Merge branch 'for-5.6-fixes' of git://git.kernel.org/pub/scm/linux/ke…

…rnel/git/tj/cgroup

Pull cgroup fix from Tejun Heo:
 "I made a mistake while removing cgroup task list lazy init
  optimization making the root cgroup.procs show entries for the
  init_tasks. The zero entries doesn't cause critical failures but does
  make systemd print out warning messages during boot.

  Fix it by omitting init_tasks as they should be"

* 'for-5.6-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: init_tasks shouldn't be linked to the root cgroup

kernel/cgroup/cgroup.c

@@ -5927,11 +5927,14 @@ void cgroup_post_fork(struct task_struct *child)
 
 	spin_lock_irq(&css_set_lock);
 
-	WARN_ON_ONCE(!list_empty(&child->cg_list));
-	cset = task_css_set(current); /* current is @child's parent */
-	get_css_set(cset);
-	cset->nr_tasks++;
-	css_set_move_task(child, NULL, cset, false);
+	/* init tasks are special, only link regular threads */
+	if (likely(child->pid)) {
+		WARN_ON_ONCE(!list_empty(&child->cg_list));
+		cset = task_css_set(current); /* current is @child's parent */
+		get_css_set(cset);
+		cset->nr_tasks++;
+		css_set_move_task(child, NULL, cset, false);
+	}
 
 	/*
 	 * If the cgroup has to be frozen, the new task has too.  Let's set