[PATCH] IB: Fix timeout/cancelled MAD handling

Fixes an issue processing a sent MAD after it has timed out or been canceled.
The race occurs when a response MAD matches with the send request.  The
request could time out or be canceled after the response MAD matches with the
request, but before the request completion can be processed.

Signed-off-by: Sean Hefty <[email protected]>
Signed-off-by: Hal Rosenstock <[email protected]>
Cc: Roland Dreier <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Hal Rosenstock

drivers/infiniband/core/mad.c

@@ -341,6 +341,7 @@ struct ib_mad_agent *ib_register_mad_agent(struct ib_device *device,
 	spin_lock_init(&mad_agent_priv->lock);
 	INIT_LIST_HEAD(&mad_agent_priv->send_list);
 	INIT_LIST_HEAD(&mad_agent_priv->wait_list);
+	INIT_LIST_HEAD(&mad_agent_priv->done_list);
 	INIT_WORK(&mad_agent_priv->timed_work, timeout_sends, mad_agent_priv);
 	INIT_LIST_HEAD(&mad_agent_priv->local_list);
 	INIT_WORK(&mad_agent_priv->local_work, local_completions,
@@ -1559,6 +1560,16 @@ find_send_req(struct ib_mad_agent_private *mad_agent_priv,
 	return NULL;
 }
 
+static void ib_mark_req_done(struct ib_mad_send_wr_private *mad_send_wr)
+{
+	mad_send_wr->timeout = 0;
+	if (mad_send_wr->refcount == 1) {
+		list_del(&mad_send_wr->agent_list);
+		list_add_tail(&mad_send_wr->agent_list,
+			      &mad_send_wr->mad_agent_priv->done_list);
+	}
+}
+
 static void ib_mad_complete_recv(struct ib_mad_agent_private *mad_agent_priv,
 				 struct ib_mad_recv_wc *mad_recv_wc)
 {
@@ -1580,8 +1591,7 @@ static void ib_mad_complete_recv(struct ib_mad_agent_private *mad_agent_priv,
 				wake_up(&mad_agent_priv->wait);
 			return;
 		}
-		/* Timeout = 0 means that we won't wait for a response */
-		mad_send_wr->timeout = 0;
+		ib_mark_req_done(mad_send_wr);
 		spin_unlock_irqrestore(&mad_agent_priv->lock, flags);
 
 		/* Defined behavior is to complete response before request */

drivers/infiniband/core/mad_priv.h

@@ -92,6 +92,7 @@ struct ib_mad_agent_private {
 	spinlock_t lock;
 	struct list_head send_list;
 	struct list_head wait_list;
+	struct list_head done_list;
 	struct work_struct timed_work;
 	unsigned long timeout;
 	struct list_head local_list;