selftests/cgroup: Fix minor defects in test_cpuset

With commit 98149f542530 ("selftests/cgroup: Add test for cpuset affinity
on controller disable"), sashiko [1] reported 3 different issues with
the new test_cpuset_affinity_on_controller_disable() test.

 1) `cpu_set_equal` iterates over mask bytes instead of bits, ignoring
    CPUs >= 8.
 2) Thread synchronization logic allows the main thread to read
    uninitialized stack memory, causing test flakiness.
 3) Test fails instead of skipping gracefully on uniprocessor systems
    or when CPU 1 is unavailable.

Fix the reported issues by:
 1) Iterates over the bit size of the mask.
 2) Test the new ready flag for each thread to end the wait
    on the conditional variable and eliminate the now unneeded
    AFFINITY_THREAD_A_READY and AFFINITY_THREADS_READY test phases.
 3) Return KSFT_SKIP on "cpuset.cpus" setting failure.

[1] https://sashiko.dev/#/patchset/20260712235510.373125-1-longman%40redhat.com

Fixes: 98149f542530 ("selftests/cgroup: Add test for cpuset affinity on controller disable")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

0 files changed, 0 insertions, 0 deletions