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         root_task_group.autogroup = &autogroup_default;
  16         kref_init(&autogroup_default.kref);
  17         init_rwsem(&autogroup_default.lock);
  18         init_task->signal->autogroup = &autogroup_default;
  19 }
  20
  21 static inline void autogroup_free(struct task_group *tg)
  22 {
  23         kfree(tg->autogroup);
  24 }
  25
  26 static inline void autogroup_destroy(struct kref *kref)
  27 {
  28         struct autogroup *ag = container_of(kref, struct autogroup, kref);
  29
  30         sched_destroy_group(ag->tg);
  31 }
  32
  33 static inline void autogroup_kref_put(struct autogroup *ag)
  34 {
  35         kref_put(&ag->kref, autogroup_destroy);
  36 }
  37
  38 static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
  39 {
  40         kref_get(&ag->kref);
  41         return ag;
  42 }
  43
  44 static inline struct autogroup *autogroup_task_get(struct task_struct *p)
  45 {
  46         struct autogroup *ag;
  47         unsigned long flags;
  48
  49         if (!lock_task_sighand(p, &flags))
  50                 return autogroup_kref_get(&autogroup_default);
  51
  52         ag = autogroup_kref_get(p->signal->autogroup);
  53         unlock_task_sighand(p, &flags);
  54
  55         return ag;
  56 }
  57
  58 static inline struct autogroup *autogroup_create(void)
  59 {
  60         struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL);
  61         struct task_group *tg;
  62
  63         if (!ag)
  64                 goto out_fail;
  65
  66         tg = sched_create_group(&root_task_group);
  67
  68         if (IS_ERR(tg))
  69                 goto out_free;
  70
  71         kref_init(&ag->kref);
  72         init_rwsem(&ag->lock);
  73         ag->id = atomic_inc_return(&autogroup_seq_nr);
  74         ag->tg = tg;
  75         tg->autogroup = ag;
  76
  77         return ag;
  78
  79 out_free:
  80         kfree(ag);
  81 out_fail:
  82         if (printk_ratelimit()) {
  83                 printk(KERN_WARNING "autogroup_create: %s failure.\n",
  84                         ag ? "sched_create_group()" : "kmalloc()");
  85         }
  86
  87         return autogroup_kref_get(&autogroup_default);
  88 }
  89
  90 static inline bool
  91 task_wants_autogroup(struct task_struct *p, struct task_group *tg)
  92 {
  93         if (tg != &root_task_group)
  94                 return false;
  95
  96         if (p->sched_class != &fair_sched_class)
  97                 return false;
  98
  99         /*
 100          * We can only assume the task group can't go away on us if
 101          * autogroup_move_group() can see us on ->thread_group list.
 102          */
 103         if (p->flags & PF_EXITING)
 104                 return false;
 105
 106         return true;
 107 }
 108
 109 static inline struct task_group *
 110 autogroup_task_group(struct task_struct *p, struct task_group *tg)
 111 {
 112         int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
 113
 114         if (enabled && task_wants_autogroup(p, tg))
 115                 return p->signal->autogroup->tg;
 116
 117         return tg;
 118 }
 119
 120 static void
 121 autogroup_move_group(struct task_struct *p, struct autogroup *ag)
 122 {
 123         struct autogroup *prev;
 124         struct task_struct *t;
 125         unsigned long flags;
 126
 127         BUG_ON(!lock_task_sighand(p, &flags));
 128
 129         prev = p->signal->autogroup;
 130         if (prev == ag) {
 131                 unlock_task_sighand(p, &flags);
 132                 return;
 133         }
 134
 135         p->signal->autogroup = autogroup_kref_get(ag);
 136
 137         t = p;
 138         do {
 139                 sched_move_task(t);
 140         } while_each_thread(p, t);
 141
 142         unlock_task_sighand(p, &flags);
 143         autogroup_kref_put(prev);
 144 }
 145
 146 /* Allocates GFP_KERNEL, cannot be called under any spinlock */
 147 void sched_autogroup_create_attach(struct task_struct *p)
 148 {
 149         struct autogroup *ag = autogroup_create();
 150
 151         autogroup_move_group(p, ag);
 152         /* drop extra refrence added by autogroup_create() */
 153         autogroup_kref_put(ag);
 154 }
 155 EXPORT_SYMBOL(sched_autogroup_create_attach);
 156
 157 /* Cannot be called under siglock.  Currently has no users */
 158 void sched_autogroup_detach(struct task_struct *p)
 159 {
 160         autogroup_move_group(p, &autogroup_default);
 161 }
 162 EXPORT_SYMBOL(sched_autogroup_detach);
 163
 164 void sched_autogroup_fork(struct signal_struct *sig)
 165 {
 166         sig->autogroup = autogroup_task_get(current);
 167 }
 168
 169 void sched_autogroup_exit(struct signal_struct *sig)
 170 {
 171         autogroup_kref_put(sig->autogroup);
 172 }
 173
 174 static int __init setup_autogroup(char *str)
 175 {
 176         sysctl_sched_autogroup_enabled = 0;
 177
 178         return 1;
 179 }
 180
 181 __setup("noautogroup", setup_autogroup);
 182
 183 #ifdef CONFIG_PROC_FS
 184
 185 int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice)
 186 {
 187         static unsigned long next = INITIAL_JIFFIES;
 188         struct autogroup *ag;
 189         int err;
 190
 191         if (*nice < -20 || *nice > 19)
 192                 return -EINVAL;
 193
 194         err = security_task_setnice(current, *nice);
 195         if (err)
 196                 return err;
 197
 198         if (*nice < 0 && !can_nice(current, *nice))
 199                 return -EPERM;
 200
 201         /* this is a heavy operation taking global locks.. */
 202         if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
 203                 return -EAGAIN;
 204
 205         next = HZ / 10 + jiffies;
 206         ag = autogroup_task_get(p);
 207
 208         down_write(&ag->lock);
 209         err = sched_group_set_shares(ag->tg, prio_to_weight[*nice + 20]);
 210         if (!err)
 211                 ag->nice = *nice;
 212         up_write(&ag->lock);
 213
 214         autogroup_kref_put(ag);
 215
 216         return err;
 217 }
 218
 219 void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
 220 {
 221         struct autogroup *ag = autogroup_task_get(p);
 222
 223         down_read(&ag->lock);
 224         seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
 225         up_read(&ag->lock);
 226
 227         autogroup_kref_put(ag);
 228 }
 229 #endif /* CONFIG_PROC_FS */
 230
 231 #ifdef CONFIG_SCHED_DEBUG
 232 static inline int autogroup_path(struct task_group *tg, char *buf, int buflen)
 233 {
 234         return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
 235 }
 236 #endif /* CONFIG_SCHED_DEBUG */
 237
 238 #endif /* CONFIG_SCHED_AUTOGROUP */