[PATCH] mthca: initialize send and receive queue locks separately

mthca: initialize send and receive queue locks separately

lockdep identifies a lock by the call site of its initialization. By
initializing the send and receive queue locks in mthca_wq_init() we confuse
lockdep. It warns that that the ordered acquiry of both locks in
mthca_modify_qp() is recursive acquiry of one lock:

=============================================
[ INFO: possible recursive locking detected ]
---------------------------------------------
modprobe/1192 is trying to acquire lock:
(&wq->lock){....}, at: [<f892b4db>] mthca_modify_qp+0x60/0xa7b [ib_mthca]
but task is already holding lock:
(&wq->lock){....}, at: [<f892b4ce>] mthca_modify_qp+0x53/0xa7b [ib_mthca]

Initializing the locks separately in mthca_alloc_qp_common() stops the
warning and will let lockdep enforce proper ordering on paths that acquire
both locks.

Signed-off-by: Zach Brown <[e-mail]>
Cc: Roland Dreier <[e-mail]>
Cc: Arjan van de Ven <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

drivers/infiniband/hw/mthca/mthca_qp.c

···
 
 static void mthca_wq_init(struct mthca_wq *wq)
 {
-	spin_lock_init(&wq->lock);
+	/* mthca_alloc_qp_common() initializes the locks */
 	wq->next_ind  = 0;
 	wq->last_comp = wq->max - 1;
 	wq->head      = 0;
···
 	qp->sq_policy    = send_policy;
 	mthca_wq_init(&qp->sq);
 	mthca_wq_init(&qp->rq);
+	/* these are initialized separately so lockdep can tell them apart */
+	spin_lock_init(&qp->sq.lock);
+	spin_lock_init(&qp->rq.lock);
 
 	ret = mthca_map_memfree(dev, qp);
 	if (ret)