1#include "sched.h"
  2
  3#include <linux/proc_fs.h>
  4#include <linux/seq_file.h>
  5#include <linux/kallsyms.h>
  6#include <linux/utsname.h>
  7#include <linux/security.h>
  8#include <linux/export.h>
  9
 10unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
 11static struct autogroup autogroup_default;
 12static atomic_t autogroup_seq_nr;
 13
 14void __init autogroup_init(struct task_struct *init_task)
 15{
 16	autogroup_default.tg = &root_task_group;
 17	kref_init(&autogroup_default.kref);
 18	init_rwsem(&autogroup_default.lock);
 19	init_task->signal->autogroup = &autogroup_default;
 20}
 21
 22void autogroup_free(struct task_group *tg)
 23{
 24	kfree(tg->autogroup);
 25}
 26
 27static inline void autogroup_destroy(struct kref *kref)
 28{
 29	struct autogroup *ag = container_of(kref, struct autogroup, kref);
 30
 31#ifdef CONFIG_RT_GROUP_SCHED
 32	/* We've redirected RT tasks to the root task group... */
 33	ag->tg->rt_se = NULL;
 34	ag->tg->rt_rq = NULL;
 35#endif
 36	sched_offline_group(ag->tg);
 37	sched_destroy_group(ag->tg);
 38}
 39
 40static inline void autogroup_kref_put(struct autogroup *ag)
 41{
 42	kref_put(&ag->kref, autogroup_destroy);
 43}
 44
 45static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
 46{
 47	kref_get(&ag->kref);
 48	return ag;
 49}
 50
 51static inline struct autogroup *autogroup_task_get(struct task_struct *p)
 52{
 53	struct autogroup *ag;
 54	unsigned long flags;
 55
 56	if (!lock_task_sighand(p, &flags))
 57		return autogroup_kref_get(&autogroup_default);
 58
 59	ag = autogroup_kref_get(p->signal->autogroup);
 60	unlock_task_sighand(p, &flags);
 61
 62	return ag;
 63}
 64
 65static inline struct autogroup *autogroup_create(void)
 66{
 67	struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL);
 68	struct task_group *tg;
 69
 70	if (!ag)
 71		goto out_fail;
 72
 73	tg = sched_create_group(&root_task_group);
 74
 75	if (IS_ERR(tg))
 76		goto out_free;
 77
 78	kref_init(&ag->kref);
 79	init_rwsem(&ag->lock);
 80	ag->id = atomic_inc_return(&autogroup_seq_nr);
 81	ag->tg = tg;
 82#ifdef CONFIG_RT_GROUP_SCHED
 83	/*
 84	 * Autogroup RT tasks are redirected to the root task group
 85	 * so we don't have to move tasks around upon policy change,
 86	 * or flail around trying to allocate bandwidth on the fly.
 87	 * A bandwidth exception in __sched_setscheduler() allows
 88	 * the policy change to proceed.
 89	 */
 90	free_rt_sched_group(tg);
 91	tg->rt_se = root_task_group.rt_se;
 92	tg->rt_rq = root_task_group.rt_rq;
 93#endif
 94	tg->autogroup = ag;
 95
 96	sched_online_group(tg, &root_task_group);
 97	return ag;
 98
 99out_free:
100	kfree(ag);
101out_fail:
102	if (printk_ratelimit()) {
103		printk(KERN_WARNING "autogroup_create: %s failure.\n",
104			ag ? "sched_create_group()" : "kmalloc()");
105	}
106
107	return autogroup_kref_get(&autogroup_default);
108}
109
110bool task_wants_autogroup(struct task_struct *p, struct task_group *tg)
111{
112	if (tg != &root_task_group)
113		return false;
114	/*
115	 * If we race with autogroup_move_group() the caller can use the old
116	 * value of signal->autogroup but in this case sched_move_task() will
117	 * be called again before autogroup_kref_put().
118	 *
119	 * However, there is no way sched_autogroup_exit_task() could tell us
120	 * to avoid autogroup->tg, so we abuse PF_EXITING flag for this case.
121	 */
122	if (p->flags & PF_EXITING)
123		return false;
124
125	return true;
126}
127
128void sched_autogroup_exit_task(struct task_struct *p)
129{
130	/*
131	 * We are going to call exit_notify() and autogroup_move_group() can't
132	 * see this thread after that: we can no longer use signal->autogroup.
133	 * See the PF_EXITING check in task_wants_autogroup().
134	 */
135	sched_move_task(p);
136}
137
138static void
139autogroup_move_group(struct task_struct *p, struct autogroup *ag)
140{
141	struct autogroup *prev;
142	struct task_struct *t;
143	unsigned long flags;
144
145	BUG_ON(!lock_task_sighand(p, &flags));
146
147	prev = p->signal->autogroup;
148	if (prev == ag) {
149		unlock_task_sighand(p, &flags);
150		return;
151	}
152
153	p->signal->autogroup = autogroup_kref_get(ag);
154	/*
155	 * We can't avoid sched_move_task() after we changed signal->autogroup,
156	 * this process can already run with task_group() == prev->tg or we can
157	 * race with cgroup code which can read autogroup = prev under rq->lock.
158	 * In the latter case for_each_thread() can not miss a migrating thread,
159	 * cpu_cgroup_attach() must not be possible after cgroup_exit() and it
160	 * can't be removed from thread list, we hold ->siglock.
161	 *
162	 * If an exiting thread was already removed from thread list we rely on
163	 * sched_autogroup_exit_task().
164	 */
165	for_each_thread(p, t)
166		sched_move_task(t);
167
168	unlock_task_sighand(p, &flags);
169	autogroup_kref_put(prev);
170}
171
172/* Allocates GFP_KERNEL, cannot be called under any spinlock */
173void sched_autogroup_create_attach(struct task_struct *p)
174{
175	struct autogroup *ag = autogroup_create();
176
177	autogroup_move_group(p, ag);
178	/* drop extra reference added by autogroup_create() */
179	autogroup_kref_put(ag);
180}
181EXPORT_SYMBOL(sched_autogroup_create_attach);
182
183/* Cannot be called under siglock.  Currently has no users */
184void sched_autogroup_detach(struct task_struct *p)
185{
186	autogroup_move_group(p, &autogroup_default);
187}
188EXPORT_SYMBOL(sched_autogroup_detach);
189
190void sched_autogroup_fork(struct signal_struct *sig)
191{
192	sig->autogroup = autogroup_task_get(current);
193}
194
195void sched_autogroup_exit(struct signal_struct *sig)
196{
197	autogroup_kref_put(sig->autogroup);
198}
199
200static int __init setup_autogroup(char *str)
201{
202	sysctl_sched_autogroup_enabled = 0;
203
204	return 1;
205}
206
207__setup("noautogroup", setup_autogroup);
208
209#ifdef CONFIG_PROC_FS
210
211int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
212{
213	static unsigned long next = INITIAL_JIFFIES;
214	struct autogroup *ag;
215	unsigned long shares;
216	int err;
217
218	if (nice < MIN_NICE || nice > MAX_NICE)
219		return -EINVAL;
220
221	err = security_task_setnice(current, nice);
222	if (err)
223		return err;
224
225	if (nice < 0 && !can_nice(current, nice))
226		return -EPERM;
227
228	/* this is a heavy operation taking global locks.. */
229	if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
230		return -EAGAIN;
231
232	next = HZ / 10 + jiffies;
233	ag = autogroup_task_get(p);
234	shares = scale_load(sched_prio_to_weight[nice + 20]);
235
236	down_write(&ag->lock);
237	err = sched_group_set_shares(ag->tg, shares);
238	if (!err)
239		ag->nice = nice;
240	up_write(&ag->lock);
241
242	autogroup_kref_put(ag);
243
244	return err;
245}
246
247void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
248{
249	struct autogroup *ag = autogroup_task_get(p);
250
251	if (!task_group_is_autogroup(ag->tg))
252		goto out;
253
254	down_read(&ag->lock);
255	seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
256	up_read(&ag->lock);
257
258out:
259	autogroup_kref_put(ag);
260}
261#endif /* CONFIG_PROC_FS */
262
263#ifdef CONFIG_SCHED_DEBUG
264int autogroup_path(struct task_group *tg, char *buf, int buflen)
265{
266	if (!task_group_is_autogroup(tg))
267		return 0;
268
269	return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
270}
271#endif /* CONFIG_SCHED_DEBUG */