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  *      Nadia Yvette Chambers, Oracle, July 2004
  12  *  Amortized hit count accounting via per-cpu open-addressed hashtables
  13  *      to resolve timer interrupt livelocks, Nadia Yvette Chambers,
  14  *      Oracle, 2004
  15  */
  16
  17 #include <linux/export.h>
  18 #include <linux/profile.h>
  19 #include <linux/bootmem.h>
  20 #include <linux/notifier.h>
  21 #include <linux/mm.h>
  22 #include <linux/cpumask.h>
  23 #include <linux/cpu.h>
  24 #include <linux/highmem.h>
  25 #include <linux/mutex.h>
  26 #include <linux/slab.h>
  27 #include <linux/vmalloc.h>
  28 #include <asm/sections.h>
  29 #include <asm/irq_regs.h>
  30 #include <asm/ptrace.h>
  31
  32 struct profile_hit {
  33         u32 pc, hits;
  34 };
  35 #define PROFILE_GRPSHIFT        3
  36 #define PROFILE_GRPSZ           (1 << PROFILE_GRPSHIFT)
  37 #define NR_PROFILE_HIT          (PAGE_SIZE/sizeof(struct profile_hit))
  38 #define NR_PROFILE_GRP          (NR_PROFILE_HIT/PROFILE_GRPSZ)
  39
  40 /* Oprofile timer tick hook */
  41 static int (*timer_hook)(struct pt_regs *) __read_mostly;
  42
  43 static atomic_t *prof_buffer;
  44 static unsigned long prof_len, prof_shift;
  45
  46 int prof_on __read_mostly;
  47 EXPORT_SYMBOL_GPL(prof_on);
  48
  49 static cpumask_var_t prof_cpu_mask;
  50 #ifdef CONFIG_SMP
  51 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
  52 static DEFINE_PER_CPU(int, cpu_profile_flip);
  53 static DEFINE_MUTEX(profile_flip_mutex);
  54 #endif /* CONFIG_SMP */
  55
  56 int profile_setup(char *str)
  57 {
  58         static char schedstr[] = "schedule";
  59         static char sleepstr[] = "sleep";
  60         static char kvmstr[] = "kvm";
  61         int par;
  62
  63         if (!strncmp(str, sleepstr, strlen(sleepstr))) {
  64 #ifdef CONFIG_SCHEDSTATS
  65                 prof_on = SLEEP_PROFILING;
  66                 if (str[strlen(sleepstr)] == ',')
  67                         str += strlen(sleepstr) + 1;
  68                 if (get_option(&str, &par))
  69                         prof_shift = par;
  70                 printk(KERN_INFO
  71                         "kernel sleep profiling enabled (shift: %ld)\n",
  72                         prof_shift);
  73 #else
  74                 printk(KERN_WARNING
  75                         "kernel sleep profiling requires CONFIG_SCHEDSTATS\n");
  76 #endif /* CONFIG_SCHEDSTATS */
  77         } else if (!strncmp(str, schedstr, strlen(schedstr))) {
  78                 prof_on = SCHED_PROFILING;
  79                 if (str[strlen(schedstr)] == ',')
  80                         str += strlen(schedstr) + 1;
  81                 if (get_option(&str, &par))
  82                         prof_shift = par;
  83                 printk(KERN_INFO
  84                         "kernel schedule profiling enabled (shift: %ld)\n",
  85                         prof_shift);
  86         } else if (!strncmp(str, kvmstr, strlen(kvmstr))) {
  87                 prof_on = KVM_PROFILING;
  88                 if (str[strlen(kvmstr)] == ',')
  89                         str += strlen(kvmstr) + 1;
  90                 if (get_option(&str, &par))
  91                         prof_shift = par;
  92                 printk(KERN_INFO
  93                         "kernel KVM profiling enabled (shift: %ld)\n",
  94                         prof_shift);
  95         } else if (get_option(&str, &par)) {
  96                 prof_shift = par;
  97                 prof_on = CPU_PROFILING;
  98                 printk(KERN_INFO "kernel profiling enabled (shift: %ld)\n",
  99                         prof_shift);
 100         }
 101         return 1;
 102 }
 103 __setup("profile=", profile_setup);
 104
 105
 106 int __ref profile_init(void)
 107 {
 108         int buffer_bytes;
 109         if (!prof_on)
 110                 return 0;
 111
 112         /* only text is profiled */
 113         prof_len = (_etext - _stext) >> prof_shift;
 114         buffer_bytes = prof_len*sizeof(atomic_t);
 115
 116         if (!alloc_cpumask_var(&prof_cpu_mask, GFP_KERNEL))
 117                 return -ENOMEM;
 118
 119         cpumask_copy(prof_cpu_mask, cpu_possible_mask);
 120
 121         prof_buffer = kzalloc(buffer_bytes, GFP_KERNEL|__GFP_NOWARN);
 122         if (prof_buffer)
 123                 return 0;
 124
 125         prof_buffer = alloc_pages_exact(buffer_bytes,
 126                                         GFP_KERNEL|__GFP_ZERO|__GFP_NOWARN);
 127         if (prof_buffer)
 128                 return 0;
 129
 130         prof_buffer = vzalloc(buffer_bytes);
 131         if (prof_buffer)
 132                 return 0;
 133
 134         free_cpumask_var(prof_cpu_mask);
 135         return -ENOMEM;
 136 }
 137
 138 /* Profile event notifications */
 139
 140 static BLOCKING_NOTIFIER_HEAD(task_exit_notifier);
 141 static ATOMIC_NOTIFIER_HEAD(task_free_notifier);
 142 static BLOCKING_NOTIFIER_HEAD(munmap_notifier);
 143
 144 void profile_task_exit(struct task_struct *task)
 145 {
 146         blocking_notifier_call_chain(&task_exit_notifier, 0, task);
 147 }
 148
 149 int profile_handoff_task(struct task_struct *task)
 150 {
 151         int ret;
 152         ret = atomic_notifier_call_chain(&task_free_notifier, 0, task);
 153         return (ret == NOTIFY_OK) ? 1 : 0;
 154 }
 155
 156 void profile_munmap(unsigned long addr)
 157 {
 158         blocking_notifier_call_chain(&munmap_notifier, 0, (void *)addr);
 159 }
 160
 161 int task_handoff_register(struct notifier_block *n)
 162 {
 163         return atomic_notifier_chain_register(&task_free_notifier, n);
 164 }
 165 EXPORT_SYMBOL_GPL(task_handoff_register);
 166
 167 int task_handoff_unregister(struct notifier_block *n)
 168 {
 169         return atomic_notifier_chain_unregister(&task_free_notifier, n);
 170 }
 171 EXPORT_SYMBOL_GPL(task_handoff_unregister);
 172
 173 int profile_event_register(enum profile_type type, struct notifier_block *n)
 174 {
 175         int err = -EINVAL;
 176
 177         switch (type) {
 178         case PROFILE_TASK_EXIT:
 179                 err = blocking_notifier_chain_register(
 180                                 &task_exit_notifier, n);
 181                 break;
 182         case PROFILE_MUNMAP:
 183                 err = blocking_notifier_chain_register(
 184                                 &munmap_notifier, n);
 185                 break;
 186         }
 187
 188         return err;
 189 }
 190 EXPORT_SYMBOL_GPL(profile_event_register);
 191
 192 int profile_event_unregister(enum profile_type type, struct notifier_block *n)
 193 {
 194         int err = -EINVAL;
 195
 196         switch (type) {
 197         case PROFILE_TASK_EXIT:
 198                 err = blocking_notifier_chain_unregister(
 199                                 &task_exit_notifier, n);
 200                 break;
 201         case PROFILE_MUNMAP:
 202                 err = blocking_notifier_chain_unregister(
 203                                 &munmap_notifier, n);
 204                 break;
 205         }
 206
 207         return err;
 208 }
 209 EXPORT_SYMBOL_GPL(profile_event_unregister);
 210
 211 int register_timer_hook(int (*hook)(struct pt_regs *))
 212 {
 213         if (timer_hook)
 214                 return -EBUSY;
 215         timer_hook = hook;
 216         return 0;
 217 }
 218 EXPORT_SYMBOL_GPL(register_timer_hook);
 219
 220 void unregister_timer_hook(int (*hook)(struct pt_regs *))
 221 {
 222         WARN_ON(hook != timer_hook);
 223         timer_hook = NULL;
 224         /* make sure all CPUs see the NULL hook */
 225         synchronize_sched();  /* Allow ongoing interrupts to complete. */
 226 }
 227 EXPORT_SYMBOL_GPL(unregister_timer_hook);
 228
 229
 230 #ifdef CONFIG_SMP
 231 /*
 232  * Each cpu has a pair of open-addressed hashtables for pending
 233  * profile hits. read_profile() IPI's all cpus to request them
 234  * to flip buffers and flushes their contents to prof_buffer itself.
 235  * Flip requests are serialized by the profile_flip_mutex. The sole
 236  * use of having a second hashtable is for avoiding cacheline
 237  * contention that would otherwise happen during flushes of pending
 238  * profile hits required for the accuracy of reported profile hits
 239  * and so resurrect the interrupt livelock issue.
 240  *
 241  * The open-addressed hashtables are indexed by profile buffer slot
 242  * and hold the number of pending hits to that profile buffer slot on
 243  * a cpu in an entry. When the hashtable overflows, all pending hits
 244  * are accounted to their corresponding profile buffer slots with
 245  * atomic_add() and the hashtable emptied. As numerous pending hits
 246  * may be accounted to a profile buffer slot in a hashtable entry,
 247  * this amortizes a number of atomic profile buffer increments likely
 248  * to be far larger than the number of entries in the hashtable,
 249  * particularly given that the number of distinct profile buffer
 250  * positions to which hits are accounted during short intervals (e.g.
 251  * several seconds) is usually very small. Exclusion from buffer
 252  * flipping is provided by interrupt disablement (note that for
 253  * SCHED_PROFILING or SLEEP_PROFILING profile_hit() may be called from
 254  * process context).
 255  * The hash function is meant to be lightweight as opposed to strong,
 256  * and was vaguely inspired by ppc64 firmware-supported inverted
 257  * pagetable hash functions, but uses a full hashtable full of finite
 258  * collision chains, not just pairs of them.
 259  *
 260  * -- nyc
 261  */
 262 static void __profile_flip_buffers(void *unused)
 263 {
 264         int cpu = smp_processor_id();
 265
 266         per_cpu(cpu_profile_flip, cpu) = !per_cpu(cpu_profile_flip, cpu);
 267 }
 268
 269 static void profile_flip_buffers(void)
 270 {
 271         int i, j, cpu;
 272
 273         mutex_lock(&profile_flip_mutex);
 274         j = per_cpu(cpu_profile_flip, get_cpu());
 275         put_cpu();
 276         on_each_cpu(__profile_flip_buffers, NULL, 1);
 277         for_each_online_cpu(cpu) {
 278                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[j];
 279                 for (i = 0; i < NR_PROFILE_HIT; ++i) {
 280                         if (!hits[i].hits) {
 281                                 if (hits[i].pc)
 282                                         hits[i].pc = 0;
 283                                 continue;
 284                         }
 285                         atomic_add(hits[i].hits, &prof_buffer[hits[i].pc]);
 286                         hits[i].hits = hits[i].pc = 0;
 287                 }
 288         }
 289         mutex_unlock(&profile_flip_mutex);
 290 }
 291
 292 static void profile_discard_flip_buffers(void)
 293 {
 294         int i, cpu;
 295
 296         mutex_lock(&profile_flip_mutex);
 297         i = per_cpu(cpu_profile_flip, get_cpu());
 298         put_cpu();
 299         on_each_cpu(__profile_flip_buffers, NULL, 1);
 300         for_each_online_cpu(cpu) {
 301                 struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
 302                 memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
 303         }
 304         mutex_unlock(&profile_flip_mutex);
 305 }
 306
 307 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 308 {
 309         unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
 310         int i, j, cpu;
 311         struct profile_hit *hits;
 312
 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_mem(cpu);
 366                 per_cpu(cpu_profile_flip, cpu) = 0;
 367                 if (!per_cpu(cpu_profile_hits, cpu)[1]) {
 368                         page = alloc_pages_exact_node(node,
 369                                         GFP_KERNEL | __GFP_ZERO,
 370                                         0);
 371                         if (!page)
 372                                 return notifier_from_errno(-ENOMEM);
 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_exact_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 notifier_from_errno(-ENOMEM);
 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 static void do_profile_hits(int type, void *__pc, unsigned int nr_hits)
 420 {
 421         unsigned long pc;
 422         pc = ((unsigned long)__pc - (unsigned long)_stext) >> prof_shift;
 423         atomic_add(nr_hits, &prof_buffer[min(pc, prof_len - 1)]);
 424 }
 425 #endif /* !CONFIG_SMP */
 426
 427 void profile_hits(int type, void *__pc, unsigned int nr_hits)
 428 {
 429         if (prof_on != type || !prof_buffer)
 430                 return;
 431         do_profile_hits(type, __pc, nr_hits);
 432 }
 433 EXPORT_SYMBOL_GPL(profile_hits);
 434
 435 void profile_tick(int type)
 436 {
 437         struct pt_regs *regs = get_irq_regs();
 438
 439         if (type == CPU_PROFILING && timer_hook)
 440                 timer_hook(regs);
 441         if (!user_mode(regs) && prof_cpu_mask != NULL &&
 442             cpumask_test_cpu(smp_processor_id(), prof_cpu_mask))
 443                 profile_hit(type, (void *)profile_pc(regs));
 444 }
 445
 446 #ifdef CONFIG_PROC_FS
 447 #include <linux/proc_fs.h>
 448 #include <linux/seq_file.h>
 449 #include <asm/uaccess.h>
 450
 451 static int prof_cpu_mask_proc_show(struct seq_file *m, void *v)
 452 {
 453         seq_cpumask(m, prof_cpu_mask);
 454         seq_putc(m, '\n');
 455         return 0;
 456 }
 457
 458 static int prof_cpu_mask_proc_open(struct inode *inode, struct file *file)
 459 {
 460         return single_open(file, prof_cpu_mask_proc_show, NULL);
 461 }
 462
 463 static ssize_t prof_cpu_mask_proc_write(struct file *file,
 464         const char __user *buffer, size_t count, loff_t *pos)
 465 {
 466         cpumask_var_t new_value;
 467         int err;
 468
 469         if (!alloc_cpumask_var(&new_value, GFP_KERNEL))
 470                 return -ENOMEM;
 471
 472         err = cpumask_parse_user(buffer, count, new_value);
 473         if (!err) {
 474                 cpumask_copy(prof_cpu_mask, new_value);
 475                 err = count;
 476         }
 477         free_cpumask_var(new_value);
 478         return err;
 479 }
 480
 481 static const struct file_operations prof_cpu_mask_proc_fops = {
 482         .open           = prof_cpu_mask_proc_open,
 483         .read           = seq_read,
 484         .llseek         = seq_lseek,
 485         .release        = single_release,
 486         .write          = prof_cpu_mask_proc_write,
 487 };
 488
 489 void create_prof_cpu_mask(struct proc_dir_entry *root_irq_dir)
 490 {
 491         /* create /proc/irq/prof_cpu_mask */
 492         proc_create("prof_cpu_mask", 0600, root_irq_dir, &prof_cpu_mask_proc_fops);
 493 }
 494
 495 /*
 496  * This function accesses profiling information. The returned data is
 497  * binary: the sampling step and the actual contents of the profile
 498  * buffer. Use of the program readprofile is recommended in order to
 499  * get meaningful info out of these data.
 500  */
 501 static ssize_t
 502 read_profile(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 503 {
 504         unsigned long p = *ppos;
 505         ssize_t read;
 506         char *pnt;
 507         unsigned int sample_step = 1 << prof_shift;
 508
 509         profile_flip_buffers();
 510         if (p >= (prof_len+1)*sizeof(unsigned int))
 511                 return 0;
 512         if (count > (prof_len+1)*sizeof(unsigned int) - p)
 513                 count = (prof_len+1)*sizeof(unsigned int) - p;
 514         read = 0;
 515
 516         while (p < sizeof(unsigned int) && count > 0) {
 517                 if (put_user(*((char *)(&sample_step)+p), buf))
 518                         return -EFAULT;
 519                 buf++; p++; count--; read++;
 520         }
 521         pnt = (char *)prof_buffer + p - sizeof(atomic_t);
 522         if (copy_to_user(buf, (void *)pnt, count))
 523                 return -EFAULT;
 524         read += count;
 525         *ppos += read;
 526         return read;
 527 }
 528
 529 /*
 530  * Writing to /proc/profile resets the counters
 531  *
 532  * Writing a 'profiling multiplier' value into it also re-sets the profiling
 533  * interrupt frequency, on architectures that support this.
 534  */
 535 static ssize_t write_profile(struct file *file, const char __user *buf,
 536                              size_t count, loff_t *ppos)
 537 {
 538 #ifdef CONFIG_SMP
 539         extern int setup_profiling_timer(unsigned int multiplier);
 540
 541         if (count == sizeof(int)) {
 542                 unsigned int multiplier;
 543
 544                 if (copy_from_user(&multiplier, buf, sizeof(int)))
 545                         return -EFAULT;
 546
 547                 if (setup_profiling_timer(multiplier))
 548                         return -EINVAL;
 549         }
 550 #endif
 551         profile_discard_flip_buffers();
 552         memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 553         return count;
 554 }
 555
 556 static const struct file_operations proc_profile_operations = {
 557         .read           = read_profile,
 558         .write          = write_profile,
 559         .llseek         = default_llseek,
 560 };
 561
 562 #ifdef CONFIG_SMP
 563 static void profile_nop(void *unused)
 564 {
 565 }
 566
 567 static int create_hash_tables(void)
 568 {
 569         int cpu;
 570
 571         for_each_online_cpu(cpu) {
 572                 int node = cpu_to_mem(cpu);
 573                 struct page *page;
 574
 575                 page = alloc_pages_exact_node(node,
 576                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 577                                 0);
 578                 if (!page)
 579                         goto out_cleanup;
 580                 per_cpu(cpu_profile_hits, cpu)[1]
 581                                 = (struct profile_hit *)page_address(page);
 582                 page = alloc_pages_exact_node(node,
 583                                 GFP_KERNEL | __GFP_ZERO | GFP_THISNODE,
 584                                 0);
 585                 if (!page)
 586                         goto out_cleanup;
 587                 per_cpu(cpu_profile_hits, cpu)[0]
 588                                 = (struct profile_hit *)page_address(page);
 589         }
 590         return 0;
 591 out_cleanup:
 592         prof_on = 0;
 593         smp_mb();
 594         on_each_cpu(profile_nop, NULL, 1);
 595         for_each_online_cpu(cpu) {
 596                 struct page *page;
 597
 598                 if (per_cpu(cpu_profile_hits, cpu)[0]) {
 599                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[0]);
 600                         per_cpu(cpu_profile_hits, cpu)[0] = NULL;
 601                         __free_page(page);
 602                 }
 603                 if (per_cpu(cpu_profile_hits, cpu)[1]) {
 604                         page = virt_to_page(per_cpu(cpu_profile_hits, cpu)[1]);
 605                         per_cpu(cpu_profile_hits, cpu)[1] = NULL;
 606                         __free_page(page);
 607                 }
 608         }
 609         return -1;
 610 }
 611 #else
 612 #define create_hash_tables()                    ({ 0; })
 613 #endif
 614
 615 int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
 616 {
 617         struct proc_dir_entry *entry;
 618
 619         if (!prof_on)
 620                 return 0;
 621         if (create_hash_tables())
 622                 return -ENOMEM;
 623         entry = proc_create("profile", S_IWUSR | S_IRUGO,
 624                             NULL, &proc_profile_operations);
 625         if (!entry)
 626                 return 0;
 627         entry->size = (1+prof_len) * sizeof(atomic_t);
 628         hotcpu_notifier(profile_cpu_callback, 0);
 629         return 0;
 630 }
 631 module_init(create_proc_profile);
 632 #endif /* CONFIG_PROC_FS */