The patch titled
Subject: drivers/acpi/scan.c: document why we don't need the device_hotplug_lock
has been added to the -mm tree. Its filename is
drivers-acpi-scanc-document-why-we-dont-need-the-device_hotplug_lock.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/drivers-acpi-scanc-document-why-we-dont-need-the-device_hotplug_lock.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/drivers-acpi-scanc-document-why-we-dont-need-the-device_hotplug_lock.patch
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------------------------------------------------------
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.
Link: http://lkml.kernel.org/r/20190731135306.31524-1-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: 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.
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
drivers-acpi-scanc-document-why-we-dont-need-the-device_hotplug_lock.patch
mm-memory_hotplug-remove-move_pfn_range.patch
drivers-base-nodec-simplify-unregister_memory_block_under_nodes.patch
