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Message-ID: <CAK6E8=fZnQXNjO_dh7sALOfsa=BL7qKzzZkzQrRtX3k9ehBZPA@mail.gmail.com>
Date: Wed, 9 Oct 2013 10:33:04 -0700
From: Yuchung Cheng <ycheng@...gle.com>
To: dormando <dormando@...ia.net>
Cc: Michele Baldessari <michele@...syn.org>,
Russell King - ARM Linux <linux@....linux.org.uk>,
netdev <netdev@...r.kernel.org>,
Neal Cardwell <ncardwell@...gle.com>,
Nandita Dukkipati <nanditad@...gle.com>
Subject: Re: IPv6 kernel warning
On Tue, Oct 8, 2013 at 1:53 PM, Yuchung Cheng <ycheng@...gle.com> wrote:
>
> On Tue, Oct 8, 2013 at 11:24 AM, dormando <dormando@...ia.net> wrote:
> > On Mon, 7 Oct 2013, Yuchung Cheng wrote:
> >
> >> On Mon, Oct 7, 2013 at 12:56 PM, dormando <dormando@...ia.net> wrote:
> >> > On Mon, 7 Oct 2013, Yuchung Cheng wrote:
> >> >
> >> >> On Mon, Oct 7, 2013 at 11:13 AM, dormando <dormando@...ia.net> wrote:
> >> >> >
> >> >> > > >
> >> >> > > > there's been multiple reports about this one:
> >> >> > > > https://bugzilla.redhat.com/show_bug.cgi?id=989251
> >> >> > > > http://bugzilla.kernel.org/show_bug.cgi?id=60779
> >> >> > > >
> >> >> > > > Could you try Yuchung's debug patch?
> >> >> > > > http://www.spinics.net/lists/netdev/msg250193.html
> >> >> > > Yes it looks like the same bug. Please try that patch to help identify
> >> >> > > this elusive bug.
> >> >> > >
> >> >> >
> >> >> > Hi!
> >> >> >
> >> >> > We get this one a few times a day in production. Here's a warning with
> >> >> > your debug trace in the line immediately following:
> >> >> > (I censored a few things)
> >> >> >
> >> >> > [125311.721950] ------------[ cut here ]------------
> >> >> > [125311.721961] WARNING: at net/ipv4/tcp_input.c:2776 tcp_fastretrans_alert+0xb58/0xc80()
> >> >> > [125311.721962] Modules linked in: bridge ip_vs macvlan coretemp crc32_pclmul ghash_clmulni_intel gpio_ich ipmi_watchdog microcode ipmi_devintf sb_edac lpc_ich edac_core mfd_core ipmi_si ipmi_msghandler iptable_nat nf_nat_ipv4 nf_nat ixgbe igb mdio i2c_algo_bit ptp pps_core
> >> >> > [125311.721981] CPU: 11 PID: 0 Comm: swapper/11 Not tainted 3.10.13 #1
> >> >> > [125311.721982] Hardware name: Supermicro XXXXXXXXXXX, BIOS 1.1 10/03/2012
> >> >> > [125311.721984] ffffffff81a82007 ffff88407fc63958 ffffffff816bb9cc ffff88407fc63998
> >> >> > [125311.721986] ffffffff8104b940 00ff8840ad904f82 ffff883b8a165b00 0000000000004120
> >> >> > [125311.721989] 0000000000000001 0000000000000019 0000000000000000 ffff88407fc639a8
> >> >> > [125311.721991] Call Trace:
> >> >> > [125311.721992] <IRQ> [<ffffffff816bb9cc>] dump_stack+0x19/0x1d
> >> >> > [125311.722002] [<ffffffff8104b940>] warn_slowpath_common+0x70/0xa0
> >> >> > [125311.722005] [<ffffffff8104b98a>] warn_slowpath_null+0x1a/0x20
> >> >> > [125311.722007] [<ffffffff81616db8>] tcp_fastretrans_alert+0xb58/0xc80
> >> >> > [125311.722011] [<ffffffff8161891f>] tcp_ack+0x6df/0xe90
> >> >> > [125311.722016] [<ffffffff8164e0ca>] ? ipt_do_table+0x22a/0x680
> >> >> > [125311.722018] [<ffffffff816194b3>] ? tcp_validate_incoming+0x63/0x320
> >> >> > [125311.722021] [<ffffffff8161a55c>] tcp_rcv_established+0x2cc/0x810
> >> >> > [125311.722023] [<ffffffff81622c84>] tcp_v4_do_rcv+0x254/0x4f0
> >> >> > [125311.722025] [<ffffffff816245ac>] tcp_v4_rcv+0x5fc/0x750
> >> >> > [125311.722027] [<ffffffff815ffa00>] ? ip_rcv+0x350/0x350
> >> >> > [125311.722032] [<ffffffff815df3ad>] ? nf_hook_slow+0x7d/0x160
> >> >> > [125311.722034] [<ffffffff815ffa00>] ? ip_rcv+0x350/0x350
> >> >> > [125311.722036] [<ffffffff815fface>] ip_local_deliver_finish+0xce/0x250
> >> >> > [125311.722037] [<ffffffff815ffc9c>] ip_local_deliver+0x4c/0x80
> >> >> > [125311.722039] [<ffffffff815ff329>] ip_rcv_finish+0x119/0x360
> >> >> > [125311.722040] [<ffffffff815ff8e0>] ip_rcv+0x230/0x350
> >> >> > [125311.722046] [<ffffffff815b4067>] __netif_receive_skb_core+0x477/0x600
> >> >> > [125311.722049] [<ffffffff815b4217>] __netif_receive_skb+0x27/0x70
> >> >> > [125311.722051] [<ffffffff815b4354>] process_backlog+0xf4/0x1e0
> >> >> > [125311.722053] [<ffffffff815b4b45>] net_rx_action+0xf5/0x250
> >> >> > [125311.722056] [<ffffffff81053a5f>] __do_softirq+0xef/0x270
> >> >> > [125311.722058] [<ffffffff81053cb5>] irq_exit+0x95/0xa0
> >> >> > [125311.722062] [<ffffffff816c8f26>] do_IRQ+0x66/0xe0
> >> >> > [125311.722065] [<ffffffff816bf62a>] common_interrupt+0x6a/0x6a
> >> >> > [125311.722065] <EOI> [<ffffffff8100abf1>] ? default_idle+0x21/0xc0
> >> >> > [125311.722082] [<ffffffff8100a54f>] arch_cpu_idle+0xf/0x20
> >> >> > [125311.722086] [<ffffffff8108f353>] cpu_startup_entry+0xb3/0x230
> >> >> > [125311.722091] [<ffffffff816b439e>] start_secondary+0x1dc/0x1e3
> >> >> > [125311.722093] ---[ end trace e77cd5ba583fcbe9 ]---
> >> >> > [125311.722096] 355.355.1.355:22496 F0x4120 S1 s7 IF25+17-1-24f0 ur57 rr3 rt0 um0 hs23120 nxt23120
> >> >> >
> >> >> > It's been happening with all 3.10 kernels, and the one above is .13 as
> >> >> > stated in the trace.
> >> >>
> >> >> Thanks! could you post the output of `sysctl -a |grep tcp`?
> >> >>
> >> >> I suspect tcp_process_tlp_ack() should not revert state to Open
> >> >> directly, but calling tcp_try_keep_open() instead, similar to all the
> >> >> undo processing in the tcp_fastretrans_alert(): after
> >> >> tcp_end_cwnd_reduction(), the process (E) falls back to check other
> >> >> stats before moving to CA_Open.
> >> >>
> >> >>
> >> >> index 9c62257..9012b42 100644
> >> >> --- a/net/ipv4/tcp_input.c
> >> >> +++ b/net/ipv4/tcp_input.c
> >> >> @@ -3314,7 +3314,7 @@ static void tcp_process_tlp_ack(struct sock *sk, u32 ack,
> >> >> tcp_init_cwnd_reduction(sk, true);
> >> >> tcp_set_ca_state(sk, TCP_CA_CWR);
> >> >> tcp_end_cwnd_reduction(sk);
> >> >> - tcp_set_ca_state(sk, TCP_CA_Open);
> >> >> + tcp_try_keep_open(sk);
> >> >> NET_INC_STATS_BH(sock_net(sk),
> >> >> LINUX_MIB_TCPLOSSPROBERECOVERY);
> >> >> }
> >> >>
> >> >
> >> > Should I apply this and see if the warning stops?
Hi Dormando,
Could you try this patch to make sure it fixes the warning (with
sysctl net.ipv4.early_retrans=3)?
> >> I'd like to hear what the authors of TLP think. In the mean time could
> >> you help us collect more evidence by disabling TLP with
> >> sysctl net.ipv4.tcp_early_retrans=2
> >> and see if the problem still occurs? (it should not).
> >>
> >> thanks
> >
> > Box hasn't had a warning in the last 24ish hours. A neighboring machine
> > with the default tcp_early_retrans setting has had 5-6 in the same
> > timeframe.
> >
> > Is this a harmful situation to the socket in any way, or is it just
> > informational weirdness?
> It should be fairly harmless. The ack that triggers the warning should
> set the TCP back to the good (non-Open) state, but it's still good to
> get rid of.
Download attachment "0001-tcp-fix-incorrect-ca_state-in-tail-loss-probe.patch" of type "application/octet-stream" (1356 bytes)
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