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Commit 581bbe2c authored by Kumar Sanghvi's avatar Kumar Sanghvi Committed by Roland Dreier
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RDMA/cxgb4: Serialize calls to CQ's comp_handler 



Commit 01e7da6b ("RDMA/cxgb4: Make sure flush CQ entries are
collected on connection close") introduced a potential problem where a
CQ's comp_handler can get called simultaneously from different places
in the iw_cxgb4 driver.  This does not comply with
Documentation/infiniband/core_locking.txt, which states that at a
given point of time, there should be only one callback per CQ should
be active.

This problem was reported by Parav Pandit <Parav.Pandit@Emulex.Com>.
Based on discussion between Parav Pandit and Steve Wise, this patch
fixes the above problem by serializing the calls to a CQ's
comp_handler using a spin_lock.

Reported-by: default avatarParav Pandit <Parav.Pandit@Emulex.Com>
Signed-off-by: default avatarKumar Sanghvi <kumaras@chelsio.com>
Acked-by: default avatarSteve Wise <swise@opengridcomputing.com>
Signed-off-by: default avatarRoland Dreier <roland@purestorage.com>
parent e14d62c0

drivers/infiniband/hw/cxgb4/cq.c

+1 −0
Original line number Diff line number Diff line
@@ -818,6 +818,7 @@ struct ib_cq *c4iw_create_cq(struct ib_device *ibdev, int entries, 
	chp->cq.size--;				/* status page */

	chp->ibcq.cqe = entries - 2;

	spin_lock_init(&chp->lock);

	spin_lock_init(&chp->comp_handler_lock);

	atomic_set(&chp->refcnt, 1);

	init_waitqueue_head(&chp->wait);

	ret = insert_handle(rhp, &rhp->cqidr, chp, chp->cq.cqid);

drivers/infiniband/hw/cxgb4/ev.c

+8 −2
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ static void post_qp_event(struct c4iw_dev *dev, struct c4iw_cq *chp, 
{

	struct ib_event event;

	struct c4iw_qp_attributes attrs;

	unsigned long flag;



	if ((qhp->attr.state == C4IW_QP_STATE_ERROR) ||

	    (qhp->attr.state == C4IW_QP_STATE_TERMINATE)) {
@@ -72,7 +73,9 @@ static void post_qp_event(struct c4iw_dev *dev, struct c4iw_cq *chp, 
	if (qhp->ibqp.event_handler)

		(*qhp->ibqp.event_handler)(&event, qhp->ibqp.qp_context);



	spin_lock_irqsave(&chp->comp_handler_lock, flag);

	(*chp->ibcq.comp_handler)(&chp->ibcq, chp->ibcq.cq_context);

	spin_unlock_irqrestore(&chp->comp_handler_lock, flag);

}



void c4iw_ev_dispatch(struct c4iw_dev *dev, struct t4_cqe *err_cqe)
@@ -183,11 +186,14 @@ void c4iw_ev_dispatch(struct c4iw_dev *dev, struct t4_cqe *err_cqe) 
int c4iw_ev_handler(struct c4iw_dev *dev, u32 qid)

{

	struct c4iw_cq *chp;

	unsigned long flag;



	chp = get_chp(dev, qid);

	if (chp)

	if (chp) {

		spin_lock_irqsave(&chp->comp_handler_lock, flag);

		(*chp->ibcq.comp_handler)(&chp->ibcq, chp->ibcq.cq_context);

	else

		spin_unlock_irqrestore(&chp->comp_handler_lock, flag);

	} else

		PDBG("%s unknown cqid 0x%x\n", __func__, qid);

	return 0;

}

drivers/infiniband/hw/cxgb4/iw_cxgb4.h

+1 −0
Original line number Diff line number Diff line
@@ -309,6 +309,7 @@ struct c4iw_cq { 
	struct c4iw_dev *rhp;

	struct t4_cq cq;

	spinlock_t lock;

	spinlock_t comp_handler_lock;

	atomic_t refcnt;

	wait_queue_head_t wait;

};

drivers/infiniband/hw/cxgb4/qp.c

+13 −2
Original line number Diff line number Diff line
@@ -941,8 +941,11 @@ static void __flush_qp(struct c4iw_qp *qhp, struct c4iw_cq *rchp, 
	flushed = c4iw_flush_rq(&qhp->wq, &rchp->cq, count);

	spin_unlock(&qhp->lock);

	spin_unlock_irqrestore(&rchp->lock, flag);

	if (flushed)

	if (flushed) {

		spin_lock_irqsave(&rchp->comp_handler_lock, flag);

		(*rchp->ibcq.comp_handler)(&rchp->ibcq, rchp->ibcq.cq_context);

		spin_unlock_irqrestore(&rchp->comp_handler_lock, flag);

	}



	/* locking hierarchy: cq lock first, then qp lock. */

	spin_lock_irqsave(&schp->lock, flag);
@@ -952,13 +955,17 @@ static void __flush_qp(struct c4iw_qp *qhp, struct c4iw_cq *rchp, 
	flushed = c4iw_flush_sq(&qhp->wq, &schp->cq, count);

	spin_unlock(&qhp->lock);

	spin_unlock_irqrestore(&schp->lock, flag);

	if (flushed)

	if (flushed) {

		spin_lock_irqsave(&schp->comp_handler_lock, flag);

		(*schp->ibcq.comp_handler)(&schp->ibcq, schp->ibcq.cq_context);

		spin_unlock_irqrestore(&schp->comp_handler_lock, flag);

	}

}



static void flush_qp(struct c4iw_qp *qhp)

{

	struct c4iw_cq *rchp, *schp;

	unsigned long flag;



	rchp = get_chp(qhp->rhp, qhp->attr.rcq);

	schp = get_chp(qhp->rhp, qhp->attr.scq);
@@ -966,11 +973,15 @@ static void flush_qp(struct c4iw_qp *qhp) 
	if (qhp->ibqp.uobject) {

		t4_set_wq_in_error(&qhp->wq);

		t4_set_cq_in_error(&rchp->cq);

		spin_lock_irqsave(&rchp->comp_handler_lock, flag);

		(*rchp->ibcq.comp_handler)(&rchp->ibcq, rchp->ibcq.cq_context);

		spin_unlock_irqrestore(&rchp->comp_handler_lock, flag);

		if (schp != rchp) {

			t4_set_cq_in_error(&schp->cq);

			spin_lock_irqsave(&schp->comp_handler_lock, flag);

			(*schp->ibcq.comp_handler)(&schp->ibcq,

					schp->ibcq.cq_context);

			spin_unlock_irqrestore(&schp->comp_handler_lock, flag);

		}

		return;

	}