1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/proc_fs.h> 3 #include <linux/seq_file.h> 4 #include <linux/utsname.h> 5 #include <linux/security.h> 6 #include <linux/export.h> 7 8 #include "sched.h" 9 10 unsigned int __read_mostly sysctl_sched_autogroup_enabled = 1; 11 static struct autogroup autogroup_default; 12 static atomic_t autogroup_seq_nr; 13 14 void __init autogroup_init(struct task_struct *init_task) 15 { 16 autogroup_default.tg = &root_task_group; 17 kref_init(&autogroup_default.kref); 18 init_rwsem(&autogroup_default.lock); 19 init_task->signal->autogroup = &autogroup_default; 20 } 21 22 void autogroup_free(struct task_group *tg) 23 { 24 kfree(tg->autogroup); 25 } 26 27 static inline void autogroup_destroy(struct kref *kref) 28 { 29 struct autogroup *ag = container_of(kref, struct autogroup, kref); 30 31 #ifdef CONFIG_RT_GROUP_SCHED 32 /* We've redirected RT tasks to the root task group... */ 33 ag->tg->rt_se = NULL; 34 ag->tg->rt_rq = NULL; 35 #endif 36 sched_offline_group(ag->tg); 37 sched_destroy_group(ag->tg); 38 } 39 40 static inline void autogroup_kref_put(struct autogroup *ag) 41 { 42 kref_put(&ag->kref, autogroup_destroy); 43 } 44 45 static inline struct autogroup *autogroup_kref_get(struct autogroup *ag) 46 { 47 kref_get(&ag->kref); 48 return ag; 49 } 50 51 static inline struct autogroup *autogroup_task_get(struct task_struct *p) 52 { 53 struct autogroup *ag; 54 unsigned long flags; 55 56 if (!lock_task_sighand(p, &flags)) 57 return autogroup_kref_get(&autogroup_default); 58 59 ag = autogroup_kref_get(p->signal->autogroup); 60 unlock_task_sighand(p, &flags); 61 62 return ag; 63 } 64 65 static inline struct autogroup *autogroup_create(void) 66 { 67 struct autogroup *ag = kzalloc(sizeof(*ag), GFP_KERNEL); 68 struct task_group *tg; 69 70 if (!ag) 71 goto out_fail; 72 73 tg = sched_create_group(&root_task_group); 74 if (IS_ERR(tg)) 75 goto out_free; 76 77 kref_init(&ag->kref); 78 init_rwsem(&ag->lock); 79 ag->id = atomic_inc_return(&autogroup_seq_nr); 80 ag->tg = tg; 81 #ifdef CONFIG_RT_GROUP_SCHED 82 /* 83 * Autogroup RT tasks are redirected to the root task group 84 * so we don't have to move tasks around upon policy change, 85 * or flail around trying to allocate bandwidth on the fly. 86 * A bandwidth exception in __sched_setscheduler() allows 87 * the policy change to proceed. 88 */ 89 free_rt_sched_group(tg); 90 tg->rt_se = root_task_group.rt_se; 91 tg->rt_rq = root_task_group.rt_rq; 92 #endif 93 tg->autogroup = ag; 94 95 sched_online_group(tg, &root_task_group); 96 return ag; 97 98 out_free: 99 kfree(ag); 100 out_fail: 101 if (printk_ratelimit()) { 102 printk(KERN_WARNING "autogroup_create: %s failure.\n", 103 ag ? "sched_create_group()" : "kzalloc()"); 104 } 105 106 return autogroup_kref_get(&autogroup_default); 107 } 108 109 bool task_wants_autogroup(struct task_struct *p, struct task_group *tg) 110 { 111 if (tg != &root_task_group) 112 return false; 113 /* 114 * If we race with autogroup_move_group() the caller can use the old 115 * value of signal->autogroup but in this case sched_move_task() will 116 * be called again before autogroup_kref_put(). 117 * 118 * However, there is no way sched_autogroup_exit_task() could tell us 119 * to avoid autogroup->tg, so we abuse PF_EXITING flag for this case. 120 */ 121 if (p->flags & PF_EXITING) 122 return false; 123 124 return true; 125 } 126 127 void sched_autogroup_exit_task(struct task_struct *p) 128 { 129 /* 130 * We are going to call exit_notify() and autogroup_move_group() can't 131 * see this thread after that: we can no longer use signal->autogroup. 132 * See the PF_EXITING check in task_wants_autogroup(). 133 */ 134 sched_move_task(p); 135 } 136 137 static void 138 autogroup_move_group(struct task_struct *p, struct autogroup *ag) 139 { 140 struct autogroup *prev; 141 struct task_struct *t; 142 unsigned long flags; 143 144 BUG_ON(!lock_task_sighand(p, &flags)); 145 146 prev = p->signal->autogroup; 147 if (prev == ag) { 148 unlock_task_sighand(p, &flags); 149 return; 150 } 151 152 p->signal->autogroup = autogroup_kref_get(ag); 153 /* 154 * We can't avoid sched_move_task() after we changed signal->autogroup, 155 * this process can already run with task_group() == prev->tg or we can 156 * race with cgroup code which can read autogroup = prev under rq->lock. 157 * In the latter case for_each_thread() can not miss a migrating thread, 158 * cpu_cgroup_attach() must not be possible after cgroup_exit() and it 159 * can't be removed from thread list, we hold ->siglock. 160 * 161 * If an exiting thread was already removed from thread list we rely on 162 * sched_autogroup_exit_task(). 163 */ 164 for_each_thread(p, t) 165 sched_move_task(t); 166 167 unlock_task_sighand(p, &flags); 168 autogroup_kref_put(prev); 169 } 170 171 /* Allocates GFP_KERNEL, cannot be called under any spinlock */ 172 void sched_autogroup_create_attach(struct task_struct *p) 173 { 174 struct autogroup *ag = autogroup_create(); 175 176 autogroup_move_group(p, ag); 177 /* drop extra reference added by autogroup_create() */ 178 autogroup_kref_put(ag); 179 } 180 EXPORT_SYMBOL(sched_autogroup_create_attach); 181 182 /* Cannot be called under siglock. Currently has no users */ 183 void sched_autogroup_detach(struct task_struct *p) 184 { 185 autogroup_move_group(p, &autogroup_default); 186 } 187 EXPORT_SYMBOL(sched_autogroup_detach); 188 189 void sched_autogroup_fork(struct signal_struct *sig) 190 { 191 sig->autogroup = autogroup_task_get(current); 192 } 193 194 void sched_autogroup_exit(struct signal_struct *sig) 195 { 196 autogroup_kref_put(sig->autogroup); 197 } 198 199 static int __init setup_autogroup(char *str) 200 { 201 sysctl_sched_autogroup_enabled = 0; 202 203 return 1; 204 } 205 206 __setup("noautogroup", setup_autogroup); 207 208 #ifdef CONFIG_PROC_FS 209 210 int proc_sched_autogroup_set_nice(struct task_struct *p, int nice) 211 { 212 static unsigned long next = INITIAL_JIFFIES; 213 struct autogroup *ag; 214 unsigned long shares; 215 int err; 216 217 if (nice < MIN_NICE || nice > MAX_NICE) 218 return -EINVAL; 219 220 err = security_task_setnice(current, nice); 221 if (err) 222 return err; 223 224 if (nice < 0 && !can_nice(current, nice)) 225 return -EPERM; 226 227 /* this is a heavy operation taking global locks.. */ 228 if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next)) 229 return -EAGAIN; 230 231 next = HZ / 10 + jiffies; 232 ag = autogroup_task_get(p); 233 shares = scale_load(sched_prio_to_weight[nice + 20]); 234 235 down_write(&ag->lock); 236 err = sched_group_set_shares(ag->tg, shares); 237 if (!err) 238 ag->nice = nice; 239 up_write(&ag->lock); 240 241 autogroup_kref_put(ag); 242 243 return err; 244 } 245 246 void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m) 247 { 248 struct autogroup *ag = autogroup_task_get(p); 249 250 if (!task_group_is_autogroup(ag->tg)) 251 goto out; 252 253 down_read(&ag->lock); 254 seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice); 255 up_read(&ag->lock); 256 257 out: 258 autogroup_kref_put(ag); 259 } 260 #endif /* CONFIG_PROC_FS */ 261 262 #ifdef CONFIG_SCHED_DEBUG 263 int autogroup_path(struct task_group *tg, char *buf, int buflen) 264 { 265 if (!task_group_is_autogroup(tg)) 266 return 0; 267 268 return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id); 269 } 270 #endif /* CONFIG_SCHED_DEBUG */ 271