Commit 2a7cec53 authored by Jason Gunthorpe's avatar Jason Gunthorpe
Browse files

RDMA/cma: Fix locking for the RDMA_CM_CONNECT state 

It is currently a bit confusing, but the design is if the handler_mutex
is held, and the state is in RDMA_CM_CONNECT, then the state cannot leave
RDMA_CM_CONNECT without also serializing with the handler_mutex.

Make this clearer by adding a direct assertion, fixing the usage in
rdma_connect and generally using READ_ONCE to read the state value.

Link: https://lore.kernel.org/r/20200902081122.745412-2-leon@kernel.org


Signed-off-by: default avatarLeon Romanovsky <leonro@nvidia.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
parent 3cc30e8d

drivers/infiniband/core/cma.c

+30 −14
Original line number Diff line number Diff line
@@ -421,6 +421,15 @@ static int cma_comp_exch(struct rdma_id_private *id_priv, 
	unsigned long flags;

	int ret;



	/*

	 * The FSM uses a funny double locking where state is protected by both

	 * the handler_mutex and the spinlock. State is not allowed to change

	 * away from a handler_mutex protected value without also holding

	 * handler_mutex.

	 */

	if (comp == RDMA_CM_CONNECT)

		lockdep_assert_held(&id_priv->handler_mutex);



	spin_lock_irqsave(&id_priv->lock, flags);

	if ((ret = (id_priv->state == comp)))

		id_priv->state = exch;
@@ -1949,13 +1958,15 @@ static int cma_ib_handler(struct ib_cm_id *cm_id, 
{

	struct rdma_id_private *id_priv = cm_id->context;

	struct rdma_cm_event event = {};

	enum rdma_cm_state state;

	int ret;



	mutex_lock(&id_priv->handler_mutex);

	state = READ_ONCE(id_priv->state);

	if ((ib_event->event != IB_CM_TIMEWAIT_EXIT &&

	     id_priv->state != RDMA_CM_CONNECT) ||

	     state != RDMA_CM_CONNECT) ||

	    (ib_event->event == IB_CM_TIMEWAIT_EXIT &&

	     id_priv->state != RDMA_CM_DISCONNECT))

	     state != RDMA_CM_DISCONNECT))

		goto out;



	switch (ib_event->event) {
@@ -1965,7 +1976,7 @@ static int cma_ib_handler(struct ib_cm_id *cm_id, 
		event.status = -ETIMEDOUT;

		break;

	case IB_CM_REP_RECEIVED:

		if (cma_comp(id_priv, RDMA_CM_CONNECT) &&

		if (state == RDMA_CM_CONNECT &&

		    (id_priv->id.qp_type != IB_QPT_UD)) {

			trace_cm_send_mra(id_priv);

			ib_send_cm_mra(cm_id, CMA_CM_MRA_SETTING, NULL, 0);
@@ -2226,8 +2237,8 @@ static int cma_ib_req_handler(struct ib_cm_id *cm_id, 
		goto net_dev_put;

	}



	if (cma_comp(conn_id, RDMA_CM_CONNECT) &&

	    (conn_id->id.qp_type != IB_QPT_UD)) {

	if (READ_ONCE(conn_id->state) == RDMA_CM_CONNECT &&

	    conn_id->id.qp_type != IB_QPT_UD) {

		trace_cm_send_mra(cm_id->context);

		ib_send_cm_mra(cm_id, CMA_CM_MRA_SETTING, NULL, 0);

	}
@@ -2288,7 +2299,7 @@ static int cma_iw_handler(struct iw_cm_id *iw_id, struct iw_cm_event *iw_event) 
	struct sockaddr *raddr = (struct sockaddr *)&iw_event->remote_addr;



	mutex_lock(&id_priv->handler_mutex);

	if (id_priv->state != RDMA_CM_CONNECT)

	if (READ_ONCE(id_priv->state) != RDMA_CM_CONNECT)

		goto out;



	switch (iw_event->event) {
@@ -3778,7 +3789,7 @@ static int cma_sidr_rep_handler(struct ib_cm_id *cm_id, 
	int ret;



	mutex_lock(&id_priv->handler_mutex);

	if (id_priv->state != RDMA_CM_CONNECT)

	if (READ_ONCE(id_priv->state) != RDMA_CM_CONNECT)

		goto out;



	switch (ib_event->event) {
@@ -4014,12 +4025,15 @@ out: 


int rdma_connect(struct rdma_cm_id *id, struct rdma_conn_param *conn_param)

{

	struct rdma_id_private *id_priv;

	struct rdma_id_private *id_priv =

		container_of(id, struct rdma_id_private, id);

	int ret;



	id_priv = container_of(id, struct rdma_id_private, id);

	if (!cma_comp_exch(id_priv, RDMA_CM_ROUTE_RESOLVED, RDMA_CM_CONNECT))

		return -EINVAL;

	mutex_lock(&id_priv->handler_mutex);

	if (!cma_comp_exch(id_priv, RDMA_CM_ROUTE_RESOLVED, RDMA_CM_CONNECT)) {

		ret = -EINVAL;

		goto err_unlock;

	}



	if (!id->qp) {

		id_priv->qp_num = conn_param->qp_num;
@@ -4036,11 +4050,13 @@ int rdma_connect(struct rdma_cm_id *id, struct rdma_conn_param *conn_param) 
	else

		ret = -ENOSYS;

	if (ret)

		goto err;



		goto err_state;

	mutex_unlock(&id_priv->handler_mutex);

	return 0;

err:

err_state:

	cma_comp_exch(id_priv, RDMA_CM_CONNECT, RDMA_CM_ROUTE_RESOLVED);

err_unlock:

	mutex_unlock(&id_priv->handler_mutex);

	return ret;

}

EXPORT_SYMBOL(rdma_connect);

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