We blindly assume that we can just take the rtnl lock and that will
prevent races with downing this interface. Unfortunately, that's not
the case. In ipoib_mcast_stop_thread() we will call flush_workqueue()
in an attempt to clear out all remaining instances of ipoib_join_task.
But, since this task is put on the same workqueue as the join task, the
flush_workqueue waits on this thread too. But this thread is deadlocked
on the rtnl lock. The better thing here is to use trylock and loop on
that until we either get the lock or we see that FLAG_ADMIN_UP has
been cleared, in which case we don't need to do anything anyway and we
just return.
Signed-off-by: Doug Ledford <dledford@xxxxxxxxxx>
---
drivers/infiniband/ulp/ipoib/ipoib_multicast.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
index a0a42859f12..7e9cd39b5ef 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_multicast.c
@@ -353,18 +353,27 @@ void ipoib_mcast_carrier_on_task(struct work_struct *work)
carrier_on_task);
struct ib_port_attr attr;
- /*
- * Take rtnl_lock to avoid racing with ipoib_stop() and
- * turning the carrier back on while a device is being
- * removed.
- */
if (ib_query_port(priv->ca, priv->port, &attr) ||
attr.state != IB_PORT_ACTIVE) {
ipoib_dbg(priv, "Keeping carrier off until IB port is active\n");
return;
}
- rtnl_lock();
+ /*
+ * Take rtnl_lock to avoid racing with ipoib_stop() and
+ * turning the carrier back on while a device is being
+ * removed. However, ipoib_stop() will attempt to flush
+ * the workqueue while holding the rtnl lock, so loop
+ * on trylock until either we get the lock or we see
+ * FLAG_ADMIN_UP go away as that signals that we are bailing
+ * and can safely ignore the carrier on work
+ */
+ while (!rtnl_trylock()) {
+ if (!test_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags))
+ return;
+ else
+ msleep(20);
+ }
if (!ipoib_cm_admin_enabled(priv->dev))
dev_set_mtu(priv->dev, min(priv->mcast_mtu, priv->admin_mtu));
netif_carrier_on(priv->dev);
--
1.9.3
--
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