linux/kernel/sched_autogroup.c
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   1#ifdef CONFIG_SCHED_AUTOGROUP
   2
   3#include <linux/proc_fs.h>
   4#include <linux/seq_file.h>
   5#include <linux/kallsyms.h>
   6#include <linux/utsname.h>
   7
   8unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
   9static struct autogroup autogroup_default;
  10static atomic_t autogroup_seq_nr;
  11
  12static void __init autogroup_init(struct task_struct *init_task)
  13{
  14        autogroup_default.tg = &root_task_group;
  15        kref_init(&autogroup_default.kref);
  16        init_rwsem(&autogroup_default.lock);
  17        init_task->signal->autogroup = &autogroup_default;
  18}
  19
  20static inline void autogroup_free(struct task_group *tg)
  21{
  22        kfree(tg->autogroup);
  23}
  24
  25static inline void autogroup_destroy(struct kref *kref)
  26{
  27        struct autogroup *ag = container_of(kref, struct autogroup, kref);
  28
  29#ifdef CONFIG_RT_GROUP_SCHED
  30        /* We've redirected RT tasks to the root task group... */
  31        ag->tg->rt_se = NULL;
  32        ag->tg->rt_rq = NULL;
  33#endif
  34        sched_destroy_group(ag->tg);
  35}
  36
  37static inline void autogroup_kref_put(struct autogroup *ag)
  38{
  39        kref_put(&ag->kref, autogroup_destroy);
  40}
  41
  42static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
  43{
  44        kref_get(&ag->kref);
  45        return ag;
  46}
  47
  48static inline struct autogroup *autogroup_task_get(struct task_struct *p)
  49{
  50        struct autogroup *ag;
  51        unsigned long flags;
  52
  53        if (!lock_task_sighand(p, &flags))
  54                return autogroup_kref_get(&autogroup_default);
  55
  56        ag = autogroup_kref_get(p->signal->autogroup);
  57        unlock_task_sighand(p, &flags);
  58
  59        return ag;
  60}
  61
  62#ifdef CONFIG_RT_GROUP_SCHED
  63static void free_rt_sched_group(struct task_group *tg);
  64#endif
  65
  66static 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
 100out_free:
 101        kfree(ag);
 102out_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
 111static inline bool
 112task_wants_autogroup(struct task_struct *p, struct task_group *tg)
 113{
 114        if (tg != &root_task_group)
 115                return false;
 116
 117        if (p->sched_class != &fair_sched_class)
 118                return false;
 119
 120        /*
 121         * We can only assume the task group can't go away on us if
 122         * autogroup_move_group() can see us on ->thread_group list.
 123         */
 124        if (p->flags & PF_EXITING)
 125                return false;
 126
 127        return true;
 128}
 129
 130static inline bool task_group_is_autogroup(struct task_group *tg)
 131{
 132        return !!tg->autogroup;
 133}
 134
 135static inline struct task_group *
 136autogroup_task_group(struct task_struct *p, struct task_group *tg)
 137{
 138        int enabled = ACCESS_ONCE(sysctl_sched_autogroup_enabled);
 139
 140        if (enabled && task_wants_autogroup(p, tg))
 141                return p->signal->autogroup->tg;
 142
 143        return tg;
 144}
 145
 146static void
 147autogroup_move_group(struct task_struct *p, struct autogroup *ag)
 148{
 149        struct autogroup *prev;
 150        struct task_struct *t;
 151        unsigned long flags;
 152
 153        BUG_ON(!lock_task_sighand(p, &flags));
 154
 155        prev = p->signal->autogroup;
 156        if (prev == ag) {
 157                unlock_task_sighand(p, &flags);
 158                return;
 159        }
 160
 161        p->signal->autogroup = autogroup_kref_get(ag);
 162
 163        if (!ACCESS_ONCE(sysctl_sched_autogroup_enabled))
 164                goto out;
 165
 166        t = p;
 167        do {
 168                sched_move_task(t);
 169        } while_each_thread(p, t);
 170
 171out:
 172        unlock_task_sighand(p, &flags);
 173        autogroup_kref_put(prev);
 174}
 175
 176/* Allocates GFP_KERNEL, cannot be called under any spinlock */
 177void sched_autogroup_create_attach(struct task_struct *p)
 178{
 179        struct autogroup *ag = autogroup_create();
 180
 181        autogroup_move_group(p, ag);
 182        /* drop extra reference added by autogroup_create() */
 183        autogroup_kref_put(ag);
 184}
 185EXPORT_SYMBOL(sched_autogroup_create_attach);
 186
 187/* Cannot be called under siglock.  Currently has no users */
 188void sched_autogroup_detach(struct task_struct *p)
 189{
 190        autogroup_move_group(p, &autogroup_default);
 191}
 192EXPORT_SYMBOL(sched_autogroup_detach);
 193
 194void sched_autogroup_fork(struct signal_struct *sig)
 195{
 196        sig->autogroup = autogroup_task_get(current);
 197}
 198
 199void sched_autogroup_exit(struct signal_struct *sig)
 200{
 201        autogroup_kref_put(sig->autogroup);
 202}
 203
 204static int __init setup_autogroup(char *str)
 205{
 206        sysctl_sched_autogroup_enabled = 0;
 207
 208        return 1;
 209}
 210
 211__setup("noautogroup", setup_autogroup);
 212
 213#ifdef CONFIG_PROC_FS
 214
 215int proc_sched_autogroup_set_nice(struct task_struct *p, int *nice)
 216{
 217        static unsigned long next = INITIAL_JIFFIES;
 218        struct autogroup *ag;
 219        int err;
 220
 221        if (*nice < -20 || *nice > 19)
 222                return -EINVAL;
 223
 224        err = security_task_setnice(current, *nice);
 225        if (err)
 226                return err;
 227
 228        if (*nice < 0 && !can_nice(current, *nice))
 229                return -EPERM;
 230
 231        /* this is a heavy operation taking global locks.. */
 232        if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next))
 233                return -EAGAIN;
 234
 235        next = HZ / 10 + jiffies;
 236        ag = autogroup_task_get(p);
 237
 238        down_write(&ag->lock);
 239        err = sched_group_set_shares(ag->tg, prio_to_weight[*nice + 20]);
 240        if (!err)
 241                ag->nice = *nice;
 242        up_write(&ag->lock);
 243
 244        autogroup_kref_put(ag);
 245
 246        return err;
 247}
 248
 249void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m)
 250{
 251        struct autogroup *ag = autogroup_task_get(p);
 252
 253        if (!task_group_is_autogroup(ag->tg))
 254                goto out;
 255
 256        down_read(&ag->lock);
 257        seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice);
 258        up_read(&ag->lock);
 259
 260out:
 261        autogroup_kref_put(ag);
 262}
 263#endif /* CONFIG_PROC_FS */
 264
 265#ifdef CONFIG_SCHED_DEBUG
 266static inline int autogroup_path(struct task_group *tg, char *buf, int buflen)
 267{
 268        if (!task_group_is_autogroup(tg))
 269                return 0;
 270
 271        return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id);
 272}
 273#endif /* CONFIG_SCHED_DEBUG */
 274
 275#endif /* CONFIG_SCHED_AUTOGROUP */
 276
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