kernel/profile.c

   1 /*
   2  *  linux/kernel/profile.c
   3  *  Simple profiling. Manages a direct-mapped profile hit count buffer,
   4  *  with configurable resolution, support for restricting the cpus on
   5  *  which profiling is done, and switching between cpu time and
   6  *  schedule() calls via kernel command line parameters passed at boot.
   7  *
   8  *  Scheduler profiling support, Arjan van de Ven and Ingo Molnar,
   9  *      Red Hat, July 2004
  10  *  Consolidation of architecture support code for profiling,
  11  *      William Irwin, Oracle, July 2004
  12  *  Amortized hit count accounting via per-cpu open-addressed hashtables
  13  *      to resolve timer interrupt livelocks, William Irwin, Oracle, 2004
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/profile.h>
  18 #include <linux/bootmem.h>
  19 #include <linux/notifier.h>
  20 #include <linux/mm.h>
  21 #include <linux/cpumask.h>
  22 #include <linux/cpu.h>
  23 #include <linux/highmem.h>
  24 #include <linux/mutex.h>
  25 #include <linux/slab.h>
  26 #include <linux/vmalloc.h>
  27 #include <asm/sections.h>
  28 #include <asm/irq_regs.h>
  29 #include <asm/ptrace.h>
  30
  31 struct profile_hit {
  32         u32 pc, hits;
  33 };
  34 #define PROFILE_GRPSHIFT        3
  35 #define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
  36 #define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
  37 #define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
  38
  39 /* Oprofile timer tick hook */
  40 static int (*timer_hook)(struct pt_regs *) __read_mostly;
  41
  42 static atomic_t *prof_buffer;
  43 static unsigned long prof_len, prof_shift;
  44
  45 int prof_on __read_mostly;
  46 EXPORT_SYMBOL_GPL(prof_on);
  47
  48 static cpumask_var_t prof_cpu_mask;
  49 #ifdef CONFIG_SMP
  50 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
  51 static DEFINE_PER_CPU(int, cpu_profile_flip);
  52 static DEFINE_MUTEX(profile_flip_mutex);
  53 #endif /* CONFIG_SMP */
  54
  55 int profile_setup(char *str)
  56 {
  57         static char schedstr[] = "schedule";
  58         static char sleepstr[] = "sleep";
  59         static char kvmstr[] = "kvm";
  60         int par;
  61
  62         if (!strncmp(str, sleepstr, strlen(sleepstr))) {
  63 #ifdef CONFIG_SCHEDSTATS
  64                 prof_on = SLEEP_PROFILING;
  65                 if (str[strlen(sleepstr)] == ',')
  66                         str += strlen(sleepstr) + 1;
  67                 if (get_option(&str, &par))
  68                         prof_shift = par;
  69                 printk(KERN_INFO
  70                         "kernel sleep profiling enabled (shift: %ld)\n",
  71                         prof_shift);
  72 #else
  73                 printk(KERN_WARNING
  74                         "kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
  75 #endif /* CONFIG_SCHEDSTATS */
  76         } else if (!strncmp(str, schedstr, strlen(schedstr))) {
  77                 prof_on = SCHED_PROFILING;
  78                 if (str[strlen(schedstr)] == ',')
  79                         str += strlen(schedstr) + 1;
  80                 if (get_option(&str, &par))
  81                         prof_shift = par;
  82                 printk(KERN_INFO
  83                         "kernel schedule profiling enabled (shift: %ld)\n",
  84                         prof_shift);
  85         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  86                 prof_on = KVM_PROFILING;
  87                 if (str[strlen(kvmstr)] == ',')
  88                         str += strlen(kvmstr) + 1;
  89                 if (get_option(&str, &par))
  90                         prof_shift = par;
  91                 printk(KERN_INFO
  92                         "kernel KVM profiling enabled (shift: %ld)\n",
  93                         prof_shift);
  94         } else if (get_option(&str, &par)) {
  95                 prof_shift = par;
  96                 prof_on = CPU_PROFILING;
  97                 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
  98                         prof_shift);
  99         }
 100         return 1;
 101 }
 102 __setup("profile=", profile_setup);
 103
 104
 105 int __ref profile_init(void)
 106 {
 107         int buffer_bytes;
 108         if (!prof_on)
 109                 return 0;
 110
 111         /* only text is profiled */
 112         prof_len = (_etext - _stext) >> prof_shift;
 113         buffer_bytes = prof_len*sizeof(atomic_t);
 114
 115         if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
 116                 return -ENOMEM;
 117
 118         cpumask_copy(prof_cpu_mask, cpu_possible_mask);
 119
 120         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL);
 121         if (prof_buffer)
 122                 return 0;
 123
 124         prof_buffer = alloc_pages_exact(buffer_bytes, GFP_KERNEL|__GFP_ZERO);
 125         if (prof_buffer)
 126                 return 0;
 127
 128         prof_buffer = vmalloc(buffer_bytes);
 129         if (prof_buffer)
 130                 return 0;
 131
 132         free_cpumask_var(prof_cpu_mask);
 133         return -ENOMEM;
 134 }
 135
 136 /* Profile event notifications */
 137
 138 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 139 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 140 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 141
 142 void profile_task_exit(struct task_struct *task)
 143 {
 144         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 145 }
 146
 147 int profile_handoff_task(struct task_struct *task)
 148 {
 149         int ret;
 150         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 151         return (ret == NOTIFY_OK) ? 1 : 0;
 152 }
 153
 154 void profile_munmap(unsigned long addr)
 155 {
 156         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 157 }
 158
 159 int task_handoff_register(struct notifier_block *n)
 160 {
 161         return atomic_notifier_chain_register(&task_free_notifier, n);
 162 }
 163 EXPORT_SYMBOL_GPL(task_handoff_register);
 164
 165 int task_handoff_unregister(struct notifier_block *n)
 166 {
 167         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 168 }
 169 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 170
 171 int profile_event_register(enum profile_type type, struct notifier_block *n)
 172 {
 173         int err = -EINVAL;
 174
 175         switch (type) {
 176         case PROFILE_TASK_EXIT:
 177                 err = blocking_notifier_chain_register(
 178                                 &task_exit_notifier, n);
 179                 break;
 180         case PROFILE_MUNMAP:
 181                 err = blocking_notifier_chain_register(
 182                                 &munmap_notifier, n);
 183                 break;
 184         }
 185
 186         return err;
 187 }
 188 EXPORT_SYMBOL_GPL(profile_event_register);
 189
 190 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 191 {
 192         int err = -EINVAL;
 193
 194         switch (type) {
 195         case PROFILE_TASK_EXIT:
 196                 err = blocking_notifier_chain_unregister(
 197                                 &task_exit_notifier, n);
 198                 break;
 199         case PROFILE_MUNMAP:
 200                 err = blocking_notifier_chain_unregister(
 201                                 &munmap_notifier, n);
 202                 break;
 203         }
 204
 205         return err;
 206 }
 207 EXPORT_SYMBOL_GPL(profile_event_unregister);
 208
 209 int register_timer_hook(int (*hook)(struct pt_regs *))
 210 {
 211         if (timer_hook)
 212                 return -EBUSY;
 213         timer_hook = hook;
 214         return 0;
 215 }
 216 EXPORT_SYMBOL_GPL(register_timer_hook);
 217
 218 void unregister_timer_hook(int (*hook)(struct pt_regs *))
 219 {
 220         WARN_ON(hook != timer_hook);
 221         timer_hook = NULL;
 222         /* make sure all CPUs see the NULL hook */
 223         synchronize_sched();  /* Allow ongoing interrupts to complete. */
 224 }
 225 EXPORT_SYMBOL_GPL(unregister_timer_hook);
 226
 227
 228 #ifdef CONFIG_SMP
 229 /*
 230  * Each cpu has a pair of open-addressed hashtables for pending
 231  * profile hits. read_profile() IPI's all cpus to request them
 232  * to flip buffers and flushes their contents to prof_buffer itself.
 233  * Flip requests are serialized by the profile_flip_mutex. The sole
 234  * use of having a second hashtable is for avoiding cacheline
 235  * contention that would otherwise happen during flushes of pending
 236  * profile hits required for the accuracy of reported profile hits
 237  * and so resurrect the interrupt livelock issue.
 238  *
 239  * The open-addressed hashtables are indexed by profile buffer slot
 240  * and hold the number of pending hits to that profile buffer slot on
 241  * a cpu in an entry. When the hashtable overflows, all pending hits
 242  * are accounted to their corresponding profile buffer slots with
 243  * atomic_add() and the hashtable emptied. As numerous pending hits
 244  * may be accounted to a profile buffer slot in a hashtable entry,
 245  * this amortizes a number of atomic profile buffer increments likely
 246  * to be far larger than the number of entries in the hashtable,
 247  * particularly given that the number of distinct profile buffer
 248  * positions to which hits are accounted during short intervals (e.g.
 249  * several seconds) is usually very small. Exclusion from buffer
 250  * flipping is provided by interrupt disablement (note that for
 251  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 252  * process context).
 253  * The hash function is meant to be lightweight as opposed to strong,
 254  * and was vaguely inspired by ppc64 firmware-supported inverted
 255  * pagetable hash functions, but uses a full hashtable full of finite
 256  * collision chains, not just pairs of them.
 257  *
 258  * -- wli
 259  */
 260 static void __profile_flip_buffers(void *unused)
 261 {
 262         int cpu = smp_processor_id();
 263
 264         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 265 }
 266
 267 static void profile_flip_buffers(void)
 268 {
 269         int i, j, cpu;
 270
 271         mutex_lock(&profile_flip_mutex);
 272         j = per_cpu(cpu_profile_flip, get_cpu());
 273         put_cpu();
 274         on_each_cpu(__profile_flip_buffers, NULL, 1);
 275         for_each_online_cpu(cpu) {
 276                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 277                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 278                         if (!hits[i].hits) {
 279                                 if (hits[i].pc)
 280                                         hits[i].pc = 0;
 281                                 continue;
 282                         }
 283                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 284                         hits[i].hits = hits[i].pc = 0;
 285                 }
 286         }
 287         mutex_unlock(&profile_flip_mutex);
 288 }
 289
 290 static void profile_discard_flip_buffers(void)
 291 {
 292         int i, cpu;
 293
 294         mutex_lock(&profile_flip_mutex);
 295         i = per_cpu(cpu_profile_flip, get_cpu());
 296         put_cpu();
 297         on_each_cpu(__profile_flip_buffers, NULL, 1);
 298         for_each_online_cpu(cpu) {
 299                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 300                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 301         }
 302         mutex_unlock(&profile_flip_mutex);
 303 }
 304
 305 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 306 {
 307         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 308         int i, j, cpu;
 309         struct profile_hit *hits;
 310
 311         if (prof_on != type || !prof_buffer)
 312                 return;
 313         pc = min((pc - (unsigned long)_stext) >> prof_shift, prof_len - 1);
 314         i = primary = (pc & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 315         secondary = (~(pc << 1) & (NR_PROFILE_GRP - 1)) << PROFILE_GRPSHIFT;
 316         cpu = get_cpu();
 317         hits = per_cpu(cpu_profile_hits, cpu)[per_cpu(cpu_profile_flip, cpu)];
 318         if (!hits) {
 319                 put_cpu();
 320                 return;
 321         }
 322         /*
 323          * We buffer the global profiler buffer into a per-CPU
 324          * queue and thus reduce the number of global (and possibly
 325          * NUMA-alien) accesses. The write-queue is self-coalescing:
 326          */
 327         local_irq_save(flags);
 328         do {
 329                 for (j = 0; j < PROFILE_GRPSZ; ++j) {
 330                         if (hits[i + j].pc == pc) {
 331                                 hits[i + j].hits += nr_hits;
 332                                 goto out;
 333                         } else if (!hits[i + j].hits) {
 334                                 hits[i + j].pc = pc;
 335                                 hits[i + j].hits = nr_hits;
 336                                 goto out;
 337                         }
 338                 }
 339                 i = (i + secondary) & (NR_PROFILE_HIT - 1);
 340         } while (i != primary);
 341
 342         /*
 343          * Add the current hit(s) and flush the write-queue out
 344          * to the global buffer:
 345          */
 346         atomic_add(nr_hits, &prof_buffer[pc]);
 347         for (i = 0; i < NR_PROFILE_HIT; ++i) {
 348                 atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 349                 hits[i].pc = hits[i].hits = 0;
 350         }
 351 out:
 352         local_irq_restore(flags);
 353         put_cpu();
 354 }
 355
 356 static int __cpuinit profile_cpu_callback(struct notifier_block *info,
 357                                         unsigned long action, void *__cpu)
 358 {
 359         int node, cpu = (unsigned long)__cpu;
 360         struct page *page;
 361
 362         switch (action) {
 363         case CPU_UP_PREPARE:
 364         case CPU_UP_PREPARE_FROZEN:
 365                 node = cpu_to_node(cpu);
 366                 per_cpu(cpu_profile_flip, cpu) = 0;
 367                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 368                         page = alloc_pages_node(node,
 369                                         GFP_KERNEL | __GFP_ZERO,
 370                                         0);
 371                         if (!page)
 372                                 return NOTIFY_BAD;
 373                         per_cpu(cpu_profile_hits, cpu)[1] = page_address(page);
 374                 }
 375                 if (!per_cpu(cpu_profile_hits, cpu)[0]) {
 376                         page = alloc_pages_node(node,
 377                                         GFP_KERNEL | __GFP_ZERO,
 378                                         0);
 379                         if (!page)
 380                                 goto out_free;
 381                         per_cpu(cpu_profile_hits, cpu)[0] = page_address(page);
 382                 }
 383                 break;
 384 out_free:
 385                 page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 386                 per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 387                 __free_page(page);
 388                 return NOTIFY_BAD;
 389         case CPU_ONLINE:
 390         case CPU_ONLINE_FROZEN:
 391                 if (prof_cpu_mask != NULL)
 392                         cpumask_set_cpu(cpu, prof_cpu_mask);
 393                 break;
 394         case CPU_UP_CANCELED:
 395         case CPU_UP_CANCELED_FROZEN:
 396         case CPU_DEAD:
 397         case CPU_DEAD_FROZEN:
 398                 if (prof_cpu_mask != NULL)
 399                         cpumask_clear_cpu(cpu, prof_cpu_mask);
 400                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 401                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 402                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 403                         __free_page(page);
 404                 }
 405                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 406                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 407                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 408                         __free_page(page);
 409                 }
 410                 break;
 411         }
 412         return NOTIFY_OK;
 413 }
 414 #else /* !CONFIG_SMP */
 415 #define profile_flip_buffers()          do { } while (0)
 416 #define profile_discard_flip_buffers()  do { } while (0)
 417 #define profile_cpu_callback            NULL
 418
 419 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 420 {
 421         unsigned long pc;
 422
 423         if (prof_on != type || !prof_buffer)
 424                 return;
 425         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 426         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 427 }
 428 #endif /* !CONFIG_SMP */
 429 EXPORT_SYMBOL_GPL(profile_hits);
 430
 431 void profile_tick(int type)
 432 {
 433         struct pt_regs *regs = get_irq_regs();
 434
 435         if (type == CPU_PROFILING && timer_hook)
 436                 timer_hook(regs);
 437         if (!user_mode(regs) && prof_cpu_mask != NULL &&
 438             cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 439                 profile_hit(type, (void *)profile_pc(regs));
 440 }
 441
 442 #ifdef CONFIG_PROC_FS
 443 #include <linux/proc_fs.h>
 444 #include <asm/uaccess.h>
 445
 446 static int prof_cpu_mask_read_proc(char *page, char **start, off_t off,
 447                         int count, int *eof, void *data)
 448 {
 449         int len = cpumask_scnprintf(page, count, data);
 450         if (count - len < 2)
 451                 return -EINVAL;
 452         len += sprintf(page + len, "\n");
 453         return len;
 454 }
 455
 456 static int prof_cpu_mask_write_proc(struct file *file,
 457         const char __user *buffer,  unsigned long count, void *data)
 458 {
 459         struct cpumask *mask = data;
 460         unsigned long full_count = count, err;
 461         cpumask_var_t new_value;
 462
 463         if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
 464                 return -ENOMEM;
 465
 466         err = cpumask_parse_user(buffer, count, new_value);
 467         if (!err) {
 468                 cpumask_copy(mask, new_value);
 469                 err = full_count;
 470         }
 471         free_cpumask_var(new_value);
 472         return err;
 473 }
 474
 475 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
 476 {
 477         struct proc_dir_entry *entry;
 478
 479         /* create /proc/irq/prof_cpu_mask */
 480         entry = create_proc_entry("prof_cpu_mask", 0600, root_irq_dir);
 481         if (!entry)
 482                 return;
 483         entry->data = prof_cpu_mask;
 484         entry->read_proc = prof_cpu_mask_read_proc;
 485         entry->write_proc = prof_cpu_mask_write_proc;
 486 }
 487
 488 /*
 489  * This function accesses profiling information. The returned data is
 490  * binary: the sampling step and the actual contents of the profile
 491  * buffer. Use of the program readprofile is recommended in order to
 492  * get meaningful info out of these data.
 493  */
 494 static ssize_t
 495 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 496 {
 497         unsigned long p = *ppos;
 498         ssize_t read;
 499         char *pnt;
 500         unsigned int sample_step = 1 << prof_shift;
 501
 502         profile_flip_buffers();
 503         if (p >= (prof_len+1)*sizeof(unsigned int))
 504                 return 0;
 505         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 506                 count = (prof_len+1)*sizeof(unsigned int) - p;
 507         read = 0;
 508
 509         while (p < sizeof(unsigned int) && count > 0) {
 510                 if (put_user(*((char *)(&sample_step)+p), buf))
 511                         return -EFAULT;
 512                 buf++; p++; count--; read++;
 513         }
 514         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 515         if (copy_to_user(buf, (void *)pnt, count))
 516                 return -EFAULT;
 517         read += count;
 518         *ppos += read;
 519         return read;
 520 }
 521
 522 /*
 523  * Writing to /proc/profile resets the counters
 524  *
 525  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 526  * interrupt frequency, on architectures that support this.
 527  */
 528 static ssize_t write_profile(struct file *file, const char __user *buf,
 529                              size_t count, loff_t *ppos)
 530 {
 531 #ifdef CONFIG_SMP
 532         extern int setup_profiling_timer(unsigned int multiplier);
 533
 534         if (count == sizeof(int)) {
 535                 unsigned int multiplier;
 536
 537                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 538                         return -EFAULT;
 539
 540                 if (setup_profiling_timer(multiplier))
 541                         return -EINVAL;
 542         }
 543 #endif
 544         profile_discard_flip_buffers();
 545         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 546         return count;
 547 }
 548
 549 static const struct file_operations proc_profile_operations = {
 550         .read           = read_profile,
 551         .write          = write_profile,
 552 };
 553
 554 #ifdef CONFIG_SMP
 555 static void profile_nop(void *unused)
 556 {
 557 }
 558
 559 static int create_hash_tables(void)
 560 {
 561         int cpu;
 562
 563         for_each_online_cpu(cpu) {
 564                 int node = cpu_to_node(cpu);
 565                 struct page *page;
 566
 567                 page = alloc_pages_node(node,
 568                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 569                                 0);
 570                 if (!page)
 571                         goto out_cleanup;
 572                 per_cpu(cpu_profile_hits, cpu)[1]
 573                                 = (struct profile_hit *)page_address(page);
 574                 page = alloc_pages_node(node,
 575                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 576                                 0);
 577                 if (!page)
 578                         goto out_cleanup;
 579                 per_cpu(cpu_profile_hits, cpu)[0]
 580                                 = (struct profile_hit *)page_address(page);
 581         }
 582         return 0;
 583 out_cleanup:
 584         prof_on = 0;
 585         smp_mb();
 586         on_each_cpu(profile_nop, NULL, 1);
 587         for_each_online_cpu(cpu) {
 588                 struct page *page;
 589
 590                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 591                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 592                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 593                         __free_page(page);
 594                 }
 595                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 596                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 597                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 598                         __free_page(page);
 599                 }
 600         }
 601         return -1;
 602 }
 603 #else
 604 #define create_hash_tables()                    ({ 0; })
 605 #endif
 606
 607 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
 608 {
 609         struct proc_dir_entry *entry;
 610
 611         if (!prof_on)
 612                 return 0;
 613         if (create_hash_tables())
 614                 return -ENOMEM;
 615         entry = proc_create("profile", S_IWUSR | S_IRUGO,
 616                             NULL, &proc_profile_operations);
 617         if (!entry)
 618                 return 0;
 619         entry->size = (1+prof_len) * sizeof(atomic_t);
 620         hotcpu_notifier(profile_cpu_callback, 0);
 621         return 0;
 622 }
 623 module_init(create_proc_profile);
 624 #endif /* CONFIG_PROC_FS */