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