Commit cc9c0373 authored by Jason Gunthorpe's avatar Jason Gunthorpe
Browse files

RDMA/cma: Remove unneeded locking for req paths 

The REQ flows are concerned that once the handler is called on the new
cm_id the ULP can choose to trigger a rdma_destroy_id() concurrently at
any time.

However, this is not true, while the ULP can call rdma_destroy_id(), it
immediately blocks on the handler_mutex which prevents anything harmful
from running concurrently.

Remove the confusing extra locking and refcounts and make the
handler_mutex protecting state during destroy more clear.

Link: https://lore.kernel.org/r/20200723070707.1771101-4-leon@kernel.org


Signed-off-by: default avatarLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@nvidia.com>
parent 3647a28d

drivers/infiniband/core/cma.c

+6 −25
Original line number Diff line number Diff line
@@ -1827,21 +1827,21 @@ static void cma_leave_mc_groups(struct rdma_id_private *id_priv) 


void rdma_destroy_id(struct rdma_cm_id *id)

{

	struct rdma_id_private *id_priv;

	struct rdma_id_private *id_priv =

		container_of(id, struct rdma_id_private, id);

	enum rdma_cm_state state;



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

	trace_cm_id_destroy(id_priv);

	state = cma_exch(id_priv, RDMA_CM_DESTROYING);

	cma_cancel_operation(id_priv, state);



	/*

	 * Wait for any active callback to finish.  New callbacks will find

	 * the id_priv state set to destroying and abort.

	 */

	mutex_lock(&id_priv->handler_mutex);

	trace_cm_id_destroy(id_priv);

	state = cma_exch(id_priv, RDMA_CM_DESTROYING);

	mutex_unlock(&id_priv->handler_mutex);



	cma_cancel_operation(id_priv, state);



	rdma_restrack_del(&id_priv->res);

	if (id_priv->cma_dev) {

		if (rdma_cap_ib_cm(id_priv->id.device, 1)) {
@@ -2201,19 +2201,9 @@ static int cma_ib_req_handler(struct ib_cm_id *cm_id, 
	cm_id->context = conn_id;

	cm_id->cm_handler = cma_ib_handler;



	/*

	 * Protect against the user destroying conn_id from another thread

	 * until we're done accessing it.

	 */

	cma_id_get(conn_id);

	ret = cma_cm_event_handler(conn_id, &event);

	if (ret)

		goto err3;

	/*

	 * Acquire mutex to prevent user executing rdma_destroy_id()

	 * while we're accessing the cm_id.

	 */

	mutex_lock(&lock);

	if (cma_comp(conn_id, RDMA_CM_CONNECT) &&

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

		trace_cm_send_mra(cm_id->context);
@@ -2222,13 +2212,11 @@ static int cma_ib_req_handler(struct ib_cm_id *cm_id, 
	mutex_unlock(&lock);

	mutex_unlock(&conn_id->handler_mutex);

	mutex_unlock(&listen_id->handler_mutex);

	cma_id_put(conn_id);

	if (net_dev)

		dev_put(net_dev);

	return 0;



err3:

	cma_id_put(conn_id);

	/* Destroy the CM ID by returning a non-zero value. */

	conn_id->cm_id.ib = NULL;

err2:
@@ -2405,11 +2393,6 @@ static int iw_conn_req_handler(struct iw_cm_id *cm_id, 
	memcpy(cma_src_addr(conn_id), laddr, rdma_addr_size(laddr));

	memcpy(cma_dst_addr(conn_id), raddr, rdma_addr_size(raddr));



	/*

	 * Protect against the user destroying conn_id from another thread

	 * until we're done accessing it.

	 */

	cma_id_get(conn_id);

	ret = cma_cm_event_handler(conn_id, &event);

	if (ret) {

		/* User wants to destroy the CM ID */
@@ -2417,13 +2400,11 @@ static int iw_conn_req_handler(struct iw_cm_id *cm_id, 
		cma_exch(conn_id, RDMA_CM_DESTROYING);

		mutex_unlock(&conn_id->handler_mutex);

		mutex_unlock(&listen_id->handler_mutex);

		cma_id_put(conn_id);

		rdma_destroy_id(&conn_id->id);

		return ret;

	}



	mutex_unlock(&conn_id->handler_mutex);

	cma_id_put(conn_id);



out:

	mutex_unlock(&listen_id->handler_mutex);

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