net: napi_hash_del() returns a boolean status

napi_hash_del() will soon be used from both drivers (if they want)
or core networking stack.

Callers are responsibles to ensure an RCU grace period is respected
before freeing napi structure : napi_hash_del() can signal if
this RCU grace period is needed or not.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 838935d..e5c33b2 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -474,9 +474,10 @@ void napi_hash_add(struct napi_struct *napi);
  *     @napi: napi context
  *
  * Warning: caller must observe rcu grace period
- * before freeing memory containing @napi
+ * before freeing memory containing @napi, if
+ * this function returns true.
  */
-void napi_hash_del(struct napi_struct *napi);
+bool napi_hash_del(struct napi_struct *napi);
 
 /**
  *     napi_disable - prevent NAPI from scheduling

diff --git a/net/core/dev.c b/net/core/dev.c
index 02dfbd9..59dddac 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4760,14 +4760,18 @@ EXPORT_SYMBOL_GPL(napi_hash_add);
 /* Warning : caller is responsible to make sure rcu grace period
  * is respected before freeing memory containing @napi
  */
-void napi_hash_del(struct napi_struct *napi)
+bool napi_hash_del(struct napi_struct *napi)
 {
+       bool rcu_sync_needed = false;
+
        spin_lock(&napi_hash_lock);
 
-       if (test_and_clear_bit(NAPI_STATE_HASHED, &napi->state))
+       if (test_and_clear_bit(NAPI_STATE_HASHED, &napi->state)) {
+               rcu_sync_needed = true;
                hlist_del_rcu(&napi->napi_hash_node);
-
+       }
        spin_unlock(&napi_hash_lock);
+       return rcu_sync_needed;
 }
 EXPORT_SYMBOL_GPL(napi_hash_del);