Hi,

As reported by Kernel Test Robot [1], some pidfd tests fail.  This is
due to the use of vfork() which introduced some side effects.
Similarly, while making it more generic, a previous commit made some
Landlock file system tests flaky, and subject to the host's file system
mount configuration.

This series fixes all these side effects by replacing vfork() with
clone3() and CLONE_VFORK, which is cleaner (no arbitrary shared memory)
and makes the Kselftest framework more robust.

I tried different approaches and I found this one to be the cleaner and
less invasive for current test cases.

I successfully ran the following tests (using TEST_F and
fork/clone/clone3) with this series:
- landlock:fs_test
- landlock:net_test
- landlock:ptrace_test
- move_mount_set_group:move_mount_set_group_test
- net/af_unix:scm_pidfd
- perf_events:remove_on_exec
- pidfd:pidfd_getfd_test
- pidfd:pidfd_setns_test
- seccomp:seccomp_bpf
- user_events:abi_test

[1] https://lore.kernel.org/oe-lkp/202403291015.1fcfa957-oliver.sang@intel.com

Regards,

Mickaël Salaün (5):
  selftests/pidfd: Fix config for pidfd_setns_test
  selftests/landlock: Fix FS tests when run on a private mount point
  selftests/harness: Fix fixture teardown
  selftests/harness: Fix interleaved scheduling leading to race
    conditions
  selftests/harness: Fix vfork() side effects and uncaught errors

 tools/testing/selftests/kselftest_harness.h   | 113 +++++++++++++-----
 tools/testing/selftests/landlock/fs_test.c    |  83 ++++++++-----
 tools/testing/selftests/pidfd/config          |   2 +
 .../selftests/pidfd/pidfd_setns_test.c        |   2 +-
 4 files changed, 135 insertions(+), 65 deletions(-)


base-commit: c942a0cd3603e34dd2d7237e064d9318cb7f9654
-- 
2.44.0