[RFC tip/locking v2 04/13] lockdep: Introduce lock_list::dep

To add recursive read locks into the dependency graph, we need to store the types of dependencies for the BFS later. There are four kinds of dependencies: * Non-recursive -> Non-recursive dependencies(NN) e.g. write_lock(prev) -> write_lock(next) * Recursive -> Non-recursive

[RFC tip/locking v2 04/13] lockdep: Introduce lock_list::dep

To add recursive read locks into the dependency graph, we need to store the types of dependencies for the BFS later. There are four kinds of dependencies: * Non-recursive -> Non-recursive dependencies(NN) e.g. write_lock(prev) -> write_lock(next) * Recursive -> Non-recursive