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| author | Gavin Shan <shangw@linux.vnet.ibm.com> | 2012-07-31 16:46:06 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-07-31 18:42:49 -0700 |
| commit | c1c9518331969f97ea403bac66f0fd4a85d204d5 (patch) | |
| tree | 9a3122ec4600b94784e86a99aec61a1e93a27da5 | |
| parent | db36a46113e101a8aa2d6ede41e78f2eaabed3f1 (diff) | |
| download | blackbird-op-linux-c1c9518331969f97ea403bac66f0fd4a85d204d5.tar.gz blackbird-op-linux-c1c9518331969f97ea403bac66f0fd4a85d204d5.zip | |
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>
| -rw-r--r-- | mm/sparse.c | 14 |
1 files changed, 1 insertions, 13 deletions
diff --git a/mm/sparse.c b/mm/sparse.c index 42ca0ea9af1b..fac95f2888f2 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 */ |
