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.  Thereafter, task_group()
 91	 * returns &root_task_group, so zero bandwidth is required.
 92	 */
 93	free_rt_sched_group(tg);
 94	tg->rt_se = root_task_group.rt_se;
 95	tg->rt_rq = root_task_group.rt_rq;
 96#endif
 97	tg->autogroup = ag;
 98
 99	sched_online_group(tg, &root_task_group);
100	return ag;
101
102out_free:
103	kfree(ag);
104out_fail:
105	if (printk_ratelimit()) {
106		printk(KERN_WARNING "autogroup_create: %s failure.\n",
107			ag ? "sched_create_group()" : "kmalloc()");
108	}
109
110	return autogroup_kref_get(&autogroup_default);
111}
112
113bool task_wants_autogroup(struct task_struct *p, struct task_group *tg)
114{
115	if (tg != &root_task_group)
116		return false;
117
118	if (p->sched_class != &fair_sched_class)
119		return false;
120
121	/*
122	 * We can only assume the task group can't go away on us if
123	 * autogroup_move_group() can see us on ->thread_group list.
124	 */
125	if (p->flags & PF_EXITING)
126		return false;
127
128	return true;
129}
130
131static void
132autogroup_move_group(struct task_struct *p, struct autogroup *ag)
133{
134	struct autogroup *prev;
135	struct task_struct *t;
136	unsigned long flags;
137
138	BUG_ON(!lock_task_sighand(p, &flags));
139
140	prev = p->signal->autogroup;
141	if (prev == ag) {
142		unlock_task_sighand(p, &flags);
143		return;
144	}
145
146	p->signal->autogroup = autogroup_kref_get(ag);
147
148	if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
149		goto out;
150
151	t = p;
152	do {
153		sched_move_task(t);
154	} while_each_thread(p, t);
155
156out:
157	unlock_task_sighand(p, &flags);
158	autogroup_kref_put(prev);
159}
160
161/* Allocates GFP_KERNEL, cannot be called under any spinlock */
162void sched_autogroup_create_attach(struct task_struct *p)
163{
164	struct autogroup *ag = autogroup_create();
165
166	autogroup_move_group(p, ag);
167	/* drop extra reference added by autogroup_create() */
168	autogroup_kref_put(ag);
169}
170EXPORT_SYMBOL(sched_autogroup_create_attach);
171
172/* Cannot be called under siglock.  Currently has no users */
173void sched_autogroup_detach(struct task_struct *p)
174{
175	autogroup_move_group(p, &autogroup_default);
176}
177EXPORT_SYMBOL(sched_autogroup_detach);
178
179void sched_autogroup_fork(struct signal_struct *sig)
180{
181	sig->autogroup = autogroup_task_get(current);
182}
183
184void sched_autogroup_exit(struct signal_struct *sig)
185{
186	autogroup_kref_put(sig->autogroup);
187}
188
189static int __init setup_autogroup(char *str)
190{
191	sysctl_sched_autogroup_enabled = 0;
192
193	return 1;
194}
195
196__setup("noautogroup", setup_autogroup);
197
198#ifdef CONFIG_PROC_FS
199
200int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
201{
202	static unsigned long next = INITIAL_JIFFIES;
203	struct autogroup *ag;
204	int err;
205
206	if (nice < MIN_NICE || nice > MAX_NICE)
207		return -EINVAL;
208
209	err = security_task_setnice(current, nice);
210	if (err)
211		return err;
212
213	if (nice < 0 && !can_nice(current, nice))
214		return -EPERM;
215
216	/* this is a heavy operation taking global locks.. */
217	if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
218		return -EAGAIN;
219
220	next = HZ / 10 + jiffies;
221	ag = autogroup_task_get(p);
222
223	down_write(&ag->lock);
224	err = sched_group_set_shares(ag->tg, prio_to_weight[nice + 20]);
225	if (!err)
226		ag->nice = nice;
227	up_write(&ag->lock);
228
229	autogroup_kref_put(ag);
230
231	return err;
232}
233
234void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
235{
236	struct autogroup *ag = autogroup_task_get(p);
237
238	if (!task_group_is_autogroup(ag->tg))
239		goto out;
240
241	down_read(&ag->lock);
242	seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
243	up_read(&ag->lock);
244
245out:
246	autogroup_kref_put(ag);
247}
248#endif /* CONFIG_PROC_FS */
249
250#ifdef CONFIG_SCHED_DEBUG
251int autogroup_path(struct task_group *tg, char *buf, int buflen)
252{
253	if (!task_group_is_autogroup(tg))
254		return 0;
255
256	return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
257}
258#endif /* CONFIG_SCHED_DEBUG */
259
260#endif /* CONFIG_SCHED_AUTOGROUP */