[PATCH v1] ACPI / scan: Acquire device_hotplug_lock in acpi_scan_init()

[David Hildenbrand]

We end up calling __add_memory() without the device hotplug lock held.
(I used a local patch to assert in __add_memory() that the
 device_hotplug_lock is held - I might upstream that as well soon)

[   26.771684]        create_memory_block_devices+0xa4/0x140
[   26.772952]        add_memory_resource+0xde/0x200
[   26.773987]        __add_memory+0x6e/0xa0
[   26.775161]        acpi_memory_device_add+0x149/0x2b0
[   26.776263]        acpi_bus_attach+0xf1/0x1f0
[   26.777247]        acpi_bus_attach+0x66/0x1f0
[   26.778268]        acpi_bus_attach+0x66/0x1f0
[   26.779073]        acpi_bus_attach+0x66/0x1f0
[   26.780143]        acpi_bus_scan+0x3e/0x90
[   26.780844]        acpi_scan_init+0x109/0x257
[   26.781638]        acpi_init+0x2ab/0x30d
[   26.782248]        do_one_initcall+0x58/0x2cf
[   26.783181]        kernel_init_freeable+0x1bd/0x247
[   26.784345]        kernel_init+0x5/0xf1
[   26.785314]        ret_from_fork+0x3a/0x50

So perform the locking just like in acpi_device_hotplug().

Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
---
 drivers/acpi/scan.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 0e28270b0fd8..cbc9d64b48dd 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -2204,7 +2204,9 @@ int __init acpi_scan_init(void)
 	acpi_gpe_apply_masked_gpes();
 	acpi_update_all_gpes();
 
+	lock_device_hotplug();
 	mutex_lock(&acpi_scan_lock);
+
 	/*
 	 * Enumerate devices in the ACPI namespace.
 	 */
@@ -2232,6 +2234,7 @@ int __init acpi_scan_init(void)
 
  out:
 	mutex_unlock(&acpi_scan_lock);
+	unlock_device_hotplug();
 	return result;
 }
 
-- 
2.21.0