Comment 36 for bug 1454892

This lts-trusty test kernel is not booting when installed on 12.04.5.

There are multiple events like this being recorded on the serial:
udevd[275]: timeout: killing '/sbin/modprobe -bv vmbus:394f16571591784eab55382f3bd5422d' [380]
udevd[246]: timeout: killing '/sbin/modprobe -bv vmbus:e7f4a0a9455a964db8278a841e8c03e6' [386]
udevd[249]: timeout: killing '/sbin/modprobe -bv vmbus:292efa3523ea364296ae3a6ebacba440' [394]

Removing the network card from the VM config, the system is booting normally.
Trying to boot the VM again with a NIC attached, the system is booting eventually, though we see the failed modprobe attempts.

There is also this call trace showing up that I was able to capture. Will check with the peers from our end if we can identify the missing patch or the one that's causing this.

[ 361.072113] INFO: task modprobe:740 blocked for more than 120 seconds.
[ 361.074061] Not tainted 3.13.0-78-generic #122
[ 361.075771] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 361.077886] modprobe D ffff88007ce33180 0 740 656 0x00000004
[ 361.077896] ffff880078193bc0 0000000000000086 ffff880036b26000 0000000000013180
[ 361.077901] ffff880078193fd8 0000000000013180 ffff880036b26000 ffff88007b60c240
[ 361.077905] ffff88007b60c244 ffff880036b26000 00000000ffffffff ffff88007b60c248
[ 361.077916] Call Trace:
[ 361.077924] [<ffffffff817294c9>] schedule_preempt_disabled+0x29/0x70
[ 361.077930] [<ffffffff8172b335>] __mutex_lock_slowpath+0x135/0x1b0
[ 361.077938] [<ffffffff81499e50>] ? __device_attach+0x40/0x40
[ 361.077943] [<ffffffff8172b3cf>] mutex_lock+0x1f/0x2f
[ 361.077953] [<ffffffff81499e99>] __driver_attach+0x49/0xa0
[ 361.077958] [<ffffffff81499e50>] ? __device_attach+0x40/0x40
[ 361.077963] [<ffffffff81497aa3>] bus_for_each_dev+0x63/0xa0
[ 361.077970] [<ffffffff8149950e>] driver_attach+0x1e/0x20
[ 361.077975] [<ffffffff814990f0>] bus_add_driver+0x180/0x250
[ 361.077986] [<ffffffff8149a564>] driver_register+0x64/0xf0
[ 361.077996] [<ffffffffa001bda7>] __vmbus_driver_register+0x57/0x60 [hv_vmbus]
[ 361.078001] [<ffffffffa0049000>] ? 0xffffffffa0048fff
[ 361.078009] [<ffffffffa004901e>] hv_kbd_init+0x1e/0x1000 [hyperv_keyboard]
[ 361.078019] [<ffffffff8100214a>] do_one_initcall+0xfa/0x1b0
[ 361.078026] [<ffffffff81059833>] ? set_memory_nx+0x43/0x50
[ 361.078032] [<ffffffff810e28fd>] load_module+0x12ed/0x1b50
[ 361.078038] [<ffffffff810de350>] ? store_uevent+0x40/0x40
[ 361.078049] [<ffffffff810e3202>] SyS_init_module+0xa2/0xf0
[ 361.078054] [<ffffffff817356dd>] system_call_fastpath+0x1a/0x1f