1#ifdef CONFIG_SCHED_AUTOGROUP
  2
  3#include <linux/proc_fs.h>
  4#include <linux/seq_file.h>
  5#include <linux/kallsyms.h>
  6#include <linux/utsname.h>
  7
  8unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
  9static struct autogroup autogroup_default;
 10static atomic_t autogroup_seq_nr;
 11
 12static void __init autogroup_init(struct task_struct *init_task)
 13{
 14	autogroup_default.tg = &root_task_group;
 15	kref_init(&autogroup_default.kref);
 16	init_rwsem(&autogroup_default.lock);
 17	init_task->signal->autogroup = &autogroup_default;
 18}
 19
 20static inline void autogroup_free(struct task_group *tg)
 21{
 22	kfree(tg->autogroup);
 23}
 24
 25static inline void autogroup_destroy(struct kref *kref)
 26{
 27	struct autogroup *ag = container_of(kref, struct autogroup, kref);
 28
 29#ifdef CONFIG_RT_GROUP_SCHED
 30	/* We've redirected RT tasks to the root task group... */
 31	ag->tg->rt_se = NULL;
 32	ag->tg->rt_rq = NULL;
 33#endif
 34	sched_destroy_group(ag->tg);
 35}
 36
 37static inline void autogroup_kref_put(struct autogroup *ag)
 38{
 39	kref_put(&ag->kref, autogroup_destroy);
 40}
 41
 42static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
 43{
 44	kref_get(&ag->kref);
 45	return ag;
 46}
 47
 48static inline struct autogroup *autogroup_task_get(struct task_struct *p)
 49{
 50	struct autogroup *ag;
 51	unsigned long flags;
 52
 53	if (!lock_task_sighand(p, &flags))
 54		return autogroup_kref_get(&autogroup_default);
 55
 56	ag = autogroup_kref_get(p->signal->autogroup);
 57	unlock_task_sighand(p, &flags);
 58
 59	return ag;
 60}
 61
 62#ifdef CONFIG_RT_GROUP_SCHED
 63static void free_rt_sched_group(struct task_group *tg);
 64#endif
 65
 66static inline struct autogroup *autogroup_create(void)
 67{
 68	struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL);
 69	struct task_group *tg;
 70
 71	if (!ag)
 72		goto out_fail;
 73
 74	tg = sched_create_group(&root_task_group);
 75
 76	if (IS_ERR(tg))
 77		goto out_free;
 78
 79	kref_init(&ag->kref);
 80	init_rwsem(&ag->lock);
 81	ag->id = atomic_inc_return(&autogroup_seq_nr);
 82	ag->tg = tg;
 83#ifdef CONFIG_RT_GROUP_SCHED
 84	/*
 85	 * Autogroup RT tasks are redirected to the root task group
 86	 * so we don't have to move tasks around upon policy change,
 87	 * or flail around trying to allocate bandwidth on the fly.
 88	 * A bandwidth exception in __sched_setscheduler() allows
 89	 * the policy change to proceed.  Thereafter, task_group()
 90	 * returns &root_task_group, so zero bandwidth is required.
 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	return ag;
 99
100out_free:
101	kfree(ag);
102out_fail:
103	if (printk_ratelimit()) {
104		printk(KERN_WARNING "autogroup_create: %s failure.\n",
105			ag ? "sched_create_group()" : "kmalloc()");
106	}
107
108	return autogroup_kref_get(&autogroup_default);
109}
110
111static inline bool
112task_wants_autogroup(struct task_struct *p, struct task_group *tg)
113{
114	if (tg != &root_task_group)
115		return false;
116
117	if (p->sched_class != &fair_sched_class)
118		return false;
119
120	/*
121	 * We can only assume the task group can't go away on us if
122	 * autogroup_move_group() can see us on ->thread_group list.
123	 */
124	if (p->flags & PF_EXITING)
125		return false;
126
127	return true;
128}
129
130static inline bool task_group_is_autogroup(struct task_group *tg)
131{
132	return !!tg->autogroup;
133}
134
135static inline struct task_group *
136autogroup_task_group(struct task_struct *p, struct task_group *tg)
137{
138	int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
139
140	if (enabled && task_wants_autogroup(p, tg))
141		return p->signal->autogroup->tg;
142
143	return tg;
144}
145
146static void
147autogroup_move_group(struct task_struct *p, struct autogroup *ag)
148{
149	struct autogroup *prev;
150	struct task_struct *t;
151	unsigned long flags;
152
153	BUG_ON(!lock_task_sighand(p, &flags));
154
155	prev = p->signal->autogroup;
156	if (prev == ag) {
157		unlock_task_sighand(p, &flags);
158		return;
159	}
160
161	p->signal->autogroup = autogroup_kref_get(ag);
162
163	if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
164		goto out;
165
166	t = p;
167	do {
168		sched_move_task(t);
169	} while_each_thread(p, t);
170
171out:
172	unlock_task_sighand(p, &flags);
173	autogroup_kref_put(prev);
174}
175
176/* Allocates GFP_KERNEL, cannot be called under any spinlock */
177void sched_autogroup_create_attach(struct task_struct *p)
178{
179	struct autogroup *ag = autogroup_create();
180
181	autogroup_move_group(p, ag);
182	/* drop extra reference added by autogroup_create() */
183	autogroup_kref_put(ag);
184}
185EXPORT_SYMBOL(sched_autogroup_create_attach);
186
187/* Cannot be called under siglock.  Currently has no users */
188void sched_autogroup_detach(struct task_struct *p)
189{
190	autogroup_move_group(p, &autogroup_default);
191}
192EXPORT_SYMBOL(sched_autogroup_detach);
193
194void sched_autogroup_fork(struct signal_struct *sig)
195{
196	sig->autogroup = autogroup_task_get(current);
197}
198
199void sched_autogroup_exit(struct signal_struct *sig)
200{
201	autogroup_kref_put(sig->autogroup);
202}
203
204static int __init setup_autogroup(char *str)
205{
206	sysctl_sched_autogroup_enabled = 0;
207
208	return 1;
209}
210
211__setup("noautogroup", setup_autogroup);
212
213#ifdef CONFIG_PROC_FS
214
215int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice)
216{
217	static unsigned long next = INITIAL_JIFFIES;
218	struct autogroup *ag;
219	int err;
220
221	if (*nice < -20 || *nice > 19)
222		return -EINVAL;
223
224	err = security_task_setnice(current, *nice);
225	if (err)
226		return err;
227
228	if (*nice < 0 && !can_nice(current, *nice))
229		return -EPERM;
230
231	/* this is a heavy operation taking global locks.. */
232	if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
233		return -EAGAIN;
234
235	next = HZ / 10 + jiffies;
236	ag = autogroup_task_get(p);
237
238	down_write(&ag->lock);
239	err = sched_group_set_shares(ag->tg, prio_to_weight[*nice + 20]);
240	if (!err)
241		ag->nice = *nice;
242	up_write(&ag->lock);
243
244	autogroup_kref_put(ag);
245
246	return err;
247}
248
249void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
250{
251	struct autogroup *ag = autogroup_task_get(p);
252
253	if (!task_group_is_autogroup(ag->tg))
254		goto out;
255
256	down_read(&ag->lock);
257	seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
258	up_read(&ag->lock);
259
260out:
261	autogroup_kref_put(ag);
262}
263#endif /* CONFIG_PROC_FS */
264
265#ifdef CONFIG_SCHED_DEBUG
266static inline int autogroup_path(struct task_group *tg, char *buf, int buflen)
267{
268	if (!task_group_is_autogroup(tg))
269		return 0;
270
271	return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
272}
273#endif /* CONFIG_SCHED_DEBUG */
274
275#endif /* CONFIG_SCHED_AUTOGROUP */