Managing processes

Navigate the hierarchy

A name is a single folder name: an empty name, ., .. or a name containing / throws an ArgumentException, so a name cannot leave the parent control group.

Move processes into a control group

• AssociateProcess(process) and AssociateProcess(pid) move a process, with all its threads. The processes it starts afterward start in the same control group.
• AssociateThread(tid) moves a single thread, within the rules of the thread mode of the kernel (Linux 4.14 or later).
• GetProcesses() and GetThreads() list the process and thread identifiers of the control group.

A process belongs to exactly one control group: moving it removes it from the previous one.

Freeze and kill

var group = CGroup2.Root.CreateOrGetChild("myapp-freezer");
using var process = Process.Start("sleep", "60");
group.AssociateProcess(process);

// Freezing is asynchronous: IsFrozen returns true once every process of the cgroup is stopped
group.Freeze();
Assert.True(SpinWait.SpinUntil(group.IsFrozen, TimeSpan.FromSeconds(10)));

group.Unfreeze();
Assert.False(group.IsFrozen());

// Kill all the processes of the cgroup and of its descendants
group.Kill();
process.WaitForExit();
Assert.Empty(group.GetProcesses());
group.Delete();

• Freeze stops all the processes of the control group and of its descendants, until Unfreeze. The kernel freezes them asynchronously: IsFrozen returns true once it is done.
• IsFrozen returns false on a kernel without the freezer.
• Kill kills all the processes of the control group and of its descendants. It is the reliable way to stop a job, including the processes it started and those that left its process tree.

Delete a control group

Delete removes a control group that has no process and no child control group: it throws an IOException otherwise. Kill the processes and wait for them to exit, delete the children, then delete the group.

Enable controllers

A control group other than the root cannot enable controllers such as memory or io while it contains processes: move them to a child first.