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_destroy_group(ag->tg);
 39}
 40
 41static inline void autogroup_kref_put(struct autogroup *ag)
 42{
 43	kref_put(&ag->kref, autogroup_destroy);
 44}
 45
 46static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
 47{
 48	kref_get(&ag->kref);
 49	return ag;
 50}
 51
 52static inline struct autogroup *autogroup_task_get(struct task_struct *p)
 53{
 54	struct autogroup *ag;
 55	unsigned long flags;
 56
 57	if (!lock_task_sighand(p, &flags))
 58		return autogroup_kref_get(&autogroup_default);
 59
 60	ag = autogroup_kref_get(p->signal->autogroup);
 61	unlock_task_sighand(p, &flags);
 62
 63	return ag;
 64}
 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
111bool task_wants_autogroup(struct task_struct *p, struct task_group *tg)
112{
113	if (tg != &root_task_group)
114		return false;
115
116	if (p->sched_class != &fair_sched_class)
117		return false;
118
119	/*
120	 * We can only assume the task group can't go away on us if
121	 * autogroup_move_group() can see us on ->thread_group list.
122	 */
123	if (p->flags & PF_EXITING)
124		return false;
125
126	return true;
127}
128
129static void
130autogroup_move_group(struct task_struct *p, struct autogroup *ag)
131{
132	struct autogroup *prev;
133	struct task_struct *t;
134	unsigned long flags;
135
136	BUG_ON(!lock_task_sighand(p, &flags));
137
138	prev = p->signal->autogroup;
139	if (prev == ag) {
140		unlock_task_sighand(p, &flags);
141		return;
142	}
143
144	p->signal->autogroup = autogroup_kref_get(ag);
145
146	if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
147		goto out;
148
149	t = p;
150	do {
151		sched_move_task(t);
152	} while_each_thread(p, t);
153
154out:
155	unlock_task_sighand(p, &flags);
156	autogroup_kref_put(prev);
157}
158
159/* Allocates GFP_KERNEL, cannot be called under any spinlock */
160void sched_autogroup_create_attach(struct task_struct *p)
161{
162	struct autogroup *ag = autogroup_create();
163
164	autogroup_move_group(p, ag);
165	/* drop extra reference added by autogroup_create() */
166	autogroup_kref_put(ag);
167}
168EXPORT_SYMBOL(sched_autogroup_create_attach);
169
170/* Cannot be called under siglock.  Currently has no users */
171void sched_autogroup_detach(struct task_struct *p)
172{
173	autogroup_move_group(p, &autogroup_default);
174}
175EXPORT_SYMBOL(sched_autogroup_detach);
176
177void sched_autogroup_fork(struct signal_struct *sig)
178{
179	sig->autogroup = autogroup_task_get(current);
180}
181
182void sched_autogroup_exit(struct signal_struct *sig)
183{
184	autogroup_kref_put(sig->autogroup);
185}
186
187static int __init setup_autogroup(char *str)
188{
189	sysctl_sched_autogroup_enabled = 0;
190
191	return 1;
192}
193
194__setup("noautogroup", setup_autogroup);
195
196#ifdef CONFIG_PROC_FS
197
198int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
199{
200	static unsigned long next = INITIAL_JIFFIES;
201	struct autogroup *ag;
202	int err;
203
204	if (nice < -20 || nice > 19)
205		return -EINVAL;
206
207	err = security_task_setnice(current, nice);
208	if (err)
209		return err;
210
211	if (nice < 0 && !can_nice(current, nice))
212		return -EPERM;
213
214	/* this is a heavy operation taking global locks.. */
215	if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
216		return -EAGAIN;
217
218	next = HZ / 10 + jiffies;
219	ag = autogroup_task_get(p);
220
221	down_write(&ag->lock);
222	err = sched_group_set_shares(ag->tg, prio_to_weight[nice + 20]);
223	if (!err)
224		ag->nice = nice;
225	up_write(&ag->lock);
226
227	autogroup_kref_put(ag);
228
229	return err;
230}
231
232void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
233{
234	struct autogroup *ag = autogroup_task_get(p);
235
236	if (!task_group_is_autogroup(ag->tg))
237		goto out;
238
239	down_read(&ag->lock);
240	seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
241	up_read(&ag->lock);
242
243out:
244	autogroup_kref_put(ag);
245}
246#endif /* CONFIG_PROC_FS */
247
248#ifdef CONFIG_SCHED_DEBUG
249int autogroup_path(struct task_group *tg, char *buf, int buflen)
250{
251	if (!task_group_is_autogroup(tg))
252		return 0;
253
254	return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
255}
256#endif /* CONFIG_SCHED_DEBUG */
257
258#endif /* CONFIG_SCHED_AUTOGROUP */