IPoIB: Fix deadlock on RTNL between bcast join comp and ipoib_stop()
Taking rtnl_lock in ipoib_mcast_join_complete() causes a deadlock with
ipoib_stop(). We avoid it by scheduling the piece of code that takes
the lock on ipoib_workqueue instead of executing it directly. This
works because we only flush the ipoib_workqueue with the RTNL not held.
The deadlock happens because ipoib_stop() calls ipoib_ib_dev_down()
which calls ipoib_mcast_dev_flush(), which calls ipoib_mcast_free(),
which calls ipoib_mcast_leave(). The latter calls
ib_sa_free_multicast(), and this waits until the multicast completion
handler finishes. This handler is ipoib_mcast_join_complete(), which
waits for the rtnl_lock(), which was already taken by ipoib_stop().
This bug was introduced in commit a77a57a1 ("IPoIB: Fix deadlock on
RTNL in ipoib_stop()").
Signed-off-by: Yossi Etigin <yosefe@voltaire.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
index ac33c8f..aae2862 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -366,6 +366,21 @@
return ret;
}
+void ipoib_mcast_carrier_on_task(struct work_struct *work)
+{
+ struct ipoib_dev_priv *priv = container_of(work, struct ipoib_dev_priv,
+ carrier_on_task);
+
+ /*
+ * Take rtnl_lock to avoid racing with ipoib_stop() and
+ * turning the carrier back on while a device is being
+ * removed.
+ */
+ rtnl_lock();
+ netif_carrier_on(priv->dev);
+ rtnl_unlock();
+}
+
static int ipoib_mcast_join_complete(int status,
struct ib_sa_multicast *multicast)
{
@@ -392,16 +407,12 @@
&priv->mcast_task, 0);
mutex_unlock(&mcast_mutex);
- if (mcast == priv->broadcast) {
- /*
- * Take RTNL lock here to avoid racing with
- * ipoib_stop() and turning the carrier back
- * on while a device is being removed.
- */
- rtnl_lock();
- netif_carrier_on(dev);
- rtnl_unlock();
- }
+ /*
+ * Defer carrier on work to ipoib_workqueue to avoid a
+ * deadlock on rtnl_lock here.
+ */
+ if (mcast == priv->broadcast)
+ queue_work(ipoib_workqueue, &priv->carrier_on_task);
return 0;
}