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 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>