kernel/sched/auto_group.c

   1 #include "sched.h"
   2
   3 #include <linux/proc_fs.h>
   4 #include <linux/seq_file.h>
   5 #include <linux/kallsyms.h>
   6 #include <linux/utsname.h>
   7 #include <linux/security.h>
   8 #include <linux/export.h>
   9
  10 unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
  11 static struct autogroup autogroup_default;
  12 static atomic_t autogroup_seq_nr;
  13
  14 void __init autogroup_init(struct task_struct *init_task)
  15 {
  16         autogroup_default.tg = &root_task_group;
  17         kref_init(&autogroup_default.kref);
  18         init_rwsem(&autogroup_default.lock);
  19         init_task->signal->autogroup = &autogroup_default;
  20 }
  21
  22 void autogroup_free(struct task_group *tg)
  23 {
  24         kfree(tg->autogroup);
  25 }
  26
  27 static inline void autogroup_destroy(struct kref *kref)
  28 {
  29         struct autogroup *ag = container_of(kref, struct autogroup, kref);
  30
  31 #ifdef CONFIG_RT_GROUP_SCHED
  32         /* We've redirected RT tasks to the root task group... */
  33         ag->tg->rt_se = NULL;
  34         ag->tg->rt_rq = NULL;
  35 #endif
  36         sched_offline_group(ag->tg);
  37         sched_destroy_group(ag->tg);
  38 }
  39
  40 static inline void autogroup_kref_put(struct autogroup *ag)
  41 {
  42         kref_put(&ag->kref, autogroup_destroy);
  43 }
  44
  45 static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
  46 {
  47         kref_get(&ag->kref);
  48         return ag;
  49 }
  50
  51 static inline struct autogroup *autogroup_task_get(struct task_struct *p)
  52 {
  53         struct autogroup *ag;
  54         unsigned long flags;
  55
  56         if (!lock_task_sighand(p, &flags))
  57                 return autogroup_kref_get(&autogroup_default);
  58
  59         ag = autogroup_kref_get(p->signal->autogroup);
  60         unlock_task_sighand(p, &flags);
  61
  62         return ag;
  63 }
  64
  65 static inline struct autogroup *autogroup_create(void)
  66 {
  67         struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL);
  68         struct task_group *tg;
  69
  70         if (!ag)
  71                 goto out_fail;
  72
  73         tg = sched_create_group(&root_task_group);
  74
  75         if (IS_ERR(tg))
  76                 goto out_free;
  77
  78         kref_init(&ag->kref);
  79         init_rwsem(&ag->lock);
  80         ag->id = atomic_inc_return(&autogroup_seq_nr);
  81         ag->tg = tg;
  82 #ifdef CONFIG_RT_GROUP_SCHED
  83         /*
  84          * Autogroup RT tasks are redirected to the root task group
  85          * so we don't have to move tasks around upon policy change,
  86          * or flail around trying to allocate bandwidth on the fly.
  87          * A bandwidth exception in __sched_setscheduler() allows
  88          * the policy change to proceed.
  89          */
  90         free_rt_sched_group(tg);
  91         tg->rt_se = root_task_group.rt_se;
  92         tg->rt_rq = root_task_group.rt_rq;
  93 #endif
  94         tg->autogroup = ag;
  95
  96         sched_online_group(tg, &root_task_group);
  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 bool task_wants_autogroup(struct task_struct *p, struct task_group *tg)
 111 {
 112         if (tg != &root_task_group)
 113                 return false;
 114
 115         /*
 116          * We can only assume the task group can't go away on us if
 117          * autogroup_move_group() can see us on ->thread_group list.
 118          */
 119         if (p->flags & PF_EXITING)
 120                 return false;
 121
 122         return true;
 123 }
 124
 125 static void
 126 autogroup_move_group(struct task_struct *p, struct autogroup *ag)
 127 {
 128         struct autogroup *prev;
 129         struct task_struct *t;
 130         unsigned long flags;
 131
 132         BUG_ON(!lock_task_sighand(p, &flags));
 133
 134         prev = p->signal->autogroup;
 135         if (prev == ag) {
 136                 unlock_task_sighand(p, &flags);
 137                 return;
 138         }
 139
 140         p->signal->autogroup = autogroup_kref_get(ag);
 141
 142         if (!READ_ONCE(sysctl_sched_autogroup_enabled))
 143                 goto out;
 144
 145         for_each_thread(p, t)
 146                 sched_move_task(t);
 147 out:
 148         unlock_task_sighand(p, &flags);
 149         autogroup_kref_put(prev);
 150 }
 151
 152 /* Allocates GFP_KERNEL, cannot be called under any spinlock */
 153 void sched_autogroup_create_attach(struct task_struct *p)
 154 {
 155         struct autogroup *ag = autogroup_create();
 156
 157         autogroup_move_group(p, ag);
 158         /* drop extra reference added by autogroup_create() */
 159         autogroup_kref_put(ag);
 160 }
 161 EXPORT_SYMBOL(sched_autogroup_create_attach);
 162
 163 /* Cannot be called under siglock.  Currently has no users */
 164 void sched_autogroup_detach(struct task_struct *p)
 165 {
 166         autogroup_move_group(p, &autogroup_default);
 167 }
 168 EXPORT_SYMBOL(sched_autogroup_detach);
 169
 170 void sched_autogroup_fork(struct signal_struct *sig)
 171 {
 172         sig->autogroup = autogroup_task_get(current);
 173 }
 174
 175 void sched_autogroup_exit(struct signal_struct *sig)
 176 {
 177         autogroup_kref_put(sig->autogroup);
 178 }
 179
 180 static int __init setup_autogroup(char *str)
 181 {
 182         sysctl_sched_autogroup_enabled = 0;
 183
 184         return 1;
 185 }
 186
 187 __setup("noautogroup", setup_autogroup);
 188
 189 #ifdef CONFIG_PROC_FS
 190
 191 int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
 192 {
 193         static unsigned long next = INITIAL_JIFFIES;
 194         struct autogroup *ag;
 195         int err;
 196
 197         if (nice < MIN_NICE || nice > MAX_NICE)
 198                 return -EINVAL;
 199
 200         err = security_task_setnice(current, nice);
 201         if (err)
 202                 return err;
 203
 204         if (nice < 0 && !can_nice(current, nice))
 205                 return -EPERM;
 206
 207         /* this is a heavy operation taking global locks.. */
 208         if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
 209                 return -EAGAIN;
 210
 211         next = HZ / 10 + jiffies;
 212         ag = autogroup_task_get(p);
 213
 214         down_write(&ag->lock);
 215         err = sched_group_set_shares(ag->tg, sched_prio_to_weight[nice + 20]);
 216         if (!err)
 217                 ag->nice = nice;
 218         up_write(&ag->lock);
 219
 220         autogroup_kref_put(ag);
 221
 222         return err;
 223 }
 224
 225 void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
 226 {
 227         struct autogroup *ag = autogroup_task_get(p);
 228
 229         if (!task_group_is_autogroup(ag->tg))
 230                 goto out;
 231
 232         down_read(&ag->lock);
 233         seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
 234         up_read(&ag->lock);
 235
 236 out:
 237         autogroup_kref_put(ag);
 238 }
 239 #endif /* CONFIG_PROC_FS */
 240
 241 #ifdef CONFIG_SCHED_DEBUG
 242 int autogroup_path(struct task_group *tg, char *buf, int buflen)
 243 {
 244         if (!task_group_is_autogroup(tg))
 245                 return 0;
 246
 247         return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
 248 }
 249 #endif /* CONFIG_SCHED_DEBUG */