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
   8 unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
   9 static struct autogroup autogroup_default;
  10 static atomic_t autogroup_seq_nr;
  11
  12 static 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
  20 static inline void autogroup_free(struct task_group *tg)
  21 {
  22         kfree(tg->autogroup);
  23 }
  24
  25 static 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
  37 static inline void autogroup_kref_put(struct autogroup *ag)
  38 {
  39         kref_put(&ag->kref, autogroup_destroy);
  40 }
  41
  42 static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
  43 {
  44         kref_get(&ag->kref);
  45         return ag;
  46 }
  47
  48 static 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
  63 static void free_rt_sched_group(struct task_group *tg);
  64 #endif
  65
  66 static 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
 100 out_free:
 101         kfree(ag);
 102 out_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
 111 static inline bool
 112 task_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
 130 static inline bool task_group_is_autogroup(struct task_group *tg)
 131 {
 132         return !!tg->autogroup;
 133 }
 134
 135 static inline struct task_group *
 136 autogroup_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
 146 static void
 147 autogroup_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
 171 out:
 172         unlock_task_sighand(p, &flags);
 173         autogroup_kref_put(prev);
 174 }
 175
 176 /* Allocates GFP_KERNEL, cannot be called under any spinlock */
 177 void 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 }
 185 EXPORT_SYMBOL(sched_autogroup_create_attach);
 186
 187 /* Cannot be called under siglock.  Currently has no users */
 188 void sched_autogroup_detach(struct task_struct *p)
 189 {
 190         autogroup_move_group(p, &autogroup_default);
 191 }
 192 EXPORT_SYMBOL(sched_autogroup_detach);
 193
 194 void sched_autogroup_fork(struct signal_struct *sig)
 195 {
 196         sig->autogroup = autogroup_task_get(current);
 197 }
 198
 199 void sched_autogroup_exit(struct signal_struct *sig)
 200 {
 201         autogroup_kref_put(sig->autogroup);
 202 }
 203
 204 static 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
 215 int 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
 249 void 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
 260 out:
 261         autogroup_kref_put(ag);
 262 }
 263 #endif /* CONFIG_PROC_FS */
 264
 265 #ifdef CONFIG_SCHED_DEBUG
 266 static 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 */