+static void __cgroup_kill(struct cgroup *cgrp)
+{
+ struct css_task_iter it;
+ struct task_struct *task;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ spin_lock_irq(&css_set_lock);
+ set_bit(CGRP_KILL, &cgrp->flags);
+ spin_unlock_irq(&css_set_lock);
+
+ css_task_iter_start(&cgrp->self, CSS_TASK_ITER_PROCS | CSS_TASK_ITER_THREADED, &it);
+ while ((task = css_task_iter_next(&it))) {
+ /* Ignore kernel threads here. */
+ if (task->flags & PF_KTHREAD)
+ continue;
+
+ /* Skip tasks that are already dying. */
+ if (__fatal_signal_pending(task))
+ continue;
+
+ send_sig(SIGKILL, task, 0);
+ }
+ css_task_iter_end(&it);
+
+ spin_lock_irq(&css_set_lock);
+ clear_bit(CGRP_KILL, &cgrp->flags);
+ spin_unlock_irq(&css_set_lock);
+}
+
+static void cgroup_kill(struct cgroup *cgrp)
+{
+ struct cgroup_subsys_state *css;
+ struct cgroup *dsct;
+
+ lockdep_assert_held(&cgroup_mutex);
+
+ cgroup_for_each_live_descendant_pre(dsct, css, cgrp)
+ __cgroup_kill(dsct);
+}
+
+static ssize_t cgroup_kill_write(struct kernfs_open_file *of, char *buf,
+ size_t nbytes, loff_t off)
+{
+ ssize_t ret = 0;
+ int kill;
+ struct cgroup *cgrp;
+
+ ret = kstrtoint(strstrip(buf), 0, &kill);
+ if (ret)
+ return ret;
+
+ if (kill != 1)
+ return -ERANGE;
+
+ cgrp = cgroup_kn_lock_live(of->kn, false);
+ if (!cgrp)
+ return -ENOENT;
+
+ /*
+ * Killing is a process directed operation, i.e. the whole thread-group
+ * is taken down so act like we do for cgroup.procs and only make this
+ * writable in non-threaded cgroups.
+ */
+ if (cgroup_is_threaded(cgrp))
+ ret = -EOPNOTSUPP;
+ else
+ cgroup_kill(cgrp);
+
+ cgroup_kn_unlock(of->kn);
+
+ return ret ?: nbytes;
+}
+