linux/kernel/sched/auto_group.c
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   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
  12unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1;
  13static struct autogroup autogroup_default;
  14static atomic_t autogroup_seq_nr;
  15
  16void __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
  24void autogroup_free(struct task_group *tg)
  25{
  26        kfree(tg->autogroup);
  27}
  28
  29static 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
  41static inline void autogroup_kref_put(struct autogroup *ag)
  42{
  43        kref_put(&ag->kref, autogroup_destroy);
  44}
  45
  46static inline struct autogroup *autogroup_kref_get(struct autogroup *ag)
  47{
  48        kref_get(&ag->kref);
  49        return ag;
  50}
  51
  52static 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
  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
 111bool 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
 129static void
 130autogroup_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
 154out:
 155        unlock_task_sighand(p, &flags);
 156        autogroup_kref_put(prev);
 157}
 158
 159/* Allocates GFP_KERNEL, cannot be called under any spinlock */
 160void 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}
 168EXPORT_SYMBOL(sched_autogroup_create_attach);
 169
 170/* Cannot be called under siglock.  Currently has no users */
 171void sched_autogroup_detach(struct task_struct *p)
 172{
 173        autogroup_move_group(p, &autogroup_default);
 174}
 175EXPORT_SYMBOL(sched_autogroup_detach);
 176
 177void sched_autogroup_fork(struct signal_struct *sig)
 178{
 179        sig->autogroup = autogroup_task_get(current);
 180}
 181
 182void sched_autogroup_exit(struct signal_struct *sig)
 183{
 184        autogroup_kref_put(sig->autogroup);
 185}
 186
 187static 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
 198int 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
 232void 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
 243out:
 244        autogroup_kref_put(ag);
 245}
 246#endif /* CONFIG_PROC_FS */
 247
 248#ifdef CONFIG_SCHED_DEBUG
 249int 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 */
 259
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