> -----Original Message----- > From: linux-rdma-owner@xxxxxxxxxxxxxxx [mailto:linux-rdma-owner@xxxxxxxxxxxxxxx] On > Behalf Of Doug Ledford > Sent: Wednesday, December 10, 2014 11:47 AM > To: linux-rdma@xxxxxxxxxxxxxxx; roland@xxxxxxxxxx > Cc: Doug Ledford > Subject: [PATCH 02/10] IPoIB: Make the carrier_on_task race aware > > 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> Acked-by: Alex Estrin <alex.estrin@xxxxxxxxx> > --- > 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 eee66d13e5b..9862c76a83f 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); > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-rdma" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
