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.
  90          */
  91         free_rt_sched_group(tg);
  92         tg->rt_se = root_task_group.rt_se;
  93         tg->rt_rq = root_task_group.rt_rq;
  94 #endif
  95         tg->autogroup = ag;
  96
  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 static inline bool
 111 task_wants_autogroup(struct task_struct *p, struct task_group *tg)
 112 {
 113         if (tg != &root_task_group)
 114                 return false;
 115
 116         /*
 117          * We can only assume the task group can't go away on us if
 118          * autogroup_move_group() can see us on ->thread_group list.
 119          */
 120         if (p->flags & PF_EXITING)
 121                 return false;
 122
 123         return true;
 124 }
 125
 126 static inline bool task_group_is_autogroup(struct task_group *tg)
 127 {
 128         return !!tg->autogroup;
 129 }
 130
 131 static inline struct task_group *
 132 autogroup_task_group(struct task_struct *p, struct task_group *tg)
 133 {
 134         int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
 135
 136         if (enabled && task_wants_autogroup(p, tg))
 137                 return p->signal->autogroup->tg;
 138
 139         return tg;
 140 }
 141
 142 static void
 143 autogroup_move_group(struct task_struct *p, struct autogroup *ag)
 144 {
 145         struct autogroup *prev;
 146         struct task_struct *t;
 147         unsigned long flags;
 148
 149         BUG_ON(!lock_task_sighand(p, &flags));
 150
 151         prev = p->signal->autogroup;
 152         if (prev == ag) {
 153                 unlock_task_sighand(p, &flags);
 154                 return;
 155         }
 156
 157         p->signal->autogroup = autogroup_kref_get(ag);
 158
 159         t = p;
 160         do {
 161                 sched_move_task(t);
 162         } while_each_thread(p, t);
 163
 164         unlock_task_sighand(p, &flags);
 165         autogroup_kref_put(prev);
 166 }
 167
 168 /* Allocates GFP_KERNEL, cannot be called under any spinlock */
 169 void sched_autogroup_create_attach(struct task_struct *p)
 170 {
 171         struct autogroup *ag = autogroup_create();
 172
 173         autogroup_move_group(p, ag);
 174         /* drop extra reference added by autogroup_create() */
 175         autogroup_kref_put(ag);
 176 }
 177 EXPORT_SYMBOL(sched_autogroup_create_attach);
 178
 179 /* Cannot be called under siglock.  Currently has no users */
 180 void sched_autogroup_detach(struct task_struct *p)
 181 {
 182         autogroup_move_group(p, &autogroup_default);
 183 }
 184 EXPORT_SYMBOL(sched_autogroup_detach);
 185
 186 void sched_autogroup_fork(struct signal_struct *sig)
 187 {
 188         sig->autogroup = autogroup_task_get(current);
 189 }
 190
 191 void sched_autogroup_exit(struct signal_struct *sig)
 192 {
 193         autogroup_kref_put(sig->autogroup);
 194 }
 195
 196 static int __init setup_autogroup(char *str)
 197 {
 198         sysctl_sched_autogroup_enabled = 0;
 199
 200         return 1;
 201 }
 202
 203 __setup("noautogroup", setup_autogroup);
 204
 205 #ifdef CONFIG_PROC_FS
 206
 207 int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice)
 208 {
 209         static unsigned long next = INITIAL_JIFFIES;
 210         struct autogroup *ag;
 211         int err;
 212
 213         if (*nice < -20 || *nice > 19)
 214                 return -EINVAL;
 215
 216         err = security_task_setnice(current, *nice);
 217         if (err)
 218                 return err;
 219
 220         if (*nice < 0 && !can_nice(current, *nice))
 221                 return -EPERM;
 222
 223         /* this is a heavy operation taking global locks.. */
 224         if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
 225                 return -EAGAIN;
 226
 227         next = HZ / 10 + jiffies;
 228         ag = autogroup_task_get(p);
 229
 230         down_write(&ag->lock);
 231         err = sched_group_set_shares(ag->tg, prio_to_weight[*nice + 20]);
 232         if (!err)
 233                 ag->nice = *nice;
 234         up_write(&ag->lock);
 235
 236         autogroup_kref_put(ag);
 237
 238         return err;
 239 }
 240
 241 void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
 242 {
 243         struct autogroup *ag = autogroup_task_get(p);
 244
 245         if (!task_group_is_autogroup(ag->tg))
 246                 goto out;
 247
 248         down_read(&ag->lock);
 249         seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
 250         up_read(&ag->lock);
 251
 252 out:
 253         autogroup_kref_put(ag);
 254 }
 255 #endif /* CONFIG_PROC_FS */
 256
 257 #ifdef CONFIG_SCHED_DEBUG
 258 static inline int autogroup_path(struct task_group *tg, char *buf, int buflen)
 259 {
 260         if (!task_group_is_autogroup(tg))
 261                 return 0;
 262
 263         return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
 264 }
 265 #endif /* CONFIG_SCHED_DEBUG */
 266
 267 #endif /* CONFIG_SCHED_AUTOGROUP */