IB/mthca: Annotate CQ locking

mthca_ib_lock_cqs()/mthca_ib_unlock_cqs() are helper functions that
lock/unlock both CQs attached to a QP in the proper order to avoid
AB-BA deadlocks.  Annotate this so sparse can understand what's going
on (and warn us if we misuse these functions).

Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/mthca/mthca_qp.c

@@ -1319,10 +1319,12 @@ int mthca_alloc_qp(struct mthca_dev *dev,
 }
 
 static void mthca_lock_cqs(struct mthca_cq *send_cq, struct mthca_cq *recv_cq)
+	__acquires(&send_cq->lock) __acquires(&recv_cq->lock)
 {
-	if (send_cq == recv_cq)
+	if (send_cq == recv_cq) {
 		spin_lock_irq(&send_cq->lock);
-	else if (send_cq->cqn < recv_cq->cqn) {
+		__acquire(&recv_cq->lock);
+	} else if (send_cq->cqn < recv_cq->cqn) {
 		spin_lock_irq(&send_cq->lock);
 		spin_lock_nested(&recv_cq->lock, SINGLE_DEPTH_NESTING);
 	} else {
@@ -1332,10 +1334,12 @@ static void mthca_lock_cqs(struct mthca_cq *send_cq, struct mthca_cq *recv_cq)
 }
 
 static void mthca_unlock_cqs(struct mthca_cq *send_cq, struct mthca_cq *recv_cq)
+	__releases(&send_cq->lock) __releases(&recv_cq->lock)
 {
-	if (send_cq == recv_cq)
+	if (send_cq == recv_cq) {
+		__release(&recv_cq->lock);
 		spin_unlock_irq(&send_cq->lock);
-	else if (send_cq->cqn < recv_cq->cqn) {
+	} else if (send_cq->cqn < recv_cq->cqn) {
 		spin_unlock(&recv_cq->lock);
 		spin_unlock_irq(&send_cq->lock);
 	} else {