Add cgroup core selftests

This commit adds tests for some of the core functionalities
of cgroups v2.

The commit adds tests for some core principles of croup V2 API:

- test_cgcore_internal_process_constraint

  Tests internal process constraint.
  You can't add a pid to a domain parent if a controller is enabled.

- test_cgcore_top_down_constraint_enable

   Tests that you can't enable a controller on a child if it's not enabled
   on the parent.

- test_cgcore_top_down_constraint_disable

  Tests that you can't disable a controller on a parent if it's
  enabled in a child.

- test_cgcore_no_internal_process_constraint_on_threads

  Tests that there's no internal process constrain on threaded cgroups.
  You can add threads/processes on a parent with a controller enabled.

- test_cgcore_parent_becomes_threaded

  Tests that when a child becomes threaded the parent type becomes
  domain threaded.

- test_cgcore_invalid_domain

  In a situation like:

  A (domain threaded) - B (threaded) - C (domain)

  it tests that C can't be used until it is turned into a threaded cgroup.
  The "cgroup.type" file will report "domain (invalid)" in these cases.
  Operations which fail due to invalid topology use EOPNOTSUPP as the errno.

- test_cgcore_populated

  In a situation like:

  A(0) - B(0) - C(1)
         \ D(0)

  It tests that A, B and C's "populated" fields would be 1 while D's 0.
  It tests that after the one process in C is moved to root, A,B and C's
  "populated" fields would flip to "0" and file modified events will
  be generated on the "cgroup.events" files of both cgroups.

Signed-off-by: Claudio Zumbo <claudioz@fb.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: kernel-team@fb.com
Acked-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Roman Gushchin <guro@fb.com>
Signed-off-by: Shuah Khan (Samsung OSG) <shuah@kernel.org>

1 files changed, 8 insertions, 0 deletions

diff --git a/tools/testing/selftests/cgroup/cgroup_util.c b/tools/testing/selftests/cgroup/cgroup_util.c
index 1e9e3c470561..1c5d2b2a583b 100644
--- a/tools/testing/selftests/cgroup/cgroup_util.c
+++ b/tools/testing/selftests/cgroup/cgroup_util.c
@@ -229,6 +229,14 @@ retry:
 	return ret;
 }
 
+int cg_enter_current(const char *cgroup)
+{
+	char pidbuf[64];
+
+	snprintf(pidbuf, sizeof(pidbuf), "%d", getpid());
+	return cg_write(cgroup, "cgroup.procs", pidbuf);
+}
+
 int cg_run(const char *cgroup,
 	   int (*fn)(const char *cgroup, void *arg),
 	   void *arg)