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

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Date:   Wed, 03 Jan 2018 12:49:29 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Darren Hart <dvhart@...radead.org>
Cc:     Jonathan McDowell <noodles@...th.li>, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        platform-driver-x86@...r.kernel.org,
        Andy Lutomirski <luto@...capital.net>
Subject: [PATCH] ACPI / WMI: Call acpi_wmi_init() later

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>
---
 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);