Re: [PATCH net-next v3] net: remove delay at device dismantle

From: Gao feng <redacted>
Date: Thu, 23 Aug 2012 12:33:03 +0800

于 2012年08月23日 11:19, Eric Dumazet 写道:

quoted

From: Eric Dumazet <edumazet@google.com>

I noticed extra one second delay in device dismantle, tracked down to
a call to dst_dev_event() while some call_rcu() are still in RCU queues.

These call_rcu() were posted by rt_free(struct rtable *rt) calls.

We then wait a little (but one second) in netdev_wait_allrefs() before
kicking again NETDEV_UNREGISTER.

As the call_rcu() are now completed, dst_dev_event() can do the needed
device swap on busy dst.

To solve this problem, add a new NETDEV_UNREGISTER_FINAL, called
after a rcu_barrier(), but outside of RTNL lock.

Use NETDEV_UNREGISTER_FINAL with care !

Change dst_dev_event() handler to react to NETDEV_UNREGISTER_FINAL

Also remove NETDEV_UNREGISTER_BATCH, as its not used anymore after
IP cache removal.

With help from Gao feng

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <redacted>
Cc: Mahesh Bandewar <redacted>
Cc: "Eric W. Biederman" <redacted>
Cc: Gao feng <redacted>

looks good to me, the lockdep warning message disappeared.

Applied, thanks everyone.