From 4d6e8a033f7c6665c7ca5c5cdcf66019baa4b7a2 Mon Sep 17 00:00:00 2001 From: Danit Goldberg Date: Thu, 19 Dec 2019 15:47:50 +0200 Subject: [PATCH] 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: Danit Goldberg Signed-off-by: Leon Romanovsky Reviewed-by: Jason Gunthorpe Signed-off-by: Jason Gunthorpe --- drivers/infiniband/core/cm.c | 43 +++++++++++++------------------------------ 1 file changed, 13 insertions(+), 30 deletions(-) diff --git a/drivers/infiniband/core/cm.c b/drivers/infiniband/core/cm.c index 455b365..2945031 100644 --- a/drivers/infiniband/core/cm.c +++ b/drivers/infiniband/core/cm.c @@ -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 - 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); + if (!cm_id_priv || cm_id_priv->id.remote_id != remote_id || + !refcount_inc_not_zero(&cm_id_priv->refcount)) + cm_id_priv = NULL; + 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); -- 2.7.4