Fix bug in iwcm that caused a panic in iw_cm_wq when krping is run

repeatedly in a tight loop.

Approved by:	re (gjb@)
Obtained from:	hselasky@ (part of larger changes in D5791)

1 files changed, 11 insertions, 2 deletions

diff --git a/sys/ofed/drivers/infiniband/core/iwcm.c b/sys/ofed/drivers/infiniband/core/iwcm.c
index 7e27584..5a1cc72 100644
--- a/sys/ofed/drivers/infiniband/core/iwcm.c
+++ b/sys/ofed/drivers/infiniband/core/iwcm.c
@@ -266,9 +266,16 @@ static void add_ref(struct iw_cm_id *cm_id)
 static void rem_ref(struct iw_cm_id *cm_id)
 {
 	struct iwcm_id_private *cm_id_priv;
+	int cb_destroy;
+
 	cm_id_priv = container_of(cm_id, struct iwcm_id_private, id);
-	if (iwcm_deref_id(cm_id_priv) &&
-	    test_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags)) {
+
+	/*
+	 * Test bit before deref in case the cm_id gets freed on another
+	 * thread.
+	 */
+	cb_destroy = test_bit(IWCM_F_CALLBACK_DESTROY, &cm_id_priv->flags);
+	if (iwcm_deref_id(cm_id_priv) && cb_destroy) {
 		BUG_ON(!list_empty(&cm_id_priv->work_list));
 		free_cm_id(cm_id_priv);
 	}
@@ -1157,6 +1164,8 @@ static void cm_work_handler(struct work_struct *_work)
 			}
 			return;
 		}
+		if (empty)
+			return;
 		spin_lock_irqsave(&cm_id_priv->lock, flags);
 	}
 	spin_unlock_irqrestore(&cm_id_priv->lock, flags);