From: Alexander Duyck <alexander.h.duyck@redhat.com>
To: Sabrina Dubroca <sd@queasysnail.net>, Scott Feldman <sfeldma@gmail.com>
Cc: netdev@vger.kernel.org
Subject: Re: suspicious RCU usage in fib_table_flush_external
Date: Tue, 10 Mar 2015 11:45:59 -0700 [thread overview]
Message-ID: <54FF3BE7.6070601@redhat.com> (raw)
In-Reply-To: <20150310183555.GB1743@kria>
On 03/10/2015 11:35 AM, Sabrina Dubroca wrote:
> I ran into this while deleting a netns with some routes:
>
> ===============================
> [ INFO: suspicious RCU usage. ]
> 4.0.0-rc2-00722-g8ac467e837a2-dirty #674 Not tainted
> -------------------------------
> net/ipv4/fib_trie.c:1606 suspicious rcu_dereference_protected() usage!
> other info that might help us debug this:
>
> rcu_scheduler_active = 1, debug_locks = 1
> 4 locks held by kworker/u4:1/50:
> #0: ("%s""netns"){.+.+.+}, at: [<ffffffff81086525>] process_one_work+0x155/0x880
> #1: (net_cleanup_work){+.+.+.}, at: [<ffffffff81086525>] process_one_work+0x155/0x880
> #2: (net_mutex){+.+.+.}, at: [<ffffffff81647cfd>] cleanup_net+0x7d/0x230
> #3: (&(&net->rules_mod_lock)->rlock){+.+...}, at: [<ffffffff81674ce4>] fib_rules_unregister+0x34/0x100
> stack backtrace:
> CPU: 1 PID: 50 Comm: kworker/u4:1 Not tainted 4.0.0-rc2-00722-g8ac467e837a2-dirty #674
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.7.5-20140617_173321-var-lib-archbuild-testing-x86_64-tobias 04/01/2014
> Workqueue: netns cleanup_net
> 0000000000000001 ffff88001dffbba8 ffffffff81835bd0 0000000000000011
> ffff88001dd95690 ffff88001dffbbd8 ffffffff810b5505 0000000000000001
> 0000000000000001 ffff88001da86270 ffff88001d528008 ffff88001dffbc08
> Call Trace:
> [<ffffffff81835bd0>] dump_stack+0x4c/0x6e
> [<ffffffff810b5505>] lockdep_rcu_suspicious+0xd5/0x110
> [<ffffffff81710421>] fib_table_flush_external+0xe1/0x130
> [<ffffffff81708808>] fib_flush_external+0x38/0x60
> [<ffffffff81719dee>] fib4_rule_delete+0x2e/0x30
> [<ffffffff81674d4b>] fib_rules_unregister+0x9b/0x100
> [<ffffffff8171a2a5>] fib4_rules_exit+0x15/0x20
> [<ffffffff817078ab>] ip_fib_net_exit+0x1b/0x120
> [<ffffffff817079e5>] fib_net_exit+0x35/0x40
>
>
>
> since fib_table_flush_external wants RTNL, should we just move
> rtnl_lock() before fib4_rules_exit in ip_fib_net_exit?
>
>
> diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
> index e067770235bf..ed94bc80eb78 100644
> --- a/net/ipv4/fib_frontend.c
> +++ b/net/ipv4/fib_frontend.c
> @@ -1126,11 +1126,12 @@ static void ip_fib_net_exit(struct net *net)
> {
> unsigned int i;
>
> + rtnl_lock();
> +
> #ifdef CONFIG_IP_MULTIPLE_TABLES
> fib4_rules_exit(net);
> #endif
>
> - rtnl_lock();
> for (i = 0; i < FIB_TABLE_HASHSZ; i++) {
> struct hlist_head *head = &net->ipv4.fib_table_hash[i];
> struct hlist_node *tmp;
>
This fix looks like it is probably correct. I'd recommend including a
note that it fixes 104616e74 ("switchdev: don't support custom ip rules,
for now"), and make sure to include a signed-off-by.
- Alex
next prev parent reply other threads:[~2015-03-10 18:46 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-10 18:35 suspicious RCU usage in fib_table_flush_external Sabrina Dubroca
2015-03-10 18:45 ` Alexander Duyck [this message]
2015-03-10 20:03 ` [PATCH net-next] fib_trie: call fib_table_flush_external under RTNL Sabrina Dubroca
2015-03-10 20:38 ` Alexander Duyck
2015-03-11 13:00 ` Jiri Pirko
2015-03-11 20:46 ` David Miller
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