On Mon 02-07-12 17:28:56, Gavin Shan wrote:
> sparse_index_init() is designed to be safe if two copies of it race. It
> uses "index_init_lock" to ensure that, even in the case of a race, only
> one CPU will manage to do:
>
> mem_section[root] = section;
>
> However, in the case where two copies of sparse_index_init() _do_ race,
> the one that loses the race will leak the "section" that
> sparse_index_alloc() allocated for it. This patch fixes that leak.
I would still like to hear how we can possibly race in this code path.
I've thought that memory onlining is done from a single CPU.
>
> Signed-off-by: Gavin Shan <shangw@xxxxxxxxxxxxxxxxxx>
> ---
> mm/sparse.c | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 781fa04..a6984d9 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -75,6 +75,20 @@ static struct mem_section noinline __init_refok *sparse_index_alloc(int nid)
> return section;
> }
>
> +static inline void __meminit sparse_index_free(struct mem_section *section)
> +{
> + unsigned long size = SECTIONS_PER_ROOT *
> + sizeof(struct mem_section);
> +
> + if (!section)
> + return;
> +
> + if (slab_is_available())
> + kfree(section);
> + else
> + free_bootmem(virt_to_phys(section), size);
> +}
> +
> static int __meminit sparse_index_init(unsigned long section_nr, int nid)
> {
> static DEFINE_SPINLOCK(index_init_lock);
> @@ -102,6 +116,9 @@ static int __meminit sparse_index_init(unsigned long section_nr, int nid)
> mem_section[root] = section;
> out:
> spin_unlock(&index_init_lock);
> + if (ret)
> + sparse_index_free(section);
> +
> return ret;
> }
> #else /* !SPARSEMEM_EXTREME */
> --
> 1.7.9.5
>
> --
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--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
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Czech Republic
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