Re: oops in tcp_xmit_retransmit_queue() w/ v2.6.32.15

From: Lennart Schulte
Date: Fri Jul 16 2010 - 08:25:51 EST

On 16.07.2010 14:02, Ilpo Järvinen wrote:

[ 2754.413150] NULL head, pkts 0
[ 2754.413156] Errors caught so far 1
Thanks for reporting the results.

Could you post the oops too or double check do the timestamps really match
(and there wasn't more "Errors caught" prints in between)? Since this
condition doesn't seem to crash the kernel as also send_head should be
NULL, which saves the day here exiting the loop (unless send head would
too be corrupt).
I can try to do some more testing, perhaps then I will get other results. But until now I've always gotten something like above.

With the debug patch the kernel doesn't crash, but I have an oops from a run before the patch:

[ 3214.498061] BUG: unable to handle kernel NULL pointer dereference at (null)
[ 3214.498085] IP: [<c12657dc>] tcp_xmit_retransmit_queue+0x4c/0x2b0
[ 3214.498121] *pdpt = 00000002cf6fa001
[ 3214.498130] Thread overran stack, or stack corrupted
[ 3214.498138] Oops: 0000 [#1] SMP
[ 3214.498154] last sysfs file: /sys/kernel/uevent_seqnum
[ 3214.498161] Modules linked in: tcp_ancr tcp_ncr
[ 3214.498174]
[ 3214.498180] Pid: 0, comm: swapper Not tainted (2.6.31.9-pae-um-wolff #79)
[ 3214.498188] EIP: 0061:[<c12657dc>] EFLAGS: 00010246 CPU: 0
[ 3214.498196] EIP is at tcp_xmit_retransmit_queue+0x4c/0x2b0
[ 3214.498203] EAX: c6da2900 EBX: c6da2880 ECX: 00000000 EDX: e50c512e
[ 3214.498211] ESI: 00000000 EDI: 0000051b EBP: c6da2900 ESP: c13d5cf0
[ 3214.498219] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0069
[ 3214.498227] Process swapper (pid: 0, ti=c13d4000 task=c13e7a20 task.ti=c13d4000)
[ 3214.498236] Stack:
[ 3214.498240] c1005a0b 00000001 00000000 e50c512e c7804300 00000013 c6da2880 0000051b
[ 3214.498264] <0> e50c512e c1260709 c6cbf840 c6d42000 c1031826 c1288bbd c6da2900 c6e09320
[ 3214.498290] <0> c6e09300 00000000 00000000 00000001 e50c512d e521a346 e50c512e 00000000
[ 3214.498318] Call Trace:
[ 3214.498329] [<c1005a0b>] ? xen_restore_fl_direct_end+0x0/0x1
[ 3214.498339] [<c1260709>] ? tcp_ack+0x7f9/0x10d0
[ 3214.498350] [<c1031826>] ? local_bh_enable+0x56/0x80
[ 3214.498359] [<c1288bbd>] ? ipt_do_table+0x2dd/0x590
[ 3214.498369] [<c1261eef>] ? tcp_rcv_state_process+0x41f/0x970
[ 3214.498378] [<c1267e7f>] ? tcp_v4_do_rcv+0x8f/0x1e0
[ 3214.498387] [<c1269ccd>] ? tcp_v4_rcv+0x68d/0x7d0
[ 3214.498397] [<c124d5f0>] ? ip_local_deliver_finish+0x0/0x1e0
[ 3214.498406] [<c124d687>] ? ip_local_deliver_finish+0x97/0x1e0
[ 3214.498416] [<c124d5f0>] ? ip_local_deliver_finish+0x0/0x1e0
[ 3214.498425] [<c124d3eb>] ? ip_rcv_finish+0x13b/0x340
[ 3214.498434] [<c124d2b0>] ? ip_rcv_finish+0x0/0x340
[ 3214.498442] [<c124d8c0>] ? ip_rcv+0x0/0x2e0
[ 3214.498452] [<c1211037>] ? netif_receive_skb+0x2f7/0x4c0
[ 3214.498468] [<c1213fe0>] ? process_backlog+0x70/0xb0
[ 3214.498476] [<c1213d98>] ? net_rx_action+0xe8/0x1a0
[ 3214.498486] [<c103116d>] ? __do_softirq+0x8d/0x120
[ 3214.498494] [<c100360d>] ? xen_mc_flush+0xed/0x1a0
[ 3214.498504] [<c1057891>] ? move_native_irq+0x11/0x50
[ 3214.498513] [<c1031238>] ? do_softirq+0x38/0x40
[ 3214.498523] [<c11930e2>] ? xen_evtchn_do_upcall+0x142/0x160
[ 3214.498534] [<c10087d7>] ? xen_do_upcall+0x7/0xc
[ 3214.498543] [<c10013a7>] ? hypercall_page+0x3a7/0x1010
[ 3214.498552] [<c100520f>] ? xen_safe_halt+0xf/0x20
[ 3214.498560] [<c100349c>] ? xen_idle+0x1c/0x30
[ 3214.498569] [<c1006bba>] ? cpu_idle+0x3a/0x60
[ 3214.498578] [<c141692a>] ? start_kernel+0x26a/0x300
[ 3214.498616] [<c1416280>] ? unknown_bootoption+0x0/0x1c0
[ 3214.498630] [<c141938e>] ? xen_start_kernel+0x3be/0x3e0
[ 3214.498637] Code: 00 00 8b b3 a0 03 00 00 85 f6 0f 84 53 02 00 00 8b 46 3c 8d ab 80 00 00 00 8b 93 04 04 00 00 39 c2 89 54 24 0c 0f 89 1c 02 00 00 <8b> 06 0f 18 00 90 39 ee 0f 84 30 01 00 00 39 b3 28 01 00 00 8d
[ 3214.498820] EIP: [<c12657dc>] tcp_xmit_retransmit_queue+0x4c/0x2b0 SS:ESP 0069:c13d5cf0
[ 3214.498836] CR2: 0000000000000000
[ 3214.498846] ---[ end trace 709a97adf87834a7 ]---
[ 3214.498852] Kernel panic - not syncing: Fatal exception in interrupt
[ 3214.498862] Pid: 0, comm: swapper Tainted: G D 2.6.31.9-pae-um-wolff #79
[ 3214.498870] Call Trace:
[ 3214.498878] [<c102c896>] ? panic+0x46/0x100
[ 3214.498904] [<c100b428>] ? oops_end+0x98/0xa0
[ 3214.498922] [<c1019eff>] ? no_context+0x11f/0x1b0
[ 3214.498930] [<c101a516>] ? do_page_fault+0x66/0x240
[ 3214.498939] [<c101a4b0>] ? do_page_fault+0x0/0x240
[ 3214.498947] [<c101a23f>] ? bad_area_nosemaphore+0xf/0x20
[ 3214.498955] [<c1308b7e>] ? error_code+0x66/0x6c
[ 3214.498963] [<c101a4b0>] ? do_page_fault+0x0/0x240
[ 3214.498972] [<c12657dc>] ? tcp_xmit_retransmit_queue+0x4c/0x2b0
[ 3214.498982] [<c1005a0b>] ? xen_restore_fl_direct_end+0x0/0x1
[ 3214.498991] [<c1260709>] ? tcp_ack+0x7f9/0x10d0
[ 3214.498999] [<c1031826>] ? local_bh_enable+0x56/0x80
[ 3214.499009] [<c1288bbd>] ? ipt_do_table+0x2dd/0x590
[ 3214.499017] [<c1261eef>] ? tcp_rcv_state_process+0x41f/0x970
[ 3214.499025] [<c1267e7f>] ? tcp_v4_do_rcv+0x8f/0x1e0
[ 3214.499034] [<c1269ccd>] ? tcp_v4_rcv+0x68d/0x7d0
[ 3214.499044] [<c124d5f0>] ? ip_local_deliver_finish+0x0/0x1e0
[ 3214.499053] [<c124d687>] ? ip_local_deliver_finish+0x97/0x1e0
[ 3214.499063] [<c124d5f0>] ? ip_local_deliver_finish+0x0/0x1e0
[ 3214.499072] [<c124d3eb>] ? ip_rcv_finish+0x13b/0x340
[ 3214.499079] [<c124d2b0>] ? ip_rcv_finish+0x0/0x340
[ 3214.499087] [<c124d8c0>] ? ip_rcv+0x0/0x2e0
[ 3214.499101] [<c1211037>] ? netif_receive_skb+0x2f7/0x4c0
[ 3214.499115] [<c1213fe0>] ? process_backlog+0x70/0xb0
[ 3214.499123] [<c1213d98>] ? net_rx_action+0xe8/0x1a0
[ 3214.499131] [<c103116d>] ? __do_softirq+0x8d/0x120
[ 3214.499143] [<c100360d>] ? xen_mc_flush+0xed/0x1a0
[ 3214.499152] [<c1057891>] ? move_native_irq+0x11/0x50
[ 3214.499160] [<c1031238>] ? do_softirq+0x38/0x40
[ 3214.499174] [<c11930e2>] ? xen_evtchn_do_upcall+0x142/0x160
[ 3214.499188] [<c10087d7>] ? xen_do_upcall+0x7/0xc
[ 3214.499195] [<c10013a7>] ? hypercall_page+0x3a7/0x1010
[ 3214.499203] [<c100520f>] ? xen_safe_halt+0xf/0x20
[ 3214.499214] [<c100349c>] ? xen_idle+0x1c/0x30
[ 3214.499223] [<c1006bba>] ? cpu_idle+0x3a/0x60
[ 3214.499231] [<c141692a>] ? start_kernel+0x26a/0x300
[ 3214.499239] [<c1416280>] ? unknown_bootoption+0x0/0x1c0
[ 3214.499247] [<c141938e>] ? xen_start_kernel+0x3be/0x3e0
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