[openib-general] [PATCH] for 2.6.17: mad: fix queuing work item after destroying wq

[Sean Hefty]

Fix an oopsable race debugged by Eli Cohen.  After removing the port from
port_list, ib_mad_port_close flushes port_priv->wq before destroying the
special QPs.  This means that a completion event could arrive, and queue new
work  in this work queue after flush.

This patch also removes an unnecessary flush_workqueue: destroy_workqueue
already includes a flush.

Signed-off-by: Michael S. Tsirkin <mst at mellanox.co.il>
Signed-off-by: Sean Hefty <sean.hefty at intel.com>

---

 drivers/infiniband/core/mad.c |   21 ++++++++++++++-------
 1 files changed, 14 insertions(+), 7 deletions(-)

4bf096f7c91b67d48a3f63f6395d762b583886ee
diff --git a/drivers/infiniband/core/mad.c b/drivers/infiniband/core/mad.c
index 16549ad..f7854b6 100644
--- a/drivers/infiniband/core/mad.c
+++ b/drivers/infiniband/core/mad.c
@@ -2364,8 +2364,12 @@ static void timeout_sends(void *data)
 static void ib_mad_thread_completion_handler(struct ib_cq *cq, void *arg)
 {
 	struct ib_mad_port_private *port_priv = cq->cq_context;
+	unsigned long flags;
 
-	queue_work(port_priv->wq, &port_priv->work);
+	spin_lock_irqsave(&ib_mad_port_list_lock, flags);
+	if (!list_empty(&port_priv->port_list))
+		queue_work(port_priv->wq, &port_priv->work);
+	spin_unlock_irqrestore(&ib_mad_port_list_lock, flags);
 }
 
 /*
@@ -2677,18 +2681,23 @@ static int ib_mad_port_open(struct ib_de
 	}
 	INIT_WORK(&port_priv->work, ib_mad_completion_handler, port_priv);
 
+	spin_lock_irqsave(&ib_mad_port_list_lock, flags);
+	list_add_tail(&port_priv->port_list, &ib_mad_port_list);
+	spin_unlock_irqrestore(&ib_mad_port_list_lock, flags);
+
 	ret = ib_mad_port_start(port_priv);
 	if (ret) {
 		printk(KERN_ERR PFX "Couldn't start port\n");
 		goto error9;
 	}
 
-	spin_lock_irqsave(&ib_mad_port_list_lock, flags);
-	list_add_tail(&port_priv->port_list, &ib_mad_port_list);
-	spin_unlock_irqrestore(&ib_mad_port_list_lock, flags);
 	return 0;
 
 error9:
+	spin_lock_irqsave(&ib_mad_port_list_lock, flags);
+	list_del_init(&port_priv->port_list);
+	spin_unlock_irqrestore(&ib_mad_port_list_lock, flags);
+
 	destroy_workqueue(port_priv->wq);
 error8:
 	destroy_mad_qp(&port_priv->qp_info[1]);
@@ -2725,11 +2734,9 @@ static int ib_mad_port_close(struct ib_d
 		printk(KERN_ERR PFX "Port %d not found\n", port_num);
 		return -ENODEV;
 	}
-	list_del(&port_priv->port_list);
+	list_del_init(&port_priv->port_list);
 	spin_unlock_irqrestore(&ib_mad_port_list_lock, flags);
 
-	/* Stop processing completions. */
-	flush_workqueue(port_priv->wq);
 	destroy_workqueue(port_priv->wq);
 	destroy_mad_qp(&port_priv->qp_info[1]);
 	destroy_mad_qp(&port_priv->qp_info[0]);
-- 
1.0.6