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