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Commit c9edea29 authored by Krishna Kumar's avatar Krishna Kumar Committed by Roland Dreier
Browse files

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: default avatarKrishna Kumar <krkumar2@in.ibm.com>
Signed-off-by: default avatarRoland Dreier <rolandd@cisco.com>
parent 7013696a

drivers/infiniband/hw/amso1100/c2_qp.c

+28 −8
Original line number Diff line number Diff line
@@ -564,6 +564,32 @@ int c2_alloc_qp(struct c2_dev *c2dev, 
	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 @@ void c2_free_qp(struct c2_dev *c2dev, struct c2_qp *qp) 
	 * 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...