From c1c9518331969f97ea403bac66f0fd4a85d204d5 Mon Sep 17 00:00:00 2001 From: Gavin Shan Date: Tue, 31 Jul 2012 16:46:06 -0700 Subject: [PATCH] mm/sparse: remove index_init_lock sparse_index_init() uses the index_init_lock spinlock to protect root mem_section assignment. The lock is not necessary anymore because the function is called only during boot (during paging init which is executed only from a single CPU) and from the hotplug code (by add_memory() via arch_add_memory()) which uses mem_hotplug_mutex. The lock was introduced by 28ae55c9 ("sparsemem extreme: hotplug preparation") and sparse_index_init() was used only during boot at that time. Later when the hotplug code (and add_memory()) was introduced there was no synchronization so it was possible to online more sections from the same root probably (though I am not 100% sure about that). The first synchronization has been added by 6ad696d2 ("mm: allow memory hotplug and hibernation in the same kernel") which was later replaced by the mem_hotplug_mutex - 20d6c96b ("mem-hotplug: introduce {un}lock_memory_hotplug()"). Let's remove the lock as it is not needed and it makes the code more confusing. [mhocko@suse.cz: changelog] Signed-off-by: Gavin Shan Reviewed-by: Michal Hocko Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- Reading git-format-patch failed