kernel/cpu.c

   1 /* CPU control.
   2  * (C) 2001, 2002, 2003, 2004 Rusty Russell
   3  *
   4  * This code is licenced under the GPL.
   5  */
   6 #include <linux/proc_fs.h>
   7 #include <linux/smp.h>
   8 #include <linux/init.h>
   9 #include <linux/notifier.h>
  10 #include <linux/sched.h>
  11 #include <linux/unistd.h>
  12 #include <linux/cpu.h>
  13 #include <linux/module.h>
  14 #include <linux/kthread.h>
  15 #include <linux/stop_machine.h>
  16 #include <linux/mutex.h>
  17 #include <linux/gfp.h>
  18
  19 #ifdef CONFIG_SMP
  20 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
  21 static DEFINE_MUTEX(cpu_add_remove_lock);
  22
  23 /*
  24  * The following two API's must be used when attempting
  25  * to serialize the updates to cpu_online_mask, cpu_present_mask.
  26  */
  27 void cpu_maps_update_begin(void)
  28 {
  29         mutex_lock(&cpu_add_remove_lock);
  30 }
  31
  32 void cpu_maps_update_done(void)
  33 {
  34         mutex_unlock(&cpu_add_remove_lock);
  35 }
  36
  37 static RAW_NOTIFIER_HEAD(cpu_chain);
  38
  39 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
  40  * Should always be manipulated under cpu_add_remove_lock
  41  */
  42 static int cpu_hotplug_disabled;
  43
  44 #ifdef CONFIG_HOTPLUG_CPU
  45
  46 static struct {
  47         struct task_struct *active_writer;
  48         struct mutex lock; /* Synchronizes accesses to refcount, */
  49         /*
  50          * Also blocks the new readers during
  51          * an ongoing cpu hotplug operation.
  52          */
  53         int refcount;
  54 } cpu_hotplug = {
  55         .active_writer = NULL,
  56         .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
  57         .refcount = 0,
  58 };
  59
  60 void get_online_cpus(void)
  61 {
  62         might_sleep();
  63         if (cpu_hotplug.active_writer == current)
  64                 return;
  65         mutex_lock(&cpu_hotplug.lock);
  66         cpu_hotplug.refcount++;
  67         mutex_unlock(&cpu_hotplug.lock);
  68
  69 }
  70 EXPORT_SYMBOL_GPL(get_online_cpus);
  71
  72 void put_online_cpus(void)
  73 {
  74         if (cpu_hotplug.active_writer == current)
  75                 return;
  76         mutex_lock(&cpu_hotplug.lock);
  77         if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
  78                 wake_up_process(cpu_hotplug.active_writer);
  79         mutex_unlock(&cpu_hotplug.lock);
  80
  81 }
  82 EXPORT_SYMBOL_GPL(put_online_cpus);
  83
  84 /*
  85  * This ensures that the hotplug operation can begin only when the
  86  * refcount goes to zero.
  87  *
  88  * Note that during a cpu-hotplug operation, the new readers, if any,
  89  * will be blocked by the cpu_hotplug.lock
  90  *
  91  * Since cpu_hotplug_begin() is always called after invoking
  92  * cpu_maps_update_begin(), we can be sure that only one writer is active.
  93  *
  94  * Note that theoretically, there is a possibility of a livelock:
  95  * - Refcount goes to zero, last reader wakes up the sleeping
  96  *   writer.
  97  * - Last reader unlocks the cpu_hotplug.lock.
  98  * - A new reader arrives at this moment, bumps up the refcount.
  99  * - The writer acquires the cpu_hotplug.lock finds the refcount
 100  *   non zero and goes to sleep again.
 101  *
 102  * However, this is very difficult to achieve in practice since
 103  * get_online_cpus() not an api which is called all that often.
 104  *
 105  */
 106 static void cpu_hotplug_begin(void)
 107 {
 108         cpu_hotplug.active_writer = current;
 109
 110         for (;;) {
 111                 mutex_lock(&cpu_hotplug.lock);
 112                 if (likely(!cpu_hotplug.refcount))
 113                         break;
 114                 __set_current_state(TASK_UNINTERRUPTIBLE);
 115                 mutex_unlock(&cpu_hotplug.lock);
 116                 schedule();
 117         }
 118 }
 119
 120 static void cpu_hotplug_done(void)
 121 {
 122         cpu_hotplug.active_writer = NULL;
 123         mutex_unlock(&cpu_hotplug.lock);
 124 }
 125
 126 #else /* #if CONFIG_HOTPLUG_CPU */
 127 static void cpu_hotplug_begin(void) {}
 128 static void cpu_hotplug_done(void) {}
 129 #endif  /* #else #if CONFIG_HOTPLUG_CPU */
 130
 131 /* Need to know about CPUs going up/down? */
 132 int __ref register_cpu_notifier(struct notifier_block *nb)
 133 {
 134         int ret;
 135         cpu_maps_update_begin();
 136         ret = raw_notifier_chain_register(&cpu_chain, nb);
 137         cpu_maps_update_done();
 138         return ret;
 139 }
 140
 141 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
 142                         int *nr_calls)
 143 {
 144         int ret;
 145
 146         ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
 147                                         nr_calls);
 148
 149         return notifier_to_errno(ret);
 150 }
 151
 152 static int cpu_notify(unsigned long val, void *v)
 153 {
 154         return __cpu_notify(val, v, -1, NULL);
 155 }
 156
 157 #ifdef CONFIG_HOTPLUG_CPU
 158
 159 static void cpu_notify_nofail(unsigned long val, void *v)
 160 {
 161         BUG_ON(cpu_notify(val, v));
 162 }
 163 EXPORT_SYMBOL(register_cpu_notifier);
 164
 165 void __ref unregister_cpu_notifier(struct notifier_block *nb)
 166 {
 167         cpu_maps_update_begin();
 168         raw_notifier_chain_unregister(&cpu_chain, nb);
 169         cpu_maps_update_done();
 170 }
 171 EXPORT_SYMBOL(unregister_cpu_notifier);
 172
 173 static inline void check_for_tasks(int cpu)
 174 {
 175         struct task_struct *p;
 176
 177         write_lock_irq(&tasklist_lock);
 178         for_each_process(p) {
 179                 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
 180                     (!cputime_eq(p->utime, cputime_zero) ||
 181                      !cputime_eq(p->stime, cputime_zero)))
 182                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
 183                                 "(state = %ld, flags = %x)\n",
 184                                 p->comm, task_pid_nr(p), cpu,
 185                                 p->state, p->flags);
 186         }
 187         write_unlock_irq(&tasklist_lock);
 188 }
 189
 190 struct take_cpu_down_param {
 191         unsigned long mod;
 192         void *hcpu;
 193 };
 194
 195 /* Take this CPU down. */
 196 static int __ref take_cpu_down(void *_param)
 197 {
 198         struct take_cpu_down_param *param = _param;
 199         int err;
 200
 201         /* Ensure this CPU doesn't handle any more interrupts. */
 202         err = __cpu_disable();
 203         if (err < 0)
 204                 return err;
 205
 206         cpu_notify(CPU_DYING | param->mod, param->hcpu);
 207         return 0;
 208 }
 209
 210 /* Requires cpu_add_remove_lock to be held */
 211 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 212 {
 213         int err, nr_calls = 0;
 214         void *hcpu = (void *)(long)cpu;
 215         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 216         struct take_cpu_down_param tcd_param = {
 217                 .mod = mod,
 218                 .hcpu = hcpu,
 219         };
 220
 221         if (num_online_cpus() == 1)
 222                 return -EBUSY;
 223
 224         if (!cpu_online(cpu))
 225                 return -EINVAL;
 226
 227         cpu_hotplug_begin();
 228
 229         err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
 230         if (err) {
 231                 nr_calls--;
 232                 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
 233                 printk("%s: attempt to take down CPU %u failed\n",
 234                                 __func__, cpu);
 235                 goto out_release;
 236         }
 237
 238         err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
 239         if (err) {
 240                 /* CPU didn't die: tell everyone.  Can't complain. */
 241                 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
 242
 243                 goto out_release;
 244         }
 245         BUG_ON(cpu_online(cpu));
 246
 247         /*
 248          * The migration_call() CPU_DYING callback will have removed all
 249          * runnable tasks from the cpu, there's only the idle task left now
 250          * that the migration thread is done doing the stop_machine thing.
 251          *
 252          * Wait for the stop thread to go away.
 253          */
 254         while (!idle_cpu(cpu))
 255                 cpu_relax();
 256
 257         /* This actually kills the CPU. */
 258         __cpu_die(cpu);
 259
 260         /* CPU is completely dead: tell everyone.  Too late to complain. */
 261         cpu_notify_nofail(CPU_DEAD | mod, hcpu);
 262
 263         check_for_tasks(cpu);
 264
 265 out_release:
 266         cpu_hotplug_done();
 267         if (!err)
 268                 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
 269         return err;
 270 }
 271
 272 int __ref cpu_down(unsigned int cpu)
 273 {
 274         int err;
 275
 276         cpu_maps_update_begin();
 277
 278         if (cpu_hotplug_disabled) {
 279                 err = -EBUSY;
 280                 goto out;
 281         }
 282
 283         err = _cpu_down(cpu, 0);
 284
 285 out:
 286         cpu_maps_update_done();
 287         return err;
 288 }
 289 EXPORT_SYMBOL(cpu_down);
 290 #endif /*CONFIG_HOTPLUG_CPU*/
 291
 292 /* Requires cpu_add_remove_lock to be held */
 293 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
 294 {
 295         int ret, nr_calls = 0;
 296         void *hcpu = (void *)(long)cpu;
 297         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 298
 299         if (cpu_online(cpu) || !cpu_present(cpu))
 300                 return -EINVAL;
 301
 302         cpu_hotplug_begin();
 303         ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
 304         if (ret) {
 305                 nr_calls--;
 306                 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
 307                                 __func__, cpu);
 308                 goto out_notify;
 309         }
 310
 311         /* Arch-specific enabling code. */
 312         ret = __cpu_up(cpu);
 313         if (ret != 0)
 314                 goto out_notify;
 315         BUG_ON(!cpu_online(cpu));
 316
 317         /* Now call notifier in preparation. */
 318         cpu_notify(CPU_ONLINE | mod, hcpu);
 319
 320 out_notify:
 321         if (ret != 0)
 322                 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
 323         cpu_hotplug_done();
 324
 325         return ret;
 326 }
 327
 328 int __cpuinit cpu_up(unsigned int cpu)
 329 {
 330         int err = 0;
 331
 332 #ifdef  CONFIG_MEMORY_HOTPLUG
 333         int nid;
 334         pg_data_t       *pgdat;
 335 #endif
 336
 337         if (!cpu_possible(cpu)) {
 338                 printk(KERN_ERR "can't online cpu %d because it is not "
 339                         "configured as may-hotadd at boot time\n", cpu);
 340 #if defined(CONFIG_IA64)
 341                 printk(KERN_ERR "please check additional_cpus= boot "
 342                                 "parameter\n");
 343 #endif
 344                 return -EINVAL;
 345         }
 346
 347 #ifdef  CONFIG_MEMORY_HOTPLUG
 348         nid = cpu_to_node(cpu);
 349         if (!node_online(nid)) {
 350                 err = mem_online_node(nid);
 351                 if (err)
 352                         return err;
 353         }
 354
 355         pgdat = NODE_DATA(nid);
 356         if (!pgdat) {
 357                 printk(KERN_ERR
 358                         "Can't online cpu %d due to NULL pgdat\n", cpu);
 359                 return -ENOMEM;
 360         }
 361
 362         if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
 363                 mutex_lock(&zonelists_mutex);
 364                 build_all_zonelists(NULL);
 365                 mutex_unlock(&zonelists_mutex);
 366         }
 367 #endif
 368
 369         cpu_maps_update_begin();
 370
 371         if (cpu_hotplug_disabled) {
 372                 err = -EBUSY;
 373                 goto out;
 374         }
 375
 376         err = _cpu_up(cpu, 0);
 377
 378 out:
 379         cpu_maps_update_done();
 380         return err;
 381 }
 382
 383 #ifdef CONFIG_PM_SLEEP_SMP
 384 static cpumask_var_t frozen_cpus;
 385
 386 void __weak arch_disable_nonboot_cpus_begin(void)
 387 {
 388 }
 389
 390 void __weak arch_disable_nonboot_cpus_end(void)
 391 {
 392 }
 393
 394 int disable_nonboot_cpus(void)
 395 {
 396         int cpu, first_cpu, error = 0;
 397
 398         cpu_maps_update_begin();
 399         first_cpu = cpumask_first(cpu_online_mask);
 400         /*
 401          * We take down all of the non-boot CPUs in one shot to avoid races
 402          * with the userspace trying to use the CPU hotplug at the same time
 403          */
 404         cpumask_clear(frozen_cpus);
 405         arch_disable_nonboot_cpus_begin();
 406
 407         printk("Disabling non-boot CPUs ...\n");
 408         for_each_online_cpu(cpu) {
 409                 if (cpu == first_cpu)
 410                         continue;
 411                 error = _cpu_down(cpu, 1);
 412                 if (!error)
 413                         cpumask_set_cpu(cpu, frozen_cpus);
 414                 else {
 415                         printk(KERN_ERR "Error taking CPU%d down: %d\n",
 416                                 cpu, error);
 417                         break;
 418                 }
 419         }
 420
 421         arch_disable_nonboot_cpus_end();
 422
 423         if (!error) {
 424                 BUG_ON(num_online_cpus() > 1);
 425                 /* Make sure the CPUs won't be enabled by someone else */
 426                 cpu_hotplug_disabled = 1;
 427         } else {
 428                 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
 429         }
 430         cpu_maps_update_done();
 431         return error;
 432 }
 433
 434 void __weak arch_enable_nonboot_cpus_begin(void)
 435 {
 436 }
 437
 438 void __weak arch_enable_nonboot_cpus_end(void)
 439 {
 440 }
 441
 442 void __ref enable_nonboot_cpus(void)
 443 {
 444         int cpu, error;
 445
 446         /* Allow everyone to use the CPU hotplug again */
 447         cpu_maps_update_begin();
 448         cpu_hotplug_disabled = 0;
 449         if (cpumask_empty(frozen_cpus))
 450                 goto out;
 451
 452         printk(KERN_INFO "Enabling non-boot CPUs ...\n");
 453
 454         arch_enable_nonboot_cpus_begin();
 455
 456         for_each_cpu(cpu, frozen_cpus) {
 457                 error = _cpu_up(cpu, 1);
 458                 if (!error) {
 459                         printk(KERN_INFO "CPU%d is up\n", cpu);
 460                         continue;
 461                 }
 462                 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
 463         }
 464
 465         arch_enable_nonboot_cpus_end();
 466
 467         cpumask_clear(frozen_cpus);
 468 out:
 469         cpu_maps_update_done();
 470 }
 471
 472 static int alloc_frozen_cpus(void)
 473 {
 474         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
 475                 return -ENOMEM;
 476         return 0;
 477 }
 478 core_initcall(alloc_frozen_cpus);
 479 #endif /* CONFIG_PM_SLEEP_SMP */
 480
 481 /**
 482  * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
 483  * @cpu: cpu that just started
 484  *
 485  * This function calls the cpu_chain notifiers with CPU_STARTING.
 486  * It must be called by the arch code on the new cpu, before the new cpu
 487  * enables interrupts and before the "boot" cpu returns from __cpu_up().
 488  */
 489 void __cpuinit notify_cpu_starting(unsigned int cpu)
 490 {
 491         unsigned long val = CPU_STARTING;
 492
 493 #ifdef CONFIG_PM_SLEEP_SMP
 494         if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
 495                 val = CPU_STARTING_FROZEN;
 496 #endif /* CONFIG_PM_SLEEP_SMP */
 497         cpu_notify(val, (void *)(long)cpu);
 498 }
 499
 500 #endif /* CONFIG_SMP */
 501
 502 /*
 503  * cpu_bit_bitmap[] is a special, "compressed" data structure that
 504  * represents all NR_CPUS bits binary values of 1<<nr.
 505  *
 506  * It is used by cpumask_of() to get a constant address to a CPU
 507  * mask value that has a single bit set only.
 508  */
 509
 510 /* cpu_bit_bitmap[0] is empty - so we can back into it */
 511 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
 512 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
 513 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
 514 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
 515
 516 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
 517
 518         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
 519         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
 520 #if BITS_PER_LONG > 32
 521         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
 522         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
 523 #endif
 524 };
 525 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
 526
 527 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
 528 EXPORT_SYMBOL(cpu_all_bits);
 529
 530 #ifdef CONFIG_INIT_ALL_POSSIBLE
 531 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
 532         = CPU_BITS_ALL;
 533 #else
 534 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
 535 #endif
 536 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
 537 EXPORT_SYMBOL(cpu_possible_mask);
 538
 539 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
 540 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
 541 EXPORT_SYMBOL(cpu_online_mask);
 542
 543 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
 544 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
 545 EXPORT_SYMBOL(cpu_present_mask);
 546
 547 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
 548 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
 549 EXPORT_SYMBOL(cpu_active_mask);
 550
 551 void set_cpu_possible(unsigned int cpu, bool possible)
 552 {
 553         if (possible)
 554                 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
 555         else
 556                 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
 557 }
 558
 559 void set_cpu_present(unsigned int cpu, bool present)
 560 {
 561         if (present)
 562                 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
 563         else
 564                 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
 565 }
 566
 567 void set_cpu_online(unsigned int cpu, bool online)
 568 {
 569         if (online)
 570                 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
 571         else
 572                 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
 573 }
 574
 575 void set_cpu_active(unsigned int cpu, bool active)
 576 {
 577         if (active)
 578                 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
 579         else
 580                 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
 581 }
 582
 583 void init_cpu_present(const struct cpumask *src)
 584 {
 585         cpumask_copy(to_cpumask(cpu_present_bits), src);
 586 }
 587
 588 void init_cpu_possible(const struct cpumask *src)
 589 {
 590         cpumask_copy(to_cpumask(cpu_possible_bits), src);
 591 }
 592
 593 void init_cpu_online(const struct cpumask *src)
 594 {
 595         cpumask_copy(to_cpumask(cpu_online_bits), src);
 596 }