Commit 4d6e8a03 authored by Danit Goldberg's avatar Danit Goldberg Committed by Jason Gunthorpe
Browse files

RDMA/cm: Use RCU synchronization mechanism to protect cm_id_private xa_load() 

The RCU mechanism is optimized for read-mostly scenarios and therefore
more suitable to protect the cm_id_private to decrease "cm.lock"
congestion.

This patch replaces the existing spinlock locking mechanism and kfree with
RCU mechanism in places where spinlock(cm.lock) protected xa_load
returning the cm_id_priv

In addition, delete the cm_get_id() function as there is no longer a
distinction if the caller already holds the cm_lock.

Remove an open coded version of cm_get_id().

Link: https://lore.kernel.org/r/20191219134750.413429-1-leon@kernel.org


Signed-off-by: default avatarDanit Goldberg <danitg@mellanox.com>
Signed-off-by: default avatarLeon Romanovsky <leonro@mellanox.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@mellanox.com>
Signed-off-by: default avatarJason Gunthorpe <jgg@mellanox.com>
parent 9f48db0d

drivers/infiniband/core/cm.c

+13 −30
Original line number Diff line number Diff line
@@ -241,6 +241,7 @@ struct cm_id_private { 
	/* Number of clients sharing this ib_cm_id. Only valid for listeners.

	 * Protected by the cm.lock spinlock. */

	int listen_sharecount;

	struct rcu_head rcu;



	struct ib_mad_send_buf *msg;

	struct cm_timewait_info *timewait_info;
@@ -593,28 +594,16 @@ static void cm_free_id(__be32 local_id) 
	xa_erase_irq(&cm.local_id_table, cm_local_id(local_id));

}



static struct cm_id_private * cm_get_id(__be32 local_id, __be32 remote_id)

static struct cm_id_private *cm_acquire_id(__be32 local_id, __be32 remote_id)

{

	struct cm_id_private *cm_id_priv;



	rcu_read_lock();

	cm_id_priv = xa_load(&cm.local_id_table, cm_local_id(local_id));

	if (cm_id_priv) {

		if (cm_id_priv->id.remote_id == remote_id)

			refcount_inc(&cm_id_priv->refcount);

		else

	if (!cm_id_priv || cm_id_priv->id.remote_id != remote_id ||

	    !refcount_inc_not_zero(&cm_id_priv->refcount))

		cm_id_priv = NULL;

	}



	return cm_id_priv;

}



static struct cm_id_private * cm_acquire_id(__be32 local_id, __be32 remote_id)

{

	struct cm_id_private *cm_id_priv;



	spin_lock_irq(&cm.lock);

	cm_id_priv = cm_get_id(local_id, remote_id);

	spin_unlock_irq(&cm.lock);

	rcu_read_unlock();



	return cm_id_priv;

}
@@ -1089,7 +1078,7 @@ retest: 
	rdma_destroy_ah_attr(&cm_id_priv->av.ah_attr);

	rdma_destroy_ah_attr(&cm_id_priv->alt_av.ah_attr);

	kfree(cm_id_priv->private_data);

	kfree(cm_id_priv);

	kfree_rcu(cm_id_priv, rcu);

}



void ib_destroy_cm_id(struct ib_cm_id *cm_id)
@@ -1821,7 +1810,7 @@ static struct cm_id_private * cm_match_req(struct cm_work *work, 
	spin_lock_irq(&cm.lock);

	timewait_info = cm_insert_remote_id(cm_id_priv->timewait_info);

	if (timewait_info) {

		cur_cm_id_priv = cm_get_id(timewait_info->work.local_id,

		cur_cm_id_priv = cm_acquire_id(timewait_info->work.local_id,

					   timewait_info->work.remote_id);

		spin_unlock_irq(&cm.lock);

		if (cur_cm_id_priv) {
@@ -1835,7 +1824,7 @@ static struct cm_id_private * cm_match_req(struct cm_work *work, 
	timewait_info = cm_insert_remote_qpn(cm_id_priv->timewait_info);

	if (timewait_info) {

		cm_cleanup_timewait(cm_id_priv->timewait_info);

		cur_cm_id_priv = cm_get_id(timewait_info->work.local_id,

		cur_cm_id_priv = cm_acquire_id(timewait_info->work.local_id,

					   timewait_info->work.remote_id);



		spin_unlock_irq(&cm.lock);
@@ -2293,7 +2282,7 @@ static int cm_rep_handler(struct cm_work *work) 
		rb_erase(&cm_id_priv->timewait_info->remote_id_node,

			 &cm.remote_id_table);

		cm_id_priv->timewait_info->inserted_remote_id = 0;

		cur_cm_id_priv = cm_get_id(timewait_info->work.local_id,

		cur_cm_id_priv = cm_acquire_id(timewait_info->work.local_id,

					   timewait_info->work.remote_id);



		spin_unlock(&cm.lock);
@@ -2788,14 +2777,8 @@ static struct cm_id_private * cm_acquire_rejected_id(struct cm_rej_msg *rej_msg) 
			spin_unlock_irq(&cm.lock);

			return NULL;

		}

		cm_id_priv = xa_load(&cm.local_id_table,

				cm_local_id(timewait_info->work.local_id));

		if (cm_id_priv) {

			if (cm_id_priv->id.remote_id == remote_id)

				refcount_inc(&cm_id_priv->refcount);

			else

				cm_id_priv = NULL;

		}

		cm_id_priv =

			cm_acquire_id(timewait_info->work.local_id, remote_id);

		spin_unlock_irq(&cm.lock);

	} else if (cm_rej_get_msg_rejected(rej_msg) == CM_MSG_RESPONSE_REQ)

		cm_id_priv = cm_acquire_id(rej_msg->remote_comm_id, 0);

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