add_memory() is supposed to be run with device_hotplug_lock grabbed, otherwise
it can race with e.g. device_online(). ACPI memory hotplug does that already
but e.g. Hyper-V ballooning driver doesn't.
Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
mm/memory_hotplug.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 9fab107..41638eb 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1213,7 +1213,11 @@ int zone_for_memory(int nid, u64 start, u64 size, int zone_default)
return zone_default;
}
-/* we are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG */
+/*
+ * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
+ * and online/offline operations before this call.
+ * We are OK calling __meminit stuff here - we have CONFIG_MEMORY_HOTPLUG.
+ */
int __ref add_memory(int nid, u64 start, u64 size)
{
pg_data_t *pgdat = NULL;
--
1.9.3
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