On Wed, 30 Mar 2011 18:05:01 +0800
Daniel J Blueman <daniel.blueman@xxxxxxxxx> wrote:
> The loop in fib_table_flush [1] calls trie_firstleaf() which
> RCU-dereferences a structure outside a RCU read critical section,
> generating a warning [2].
>
> Since trie_leaf_remove() uses rcu_assign_pointer(), which should be
> outside the RCU read critical section, is there any better solution
> than spitting up the loop, with the first half covered by a RCU read
> critical section lock?
>
> Daniel
>
> --- [1]
>
> int fib_table_flush(struct fib_table *tb)
> {
> struct trie *t = (struct trie *) tb->tb_data;
> struct leaf *l, *ll = NULL;
> int found = 0;
>
> for (l = trie_firstleaf(t); l; l = trie_nextleaf(l)) {
> found += trie_flush_leaf(l);
>
> if (ll && hlist_empty(&ll->list))
> trie_leaf_remove(t, ll);
> ll = l;
> }
>
> --- [2]
>
> ===================================================
> [ INFO: suspicious rcu_dereference_check() usage. ]
> ---------------------------------------------------
> net/ipv4/fib_trie.c:1777 invoked rcu_dereference_check() without protection!
>
> other info that might help us debug this:
>
> rcu_scheduler_active = 1, debug_locks = 1
> 3 locks held by kworker/u:5/51:
> #0: (netns){.+.+.+}, at: [<ffffffff8107b639>] process_one_work+0x149/0x470
> #1: (net_cleanup_work){+.+.+.}, at: [<ffffffff8107b639>]
> process_one_work+0x149/0x470
> #2: (net_mutex){+.+.+.}, at: [<ffffffff8157b4b0>] cleanup_net+0x80/0x1b0
>
> stack backtrace:
> Pid: 51, comm: kworker/u:5 Tainted: G W 2.6.39-rc1-350cd #1
> Call Trace:
> [<ffffffff81094cd4>] lockdep_rcu_dereference+0xa4/0xc0
> [<ffffffff8160aa23>] trie_firstleaf+0x93/0xa0
> [<ffffffff8156feb8>] ? __sk_free+0x148/0x1e0
> [<ffffffff8160d890>] fib_table_flush+0x20/0x1a0
> [<ffffffff81606da5>] ip_fib_net_exit+0x95/0xd0
> [<ffffffff81606e10>] fib_net_exit+0x30/0x40
> [<ffffffff8157ab8e>] ops_exit_list+0x2e/0x70
> [<ffffffff8157b52b>] cleanup_net+0xfb/0x1b0
> [<ffffffff8107b69a>] process_one_work+0x1aa/0x470
> [<ffffffff8107b639>] ? process_one_work+0x149/0x470
> [<ffffffff8157b430>] ? net_free+0x30/0x30
> [<ffffffff8107bd97>] worker_thread+0x157/0x3c0
> [<ffffffff816ea484>] ? preempt_schedule+0x44/0x60
> [<ffffffff8107bc40>] ? rescuer_thread+0x2e0/0x2e0
> [<ffffffff81080236>] kthread+0xb6/0xc0
> [<ffffffff81095f1d>] ? trace_hardirqs_on_caller+0x14d/0x190
> [<ffffffff816ef094>] kernel_thread_helper+0x4/0x10
> [<ffffffff810553f8>] ? finish_task_switch+0x78/0x110
> [<ffffffff816ed7c4>] ? retint_restore_args+0xe/0xe
> [<ffffffff81080180>] ? __init_kthread_worker+0x70/0x70
> [<ffffffff816ef090>] ? gs_change+0xb/0xb
The problem is that fib_net_exit is not calling rtnl_lock()
--
To unsubscribe from this list: send the line "unsubscribe linux-net" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
