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

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Message-ID: <20180106110227.j2jkxjpjktcy6yjr@earth.li>
Date:   Sat, 6 Jan 2018 11:02:27 +0000
From:   Jonathan McDowell <noodles@...th.li>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>,
        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 Sat, Jan 06, 2018 at 12:30:23AM +0100, Rafael J. Wysocki wrote:
> 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.

Note that I first started seeing it in v4.9 so would ideally hit the
appropriate stable trees too.

> > ---
> >  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);
> >
> > --

J.

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