• WANG Cong's avatar
    net_sched: remove tc class reference counting · 143976ce
    WANG Cong authored
    For TC classes, their ->get() and ->put() are always paired, and the
    reference counting is completely useless, because:
    
    1) For class modification and dumping paths, we already hold RTNL lock,
       so all of these ->get(),->change(),->put() are atomic.
    
    2) For filter bindiing/unbinding, we use other reference counter than
       this one, and they should have RTNL lock too.
    
    3) For ->qlen_notify(), it is special because it is called on ->enqueue()
       path, but we already hold qdisc tree lock there, and we hold this
       tree lock when graft or delete the class too, so it should not be gone
       or changed until we release the tree lock.
    
    Therefore, this patch removes ->get() and ->put(), but:
    
    1) Adds a new ->find() to find the pointer to a class by classid, no
       refcnt.
    
    2) Move the original class destroy upon the last refcnt into ->delete(),
       right after releasing tree lock. This is fine because the class is
       already removed from hash when holding the lock.
    
    For those who also use ->put() as ->unbind(), just rename them to reflect
    this change.
    
    Cc: Jamal Hadi Salim <jhs@mojatatu.com>
    Signed-off-by: 's avatarCong Wang <xiyou.wangcong@gmail.com>
    Acked-by: 's avatarJiri Pirko <jiri@mellanox.com>
    Acked-by: 's avatarJamal Hadi Salim <jhs@mojatatu.com>
    Signed-off-by: 's avatarDavid S. Miller <davem@davemloft.net>
    143976ce