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Date: Thu, 02 Jul 2009 08:10:14 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: "Tantilov, Emil S" <emil.s.tantilov@...el.com> CC: NetDev <netdev@...r.kernel.org>, "Brandeburg, Jesse" <jesse.brandeburg@...el.com>, "Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>, Jiri Olsa <jolsa@...hat.com>, "David S. Miller" <davem@...emloft.net> Subject: Re: WARNING: at include/net/sock.h:417 udp_lib_unhash Tantilov, Emil S a écrit : > I see the following trace during netperf stress mixed UDP/TCP IPv4/6 traffic. This is on recent pulls from net-2.6 and net-next. > > [45197.989163] ------------[ cut here ]------------ > [45197.994309] WARNING: at include/net/sock.h:417 udp_lib_unhash+0x81/0xab() > [45197.994311] Hardware name: X7DA8 > [45197.994314] Modules linked in: e1000 [last unloaded: e1000] > [45197.994326] Pid: 7110, comm: netserver Tainted: G W 2.6.31-rc1-net-next-e1000-06250902 #8 > [45197.994331] Call Trace: > [45197.994336] [<ffffffff8135e0dc>] ? udp_lib_unhash+0x81/0xab > [45197.994344] [<ffffffff8103cac9>] warn_slowpath_common+0x77/0x8f > [45197.994349] [<ffffffff8103caf0>] warn_slowpath_null+0xf/0x11 > [45197.994352] [<ffffffff8135e0dc>] udp_lib_unhash+0x81/0xab > [45197.994357] [<ffffffff81301acb>] sk_common_release+0x2f/0xb4 > [45197.994364] [<ffffffff813a0256>] udp_lib_close+0x9/0xb > [45197.994369] [<ffffffff81364259>] inet_release+0x58/0x5f > [45197.994374] [<ffffffff8138c8bd>] inet6_release+0x30/0x35 > [45197.994383] [<ffffffff812ff273>] sock_release+0x1a/0x6c > [45197.994386] [<ffffffff812ff763>] sock_close+0x22/0x26 > [45197.994392] [<ffffffff810c69a0>] __fput+0xf0/0x18c > [45197.994395] [<ffffffff810c6d00>] fput+0x15/0x19 > [45197.994399] [<ffffffff810c3c3e>] filp_close+0x5c/0x67 > [45197.994404] [<ffffffff810c3cc4>] sys_close+0x7b/0xb6 > [45197.994412] [<ffffffff8100baeb>] system_call_fastpath+0x16/0x1b > [45197.994418] ---[ end trace 5acab6fc0afdaaa3 ]--- > > Emil-- Thanks for this report Emil. I could not find a recent change in this area in last kernels. If struct sk is hashed (sk_hashed() true), then sk_refcnt was incremented in sk_nulls_add_node_rcu(), thus its value should be >= 2. Maybe we have a missing memory barrier somewhere or a list corruption. 1) Could you try CONFIG_DEBUG_LIST=y ? 2) Could you give model of cpu, since it reminds me the ongoing discussion raised by Jiri Olsa. CPU1 does an atomic_inc(&sk->sk_refcnt) : refcnt changes from 1 to 2 then CPU2 does an atomic_read(&sk->sk_refcnt) and reads 1 instead of 2 David, maybe this test is not safe and if we really want to do a check we need to use a stronger atomic function. If you can reproduce this problem easily could you try following patch ? Thank you diff --git a/include/net/sock.h b/include/net/sock.h index 352f06b..96ab278 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -393,8 +393,9 @@ static __inline__ int sk_del_node_init(struct sock *sk) if (rc) { /* paranoid for a while -acme */ - WARN_ON(atomic_read(&sk->sk_refcnt) == 1); - __sock_put(sk); + int res = atomic_dec_return(&sk->sk_refcnt); + + WARN_ON(res <= 0); } return rc; } @@ -413,9 +414,9 @@ static __inline__ int sk_nulls_del_node_init_rcu(struct sock *sk) int rc = __sk_nulls_del_node_init_rcu(sk); if (rc) { - /* paranoid for a while -acme */ - WARN_ON(atomic_read(&sk->sk_refcnt) == 1); - __sock_put(sk); + int res = atomic_dec_return(&sk->sk_refcnt); + + WARN_ON(res <= 0); } return rc; } -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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