• Herbert Xu's avatar
    [IPV4]: Kill redundant rcu_dereference on fa_info · 1371e37d
    Herbert Xu authored
    This patch kills a redundant rcu_dereference on fa->fa_info in fib_trie.c.
    As this dereference directly follows a list_for_each_entry_rcu line, we
    have already taken a read barrier with respect to getting an entry from
    the list.
    
    This read barrier guarantees that all values read out of fa are valid.
    In particular, the contents of structure pointed to by fa->fa_info is
    initialised before fa->fa_info is actually set (see fn_trie_insert);
    the setting of fa->fa_info itself is further separated with a write
    barrier from the insertion of fa into the list.
    
    Therefore by taking a read barrier after obtaining fa from the list
    (which is given by list_for_each_entry_rcu), we can be sure that
    fa->fa_info contains a valid pointer, as well as the fact that the
    data pointed to by fa->fa_info is itself valid.
    Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
    Acked-by: default avatarPaul E. McKenney <paulmck@us.ibm.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@mandriva.com>
    1371e37d
fib_trie.c 58.1 KB