1. 根目录:
2. kernel
3. rcu
4. Makefile

obj-y += update.o srcu.o
obj-$(CONFIG_RCU_TORTURE_TEST) += torture.o
obj-$(CONFIG_TREE_RCU) += tree.o
obj-$(CONFIG_TREE_PREEMPT_RCU) += tree.o
obj-$(CONFIG_TREE_RCU_TRACE) += tree_trace.o
obj-$(CONFIG_TINY_RCU) += tiny.o