1#ifdef CONFIG_SCHED_AUTOGROUP
2
3#include "sched.h"
4
5#include <linux/proc_fs.h>
6#include <linux/seq_file.h>
7#include <linux/kallsyms.h>
8#include <linux/utsname.h>
9#include <linux/security.h>
10#include <linux/export.h>
11
12unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
13static struct autogroup autogroup_default;
14static atomic_t autogroup_seq_nr;
15
16void __init autogroup_init(struct task_struct *init_task)
17{
18	autogroup_default.tg = &root_task_group;
19	kref_init(&autogroup_default.kref);
20	init_rwsem(&autogroup_default.lock);
21	init_task->signal->autogroup = &autogroup_default;
22}
23
24void autogroup_free(struct task_group *tg)
25{
26	kfree(tg->autogroup);
27}
28
29static inline void autogroup_destroy(struct kref *kref)
30{
31	struct autogroup *ag = container_of(kref, struct autogroup, kref);
32
33#ifdef CONFIG_RT_GROUP_SCHED
34	/* We've redirected RT tasks to the root task group... */
35	ag->tg->rt_se = NULL;
36	ag->tg->rt_rq = NULL;
37#endif
38	sched_offline_group(ag->tg);
39	sched_destroy_group(ag->tg);
40}
41
42static inline void autogroup_kref_put(struct autogroup *ag)
43{
44	kref_put(&ag->kref, autogroup_destroy);
45}
46
47static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
48{
49	kref_get(&ag->kref);
50	return ag;
51}
52
53static inline struct autogroup *autogroup_task_get(struct task_struct *p)
54{
55	struct autogroup *ag;
56	unsigned long flags;
57
58	if (!lock_task_sighand(p, &flags))
59		return autogroup_kref_get(&autogroup_default);
60
61	ag = autogroup_kref_get(p->signal->autogroup);
62	unlock_task_sighand(p, &flags);
63
64	return ag;
65}
66
67static inline struct autogroup *autogroup_create(void)
68{
69	struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL);
70	struct task_group *tg;
71
72	if (!ag)
73		goto out_fail;
74
75	tg = sched_create_group(&root_task_group);
76
77	if (IS_ERR(tg))
78		goto out_free;
79
80	kref_init(&ag->kref);
81	init_rwsem(&ag->lock);
82	ag->id = atomic_inc_return(&autogroup_seq_nr);
83	ag->tg = tg;
84#ifdef CONFIG_RT_GROUP_SCHED
85	/*
86	 * Autogroup RT tasks are redirected to the root task group
87	 * so we don't have to move tasks around upon policy change,
88	 * or flail around trying to allocate bandwidth on the fly.
89	 * A bandwidth exception in __sched_setscheduler() allows
90	 * the policy change to proceed.
91	 */
92	free_rt_sched_group(tg);
93	tg->rt_se = root_task_group.rt_se;
94	tg->rt_rq = root_task_group.rt_rq;
95#endif
96	tg->autogroup = ag;
97
98	sched_online_group(tg, &root_task_group);
99	return ag;
100
101out_free:
102	kfree(ag);
103out_fail:
104	if (printk_ratelimit()) {
105		printk(KERN_WARNING "autogroup_create: %s failure.\n",
106			ag ? "sched_create_group()" : "kmalloc()");
107	}
108
109	return autogroup_kref_get(&autogroup_default);
110}
111
112bool task_wants_autogroup(struct task_struct *p, struct task_group *tg)
113{
114	if (tg != &root_task_group)
115		return false;
116
117	/*
118	 * We can only assume the task group can't go away on us if
119	 * autogroup_move_group() can see us on ->thread_group list.
120	 */
121	if (p->flags & PF_EXITING)
122		return false;
123
124	return true;
125}
126
127static void
128autogroup_move_group(struct task_struct *p, struct autogroup *ag)
129{
130	struct autogroup *prev;
131	struct task_struct *t;
132	unsigned long flags;
133
134	BUG_ON(!lock_task_sighand(p, &flags));
135
136	prev = p->signal->autogroup;
137	if (prev == ag) {
138		unlock_task_sighand(p, &flags);
139		return;
140	}
141
142	p->signal->autogroup = autogroup_kref_get(ag);
143
144	if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
145		goto out;
146
147	for_each_thread(p, t)
148		sched_move_task(t);
149out:
150	unlock_task_sighand(p, &flags);
151	autogroup_kref_put(prev);
152}
153
154/* Allocates GFP_KERNEL, cannot be called under any spinlock */
155void sched_autogroup_create_attach(struct task_struct *p)
156{
157	struct autogroup *ag = autogroup_create();
158
159	autogroup_move_group(p, ag);
160	/* drop extra reference added by autogroup_create() */
161	autogroup_kref_put(ag);
162}
163EXPORT_SYMBOL(sched_autogroup_create_attach);
164
165/* Cannot be called under siglock.  Currently has no users */
166void sched_autogroup_detach(struct task_struct *p)
167{
168	autogroup_move_group(p, &autogroup_default);
169}
170EXPORT_SYMBOL(sched_autogroup_detach);
171
172void sched_autogroup_fork(struct signal_struct *sig)
173{
174	sig->autogroup = autogroup_task_get(current);
175}
176
177void sched_autogroup_exit(struct signal_struct *sig)
178{
179	autogroup_kref_put(sig->autogroup);
180}
181
182static int __init setup_autogroup(char *str)
183{
184	sysctl_sched_autogroup_enabled = 0;
185
186	return 1;
187}
188
189__setup("noautogroup", setup_autogroup);
190
191#ifdef CONFIG_PROC_FS
192
193int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
194{
195	static unsigned long next = INITIAL_JIFFIES;
196	struct autogroup *ag;
197	int err;
198
199	if (nice < MIN_NICE || nice > MAX_NICE)
200		return -EINVAL;
201
202	err = security_task_setnice(current, nice);
203	if (err)
204		return err;
205
206	if (nice < 0 && !can_nice(current, nice))
207		return -EPERM;
208
209	/* this is a heavy operation taking global locks.. */
210	if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
211		return -EAGAIN;
212
213	next = HZ / 10 + jiffies;
214	ag = autogroup_task_get(p);
215
216	down_write(&ag->lock);
217	err = sched_group_set_shares(ag->tg, prio_to_weight[nice + 20]);
218	if (!err)
219		ag->nice = nice;
220	up_write(&ag->lock);
221
222	autogroup_kref_put(ag);
223
224	return err;
225}
226
227void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
228{
229	struct autogroup *ag = autogroup_task_get(p);
230
231	if (!task_group_is_autogroup(ag->tg))
232		goto out;
233
234	down_read(&ag->lock);
235	seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
236	up_read(&ag->lock);
237
238out:
239	autogroup_kref_put(ag);
240}
241#endif /* CONFIG_PROC_FS */
242
243#ifdef CONFIG_SCHED_DEBUG
244int autogroup_path(struct task_group *tg, char *buf, int buflen)
245{
246	if (!task_group_is_autogroup(tg))
247		return 0;
248
249	return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
250}
251#endif /* CONFIG_SCHED_DEBUG */
252
253#endif /* CONFIG_SCHED_AUTOGROUP */
254