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 #ifdef CONFIG_RT_GROUP_SCHED
  31         /* We've redirected RT tasks to the root task group... */
  32         ag->tg->rt_se = NULL;
  33         ag->tg->rt_rq = NULL;
  34 #endif
  35         sched_destroy_group(ag->tg);
  36 }
  37
  38 static inline void autogroup_kref_put(struct autogroup *ag)
  39 {
  40         kref_put(&ag->kref, autogroup_destroy);
  41 }
  42
  43 static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
  44 {
  45         kref_get(&ag->kref);
  46         return ag;
  47 }
  48
  49 static inline struct autogroup *autogroup_task_get(struct task_struct *p)
  50 {
  51         struct autogroup *ag;
  52         unsigned long flags;
  53
  54         if (!lock_task_sighand(p, &flags))
  55                 return autogroup_kref_get(&autogroup_default);
  56
  57         ag = autogroup_kref_get(p->signal->autogroup);
  58         unlock_task_sighand(p, &flags);
  59
  60         return ag;
  61 }
  62
  63 #ifdef CONFIG_RT_GROUP_SCHED
  64 static void free_rt_sched_group(struct task_group *tg);
  65 #endif
  66
  67 static inline struct autogroup *autogroup_create(void)
  68 {
  69         struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL);
  70         struct task_group *tg;
  71
  72         if (!ag)
  73                 goto out_fail;
  74
  75         tg = sched_create_group(&root_task_group);
  76
  77         if (IS_ERR(tg))
  78                 goto out_free;
  79
  80         kref_init(&ag->kref);
  81         init_rwsem(&ag->lock);
  82         ag->id = atomic_inc_return(&autogroup_seq_nr);
  83         ag->tg = tg;
  84 #ifdef CONFIG_RT_GROUP_SCHED
  85         /*
  86          * Autogroup RT tasks are redirected to the root task group
  87          * so we don't have to move tasks around upon policy change,
  88          * or flail around trying to allocate bandwidth on the fly.
  89          * A bandwidth exception in __sched_setscheduler() allows
  90          * the policy change to proceed.  Thereafter, task_group()
  91          * returns &root_task_group, so zero bandwidth is required.
  92          */
  93         free_rt_sched_group(tg);
  94         tg->rt_se = root_task_group.rt_se;
  95         tg->rt_rq = root_task_group.rt_rq;
  96 #endif
  97         tg->autogroup = ag;
  98
  99         return ag;
 100
 101 out_free:
 102         kfree(ag);
 103 out_fail:
 104         if (printk_ratelimit()) {
 105                 printk(KERN_WARNING "autogroup_create: %s failure.\n",
 106                         ag ? "sched_create_group()" : "kmalloc()");
 107         }
 108
 109         return autogroup_kref_get(&autogroup_default);
 110 }
 111
 112 static inline bool
 113 task_wants_autogroup(struct task_struct *p, struct task_group *tg)
 114 {
 115         if (tg != &root_task_group)
 116                 return false;
 117
 118         if (p->sched_class != &fair_sched_class)
 119                 return false;
 120
 121         /*
 122          * We can only assume the task group can't go away on us if
 123          * autogroup_move_group() can see us on ->thread_group list.
 124          */
 125         if (p->flags & PF_EXITING)
 126                 return false;
 127
 128         return true;
 129 }
 130
 131 static inline bool task_group_is_autogroup(struct task_group *tg)
 132 {
 133         return tg != &root_task_group && tg->autogroup;
 134 }
 135
 136 static inline struct task_group *
 137 autogroup_task_group(struct task_struct *p, struct task_group *tg)
 138 {
 139         int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
 140
 141         if (enabled && task_wants_autogroup(p, tg))
 142                 return p->signal->autogroup->tg;
 143
 144         return tg;
 145 }
 146
 147 static void
 148 autogroup_move_group(struct task_struct *p, struct autogroup *ag)
 149 {
 150         struct autogroup *prev;
 151         struct task_struct *t;
 152         unsigned long flags;
 153
 154         BUG_ON(!lock_task_sighand(p, &flags));
 155
 156         prev = p->signal->autogroup;
 157         if (prev == ag) {
 158                 unlock_task_sighand(p, &flags);
 159                 return;
 160         }
 161
 162         p->signal->autogroup = autogroup_kref_get(ag);
 163
 164         t = p;
 165         do {
 166                 sched_move_task(t);
 167         } while_each_thread(p, t);
 168
 169         unlock_task_sighand(p, &flags);
 170         autogroup_kref_put(prev);
 171 }
 172
 173 /* Allocates GFP_KERNEL, cannot be called under any spinlock */
 174 void sched_autogroup_create_attach(struct task_struct *p)
 175 {
 176         struct autogroup *ag = autogroup_create();
 177
 178         autogroup_move_group(p, ag);
 179         /* drop extra refrence added by autogroup_create() */
 180         autogroup_kref_put(ag);
 181 }
 182 EXPORT_SYMBOL(sched_autogroup_create_attach);
 183
 184 /* Cannot be called under siglock.  Currently has no users */
 185 void sched_autogroup_detach(struct task_struct *p)
 186 {
 187         autogroup_move_group(p, &autogroup_default);
 188 }
 189 EXPORT_SYMBOL(sched_autogroup_detach);
 190
 191 void sched_autogroup_fork(struct signal_struct *sig)
 192 {
 193         sig->autogroup = autogroup_task_get(current);
 194 }
 195
 196 void sched_autogroup_exit(struct signal_struct *sig)
 197 {
 198         autogroup_kref_put(sig->autogroup);
 199 }
 200
 201 static int __init setup_autogroup(char *str)
 202 {
 203         sysctl_sched_autogroup_enabled = 0;
 204
 205         return 1;
 206 }
 207
 208 __setup("noautogroup", setup_autogroup);
 209
 210 #ifdef CONFIG_PROC_FS
 211
 212 int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice)
 213 {
 214         static unsigned long next = INITIAL_JIFFIES;
 215         struct autogroup *ag;
 216         int err;
 217
 218         if (*nice < -20 || *nice > 19)
 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
 235         down_write(&ag->lock);
 236         err = sched_group_set_shares(ag->tg, prio_to_weight[*nice + 20]);
 237         if (!err)
 238                 ag->nice = *nice;
 239         up_write(&ag->lock);
 240
 241         autogroup_kref_put(ag);
 242
 243         return err;
 244 }
 245
 246 void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
 247 {
 248         struct autogroup *ag = autogroup_task_get(p);
 249
 250         down_read(&ag->lock);
 251         seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
 252         up_read(&ag->lock);
 253
 254         autogroup_kref_put(ag);
 255 }
 256 #endif /* CONFIG_PROC_FS */
 257
 258 #ifdef CONFIG_SCHED_DEBUG
 259 static inline int autogroup_path(struct task_group *tg, char *buf, int buflen)
 260 {
 261         int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
 262
 263         if (!enabled || !tg->autogroup)
 264                 return 0;
 265
 266         return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
 267 }
 268 #endif /* CONFIG_SCHED_DEBUG */
 269
 270 #endif /* CONFIG_SCHED_AUTOGROUP */