RDMA/amso1100: Prevent deadlock in destroy QP
It is possible to swap the CQs used for send_cq and recv_cq when
creating two different QPs. If these two QPs are then destroyed at
the same time, an AB-BA deadlock can occur because the CQ locks are
taken our of order. Fix this by always taking CQ locks in a fixed
order.
Signed-off-by: Krishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/hw/amso1100/c2_qp.c b/drivers/infiniband/hw/amso1100/c2_qp.c
index 5bcf697..179d005 100644
--- a/drivers/infiniband/hw/amso1100/c2_qp.c
+++ b/drivers/infiniband/hw/amso1100/c2_qp.c
@@ -564,6 +564,32 @@
return err;
}
+static inline void c2_lock_cqs(struct c2_cq *send_cq, struct c2_cq *recv_cq)
+{
+ if (send_cq == recv_cq)
+ spin_lock_irq(&send_cq->lock);
+ else if (send_cq > recv_cq) {
+ spin_lock_irq(&send_cq->lock);
+ spin_lock_nested(&recv_cq->lock, SINGLE_DEPTH_NESTING);
+ } else {
+ spin_lock_irq(&recv_cq->lock);
+ spin_lock_nested(&send_cq->lock, SINGLE_DEPTH_NESTING);
+ }
+}
+
+static inline void c2_unlock_cqs(struct c2_cq *send_cq, struct c2_cq *recv_cq)
+{
+ if (send_cq == recv_cq)
+ spin_unlock_irq(&send_cq->lock);
+ else if (send_cq > recv_cq) {
+ spin_unlock(&recv_cq->lock);
+ spin_unlock_irq(&send_cq->lock);
+ } else {
+ spin_unlock(&send_cq->lock);
+ spin_unlock_irq(&recv_cq->lock);
+ }
+}
+
void c2_free_qp(struct c2_dev *c2dev, struct c2_qp *qp)
{
struct c2_cq *send_cq;
@@ -576,15 +602,9 @@
* Lock CQs here, so that CQ polling code can do QP lookup
* without taking a lock.
*/
- spin_lock_irq(&send_cq->lock);
- if (send_cq != recv_cq)
- spin_lock(&recv_cq->lock);
-
+ c2_lock_cqs(send_cq, recv_cq);
c2_free_qpn(c2dev, qp->qpn);
-
- if (send_cq != recv_cq)
- spin_unlock(&recv_cq->lock);
- spin_unlock_irq(&send_cq->lock);
+ c2_unlock_cqs(send_cq, recv_cq);
/*
* Destory qp in the rnic...