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[Jürg Häfliger <1933969@xxxxxxxxxxxxxxxxxx>]

** Tags added: kernel-daily-bug

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https://bugs.launchpad.net/bugs/1933969

Title:
  test_pmtu_vti4_link_add_mtu() test from net/pmtu.sh in
  ubuntu_kernel_selftests cannot finish properly on 5.11 and 5.8

Status in ubuntu-kernel-tests:
  Fix Released
Status in linux package in Ubuntu:
  Invalid
Status in linux source package in Groovy:
  Fix Released
Status in linux source package in Hirsute:
  Fix Released

Bug description:
  Issue found with Groovy 5.8.0-60.67 on different amd64 / arm64 / s390x
  instances

  Test case:
  * tools/testing/selftests/net/pmtu.sh

  The pmtu.sh test will hang, and gets killed:
  # TEST: IPv6 over IPv6: PMTU exceptions - nexthop objects    [ OK ]
  # TEST: vti6: PMTU exceptions    [ OK ]
  Timer expired (1800 sec.), nuking pid 13090

  If you take a closer look on this node, you will see it's complaining about unregister_netdevice and modprobe command hung:
    unregister_netdevice: waiting for ip6_vti0 to become free. Usage count = 1
    unregister_netdevice: waiting for ip6_vti0 to become free. Usage count = 1
    INFO: task modprobe:40237 blocked for more than 122 seconds.
          Tainted: P           O      5.8.0-60-generic #67-Ubuntu
    "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
    modprobe        D    0 40237   1265 0x00000000
    Call Trace:
     [<0000000036dc7860>] __schedule+0x300/0x840
     [<0000000036dc7e02>] schedule+0x62/0x100
     [<00000000362c3bce>] rwsem_down_write_slowpath+0x23e/0x6c0
     [<0000000036b3716c>] register_pernet_device+0x2c/0xa0
     [<000003ff80a16034>] vti_init+0x34/0x1000 [ip_vti]
     [<00000000361a88b0>] do_one_initcall+0x40/0x200
     [<000000003632b34e>] do_init_module+0x6e/0x530
     [<000000003632e06a>] __do_sys_finit_module+0xaa/0xf0
     [<0000000036dcefbc>] system_call+0xe0/0x2b8
    unregister_netdevice: waiting for ip6_vti0 to become free. Usage count = 1

  Running process shows:
    root       40236  0.0  0.0   3748  1040 ?        D    10:39   0:00 ip link add vti4_a type vti local 192.168.1.1 remote 192.168.1.2 key 10
    root       40237  0.0  0.0   6092  1560 ?        D    10:39   0:00 /sbin/modprobe -q -- rtnl-link-vti

  This command "ip link add vti4_a type vti local" belongs to the
  test_pmtu_vti4_link_add_mtu() test in pmtu.sh

  This will prevent the whole ubuntu_kernel_selftests to finish

  On Jenkins, the test will hang and killed by the timeout:
  10:08:18 INFO | ========== Summary ===========
  10:08:18 INFO | No failed cases reported
  10:08:18 INFO | 		GOOD	ubuntu_kernel_selftests.ftrace	ubuntu_kernel_selftests.ftrace	timestamp=1624439298	localtime=Jun 23 10:08:18	completed successfully
  10:08:18 INFO | 	END GOOD	ubuntu_kernel_selftests.ftrace	ubuntu_kernel_selftests.ftrace	timestamp=1624439298	localtime=Jun 23 10:08:18
  10:08:18 DEBUG| Persistent state client._record_indent now set to 1
  10:08:18 DEBUG| Persistent state client.unexpected_reboot deleted
  10:08:18 INFO | END GOOD	----	----	timestamp=1624439298	localtime=Jun 23 10:08:18
  10:08:18 DEBUG| Persistent state client._record_indent now set to 0
  10:08:18 INFO | Report successfully generated at /home/ubuntu/autotest/client/results/default/job_report.html
  Build timed out (after 240 minutes). Marking the build as aborted.
  Build was aborted
  Recording test results
  ERROR: Step ‘Publish JUnit test result report’ failed: No test report files were found. Configuration error?

  Since we don't have any change to the pmtu.sh in this cycle. This
  looks like a potential regression to me.

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