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  /* #esle #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
 164 EXPORT_SYMBOL(register_cpu_notifier);
 165
 166 void __ref unregister_cpu_notifier(struct notifier_block *nb)
 167 {
 168         cpu_maps_update_begin();
 169         raw_notifier_chain_unregister(&cpu_chain, nb);
 170         cpu_maps_update_done();
 171 }
 172 EXPORT_SYMBOL(unregister_cpu_notifier);
 173
 174 static inline void check_for_tasks(int cpu)
 175 {
 176         struct task_struct *p;
 177
 178         write_lock_irq(&tasklist_lock);
 179         for_each_process(p) {
 180                 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
 181                     (!cputime_eq(p->utime, cputime_zero) ||
 182                      !cputime_eq(p->stime, cputime_zero)))
 183                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
 184                                 "(state = %ld, flags = %x)\n",
 185                                 p->comm, task_pid_nr(p), cpu,
 186                                 p->state, p->flags);
 187         }
 188         write_unlock_irq(&tasklist_lock);
 189 }
 190
 191 struct take_cpu_down_param {
 192         unsigned long mod;
 193         void *hcpu;
 194 };
 195
 196 /* Take this CPU down. */
 197 static int __ref take_cpu_down(void *_param)
 198 {
 199         struct take_cpu_down_param *param = _param;
 200         unsigned int cpu = (unsigned long)param->hcpu;
 201         int err;
 202
 203         /* Ensure this CPU doesn't handle any more interrupts. */
 204         err = __cpu_disable();
 205         if (err < 0)
 206                 return err;
 207
 208         cpu_notify(CPU_DYING | param->mod, param->hcpu);
 209
 210         return 0;
 211 }
 212
 213 /* Requires cpu_add_remove_lock to be held */
 214 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
 215 {
 216         int err, nr_calls = 0;
 217         void *hcpu = (void *)(long)cpu;
 218         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 219         struct take_cpu_down_param tcd_param = {
 220                 .mod = mod,
 221                 .hcpu = hcpu,
 222         };
 223
 224         if (num_online_cpus() == 1)
 225                 return -EBUSY;
 226
 227         if (!cpu_online(cpu))
 228                 return -EINVAL;
 229
 230         cpu_hotplug_begin();
 231         err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
 232         if (err) {
 233                 nr_calls--;
 234                 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
 235                 printk("%s: attempt to take down CPU %u failed\n",
 236                                 __func__, cpu);
 237                 goto out_release;
 238         }
 239
 240         err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
 241         if (err) {
 242                 /* CPU didn't die: tell everyone.  Can't complain. */
 243                 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
 244
 245                 goto out_release;
 246         }
 247         BUG_ON(cpu_online(cpu));
 248
 249         /*
 250          * The migration_call() CPU_DYING callback will have removed all
 251          * runnable tasks from the cpu, there's only the idle task left now
 252          * that the migration thread is done doing the stop_machine thing.
 253          */
 254         BUG_ON(!idle_cpu(cpu));
 255
 256         /* This actually kills the CPU. */
 257         __cpu_die(cpu);
 258
 259         /* CPU is completely dead: tell everyone.  Too late to complain. */
 260         cpu_notify_nofail(CPU_DEAD | mod, hcpu);
 261
 262         check_for_tasks(cpu);
 263
 264 out_release:
 265         cpu_hotplug_done();
 266         if (!err)
 267                 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
 268         return err;
 269 }
 270
 271 int __ref cpu_down(unsigned int cpu)
 272 {
 273         int err;
 274
 275         cpu_maps_update_begin();
 276
 277         if (cpu_hotplug_disabled) {
 278                 err = -EBUSY;
 279                 goto out;
 280         }
 281
 282         err = _cpu_down(cpu, 0);
 283
 284 out:
 285         cpu_maps_update_done();
 286         return err;
 287 }
 288 EXPORT_SYMBOL(cpu_down);
 289 #endif /*CONFIG_HOTPLUG_CPU*/
 290
 291 /* Requires cpu_add_remove_lock to be held */
 292 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
 293 {
 294         int ret, nr_calls = 0;
 295         void *hcpu = (void *)(long)cpu;
 296         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 297
 298         if (cpu_online(cpu) || !cpu_present(cpu))
 299                 return -EINVAL;
 300
 301         cpu_hotplug_begin();
 302         ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
 303         if (ret) {
 304                 nr_calls--;
 305                 printk("%s: attempt to bring up CPU %u failed\n",
 306                                 __func__, cpu);
 307                 goto out_notify;
 308         }
 309
 310         /* Arch-specific enabling code. */
 311         ret = __cpu_up(cpu);
 312         if (ret != 0)
 313                 goto out_notify;
 314         BUG_ON(!cpu_online(cpu));
 315
 316         /* Now call notifier in preparation. */
 317         cpu_notify(CPU_ONLINE | mod, hcpu);
 318
 319 out_notify:
 320         if (ret != 0)
 321                 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
 322         cpu_hotplug_done();
 323
 324         return ret;
 325 }
 326
 327 int __cpuinit cpu_up(unsigned int cpu)
 328 {
 329         int err = 0;
 330
 331 #ifdef  CONFIG_MEMORY_HOTPLUG
 332         int nid;
 333         pg_data_t       *pgdat;
 334 #endif
 335
 336         if (!cpu_possible(cpu)) {
 337                 printk(KERN_ERR "can't online cpu %d because it is not "
 338                         "configured as may-hotadd at boot time\n", cpu);
 339 #if defined(CONFIG_IA64)
 340                 printk(KERN_ERR "please check additional_cpus= boot "
 341                                 "parameter\n");
 342 #endif
 343                 return -EINVAL;
 344         }
 345
 346 #ifdef  CONFIG_MEMORY_HOTPLUG
 347         nid = cpu_to_node(cpu);
 348         if (!node_online(nid)) {
 349                 err = mem_online_node(nid);
 350                 if (err)
 351                         return err;
 352         }
 353
 354         pgdat = NODE_DATA(nid);
 355         if (!pgdat) {
 356                 printk(KERN_ERR
 357                         "Can't online cpu %d due to NULL pgdat\n", cpu);
 358                 return -ENOMEM;
 359         }
 360
 361         if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
 362                 mutex_lock(&zonelists_mutex);
 363                 build_all_zonelists(NULL);
 364                 mutex_unlock(&zonelists_mutex);
 365         }
 366 #endif
 367
 368         cpu_maps_update_begin();
 369
 370         if (cpu_hotplug_disabled) {
 371                 err = -EBUSY;
 372                 goto out;
 373         }
 374
 375         err = _cpu_up(cpu, 0);
 376
 377 out:
 378         cpu_maps_update_done();
 379         return err;
 380 }
 381
 382 #ifdef CONFIG_PM_SLEEP_SMP
 383 static cpumask_var_t frozen_cpus;
 384
 385 int disable_nonboot_cpus(void)
 386 {
 387         int cpu, first_cpu, error = 0;
 388
 389         cpu_maps_update_begin();
 390         first_cpu = cpumask_first(cpu_online_mask);
 391         /*
 392          * We take down all of the non-boot CPUs in one shot to avoid races
 393          * with the userspace trying to use the CPU hotplug at the same time
 394          */
 395         cpumask_clear(frozen_cpus);
 396
 397         printk("Disabling non-boot CPUs ...\n");
 398         for_each_online_cpu(cpu) {
 399                 if (cpu == first_cpu)
 400                         continue;
 401                 error = _cpu_down(cpu, 1);
 402                 if (!error)
 403                         cpumask_set_cpu(cpu, frozen_cpus);
 404                 else {
 405                         printk(KERN_ERR "Error taking CPU%d down: %d\n",
 406                                 cpu, error);
 407                         break;
 408                 }
 409         }
 410
 411         if (!error) {
 412                 BUG_ON(num_online_cpus() > 1);
 413                 /* Make sure the CPUs won't be enabled by someone else */
 414                 cpu_hotplug_disabled = 1;
 415         } else {
 416                 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
 417         }
 418         cpu_maps_update_done();
 419         return error;
 420 }
 421
 422 void __weak arch_enable_nonboot_cpus_begin(void)
 423 {
 424 }
 425
 426 void __weak arch_enable_nonboot_cpus_end(void)
 427 {
 428 }
 429
 430 void __ref enable_nonboot_cpus(void)
 431 {
 432         int cpu, error;
 433
 434         /* Allow everyone to use the CPU hotplug again */
 435         cpu_maps_update_begin();
 436         cpu_hotplug_disabled = 0;
 437         if (cpumask_empty(frozen_cpus))
 438                 goto out;
 439
 440         printk("Enabling non-boot CPUs ...\n");
 441
 442         arch_enable_nonboot_cpus_begin();
 443
 444         for_each_cpu(cpu, frozen_cpus) {
 445                 error = _cpu_up(cpu, 1);
 446                 if (!error) {
 447                         printk("CPU%d is up\n", cpu);
 448                         continue;
 449                 }
 450                 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
 451         }
 452
 453         arch_enable_nonboot_cpus_end();
 454
 455         cpumask_clear(frozen_cpus);
 456 out:
 457         cpu_maps_update_done();
 458 }
 459
 460 static int alloc_frozen_cpus(void)
 461 {
 462         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
 463                 return -ENOMEM;
 464         return 0;
 465 }
 466 core_initcall(alloc_frozen_cpus);
 467 #endif /* CONFIG_PM_SLEEP_SMP */
 468
 469 /**
 470  * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
 471  * @cpu: cpu that just started
 472  *
 473  * This function calls the cpu_chain notifiers with CPU_STARTING.
 474  * It must be called by the arch code on the new cpu, before the new cpu
 475  * enables interrupts and before the "boot" cpu returns from __cpu_up().
 476  */
 477 void __cpuinit notify_cpu_starting(unsigned int cpu)
 478 {
 479         unsigned long val = CPU_STARTING;
 480
 481 #ifdef CONFIG_PM_SLEEP_SMP
 482         if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
 483                 val = CPU_STARTING_FROZEN;
 484 #endif /* CONFIG_PM_SLEEP_SMP */
 485         cpu_notify(val, (void *)(long)cpu);
 486 }
 487
 488 #endif /* CONFIG_SMP */
 489
 490 /*
 491  * cpu_bit_bitmap[] is a special, "compressed" data structure that
 492  * represents all NR_CPUS bits binary values of 1<<nr.
 493  *
 494  * It is used by cpumask_of() to get a constant address to a CPU
 495  * mask value that has a single bit set only.
 496  */
 497
 498 /* cpu_bit_bitmap[0] is empty - so we can back into it */
 499 #define MASK_DECLARE_1(x)       [x+1][0] = 1UL << (x)
 500 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
 501 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
 502 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
 503
 504 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
 505
 506         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
 507         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
 508 #if BITS_PER_LONG > 32
 509         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
 510         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
 511 #endif
 512 };
 513 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
 514
 515 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
 516 EXPORT_SYMBOL(cpu_all_bits);
 517
 518 #ifdef CONFIG_INIT_ALL_POSSIBLE
 519 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
 520         = CPU_BITS_ALL;
 521 #else
 522 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
 523 #endif
 524 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
 525 EXPORT_SYMBOL(cpu_possible_mask);
 526
 527 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
 528 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
 529 EXPORT_SYMBOL(cpu_online_mask);
 530
 531 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
 532 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
 533 EXPORT_SYMBOL(cpu_present_mask);
 534
 535 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
 536 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
 537 EXPORT_SYMBOL(cpu_active_mask);
 538
 539 void set_cpu_possible(unsigned int cpu, bool possible)
 540 {
 541         if (possible)
 542                 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
 543         else
 544                 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
 545 }
 546
 547 void set_cpu_present(unsigned int cpu, bool present)
 548 {
 549         if (present)
 550                 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
 551         else
 552                 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
 553 }
 554
 555 void set_cpu_online(unsigned int cpu, bool online)
 556 {
 557         if (online)
 558                 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
 559         else
 560                 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
 561 }
 562
 563 void set_cpu_active(unsigned int cpu, bool active)
 564 {
 565         if (active)
 566                 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
 567         else
 568                 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
 569 }
 570
 571 void init_cpu_present(const struct cpumask *src)
 572 {
 573         cpumask_copy(to_cpumask(cpu_present_bits), src);
 574 }
 575
 576 void init_cpu_possible(const struct cpumask *src)
 577 {
 578         cpumask_copy(to_cpumask(cpu_possible_bits), src);
 579 }
 580
 581 void init_cpu_online(const struct cpumask *src)
 582 {
 583         cpumask_copy(to_cpumask(cpu_online_bits), src);
 584 }