On 06/27/2012 09:36 AM, Gavin Shan wrote: > With CONFIG_SPARSEMEM_EXTREME, the root memory section descriptors > are allocated by slab or bootmem allocator. Also, the descriptors > might have been allocated and initialized during the hotplug path. > However, the memory chunk allocated in current implementation wouldn't > be put into the available pool if that has been allocated. The situation > will lead to memory leak. I've read this changelog about ten times and I'm still not really clear what the bug is here. -- 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. -- Technically, I'm not sure that we can race during the time when we'd be using bootmem. I think we do all those initializations single-threaded at the moment, and we'd finish them before we turn the slab on. So, technically, we probably don't need the bootmem stuff in sparse_index_free(). But, I guess it doesn't hurt, and it's fine for completeness. Gavin, have you actually tested this in some way? It looks OK to me, but I worry that you've just added a block of code that's exceedingly unlikely to get run. -- 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>