[uml-devel] UML Network Related Crashing

["Dave Humphreys (Bob)" <dave@bob-the-boat.me.uk>]

I have experimented further with the network related crashing problem that I 
have had for some time with UML.

I have been using 3.8.0-rc3 UML kernels with Debian root filesystems.

I have been running two UML instances side-by-side on the same host and 
communicationg via mcast networking.

My current testing uses a 64 bit UML from which i copy data using rsync 
(because this is how I found the original problem).

I seem to be able to copy from 64 bit to 64 bit, but when I copy from 64 bit 
to 32 bit I get a crash.

The oringinal problem that I had was a 32 bit UML that I access via a real 
ethernet network connection and it crashes occasionally. i find that I can 
crash it regularly bu rsyncing data from it.

I can therefore say that the problem does not seems to occur when using both 
mcast and tuntap networking; and when the bulk of the network traffic is 
received or transmitted.

It does appear to be a problem with the 32 bit variant and not the 64 bit.

As an aside, I also find that I can crash the 32 bit UML by rsyncing between 
the UML and the host via a hostfs mount. I have a copy of the crash output for 
this if it is of any interest. I mention this in case there could be a link, 
but my current principle concern is to cure the networking problem.

Here is what happens when it crashes:


 map/@DEB1-32:~# rsync --archive --delete --progress 10.0.10.30:/var/imap/ 
/var/imap/
The authenticity of host '10.0.10.30 (10.0.10.30)' can't be established.
RSA key fingerprint is b8:5d:e0:69:bc:61:d9:88:e4:12:80:84:c9:94:81:2f.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '10.0.10.30' (RSA) to the list of known hosts.
receiving incremental file list
./
.bash_history
        1970 100%    1.88MB/s    0:00:00 (xfer#1, to-check=1005/1007)
config/
config/annotations.db
         144 100%    3.70kB/s    0:00:00 (xfer#2, to-check=1356/1362)
config/deliver.db
           0   0%    0.00kB/s    0:00:00  ------------[ cut here ]------------
WARNING: at net/core/skbuff.c:573 skb_release_head_state+0x60/0x6c()
Modules linked in:

2367232c:  [<082050f7>] dump_stack+0x16/0x1a

23672340:  [<08070515>] warn_slowpath_common+0x48/0x5e

23672358:  [<08070540>] warn_slowpath_null+0x15/0x19

23672368:  [<081a1f93>] skb_release_head_state+0x60/0x6c

23672380:  [<081a3705>] __kfree_skb+0xe/0x72

2367238c:  [<081a3791>] consume_skb+0x28/0x2b

23672398:  [<080615e2>] uml_net_start_xmit+0xd5/0xdf

236723b8:  [<081ac85b>] dev_hard_start_xmit+0x26c/0x374

236723e4:  [<081bac2c>] sch_direct_xmit+0x35/0x10d

23672408:  [<081acb0b>] dev_queue_xmit+0xd6/0x203

23672438:  [<081c519a>] ip_finish_output+0x272/0x2d9

23672470:  [<081c5f9b>] ip_output+0x4b/0x50

23672484:  [<081c5a18>] ip_local_out+0x1d/0x23

23672494:  [<081c5ccd>] ip_queue_xmit+0x2af/0x2f7

236724d0:  [<081d70a7>] tcp_transmit_skb+0x697/0x6fb

23672520:  [<081d8e65>] tcp_send_ack+0xcc/0xd4

23672534:  [<081cfabb>] __tcp_ack_snd_check+0x42/0x7a

23672548:  [<081d47f1>] tcp_rcv_established+0x36e/0x594

23672570:  [<081da56f>] tcp_v4_do_rcv+0x5d/0x18e

2367259c:  [<081dcbcc>] tcp_v4_rcv+0x6a0/0x6f7

236725d4:  [<081c2195>] ip_local_deliver+0x11d/0x1b8

236725f0:  [<081c25f7>] ip_rcv+0x3c7/0x410

23672608:  [<081aa94e>] __netif_receive_skb+0x34a/0x3e4

23672650:  [<081aaa47>] process_backlog+0x5f/0xe1

2367266c:  [<081aadd5>] net_rx_action+0x49/0x121

23672690:  [<080757c9>] __do_softirq+0x84/0x129

236726b8:  [<080758d0>] do_softirq+0x30/0x3c

236726c8:  [<08075a6a>] irq_exit+0x35/0x6d

236726d4:  [<0805af16>] do_IRQ+0x24/0x34

236726e4:  [<0805af68>] sigio_handler+0x42/0x56

236726f8:  [<08068db7>] sig_handler_common+0x79/0x8c

23672978:  [<08068d2d>] unblock_signals+0x48/0x59

23672984:  [<0808accf>] finish_task_switch.isra.63+0x1b/0x51

2367299c:  [<08208103>] __schedule+0x234/0x28a

236729c0:  [<08208250>] schedule+0x57/0x59

236729cc:  [<082078ce>] schedule_hrtimeout_range_clock+0x33/0x128

23672a18:  [<082079d6>] schedule_hrtimeout_range+0x13/0x15

23672a30:  [<080d497f>] poll_schedule_timeout+0x2a/0x51

23672a4c:  [<080d5136>] do_select+0x4cd/0x504

23672d3c:  [<080d539b>] core_sys_select+0x22e/0x24b

23672e7c:  [<080d5416>] sys_select+0x5e/0x86

23672eb0:  [<0805d742>] handle_syscall+0x6a/0x80

23672ef4:  [<0806aee8>] userspace+0x362/0x488

23672fe4:  [<0805b3d6>] fork_handler+0x56/0x5b

23672ffc:  [<00746f6f>] 0x746f6f

---[ end trace 8e9ba3f2efd7a2c6 ]---
------------[ cut here ]------------
WARNING: at kernel/softirq.c:160 local_bh_enable+0x2f/0x83()

Modules linked in:
236723f4:  [<082050f7>] dump_stack+0x16/0x1a

23672408:  [<08070515>] warn_slowpath_common+0x48/0x5e
23672420:  [<08070540>] warn_slowpath_null+0x15/0x19
23672430:  [<0807598e>] local_bh_enable+0x2f/0x83
23672444:  [<081c51b1>] ip_finish_output+0x289/0x2d9
23672470:  [<081c5f9b>] ip_output+0x4b/0x50
23672484:  [<081c5a18>] ip_local_out+0x1d/0x23
23672494:  [<081c5ccd>] ip_queue_xmit+0x2af/0x2f7
236724d0:  [<081d70a7>] tcp_transmit_skb+0x697/0x6fb
23672520:  [<081d8e65>] tcp_send_ack+0xcc/0xd4
23672534:  [<081cfabb>] __tcp_ack_snd_check+0x42/0x7a
23672548:  [<081d47f1>] tcp_rcv_established+0x36e/0x594
23672570:  [<081da56f>] tcp_v4_do_rcv+0x5d/0x18e
2367259c:  [<081dcbcc>] tcp_v4_rcv+0x6a0/0x6f7
236725d4:  [<081c2195>] ip_local_deliver+0x11d/0x1b8
236725f0:  [<081c25f7>] ip_rcv+0x3c7/0x410
23672608:  [<081aa94e>] __netif_receive_skb+0x34a/0x3e4
23672650:  [<081aaa47>] process_backlog+0x5f/0xe1
2367266c:  [<081aadd5>] net_rx_action+0x49/0x121
23672690:  [<080757c9>] __do_softirq+0x84/0x129
236726b8:  [<080758d0>] do_softirq+0x30/0x3c
236726c8:  [<08075a6a>] irq_exit+0x35/0x6d
236726d4:  [<0805af16>] do_IRQ+0x24/0x34
236726e4:  [<0805af68>] sigio_handler+0x42/0x56
236726f8:  [<08068db7>] sig_handler_common+0x79/0x8c
23672978:  [<08068d2d>] unblock_signals+0x48/0x59
23672984:  [<0808accf>] finish_task_switch.isra.63+0x1b/0x51
2367299c:  [<08208103>] __schedule+0x234/0x28a
236729c0:  [<08208250>] schedule+0x57/0x59
236729cc:  [<082078ce>] schedule_hrtimeout_range_clock+0x33/0x128
23672a18:  [<082079d6>] schedule_hrtimeout_range+0x13/0x15
23672a30:  [<080d497f>] poll_schedule_timeout+0x2a/0x51
23672a4c:  [<080d5136>] do_select+0x4cd/0x504
23672d3c:  [<080d539b>] core_sys_select+0x22e/0x24b
23672e7c:  [<080d5416>] sys_select+0x5e/0x86
23672eb0:  [<0805d742>] handle_syscall+0x6a/0x80
23672ef4:  [<0806aee8>] userspace+0x362/0x488
23672fe4:  [<0805b3d6>] fork_handler+0x56/0x5b
23672ffc:  [<00746f6f>] 0x746f6f

---[ end trace 8e9ba3f2efd7a2c7 ]---
huh, entered softirq 3 NET_RX 081aad8c preempt_count 00000100, exited with 
fffffe01?

EIP: 0023:[<080d9e01>] CPU: 0 Tainted: G        W    ESP: 002b:23672a44 
EFLAGS: 00010202
    Tainted: G        W   
EAX: 00082a40 EBX: 23672ac4 ECX: 00fffffe EDX: 00000003
ESI: 00000005 EDI: 23672d54 EBP: 23672a50 DS: 002b ES: 002b
082a4750:  [<0806d29a>] show_regs+0xc0/0xc6
082a477c:  [<0805ceef>] segv+0x57/0x218
082a481c:  [<0805d102>] segv_handler+0x52/0x5d
082a4848:  [<08068db7>] sig_handler_common+0x79/0x8c
082a4ac8:  [<08068ea5>] sig_handler+0x34/0x43
082a4ad4:  [<08068b3a>] hard_handler+0x5a/0x88
082a4afc:  [<ffffe410>] 0xffffe410

Kernel panic - not syncing: Segfault with no mm
082a474c:  [<082050f7>] dump_stack+0x16/0x1a
082a4760:  [<08205181>] panic+0x67/0x149
082a4778:  [<0805cef9>] segv+0x61/0x218
082a481c:  [<0805d102>] segv_handler+0x52/0x5d
082a4848:  [<08068db7>] sig_handler_common+0x79/0x8c
082a4ac8:  [<08068ea5>] sig_handler+0x34/0x43
082a4ad4:  [<08068b3a>] hard_handler+0x5a/0x88
082a4afc:  [<ffffe410>] 0xffffe410


EIP: 0000:[<00000000>] CPU: 0 Tainted: G        W    EFLAGS: 00000000
    Tainted: G        W   
EAX: 00000000 EBX: 00000000 ECX: 00000000 EDX: 00000000
ESI: 00000000 EDI: 00000000 EBP: 00000000 DS: 0000 ES: 0000
082a46bc:  [<0806d29a>] show_regs+0xc0/0xc6
082a46e8:  [<0805d32b>] panic_exit+0x20/0x36
082a46fc:  [<08088c3b>] notifier_call_chain+0x20/0x4b
082a4724:  [<08088c7d>] __atomic_notifier_call_chain+0x17/0x19
082a4734:  [<08088c94>] atomic_notifier_call_chain+0x15/0x17
082a4750:  [<08205199>] panic+0x7f/0x149
082a4778:  [<0805cef9>] segv+0x61/0x218
082a481c:  [<0805d102>] segv_handler+0x52/0x5d
082a4848:  [<08068db7>] sig_handler_common+0x79/0x8c
082a4ac8:  [<08068ea5>] sig_handler+0x34/0x43
082a4ad4:  [<08068b3a>] hard_handler+0x5a/0x88
082a4afc:  [<ffffe410>] 0xffffe410

Terminated
 

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