Re: [PATCH v4 1/4] kernel: param: initialize module_kset before do_initcalls()

Shashank Balaji
2026-04-28T00:37:22Z

Hi Gary,

On Mon, Apr 27, 2026 at 02:29:55PM +0100, Gary Guo wrote:
> On Mon Apr 27, 2026 at 3:41 AM BST, Shashank Balaji wrote:
> > module_kset is initialized in param_sysfs_init(), a subsys_initcall. A number
> > of platform drivers register themselves prior to subsys_initcalls
> > (tegra194_cbb_driver registers in a pure_initcall, for example). With an
> > upcoming patch ("driver core: platform: set mod_name in driver registration")
> > that sets their mod_name in struct device_driver, lookup_or_create_module_kobject()
> > will be called for those drivers, which calls kset_find_obj(module_kset, mod_name).
> > This causes a null deref because module_kset isn't alive yet.
> >
> > Fix this by initializing module_kset in do_basic_setup() before do_initcalls().
> > Modernize the pr_warn while we're at it.
> >
> > Suggested-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Suggested-by: Gary Guo <gary@garyguo.net>
>
> I didn't suggest this change :)
>
> I suggested `pure_initcall`, which is just a one line change.

Oops, sorry about the misattribution.

> diff --git a/kernel/params.c b/kernel/params.c
> index 74d620bc2521..ac088d4b09a9 100644
> --- a/kernel/params.c
> +++ b/kernel/params.c
> @@ -957,7 +957,7 @@ static int __init param_sysfs_init(void)
>
> return 0;
> }
> -subsys_initcall(param_sysfs_init);
> +pure_initcall(param_sysfs_init);
>
> /*
> * param_sysfs_builtin_init - add sysfs version and parameter
>
> pure_initcall is level 0 so it happens before all other init calls. Does it not
> work?

tegra194_cbb_driver registers itself in a pure_initcall too. We wouldn't
want the ordering of its registration and module_kset init to be link order
dependent.

Thanks,
Shashank