[B.A.T.M.A.N.] [PATCH] batman-adv: Don't remove interface with spinlock held

[B.A.T.M.A.N.] [PATCH] batman-adv: Don't remove interface with spinlock held

[Sven Eckelmann]

We call a lot of the netdevice code when holding if_list_lock which will
spin the whole time. This is not necessary because we only want to
protect the access to the list to be serialized. An extra queue can be
used which hold all interfaces which should be removed and then use that
queue without any locks for netdevice cleanup.

Signed-off-by: Sven Eckelmann <sven.eckelmann@gmx.de>
---
 batman-adv/hard-interface.c |   19 +++++++++++++------
 1 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/batman-adv/hard-interface.c b/batman-adv/hard-interface.c
index e22f0dd..bf98b90 100644
--- a/batman-adv/hard-interface.c
+++ b/batman-adv/hard-interface.c
@@ -469,9 +469,6 @@ static void hardif_remove_interface(struct batman_if *batman_if)
 		return;
 
 	batman_if->if_status = IF_TO_BE_REMOVED;
-
-	/* caller must take if_list_lock */
-	list_del_rcu(&batman_if->list);
 	sysfs_del_hardif(&batman_if->hardif_obj);
 	call_rcu(&batman_if->rcu, hardif_free_rcu);
 }
@@ -479,13 +476,21 @@ static void hardif_remove_interface(struct batman_if *batman_if)
 void hardif_remove_interfaces(void)
 {
 	struct batman_if *batman_if, *batman_if_tmp;
+	struct list_head if_list_queue;
+
+	INIT_LIST_HEAD(&if_list_queue);
 
-	rtnl_lock();
 	spin_lock(&if_list_lock);
 	list_for_each_entry_safe(batman_if, batman_if_tmp, &if_list, list) {
-		hardif_remove_interface(batman_if);
+		list_del_rcu(&batman_if->list);
+		list_add_tail(&batman_if->list, &if_list_queue);
 	}
 	spin_unlock(&if_list_lock);
+
+	rtnl_lock();
+	list_for_each_entry_safe(batman_if, batman_if_tmp, &if_list_queue, list) {
+		hardif_remove_interface(batman_if);
+	}
 	rtnl_unlock();
 }
 
@@ -512,8 +517,10 @@ static int hard_if_event(struct notifier_block *this,
 		break;
 	case NETDEV_UNREGISTER:
 		spin_lock(&if_list_lock);
-		hardif_remove_interface(batman_if);
+		list_del_rcu(&batman_if->list);
 		spin_unlock(&if_list_lock);
+
+		hardif_remove_interface(batman_if);
 		break;
 	case NETDEV_CHANGEMTU:
 		if (batman_if->soft_iface)
-- 
1.7.2.3

Re: [B.A.T.M.A.N.] [PATCH] batman-adv: Don't remove interface with spinlock held

[Marek Lindner]

On Sunday 21 November 2010 20:54:28 Sven Eckelmann wrote:
> We call a lot of the netdevice code when holding if_list_lock which will
> spin the whole time. This is not necessary because we only want to
> protect the access to the list to be serialized. An extra queue can be
> used which hold all interfaces which should be removed and then use that
> queue without any locks for netdevice cleanup.

Applied in revision 1867.

Thanks,
Marek