Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161810AbXECGvk (ORCPT ); Thu, 3 May 2007 02:51:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1161803AbXECGvk (ORCPT ); Thu, 3 May 2007 02:51:40 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:34597 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1161802AbXECGvi (ORCPT ); Thu, 3 May 2007 02:51:38 -0400 Date: Thu, 3 May 2007 09:51:36 +0300 (EEST) From: "=?ISO-8859-1?Q?Ilpo_J=E4rvinen?=" X-X-Sender: ijjarvin@kivilampi-30.cs.helsinki.fi To: Michal Piotrowski , David Miller cc: Netdev , LKML Subject: Re: kernel BUG at include/net/tcp.h:739 In-Reply-To: <4638F14E.6000803@googlemail.com> Message-ID: References: <4638F14E.6000803@googlemail.com> MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="-696243703-1270442657-1178175096=:3607" Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5786 Lines: 119 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---696243703-1270442657-1178175096=:3607 Content-Type: TEXT/PLAIN; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT On Wed, 2 May 2007, Michal Piotrowski wrote: > Please take a look at this bug > > [15236.638092] kernel BUG at /mnt/md0/devel/linux-git/include/net/tcp.h:739! > [15236.644860] invalid opcode: 0000 [#1] > [15236.648514] PREEMPT SMP > [15236.651075] Modules linked in: ipt_MASQUERADE iptable_nat nf_nat autofs4 af_packet nf_conntrack_netbios_ns ipt_REJECT nf_conntrack_ipv4 xt_state nf_conntrack nfnetlink iptable_filter ip_tables ip6t_REJECT xt_tcpudp ip6table_filter ip6_tables x_tables ipv6 binfmt_misc thermal processor fan container nvram snd_intel8x0 snd_ac97_codec ac97_bus snd_seq_dummy snd_seq_oss snd_seq_midi_event snd_seq snd_seq_device snd_pcm_oss snd_mixer_oss snd_pcm evdev snd_timer snd intel_agp i2c_i801 soundcore agpgart snd_page_alloc ide_cd cdrom rtc unix > [15236.698898] CPU: 0 > [15236.698899] EIP: 0060:[] Not tainted VLI > [15236.698900] EFLAGS: 00010206 (2.6.21-gdc87c398 #169) > [15236.711580] EIP is at tcp_ack+0xc54/0x16a0 > [15236.715664] eax: 00000017 ebx: 00000000 ecx: 00000003 edx: 0000010e > [15236.722433] esi: d5bc1254 edi: 0000010e ebp: c0462e18 esp: c0462da8 > [15236.729202] ds: 007b es: 007b fs: 00d8 gs: 0000 ss: 0068 > [15236.735019] Process swapper (pid: 0, ti=c0462000 task=c03f14e0 task.ti=c0427000) > [15236.742219] Stack: 00000000 00000000 00000000 00000198 00000100 00000000 00000000 00000018 > [15236.750698] 3b4d5775 0ffef1c0 3b4d79ad 00000001 00000018 00000006 3b4d79ad 003f14e0 > [15236.759178] 00000006 0000082a d4b9cde0 00e4059a 0000000c 00000000 00000000 0130204a > [15236.767649] Call Trace: > [15236.770286] [] show_trace_log_lvl+0x1a/0x2f > [15236.775438] [] show_stack_log_lvl+0x9d/0xa5 > [15236.780590] [] show_registers+0x1ed/0x32c > [15236.785569] [] die+0x118/0x22f > [15236.789588] [] do_trap+0x79/0x91 > [15236.793781] [] do_invalid_op+0x97/0xa1 > [15236.798501] [] error_code+0x7c/0x84 > [15236.802960] [] tcp_rcv_established+0x568/0x645 > [15236.808354] [] tcp_v4_do_rcv+0x2b/0x32c > [15236.813144] [] tcp_v4_rcv+0x7f9/0x86b > [15236.817777] [] ip_local_deliver+0x170/0x235 > [15236.822928] [] ip_rcv+0x4f3/0x52c > [15236.827199] [] netif_receive_skb+0x1b9/0x252 > [15236.832437] [] skge_poll+0x47a/0x545 > [15236.836967] [] net_rx_action+0x9f/0x192 > [15236.841772] [] __do_softirq+0x6d/0xea > [15236.846407] [] do_softirq+0x64/0xd1 > [15236.850867] ======================= > [15236.854437] Code: 69 42 c0 f7 d0 64 8b 15 04 00 00 00 8b 04 90 ff 80 a4 00 00 00 8b 9e 70 05 00 00 89 d8 03 86 74 05 00 00 3b 86 8c 04 00 00 76 04 <0f> 0b eb fe 89 86 90 04 00 00 8a 86 88 03 00 00 84 c0 75 3c 83 > [15236.874343] EIP: [] tcp_ack+0xc54/0x16a0 SS:ESP 0068:c0462da8 > > l *0xc02f798b > 0xc02f798b is in tcp_ack (/mnt/md0/devel/linux-git/include/net/tcp.h:739). > 734 (tp->snd_cwnd >> 2))); > 735 } > 736 > 737 static inline void tcp_sync_left_out(struct tcp_sock *tp) > 738 { > 739 BUG_ON(tp->sacked_out + tp->lost_out > tp->packets_out); > 740 tp->left_out = tp->sacked_out + tp->lost_out; > 741 } > 742 > 743 extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh); > > Caused by commit 34588b4c046c34773e5a1a962da7b78b05c4d1bd I think I found the reason: tcp_clean_rtx_queue without SACK it does not decrement sacked_out but tcp_reset_reno_sack/remove_reno_sack is being called later in tcp_fastretrans_alert. Before that, tcp_sync_left_out is being called, at least by tcp_fastretrans_alert itself, which sees sacked_out that includes also segments that are no longer in window (this also explains why the original code did not do the reduction in the non-SACK case). Also tcp_process_frto calls tcp_sync_left_out, so it would also lead to the same problem. Here is a change that ignores this trap without SACK. However, it would be useful to trap this without SACK too as S+L skb causes potentially a negative packets in flight (= large one) disturbing cwnd compares. [PATCH] [TCP]: Use S+L catcher only with SACK for now TCP has a transitional state when SACK is not in use during which this invariant is temporarily broken. Without SACK, tcp_clean_rtx_queue does not decrement sacked_out. Therefore calls to tcp_sync_left_out before sacked_out is again corrected by tcp_fastretrans_alert can trigger this trap as sacked_out still has couple of segments that are already out of window. Signed-off-by: Ilpo J?rvinen --- include/net/tcp.h | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index ef8f9d4..e22b4f0 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -736,7 +736,8 @@ static inline __u32 tcp_current_ssthresh static inline void tcp_sync_left_out(struct tcp_sock *tp) { - BUG_ON(tp->sacked_out + tp->lost_out > tp->packets_out); + BUG_ON(tp->rx_opt.sack_ok && + (tp->sacked_out + tp->lost_out > tp->packets_out)); tp->left_out = tp->sacked_out + tp->lost_out; } -- 1.4.2 ---696243703-1270442657-1178175096=:3607-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/