kernel/sched/auto_group.c

   1 #ifdef CONFIG_SCHED_AUTOGROUP
   2
   3 #include "sched.h"
   4
   5 #include <linux/proc_fs.h>
   6 #include <linux/seq_file.h>
   7 #include <linux/kallsyms.h>
   8 #include <linux/utsname.h>
   9 #include <linux/security.h>
  10 #include <linux/export.h>
  11
  12 unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
  13 static struct autogroup autogroup_default;
  14 static atomic_t autogroup_seq_nr;
  15
  16 void __init autogroup_init(struct task_struct *init_task)
  17 {
  18         autogroup_default.tg = &root_task_group;
  19         kref_init(&autogroup_default.kref);
  20         init_rwsem(&autogroup_default.lock);
  21         init_task->signal->autogroup = &autogroup_default;
  22 }
  23
  24 void autogroup_free(struct task_group *tg)
  25 {
  26         kfree(tg->autogroup);
  27 }
  28
  29 static inline void autogroup_destroy(struct kref *kref)
  30 {
  31         struct autogroup *ag = container_of(kref, struct autogroup, kref);
  32
  33 #ifdef CONFIG_RT_GROUP_SCHED
  34         /* We've redirected RT tasks to the root task group... */
  35         ag->tg->rt_se = NULL;
  36         ag->tg->rt_rq = NULL;
  37 #endif
  38         sched_offline_group(ag->tg);
  39         sched_destroy_group(ag->tg);
  40 }
  41
  42 static inline void autogroup_kref_put(struct autogroup *ag)
  43 {
  44         kref_put(&ag->kref, autogroup_destroy);
  45 }
  46
  47 static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
  48 {
  49         kref_get(&ag->kref);
  50         return ag;
  51 }
  52
  53 static inline struct autogroup *autogroup_task_get(struct task_struct *p)
  54 {
  55         struct autogroup *ag;
  56         unsigned long flags;
  57
  58         if (!lock_task_sighand(p, &flags))
  59                 return autogroup_kref_get(&autogroup_default);
  60
  61         ag = autogroup_kref_get(p->signal->autogroup);
  62         unlock_task_sighand(p, &flags);
  63
  64         return ag;
  65 }
  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         sched_online_group(tg, &root_task_group);
 100         return ag;
 101
 102 out_free:
 103         kfree(ag);
 104 out_fail:
 105         if (printk_ratelimit()) {
 106                 printk(KERN_WARNING "autogroup_create: %s failure.\n",
 107                         ag ? "sched_create_group()" : "kmalloc()");
 108         }
 109
 110         return autogroup_kref_get(&autogroup_default);
 111 }
 112
 113 bool 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 void
 132 autogroup_move_group(struct task_struct *p, struct autogroup *ag)
 133 {
 134         struct autogroup *prev;
 135         struct task_struct *t;
 136         unsigned long flags;
 137
 138         BUG_ON(!lock_task_sighand(p, &flags));
 139
 140         prev = p->signal->autogroup;
 141         if (prev == ag) {
 142                 unlock_task_sighand(p, &flags);
 143                 return;
 144         }
 145
 146         p->signal->autogroup = autogroup_kref_get(ag);
 147
 148         if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
 149                 goto out;
 150
 151         for_each_thread(p, t)
 152                 sched_move_task(t);
 153 out:
 154         unlock_task_sighand(p, &flags);
 155         autogroup_kref_put(prev);
 156 }
 157
 158 /* Allocates GFP_KERNEL, cannot be called under any spinlock */
 159 void sched_autogroup_create_attach(struct task_struct *p)
 160 {
 161         struct autogroup *ag = autogroup_create();
 162
 163         autogroup_move_group(p, ag);
 164         /* drop extra reference added by autogroup_create() */
 165         autogroup_kref_put(ag);
 166 }
 167 EXPORT_SYMBOL(sched_autogroup_create_attach);
 168
 169 /* Cannot be called under siglock.  Currently has no users */
 170 void sched_autogroup_detach(struct task_struct *p)
 171 {
 172         autogroup_move_group(p, &autogroup_default);
 173 }
 174 EXPORT_SYMBOL(sched_autogroup_detach);
 175
 176 void sched_autogroup_fork(struct signal_struct *sig)
 177 {
 178         sig->autogroup = autogroup_task_get(current);
 179 }
 180
 181 void sched_autogroup_exit(struct signal_struct *sig)
 182 {
 183         autogroup_kref_put(sig->autogroup);
 184 }
 185
 186 static int __init setup_autogroup(char *str)
 187 {
 188         sysctl_sched_autogroup_enabled = 0;
 189
 190         return 1;
 191 }
 192
 193 __setup("noautogroup", setup_autogroup);
 194
 195 #ifdef CONFIG_PROC_FS
 196
 197 int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
 198 {
 199         static unsigned long next = INITIAL_JIFFIES;
 200         struct autogroup *ag;
 201         int err;
 202
 203         if (nice < MIN_NICE || nice > MAX_NICE)
 204                 return -EINVAL;
 205
 206         err = security_task_setnice(current, nice);
 207         if (err)
 208                 return err;
 209
 210         if (nice < 0 && !can_nice(current, nice))
 211                 return -EPERM;
 212
 213         /* this is a heavy operation taking global locks.. */
 214         if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
 215                 return -EAGAIN;
 216
 217         next = HZ / 10 + jiffies;
 218         ag = autogroup_task_get(p);
 219
 220         down_write(&ag->lock);
 221         err = sched_group_set_shares(ag->tg, prio_to_weight[nice + 20]);
 222         if (!err)
 223                 ag->nice = nice;
 224         up_write(&ag->lock);
 225
 226         autogroup_kref_put(ag);
 227
 228         return err;
 229 }
 230
 231 void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
 232 {
 233         struct autogroup *ag = autogroup_task_get(p);
 234
 235         if (!task_group_is_autogroup(ag->tg))
 236                 goto out;
 237
 238         down_read(&ag->lock);
 239         seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
 240         up_read(&ag->lock);
 241
 242 out:
 243         autogroup_kref_put(ag);
 244 }
 245 #endif /* CONFIG_PROC_FS */
 246
 247 #ifdef CONFIG_SCHED_DEBUG
 248 int autogroup_path(struct task_group *tg, char *buf, int buflen)
 249 {
 250         if (!task_group_is_autogroup(tg))
 251                 return 0;
 252
 253         return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
 254 }
 255 #endif /* CONFIG_SCHED_DEBUG */
 256
 257 #endif /* CONFIG_SCHED_AUTOGROUP */