[Xen-devel] xennet: skb rides the rocket messages in domU dmesg

[Mark Hurenkamp <mark.hurenkamp@xxxxxxxxx>]

Hi,


On my home server i am running Xen-4.0.1-rc1 with a recent xen/next kernel,
and a pvm domU with the same kernel, and 4 tuners passed through.
Because the mythtv backend domain would sometimes become unstable, i 
decided
to split up my mythtv backend into 3 seperate virtual machines, one master
backend with the database, and 2 slave backends with the tuners.
One of the slave backends has a cx23885 based dvb tuner card, the other 
slave
backend runs 3 ivtv based tuners.
To keep consistency with old recording data, and since i would like to 
have all
recordings in a single volume, i tried to use an nfs mount of the 
recordings volume
from the dom0 to mount on all backends. This resulted in a very unstable 
system,
to the point where my most important slave backend became unusable.
So i tried it the other way, have the slave backends each mount their own
recordings volume as a block device via xen, and for backwards 
compatibility mount
the volume which holds the old recordings via nfs on the master backend.

Now i see many "xennet: skb rides the rocket" messages appear in the 
(pv) slave
backend which exports the recordings volume to the master backend. These
messages i did not see when there was only a single mythtv backend.
(both the dom0 as well as the mythtv domUs are ubuntu lucid server based)
Overall the system seems to perform ok, and the messages are not causing the
system to become unusable or more unstable, so it is not a major issue.

Note that both the master backend, and the slave backend which exports the
volume, are paravirtualised domains. The slave backend has the following
xen config:

kernel = '/boot/vmlinuz-2.6.32m5'
ramdisk = '/boot/initrd.img-2.6.32m5'
extra = 'root=/dev/xvda1 ro console=hvc0 noirqdebug iommu=soft 
swiotlb=force'
maxmem = '1000'
memory = '500'
device_model='/usr/lib/xen/bin/qemu-dm'
serial='pty'
disk = [
    'phy:/dev/vm/tilnes-lucid,hda,w',
    'phy:/dev/mythtv/recordings,hdb,w',
]
boot='c'
name = 'tilnes'
vif = [ 'mac=aa:20:00:00:01:72, bridge=loc' ]
vfb = [ 'vnc=1,vnclisten=0.0.0.0,vncdisplay=5' ]

usb=1
usbdevice='tablet'
monitor=1
pci = [
    '0000:08:02.0',
    '0000:09:08.0',
    '0000:09:09.0',
    ]
vcpus=8


The messagedump i see (this is only 1 example, my dmesg is full of these):

xennet: skb rides the rocket: 20 frags
Pid: 3237, comm: nfsd Tainted: G      D    2.6.32m5 #9
Call Trace:
<IRQ>  [<ffffffffa005e2d4>] xennet_start_xmit+0x75/0x678 [xen_netfront]
 [<ffffffff8100eff2>] ? check_events+0x12/0x20
 [<ffffffff8136bd3a>] ? rcu_read_unlock+0x0/0x1e
 [<ffffffff8100efdf>] ? xen_restore_fl_direct_end+0x0/0x1
 [<ffffffff81076983>] ? lock_release+0x1e0/0x1ed
 [<ffffffff8136ee0e>] dev_hard_start_xmit+0x236/0x2e1
 [<ffffffff8138114e>] sch_direct_xmit+0x68/0x16f
 [<ffffffff8136f240>] dev_queue_xmit+0x274/0x3de
 [<ffffffff8136f130>] ? dev_queue_xmit+0x164/0x3de
 [<ffffffff8139cf30>] ? dst_output+0x0/0xd
 [<ffffffff8139e16d>] ip_finish_output2+0x1df/0x222
 [<ffffffff8139e218>] ip_finish_output+0x68/0x6a
 [<ffffffff8139e503>] ip_output+0x9c/0xa0
 [<ffffffff8139e5a2>] ip_local_out+0x20/0x24
 [<ffffffff8139ebfe>] ip_queue_xmit+0x309/0x37a
 [<ffffffff8100e871>] ? xen_force_evtchn_callback+0xd/0xf
 [<ffffffff8100eff2>] ? check_events+0x12/0x20
 [<ffffffff8100e871>] ? xen_force_evtchn_callback+0xd/0xf
 [<ffffffff8100eff2>] ? check_events+0x12/0x20
 [<ffffffff813b012a>] tcp_transmit_skb+0x648/0x686
 [<ffffffff813b2654>] tcp_write_xmit+0x808/0x8f7
 [<ffffffff8100eff2>] ? check_events+0x12/0x20
 [<ffffffff813af7e2>] ? tcp_established_options+0x2e/0xa9
 [<ffffffff813b279e>] __tcp_push_pending_frames+0x2a/0x58
 [<ffffffff813ac124>] tcp_data_snd_check+0x24/0xea
 [<ffffffff813ae464>] tcp_rcv_established+0xdd/0x6d4
 [<ffffffff8100eff2>] ? check_events+0x12/0x20
 [<ffffffff813b535b>] tcp_v4_do_rcv+0x1ba/0x375
 [<ffffffff8100efdf>] ? xen_restore_fl_direct_end+0x0/0x1
 [<ffffffff813b62d1>] ? tcp_v4_rcv+0x2b3/0x6b7
 [<ffffffff813b6474>] tcp_v4_rcv+0x456/0x6b7
 [<ffffffff8139ad27>] ? ip_local_deliver_finish+0x0/0x235
 [<ffffffff8139ae9b>] ip_local_deliver_finish+0x174/0x235
 [<ffffffff8139ad6b>] ? ip_local_deliver_finish+0x44/0x235
 [<ffffffff8139afce>] ip_local_deliver+0x72/0x7c
 [<ffffffff8139a89d>] ip_rcv_finish+0x3cd/0x3fb
 [<ffffffff8139ab84>] ip_rcv+0x2b9/0x2f9
 [<ffffffff813ec764>] ? packet_rcv_spkt+0xd6/0xe1
 [<ffffffff8136e065>] netif_receive_skb+0x445/0x46f
 [<ffffffff810c0b92>] ? free_hot_page+0x3a/0x3f
 [<ffffffffa005f41d>] xennet_poll+0xaf4/0xc7b [xen_netfront]
 [<ffffffff8136e7ac>] net_rx_action+0xab/0x1df
 [<ffffffff81076983>] ? lock_release+0x1e0/0x1ed
 [<ffffffff81053842>] __do_softirq+0xe0/0x1a2
 [<ffffffff8109e984>] ? handle_level_irq+0xd1/0xda
 [<ffffffff8126a152>] ? __xen_evtchn_do_upcall+0x12e/0x163
 [<ffffffff81012cac>] call_softirq+0x1c/0x30
 [<ffffffff8101428d>] do_softirq+0x41/0x81
 [<ffffffff81053694>] irq_exit+0x36/0x78
 [<ffffffff8126a646>] xen_evtchn_do_upcall+0x37/0x47
 [<ffffffff81012cfe>] xen_do_hypervisor_callback+0x1e/0x30
<EOI>  [<ffffffff8111dc4a>] ? __bio_add_page+0xee/0x212
 [<ffffffff8111df9b>] ? bio_alloc+0x10/0x1f
 [<ffffffff811217e1>] ? mpage_alloc+0x25/0x7d
 [<ffffffff8111dd9f>] ? bio_add_page+0x31/0x33
 [<ffffffff81121dde>] ? do_mpage_readpage+0x3d3/0x488
 [<ffffffff810bba3b>] ? add_to_page_cache_locked+0xcc/0x108
 [<ffffffff81121fbb>] ? mpage_readpages+0xcb/0x10f
 [<ffffffff81159aee>] ? ext3_get_block+0x0/0xf9
 [<ffffffff81159aee>] ? ext3_get_block+0x0/0xf9
 [<ffffffff81157bbc>] ? ext3_readpages+0x18/0x1a
 [<ffffffff810c387b>] ? __do_page_cache_readahead+0x140/0x1cd
 [<ffffffff8100eff2>] ? check_events+0x12/0x20
 [<ffffffff8100efdf>] ? xen_restore_fl_direct_end+0x0/0x1
 [<ffffffff810c3924>] ? ra_submit+0x1c/0x20
 [<ffffffff810c3d1c>] ? ondemand_readahead+0x1de/0x1f1
 [<ffffffff810c3dc3>] ? page_cache_sync_readahead+0x17/0x1c
 [<ffffffff81118790>] ? __generic_file_splice_read+0xf0/0x41a
 [<ffffffff8100eff2>] ? check_events+0x12/0x20
 [<ffffffff811c0c07>] ? rcu_read_unlock+0x0/0x1e
 [<ffffffff8100efdf>] ? xen_restore_fl_direct_end+0x0/0x1
 [<ffffffff81076983>] ? lock_release+0x1e0/0x1ed
 [<ffffffff811c0c23>] ? rcu_read_unlock+0x1c/0x1e
 [<ffffffff811c16e2>] ? avc_has_perm_noaudit+0x3b5/0x3c7
 [<ffffffff810ec8eb>] ? check_object+0x170/0x1a9
 [<ffffffff8100e871>] ? xen_force_evtchn_callback+0xd/0xf
 [<ffffffff8111770d>] ? spd_release_page+0x0/0x14
 [<ffffffff811c4d62>] ? selinux_file_permission+0x57/0xae
 [<ffffffff81118afe>] ? generic_file_splice_read+0x44/0x72
 [<ffffffff8100eff2>] ? check_events+0x12/0x20
 [<ffffffff811171d4>] ? do_splice_to+0x6c/0x79
 [<ffffffff8100eff2>] ? check_events+0x12/0x20
 [<ffffffff811178ed>] ? splice_direct_to_actor+0xc2/0x1a1
 [<ffffffff8100efdf>] ? xen_restore_fl_direct_end+0x0/0x1
 [<ffffffffa01a0b53>] ? nfsd_direct_splice_actor+0x0/0x12 [nfsd]
 [<ffffffffa01a0a44>] ? nfsd_vfs_read+0x276/0x385 [nfsd]
 [<ffffffffa01a115a>] ? nfsd_read+0xa1/0xbf [nfsd]
 [<ffffffffa00de128>] ? svc_xprt_enqueue+0x22b/0x238 [sunrpc]
 [<ffffffffa01a7cbf>] ? nfsd3_proc_read+0xe2/0x121 [nfsd]
 [<ffffffffa00d6551>] ? cache_put+0x2d/0x2f [sunrpc]
 [<ffffffffa019c36f>] ? nfsd_dispatch+0xec/0x1c7 [nfsd]
 [<ffffffffa00d2e99>] ? svc_process+0x436/0x637 [sunrpc]
 [<ffffffffa01a4418>] ? exp_readlock+0x10/0x12 [nfsd]
 [<ffffffffa019c8c0>] ? nfsd+0xf3/0x13e [nfsd]
 [<ffffffffa019c7cd>] ? nfsd+0x0/0x13e [nfsd]
 [<ffffffff8106601d>] ? kthread+0x7a/0x82
 [<ffffffff81012baa>] ? child_rip+0xa/0x20
 [<ffffffff81011ce6>] ? int_ret_from_sys_call+0x7/0x1b
 [<ffffffff81012526>] ? retint_restore_args+0x5/0x6
 [<ffffffff81012ba0>] ? child_rip+0x0/0x20


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