cgroups: document the effect of attaching PID 0 to a cgroup Document that a pid of zero(0) can be used to refer to the current task when attaching a task to a cgroup, as in the following usage: # echo 0 > /dev/cgroup/tasks This is consistent with existing cpuset behavior. Signed-off-by: Li Zefan <[email protected]> Acked-by: Paul Jackson <[email protected]> Acked-by: Dhaval Giani <[email protected]> Cc: Paul Menage <[email protected]> Cc: Balbir Singh <[email protected]> Cc: Andrea Righi <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>