netpoll: make __netpoll_cleanup non-block

Like the previous patch, slave_disable_netpoll() and __netpoll_cleanup()
may be called with read_lock() held too, so we should make them
non-block, by moving the cleanup and kfree() to call_rcu_bh() callbacks.

Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 32 insertions, 10 deletions

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 37cc854774a..dc17f1db147 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -878,6 +878,24 @@ static int __init netpoll_init(void)
 }
 core_initcall(netpoll_init);
 
+static void rcu_cleanup_netpoll_info(struct rcu_head *rcu_head)
+{
+        struct netpoll_info *npinfo =
+                        container_of(rcu_head, struct netpoll_info, rcu);
+
+        skb_queue_purge(&npinfo->arp_tx);
+        skb_queue_purge(&npinfo->txq);
+
+        /* we can't call cancel_delayed_work_sync here, as we are in softirq */
+        cancel_delayed_work(&npinfo->tx_work);
+
+        /* clean after last, unfinished work */
+        __skb_queue_purge(&npinfo->txq);
+        /* now cancel it again */
+        cancel_delayed_work(&npinfo->tx_work);
+        kfree(npinfo);
+}
+
 void __netpoll_cleanup(struct netpoll *np)
 {
         struct netpoll_info *npinfo;
@@ -903,20 +921,24 @@ void __netpoll_cleanup(struct netpoll *np)
                         ops->ndo_netpoll_cleanup(np->dev);
 
                 RCU_INIT_POINTER(np->dev->npinfo, NULL);
+                call_rcu_bh(&npinfo->rcu, rcu_cleanup_netpoll_info);
+        }
+}
+EXPORT_SYMBOL_GPL(__netpoll_cleanup);
 
-                /* avoid racing with NAPI reading npinfo */
-                synchronize_rcu_bh();
+static void rcu_cleanup_netpoll(struct rcu_head *rcu_head)
+{
+        struct netpoll *np = container_of(rcu_head, struct netpoll, rcu);
 
-                skb_queue_purge(&npinfo->arp_tx);
-                skb_queue_purge(&npinfo->txq);
-                cancel_delayed_work_sync(&npinfo->tx_work);
+        __netpoll_cleanup(np);
+        kfree(np);
+}
 
-                /* clean after last, unfinished work */
-                __skb_queue_purge(&npinfo->txq);
-                kfree(npinfo);
-        }
+void __netpoll_free_rcu(struct netpoll *np)
+{
+        call_rcu_bh(&np->rcu, rcu_cleanup_netpoll);
 }
-EXPORT_SYMBOL_GPL(__netpoll_cleanup);
+EXPORT_SYMBOL_GPL(__netpoll_free_rcu);
 
 void netpoll_cleanup(struct netpoll *np)
 {