1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Auto-group scheduling implementation: 4 */ 5 #include "sched.h" 6 7 unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1; 8 static struct autogroup autogroup_default; 9 static atomic_t autogroup_seq_nr; 10 11 void __init autogroup_init(struct task_struct *init_task) 12 { 13 autogroup_default.tg = &root_task_group; 14 kref_init(&autogroup_default.kref); 15 init_rwsem(&autogroup_default.lock); 16 init_task->signal->autogroup = &autogroup_default; 17 } 18 19 void autogroup_free(struct task_group *tg) 20 { 21 kfree(tg->autogroup); 22 } 23 24 static inline void autogroup_destroy(struct kref *kref) 25 { 26 struct autogroup *ag = container_of(kref, struct autogroup, kref); 27 28 #ifdef CONFIG_RT_GROUP_SCHED 29 /* We've redirected RT tasks to the root task group... */ 30 ag->tg->rt_se = NULL; 31 ag->tg->rt_rq = NULL; 32 #endif 33 sched_offline_group(ag->tg); 34 sched_destroy_group(ag->tg); 35 } 36 37 static inline void autogroup_kref_put(struct autogroup *ag) 38 { 39 kref_put(&ag->kref, autogroup_destroy); 40 } 41 42 static inline struct autogroup *autogroup_kref_get(struct autogroup *ag) 43 { 44 kref_get(&ag->kref); 45 return ag; 46 } 47 48 static 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 static inline struct autogroup *autogroup_create(void) 63 { 64 struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL); 65 struct task_group *tg; 66 67 if (!ag) 68 goto out_fail; 69 70 tg = sched_create_group(&root_task_group); 71 if (IS_ERR(tg)) 72 goto out_free; 73 74 kref_init(&ag->kref); 75 init_rwsem(&ag->lock); 76 ag->id = atomic_inc_return(&autogroup_seq_nr); 77 ag->tg = tg; 78 #ifdef CONFIG_RT_GROUP_SCHED 79 /* 80 * Autogroup RT tasks are redirected to the root task group 81 * so we don't have to move tasks around upon policy change, 82 * or flail around trying to allocate bandwidth on the fly. 83 * A bandwidth exception in __sched_setscheduler() allows 84 * the policy change to proceed. 85 */ 86 free_rt_sched_group(tg); 87 tg->rt_se = root_task_group.rt_se; 88 tg->rt_rq = root_task_group.rt_rq; 89 #endif 90 tg->autogroup = ag; 91 92 sched_online_group(tg, &root_task_group); 93 return ag; 94 95 out_free: 96 kfree(ag); 97 out_fail: 98 if (printk_ratelimit()) { 99 printk(KERN_WARNING "autogroup_create: %s failure.\n", 100 ag ? "sched_create_group()" : "kzalloc()"); 101 } 102 103 return autogroup_kref_get(&autogroup_default); 104 } 105 106 bool task_wants_autogroup(struct task_struct *p, struct task_group *tg) 107 { 108 if (tg != &root_task_group) 109 return false; 110 /* 111 * If we race with autogroup_move_group() the caller can use the old 112 * value of signal->autogroup but in this case sched_move_task() will 113 * be called again before autogroup_kref_put(). 114 * 115 * However, there is no way sched_autogroup_exit_task() could tell us 116 * to avoid autogroup->tg, so we abuse PF_EXITING flag for this case. 117 */ 118 if (p->flags & PF_EXITING) 119 return false; 120 121 return true; 122 } 123 124 void sched_autogroup_exit_task(struct task_struct *p) 125 { 126 /* 127 * We are going to call exit_notify() and autogroup_move_group() can't 128 * see this thread after that: we can no longer use signal->autogroup. 129 * See the PF_EXITING check in task_wants_autogroup(). 130 */ 131 sched_move_task(p); 132 } 133 134 static void 135 autogroup_move_group(struct task_struct *p, struct autogroup *ag) 136 { 137 struct autogroup *prev; 138 struct task_struct *t; 139 unsigned long flags; 140 141 BUG_ON(!lock_task_sighand(p, &flags)); 142 143 prev = p->signal->autogroup; 144 if (prev == ag) { 145 unlock_task_sighand(p, &flags); 146 return; 147 } 148 149 p->signal->autogroup = autogroup_kref_get(ag); 150 /* 151 * We can't avoid sched_move_task() after we changed signal->autogroup, 152 * this process can already run with task_group() == prev->tg or we can 153 * race with cgroup code which can read autogroup = prev under rq->lock. 154 * In the latter case for_each_thread() can not miss a migrating thread, 155 * cpu_cgroup_attach() must not be possible after cgroup_exit() and it 156 * can't be removed from thread list, we hold ->siglock. 157 * 158 * If an exiting thread was already removed from thread list we rely on 159 * sched_autogroup_exit_task(). 160 */ 161 for_each_thread(p, t) 162 sched_move_task(t); 163 164 unlock_task_sighand(p, &flags); 165 autogroup_kref_put(prev); 166 } 167 168 /* Allocates GFP_KERNEL, cannot be called under any spinlock: */ 169 void sched_autogroup_create_attach(struct task_struct *p) 170 { 171 struct autogroup *ag = autogroup_create(); 172 173 autogroup_move_group(p, ag); 174 175 /* Drop extra reference added by autogroup_create(): */ 176 autogroup_kref_put(ag); 177 } 178 EXPORT_SYMBOL(sched_autogroup_create_attach); 179 180 /* Cannot be called under siglock. Currently has no users: */ 181 void sched_autogroup_detach(struct task_struct *p) 182 { 183 autogroup_move_group(p, &autogroup_default); 184 } 185 EXPORT_SYMBOL(sched_autogroup_detach); 186 187 void sched_autogroup_fork(struct signal_struct *sig) 188 { 189 sig->autogroup = autogroup_task_get(current); 190 } 191 192 void sched_autogroup_exit(struct signal_struct *sig) 193 { 194 autogroup_kref_put(sig->autogroup); 195 } 196 197 static int __init setup_autogroup(char *str) 198 { 199 sysctl_sched_autogroup_enabled = 0; 200 201 return 1; 202 } 203 __setup("noautogroup", setup_autogroup); 204 205 #ifdef CONFIG_PROC_FS 206 207 int proc_sched_autogroup_set_nice(struct task_struct *p, int nice) 208 { 209 static unsigned long next = INITIAL_JIFFIES; 210 struct autogroup *ag; 211 unsigned long shares; 212 int err; 213 214 if (nice < MIN_NICE || nice > MAX_NICE) 215 return -EINVAL; 216 217 err = security_task_setnice(current, nice); 218 if (err) 219 return err; 220 221 if (nice < 0 && !can_nice(current, nice)) 222 return -EPERM; 223 224 /* This is a heavy operation, taking global locks.. */ 225 if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next)) 226 return -EAGAIN; 227 228 next = HZ / 10 + jiffies; 229 ag = autogroup_task_get(p); 230 shares = scale_load(sched_prio_to_weight[nice + 20]); 231 232 down_write(&ag->lock); 233 err = sched_group_set_shares(ag->tg, shares); 234 if (!err) 235 ag->nice = nice; 236 up_write(&ag->lock); 237 238 autogroup_kref_put(ag); 239 240 return err; 241 } 242 243 void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m) 244 { 245 struct autogroup *ag = autogroup_task_get(p); 246 247 if (!task_group_is_autogroup(ag->tg)) 248 goto out; 249 250 down_read(&ag->lock); 251 seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice); 252 up_read(&ag->lock); 253 254 out: 255 autogroup_kref_put(ag); 256 } 257 #endif /* CONFIG_PROC_FS */ 258 259 #ifdef CONFIG_SCHED_DEBUG 260 int autogroup_path(struct task_group *tg, char *buf, int buflen) 261 { 262 if (!task_group_is_autogroup(tg)) 263 return 0; 264 265 return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id); 266 } 267 #endif 268