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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