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         sched_online_group(tg, &root_task_group);
  81
  82         kref_init(&ag->kref);
  83         init_rwsem(&ag->lock);
  84         ag->id = atomic_inc_return(&autogroup_seq_nr);
  85         ag->tg = tg;
  86 #ifdef CONFIG_RT_GROUP_SCHED
  87         /*
  88          * Autogroup RT tasks are redirected to the root task group
  89          * so we don't have to move tasks around upon policy change,
  90          * or flail around trying to allocate bandwidth on the fly.
  91          * A bandwidth exception in __sched_setscheduler() allows
  92          * the policy change to proceed.  Thereafter, task_group()
  93          * returns &root_task_group, so zero bandwidth is required.
  94          */
  95         free_rt_sched_group(tg);
  96         tg->rt_se = root_task_group.rt_se;
  97         tg->rt_rq = root_task_group.rt_rq;
  98 #endif
  99         tg->autogroup = ag;
 100
 101         return ag;
 102
 103 out_free:
 104         kfree(ag);
 105 out_fail:
 106         if (printk_ratelimit()) {
 107                 printk(KERN_WARNING "autogroup_create: %s failure.\n",
 108                         ag ? "sched_create_group()" : "kmalloc()");
 109         }
 110
 111         return autogroup_kref_get(&autogroup_default);
 112 }
 113
 114 bool task_wants_autogroup(struct task_struct *p, struct task_group *tg)
 115 {
 116         if (tg != &root_task_group)
 117                 return false;
 118
 119         if (p->sched_class != &fair_sched_class)
 120                 return false;
 121
 122         /*
 123          * We can only assume the task group can't go away on us if
 124          * autogroup_move_group() can see us on ->thread_group list.
 125          */
 126         if (p->flags & PF_EXITING)
 127                 return false;
 128
 129         return true;
 130 }
 131
 132 static void
 133 autogroup_move_group(struct task_struct *p, struct autogroup *ag)
 134 {
 135         struct autogroup *prev;
 136         struct task_struct *t;
 137         unsigned long flags;
 138
 139         BUG_ON(!lock_task_sighand(p, &flags));
 140
 141         prev = p->signal->autogroup;
 142         if (prev == ag) {
 143                 unlock_task_sighand(p, &flags);
 144                 return;
 145         }
 146
 147         p->signal->autogroup = autogroup_kref_get(ag);
 148
 149         if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
 150                 goto out;
 151
 152         t = p;
 153         do {
 154                 sched_move_task(t);
 155         } while_each_thread(p, t);
 156
 157 out:
 158         unlock_task_sighand(p, &flags);
 159         autogroup_kref_put(prev);
 160 }
 161
 162 /* Allocates GFP_KERNEL, cannot be called under any spinlock */
 163 void sched_autogroup_create_attach(struct task_struct *p)
 164 {
 165         struct autogroup *ag = autogroup_create();
 166
 167         autogroup_move_group(p, ag);
 168         /* drop extra reference added by autogroup_create() */
 169         autogroup_kref_put(ag);
 170 }
 171 EXPORT_SYMBOL(sched_autogroup_create_attach);
 172
 173 /* Cannot be called under siglock.  Currently has no users */
 174 void sched_autogroup_detach(struct task_struct *p)
 175 {
 176         autogroup_move_group(p, &autogroup_default);
 177 }
 178 EXPORT_SYMBOL(sched_autogroup_detach);
 179
 180 void sched_autogroup_fork(struct signal_struct *sig)
 181 {
 182         sig->autogroup = autogroup_task_get(current);
 183 }
 184
 185 void sched_autogroup_exit(struct signal_struct *sig)
 186 {
 187         autogroup_kref_put(sig->autogroup);
 188 }
 189
 190 static int __init setup_autogroup(char *str)
 191 {
 192         sysctl_sched_autogroup_enabled = 0;
 193
 194         return 1;
 195 }
 196
 197 __setup("noautogroup", setup_autogroup);
 198
 199 #ifdef CONFIG_PROC_FS
 200
 201 int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
 202 {
 203         static unsigned long next = INITIAL_JIFFIES;
 204         struct autogroup *ag;
 205         int err;
 206
 207         if (nice < -20 || nice > 19)
 208                 return -EINVAL;
 209
 210         err = security_task_setnice(current, nice);
 211         if (err)
 212                 return err;
 213
 214         if (nice < 0 && !can_nice(current, nice))
 215                 return -EPERM;
 216
 217         /* this is a heavy operation taking global locks.. */
 218         if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
 219                 return -EAGAIN;
 220
 221         next = HZ / 10 + jiffies;
 222         ag = autogroup_task_get(p);
 223
 224         down_write(&ag->lock);
 225         err = sched_group_set_shares(ag->tg, prio_to_weight[nice + 20]);
 226         if (!err)
 227                 ag->nice = nice;
 228         up_write(&ag->lock);
 229
 230         autogroup_kref_put(ag);
 231
 232         return err;
 233 }
 234
 235 void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
 236 {
 237         struct autogroup *ag = autogroup_task_get(p);
 238
 239         if (!task_group_is_autogroup(ag->tg))
 240                 goto out;
 241
 242         down_read(&ag->lock);
 243         seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
 244         up_read(&ag->lock);
 245
 246 out:
 247         autogroup_kref_put(ag);
 248 }
 249 #endif /* CONFIG_PROC_FS */
 250
 251 #ifdef CONFIG_SCHED_DEBUG
 252 int autogroup_path(struct task_group *tg, char *buf, int buflen)
 253 {
 254         if (!task_group_is_autogroup(tg))
 255                 return 0;
 256
 257         return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
 258 }
 259 #endif /* CONFIG_SCHED_DEBUG */
 260
 261 #endif /* CONFIG_SCHED_AUTOGROUP */