add add_task_by_tgid

Add task by writing thread group id to cgroup.procs.

Signed-off-by: Yang, Wei <wei.yang1@linux.alibaba.com>
Signed-off-by: Tim Zhang <tim@hyper.sh>

src/cgroup.rs

@@ -233,6 +233,13 @@ impl<'b> Cgroup<'b> {
         }
     }
 
+    /// Attach a task to the control group by thread group id.
+    pub fn add_task_by_tgid(&self, pid: CgroupPid) -> Result<()> {
+        self.subsystems()
+            .iter()
+            .try_for_each(|sub| sub.to_controller().add_task_by_tgid(&pid))
+    }
+
     /// Returns an Iterator that can be used to iterate over the tasks that are currently in the
     /// control group.
     pub fn tasks(&self) -> Vec<CgroupPid> {

src/lib.rs

@@ -219,6 +219,9 @@ pub trait Controller {
     /// Attach a task to this controller.
     fn add_task(&self, pid: &CgroupPid) -> Result<()>;
 
+    /// Attach a task to this controller.
+    fn add_task_by_tgid(&self, pid: &CgroupPid) -> Result<()>;
+
     /// Get the list of tasks that this controller has.
     fn tasks(&self) -> Vec<CgroupPid>;
 
@@ -278,6 +281,14 @@ where
         })
     }
 
+    /// Attach a task to this controller by thread group id.
+    fn add_task_by_tgid(&self, pid: &CgroupPid) -> Result<()> {
+        self.open_path("cgroup.procs", true).and_then(|mut file| {
+            file.write_all(pid.pid.to_string().as_ref())
+                .map_err(|e| Error::with_cause(ErrorKind::WriteFailed, e))
+        })
+    }
+
     /// Get the list of tasks that this controller has.
     fn tasks(&self) -> Vec<CgroupPid> {
         let mut file = "tasks";