We've observed issues on two codfw cache hosts (cp2006 and cp2015) while bringing up the network interface at startup. Starting networking.service takes a little more than 3 minutes, but eventually succeeds. The unit can be seen on top of systemd-analyze blame:
3min 1.271s networking.service
The problem might be related to the intel_uncore kernel module, in both cases the following output could be found in dmesg:
[Mon Apr 10 15:14:17 2017] INFO: task systemd-udevd:677 blocked for more than 120 seconds. [Mon Apr 10 15:14:17 2017] Tainted: G E 4.9.0-0.bpo.2-amd64 #1 [Mon Apr 10 15:14:17 2017] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [Mon Apr 10 15:14:17 2017] systemd-udevd D 0 677 665 0x00000004 [Mon Apr 10 15:14:17 2017] ffff9d19b153fc00 0000000000000000 ffff9d39b2a94000 ffff9d19ae362080 [Mon Apr 10 15:14:17 2017] ffff9d39bf158700 ffffb9179a677b50 ffffffffbc7f668d 0000000000000001 [Mon Apr 10 15:14:17 2017] 0000000000000001 00000000024080c0 00000000024080c0 ffff9d19ae362080 [Mon Apr 10 15:14:17 2017] Call Trace: [Mon Apr 10 15:14:17 2017] [<ffffffffbc7f668d>] ? __schedule+0x23d/0x6d0 [Mon Apr 10 15:14:17 2017] [<ffffffffc08bee30>] ? uncore_pci_remove+0x160/0x160 [intel_uncore] [Mon Apr 10 15:14:17 2017] [<ffffffffbc7f6b52>] ? schedule+0x32/0x80 [Mon Apr 10 15:14:17 2017] [<ffffffffbc7fa089>] ? schedule_timeout+0x249/0x300 [Mon Apr 10 15:14:17 2017] [<ffffffffc08be554>] ? uncore_alloc_box+0x74/0xd0 [intel_uncore] [Mon Apr 10 15:14:17 2017] [<ffffffffc08be64f>] ? uncore_cpu_prepare+0x9f/0x100 [intel_uncore] [Mon Apr 10 15:14:17 2017] [<ffffffffc08bee30>] ? uncore_pci_remove+0x160/0x160 [intel_uncore] [Mon Apr 10 15:14:17 2017] [<ffffffffbc7f756a>] ? wait_for_completion+0xfa/0x130 [Mon Apr 10 15:14:17 2017] [<ffffffffbc2a2b30>] ? wake_up_q+0x60/0x60 [Mon Apr 10 15:14:17 2017] [<ffffffffbc2791d6>] ? cpuhp_issue_call+0x96/0xc0 [Mon Apr 10 15:14:17 2017] [<ffffffffbc27948a>] ? __cpuhp_setup_state+0xca/0x200 [Mon Apr 10 15:14:17 2017] [<ffffffffc08dd317>] ? intel_uncore_init+0x1c1/0xeaa [intel_uncore] [Mon Apr 10 15:14:17 2017] [<ffffffffc08dd156>] ? uncore_type_init+0x156/0x156 [intel_uncore] [Mon Apr 10 15:14:17 2017] [<ffffffffbc20218c>] ? do_one_initcall+0x4c/0x180 [Mon Apr 10 15:14:17 2017] [<ffffffffbc37c3af>] ? do_init_module+0x5a/0x1f1 [Mon Apr 10 15:14:17 2017] [<ffffffffbc301de9>] ? load_module+0x23c9/0x28f0 [Mon Apr 10 15:14:17 2017] [<ffffffffbc2fe650>] ? __symbol_put+0x60/0x60 [Mon Apr 10 15:14:17 2017] [<ffffffffbc4033a4>] ? vfs_read+0x114/0x130 [Mon Apr 10 15:14:17 2017] [<ffffffffbc4a3e01>] ? security_capable+0x41/0x60 [Mon Apr 10 15:14:17 2017] [<ffffffffbc3024fe>] ? SYSC_finit_module+0x8e/0xe0 [Mon Apr 10 15:14:17 2017] [<ffffffffbc7fb3fb>] ? system_call_fast_compare_end+0xc/0x9b