commit 98b8e4e5c17bf87c1b18ed929472051dab39878c upstream Please apply to 4.9.x and later stable kernel trees (this is as far back as 86d9f48534e8 was applied). This submission should have followed Option 1, but I failed to Cc: stable in the original commit.
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@earth.li Reported-by: Joonsoo Kim iamjoonsoo.kim@lge.com Tested-by: Jonathan McDowell noodles@earth.li Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Darren Hart (VMware) dvhart@infradead.org --- drivers/platform/x86/wmi.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c index 791449a..daa68ac 100644 --- a/drivers/platform/x86/wmi.c +++ b/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);