IPoIB: Disable NAPI while CQ is being drained

If NAPI is enabled while IPoIB's CQ is being drained, it creates a
race on priv->ibwc between ipoib_poll() and ipoib_drain_cq(), leading
to memory corruption.

The solution is to enable/disable NAPI in ipoib_ib_dev_{open/stop}()
instead of in ipoib_{open/stop}(), and sync NAPI on the INITIALIZED
flag instead on the ADMIN_UP flag. This way NAPI will be disabled when
ipoib_drain_cq() is called.

This fixes <https://bugs.openfabrics.org/show_bug.cgi?id=1587>.

Signed-off-by: Yossi Etigin <yosefe@voltaire.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

2 files changed, 5 insertions, 6 deletions

diff --git a/drivers/infiniband/ulp/ipoib/ipoib_ib.c b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
index da6082739839..e7e5adf84e84 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_ib.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_ib.c
@@ -685,7 +685,8 @@ int ipoib_ib_dev_open(struct net_device *dev)
         queue_delayed_work(ipoib_workqueue, &priv->ah_reap_task,
                            round_jiffies_relative(HZ));
 
-        set_bit(IPOIB_FLAG_INITIALIZED, &priv->flags);
+        if (!test_and_set_bit(IPOIB_FLAG_INITIALIZED, &priv->flags))
+                napi_enable(&priv->napi);
 
         return 0;
 }
@@ -804,7 +805,8 @@ int ipoib_ib_dev_stop(struct net_device *dev, int flush)
         struct ipoib_tx_buf *tx_req;
         int i;
 
-        clear_bit(IPOIB_FLAG_INITIALIZED, &priv->flags);
+        if (test_and_clear_bit(IPOIB_FLAG_INITIALIZED, &priv->flags))
+                napi_disable(&priv->napi);
 
         ipoib_cm_dev_stop(dev);
 
diff --git a/drivers/infiniband/ulp/ipoib/ipoib_main.c b/drivers/infiniband/ulp/ipoib/ipoib_main.c
index 421a6640c9bd..ab2c192c76bc 100644
--- a/drivers/infiniband/ulp/ipoib/ipoib_main.c
+++ b/drivers/infiniband/ulp/ipoib/ipoib_main.c
@@ -106,8 +106,7 @@ int ipoib_open(struct net_device *dev)
 
         ipoib_dbg(priv, "bringing up interface\n");
 
-        if (!test_and_set_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags))
-                napi_enable(&priv->napi);
+        set_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags);
 
         if (ipoib_pkey_dev_delay_open(dev))
                 return 0;
@@ -143,7 +142,6 @@ err_stop:
         ipoib_ib_dev_stop(dev, 1);
 
 err_disable:
-        napi_disable(&priv->napi);
         clear_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags);
 
         return -EINVAL;
@@ -156,7 +154,6 @@ static int ipoib_stop(struct net_device *dev)
         ipoib_dbg(priv, "stopping interface\n");
 
         clear_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags);
-        napi_disable(&priv->napi);
 
         netif_stop_queue(dev);