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 18 #ifdef CONFIG_SMP 19 /* Serializes the updates to cpu_online_mask, cpu_present_mask */ 20 static DEFINE_MUTEX(cpu_add_remove_lock); 21 22 static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain); 23 24 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing. 25 * Should always be manipulated under cpu_add_remove_lock 26 */ 27 static int cpu_hotplug_disabled; 28 29 static struct { 30 struct task_struct *active_writer; 31 struct mutex lock; /* Synchronizes accesses to refcount, */ 32 /* 33 * Also blocks the new readers during 34 * an ongoing cpu hotplug operation. 35 */ 36 int refcount; 37 } cpu_hotplug = { 38 .active_writer = NULL, 39 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock), 40 .refcount = 0, 41 }; 42 43 #ifdef CONFIG_HOTPLUG_CPU 44 45 void get_online_cpus(void) 46 { 47 might_sleep(); 48 if (cpu_hotplug.active_writer == current) 49 return; 50 mutex_lock(&cpu_hotplug.lock); 51 cpu_hotplug.refcount++; 52 mutex_unlock(&cpu_hotplug.lock); 53 54 } 55 EXPORT_SYMBOL_GPL(get_online_cpus); 56 57 void put_online_cpus(void) 58 { 59 if (cpu_hotplug.active_writer == current) 60 return; 61 mutex_lock(&cpu_hotplug.lock); 62 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer)) 63 wake_up_process(cpu_hotplug.active_writer); 64 mutex_unlock(&cpu_hotplug.lock); 65 66 } 67 EXPORT_SYMBOL_GPL(put_online_cpus); 68 69 #endif /* CONFIG_HOTPLUG_CPU */ 70 71 /* 72 * The following two API's must be used when attempting 73 * to serialize the updates to cpu_online_mask, cpu_present_mask. 74 */ 75 void cpu_maps_update_begin(void) 76 { 77 mutex_lock(&cpu_add_remove_lock); 78 } 79 80 void cpu_maps_update_done(void) 81 { 82 mutex_unlock(&cpu_add_remove_lock); 83 } 84 85 /* 86 * This ensures that the hotplug operation can begin only when the 87 * refcount goes to zero. 88 * 89 * Note that during a cpu-hotplug operation, the new readers, if any, 90 * will be blocked by the cpu_hotplug.lock 91 * 92 * Since cpu_hotplug_begin() is always called after invoking 93 * cpu_maps_update_begin(), we can be sure that only one writer is active. 94 * 95 * Note that theoretically, there is a possibility of a livelock: 96 * - Refcount goes to zero, last reader wakes up the sleeping 97 * writer. 98 * - Last reader unlocks the cpu_hotplug.lock. 99 * - A new reader arrives at this moment, bumps up the refcount. 100 * - The writer acquires the cpu_hotplug.lock finds the refcount 101 * non zero and goes to sleep again. 102 * 103 * However, this is very difficult to achieve in practice since 104 * get_online_cpus() not an api which is called all that often. 105 * 106 */ 107 static void cpu_hotplug_begin(void) 108 { 109 cpu_hotplug.active_writer = current; 110 111 for (;;) { 112 mutex_lock(&cpu_hotplug.lock); 113 if (likely(!cpu_hotplug.refcount)) 114 break; 115 __set_current_state(TASK_UNINTERRUPTIBLE); 116 mutex_unlock(&cpu_hotplug.lock); 117 schedule(); 118 } 119 } 120 121 static void cpu_hotplug_done(void) 122 { 123 cpu_hotplug.active_writer = NULL; 124 mutex_unlock(&cpu_hotplug.lock); 125 } 126 /* Need to know about CPUs going up/down? */ 127 int __ref register_cpu_notifier(struct notifier_block *nb) 128 { 129 int ret; 130 cpu_maps_update_begin(); 131 ret = raw_notifier_chain_register(&cpu_chain, nb); 132 cpu_maps_update_done(); 133 return ret; 134 } 135 136 #ifdef CONFIG_HOTPLUG_CPU 137 138 EXPORT_SYMBOL(register_cpu_notifier); 139 140 void __ref unregister_cpu_notifier(struct notifier_block *nb) 141 { 142 cpu_maps_update_begin(); 143 raw_notifier_chain_unregister(&cpu_chain, nb); 144 cpu_maps_update_done(); 145 } 146 EXPORT_SYMBOL(unregister_cpu_notifier); 147 148 static inline void check_for_tasks(int cpu) 149 { 150 struct task_struct *p; 151 152 write_lock_irq(&tasklist_lock); 153 for_each_process(p) { 154 if (task_cpu(p) == cpu && 155 (!cputime_eq(p->utime, cputime_zero) || 156 !cputime_eq(p->stime, cputime_zero))) 157 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\ 158 (state = %ld, flags = %x) \n", 159 p->comm, task_pid_nr(p), cpu, 160 p->state, p->flags); 161 } 162 write_unlock_irq(&tasklist_lock); 163 } 164 165 struct take_cpu_down_param { 166 unsigned long mod; 167 void *hcpu; 168 }; 169 170 /* Take this CPU down. */ 171 static int __ref take_cpu_down(void *_param) 172 { 173 struct take_cpu_down_param *param = _param; 174 int err; 175 176 /* Ensure this CPU doesn't handle any more interrupts. */ 177 err = __cpu_disable(); 178 if (err < 0) 179 return err; 180 181 raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod, 182 param->hcpu); 183 184 /* Force idle task to run as soon as we yield: it should 185 immediately notice cpu is offline and die quickly. */ 186 sched_idle_next(); 187 return 0; 188 } 189 190 /* Requires cpu_add_remove_lock to be held */ 191 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen) 192 { 193 int err, nr_calls = 0; 194 cpumask_var_t old_allowed; 195 void *hcpu = (void *)(long)cpu; 196 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0; 197 struct take_cpu_down_param tcd_param = { 198 .mod = mod, 199 .hcpu = hcpu, 200 }; 201 202 if (num_online_cpus() == 1) 203 return -EBUSY; 204 205 if (!cpu_online(cpu)) 206 return -EINVAL; 207 208 if (!alloc_cpumask_var(&old_allowed, GFP_KERNEL)) 209 return -ENOMEM; 210 211 cpu_hotplug_begin(); 212 set_cpu_active(cpu, false); 213 err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod, 214 hcpu, -1, &nr_calls); 215 if (err == NOTIFY_BAD) { 216 set_cpu_active(cpu, true); 217 218 nr_calls--; 219 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod, 220 hcpu, nr_calls, NULL); 221 printk("%s: attempt to take down CPU %u failed\n", 222 __func__, cpu); 223 err = -EINVAL; 224 goto out_release; 225 } 226 227 /* Ensure that we are not runnable on dying cpu */ 228 cpumask_copy(old_allowed, ¤t->cpus_allowed); 229 set_cpus_allowed_ptr(current, cpu_active_mask); 230 231 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu)); 232 if (err) { 233 set_cpu_active(cpu, true); 234 /* CPU didn't die: tell everyone. Can't complain. */ 235 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod, 236 hcpu) == NOTIFY_BAD) 237 BUG(); 238 239 goto out_allowed; 240 } 241 BUG_ON(cpu_online(cpu)); 242 243 /* Wait for it to sleep (leaving idle task). */ 244 while (!idle_cpu(cpu)) 245 yield(); 246 247 /* This actually kills the CPU. */ 248 __cpu_die(cpu); 249 250 /* CPU is completely dead: tell everyone. Too late to complain. */ 251 if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod, 252 hcpu) == NOTIFY_BAD) 253 BUG(); 254 255 check_for_tasks(cpu); 256 257 out_allowed: 258 set_cpus_allowed_ptr(current, old_allowed); 259 out_release: 260 cpu_hotplug_done(); 261 if (!err) { 262 if (raw_notifier_call_chain(&cpu_chain, CPU_POST_DEAD | mod, 263 hcpu) == NOTIFY_BAD) 264 BUG(); 265 } 266 free_cpumask_var(old_allowed); 267 return err; 268 } 269 270 int __ref cpu_down(unsigned int cpu) 271 { 272 int err; 273 274 err = stop_machine_create(); 275 if (err) 276 return err; 277 cpu_maps_update_begin(); 278 279 if (cpu_hotplug_disabled) { 280 err = -EBUSY; 281 goto out; 282 } 283 284 err = _cpu_down(cpu, 0); 285 286 out: 287 cpu_maps_update_done(); 288 stop_machine_destroy(); 289 return err; 290 } 291 EXPORT_SYMBOL(cpu_down); 292 #endif /*CONFIG_HOTPLUG_CPU*/ 293 294 /* Requires cpu_add_remove_lock to be held */ 295 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) 296 { 297 int ret, nr_calls = 0; 298 void *hcpu = (void *)(long)cpu; 299 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0; 300 301 if (cpu_online(cpu) || !cpu_present(cpu)) 302 return -EINVAL; 303 304 cpu_hotplug_begin(); 305 ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu, 306 -1, &nr_calls); 307 if (ret == NOTIFY_BAD) { 308 nr_calls--; 309 printk("%s: attempt to bring up CPU %u failed\n", 310 __func__, cpu); 311 ret = -EINVAL; 312 goto out_notify; 313 } 314 315 /* Arch-specific enabling code. */ 316 ret = __cpu_up(cpu); 317 if (ret != 0) 318 goto out_notify; 319 BUG_ON(!cpu_online(cpu)); 320 321 set_cpu_active(cpu, true); 322 323 /* Now call notifier in preparation. */ 324 raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu); 325 326 out_notify: 327 if (ret != 0) 328 __raw_notifier_call_chain(&cpu_chain, 329 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL); 330 cpu_hotplug_done(); 331 332 return ret; 333 } 334 335 int __cpuinit cpu_up(unsigned int cpu) 336 { 337 int err = 0; 338 if (!cpu_possible(cpu)) { 339 printk(KERN_ERR "can't online cpu %d because it is not " 340 "configured as may-hotadd at boot time\n", cpu); 341 #if defined(CONFIG_IA64) || defined(CONFIG_X86_64) 342 printk(KERN_ERR "please check additional_cpus= boot " 343 "parameter\n"); 344 #endif 345 return -EINVAL; 346 } 347 348 cpu_maps_update_begin(); 349 350 if (cpu_hotplug_disabled) { 351 err = -EBUSY; 352 goto out; 353 } 354 355 err = _cpu_up(cpu, 0); 356 357 out: 358 cpu_maps_update_done(); 359 return err; 360 } 361 362 #ifdef CONFIG_PM_SLEEP_SMP 363 static cpumask_var_t frozen_cpus; 364 365 int disable_nonboot_cpus(void) 366 { 367 int cpu, first_cpu, error; 368 369 error = stop_machine_create(); 370 if (error) 371 return error; 372 cpu_maps_update_begin(); 373 first_cpu = cpumask_first(cpu_online_mask); 374 /* 375 * We take down all of the non-boot CPUs in one shot to avoid races 376 * with the userspace trying to use the CPU hotplug at the same time 377 */ 378 cpumask_clear(frozen_cpus); 379 380 printk("Disabling non-boot CPUs ...\n"); 381 for_each_online_cpu(cpu) { 382 if (cpu == first_cpu) 383 continue; 384 error = _cpu_down(cpu, 1); 385 if (!error) 386 cpumask_set_cpu(cpu, frozen_cpus); 387 else { 388 printk(KERN_ERR "Error taking CPU%d down: %d\n", 389 cpu, error); 390 break; 391 } 392 } 393 394 if (!error) { 395 BUG_ON(num_online_cpus() > 1); 396 /* Make sure the CPUs won't be enabled by someone else */ 397 cpu_hotplug_disabled = 1; 398 } else { 399 printk(KERN_ERR "Non-boot CPUs are not disabled\n"); 400 } 401 cpu_maps_update_done(); 402 stop_machine_destroy(); 403 return error; 404 } 405 406 void __weak arch_enable_nonboot_cpus_begin(void) 407 { 408 } 409 410 void __weak arch_enable_nonboot_cpus_end(void) 411 { 412 } 413 414 void __ref enable_nonboot_cpus(void) 415 { 416 int cpu, error; 417 418 /* Allow everyone to use the CPU hotplug again */ 419 cpu_maps_update_begin(); 420 cpu_hotplug_disabled = 0; 421 if (cpumask_empty(frozen_cpus)) 422 goto out; 423 424 printk("Enabling non-boot CPUs ...\n"); 425 426 arch_enable_nonboot_cpus_begin(); 427 428 for_each_cpu(cpu, frozen_cpus) { 429 error = _cpu_up(cpu, 1); 430 if (!error) { 431 printk("CPU%d is up\n", cpu); 432 continue; 433 } 434 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error); 435 } 436 437 arch_enable_nonboot_cpus_end(); 438 439 cpumask_clear(frozen_cpus); 440 out: 441 cpu_maps_update_done(); 442 } 443 444 static int alloc_frozen_cpus(void) 445 { 446 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO)) 447 return -ENOMEM; 448 return 0; 449 } 450 core_initcall(alloc_frozen_cpus); 451 #endif /* CONFIG_PM_SLEEP_SMP */ 452 453 /** 454 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers 455 * @cpu: cpu that just started 456 * 457 * This function calls the cpu_chain notifiers with CPU_STARTING. 458 * It must be called by the arch code on the new cpu, before the new cpu 459 * enables interrupts and before the "boot" cpu returns from __cpu_up(). 460 */ 461 void __cpuinit notify_cpu_starting(unsigned int cpu) 462 { 463 unsigned long val = CPU_STARTING; 464 465 #ifdef CONFIG_PM_SLEEP_SMP 466 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus)) 467 val = CPU_STARTING_FROZEN; 468 #endif /* CONFIG_PM_SLEEP_SMP */ 469 raw_notifier_call_chain(&cpu_chain, val, (void *)(long)cpu); 470 } 471 472 #endif /* CONFIG_SMP */ 473 474 /* 475 * cpu_bit_bitmap[] is a special, "compressed" data structure that 476 * represents all NR_CPUS bits binary values of 1<<nr. 477 * 478 * It is used by cpumask_of() to get a constant address to a CPU 479 * mask value that has a single bit set only. 480 */ 481 482 /* cpu_bit_bitmap[0] is empty - so we can back into it */ 483 #define MASK_DECLARE_1(x) [x+1][0] = 1UL << (x) 484 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1) 485 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2) 486 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4) 487 488 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = { 489 490 MASK_DECLARE_8(0), MASK_DECLARE_8(8), 491 MASK_DECLARE_8(16), MASK_DECLARE_8(24), 492 #if BITS_PER_LONG > 32 493 MASK_DECLARE_8(32), MASK_DECLARE_8(40), 494 MASK_DECLARE_8(48), MASK_DECLARE_8(56), 495 #endif 496 }; 497 EXPORT_SYMBOL_GPL(cpu_bit_bitmap); 498 499 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL; 500 EXPORT_SYMBOL(cpu_all_bits); 501 502 #ifdef CONFIG_INIT_ALL_POSSIBLE 503 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly 504 = CPU_BITS_ALL; 505 #else 506 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly; 507 #endif 508 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits); 509 EXPORT_SYMBOL(cpu_possible_mask); 510 511 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly; 512 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits); 513 EXPORT_SYMBOL(cpu_online_mask); 514 515 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly; 516 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits); 517 EXPORT_SYMBOL(cpu_present_mask); 518 519 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly; 520 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits); 521 EXPORT_SYMBOL(cpu_active_mask); 522 523 void set_cpu_possible(unsigned int cpu, bool possible) 524 { 525 if (possible) 526 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits)); 527 else 528 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits)); 529 } 530 531 void set_cpu_present(unsigned int cpu, bool present) 532 { 533 if (present) 534 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits)); 535 else 536 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits)); 537 } 538 539 void set_cpu_online(unsigned int cpu, bool online) 540 { 541 if (online) 542 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits)); 543 else 544 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits)); 545 } 546 547 void set_cpu_active(unsigned int cpu, bool active) 548 { 549 if (active) 550 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits)); 551 else 552 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits)); 553 } 554 555 void init_cpu_present(const struct cpumask *src) 556 { 557 cpumask_copy(to_cpumask(cpu_present_bits), src); 558 } 559 560 void init_cpu_possible(const struct cpumask *src) 561 { 562 cpumask_copy(to_cpumask(cpu_possible_bits), src); 563 } 564 565 void init_cpu_online(const struct cpumask *src) 566 { 567 cpumask_copy(to_cpumask(cpu_online_bits), src); 568 } 569