[PATCH] net/ibmnvic: Fix deadlock problem in reset

[Juliet Kim]

Subject: [PATCH] net/ibmnvic: Fix deadlock problem in reset

From: Juliet Kim <julietk at linux.vnet.ibm.com>

This patch changes to use rtnl_lock only during a reset to avoid
deadlock that could occur when a thread operating close is holding
rtnl_lock and waiting for reset_lock acquired by another thread,
which is waiting for rtnl_lock in order to set the number of tx/rx
queues during a reset.

Also, we now setting the number of tx/rx queues during a soft reset
for failover or LPM events.

Signed-off-by: Juliet Kim <julietk at linux.vnet.ibm.com>
---
  drivers/net/ethernet/ibm/ibmvnic.c |   59 
+++++++++++++-----------------------
  drivers/net/ethernet/ibm/ibmvnic.h |    2 +
  2 files changed, 22 insertions(+), 39 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c 
b/drivers/net/ethernet/ibm/ibmvnic.c
index 7893bef..4a5de59 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -1103,20 +1103,15 @@ static int ibmvnic_open(struct net_device *netdev)
         return 0;
     }

-   mutex_lock(&adapter->reset_lock);
-
     if (adapter->state != VNIC_CLOSED) {
         rc = ibmvnic_login(netdev);
-       if (rc) {
-           mutex_unlock(&adapter->reset_lock);
+       if (rc)
             return rc;
-       }

         rc = init_resources(adapter);
         if (rc) {
             netdev_err(netdev, "failed to initialize resources\n");
             release_resources(adapter);
-           mutex_unlock(&adapter->reset_lock);
             return rc;
         }
     }
@@ -1124,8 +1119,6 @@ static int ibmvnic_open(struct net_device *netdev)
     rc = __ibmvnic_open(netdev);
     netif_carrier_on(netdev);

-   mutex_unlock(&adapter->reset_lock);
-
     return rc;
  }

@@ -1269,10 +1262,8 @@ static int ibmvnic_close(struct net_device *netdev)
         return 0;
     }

-   mutex_lock(&adapter->reset_lock);
     rc = __ibmvnic_close(netdev);
     ibmvnic_cleanup(netdev);
-   mutex_unlock(&adapter->reset_lock);

     return rc;
  }
@@ -1820,20 +1811,15 @@ static int do_reset(struct ibmvnic_adapter *adapter,
                 return rc;
         } else if (adapter->req_rx_queues != old_num_rx_queues ||
                adapter->req_tx_queues != old_num_tx_queues) {
-           adapter->map_id = 1;
             release_rx_pools(adapter);
             release_tx_pools(adapter);
-           rc = init_rx_pools(netdev);
-           if (rc)
-               return rc;
-           rc = init_tx_pools(netdev);
-           if (rc)
-               return rc;
-
             release_napi(adapter);
-           rc = init_napi(adapter);
+           release_vpd_data(adapter);
+
+           rc = init_resources(adapter);
             if (rc)
                 return rc;
+
         } else {
             rc = reset_tx_pools(adapter);
             if (rc)
@@ -1917,17 +1903,8 @@ static int do_hard_reset(struct ibmvnic_adapter 
*adapter,
         adapter->state = VNIC_PROBED;
         return 0;
     }
-   /* netif_set_real_num_xx_queues needs to take rtnl lock here
-    * unless wait_for_reset is set, in which case the rtnl lock
-    * has already been taken before initializing the reset
-    */
-   if (!adapter->wait_for_reset) {
-       rtnl_lock();
-       rc = init_resources(adapter);
-       rtnl_unlock();
-   } else {
-       rc = init_resources(adapter);
-   }
+
+   rc = init_resources(adapter);
     if (rc)
         return rc;

@@ -1986,13 +1963,21 @@ static void __ibmvnic_reset(struct work_struct 
*work)
     struct ibmvnic_rwi *rwi;
     struct ibmvnic_adapter *adapter;
     struct net_device *netdev;
+   bool we_lock_rtnl = false;
     u32 reset_state;
     int rc = 0;

     adapter = container_of(work, struct ibmvnic_adapter, ibmvnic_reset);
     netdev = adapter->netdev;

-   mutex_lock(&adapter->reset_lock);
+   /* netif_set_real_num_xx_queues needs to take rtnl lock here
+    * unless wait_for_reset is set, in which case the rtnl lock
+    * has already been taken before initializing the reset
+    */
+   if (!adapter->wait_for_reset) {
+       rtnl_lock();
+       we_lock_rtnl = true;
+   }

     reset_state = adapter->state;


     rwi = get_next_rwi(adapter);
@@ -2020,12 +2005,11 @@ static void __ibmvnic_reset(struct work_struct 
*work)
     if (rc) {
         netdev_dbg(adapter->netdev, "Reset failed\n");
         free_all_rwi(adapter);
-       mutex_unlock(&adapter->reset_lock);
-       return;
     }

     adapter->resetting = false;
-   mutex_unlock(&adapter->reset_lock);
+   if (we_lock_rtnl)
+       rtnl_unlock();
  }

  static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
@@ -4768,7 +4752,6 @@ static int ibmvnic_probe(struct vio_dev *dev, 
const struct vio_device_id *id)

     INIT_WORK(&adapter->ibmvnic_reset, __ibmvnic_reset);
     INIT_LIST_HEAD(&adapter->rwi_list);
-   mutex_init(&adapter->reset_lock);
     mutex_init(&adapter->rwi_lock);
     adapter->resetting = false;

@@ -4840,8 +4823,8 @@ static int ibmvnic_remove(struct vio_dev *dev)
     struct ibmvnic_adapter *adapter = netdev_priv(netdev);

     adapter->state = VNIC_REMOVING;
-   unregister_netdev(netdev);
-   mutex_lock(&adapter->reset_lock);
+   rtnl_lock();
+   unregister_netdevice(netdev);

     release_resources(adapter);
     release_sub_crqs(adapter, 1);
@@ -4852,7 +4835,7 @@ static int ibmvnic_remove(struct vio_dev *dev)

     adapter->state = VNIC_REMOVED;

-   mutex_unlock(&adapter->reset_lock);
+   rtnl_unlock();
     device_remove_file(&dev->dev, &dev_attr_failover);
     free_netdev(netdev);
     dev_set_drvdata(&dev->dev, NULL);
diff --git a/drivers/net/ethernet/ibm/ibmvnic.h 
b/drivers/net/ethernet/ibm/ibmvnic.h
index 18103b8..99c4f8d 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.h
+++ b/drivers/net/ethernet/ibm/ibmvnic.h
@@ -1075,7 +1075,7 @@ struct ibmvnic_adapter {
     struct tasklet_struct tasklet;
     enum vnic_state state;
     enum ibmvnic_reset_reason reset_reason;
-   struct mutex reset_lock, rwi_lock;
+   struct mutex rwi_lock;
     struct list_head rwi_list;
     struct work_struct ibmvnic_reset;
     bool resetting;