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[Vinicius Peixoto <2073526@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

The timers:posix_timers selftests are failing consistently in multiple
cloud kernels (including noble:linux-azure and jammy:linux-azure-6.8,
jammy:linux-aws-6.8):

DEBUG| Running 'make run_tests -C timers TEST_PROGS=posix_timers TEST_GEN_PROGS='' TEST_CUSTOM_PROGS='''
DEBUG| [stdout] make: Entering directory '/home/azure/autotest/client/tmp/ubuntu_kernel_selftests/src/linux/tools/testing/selftests/timers'
DEBUG| [stdout] TAP version 13
DEBUG| [stdout] 1..1
DEBUG| [stdout] # timeout set to 0
DEBUG| [stdout] # selftests: timers: posix_timers
DEBUG| [stdout] # TAP version 13
DEBUG| [stdout] # 1..6
DEBUG| [stdout] # # Testing posix timers. False negative may happen on CPU execution 
DEBUG| [stdout] # # based timers if other threads run on the CPU...
DEBUG| [stdout] # Diff too high: 3904813..not ok 1 ITIMER_VIRTUAL
DEBUG| [stdout] # Diff too high: 4025856..not ok 2 ITIMER_PROF
DEBUG| [stdout] # ok 3 ITIMER_REAL
DEBUG| [stdout] # ok 4 timer_create() per thread
DEBUG| [stdout] # ok 5 timer_create() per process
DEBUG| [stdout] # ok 6 check signal distribution
DEBUG| [stdout] # # Totals: pass:4 fail:2 xfail:0 xpass:0 skip:0 error:0

This has been spotted before (LP: #1851805, LP: #1849095), but I believe
the tests were flaky due to jitter (they fail if the diff value >
2500000us); this time the tests seem to fail consistently on 6.8 kernels
with the diff value being always close to 4000000us (seems too high to
be due to jitter). I verified they fail consistently (after several
runs) on noble:linux-azure running on a Standard_A2_v2 Azure instance,
while passing consistently on jammy:linux-azure on the same instance
flavor.

** Affects: ubuntu-kernel-tests
     Importance: Undecided
         Status: New


** Tags: amd64 azure noble ubuntu-kernel-selftests

** Tags added: amd64

** Tags added: azure noble

** Tags added: ubuntu-kernel-selftests

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https://bugs.launchpad.net/bugs/2073526

Title:
  timers:posix_timers in ubuntu_kernel_selftests fails on Noble

Status in ubuntu-kernel-tests:
  New

Bug description:
  The timers:posix_timers selftests are failing consistently in multiple
  cloud kernels (including noble:linux-azure and jammy:linux-azure-6.8,
  jammy:linux-aws-6.8):

  DEBUG| Running 'make run_tests -C timers TEST_PROGS=posix_timers TEST_GEN_PROGS='' TEST_CUSTOM_PROGS='''
  DEBUG| [stdout] make: Entering directory '/home/azure/autotest/client/tmp/ubuntu_kernel_selftests/src/linux/tools/testing/selftests/timers'
  DEBUG| [stdout] TAP version 13
  DEBUG| [stdout] 1..1
  DEBUG| [stdout] # timeout set to 0
  DEBUG| [stdout] # selftests: timers: posix_timers
  DEBUG| [stdout] # TAP version 13
  DEBUG| [stdout] # 1..6
  DEBUG| [stdout] # # Testing posix timers. False negative may happen on CPU execution 
  DEBUG| [stdout] # # based timers if other threads run on the CPU...
  DEBUG| [stdout] # Diff too high: 3904813..not ok 1 ITIMER_VIRTUAL
  DEBUG| [stdout] # Diff too high: 4025856..not ok 2 ITIMER_PROF
  DEBUG| [stdout] # ok 3 ITIMER_REAL
  DEBUG| [stdout] # ok 4 timer_create() per thread
  DEBUG| [stdout] # ok 5 timer_create() per process
  DEBUG| [stdout] # ok 6 check signal distribution
  DEBUG| [stdout] # # Totals: pass:4 fail:2 xfail:0 xpass:0 skip:0 error:0

  This has been spotted before (LP: #1851805, LP: #1849095), but I
  believe the tests were flaky due to jitter (they fail if the diff
  value > 2500000us); this time the tests seem to fail consistently on
  6.8 kernels with the diff value being always close to 4000000us (seems
  too high to be due to jitter). I verified they fail consistently
  (after several runs) on noble:linux-azure running on a Standard_A2_v2
  Azure instance, while passing consistently on jammy:linux-azure on the
  same instance flavor.

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