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authorGavin Shan <shangw@linux.vnet.ibm.com>2012-07-31 16:46:06 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-07-31 18:42:49 -0700
commitc1c9518331969f97ea403bac66f0fd4a85d204d5 (patch)
tree9a3122ec4600b94784e86a99aec61a1e93a27da5 /mm/sparse.c
parentdb36a46113e101a8aa2d6ede41e78f2eaabed3f1 (diff)
downloadlinux-c1c9518331969f97ea403bac66f0fd4a85d204d5.tar.gz
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 <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>
Diffstat (limited to 'mm/sparse.c')
-rw-r--r--mm/sparse.c14
1 files changed, 1 insertions, 13 deletions
diff --git a/mm/sparse.c b/mm/sparse.c
index 42ca0ea9af1..fac95f2888f 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -77,7 +77,6 @@ static struct mem_section noinline __init_refok *sparse_index_alloc(int nid)
static int __meminit sparse_index_init(unsigned long section_nr, int nid)
{
- static DEFINE_SPINLOCK(index_init_lock);
unsigned long root = SECTION_NR_TO_ROOT(section_nr);
struct mem_section *section;
int ret = 0;
@@ -88,20 +87,9 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
section = sparse_index_alloc(nid);
if (!section)
return -ENOMEM;
- /*
- * This lock keeps two different sections from
- * reallocating for the same index
- */
- spin_lock(&index_init_lock);
-
- if (mem_section[root]) {
- ret = -EEXIST;
- goto out;
- }
mem_section[root] = section;
-out:
- spin_unlock(&index_init_lock);
+
return ret;
}
#else /* !SPARSEMEM_EXTREME */