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 10:47:50 -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> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <6afa951e-d904-f3c0-053f-82a02fb18979-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Content-Language: en-US Sender: linux-tegra-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 10:21 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_drvda= ta(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->clien= t); >>>> +=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 unregister h= ost1x 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. Could=20 >>> you >>> please explain in a more details? >>> >>> Have you tried to test this driver under KASAN? I suspect that you 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 opened=20 >> then unloading module will not happen and module refcnt is also=20 >> non-zero and unloading tegra-video module reports module in use. >> >> 2. during tegra-video driver unbind, tegra-video driver removal will=20 >> do vi/csi clients exit ops which unregisters video device allocated=20 >> memory during release callback of v4l2 device. vi/csi structure=20 >> allocation remains same as vi/csi driver removal will not happen in=20 >> 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 unregistered=20 >> during direct client driver unbind prior to freeing vi/csi memory. >> >> Also vi/csi driver remove does explicit free vi/csi as its allocated=20 >> with kzalloc. So not sure how using kzalloc is different to=20 >> devm_kzalloc for vi/csi structure in terms of when vi/csi memory gets=20 >> 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 for=20 > specified time and if direct vi client driver unbind happens then vi=20 > driver remove() will free vi memory before v4l2 device release happens. > > But I don't see any crash or errors with this case. > > Also if we allow direct client driver unbind, then vi structure memory=20 > 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 immediate=20 > and we cant free vi that early. typo fix: But we can't free vi structure memory allocation in v4l2 device release=20 callback as in case when device node is not kept opened, device release=20 happens immediate and we can't free vi structure memory that early. > > Hans/Thierry, Can you please comment on this case? > > Thanks > > Sowjanya >