linux-kernel - Re: [PATCH] ACPI / WMI: Call acpi_wmi

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Message-ID: <CAJZ5v0jxVUxFetwPaj76FoeQjHtSSwO+4jiEqadA1WXZ_YNNoQ@mail.gmail.com>
Date:   Sat, 6 Jan 2018 00:30:23 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>
Cc:     Jonathan McDowell <noodles@...th.li>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH] ACPI / WMI: Call acpi_wmi_init() later

On Wed, Jan 3, 2018 at 12:49 PM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Calling acpi_wmi_init() at the subsys_initcall() level causes ordering
> issues to appear on some systems and they are difficult to reproduce,
> because there is no guaranteed ordering between subsys_initcall()
> calls, so they may occur in different orders on different systems.
>
> In particular, commit 86d9f48534e8 (mm/slab: fix kmemcg cache
> creation delayed issue) exposed one of these issues where genl_init()
> and acpi_wmi_init() are both called at the same initcall level, but
> the former must run before the latter so as to avoid a NULL pointer
> dereference.
>
> For this reason, move the acpi_wmi_init() invocation to the
> initcall_sync level which should still be early enough for things
> to work correctly in the WMI land.
>
> Link: https://marc.info/?t=151274596700002&r=1&w=2
> Reported-by: Jonathan McDowell <noodles@...th.li>
> Reported-by: Joonsoo Kim <iamjoonsoo.kim@....com>
> Tested-by: Jonathan McDowell <noodles@...th.li>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Guys, this fixes a crash on boot.

If there are no concerns/objections I will just take it through the ACPI tree.

> ---
>  drivers/platform/x86/wmi.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-pm/drivers/platform/x86/wmi.c
> ===================================================================
> --- linux-pm.orig/drivers/platform/x86/wmi.c
> +++ linux-pm/drivers/platform/x86/wmi.c
> @@ -1458,5 +1458,5 @@ static void __exit acpi_wmi_exit(void)
>         class_unregister(&wmi_bus_class);
>  }
>
> -subsys_initcall(acpi_wmi_init);
> +subsys_initcall_sync(acpi_wmi_init);
>  module_exit(acpi_wmi_exit);
>
> --