[LTP] cgroup_core02: modernize test using LTP cgroup API

[linuxtestproject.agent@gmail.com]

Hi Sushmitha,

On Thu, 1 Oct 2026 16:39:53 +0530, Sushmitha wrote:
> cgroup_core02: modernize test using LTP cgroup API

> diff --git a/cgroup_core02.c b/cgroup_core02.c
> new file mode 100644
> --- /dev/null
> +++ b/cgroup_core02.c

This adds an unbuilt root-level copy; normal builds and the existing
runtest entries still use the unchanged original test. Apply the changes
to testcases/kernel/controllers/cgroup/cgroup_core02.c instead and remove
the root-level copy.

> +		if (pid < 0)
> +			tst_brk(TBROK, "clone failed");

In a forked child, tst_brk(TBROK) kills the main test process with SIGKILL,
skipping cleanup(). If clone fails with EAGAIN, child_a and child_b remain,
and tst_cg_cleanup() cannot remove their parent because it does not remove
these descendants. Propagate the error to the main process and report
TBROK there so cleanup() runs.

> +			TST_EXP_FAIL(write(targ.fds[i], "0", 1), ENOENT,
> +				     "write to cgroup.procs from different namespace");

Use TST_EXP_FAIL2() here: write() returns a byte count on success, not zero.
TST_EXP_FAIL() diagnoses a successful one-byte write as "invalid retval 1"
instead of an unexpectedly successful migration.

Verdict - Needs revision

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