Root/kernel/sched_autogroup.c

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 */
276

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