kernel/taskstats.c

   1 /*
   2  * taskstats.c - Export per-task statistics to userland
   3  *
   4  * Copyright (C) Shailabh Nagar, IBM Corp. 2006
   5  *           (C) Balbir Singh,   IBM Corp. 2006
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  */
  18
  19 #include <linux/kernel.h>
  20 #include <linux/taskstats_kern.h>
  21 #include <linux/tsacct_kern.h>
  22 #include <linux/delayacct.h>
  23 #include <linux/cpumask.h>
  24 #include <linux/percpu.h>
  25 #include <linux/slab.h>
  26 #include <linux/cgroupstats.h>
  27 #include <linux/cgroup.h>
  28 #include <linux/fs.h>
  29 #include <linux/file.h>
  30 #include <linux/pid_namespace.h>
  31 #include <net/genetlink.h>
  32 #include <linux/atomic.h>
  33
  34 /*
  35  * Maximum length of a cpumask that can be specified in
  36  * the TASKSTATS_CMD_ATTR_REGISTER/DEREGISTER_CPUMASK attribute
  37  */
  38 #define TASKSTATS_CPUMASK_MAXLEN        (100+6*NR_CPUS)
  39
  40 static DEFINE_PER_CPU(__u32, taskstats_seqnum);
  41 static int family_registered;
  42 struct kmem_cache *taskstats_cache;
  43
  44 static struct genl_family family = {
  45         .id             = GENL_ID_GENERATE,
  46         .name           = TASKSTATS_GENL_NAME,
  47         .version        = TASKSTATS_GENL_VERSION,
  48         .maxattr        = TASKSTATS_CMD_ATTR_MAX,
  49 };
  50
  51 static const struct nla_policy taskstats_cmd_get_policy[TASKSTATS_CMD_ATTR_MAX+1] = {
  52         [TASKSTATS_CMD_ATTR_PID]  = { .type = NLA_U32 },
  53         [TASKSTATS_CMD_ATTR_TGID] = { .type = NLA_U32 },
  54         [TASKSTATS_CMD_ATTR_REGISTER_CPUMASK] = { .type = NLA_STRING },
  55         [TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK] = { .type = NLA_STRING },};
  56
  57 static const struct nla_policy cgroupstats_cmd_get_policy[CGROUPSTATS_CMD_ATTR_MAX+1] = {
  58         [CGROUPSTATS_CMD_ATTR_FD] = { .type = NLA_U32 },
  59 };
  60
  61 struct listener {
  62         struct list_head list;
  63         pid_t pid;
  64         char valid;
  65 };
  66
  67 struct listener_list {
  68         struct rw_semaphore sem;
  69         struct list_head list;
  70 };
  71 static DEFINE_PER_CPU(struct listener_list, listener_array);
  72
  73 enum actions {
  74         REGISTER,
  75         DEREGISTER,
  76         CPU_DONT_CARE
  77 };
  78
  79 static int prepare_reply(struct genl_info *info, u8 cmd, struct sk_buff **skbp,
  80                                 size_t size)
  81 {
  82         struct sk_buff *skb;
  83         void *reply;
  84
  85         /*
  86          * If new attributes are added, please revisit this allocation
  87          */
  88         skb = genlmsg_new(size, GFP_KERNEL);
  89         if (!skb)
  90                 return -ENOMEM;
  91
  92         if (!info) {
  93                 int seq = this_cpu_inc_return(taskstats_seqnum) - 1;
  94
  95                 reply = genlmsg_put(skb, 0, seq, &family, 0, cmd);
  96         } else
  97                 reply = genlmsg_put_reply(skb, info, &family, 0, cmd);
  98         if (reply == NULL) {
  99                 nlmsg_free(skb);
 100                 return -EINVAL;
 101         }
 102
 103         *skbp = skb;
 104         return 0;
 105 }
 106
 107 /*
 108  * Send taskstats data in @skb to listener with nl_pid @pid
 109  */
 110 static int send_reply(struct sk_buff *skb, struct genl_info *info)
 111 {
 112         struct genlmsghdr *genlhdr = nlmsg_data(nlmsg_hdr(skb));
 113         void *reply = genlmsg_data(genlhdr);
 114         int rc;
 115
 116         rc = genlmsg_end(skb, reply);
 117         if (rc < 0) {
 118                 nlmsg_free(skb);
 119                 return rc;
 120         }
 121
 122         return genlmsg_reply(skb, info);
 123 }
 124
 125 /*
 126  * Send taskstats data in @skb to listeners registered for @cpu's exit data
 127  */
 128 static void send_cpu_listeners(struct sk_buff *skb,
 129                                         struct listener_list *listeners)
 130 {
 131         struct genlmsghdr *genlhdr = nlmsg_data(nlmsg_hdr(skb));
 132         struct listener *s, *tmp;
 133         struct sk_buff *skb_next, *skb_cur = skb;
 134         void *reply = genlmsg_data(genlhdr);
 135         int rc, delcount = 0;
 136
 137         rc = genlmsg_end(skb, reply);
 138         if (rc < 0) {
 139                 nlmsg_free(skb);
 140                 return;
 141         }
 142
 143         rc = 0;
 144         down_read(&listeners->sem);
 145         list_for_each_entry(s, &listeners->list, list) {
 146                 skb_next = NULL;
 147                 if (!list_is_last(&s->list, &listeners->list)) {
 148                         skb_next = skb_clone(skb_cur, GFP_KERNEL);
 149                         if (!skb_next)
 150                                 break;
 151                 }
 152                 rc = genlmsg_unicast(&init_net, skb_cur, s->pid);
 153                 if (rc == -ECONNREFUSED) {
 154                         s->valid = 0;
 155                         delcount++;
 156                 }
 157                 skb_cur = skb_next;
 158         }
 159         up_read(&listeners->sem);
 160
 161         if (skb_cur)
 162                 nlmsg_free(skb_cur);
 163
 164         if (!delcount)
 165                 return;
 166
 167         /* Delete invalidated entries */
 168         down_write(&listeners->sem);
 169         list_for_each_entry_safe(s, tmp, &listeners->list, list) {
 170                 if (!s->valid) {
 171                         list_del(&s->list);
 172                         kfree(s);
 173                 }
 174         }
 175         up_write(&listeners->sem);
 176 }
 177
 178 static void fill_stats(struct user_namespace *user_ns,
 179                        struct pid_namespace *pid_ns,
 180                        struct task_struct *tsk, struct taskstats *stats)
 181 {
 182         memset(stats, 0, sizeof(*stats));
 183         /*
 184          * Each accounting subsystem adds calls to its functions to
 185          * fill in relevant parts of struct taskstsats as follows
 186          *
 187          *      per-task-foo(stats, tsk);
 188          */
 189
 190         delayacct_add_tsk(stats, tsk);
 191
 192         /* fill in basic acct fields */
 193         stats->version = TASKSTATS_VERSION;
 194         stats->nvcsw = tsk->nvcsw;
 195         stats->nivcsw = tsk->nivcsw;
 196         bacct_add_tsk(user_ns, pid_ns, stats, tsk);
 197
 198         /* fill in extended acct fields */
 199         xacct_add_tsk(stats, tsk);
 200 }
 201
 202 static int fill_stats_for_pid(pid_t pid, struct taskstats *stats)
 203 {
 204         struct task_struct *tsk;
 205
 206         rcu_read_lock();
 207         tsk = find_task_by_vpid(pid);
 208         if (tsk)
 209                 get_task_struct(tsk);
 210         rcu_read_unlock();
 211         if (!tsk)
 212                 return -ESRCH;
 213         fill_stats(current_user_ns(), task_active_pid_ns(current), tsk, stats);
 214         put_task_struct(tsk);
 215         return 0;
 216 }
 217
 218 static int fill_stats_for_tgid(pid_t tgid, struct taskstats *stats)
 219 {
 220         struct task_struct *tsk, *first;
 221         unsigned long flags;
 222         int rc = -ESRCH;
 223
 224         /*
 225          * Add additional stats from live tasks except zombie thread group
 226          * leaders who are already counted with the dead tasks
 227          */
 228         rcu_read_lock();
 229         first = find_task_by_vpid(tgid);
 230
 231         if (!first || !lock_task_sighand(first, &flags))
 232                 goto out;
 233
 234         if (first->signal->stats)
 235                 memcpy(stats, first->signal->stats, sizeof(*stats));
 236         else
 237                 memset(stats, 0, sizeof(*stats));
 238
 239         tsk = first;
 240         do {
 241                 if (tsk->exit_state)
 242                         continue;
 243                 /*
 244                  * Accounting subsystem can call its functions here to
 245                  * fill in relevant parts of struct taskstsats as follows
 246                  *
 247                  *      per-task-foo(stats, tsk);
 248                  */
 249                 delayacct_add_tsk(stats, tsk);
 250
 251                 stats->nvcsw += tsk->nvcsw;
 252                 stats->nivcsw += tsk->nivcsw;
 253         } while_each_thread(first, tsk);
 254
 255         unlock_task_sighand(first, &flags);
 256         rc = 0;
 257 out:
 258         rcu_read_unlock();
 259
 260         stats->version = TASKSTATS_VERSION;
 261         /*
 262          * Accounting subsystems can also add calls here to modify
 263          * fields of taskstats.
 264          */
 265         return rc;
 266 }
 267
 268 static void fill_tgid_exit(struct task_struct *tsk)
 269 {
 270         unsigned long flags;
 271
 272         spin_lock_irqsave(&tsk->sighand->siglock, flags);
 273         if (!tsk->signal->stats)
 274                 goto ret;
 275
 276         /*
 277          * Each accounting subsystem calls its functions here to
 278          * accumalate its per-task stats for tsk, into the per-tgid structure
 279          *
 280          *      per-task-foo(tsk->signal->stats, tsk);
 281          */
 282         delayacct_add_tsk(tsk->signal->stats, tsk);
 283 ret:
 284         spin_unlock_irqrestore(&tsk->sighand->siglock, flags);
 285         return;
 286 }
 287
 288 static int add_del_listener(pid_t pid, const struct cpumask *mask, int isadd)
 289 {
 290         struct listener_list *listeners;
 291         struct listener *s, *tmp, *s2;
 292         unsigned int cpu;
 293         int ret = 0;
 294
 295         if (!cpumask_subset(mask, cpu_possible_mask))
 296                 return -EINVAL;
 297
 298         if (current_user_ns() != &init_user_ns)
 299                 return -EINVAL;
 300
 301         if (task_active_pid_ns(current) != &init_pid_ns)
 302                 return -EINVAL;
 303
 304         if (isadd == REGISTER) {
 305                 for_each_cpu(cpu, mask) {
 306                         s = kmalloc_node(sizeof(struct listener),
 307                                         GFP_KERNEL, cpu_to_node(cpu));
 308                         if (!s) {
 309                                 ret = -ENOMEM;
 310                                 goto cleanup;
 311                         }
 312                         s->pid = pid;
 313                         s->valid = 1;
 314
 315                         listeners = &per_cpu(listener_array, cpu);
 316                         down_write(&listeners->sem);
 317                         list_for_each_entry(s2, &listeners->list, list) {
 318                                 if (s2->pid == pid && s2->valid)
 319                                         goto exists;
 320                         }
 321                         list_add(&s->list, &listeners->list);
 322                         s = NULL;
 323 exists:
 324                         up_write(&listeners->sem);
 325                         kfree(s); /* nop if NULL */
 326                 }
 327                 return 0;
 328         }
 329
 330         /* Deregister or cleanup */
 331 cleanup:
 332         for_each_cpu(cpu, mask) {
 333                 listeners = &per_cpu(listener_array, cpu);
 334                 down_write(&listeners->sem);
 335                 list_for_each_entry_safe(s, tmp, &listeners->list, list) {
 336                         if (s->pid == pid) {
 337                                 list_del(&s->list);
 338                                 kfree(s);
 339                                 break;
 340                         }
 341                 }
 342                 up_write(&listeners->sem);
 343         }
 344         return ret;
 345 }
 346
 347 static int parse(struct nlattr *na, struct cpumask *mask)
 348 {
 349         char *data;
 350         int len;
 351         int ret;
 352
 353         if (na == NULL)
 354                 return 1;
 355         len = nla_len(na);
 356         if (len > TASKSTATS_CPUMASK_MAXLEN)
 357                 return -E2BIG;
 358         if (len < 1)
 359                 return -EINVAL;
 360         data = kmalloc(len, GFP_KERNEL);
 361         if (!data)
 362                 return -ENOMEM;
 363         nla_strlcpy(data, na, len);
 364         ret = cpulist_parse(data, mask);
 365         kfree(data);
 366         return ret;
 367 }
 368
 369 #if defined(CONFIG_64BIT) && !defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
 370 #define TASKSTATS_NEEDS_PADDING 1
 371 #endif
 372
 373 static struct taskstats *mk_reply(struct sk_buff *skb, int type, u32 pid)
 374 {
 375         struct nlattr *na, *ret;
 376         int aggr;
 377
 378         aggr = (type == TASKSTATS_TYPE_PID)
 379                         ? TASKSTATS_TYPE_AGGR_PID
 380                         : TASKSTATS_TYPE_AGGR_TGID;
 381
 382         /*
 383          * The taskstats structure is internally aligned on 8 byte
 384          * boundaries but the layout of the aggregrate reply, with
 385          * two NLA headers and the pid (each 4 bytes), actually
 386          * force the entire structure to be unaligned. This causes
 387          * the kernel to issue unaligned access warnings on some
 388          * architectures like ia64. Unfortunately, some software out there
 389          * doesn't properly unroll the NLA packet and assumes that the start
 390          * of the taskstats structure will always be 20 bytes from the start
 391          * of the netlink payload. Aligning the start of the taskstats
 392          * structure breaks this software, which we don't want. So, for now
 393          * the alignment only happens on architectures that require it
 394          * and those users will have to update to fixed versions of those
 395          * packages. Space is reserved in the packet only when needed.
 396          * This ifdef should be removed in several years e.g. 2012 once
 397          * we can be confident that fixed versions are installed on most
 398          * systems. We add the padding before the aggregate since the
 399          * aggregate is already a defined type.
 400          */
 401 #ifdef TASKSTATS_NEEDS_PADDING
 402         if (nla_put(skb, TASKSTATS_TYPE_NULL, 0, NULL) < 0)
 403                 goto err;
 404 #endif
 405         na = nla_nest_start(skb, aggr);
 406         if (!na)
 407                 goto err;
 408
 409         if (nla_put(skb, type, sizeof(pid), &pid) < 0) {
 410                 nla_nest_cancel(skb, na);
 411                 goto err;
 412         }
 413         ret = nla_reserve(skb, TASKSTATS_TYPE_STATS, sizeof(struct taskstats));
 414         if (!ret) {
 415                 nla_nest_cancel(skb, na);
 416                 goto err;
 417         }
 418         nla_nest_end(skb, na);
 419
 420         return nla_data(ret);
 421 err:
 422         return NULL;
 423 }
 424
 425 static int cgroupstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
 426 {
 427         int rc = 0;
 428         struct sk_buff *rep_skb;
 429         struct cgroupstats *stats;
 430         struct nlattr *na;
 431         size_t size;
 432         u32 fd;
 433         struct fd f;
 434
 435         na = info->attrs[CGROUPSTATS_CMD_ATTR_FD];
 436         if (!na)
 437                 return -EINVAL;
 438
 439         fd = nla_get_u32(info->attrs[CGROUPSTATS_CMD_ATTR_FD]);
 440         f = fdget(fd);
 441         if (!f.file)
 442                 return 0;
 443
 444         size = nla_total_size(sizeof(struct cgroupstats));
 445
 446         rc = prepare_reply(info, CGROUPSTATS_CMD_NEW, &rep_skb,
 447                                 size);
 448         if (rc < 0)
 449                 goto err;
 450
 451         na = nla_reserve(rep_skb, CGROUPSTATS_TYPE_CGROUP_STATS,
 452                                 sizeof(struct cgroupstats));
 453         if (na == NULL) {
 454                 nlmsg_free(rep_skb);
 455                 rc = -EMSGSIZE;
 456                 goto err;
 457         }
 458
 459         stats = nla_data(na);
 460         memset(stats, 0, sizeof(*stats));
 461
 462         rc = cgroupstats_build(stats, f.file->f_dentry);
 463         if (rc < 0) {
 464                 nlmsg_free(rep_skb);
 465                 goto err;
 466         }
 467
 468         rc = send_reply(rep_skb, info);
 469
 470 err:
 471         fdput(f);
 472         return rc;
 473 }
 474
 475 static int cmd_attr_register_cpumask(struct genl_info *info)
 476 {
 477         cpumask_var_t mask;
 478         int rc;
 479
 480         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
 481                 return -ENOMEM;
 482         rc = parse(info->attrs[TASKSTATS_CMD_ATTR_REGISTER_CPUMASK], mask);
 483         if (rc < 0)
 484                 goto out;
 485         rc = add_del_listener(info->snd_portid, mask, REGISTER);
 486 out:
 487         free_cpumask_var(mask);
 488         return rc;
 489 }
 490
 491 static int cmd_attr_deregister_cpumask(struct genl_info *info)
 492 {
 493         cpumask_var_t mask;
 494         int rc;
 495
 496         if (!alloc_cpumask_var(&mask, GFP_KERNEL))
 497                 return -ENOMEM;
 498         rc = parse(info->attrs[TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK], mask);
 499         if (rc < 0)
 500                 goto out;
 501         rc = add_del_listener(info->snd_portid, mask, DEREGISTER);
 502 out:
 503         free_cpumask_var(mask);
 504         return rc;
 505 }
 506
 507 static size_t taskstats_packet_size(void)
 508 {
 509         size_t size;
 510
 511         size = nla_total_size(sizeof(u32)) +
 512                 nla_total_size(sizeof(struct taskstats)) + nla_total_size(0);
 513 #ifdef TASKSTATS_NEEDS_PADDING
 514         size += nla_total_size(0); /* Padding for alignment */
 515 #endif
 516         return size;
 517 }
 518
 519 static int cmd_attr_pid(struct genl_info *info)
 520 {
 521         struct taskstats *stats;
 522         struct sk_buff *rep_skb;
 523         size_t size;
 524         u32 pid;
 525         int rc;
 526
 527         size = taskstats_packet_size();
 528
 529         rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);
 530         if (rc < 0)
 531                 return rc;
 532
 533         rc = -EINVAL;
 534         pid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_PID]);
 535         stats = mk_reply(rep_skb, TASKSTATS_TYPE_PID, pid);
 536         if (!stats)
 537                 goto err;
 538
 539         rc = fill_stats_for_pid(pid, stats);
 540         if (rc < 0)
 541                 goto err;
 542         return send_reply(rep_skb, info);
 543 err:
 544         nlmsg_free(rep_skb);
 545         return rc;
 546 }
 547
 548 static int cmd_attr_tgid(struct genl_info *info)
 549 {
 550         struct taskstats *stats;
 551         struct sk_buff *rep_skb;
 552         size_t size;
 553         u32 tgid;
 554         int rc;
 555
 556         size = taskstats_packet_size();
 557
 558         rc = prepare_reply(info, TASKSTATS_CMD_NEW, &rep_skb, size);
 559         if (rc < 0)
 560                 return rc;
 561
 562         rc = -EINVAL;
 563         tgid = nla_get_u32(info->attrs[TASKSTATS_CMD_ATTR_TGID]);
 564         stats = mk_reply(rep_skb, TASKSTATS_TYPE_TGID, tgid);
 565         if (!stats)
 566                 goto err;
 567
 568         rc = fill_stats_for_tgid(tgid, stats);
 569         if (rc < 0)
 570                 goto err;
 571         return send_reply(rep_skb, info);
 572 err:
 573         nlmsg_free(rep_skb);
 574         return rc;
 575 }
 576
 577 static int taskstats_user_cmd(struct sk_buff *skb, struct genl_info *info)
 578 {
 579         if (info->attrs[TASKSTATS_CMD_ATTR_REGISTER_CPUMASK])
 580                 return cmd_attr_register_cpumask(info);
 581         else if (info->attrs[TASKSTATS_CMD_ATTR_DEREGISTER_CPUMASK])
 582                 return cmd_attr_deregister_cpumask(info);
 583         else if (info->attrs[TASKSTATS_CMD_ATTR_PID])
 584                 return cmd_attr_pid(info);
 585         else if (info->attrs[TASKSTATS_CMD_ATTR_TGID])
 586                 return cmd_attr_tgid(info);
 587         else
 588                 return -EINVAL;
 589 }
 590
 591 static struct taskstats *taskstats_tgid_alloc(struct task_struct *tsk)
 592 {
 593         struct signal_struct *sig = tsk->signal;
 594         struct taskstats *stats;
 595
 596         if (sig->stats || thread_group_empty(tsk))
 597                 goto ret;
 598
 599         /* No problem if kmem_cache_zalloc() fails */
 600         stats = kmem_cache_zalloc(taskstats_cache, GFP_KERNEL);
 601
 602         spin_lock_irq(&tsk->sighand->siglock);
 603         if (!sig->stats) {
 604                 sig->stats = stats;
 605                 stats = NULL;
 606         }
 607         spin_unlock_irq(&tsk->sighand->siglock);
 608
 609         if (stats)
 610                 kmem_cache_free(taskstats_cache, stats);
 611 ret:
 612         return sig->stats;
 613 }
 614
 615 /* Send pid data out on exit */
 616 void taskstats_exit(struct task_struct *tsk, int group_dead)
 617 {
 618         int rc;
 619         struct listener_list *listeners;
 620         struct taskstats *stats;
 621         struct sk_buff *rep_skb;
 622         size_t size;
 623         int is_thread_group;
 624
 625         if (!family_registered)
 626                 return;
 627
 628         /*
 629          * Size includes space for nested attributes
 630          */
 631         size = taskstats_packet_size();
 632
 633         is_thread_group = !!taskstats_tgid_alloc(tsk);
 634         if (is_thread_group) {
 635                 /* PID + STATS + TGID + STATS */
 636                 size = 2 * size;
 637                 /* fill the tsk->signal->stats structure */
 638                 fill_tgid_exit(tsk);
 639         }
 640
 641         listeners = raw_cpu_ptr(&listener_array);
 642         if (list_empty(&listeners->list))
 643                 return;
 644
 645         rc = prepare_reply(NULL, TASKSTATS_CMD_NEW, &rep_skb, size);
 646         if (rc < 0)
 647                 return;
 648
 649         stats = mk_reply(rep_skb, TASKSTATS_TYPE_PID,
 650                          task_pid_nr_ns(tsk, &init_pid_ns));
 651         if (!stats)
 652                 goto err;
 653
 654         fill_stats(&init_user_ns, &init_pid_ns, tsk, stats);
 655
 656         /*
 657          * Doesn't matter if tsk is the leader or the last group member leaving
 658          */
 659         if (!is_thread_group || !group_dead)
 660                 goto send;
 661
 662         stats = mk_reply(rep_skb, TASKSTATS_TYPE_TGID,
 663                          task_tgid_nr_ns(tsk, &init_pid_ns));
 664         if (!stats)
 665                 goto err;
 666
 667         memcpy(stats, tsk->signal->stats, sizeof(*stats));
 668
 669 send:
 670         send_cpu_listeners(rep_skb, listeners);
 671         return;
 672 err:
 673         nlmsg_free(rep_skb);
 674 }
 675
 676 static const struct genl_ops taskstats_ops[] = {
 677         {
 678                 .cmd            = TASKSTATS_CMD_GET,
 679                 .doit           = taskstats_user_cmd,
 680                 .policy         = taskstats_cmd_get_policy,
 681                 .flags          = GENL_ADMIN_PERM,
 682         },
 683         {
 684                 .cmd            = CGROUPSTATS_CMD_GET,
 685                 .doit           = cgroupstats_user_cmd,
 686                 .policy         = cgroupstats_cmd_get_policy,
 687         },
 688 };
 689
 690 /* Needed early in initialization */
 691 void __init taskstats_init_early(void)
 692 {
 693         unsigned int i;
 694
 695         taskstats_cache = KMEM_CACHE(taskstats, SLAB_PANIC);
 696         for_each_possible_cpu(i) {
 697                 INIT_LIST_HEAD(&(per_cpu(listener_array, i).list));
 698                 init_rwsem(&(per_cpu(listener_array, i).sem));
 699         }
 700 }
 701
 702 static int __init taskstats_init(void)
 703 {
 704         int rc;
 705
 706         rc = genl_register_family_with_ops(&family, taskstats_ops);
 707         if (rc)
 708                 return rc;
 709
 710         family_registered = 1;
 711         pr_info("registered taskstats version %d\n", TASKSTATS_GENL_VERSION);
 712         return 0;
 713 }
 714
 715 /*
 716  * late initcall ensures initialization of statistics collection
 717  * mechanisms precedes initialization of the taskstats interface
 718  */
 719 late_initcall(taskstats_init);