1 #include "sched.h" 2 3 #include <linux/proc_fs.h> 4 #include <linux/seq_file.h> 5 #include <linux/kallsyms.h> 6 #include <linux/utsname.h> 7 #include <linux/security.h> 8 #include <linux/export.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 75 if (IS_ERR(tg)) 76 goto out_free; 77 78 kref_init(&ag->kref); 79 init_rwsem(&ag->lock); 80 ag->id = atomic_inc_return(&autogroup_seq_nr); 81 ag->tg = tg; 82 #ifdef CONFIG_RT_GROUP_SCHED 83 /* 84 * Autogroup RT tasks are redirected to the root task group 85 * so we don't have to move tasks around upon policy change, 86 * or flail around trying to allocate bandwidth on the fly. 87 * A bandwidth exception in __sched_setscheduler() allows 88 * the policy change to proceed. 89 */ 90 free_rt_sched_group(tg); 91 tg->rt_se = root_task_group.rt_se; 92 tg->rt_rq = root_task_group.rt_rq; 93 #endif 94 tg->autogroup = ag; 95 96 sched_online_group(tg, &root_task_group); 97 return ag; 98 99 out_free: 100 kfree(ag); 101 out_fail: 102 if (printk_ratelimit()) { 103 printk(KERN_WARNING "autogroup_create: %s failure.\n", 104 ag ? "sched_create_group()" : "kmalloc()"); 105 } 106 107 return autogroup_kref_get(&autogroup_default); 108 } 109 110 bool task_wants_autogroup(struct task_struct *p, struct task_group *tg) 111 { 112 if (tg != &root_task_group) 113 return false; 114 /* 115 * If we race with autogroup_move_group() the caller can use the old 116 * value of signal->autogroup but in this case sched_move_task() will 117 * be called again before autogroup_kref_put(). 118 * 119 * However, there is no way sched_autogroup_exit_task() could tell us 120 * to avoid autogroup->tg, so we abuse PF_EXITING flag for this case. 121 */ 122 if (p->flags & PF_EXITING) 123 return false; 124 125 return true; 126 } 127 128 void sched_autogroup_exit_task(struct task_struct *p) 129 { 130 /* 131 * We are going to call exit_notify() and autogroup_move_group() can't 132 * see this thread after that: we can no longer use signal->autogroup. 133 * See the PF_EXITING check in task_wants_autogroup(). 134 */ 135 sched_move_task(p); 136 } 137 138 static void 139 autogroup_move_group(struct task_struct *p, struct autogroup *ag) 140 { 141 struct autogroup *prev; 142 struct task_struct *t; 143 unsigned long flags; 144 145 BUG_ON(!lock_task_sighand(p, &flags)); 146 147 prev = p->signal->autogroup; 148 if (prev == ag) { 149 unlock_task_sighand(p, &flags); 150 return; 151 } 152 153 p->signal->autogroup = autogroup_kref_get(ag); 154 /* 155 * We can't avoid sched_move_task() after we changed signal->autogroup, 156 * this process can already run with task_group() == prev->tg or we can 157 * race with cgroup code which can read autogroup = prev under rq->lock. 158 * In the latter case for_each_thread() can not miss a migrating thread, 159 * cpu_cgroup_attach() must not be possible after cgroup_exit() and it 160 * can't be removed from thread list, we hold ->siglock. 161 * 162 * If an exiting thread was already removed from thread list we rely on 163 * sched_autogroup_exit_task(). 164 */ 165 for_each_thread(p, t) 166 sched_move_task(t); 167 168 unlock_task_sighand(p, &flags); 169 autogroup_kref_put(prev); 170 } 171 172 /* Allocates GFP_KERNEL, cannot be called under any spinlock */ 173 void sched_autogroup_create_attach(struct task_struct *p) 174 { 175 struct autogroup *ag = autogroup_create(); 176 177 autogroup_move_group(p, ag); 178 /* drop extra reference added by autogroup_create() */ 179 autogroup_kref_put(ag); 180 } 181 EXPORT_SYMBOL(sched_autogroup_create_attach); 182 183 /* Cannot be called under siglock. Currently has no users */ 184 void sched_autogroup_detach(struct task_struct *p) 185 { 186 autogroup_move_group(p, &autogroup_default); 187 } 188 EXPORT_SYMBOL(sched_autogroup_detach); 189 190 void sched_autogroup_fork(struct signal_struct *sig) 191 { 192 sig->autogroup = autogroup_task_get(current); 193 } 194 195 void sched_autogroup_exit(struct signal_struct *sig) 196 { 197 autogroup_kref_put(sig->autogroup); 198 } 199 200 static int __init setup_autogroup(char *str) 201 { 202 sysctl_sched_autogroup_enabled = 0; 203 204 return 1; 205 } 206 207 __setup("noautogroup", setup_autogroup); 208 209 #ifdef CONFIG_PROC_FS 210 211 int proc_sched_autogroup_set_nice(struct task_struct *p, int nice) 212 { 213 static unsigned long next = INITIAL_JIFFIES; 214 struct autogroup *ag; 215 unsigned long shares; 216 int err; 217 218 if (nice < MIN_NICE || nice > MAX_NICE) 219 return -EINVAL; 220 221 err = security_task_setnice(current, nice); 222 if (err) 223 return err; 224 225 if (nice < 0 && !can_nice(current, nice)) 226 return -EPERM; 227 228 /* this is a heavy operation taking global locks.. */ 229 if (!capable(CAP_SYS_ADMIN) && time_before(jiffies, next)) 230 return -EAGAIN; 231 232 next = HZ / 10 + jiffies; 233 ag = autogroup_task_get(p); 234 shares = scale_load(sched_prio_to_weight[nice + 20]); 235 236 down_write(&ag->lock); 237 err = sched_group_set_shares(ag->tg, shares); 238 if (!err) 239 ag->nice = nice; 240 up_write(&ag->lock); 241 242 autogroup_kref_put(ag); 243 244 return err; 245 } 246 247 void proc_sched_autogroup_show_task(struct task_struct *p, struct seq_file *m) 248 { 249 struct autogroup *ag = autogroup_task_get(p); 250 251 if (!task_group_is_autogroup(ag->tg)) 252 goto out; 253 254 down_read(&ag->lock); 255 seq_printf(m, "/autogroup-%ld nice %d\n", ag->id, ag->nice); 256 up_read(&ag->lock); 257 258 out: 259 autogroup_kref_put(ag); 260 } 261 #endif /* CONFIG_PROC_FS */ 262 263 #ifdef CONFIG_SCHED_DEBUG 264 int autogroup_path(struct task_group *tg, char *buf, int buflen) 265 { 266 if (!task_group_is_autogroup(tg)) 267 return 0; 268 269 return snprintf(buf, buflen, "%s-%ld", "/autogroup", tg->autogroup->id); 270 } 271 #endif /* CONFIG_SCHED_DEBUG */ 272