[PATCH v2] selftests/cgroup: add user_usec sanity check in test_cpucg_nice

[Shaojie Sun]

In test_cpucg_nice, after the child process exits, user_usec is
read from cpu.stat but the value is not checked. Add a sanity check
to ensure user_usec > 0, analogous to test_cpucg_stats(), so that
the test fails early if CPU usage wasn't properly accounted.

Signed-off-by: Shaojie Sun <sunshaojie@xxxxxxxxxx>
---
v2: Instead of simply removing the unused user_usec read, add a sanity
    check (if user_usec <= 0, goto cleanup) analogous to test_cpucg_stats(),
    as suggested by Michal.

 tools/testing/selftests/cgroup/test_cpu.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/testing/selftests/cgroup/test_cpu.c b/tools/testing/selftests/cgroup/test_cpu.c
index 7a40d76b9548..5a44705ed3fd 100644
--- a/tools/testing/selftests/cgroup/test_cpu.c
+++ b/tools/testing/selftests/cgroup/test_cpu.c
@@ -291,6 +291,8 @@ static int test_cpucg_nice(const char *root)
 
 		user_usec = cg_read_key_long(cpucg, "cpu.stat", "user_usec");
 		nice_usec = cg_read_key_long(cpucg, "cpu.stat", "nice_usec");
+		if (user_usec <= 0)
+			goto cleanup;
 		if (!values_close_report(nice_usec, expected_nice_usec, 1))
 			goto cleanup;
 
-- 
2.25.1