* [Patch net] net: explain the lockdep annotations for dev_uc_unsync()
@ 2020-06-26 18:25 Cong Wang
2020-06-29 4:38 ` David Miller
0 siblings, 1 reply; 2+ messages in thread
From: Cong Wang @ 2020-06-26 18:25 UTC (permalink / raw)
To: netdev; +Cc: Cong Wang, Taehee Yoo, Dmitry Vyukov
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 <ap420073@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
---
net/core/dev_addr_lists.c | 10 ++++++++++
1 file changed, 10 insertions(+)
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);
--
2.27.0
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Patch net] net: explain the lockdep annotations for dev_uc_unsync()
2020-06-26 18:25 [Patch net] net: explain the lockdep annotations for dev_uc_unsync() Cong Wang
@ 2020-06-29 4:38 ` David Miller
0 siblings, 0 replies; 2+ messages in thread
From: David Miller @ 2020-06-29 4:38 UTC (permalink / raw)
To: xiyou.wangcong; +Cc: netdev, ap420073, dvyukov
From: Cong Wang <xiyou.wangcong@gmail.com>
Date: Fri, 26 Jun 2020 11:25:27 -0700
> 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 <ap420073@gmail.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Applied.
^ permalink raw reply [flat|nested] 2+ messages in thread
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