[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 <zach.brown@oracle.com>
Cc: Roland Dreier <rolandd@cisco.com>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 4 insertions, 1 deletions

diff --git a/drivers/infiniband/hw/mthca/mthca_qp.c b/drivers/infiniband/hw/mthca/mthca_qp.c
index 16c387d8170c..490fc783bb0c 100644
--- a/drivers/infiniband/hw/mthca/mthca_qp.c
+++ b/drivers/infiniband/hw/mthca/mthca_qp.c
@@ -224,7 +224,7 @@ static void *get_send_wqe(struct mthca_qp *qp, int n)
 
 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;
@@ -1114,6 +1114,9 @@ static int mthca_alloc_qp_common(struct mthca_dev *dev,
         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)