From: David Hildenbrand <david@xxxxxxxxxx> Subject: drivers/acpi/scan.c: document why we don't need the device_hotplug_lock Let's document why the lock is not needed in acpi_scan_init(), right now this is not really obvious. [akpm@xxxxxxxxxxxxxxxxxxxx: fix tpyo] Link: http://lkml.kernel.org/r/20190731135306.31524-1-david@xxxxxxxxxx Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> Cc: Oscar Salvador <osalvador@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/acpi/scan.c | 6 ++++++ 1 file changed, 6 insertions(+) --- a/drivers/acpi/scan.c~drivers-acpi-scanc-document-why-we-dont-need-the-device_hotplug_lock +++ a/drivers/acpi/scan.c @@ -2204,6 +2204,12 @@ int __init acpi_scan_init(void) acpi_gpe_apply_masked_gpes(); acpi_update_all_gpes(); + /* + * Although we call __add_memory() that is documented to require the + * device_hotplug_lock, it is not necessary here because this is an + * early code when userspace or any other code path cannot trigger + * hotplug/hotunplug operations. + */ mutex_lock(&acpi_scan_lock); /* * Enumerate devices in the ACPI namespace. _
