On Mon, May 20, 2019 at 05:37:41AM +0530, Amit Kumar wrote: > HI, > > mm/slub.c: line 3973 > int __kmem_cache_shrink(struct kmem_cache *s) > { > int node; > int i; > struct kmem_cache_node *n; > struct page *page; > struct page *t; > struct list_head discard; > struct list_head promote[SHRINK_PROMOTE_MAX]; > unsigned long flags; > int ret = 0; > > flush_all(s); > for_each_kmem_cache_node(s, node, n) { > > How uninitialized variable node is being used in macro for_each_kmem_cache_node? > > node is a local variable with no extern and not initialized. > > mm/slab.h: line 490 > #define for_each_kmem_cache_node(__s, __node, __n) \ > for (__node = 0; __node < nr_node_ids; __node++) \ This _is_ the initialization of node. Macros are kinda funky, there isn't much more to say about that other than perhaps read up some more about how macros work in C and read a bunch more macros in the kernel e.g. include/linux/list.h Good luck, Tobin.