cgroup: support to set threaded mode in cgroup v2

Support to set threaded mode in cgroup v2. The premise of switching to threaded mode is that only the cgroup of cpuset, cpu and pids is supported.

Fixes: #90

Signed-off-by: yaoyinnan <yaoyinnan@foxmail.com>

tests/cgroup.rs

@@ -10,28 +10,25 @@ use cgroups_rs::Controller;
 use cgroups_rs::{Cgroup, CgroupPid, Subsystem};
 
 #[test]
-fn test_tasks_iterator() {
+fn test_procs_iterator_cgroup() {
     let h = cgroups_rs::hierarchies::auto();
     let pid = libc::pid_t::from(nix::unistd::getpid()) as u64;
-    let cg = Cgroup::new(h, String::from("test_tasks_iterator"));
+    let cg = Cgroup::new(h, String::from("test_procs_iterator_cgroup")).unwrap();
     {
         // Add a task to the control group.
-        cg.add_task(CgroupPid::from(pid)).unwrap();
+        cg.add_task_by_tgid(CgroupPid::from(pid)).unwrap();
 
-        use std::{thread, time};
-        thread::sleep(time::Duration::from_millis(100));
-
-        let mut tasks = cg.tasks().into_iter();
-        // Verify that the task is indeed in the control group
-        assert_eq!(tasks.next(), Some(CgroupPid::from(pid)));
-        assert_eq!(tasks.next(), None);
+        let mut procs = cg.procs().into_iter();
+        // Verify that the task is indeed in the xcontrol group
+        assert_eq!(procs.next(), Some(CgroupPid::from(pid)));
+        assert_eq!(procs.next(), None);
 
         // Now, try removing it.
-        cg.remove_task(CgroupPid::from(pid));
-        tasks = cg.tasks().into_iter();
+        cg.remove_task_by_tgid(CgroupPid::from(pid)).unwrap();
+        procs = cg.procs().into_iter();
 
         // Verify that it was indeed removed.
-        assert_eq!(tasks.next(), None);
+        assert_eq!(procs.next(), None);
     }
     cg.delete().unwrap();
 }
@@ -83,7 +80,7 @@ fn test_cgroup_v2() {
         return;
     }
     let h = cgroups_rs::hierarchies::auto();
-    let cg = Cgroup::new(h, String::from("test_v2"));
+    let cg = Cgroup::new(h, String::from("test_v2")).unwrap();
 
     let mem_controller: &MemController = cg.controller_of().unwrap();
     let (mem, swp, rev) = (4 * 1024 * 1000, 2 * 1024 * 1000, 1024 * 1000);
@@ -103,3 +100,57 @@ fn test_cgroup_v2() {
 
     cg.delete().unwrap();
 }
+
+#[test]
+fn test_tasks_iterator_cgroup_threaded_mode() {
+    if !cgroups_rs::hierarchies::is_cgroup2_unified_mode() {
+        return;
+    }
+    let h = cgroups_rs::hierarchies::auto();
+    let pid = libc::pid_t::from(nix::unistd::getpid()) as u64;
+    let cg = Cgroup::new(h, String::from("test_tasks_iterator_cgroup_threaded_mode")).unwrap();
+    let h = cgroups_rs::hierarchies::auto();
+    let specified_controllers = vec![String::from("cpuset"), String::from("cpu")];
+    let cg_threaded = Cgroup::new_with_specified_controllers(
+        h,
+        String::from("test_tasks_iterator_cgroup_threaded_mode/threaded"),
+        Some(specified_controllers),
+    )
+    .unwrap();
+    cg_threaded.set_cgroup_type("threaded").unwrap();
+    {
+        // Add a task to the control group.
+        cg.add_task_by_tgid(CgroupPid::from(pid)).unwrap();
+
+        let mut procs = cg.procs().into_iter();
+        // Verify that the task is indeed in the xcontrol group
+        assert_eq!(procs.next(), Some(CgroupPid::from(pid)));
+        assert_eq!(procs.next(), None);
+
+        // Add a task to the sub control group.
+        cg_threaded.add_task(CgroupPid::from(pid)).unwrap();
+
+        let mut tasks = cg_threaded.tasks().into_iter();
+        // Verify that the task is indeed in the xcontrol group
+        assert_eq!(tasks.next(), Some(CgroupPid::from(pid)));
+        assert_eq!(tasks.next(), None);
+
+        // Now, try move it to parent.
+        cg_threaded
+            .move_task_to_parent(CgroupPid::from(pid))
+            .unwrap();
+        tasks = cg_threaded.tasks().into_iter();
+
+        // Verify that it was indeed removed.
+        assert_eq!(tasks.next(), None);
+
+        // Now, try removing it.
+        cg.remove_task_by_tgid(CgroupPid::from(pid)).unwrap();
+        procs = cg.procs().into_iter();
+
+        // Verify that it was indeed removed.
+        assert_eq!(procs.next(), None);
+    }
+    cg_threaded.delete().unwrap();
+    cg.delete().unwrap();
+}