and we cant free vi that early. >> >> typo fix: >> >> But we can't free vi structure memory allocation in v4l2 device=20 >> release callback as in case when device node is not kept opened,=20 >> device release happens immediate and we can't free vi structure=20 >> memory that early. >> >>> Hans/Thierry, Can you please comment on this case? >>> >>> Thanks >>> >>> Sowjanya >>> > Also, Can you please help explain on cases where we do/need direct=20 > host1x clients vi/csi drivers unbind?