LOCK_UNLOCK_2
LOCK_UNLOCK_2(A, B); \
LOCK_UNLOCK_2(B, A); /* fail */
LOCK_UNLOCK_2(A, B); \
LOCK_UNLOCK_2(B, C); \
LOCK_UNLOCK_2(C, A); /* fail */
LOCK_UNLOCK_2(A, B); \
LOCK_UNLOCK_2(C, A); \
LOCK_UNLOCK_2(B, C); /* fail */
LOCK_UNLOCK_2(A, B); \
LOCK_UNLOCK_2(B, C); \
LOCK_UNLOCK_2(C, D); \
LOCK_UNLOCK_2(D, A); /* fail */
LOCK_UNLOCK_2(A, B); \
LOCK_UNLOCK_2(C, D); \
LOCK_UNLOCK_2(B, D); \
LOCK_UNLOCK_2(D, A); /* fail */
LOCK_UNLOCK_2(A, B); \
LOCK_UNLOCK_2(C, D); \
LOCK_UNLOCK_2(B, C); \
LOCK_UNLOCK_2(D, A); /* fail */