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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 by28ae55c9
("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 by6ad696d2
("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 <shangw@linux.vnet.ibm.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Cc: Michal Hocko <mhocko@suse.cz> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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parent
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1 changed files with 1 additions and 13 deletions
14
mm/sparse.c
14
mm/sparse.c
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@ -77,7 +77,6 @@ static struct mem_section noinline __init_refok *sparse_index_alloc(int nid)
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static int __meminit sparse_index_init(unsigned long section_nr, int nid)
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{
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static DEFINE_SPINLOCK(index_init_lock);
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unsigned long root = SECTION_NR_TO_ROOT(section_nr);
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struct mem_section *section;
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int ret = 0;
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@ -88,20 +87,9 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
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section = sparse_index_alloc(nid);
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if (!section)
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return -ENOMEM;
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/*
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* This lock keeps two different sections from
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* reallocating for the same index
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*/
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spin_lock(&index_init_lock);
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if (mem_section[root]) {
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ret = -EEXIST;
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goto out;
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}
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mem_section[root] = section;
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out:
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spin_unlock(&index_init_lock);
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return ret;
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}
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#else /* !SPARSEMEM_EXTREME */
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