From: Eric W. Biederman Date: Thu, 13 Oct 2011 22:25:23 +0000 (+0000) Subject: net: Move rcu_barrier from rollback_registered_many to netdev_run_todo. X-Git-Tag: v3.2-rc1~182^2~67 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=850a545bd8a41648445bfc5541afe36ca105b0b8;p=pandora-kernel.git net: Move rcu_barrier from rollback_registered_many to netdev_run_todo. This patch moves the rcu_barrier from rollback_registered_many (inside the rtnl_lock) into netdev_run_todo (just outside the rtnl_lock). This allows us to gain the full benefit of sychronize_net calling synchronize_rcu_expedited when the rtnl_lock is held. The rcu_barrier in rollback_registered_many was originally a synchronize_net but was promoted to be a rcu_barrier() when it was found that people were unnecessarily hitting the 250ms wait in netdev_wait_allrefs(). Changing the rcu_barrier back to a synchronize_net is therefore safe. Since we only care about waiting for the rcu callbacks before we get to netdev_wait_allrefs() it is also safe to move the wait into netdev_run_todo. This was tested by creating and destroying 1000 tap devices and observing /proc/lock_stat. /proc/lock_stat reports this change reduces the hold times of the rtnl_lock by a factor of 10. There was no observable difference in the amount of time it takes to destroy a network device. Signed-off-by: Eric W. Biederman Signed-off-by: David S. Miller --- Reading git-diff-tree failed