lock_downgrade    378 include/linux/lockdep.h extern void lock_downgrade(struct lockdep_map *lock, unsigned long ip);
lock_downgrade   4470 kernel/locking/lockdep.c EXPORT_SYMBOL_GPL(lock_downgrade);
lock_downgrade   1596 kernel/locking/rwsem.c 	lock_downgrade(&sem->dep_map, _RET_IP_);