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    net: remove delay at device dismantle · 0115e8e3
    Eric Dumazet 提交于
    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: NEric Dumazet <edumazet@google.com>
    Cc: Tom Herbert <therbert@google.com>
    Cc: Mahesh Bandewar <maheshb@google.com>
    Cc: "Eric W. Biederman" <ebiederm@xmission.com>
    Cc: Gao feng <gaofeng@cn.fujitsu.com>
    Signed-off-by: NDavid S. Miller <davem@davemloft.net>
    0115e8e3
dev.c 162.0 KB