| // SPDX-License-Identifier: GPL-2.0 |
| |
| /* |
| * Auto-group scheduling implementation: |
| */ |
| |
| unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1; |
| static struct autogroup autogroup_default; |
| static atomic_t autogroup_seq_nr; |
| |
| #ifdef CONFIG_SYSCTL |
| static struct ctl_table sched_autogroup_sysctls[] = { |
| { |
| .procname = "sched_autogroup_enabled", |
| .data = &sysctl_sched_autogroup_enabled, |
| .maxlen = sizeof(unsigned int), |
| .mode = 0644, |
| .proc_handler = proc_dointvec_minmax, |
| .extra1 = SYSCTL_ZERO, |
| .extra2 = SYSCTL_ONE, |
| }, |
| {} |
| }; |
| |
| static void __init sched_autogroup_sysctl_init(void) |
| { |
| register_sysctl_init("kernel", sched_autogroup_sysctls); |
| } |
| #else |
| #define sched_autogroup_sysctl_init() do { } while (0) |
| #endif |
| |
| void __init autogroup_init(struct task_struct *init_task) |
| { |
| autogroup_default.tg = &root_task_group; |
| kref_init(&autogroup_default.kref); |
| init_rwsem(&autogroup_default.lock); |
| init_task->signal->autogroup = &autogroup_default; |
| sched_autogroup_sysctl_init(); |
| } |
| |
| void autogroup_free(struct task_group *tg) |
| { |
| kfree(tg->autogroup); |
| } |
| |
| static inline void autogroup_destroy(struct kref *kref) |
| { |
| struct autogroup *ag = container_of(kref, struct autogroup, kref); |
| |
| #ifdef CONFIG_RT_GROUP_SCHED |
| /* We've redirected RT tasks to the root task group... */ |
| ag->tg->rt_se = NULL; |
| ag->tg->rt_rq = NULL; |
| #endif |
| sched_release_group(ag->tg); |
| sched_destroy_group(ag->tg); |
| } |
| |
| static inline void autogroup_kref_put(struct autogroup *ag) |
| { |
| kref_put(&ag->kref, autogroup_destroy); |
| } |
| |
| static inline struct autogroup *autogroup_kref_get(struct autogroup *ag) |
| { |
| kref_get(&ag->kref); |
| return ag; |
| } |
| |
| static inline struct autogroup *autogroup_task_get(struct task_struct *p) |
| { |
| struct autogroup *ag; |
| unsigned long flags; |
| |
| if (!lock_task_sighand(p, &flags)) |
| return autogroup_kref_get(&autogroup_default); |
| |
| ag = autogroup_kref_get(p->signal->autogroup); |
| unlock_task_sighand(p, &flags); |
| |
| return ag; |
| } |
| |
| static inline struct autogroup *autogroup_create(void) |
| { |
| struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL); |
| struct task_group *tg; |
| |
| if (!ag) |
| goto out_fail; |
| |
| tg = sched_create_group(&root_task_group); |
| if (IS_ERR(tg)) |
| goto out_free; |
| |
| kref_init(&ag->kref); |
| init_rwsem(&ag->lock); |
| ag->id = atomic_inc_return(&autogroup_seq_nr); |
| ag->tg = tg; |
| #ifdef CONFIG_RT_GROUP_SCHED |
| /* |
| * Autogroup RT tasks are redirected to the root task group |
| * so we don't have to move tasks around upon policy change, |
| * or flail around trying to allocate bandwidth on the fly. |
| * A bandwidth exception in __sched_setscheduler() allows |
| * the policy change to proceed. |
| */ |
| free_rt_sched_group(tg); |
| tg->rt_se = root_task_group.rt_se; |
| tg->rt_rq = root_task_group.rt_rq; |
| #endif |
| tg->autogroup = ag; |
| |
| sched_online_group(tg, &root_task_group); |
| return ag; |
| |
| out_free: |
| kfree(ag); |
| out_fail: |
| if (printk_ratelimit()) { |
| printk(KERN_WARNING "autogroup_create: %s failure.\n", |
| ag ? "sched_create_group()" : "kzalloc()"); |
| } |
| |
| return autogroup_kref_get(&autogroup_default); |
| } |
| |
| bool task_wants_autogroup(struct task_struct *p, struct task_group *tg) |
| { |
| if (tg != &root_task_group) |
| return false; |
| /* |
| * If we race with autogroup_move_group() the caller can use the old |
| * value of signal->autogroup but in this case sched_move_task() will |
| * be called again before autogroup_kref_put(). |
| * |
| * However, there is no way sched_autogroup_exit_task() could tell us |
| * to avoid autogroup->tg, so we abuse PF_EXITING flag for this case. |
| */ |
| if (p->flags & PF_EXITING) |
| return false; |
| |
| return true; |
| } |
| |
| void sched_autogroup_exit_task(struct task_struct *p) |
| { |
| /* |
| * We are going to call exit_notify() and autogroup_move_group() can't |
| * see this thread after that: we can no longer use signal->autogroup. |
| * See the PF_EXITING check in task_wants_autogroup(). |
| */ |
| sched_move_task(p); |
| } |
| |
| static void |
| autogroup_move_group(struct task_struct *p, struct autogroup *ag) |
| { |
| struct autogroup *prev; |
| struct task_struct *t; |
| unsigned long flags; |
| |
| BUG_ON(!lock_task_sighand(p, &flags)); |
| |
| prev = p->signal->autogroup; |
| if (prev == ag) { |
| unlock_task_sighand(p, &flags); |
| return; |
| } |
| |
| p->signal->autogroup = autogroup_kref_get(ag); |
| /* |
| * We can't avoid sched_move_task() after we changed signal->autogroup, |
| * this process can already run with task_group() == prev->tg or we can |
| * race with cgroup code which can read autogroup = prev under rq->lock. |
| * In the latter case for_each_thread() can not miss a migrating thread, |
| * cpu_cgroup_attach() must not be possible after cgroup_exit() and it |
| * can't be removed from thread list, we hold ->siglock. |
| * |
| * If an exiting thread was already removed from thread list we rely on |
| * sched_autogroup_exit_task(). |
| */ |
| for_each_thread(p, t) |
| sched_move_task(t); |
| |
| unlock_task_sighand(p, &flags); |
| autogroup_kref_put(prev); |
| } |
| |
| /* Allocates GFP_KERNEL, cannot be called under any spinlock: */ |
| void sched_autogroup_create_attach(struct task_struct *p) |
| { |
| struct autogroup *ag = autogroup_create(); |
| |
| autogroup_move_group(p, ag); |
| |
| /* Drop extra reference added by autogroup_create(): */ |
| autogroup_kref_put(ag); |
| } |
| EXPORT_SYMBOL(sched_autogroup_create_attach); |
| |
| /* Cannot be called under siglock. Currently has no users: */ |
| void sched_autogroup_detach(struct task_struct *p) |
| { |
| autogroup_move_group(p, &autogroup_default); |
| } |
| EXPORT_SYMBOL(sched_autogroup_detach); |
| |
| void sched_autogroup_fork(struct signal_struct *sig) |
| { |
| sig->autogroup = autogroup_task_get(current); |
| } |
| |
| void sched_autogroup_exit(struct signal_struct *sig) |
| { |
| autogroup_kref_put(sig->autogroup); |
| } |
| |
| static int __init setup_autogroup(char *str) |
| { |
| sysctl_sched_autogroup_enabled = 0; |
| |
| return 1; |
| } |
| __setup("noautogroup", setup_autogroup); |
| |
| #ifdef CONFIG_PROC_FS |
| |
| int proc_sched_autogroup_set_nice(struct task_struct *p, int nice) |
| { |
| static unsigned long next = INITIAL_JIFFIES; |
| struct autogroup *ag; |
| unsigned long shares; |
| int err, idx; |
| |
| if (nice < MIN_NICE || nice > MAX_NICE) |
| return -EINVAL; |
| |
| err = security_task_setnice(current, nice); |
| if (err) |
| return err; |
| |
| if (nice < 0 && !can_nice(current, nice)) |
| return -EPERM; |
| |
| /* This is a heavy operation, taking global locks.. */ |
| if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next)) |
| return -EAGAIN; |
| |
| next = HZ / 10 + jiffies; |
| ag = autogroup_task_get(p); |
| |
| idx = array_index_nospec(nice + 20, 40); |
| shares = scale_load(sched_prio_to_weight[idx]); |
| |
| down_write(&ag->lock); |
| err = sched_group_set_shares(ag->tg, shares); |
| if (!err) |
| ag->nice = nice; |
| up_write(&ag->lock); |
| |
| autogroup_kref_put(ag); |
| |
| return err; |
| } |
| |
| void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m) |
| { |
| struct autogroup *ag = autogroup_task_get(p); |
| |
| if (!task_group_is_autogroup(ag->tg)) |
| goto out; |
| |
| down_read(&ag->lock); |
| seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice); |
| up_read(&ag->lock); |
| |
| out: |
| autogroup_kref_put(ag); |
| } |
| #endif /* CONFIG_PROC_FS */ |
| |
| int autogroup_path(struct task_group *tg, char *buf, int buflen) |
| { |
| if (!task_group_is_autogroup(tg)) |
| return 0; |
| |
| return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id); |
| } |