netpoll: cleanup sparse warnings

With my recent commit I introduced two sparse warnings.  Looking closer there
were a few more in the same file, so I fixed them all up.  Basic rcu pointer
dereferencing suff.

I've validated these changes using CONFIG_PROVE_RCU while starting and stopping
netconsole repeatedly in bonded and non-bonded configurations

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: fengguang.wu@intel.com
CC: David Miller <davem@davemloft.net>
CC: eric.dumazet@gmail.com
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index c536474..bcfd4f4 100644 (file)
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -206,7 +206,7 @@ static void netpoll_poll_dev(struct net_device *dev)
         * the dev_open/close paths use this to block netpoll activity
         * while changing device state
         */
-       if (!mutex_trylock(&dev->npinfo->dev_lock))
+       if (!mutex_trylock(&ni->dev_lock))
                return;
 
        if (!dev || !netif_running(dev))
@@ -221,7 +221,7 @@ static void netpoll_poll_dev(struct net_device *dev)
 
        poll_napi(dev);
 
-       mutex_unlock(&dev->npinfo->dev_lock);
+       mutex_unlock(&ni->dev_lock);
 
        if (dev->flags & IFF_SLAVE) {
                if (ni) {
@@ -1056,7 +1056,7 @@ int __netpoll_setup(struct netpoll *np, struct net_device *ndev, gfp_t gfp)
                                goto free_npinfo;
                }
        } else {
-               npinfo = ndev->npinfo;
+               npinfo = rtnl_dereference(ndev->npinfo);
                atomic_inc(&npinfo->refcnt);
        }
 
@@ -1236,7 +1236,11 @@ void __netpoll_cleanup(struct netpoll *np)
        struct netpoll_info *npinfo;
        unsigned long flags;
 
-       npinfo = np->dev->npinfo;
+       /* rtnl_dereference would be preferable here but
+        * rcu_cleanup_netpoll path can put us in here safely without
+        * holding the rtnl, so plain rcu_dereference it is
+        */
+       npinfo = rtnl_dereference(np->dev->npinfo);
        if (!npinfo)
                return;