Hi,
kmem_cache_{create,destroy,shrink} need to get a stable value of
cpu/node online mask, because they init/destroy/access per-cpu/node
kmem_cache parts, which can be allocated or destroyed on cpu/mem
hotplug. To protect against cpu hotplug, these functions use
{get,put}_online_cpus. However, they do nothing to synchronize with
memory hotplug - taking the slab_mutex does not eliminate the
possibility of race as described in patch 2.
What we need there is something like get_online_cpus, but for memory. We
already have lock_memory_hotplug, which serves for the purpose, but it's
a bit of a hammer right now, because it's backed by a mutex. As a
result, it imposes some limitations to locking order, which are not
desirable, and can't be used just like get_online_cpus. That's why in
patch 1 I substitute it with get/put_online_mems, which work exactly
like get/put_online_cpus except they block not cpu, but memory hotplug.
[ v1 can be found at https://lkml.org/lkml/2014/4/6/68. I NAK'ed it by
myself, because it used an rw semaphore for get/put_online_mems, making
them dead lock prune. ]
Thanks,
Vladimir Davydov (2):
mem-hotplug: implement get/put_online_mems
slab: lock_memory_hotplug for kmem_cache_{create,destroy,shrink}
include/linux/memory_hotplug.h | 14 ++--
include/linux/mmzone.h | 8 +--
mm/kmemleak.c | 4 +-
mm/memory-failure.c | 8 +--
mm/memory_hotplug.c | 142 ++++++++++++++++++++++++++++------------
mm/slab.c | 26 +-------
mm/slab.h | 1 +
mm/slab_common.c | 35 +++++++++-
mm/slob.c | 3 +-
mm/slub.c | 9 ++-
mm/vmscan.c | 2 +-
11 files changed, 155 insertions(+), 97 deletions(-)
--
1.7.10.4
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