On 4/15/20 9:54 AM, Sowjanya Komatineni wrote:
On 4/15/20 7:22 AM, Dmitry Osipenko wrote:
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15.04.2020 05:57, Sowjanya Komatineni пишет:
+static int tegra_csi_remove(struct platform_device *pdev)
+{
+ struct tegra_csi *csi = platform_get_drvdata(pdev);
+ int err;
+
+ err = host1x_client_unregister(&csi->client);
+ if (err < 0) {
+ dev_err(csi->dev,
+ "failed to unregister host1x client: %d\n", err);
+ return err;
+ }
+
+ pm_runtime_disable(csi->dev);
+ 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 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
request to switch to use kzalloc all over this driver.
Hi Hans,
video devices lifetime is till video device nodes are released. So,
v4l2 device release callback does the release of tegra channel
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
which is the case when any of video device node handle is kept opened
then unloading module will not happen and module refcnt is also
non-zero and unloading tegra-video module reports module in use.
2. during tegra-video driver unbind, tegra-video driver removal will
do vi/csi clients exit ops which unregisters video device allocated
memory during release callback of v4l2 device. vi/csi structure
allocation remains same as vi/csi driver removal will not happen in
this case.
3. during direct host1x client drivers vi/csi unbind, both
host1x_clients vi/csi gets unregistered, deletes host1x logical device
which executes tegra-video driver removal() -> vi/csi exit() before
vi/csi memory gets freed in vi/csi driver remove().
So, any active streaming will stop and video devices are unregistered
during direct client driver unbind prior to freeing vi/csi memory.
Also vi/csi driver remove does explicit free vi/csi as its allocated
with kzalloc. So not sure how using kzalloc is different to
devm_kzalloc for vi/csi structure in terms of when vi/csi memory gets
freed?
Except for channel allocation which holds video device and as video
device life time is beyond tegra-video module unbind->vi exit(), looks
like we can use devm_kzalloc for vi/csi.
Can you please comment if you still think we need to use kzalloc
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
sleep (rather than streaming), where it will keep device node open for
specified time and if direct vi client driver unbind happens then vi
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
lifetime should also be till v4l2 device release happens.
But we can free vi in v4l2 device release callback as in case when
device node is not kept opened, video device release happens immediate
and we cant free vi that early.
Hans/Thierry, Can you please comment on this case?
Thanks
Sowjanya
