From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: WARNING: at include/net/sock.h:417 udp_lib_unhash Date: Tue, 07 Jul 2009 09:21:47 +0200 Message-ID: <4A52F78B.6020503@gmail.com> References: <4A4C4F46.2070701@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "Tantilov, Emil S" , NetDev , "Brandeburg, Jesse" , "Kirsher, Jeffrey T" , Jiri Olsa , "David S. Miller" To: Emil S Tantilov Return-path: Received: from gw1.cosmosbay.com ([212.99.114.194]:58339 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754049AbZGGHWK (ORCPT ); Tue, 7 Jul 2009 03:22:10 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Emil S Tantilov a =C3=A9crit : > On Wed, Jul 1, 2009 at 11:10 PM, Eric Dumazet= wrote: >> Tantilov, Emil S a =C3=A9crit : >>> 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+0x= 81/0xab() >>> [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] [] ? udp_lib_unhash+0x81/0xab >>> [45197.994344] [] warn_slowpath_common+0x77/0x8f >>> [45197.994349] [] warn_slowpath_null+0xf/0x11 >>> [45197.994352] [] udp_lib_unhash+0x81/0xab >>> [45197.994357] [] sk_common_release+0x2f/0xb4 >>> [45197.994364] [] udp_lib_close+0x9/0xb >>> [45197.994369] [] inet_release+0x58/0x5f >>> [45197.994374] [] inet6_release+0x30/0x35 >>> [45197.994383] [] sock_release+0x1a/0x6c >>> [45197.994386] [] sock_close+0x22/0x26 >>> [45197.994392] [] __fput+0xf0/0x18c >>> [45197.994395] [] fput+0x15/0x19 >>> [45197.994399] [] filp_close+0x5c/0x67 >>> [45197.994404] [] sys_close+0x7b/0xb6 >>> [45197.994412] [] 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 increm= ented >> in sk_nulls_add_node_rcu(), thus its value should be >=3D 2. >> >> Maybe we have a missing memory barrier somewhere or a list corruptio= n. >> >> 1) Could you try CONFIG_DEBUG_LIST=3Dy ? > I am running a test with this option now. Sorry for the delayed > response, I was out last week. >=20 >> 2) Could you give model of cpu, since it reminds me the ongoing disc= ussion raised by Jiri Olsa. >=20 > processor : 0 > vendor_id : GenuineIntel > cpu family : 6 > model : 23 > model name : Intel(R) Xeon(R) CPU E5450 @ 3.00GHz > stepping : 6 > cpu MHz : 2999.790 > cache size : 6144 KB > physical id : 0 > siblings : 4 > core id : 0 > cpu cores : 4 > apicid : 0 > initial apicid : 0 > fpu : yes > fpu_exception : yes > cpuid level : 10 > wp : yes > flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmo= v > pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx > lm constant_tsc arch_perfmon pebs bts rep_good pni dtes64 monitor > ds_cpl vmx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 lahf_lm tpr_shadow > vnmi flexpriority > bogomips : 5999.58 > clflush size : 64 >=20 > 2 quad core Xeons, I only included the output from the first to reduc= e clutter. >=20 >> 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 che= ck >> we need to use a stronger atomic function. >> >> If you can reproduce this problem easily could you try following pat= ch ? >=20 > It varies from few minutes to hours, but it does reproduce > consistently in my tests so far. I will try your patch once I manage > to get a trace with CONFIG_DEBUG_LIST >=20 Eventually, could you also use following debug/quick&dirty patch ? diff --git a/include/net/sock.h b/include/net/sock.h index 352f06b..548f822 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -376,6 +376,7 @@ static __inline__ int __sk_del_node_init(struct soc= k *sk) =20 static inline void sock_hold(struct sock *sk) { + WARN_ON(atomic_read(&sk->sk_refcnt) =3D=3D 0); atomic_inc(&sk->sk_refcnt); } =20 @@ -385,6 +386,7 @@ static inline void sock_hold(struct sock *sk) static inline void __sock_put(struct sock *sk) { atomic_dec(&sk->sk_refcnt); + WARN_ON(atomic_read(&sk->sk_refcnt) =3D=3D 0); } =20 static __inline__ int sk_del_node_init(struct sock *sk)