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    SubjectRe: [PATCH tip/core/rcu 05/13] net: add checking to rcu_dereference() primitives
    From
    2010/2/12 Eric Dumazet <eric.dumazet@gmail.com>:
    > Le jeudi 11 février 2010 à 16:00 -0800, Paul E. McKenney a écrit :
    [...]
    >> @@ -1654,12 +1654,12 @@ static struct dn_route *dn_rt_cache_get_first(struct seq_file *seq)
    >>
    >>       for(s->bucket = dn_rt_hash_mask; s->bucket >= 0; --s->bucket) {
    >>               rcu_read_lock_bh();
    >> -             rt = dn_rt_hash_table[s->bucket].chain;
    >> +             rt = rcu_dereference_bh(dn_rt_hash_table[s->bucket].chain);
    >>               if (rt)
    >>                       break;
    >>               rcu_read_unlock_bh();
    >>       }
    >> -     return rcu_dereference(rt);
    >> +     return rt;
    >>  }

    Isn't there a bug? Looks like data pointed to by rt should be
    protected by RCU, but the rcu_read_lock is withdrawn before access.

    Best Regards,
    Michał Mirosław
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