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_destroy_group(ag->tg);
  39 }
  40
  41 static inline void autogroup_kref_put(struct autogroup *ag)
  42 {
  43         kref_put(&ag->kref, autogroup_destroy);
  44 }
  45
  46 static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
  47 {
  48         kref_get(&ag->kref);
  49         return ag;
  50 }
  51
  52 static inline struct autogroup *autogroup_task_get(struct task_struct *p)
  53 {
  54         struct autogroup *ag;
  55         unsigned long flags;
  56
  57         if (!lock_task_sighand(p, &flags))
  58                 return autogroup_kref_get(&autogroup_default);
  59
  60         ag = autogroup_kref_get(p->signal->autogroup);
  61         unlock_task_sighand(p, &flags);
  62
  63         return ag;
  64 }
  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.  Thereafter, task_group()
  90          * returns &root_task_group, so zero bandwidth is required.
  91          */
  92         free_rt_sched_group(tg);
  93         tg->rt_se = root_task_group.rt_se;
  94         tg->rt_rq = root_task_group.rt_rq;
  95 #endif
  96         tg->autogroup = ag;
  97
  98         return ag;
  99
 100 out_free:
 101         kfree(ag);
 102 out_fail:
 103         if (printk_ratelimit()) {
 104                 printk(KERN_WARNING "autogroup_create: %s failure.\n",
 105                         ag ? "sched_create_group()" : "kmalloc()");
 106         }
 107
 108         return autogroup_kref_get(&autogroup_default);
 109 }
 110
 111 bool task_wants_autogroup(struct task_struct *p, struct task_group *tg)
 112 {
 113         if (tg != &root_task_group)
 114                 return false;
 115
 116         if (p->sched_class != &fair_sched_class)
 117                 return false;
 118
 119         /*
 120          * We can only assume the task group can't go away on us if
 121          * autogroup_move_group() can see us on ->thread_group list.
 122          */
 123         if (p->flags & PF_EXITING)
 124                 return false;
 125
 126         return true;
 127 }
 128
 129 static void
 130 autogroup_move_group(struct task_struct *p, struct autogroup *ag)
 131 {
 132         struct autogroup *prev;
 133         struct task_struct *t;
 134         unsigned long flags;
 135
 136         BUG_ON(!lock_task_sighand(p, &flags));
 137
 138         prev = p->signal->autogroup;
 139         if (prev == ag) {
 140                 unlock_task_sighand(p, &flags);
 141                 return;
 142         }
 143
 144         p->signal->autogroup = autogroup_kref_get(ag);
 145
 146         if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
 147                 goto out;
 148
 149         t = p;
 150         do {
 151                 sched_move_task(t);
 152         } while_each_thread(p, t);
 153
 154 out:
 155         unlock_task_sighand(p, &flags);
 156         autogroup_kref_put(prev);
 157 }
 158
 159 /* Allocates GFP_KERNEL, cannot be called under any spinlock */
 160 void sched_autogroup_create_attach(struct task_struct *p)
 161 {
 162         struct autogroup *ag = autogroup_create();
 163
 164         autogroup_move_group(p, ag);
 165         /* drop extra reference added by autogroup_create() */
 166         autogroup_kref_put(ag);
 167 }
 168 EXPORT_SYMBOL(sched_autogroup_create_attach);
 169
 170 /* Cannot be called under siglock.  Currently has no users */
 171 void sched_autogroup_detach(struct task_struct *p)
 172 {
 173         autogroup_move_group(p, &autogroup_default);
 174 }
 175 EXPORT_SYMBOL(sched_autogroup_detach);
 176
 177 void sched_autogroup_fork(struct signal_struct *sig)
 178 {
 179         sig->autogroup = autogroup_task_get(current);
 180 }
 181
 182 void sched_autogroup_exit(struct signal_struct *sig)
 183 {
 184         autogroup_kref_put(sig->autogroup);
 185 }
 186
 187 static int __init setup_autogroup(char *str)
 188 {
 189         sysctl_sched_autogroup_enabled = 0;
 190
 191         return 1;
 192 }
 193
 194 __setup("noautogroup", setup_autogroup);
 195
 196 #ifdef CONFIG_PROC_FS
 197
 198 int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
 199 {
 200         static unsigned long next = INITIAL_JIFFIES;
 201         struct autogroup *ag;
 202         int err;
 203
 204         if (nice < -20 || nice > 19)
 205                 return -EINVAL;
 206
 207         err = security_task_setnice(current, nice);
 208         if (err)
 209                 return err;
 210
 211         if (nice < 0 && !can_nice(current, nice))
 212                 return -EPERM;
 213
 214         /* this is a heavy operation taking global locks.. */
 215         if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
 216                 return -EAGAIN;
 217
 218         next = HZ / 10 + jiffies;
 219         ag = autogroup_task_get(p);
 220
 221         down_write(&ag->lock);
 222         err = sched_group_set_shares(ag->tg, prio_to_weight[nice + 20]);
 223         if (!err)
 224                 ag->nice = nice;
 225         up_write(&ag->lock);
 226
 227         autogroup_kref_put(ag);
 228
 229         return err;
 230 }
 231
 232 void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
 233 {
 234         struct autogroup *ag = autogroup_task_get(p);
 235
 236         if (!task_group_is_autogroup(ag->tg))
 237                 goto out;
 238
 239         down_read(&ag->lock);
 240         seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
 241         up_read(&ag->lock);
 242
 243 out:
 244         autogroup_kref_put(ag);
 245 }
 246 #endif /* CONFIG_PROC_FS */
 247
 248 #ifdef CONFIG_SCHED_DEBUG
 249 int autogroup_path(struct task_group *tg, char *buf, int buflen)
 250 {
 251         if (!task_group_is_autogroup(tg))
 252                 return 0;
 253
 254         return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
 255 }
 256 #endif /* CONFIG_SCHED_DEBUG */
 257
 258 #endif /* CONFIG_SCHED_AUTOGROUP */