kernel/taskstats.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * taskstats.c - Export per-task statistics to userland
   4  *
   5  * Copyright (C) Shailabh Nagar, IBM Corp. 2006
   6  *           (C) Balbir Singh,   IBM Corp. 2006
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/taskstats_kern.h>
  11 #include <linux/tsacct_kern.h>
  12 #include <linux/acct.h>
  13 #include <linux/delayacct.h>
  14 #include <linux/cpumask.h>
  15 #include <linux/percpu.h>
  16 #include <linux/slab.h>
  17 #include <linux/cgroupstats.h>
  18 #include <linux/cgroup.h>
  19 #include <linux/fs.h>
  20 #include <linux/file.h>
  21 #include <linux/pid_namespace.h>
  22 #include <net/genetlink.h>
  23 #include <linux/atomic.h>
  24 #include <linux/sched/cputime.h>
  25
  26 /*
  27  * Maximum length of a cpumask that can be specified in
  28  * the TASKSTATS_CMD_ATTR_REGISTER/DEREGISTER_CPUMASK attribute
  29  */
  30 #define TASKSTATS_CPUMASK_MAXLEN        (100+6*NR_CPUS)
  31
  32 static DEFINE_PER_CPU(__u32, taskstats_seqnum);
  33 static int family_registered;
  34 struct kmem_cache *taskstats_cache;
  35
  36 static struct genl_family family;
  37
  38 static const struct nla_policy taskstats_cmd_get_policy[] = {
  39         [TASKSTATS_CMD_ATTR_PID]  = { .type = NLA_U32 },
  40         [TASKSTATS_CMD_ATTR_TGID] = { .type = NLA_U32 },
  41         [TASKSTATS_CMD_ATTR_REGISTER_CPUMASK] = { .type = NLA_STRING },
  42         [TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK] = { .type = NLA_STRING },};
  43
  44 static const struct nla_policy cgroupstats_cmd_get_policy[] = {
  45         [CGROUPSTATS_CMD_ATTR_FD] = { .type = NLA_U32 },
  46 };
  47
  48 struct listener {
  49         struct list_head list;
  50         pid_t pid;
  51         char valid;
  52 };
  53
  54 struct listener_list {
  55         struct rw_semaphore sem;
  56         struct list_head list;
  57 };
  58 static DEFINE_PER_CPU(struct listener_list, listener_array);
  59
  60 enum actions {
  61         REGISTER,
  62         DEREGISTER,
  63         CPU_DONT_CARE
  64 };
  65
  66 static int prepare_reply(struct genl_info *info, u8 cmd, struct sk_buff **skbp,
  67                                 size_t size)
  68 {
  69         struct sk_buff *skb;
  70         void *reply;
  71
  72         /*
  73          * If new attributes are added, please revisit this allocation
  74          */
  75         skb = genlmsg_new(size, GFP_KERNEL);
  76         if (!skb)
  77                 return -ENOMEM;
  78
  79         if (!info) {
  80                 int seq = this_cpu_inc_return(taskstats_seqnum) - 1;
  81
  82                 reply = genlmsg_put(skb, 0, seq, &family, 0, cmd);
  83         } else
  84                 reply = genlmsg_put_reply(skb, info, &family, 0, cmd);
  85         if (reply == NULL) {
  86                 nlmsg_free(skb);
  87                 return -EINVAL;
  88         }
  89
  90         *skbp = skb;
  91         return 0;
  92 }
  93
  94 /*
  95  * Send taskstats data in @skb to listener with nl_pid @pid
  96  */
  97 static int send_reply(struct sk_buff *skb, struct genl_info *info)
  98 {
  99         struct genlmsghdr *genlhdr = nlmsg_data(nlmsg_hdr(skb));
 100         void *reply = genlmsg_data(genlhdr);
 101
 102         genlmsg_end(skb, reply);
 103
 104         return genlmsg_reply(skb, info);
 105 }
 106
 107 /*
 108  * Send taskstats data in @skb to listeners registered for @cpu's exit data
 109  */
 110 static void send_cpu_listeners(struct sk_buff *skb,
 111                                         struct listener_list *listeners)
 112 {
 113         struct genlmsghdr *genlhdr = nlmsg_data(nlmsg_hdr(skb));
 114         struct listener *s, *tmp;
 115         struct sk_buff *skb_next, *skb_cur = skb;
 116         void *reply = genlmsg_data(genlhdr);
 117         int delcount = 0;
 118
 119         genlmsg_end(skb, reply);
 120
 121         down_read(&listeners->sem);
 122         list_for_each_entry(s, &listeners->list, list) {
 123                 int rc;
 124
 125                 skb_next = NULL;
 126                 if (!list_is_last(&s->list, &listeners->list)) {
 127                         skb_next = skb_clone(skb_cur, GFP_KERNEL);
 128                         if (!skb_next)
 129                                 break;
 130                 }
 131                 rc = genlmsg_unicast(&init_net, skb_cur, s->pid);
 132                 if (rc == -ECONNREFUSED) {
 133                         s->valid = 0;
 134                         delcount++;
 135                 }
 136                 skb_cur = skb_next;
 137         }
 138         up_read(&listeners->sem);
 139
 140         if (skb_cur)
 141                 nlmsg_free(skb_cur);
 142
 143         if (!delcount)
 144                 return;
 145
 146         /* Delete invalidated entries */
 147         down_write(&listeners->sem);
 148         list_for_each_entry_safe(s, tmp, &listeners->list, list) {
 149                 if (!s->valid) {
 150                         list_del(&s->list);
 151                         kfree(s);
 152                 }
 153         }
 154         up_write(&listeners->sem);
 155 }
 156
 157 static void exe_add_tsk(struct taskstats *stats, struct task_struct *tsk)
 158 {
 159         /* No idea if I'm allowed to access that here, now. */
 160         struct file *exe_file = get_task_exe_file(tsk);
 161
 162         if (exe_file) {
 163                 /* Following cp_new_stat64() in stat.c . */
 164                 stats->ac_exe_dev =
 165                         huge_encode_dev(exe_file->f_inode->i_sb->s_dev);
 166                 stats->ac_exe_inode = exe_file->f_inode->i_ino;
 167                 fput(exe_file);
 168         } else {
 169                 stats->ac_exe_dev = 0;
 170                 stats->ac_exe_inode = 0;
 171         }
 172 }
 173
 174 static void fill_stats(struct user_namespace *user_ns,
 175                        struct pid_namespace *pid_ns,
 176                        struct task_struct *tsk, struct taskstats *stats)
 177 {
 178         memset(stats, 0, sizeof(*stats));
 179         /*
 180          * Each accounting subsystem adds calls to its functions to
 181          * fill in relevant parts of struct taskstsats as follows
 182          *
 183          *      per-task-foo(stats, tsk);
 184          */
 185
 186         delayacct_add_tsk(stats, tsk);
 187
 188         /* fill in basic acct fields */
 189         stats->version = TASKSTATS_VERSION;
 190         stats->nvcsw = tsk->nvcsw;
 191         stats->nivcsw = tsk->nivcsw;
 192         bacct_add_tsk(user_ns, pid_ns, stats, tsk);
 193
 194         /* fill in extended acct fields */
 195         xacct_add_tsk(stats, tsk);
 196
 197         /* add executable info */
 198         exe_add_tsk(stats, tsk);
 199 }
 200
 201 static int fill_stats_for_pid(pid_t pid, struct taskstats *stats)
 202 {
 203         struct task_struct *tsk;
 204
 205         tsk = find_get_task_by_vpid(pid);
 206         if (!tsk)
 207                 return -ESRCH;
 208         fill_stats(current_user_ns(), task_active_pid_ns(current), tsk, stats);
 209         put_task_struct(tsk);
 210         return 0;
 211 }
 212
 213 static int fill_stats_for_tgid(pid_t tgid, struct taskstats *stats)
 214 {
 215         struct task_struct *tsk, *first;
 216         unsigned long flags;
 217         int rc = -ESRCH;
 218         u64 delta, utime, stime;
 219         u64 start_time;
 220
 221         /*
 222          * Add additional stats from live tasks except zombie thread group
 223          * leaders who are already counted with the dead tasks
 224          */
 225         rcu_read_lock();
 226         first = find_task_by_vpid(tgid);
 227
 228         if (!first || !lock_task_sighand(first, &flags))
 229                 goto out;
 230
 231         if (first->signal->stats)
 232                 memcpy(stats, first->signal->stats, sizeof(*stats));
 233         else
 234                 memset(stats, 0, sizeof(*stats));
 235
 236         start_time = ktime_get_ns();
 237         for_each_thread(first, tsk) {
 238                 if (tsk->exit_state)
 239                         continue;
 240                 /*
 241                  * Accounting subsystem can call its functions here to
 242                  * fill in relevant parts of struct taskstsats as follows
 243                  *
 244                  *      per-task-foo(stats, tsk);
 245                  */
 246                 delayacct_add_tsk(stats, tsk);
 247
 248                 /* calculate task elapsed time in nsec */
 249                 delta = start_time - tsk->start_time;
 250                 /* Convert to micro seconds */
 251                 do_div(delta, NSEC_PER_USEC);
 252                 stats->ac_etime += delta;
 253
 254                 task_cputime(tsk, &utime, &stime);
 255                 stats->ac_utime += div_u64(utime, NSEC_PER_USEC);
 256                 stats->ac_stime += div_u64(stime, NSEC_PER_USEC);
 257
 258                 stats->nvcsw += tsk->nvcsw;
 259                 stats->nivcsw += tsk->nivcsw;
 260         }
 261
 262         unlock_task_sighand(first, &flags);
 263         rc = 0;
 264 out:
 265         rcu_read_unlock();
 266
 267         stats->version = TASKSTATS_VERSION;
 268         /*
 269          * Accounting subsystems can also add calls here to modify
 270          * fields of taskstats.
 271          */
 272         return rc;
 273 }
 274
 275 static void fill_tgid_exit(struct task_struct *tsk)
 276 {
 277         unsigned long flags;
 278
 279         spin_lock_irqsave(&tsk->sighand->siglock, flags);
 280         if (!tsk->signal->stats)
 281                 goto ret;
 282
 283         /*
 284          * Each accounting subsystem calls its functions here to
 285          * accumalate its per-task stats for tsk, into the per-tgid structure
 286          *
 287          *      per-task-foo(tsk->signal->stats, tsk);
 288          */
 289         delayacct_add_tsk(tsk->signal->stats, tsk);
 290 ret:
 291         spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
 292         return;
 293 }
 294
 295 static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)
 296 {
 297         struct listener_list *listeners;
 298         struct listener *s, *tmp, *s2;
 299         unsigned int cpu;
 300         int ret = 0;
 301
 302         if (!cpumask_subset(mask, cpu_possible_mask))
 303                 return -EINVAL;
 304
 305         if (current_user_ns() != &init_user_ns)
 306                 return -EINVAL;
 307
 308         if (task_active_pid_ns(current) != &init_pid_ns)
 309                 return -EINVAL;
 310
 311         if (isadd == REGISTER) {
 312                 for_each_cpu(cpu, mask) {
 313                         s = kmalloc_node(sizeof(struct listener),
 314                                         GFP_KERNEL, cpu_to_node(cpu));
 315                         if (!s) {
 316                                 ret = -ENOMEM;
 317                                 goto cleanup;
 318                         }
 319                         s->pid = pid;
 320                         s->valid = 1;
 321
 322                         listeners = &per_cpu(listener_array, cpu);
 323                         down_write(&listeners->sem);
 324                         list_for_each_entry(s2, &listeners->list, list) {
 325                                 if (s2->pid == pid && s2->valid)
 326                                         goto exists;
 327                         }
 328                         list_add(&s->list, &listeners->list);
 329                         s = NULL;
 330 exists:
 331                         up_write(&listeners->sem);
 332                         kfree(s); /* nop if NULL */
 333                 }
 334                 return 0;
 335         }
 336
 337         /* Deregister or cleanup */
 338 cleanup:
 339         for_each_cpu(cpu, mask) {
 340                 listeners = &per_cpu(listener_array, cpu);
 341                 down_write(&listeners->sem);
 342                 list_for_each_entry_safe(s, tmp, &listeners->list, list) {
 343                         if (s->pid == pid) {
 344                                 list_del(&s->list);
 345                                 kfree(s);
 346                                 break;
 347                         }
 348                 }
 349                 up_write(&listeners->sem);
 350         }
 351         return ret;
 352 }
 353
 354 static int parse(struct nlattr *na, struct cpumask *mask)
 355 {
 356         char *data;
 357         int len;
 358         int ret;
 359
 360         if (na == NULL)
 361                 return 1;
 362         len = nla_len(na);
 363         if (len > TASKSTATS_CPUMASK_MAXLEN)
 364                 return -E2BIG;
 365         if (len < 1)
 366                 return -EINVAL;
 367         data = kmalloc(len, GFP_KERNEL);
 368         if (!data)
 369                 return -ENOMEM;
 370         nla_strscpy(data, na, len);
 371         ret = cpulist_parse(data, mask);
 372         kfree(data);
 373         return ret;
 374 }
 375
 376 static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
 377 {
 378         struct nlattr *na, *ret;
 379         int aggr;
 380
 381         aggr = (type == TASKSTATS_TYPE_PID)
 382                         ? TASKSTATS_TYPE_AGGR_PID
 383                         : TASKSTATS_TYPE_AGGR_TGID;
 384
 385         na = nla_nest_start_noflag(skb, aggr);
 386         if (!na)
 387                 goto err;
 388
 389         if (nla_put(skb, type, sizeof(pid), &pid) < 0) {
 390                 nla_nest_cancel(skb, na);
 391                 goto err;
 392         }
 393         ret = nla_reserve_64bit(skb, TASKSTATS_TYPE_STATS,
 394                                 sizeof(struct taskstats), TASKSTATS_TYPE_NULL);
 395         if (!ret) {
 396                 nla_nest_cancel(skb, na);
 397                 goto err;
 398         }
 399         nla_nest_end(skb, na);
 400
 401         return nla_data(ret);
 402 err:
 403         return NULL;
 404 }
 405
 406 static int cgroupstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
 407 {
 408         int rc = 0;
 409         struct sk_buff *rep_skb;
 410         struct cgroupstats *stats;
 411         struct nlattr *na;
 412         size_t size;
 413         u32 fd;
 414
 415         na = info->attrs[CGROUPSTATS_CMD_ATTR_FD];
 416         if (!na)
 417                 return -EINVAL;
 418
 419         fd = nla_get_u32(info->attrs[CGROUPSTATS_CMD_ATTR_FD]);
 420         CLASS(fd, f)(fd);
 421         if (fd_empty(f))
 422                 return 0;
 423
 424         size = nla_total_size(sizeof(struct cgroupstats));
 425
 426         rc = prepare_reply(info, CGROUPSTATS_CMD_NEW, &rep_skb,
 427                                 size);
 428         if (rc < 0)
 429                 return rc;
 430
 431         na = nla_reserve(rep_skb, CGROUPSTATS_TYPE_CGROUP_STATS,
 432                                 sizeof(struct cgroupstats));
 433         if (na == NULL) {
 434                 nlmsg_free(rep_skb);
 435                 return -EMSGSIZE;
 436         }
 437
 438         stats = nla_data(na);
 439         memset(stats, 0, sizeof(*stats));
 440
 441         rc = cgroupstats_build(stats, fd_file(f)->f_path.dentry);
 442         if (rc < 0) {
 443                 nlmsg_free(rep_skb);
 444                 return rc;
 445         }
 446
 447         return send_reply(rep_skb, info);
 448 }
 449
 450 static int cmd_attr_register_cpumask(struct genl_info *info)
 451 {
 452         cpumask_var_t mask;
 453         int rc;
 454
 455         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
 456                 return -ENOMEM;
 457         rc = parse(info->attrs[TASKSTATS_CMD_ATTR_REGISTER_CPUMASK], mask);
 458         if (rc < 0)
 459                 goto out;
 460         rc = add_del_listener(info->snd_portid, mask, REGISTER);
 461 out:
 462         free_cpumask_var(mask);
 463         return rc;
 464 }
 465
 466 static int cmd_attr_deregister_cpumask(struct genl_info *info)
 467 {
 468         cpumask_var_t mask;
 469         int rc;
 470
 471         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
 472                 return -ENOMEM;
 473         rc = parse(info->attrs[TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK], mask);
 474         if (rc < 0)
 475                 goto out;
 476         rc = add_del_listener(info->snd_portid, mask, DEREGISTER);
 477 out:
 478         free_cpumask_var(mask);
 479         return rc;
 480 }
 481
 482 static size_t taskstats_packet_size(void)
 483 {
 484         size_t size;
 485
 486         size = nla_total_size(sizeof(u32)) +
 487                 nla_total_size_64bit(sizeof(struct taskstats)) +
 488                 nla_total_size(0);
 489
 490         return size;
 491 }
 492
 493 static int cmd_attr_pid(struct genl_info *info)
 494 {
 495         struct taskstats *stats;
 496         struct sk_buff *rep_skb;
 497         size_t size;
 498         u32 pid;
 499         int rc;
 500
 501         size = taskstats_packet_size();
 502
 503         rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);
 504         if (rc < 0)
 505                 return rc;
 506
 507         rc = -EINVAL;
 508         pid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_PID]);
 509         stats = mk_reply(rep_skb, TASKSTATS_TYPE_PID, pid);
 510         if (!stats)
 511                 goto err;
 512
 513         rc = fill_stats_for_pid(pid, stats);
 514         if (rc < 0)
 515                 goto err;
 516         return send_reply(rep_skb, info);
 517 err:
 518         nlmsg_free(rep_skb);
 519         return rc;
 520 }
 521
 522 static int cmd_attr_tgid(struct genl_info *info)
 523 {
 524         struct taskstats *stats;
 525         struct sk_buff *rep_skb;
 526         size_t size;
 527         u32 tgid;
 528         int rc;
 529
 530         size = taskstats_packet_size();
 531
 532         rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);
 533         if (rc < 0)
 534                 return rc;
 535
 536         rc = -EINVAL;
 537         tgid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_TGID]);
 538         stats = mk_reply(rep_skb, TASKSTATS_TYPE_TGID, tgid);
 539         if (!stats)
 540                 goto err;
 541
 542         rc = fill_stats_for_tgid(tgid, stats);
 543         if (rc < 0)
 544                 goto err;
 545         return send_reply(rep_skb, info);
 546 err:
 547         nlmsg_free(rep_skb);
 548         return rc;
 549 }
 550
 551 static int taskstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
 552 {
 553         if (info->attrs[TASKSTATS_CMD_ATTR_REGISTER_CPUMASK])
 554                 return cmd_attr_register_cpumask(info);
 555         else if (info->attrs[TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK])
 556                 return cmd_attr_deregister_cpumask(info);
 557         else if (info->attrs[TASKSTATS_CMD_ATTR_PID])
 558                 return cmd_attr_pid(info);
 559         else if (info->attrs[TASKSTATS_CMD_ATTR_TGID])
 560                 return cmd_attr_tgid(info);
 561         else
 562                 return -EINVAL;
 563 }
 564
 565 static struct taskstats *taskstats_tgid_alloc(struct task_struct *tsk)
 566 {
 567         struct signal_struct *sig = tsk->signal;
 568         struct taskstats *stats_new, *stats;
 569
 570         /* Pairs with smp_store_release() below. */
 571         stats = smp_load_acquire(&sig->stats);
 572         if (stats || thread_group_empty(tsk))
 573                 return stats;
 574
 575         /* No problem if kmem_cache_zalloc() fails */
 576         stats_new = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL);
 577
 578         spin_lock_irq(&tsk->sighand->siglock);
 579         stats = sig->stats;
 580         if (!stats) {
 581                 /*
 582                  * Pairs with smp_store_release() above and order the
 583                  * kmem_cache_zalloc().
 584                  */
 585                 smp_store_release(&sig->stats, stats_new);
 586                 stats = stats_new;
 587                 stats_new = NULL;
 588         }
 589         spin_unlock_irq(&tsk->sighand->siglock);
 590
 591         if (stats_new)
 592                 kmem_cache_free(taskstats_cache, stats_new);
 593
 594         return stats;
 595 }
 596
 597 /* Send pid data out on exit */
 598 void taskstats_exit(struct task_struct *tsk, int group_dead)
 599 {
 600         int rc;
 601         struct listener_list *listeners;
 602         struct taskstats *stats;
 603         struct sk_buff *rep_skb;
 604         size_t size;
 605         int is_thread_group;
 606
 607         if (!family_registered)
 608                 return;
 609
 610         /*
 611          * Size includes space for nested attributes
 612          */
 613         size = taskstats_packet_size();
 614
 615         is_thread_group = !!taskstats_tgid_alloc(tsk);
 616         if (is_thread_group) {
 617                 /* PID + STATS + TGID + STATS */
 618                 size = 2 * size;
 619                 /* fill the tsk->signal->stats structure */
 620                 fill_tgid_exit(tsk);
 621         }
 622
 623         listeners = raw_cpu_ptr(&listener_array);
 624         if (list_empty(&listeners->list))
 625                 return;
 626
 627         rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, size);
 628         if (rc < 0)
 629                 return;
 630
 631         stats = mk_reply(rep_skb, TASKSTATS_TYPE_PID,
 632                          task_pid_nr_ns(tsk, &init_pid_ns));
 633         if (!stats)
 634                 goto err;
 635
 636         fill_stats(&init_user_ns, &init_pid_ns, tsk, stats);
 637         if (group_dead)
 638                 stats->ac_flag |= AGROUP;
 639
 640         /*
 641          * Doesn't matter if tsk is the leader or the last group member leaving
 642          */
 643         if (!is_thread_group || !group_dead)
 644                 goto send;
 645
 646         stats = mk_reply(rep_skb, TASKSTATS_TYPE_TGID,
 647                          task_tgid_nr_ns(tsk, &init_pid_ns));
 648         if (!stats)
 649                 goto err;
 650
 651         memcpy(stats, tsk->signal->stats, sizeof(*stats));
 652
 653 send:
 654         send_cpu_listeners(rep_skb, listeners);
 655         return;
 656 err:
 657         nlmsg_free(rep_skb);
 658 }
 659
 660 static const struct genl_ops taskstats_ops[] = {
 661         {
 662                 .cmd            = TASKSTATS_CMD_GET,
 663                 .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 664                 .doit           = taskstats_user_cmd,
 665                 .policy         = taskstats_cmd_get_policy,
 666                 .maxattr        = ARRAY_SIZE(taskstats_cmd_get_policy) - 1,
 667                 .flags          = GENL_ADMIN_PERM,
 668         },
 669         {
 670                 .cmd            = CGROUPSTATS_CMD_GET,
 671                 .validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
 672                 .doit           = cgroupstats_user_cmd,
 673                 .policy         = cgroupstats_cmd_get_policy,
 674                 .maxattr        = ARRAY_SIZE(cgroupstats_cmd_get_policy) - 1,
 675         },
 676 };
 677
 678 static struct genl_family family __ro_after_init = {
 679         .name           = TASKSTATS_GENL_NAME,
 680         .version        = TASKSTATS_GENL_VERSION,
 681         .module         = THIS_MODULE,
 682         .ops            = taskstats_ops,
 683         .n_ops          = ARRAY_SIZE(taskstats_ops),
 684         .resv_start_op  = CGROUPSTATS_CMD_GET + 1,
 685         .netnsok        = true,
 686 };
 687
 688 /* Needed early in initialization */
 689 void __init taskstats_init_early(void)
 690 {
 691         unsigned int i;
 692
 693         taskstats_cache = KMEM_CACHE(taskstats, SLAB_PANIC);
 694         for_each_possible_cpu(i) {
 695                 INIT_LIST_HEAD(&(per_cpu(listener_array, i).list));
 696                 init_rwsem(&(per_cpu(listener_array, i).sem));
 697         }
 698 }
 699
 700 static int __init taskstats_init(void)
 701 {
 702         int rc;
 703
 704         rc = genl_register_family(&family);
 705         if (rc)
 706                 return rc;
 707
 708         family_registered = 1;
 709         pr_info("registered taskstats version %d\n", TASKSTATS_GENL_VERSION);
 710         return 0;
 711 }
 712
 713 /*
 714  * late initcall ensures initialization of statistics collection
 715  * mechanisms precedes initialization of the taskstats interface
 716  */
 717 late_initcall(taskstats_init);