READ_ENTER
# define READ_ENTER(x) ipf_read_enter(x)
# define READ_ENTER(x) lock_read((x)->ipf_lk)
# define READ_ENTER(x) eMrwlock_read_enter(&(x)->ipf_emu, \
# define READ_ENTER(x) ;
# define READ_ENTER(x) rw_enter(&(x)->ipf_lk, RW_READER)
# define READ_ENTER(x) lock_read(&(x)->ipf_lk)
# define READ_ENTER(x) MUTEX_ENTER(x)
# define READ_ENTER(x) RW_RDLOCK(&(x)->ipf_lk)
# define READ_ENTER(x) MUTEX_ENTER(&(x)->ipf_lk)
# define READ_ENTER(x) lock_read(&(x)->ipf_lk)
# define READ_ENTER(x) mtx_lock(&(x)->ipf_lk)
# define READ_ENTER(x) sx_slock(&(x)->ipf_lk)
#define READ_ENTER(x) rw_enter(x, RW_READER)
#define READ_ENTER(x) rw_enter(x, RW_READER)
#define READ_ENTER(x) rw_enter(x, RW_READER)