From e8280338c778a3f81477624267c9fa47f931477b Mon Sep 17 00:00:00 2001 From: Cong Wang Date: Fri, 26 Jun 2020 11:25:27 -0700 Subject: net: explain the lockdep annotations for dev_uc_unsync() The lockdep annotations for dev_uc_unsync() and dev_mc_unsync() are not easy to understand, so add some comments to explain why they are correct. Similar for the rest netif_addr_lock_bh() cases, they don't need nested version. Cc: Taehee Yoo Cc: Dmitry Vyukov Signed-off-by: Cong Wang Signed-off-by: David S. Miller --- net/core/dev_addr_lists.c | 10 ++++++++++ 1 file changed, 10 insertions(+) (limited to 'net/core/dev_addr_lists.c') diff --git a/net/core/dev_addr_lists.c b/net/core/dev_addr_lists.c index 6393ba930097..54cd568e7c2f 100644 --- a/net/core/dev_addr_lists.c +++ b/net/core/dev_addr_lists.c @@ -690,6 +690,15 @@ void dev_uc_unsync(struct net_device *to, struct net_device *from) if (to->addr_len != from->addr_len) return; + /* netif_addr_lock_bh() uses lockdep subclass 0, this is okay for two + * reasons: + * 1) This is always called without any addr_list_lock, so as the + * outermost one here, it must be 0. + * 2) This is called by some callers after unlinking the upper device, + * so the dev->lower_level becomes 1 again. + * Therefore, the subclass for 'from' is 0, for 'to' is either 1 or + * larger. + */ netif_addr_lock_bh(from); netif_addr_lock_nested(to); __hw_addr_unsync(&to->uc, &from->uc, to->addr_len); @@ -911,6 +920,7 @@ void dev_mc_unsync(struct net_device *to, struct net_device *from) if (to->addr_len != from->addr_len) return; + /* See the above comments inside dev_uc_unsync(). */ netif_addr_lock_bh(from); netif_addr_lock_nested(to); __hw_addr_unsync(&to->mc, &from->mc, to->addr_len); -- cgit v1.2.3