Lighttpd

got this often in the dmesg.

------------[ cut here ]------------
WARNING: at net/ipv4/tcp_input.c:2539 tcp_ack+0x1c19/0x1db0()
Modules linked in: 3w_9xxx
Pid: 2893, comm: lighttpd Not tainted 2.6.25.4 #3

Call Trace:
<IRQ> <ffffffff8022fd94> warn_on_slowpath+0x64/0x90
<ffffffff80490470> bond_xmit_roundrobin+0xc0/0xd0
<ffffffff80521975> dev_queue_xmit+0xa5/0x310
<ffffffff8027e7d6> free_block+0x66/0x160
<ffffffff8027e4d3> cache_flusharray+0x63/0xe0
<ffffffff80546db6> tcp_enter_frto_loss+0x186/0x200
<ffffffff80549b49> tcp_ack+0x1c19/0x1db0
<ffffffff8054d123> tcp_rcv_established+0x563/0x7c0
<ffffffff8055312c> tcp_v4_do_rcv+0xdc/0x220
<ffffffff80554b12> tcp_v4_rcv+0x5a2/0x6b0
<ffffffff80537b87> ip_local_deliver+0x87/0x140
<ffffffff80537f2e> ip_rcv+0x2ee/0x560
<ffffffff805197a5> __alloc_skb+0x85/0x150
<ffffffff8049c401> sky2_poll+0x4f1/0xd70
<ffffffff80520efc> net_rx_action+0xbc/0x180
<ffffffff802358d9> __do_softirq+0x69/0xe0
<ffffffff8020c45c> call_softirq+0x1c/0x30
<ffffffff8020e935> do_softirq+0x35/0x70
<ffffffff8020ebb0> do_IRQ+0x80/0x100
<ffffffff8020b7e1> ret_from_intr+0x0/0xa
<EOI> <ffffffff80543edf> tcp_sendmsg+0x65f/0xbf0
<ffffffff80543e81> tcp_sendmsg+0x601/0xbf0
<ffffffff80511a00> sock_aio_write+0x110/0x120
<ffffffff80229263> __wake_up+0x43/0x70
<ffffffff80282219> do_sync_write+0xd9/0x120
<ffffffff80244460> autoremove_wake_function+0x0/0x30
<ffffffff80227433> set_next_entity+0x23/0x50
<ffffffff805ce1bd> thread_return+0x3e/0x4d1
<ffffffff80282b6a> vfs_write+0x15a/0x170
<ffffffff802831b3> sys_write+0x53/0x90
<ffffffff8020b2bb> system_call_after_swapgs+0x7b/0x80

---[ end trace 6b1f9e79512e4f31 ]---