cgroup: use restart_syscall() for retries after offline waits in cgroup_subtree_control_write()

After waiting for a child to finish offline,
cgroup_subtree_control_write() jumps up to retry from after the input
parsing and active protection breaking.  This retry makes the
scheduled locking update more difficult.  Let's simplify it by
returning with restart_syscall() for retries.

Signed-off-by: Tejun Heo <tj@kernel.org>
1 file changed