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TOMOYO Linux Cross Reference
Linux/kernel/sched/autogroup.c

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  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 
 10 unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
 11 static struct autogroup autogroup_default;
 12 static atomic_t autogroup_seq_nr;
 13 
 14 void __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 
 22 void autogroup_free(struct task_group *tg)
 23 {
 24         kfree(tg->autogroup);
 25 }
 26 
 27 static 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 
 40 static inline void autogroup_kref_put(struct autogroup *ag)
 41 {
 42         kref_put(&ag->kref, autogroup_destroy);
 43 }
 44 
 45 static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
 46 {
 47         kref_get(&ag->kref);
 48         return ag;
 49 }
 50 
 51 static 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 
 65 static 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 
 99 out_free:
100         kfree(ag);
101 out_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 
110 bool 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 
128 void 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 
138 static void
139 autogroup_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 */
173 void 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 }
181 EXPORT_SYMBOL(sched_autogroup_create_attach);
182 
183 /* Cannot be called under siglock.  Currently has no users */
184 void sched_autogroup_detach(struct task_struct *p)
185 {
186         autogroup_move_group(p, &autogroup_default);
187 }
188 EXPORT_SYMBOL(sched_autogroup_detach);
189 
190 void sched_autogroup_fork(struct signal_struct *sig)
191 {
192         sig->autogroup = autogroup_task_get(current);
193 }
194 
195 void sched_autogroup_exit(struct signal_struct *sig)
196 {
197         autogroup_kref_put(sig->autogroup);
198 }
199 
200 static 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 
211 int 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 
247 void 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 
258 out:
259         autogroup_kref_put(ag);
260 }
261 #endif /* CONFIG_PROC_FS */
262 
263 #ifdef CONFIG_SCHED_DEBUG
264 int 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 */
272 

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