RDMA/cma: Simplify locking needed for serialization of callbacks

The RDMA CM has some logic in place to make sure that callbacks on a
given CM ID are delivered to the consumer in a serialized manner.
Specifically it has code to protect against a device removal racing
with a running callback function.

This patch simplifies this logic by using a mutex per ID instead of a
wait queue and atomic variable.  This means that cma_disable_remove()
now is more properly named to cma_disable_callback(), and
cma_enable_remove() can now be removed because it just would become a
trivial wrapper around mutex_unlock().

Signed-off-by: Or Gerlitz <ogerlitz@voltaire.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

1 files changed, 50 insertions, 56 deletions

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 5fb506a4177..ae11d5cc74d 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -130,8 +130,7 @@ struct rdma_id_private {
 
         struct completion       comp;
         atomic_t                refcount;
-        wait_queue_head_t       wait_remove;
-        atomic_t                dev_remove;
+        struct mutex            handler_mutex;
 
         int                     backlog;
         int                     timeout_ms;
@@ -355,26 +354,15 @@ static void cma_deref_id(struct rdma_id_private *id_priv)
                 complete(&id_priv->comp);
 }
 
-static int cma_disable_remove(struct rdma_id_private *id_priv,
+static int cma_disable_callback(struct rdma_id_private *id_priv,
                               enum cma_state state)
 {
-        unsigned long flags;
-        int ret;
-
-        spin_lock_irqsave(&id_priv->lock, flags);
-        if (id_priv->state == state) {
-                atomic_inc(&id_priv->dev_remove);
-                ret = 0;
-        } else
-                ret = -EINVAL;
-        spin_unlock_irqrestore(&id_priv->lock, flags);
-        return ret;
-}
-
-static void cma_enable_remove(struct rdma_id_private *id_priv)
-{
-        if (atomic_dec_and_test(&id_priv->dev_remove))
-                wake_up(&id_priv->wait_remove);
+        mutex_lock(&id_priv->handler_mutex);
+        if (id_priv->state != state) {
+                mutex_unlock(&id_priv->handler_mutex);
+                return -EINVAL;
+        }
+        return 0;
 }
 
 static int cma_has_cm_dev(struct rdma_id_private *id_priv)
@@ -399,8 +387,7 @@ struct rdma_cm_id *rdma_create_id(rdma_cm_event_handler event_handler,
         mutex_init(&id_priv->qp_mutex);
         init_completion(&id_priv->comp);
         atomic_set(&id_priv->refcount, 1);
-        init_waitqueue_head(&id_priv->wait_remove);
-        atomic_set(&id_priv->dev_remove, 0);
+        mutex_init(&id_priv->handler_mutex);
         INIT_LIST_HEAD(&id_priv->listen_list);
         INIT_LIST_HEAD(&id_priv->mc_list);
         get_random_bytes(&id_priv->seq_num, sizeof id_priv->seq_num);
@@ -927,7 +914,7 @@ static int cma_ib_handler(struct ib_cm_id *cm_id, struct ib_cm_event *ib_event)
         struct rdma_cm_event event;
         int ret = 0;
 
-        if (cma_disable_remove(id_priv, CMA_CONNECT))
+        if (cma_disable_callback(id_priv, CMA_CONNECT))
                 return 0;
 
         memset(&event, 0, sizeof event);
@@ -984,12 +971,12 @@ static int cma_ib_handler(struct ib_cm_id *cm_id, struct ib_cm_event *ib_event)
                 /* Destroy the CM ID by returning a non-zero value. */
                 id_priv->cm_id.ib = NULL;
                 cma_exch(id_priv, CMA_DESTROYING);
-                cma_enable_remove(id_priv);
+                mutex_unlock(&id_priv->handler_mutex);
                 rdma_destroy_id(&id_priv->id);
                 return ret;
         }
 out:
-        cma_enable_remove(id_priv);
+        mutex_unlock(&id_priv->handler_mutex);
         return ret;
 }
 
@@ -1101,7 +1088,7 @@ static int cma_req_handler(struct ib_cm_id *cm_id, struct ib_cm_event *ib_event)
         int offset, ret;
 
         listen_id = cm_id->context;
-        if (cma_disable_remove(listen_id, CMA_LISTEN))
+        if (cma_disable_callback(listen_id, CMA_LISTEN))
                 return -ECONNABORTED;
 
         memset(&event, 0, sizeof event);
@@ -1122,7 +1109,7 @@ static int cma_req_handler(struct ib_cm_id *cm_id, struct ib_cm_event *ib_event)
                 goto out;
         }
 
-        atomic_inc(&conn_id->dev_remove);
+        mutex_lock_nested(&conn_id->handler_mutex, SINGLE_DEPTH_NESTING);
         mutex_lock(&lock);
         ret = cma_acquire_dev(conn_id);
         mutex_unlock(&lock);
@@ -1144,7 +1131,7 @@ static int cma_req_handler(struct ib_cm_id *cm_id, struct ib_cm_event *ib_event)
                     !cma_is_ud_ps(conn_id->id.ps))
                         ib_send_cm_mra(cm_id, CMA_CM_MRA_SETTING, NULL, 0);
                 mutex_unlock(&lock);
-                cma_enable_remove(conn_id);
+                mutex_unlock(&conn_id->handler_mutex);
                 goto out;
         }
 
@@ -1153,11 +1140,11 @@ static int cma_req_handler(struct ib_cm_id *cm_id, struct ib_cm_event *ib_event)
 
 release_conn_id:
         cma_exch(conn_id, CMA_DESTROYING);
-        cma_enable_remove(conn_id);
+        mutex_unlock(&conn_id->handler_mutex);
         rdma_destroy_id(&conn_id->id);
 
 out:
-        cma_enable_remove(listen_id);
+        mutex_unlock(&listen_id->handler_mutex);
         return ret;
 }
 
@@ -1223,7 +1210,7 @@ static int cma_iw_handler(struct iw_cm_id *iw_id, struct iw_cm_event *iw_event)
         struct sockaddr_in *sin;
         int ret = 0;
 
-        if (cma_disable_remove(id_priv, CMA_CONNECT))
+        if (cma_disable_callback(id_priv, CMA_CONNECT))
                 return 0;
 
         memset(&event, 0, sizeof event);
@@ -1267,12 +1254,12 @@ static int cma_iw_handler(struct iw_cm_id *iw_id, struct iw_cm_event *iw_event)
                 /* Destroy the CM ID by returning a non-zero value. */
                 id_priv->cm_id.iw = NULL;
                 cma_exch(id_priv, CMA_DESTROYING);
-                cma_enable_remove(id_priv);
+                mutex_unlock(&id_priv->handler_mutex);
                 rdma_destroy_id(&id_priv->id);
                 return ret;
         }
 
-        cma_enable_remove(id_priv);
+        mutex_unlock(&id_priv->handler_mutex);
         return ret;
 }
 
@@ -1288,7 +1275,7 @@ static int iw_conn_req_handler(struct iw_cm_id *cm_id,
         struct ib_device_attr attr;
 
         listen_id = cm_id->context;
-        if (cma_disable_remove(listen_id, CMA_LISTEN))
+        if (cma_disable_callback(listen_id, CMA_LISTEN))
                 return -ECONNABORTED;
 
         /* Create a new RDMA id for the new IW CM ID */
@@ -1300,19 +1287,19 @@ static int iw_conn_req_handler(struct iw_cm_id *cm_id,
                 goto out;
         }
         conn_id = container_of(new_cm_id, struct rdma_id_private, id);
-        atomic_inc(&conn_id->dev_remove);
+        mutex_lock_nested(&conn_id->handler_mutex, SINGLE_DEPTH_NESTING);
         conn_id->state = CMA_CONNECT;
 
         dev = ip_dev_find(&init_net, iw_event->local_addr.sin_addr.s_addr);
         if (!dev) {
                 ret = -EADDRNOTAVAIL;
-                cma_enable_remove(conn_id);
+                mutex_unlock(&conn_id->handler_mutex);
                 rdma_destroy_id(new_cm_id);
                 goto out;
         }
         ret = rdma_copy_addr(&conn_id->id.route.addr.dev_addr, dev, NULL);
         if (ret) {
-                cma_enable_remove(conn_id);
+                mutex_unlock(&conn_id->handler_mutex);
                 rdma_destroy_id(new_cm_id);
                 goto out;
         }
@@ -1321,7 +1308,7 @@ static int iw_conn_req_handler(struct iw_cm_id *cm_id,
         ret = cma_acquire_dev(conn_id);
         mutex_unlock(&lock);
         if (ret) {
-                cma_enable_remove(conn_id);
+                mutex_unlock(&conn_id->handler_mutex);
                 rdma_destroy_id(new_cm_id);
                 goto out;
         }
@@ -1337,7 +1324,7 @@ static int iw_conn_req_handler(struct iw_cm_id *cm_id,
 
         ret = ib_query_device(conn_id->id.device, &attr);
         if (ret) {
-                cma_enable_remove(conn_id);
+                mutex_unlock(&conn_id->handler_mutex);
                 rdma_destroy_id(new_cm_id);
                 goto out;
         }
@@ -1353,14 +1340,17 @@ static int iw_conn_req_handler(struct iw_cm_id *cm_id,
                 /* User wants to destroy the CM ID */
                 conn_id->cm_id.iw = NULL;
                 cma_exch(conn_id, CMA_DESTROYING);
-                cma_enable_remove(conn_id);
+                mutex_unlock(&conn_id->handler_mutex);
                 rdma_destroy_id(&conn_id->id);
+                goto out;
         }
 
+        mutex_unlock(&conn_id->handler_mutex);
+
 out:
         if (dev)
                 dev_put(dev);
-        cma_enable_remove(listen_id);
+        mutex_unlock(&listen_id->handler_mutex);
         return ret;
 }
 
@@ -1592,7 +1582,7 @@ static void cma_work_handler(struct work_struct *_work)
         struct rdma_id_private *id_priv = work->id;
         int destroy = 0;
 
-        atomic_inc(&id_priv->dev_remove);
+        mutex_lock(&id_priv->handler_mutex);
         if (!cma_comp_exch(id_priv, work->old_state, work->new_state))
                 goto out;
 
@@ -1601,7 +1591,7 @@ static void cma_work_handler(struct work_struct *_work)
                 destroy = 1;
         }
 out:
-        cma_enable_remove(id_priv);
+        mutex_unlock(&id_priv->handler_mutex);
         cma_deref_id(id_priv);
         if (destroy)
                 rdma_destroy_id(&id_priv->id);
@@ -1764,7 +1754,7 @@ static void addr_handler(int status, struct sockaddr *src_addr,
         struct rdma_cm_event event;
 
         memset(&event, 0, sizeof event);
-        atomic_inc(&id_priv->dev_remove);
+        mutex_lock(&id_priv->handler_mutex);
 
         /*
          * Grab mutex to block rdma_destroy_id() from removing the device while
@@ -1793,13 +1783,13 @@ static void addr_handler(int status, struct sockaddr *src_addr,
 
         if (id_priv->id.event_handler(&id_priv->id, &event)) {
                 cma_exch(id_priv, CMA_DESTROYING);
-                cma_enable_remove(id_priv);
+                mutex_unlock(&id_priv->handler_mutex);
                 cma_deref_id(id_priv);
                 rdma_destroy_id(&id_priv->id);
                 return;
         }
 out:
-        cma_enable_remove(id_priv);
+        mutex_unlock(&id_priv->handler_mutex);
         cma_deref_id(id_priv);
 }
 
@@ -2126,7 +2116,7 @@ static int cma_sidr_rep_handler(struct ib_cm_id *cm_id,
         struct ib_cm_sidr_rep_event_param *rep = &ib_event->param.sidr_rep_rcvd;
         int ret = 0;
 
-        if (cma_disable_remove(id_priv, CMA_CONNECT))
+        if (cma_disable_callback(id_priv, CMA_CONNECT))
                 return 0;
 
         memset(&event, 0, sizeof event);
@@ -2167,12 +2157,12 @@ static int cma_sidr_rep_handler(struct ib_cm_id *cm_id,
                 /* Destroy the CM ID by returning a non-zero value. */
                 id_priv->cm_id.ib = NULL;
                 cma_exch(id_priv, CMA_DESTROYING);
-                cma_enable_remove(id_priv);
+                mutex_unlock(&id_priv->handler_mutex);
                 rdma_destroy_id(&id_priv->id);
                 return ret;
         }
 out:
-        cma_enable_remove(id_priv);
+        mutex_unlock(&id_priv->handler_mutex);
         return ret;
 }
 
@@ -2570,8 +2560,8 @@ static int cma_ib_mc_handler(int status, struct ib_sa_multicast *multicast)
         int ret;
 
         id_priv = mc->id_priv;
-        if (cma_disable_remove(id_priv, CMA_ADDR_BOUND) &&
-            cma_disable_remove(id_priv, CMA_ADDR_RESOLVED))
+        if (cma_disable_callback(id_priv, CMA_ADDR_BOUND) &&
+            cma_disable_callback(id_priv, CMA_ADDR_RESOLVED))
                 return 0;
 
         mutex_lock(&id_priv->qp_mutex);
@@ -2596,12 +2586,12 @@ static int cma_ib_mc_handler(int status, struct ib_sa_multicast *multicast)
         ret = id_priv->id.event_handler(&id_priv->id, &event);
         if (ret) {
                 cma_exch(id_priv, CMA_DESTROYING);
-                cma_enable_remove(id_priv);
+                mutex_unlock(&id_priv->handler_mutex);
                 rdma_destroy_id(&id_priv->id);
                 return 0;
         }
 
-        cma_enable_remove(id_priv);
+        mutex_unlock(&id_priv->handler_mutex);
         return 0;
 }
 
@@ -2760,6 +2750,7 @@ static int cma_remove_id_dev(struct rdma_id_private *id_priv)
 {
         struct rdma_cm_event event;
         enum cma_state state;
+        int ret = 0;
 
         /* Record that we want to remove the device */
         state = cma_exch(id_priv, CMA_DEVICE_REMOVAL);
@@ -2767,15 +2758,18 @@ static int cma_remove_id_dev(struct rdma_id_private *id_priv)
                 return 0;
 
         cma_cancel_operation(id_priv, state);
-        wait_event(id_priv->wait_remove, !atomic_read(&id_priv->dev_remove));
+        mutex_lock(&id_priv->handler_mutex);
 
         /* Check for destruction from another callback. */
         if (!cma_comp(id_priv, CMA_DEVICE_REMOVAL))
-                return 0;
+                goto out;
 
         memset(&event, 0, sizeof event);
         event.event = RDMA_CM_EVENT_DEVICE_REMOVAL;
-        return id_priv->id.event_handler(&id_priv->id, &event);
+        ret = id_priv->id.event_handler(&id_priv->id, &event);
+out:
+        mutex_unlock(&id_priv->handler_mutex);
+        return ret;
 }
 
 static void cma_process_remove(struct cma_device *cma_dev)