ftests: add a test for cgroup v2 threaded support

Add a functional test to verify threaded cgroup support on a
cgroup v2 filesystem.

-----------------------------------------------------------------
Test Results:
        Run Date:                          Jan 25 10:41:34
        Passed:                                  1 test(s)
        Skipped:                                 0 test(s)
        Failed:                                  0 test(s)
-----------------------------------------------------------------
Timing Results:
        Test                          Time (sec)
        ----------------------------------------
        setup                               0.00
        036-cgset-multi_thread.py           0.10
        teardown                            0.00
        ----------------------------------------
        Total Run Time                      0.10

Suggested-by: Tom Hromatka <tom.hromatka@oracle.com>
Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tom Hromatka <tom.hromatka@oracle.com>
TJH: Minor cleanups to utilize the new set_and_validate() method

diff --git a/ftests/036-cgset-multi_thread.py b/ftests/036-cgset-multi_thread.py
new file mode 100755 (executable)
index 0000000..f12d565
--- /dev/null
+++ b/ftests/036-cgset-multi_thread.py
@@ -0,0 +1,104 @@
+#!/usr/bin/env python3
+#
+# Multithreaded cgroup v2 test
+#
+# Copyright (c) 2022 Oracle and/or its affiliates.
+# Author: Kamalesh Babulal <kamalesh.babulal@oracle.com>
+#
+
+#
+# This library is free software; you can redistribute it and/or modify it
+# under the terms of version 2.1 of the GNU Lesser General Public License as
+# published by the Free Software Foundation.
+#
+# This library is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License
+# for more details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with this library; if not, see <http://www.gnu.org/licenses>.
+#
+
+from cgroup import Cgroup, CgroupVersion
+from run import Run
+import consts
+import ftests
+import sys
+import os
+
+CONTROLLER = 'cpu'
+PARENT_CGNAME = '036threaded'
+CHILD_CGPATH = os.path.join(PARENT_CGNAME, 'childcg')
+
+SETTING = 'cgroup.type'
+AFTER = 'threaded'
+THREADS = 3
+
+def prereqs(config):
+    result = consts.TEST_PASSED
+    cause = None
+
+    if config.args.container:
+        result = consts.TEST_SKIPPED
+        cause = "This test cannot be run within a container"
+        return result, cause
+
+    if CgroupVersion.get_version(CONTROLLER) != CgroupVersion.CGROUP_V2:
+        result = consts.TEST_SKIPPED
+        cause = "This test requires the cgroup v2"
+        return result, cause
+
+    return result, cause
+
+def setup(config):
+    Cgroup.create(config, CONTROLLER, PARENT_CGNAME)
+    Cgroup.create(config, CONTROLLER, CHILD_CGPATH)
+
+    Cgroup.set_and_validate(config, CHILD_CGPATH, SETTING, AFTER)
+
+    return consts.TEST_PASSED, None
+
+def test(config):
+    config.process.create_threaded_process_in_cgroup(
+                                config, CONTROLLER, PARENT_CGNAME, THREADS)
+
+    threads = Cgroup.get(config, controller=None, cgname=PARENT_CGNAME,
+                         setting="cgroup.threads", print_headers=False,
+                         values_only=True)
+    threads = threads.replace('\n', '').split('\t')
+
+    #pick the first thread
+    thread_tid = threads[1]
+
+    Cgroup.set_and_validate(config, CHILD_CGPATH, "cgroup.threads", thread_tid)
+
+    return consts.TEST_PASSED, None
+
+def teardown(config):
+    # destroy the child processes
+    pids = Cgroup.get_pids_in_cgroup(config, PARENT_CGNAME, CONTROLLER)
+    if pids:
+        for p in pids.splitlines():
+            Run.run(['sudo', 'kill', '-9', p])
+
+    Cgroup.delete(config, CONTROLLER, PARENT_CGNAME, recursive=True)
+
+def main(config):
+    [result, cause] = prereqs(config)
+    if result != consts.TEST_PASSED:
+        return [result, cause]
+
+    try:
+        setup(config)
+        [result, cause] = test(config)
+    finally:
+        teardown(config)
+
+    return [result, cause]
+
+if __name__ == '__main__':
+    config = ftests.parse_args()
+    # this test was invoked directly.  run only it
+    config.args.num = int(os.path.basename(__file__).split('-')[0])
+    sys.exit(ftests.main(config))