sched: fix the task_group hierarchy for UID grouping

UID grouping doesn't actually have a task_group representing the root of
the task_group tree. Add one.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/sched.h

@@ -2051,6 +2051,9 @@ extern void normalize_rt_tasks(void);
 #ifdef CONFIG_GROUP_SCHED
 
 extern struct task_group init_task_group;
+#ifdef CONFIG_USER_SCHED
+extern struct task_group root_task_group;
+#endif
 
 extern struct task_group *sched_create_group(struct task_group *parent);
 extern void sched_destroy_group(struct task_group *tg);

kernel/sched.c

@@ -274,6 +274,14 @@ struct task_group {
 };
 
 #ifdef CONFIG_USER_SCHED
+
+/*
+ * Root task group.
+ * 	Every UID task group (including init_task_group aka UID-0) will
+ * 	be a child to this group.
+ */
+struct task_group root_task_group;
+
 #ifdef CONFIG_FAIR_GROUP_SCHED
 /* Default task group's sched entity on each cpu */
 static DEFINE_PER_CPU(struct sched_entity, init_sched_entity);
@@ -285,6 +293,8 @@ static DEFINE_PER_CPU(struct cfs_rq, init_cfs_rq) ____cacheline_aligned_in_smp;
 static DEFINE_PER_CPU(struct sched_rt_entity, init_sched_rt_entity);
 static DEFINE_PER_CPU(struct rt_rq, init_rt_rq) ____cacheline_aligned_in_smp;
 #endif
+#else
+#define root_task_group init_task_group
 #endif
 
 /* task_group_lock serializes add/remove of task groups and also changes to
@@ -7507,6 +7517,9 @@ void __init sched_init(void)
 #endif
 #ifdef CONFIG_RT_GROUP_SCHED
 	alloc_size += 2 * nr_cpu_ids * sizeof(void **);
+#endif
+#ifdef CONFIG_USER_SCHED
+	alloc_size *= 2;
 #endif
 	/*
 	 * As sched_init() is called before page_alloc is setup,
@@ -7521,12 +7534,29 @@ void __init sched_init(void)
 
 		init_task_group.cfs_rq = (struct cfs_rq **)ptr;
 		ptr += nr_cpu_ids * sizeof(void **);
+
+#ifdef CONFIG_USER_SCHED
+		root_task_group.se = (struct sched_entity **)ptr;
+		ptr += nr_cpu_ids * sizeof(void **);
+
+		root_task_group.cfs_rq = (struct cfs_rq **)ptr;
+		ptr += nr_cpu_ids * sizeof(void **);
+#endif
 #endif
 #ifdef CONFIG_RT_GROUP_SCHED
 		init_task_group.rt_se = (struct sched_rt_entity **)ptr;
 		ptr += nr_cpu_ids * sizeof(void **);
 
 		init_task_group.rt_rq = (struct rt_rq **)ptr;
+		ptr += nr_cpu_ids * sizeof(void **);
+
+#ifdef CONFIG_USER_SCHED
+		root_task_group.rt_se = (struct sched_rt_entity **)ptr;
+		ptr += nr_cpu_ids * sizeof(void **);
+
+		root_task_group.rt_rq = (struct rt_rq **)ptr;
+		ptr += nr_cpu_ids * sizeof(void **);
+#endif
 #endif
 	}
 
@@ -7540,6 +7570,10 @@ void __init sched_init(void)
 #ifdef CONFIG_RT_GROUP_SCHED
 	init_rt_bandwidth(&init_task_group.rt_bandwidth,
 			global_rt_period(), global_rt_runtime());
+#ifdef CONFIG_USER_SCHED
+	init_rt_bandwidth(&root_task_group.rt_bandwidth,
+			global_rt_period(), RUNTIME_INF);
+#endif
 #endif
 
 #ifdef CONFIG_GROUP_SCHED
@@ -7582,6 +7616,8 @@ void __init sched_init(void)
 		 */
 		init_tg_cfs_entry(&init_task_group, &rq->cfs, NULL, i, 1, NULL);
 #elif defined CONFIG_USER_SCHED
+		root_task_group.shares = NICE_0_LOAD;
+		init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, 0, NULL);
 		/*
 		 * In case of task-groups formed thr' the user id of tasks,
 		 * init_task_group represents tasks belonging to root user.
@@ -7595,7 +7631,8 @@ void __init sched_init(void)
 		 */
 		init_tg_cfs_entry(&init_task_group,
 				&per_cpu(init_cfs_rq, i),
-				&per_cpu(init_sched_entity, i), i, 1, NULL);
+				&per_cpu(init_sched_entity, i), i, 1,
+				root_task_group.se[i]);
 
 #endif
 #endif /* CONFIG_FAIR_GROUP_SCHED */
@@ -7606,9 +7643,11 @@ void __init sched_init(void)
 #ifdef CONFIG_CGROUP_SCHED
 		init_tg_rt_entry(&init_task_group, &rq->rt, NULL, i, 1, NULL);
 #elif defined CONFIG_USER_SCHED
+		init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, 0, NULL);
 		init_tg_rt_entry(&init_task_group,
 				&per_cpu(init_rt_rq, i),
-				&per_cpu(init_sched_rt_entity, i), i, 1, NULL);
+				&per_cpu(init_sched_rt_entity, i), i, 1,
+				root_task_group.rt_se[i]);
 #endif
 #endif
 

kernel/user.c

@@ -101,7 +101,7 @@ static int sched_create_user(struct user_struct *up)
 {
 	int rc = 0;
 
-	up->tg = sched_create_group(NULL);
+	up->tg = sched_create_group(&root_task_group);
 	if (IS_ERR(up->tg))
 		rc = -ENOMEM;