Latest working kernel version: unknown
Earliest failing kernel version: unknown
Distribution: gentoo x86-64
Hardware Environment: 
#1 2xQuadra opteron, mcp55 nvidia, forcedeth gigabit network
#2 2xQuadra xeon, intel 5000 series, e1000e gigabit network

Software Environment:
nginx+haproxy

Problem Description:
after 5-10 hours network load I have this backtrace in dmesg:

------------[ cut here ]------------
WARNING: at net/ipv4/tcp_input.c:2569 tcp_ack+0xcd9/0x1f90()
Modules linked in:                                          
Pid: 0, comm: swapper Tainted: G        W 2.6.26.5 #5       

Call Trace:
 <IRQ>  [<ffffffff80234504>] warn_on_slowpath+0x64/0xc0
 [<ffffffff8040f778>] dev_queue_xmit+0xc8/0x3b0
 [<ffffffff8049a5d9>] _spin_lock_bh+0x9/0x20
 [<ffffffff80426f09>] __nf_ct_refresh_acct+0x29/0xf0
 [<ffffffff80286c3f>] add_partial+0x1f/0x80
 [<ffffffff8023ec74>] lock_timer_base+0x34/0x70
 [<ffffffff8044fa6e>] tcp_init_tso_segs+0x2e/0x50
 [<ffffffff8044fab7>] tcp_snd_test+0x27/0x170
 [<ffffffff8044fc53>] tcp_may_send_now+0x53/0x80
 [<ffffffff8044a779>] tcp_ack+0xcd9/0x1f90
 [<ffffffff8044eda7>] tcp_rcv_established+0x587/0xdd0
 [<ffffffff80455fad>] tcp_v4_do_rcv+0xdd/0x240
 [<ffffffff8045670e>] tcp_v4_rcv+0x5fe/0x810
 [<ffffffff80437e20>] ip_rcv_finish+0x0/0x360
 [<ffffffff80438506>] ip_local_deliver_finish+0xa6/0x1f0
 [<ffffffff80437f9a>] ip_rcv_finish+0x17a/0x360
 [<ffffffff804383c6>] ip_rcv+0x246/0x2e0
 [<ffffffff803af093>] e1000_receive_skb+0x53/0x1f0
 [<ffffffff803af334>] e1000_clean_rx_irq+0x104/0x360
 [<ffffffff803ad661>] e1000_clean+0xe1/0x210
 [<ffffffff8040d842>] net_rx_action+0xe2/0x220
 [<ffffffff8023a3ca>] __do_softirq+0x7a/0xf0
 [<ffffffff8020c89c>] call_softirq+0x1c/0x30
 [<ffffffff8020e8e5>] do_softirq+0x35/0x70
 [<ffffffff8020e9d1>] do_IRQ+0x81/0x100
 [<ffffffff80212a80>] mwait_idle+0x0/0x50
 [<ffffffff8020bc21>] ret_from_intr+0x0/0xa
 <EOI>  [<ffffffff80209410>] default_idle+0x0/0x50
 [<ffffffff80212abc>] mwait_idle+0x3c/0x50
 [<ffffffff8020a720>] cpu_idle+0x60/0xa0

---[ end trace 8bcf9abf1f67c29e ]---

Steps to reproduce:

sysctl.conf:
net.ipv4.ip_forward = 0                         
net.ipv4.conf.default.log_martians = 1          
net.ipv4.conf.all.log_martians = 1              
net.ipv4.conf.default.send_redirects = 0        
net.ipv4.ip_dynaddr = 0                         
net.ipv4.tcp_ecn = 0                            
net.ipv4.conf.default.rp_filter = 1             
net.ipv4.conf.all.rp_filter = 1                 
net.ipv4.tcp_syncookies = 1                                                 
net.ipv4.tcp_tw_recycle = 1                                                 
net.ipv4.tcp_tw_reuse = 1                                                   
net.ipv4.tcp_timestamps = 1
net.ipv4.tcp_synack_retries = 5
net.ipv4.conf.all.accept_source_route = 0
net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.secure_redirects = 0
net.ipv4.conf.default.secure_redirects = 0
net.ipv4.icmp_echo_ignore_broadcasts = 1
kernel.panic = 5
net.ipv4.tcp_max_syn_backlog = 14096
net.ipv4.tcp_synack_retries = 5
net.ipv4.tcp_syn_retries = 5
net.ipv4.tcp_fin_timeout = 5
net.ipv4.tcp_keepalive_time = 7200
net.core.optmem_max = 655360
net.core.netdev_max_backlog = 40000
net.core.somaxconn = 40000
net.ipv4.tcp_max_tw_buckets = 580000
net.core.rmem_default = 262141
net.core.wmem_default = 262141
net.core.rmem_max = 25165824
net.core.wmem_max = 25165824
net.ipv4.tcp_rmem =  4096 262141 25165824
net.ipv4.tcp_wmem =  4096 262141 25165824
net.ipv4.tcp_no_metrics_save = 1
net.ipv4.tcp_mtu_probing = 1
net.ipv4.tcp_sack = 1
net.ipv4.tcp_dsack = 1

iptables rules-save:
# Generated by iptables-save v1.4.1.1 on Wed Sep 10 22:43:18 2008
*nat                                                             
:PREROUTING ACCEPT [72621:4808515]                               
:POSTROUTING ACCEPT [191712:11662324]                            
:OUTPUT ACCEPT [191712:11662324]                                 
COMMIT                                                           
# Completed on Wed Sep 10 22:43:18 2008                          
# Generated by iptables-save v1.4.1.1 on Wed Sep 10 22:43:18 2008
*mangle
:PREROUTING ACCEPT [16013862:7579402727]
:INPUT ACCEPT [16013694:7579367635]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [9821064:22219526681]
:POSTROUTING ACCEPT [9821064:22219526681]
COMMIT
# Completed on Wed Sep 10 22:43:18 2008
# Generated by iptables-save v1.4.1.1 on Wed Sep 10 22:43:18 2008
*filter
:INPUT DROP [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [12899:31686989]
:black - [0:0]
:block - [0:0]
:ddos - [0:0]
:synflood - [0:0]
:white - [0:0]
[18730:7560663] -A INPUT -j white
[0:0] -A INPUT -p icmp -j ACCEPT
[66:3612] -A INPUT -j block
[66:3612] -A INPUT -p tcp -m multiport --dports 80,22,443 -j ACCEPT
[66:3612] -A block -j black
[66:3612] -A block -j ddos
[19:1128] -A block -p tcp -m state --state NEW -j synflood
[0:0] -A synflood -p tcp -m multiport --dports ! 80,443 -m recent --set --name BRUTE --rsource
[0:0] -A synflood -p tcp -m multiport --dports ! 80,443 -m recent --update --seconds 10 --hitcount 15 --name BRUTE --rsource -j DROP
[2332:1074647] -A white -i lo -j ACCEPT
[16285:6479584] -A white -m state --state RELATED,ESTABLISHED -j ACCEPT
[47:2820] -A white -s 192.168.0.1/32 -j ACCEPT
[0:0] -A white -s 192.168.0.2/32 -j ACCEPT
COMMIT
# Completed on Wed Sep 10 22:43:18 2008