| 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * Generic helpers for smp ipi calls |
| 4 | * |
| 5 | * (C) Jens Axboe <jens.axboe@oracle.com> 2008 |
| 6 | */ |
| 7 | |
| 8 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 9 | |
| 10 | #include <linux/irq_work.h> |
| 11 | #include <linux/rcupdate.h> |
| 12 | #include <linux/rculist.h> |
| 13 | #include <linux/kernel.h> |
| 14 | #include <linux/export.h> |
| 15 | #include <linux/percpu.h> |
| 16 | #include <linux/init.h> |
| 17 | #include <linux/gfp.h> |
| 18 | #include <linux/smp.h> |
| 19 | #include <linux/cpu.h> |
| 20 | #include <linux/sched.h> |
| 21 | #include <linux/sched/idle.h> |
| 22 | #include <linux/hypervisor.h> |
| 23 | |
| 24 | #include "smpboot.h" |
| 25 | |
| 26 | enum { |
| 27 | CSD_FLAG_LOCK = 0x01, |
| 28 | CSD_FLAG_SYNCHRONOUS = 0x02, |
| 29 | }; |
| 30 | |
| 31 | struct call_function_data { |
| 32 | call_single_data_t __percpu *csd; |
| 33 | cpumask_var_t cpumask; |
| 34 | cpumask_var_t cpumask_ipi; |
| 35 | }; |
| 36 | |
| 37 | static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data); |
| 38 | |
| 39 | static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue); |
| 40 | |
| 41 | static void flush_smp_call_function_queue(bool warn_cpu_offline); |
| 42 | |
| 43 | int smpcfd_prepare_cpu(unsigned int cpu) |
| 44 | { |
| 45 | struct call_function_data *cfd = &per_cpu(cfd_data, cpu); |
| 46 | |
| 47 | if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, |
| 48 | cpu_to_node(cpu))) |
| 49 | return -ENOMEM; |
| 50 | if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, |
| 51 | cpu_to_node(cpu))) { |
| 52 | free_cpumask_var(cfd->cpumask); |
| 53 | return -ENOMEM; |
| 54 | } |
| 55 | cfd->csd = alloc_percpu(call_single_data_t); |
| 56 | if (!cfd->csd) { |
| 57 | free_cpumask_var(cfd->cpumask); |
| 58 | free_cpumask_var(cfd->cpumask_ipi); |
| 59 | return -ENOMEM; |
| 60 | } |
| 61 | |
| 62 | return 0; |
| 63 | } |
| 64 | |
| 65 | int smpcfd_dead_cpu(unsigned int cpu) |
| 66 | { |
| 67 | struct call_function_data *cfd = &per_cpu(cfd_data, cpu); |
| 68 | |
| 69 | free_cpumask_var(cfd->cpumask); |
| 70 | free_cpumask_var(cfd->cpumask_ipi); |
| 71 | free_percpu(cfd->csd); |
| 72 | return 0; |
| 73 | } |
| 74 | |
| 75 | int smpcfd_dying_cpu(unsigned int cpu) |
| 76 | { |
| 77 | /* |
| 78 | * The IPIs for the smp-call-function callbacks queued by other |
| 79 | * CPUs might arrive late, either due to hardware latencies or |
| 80 | * because this CPU disabled interrupts (inside stop-machine) |
| 81 | * before the IPIs were sent. So flush out any pending callbacks |
| 82 | * explicitly (without waiting for the IPIs to arrive), to |
| 83 | * ensure that the outgoing CPU doesn't go offline with work |
| 84 | * still pending. |
| 85 | */ |
| 86 | flush_smp_call_function_queue(false); |
| 87 | return 0; |
| 88 | } |
| 89 | |
| 90 | void __init call_function_init(void) |
| 91 | { |
| 92 | int i; |
| 93 | |
| 94 | for_each_possible_cpu(i) |
| 95 | init_llist_head(&per_cpu(call_single_queue, i)); |
| 96 | |
| 97 | smpcfd_prepare_cpu(smp_processor_id()); |
| 98 | } |
| 99 | |
| 100 | /* |
| 101 | * csd_lock/csd_unlock used to serialize access to per-cpu csd resources |
| 102 | * |
| 103 | * For non-synchronous ipi calls the csd can still be in use by the |
| 104 | * previous function call. For multi-cpu calls its even more interesting |
| 105 | * as we'll have to ensure no other cpu is observing our csd. |
| 106 | */ |
| 107 | static __always_inline void csd_lock_wait(call_single_data_t *csd) |
| 108 | { |
| 109 | smp_cond_load_acquire(&csd->flags, !(VAL & CSD_FLAG_LOCK)); |
| 110 | } |
| 111 | |
| 112 | static __always_inline void csd_lock(call_single_data_t *csd) |
| 113 | { |
| 114 | csd_lock_wait(csd); |
| 115 | csd->flags |= CSD_FLAG_LOCK; |
| 116 | |
| 117 | /* |
| 118 | * prevent CPU from reordering the above assignment |
| 119 | * to ->flags with any subsequent assignments to other |
| 120 | * fields of the specified call_single_data_t structure: |
| 121 | */ |
| 122 | smp_wmb(); |
| 123 | } |
| 124 | |
| 125 | static __always_inline void csd_unlock(call_single_data_t *csd) |
| 126 | { |
| 127 | WARN_ON(!(csd->flags & CSD_FLAG_LOCK)); |
| 128 | |
| 129 | /* |
| 130 | * ensure we're all done before releasing data: |
| 131 | */ |
| 132 | smp_store_release(&csd->flags, 0); |
| 133 | } |
| 134 | |
| 135 | static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data); |
| 136 | |
| 137 | /* |
| 138 | * Insert a previously allocated call_single_data_t element |
| 139 | * for execution on the given CPU. data must already have |
| 140 | * ->func, ->info, and ->flags set. |
| 141 | */ |
| 142 | static int generic_exec_single(int cpu, call_single_data_t *csd, |
| 143 | smp_call_func_t func, void *info) |
| 144 | { |
| 145 | if (cpu == smp_processor_id()) { |
| 146 | unsigned long flags; |
| 147 | |
| 148 | /* |
| 149 | * We can unlock early even for the synchronous on-stack case, |
| 150 | * since we're doing this from the same CPU.. |
| 151 | */ |
| 152 | csd_unlock(csd); |
| 153 | local_irq_save(flags); |
| 154 | func(info); |
| 155 | local_irq_restore(flags); |
| 156 | return 0; |
| 157 | } |
| 158 | |
| 159 | |
| 160 | if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) { |
| 161 | csd_unlock(csd); |
| 162 | return -ENXIO; |
| 163 | } |
| 164 | |
| 165 | csd->func = func; |
| 166 | csd->info = info; |
| 167 | |
| 168 | /* |
| 169 | * The list addition should be visible before sending the IPI |
| 170 | * handler locks the list to pull the entry off it because of |
| 171 | * normal cache coherency rules implied by spinlocks. |
| 172 | * |
| 173 | * If IPIs can go out of order to the cache coherency protocol |
| 174 | * in an architecture, sufficient synchronisation should be added |
| 175 | * to arch code to make it appear to obey cache coherency WRT |
| 176 | * locking and barrier primitives. Generic code isn't really |
| 177 | * equipped to do the right thing... |
| 178 | */ |
| 179 | if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu))) |
| 180 | arch_send_call_function_single_ipi(cpu); |
| 181 | |
| 182 | return 0; |
| 183 | } |
| 184 | |
| 185 | /** |
| 186 | * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks |
| 187 | * |
| 188 | * Invoked by arch to handle an IPI for call function single. |
| 189 | * Must be called with interrupts disabled. |
| 190 | */ |
| 191 | void generic_smp_call_function_single_interrupt(void) |
| 192 | { |
| 193 | flush_smp_call_function_queue(true); |
| 194 | } |
| 195 | |
| 196 | /** |
| 197 | * flush_smp_call_function_queue - Flush pending smp-call-function callbacks |
| 198 | * |
| 199 | * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an |
| 200 | * offline CPU. Skip this check if set to 'false'. |
| 201 | * |
| 202 | * Flush any pending smp-call-function callbacks queued on this CPU. This is |
| 203 | * invoked by the generic IPI handler, as well as by a CPU about to go offline, |
| 204 | * to ensure that all pending IPI callbacks are run before it goes completely |
| 205 | * offline. |
| 206 | * |
| 207 | * Loop through the call_single_queue and run all the queued callbacks. |
| 208 | * Must be called with interrupts disabled. |
| 209 | */ |
| 210 | static void flush_smp_call_function_queue(bool warn_cpu_offline) |
| 211 | { |
| 212 | struct llist_head *head; |
| 213 | struct llist_node *entry; |
| 214 | call_single_data_t *csd, *csd_next; |
| 215 | static bool warned; |
| 216 | |
| 217 | lockdep_assert_irqs_disabled(); |
| 218 | |
| 219 | head = this_cpu_ptr(&call_single_queue); |
| 220 | entry = llist_del_all(head); |
| 221 | entry = llist_reverse_order(entry); |
| 222 | |
| 223 | /* There shouldn't be any pending callbacks on an offline CPU. */ |
| 224 | if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) && |
| 225 | !warned && !llist_empty(head))) { |
| 226 | warned = true; |
| 227 | WARN(1, "IPI on offline CPU %d\n", smp_processor_id()); |
| 228 | |
| 229 | /* |
| 230 | * We don't have to use the _safe() variant here |
| 231 | * because we are not invoking the IPI handlers yet. |
| 232 | */ |
| 233 | llist_for_each_entry(csd, entry, llist) |
| 234 | pr_warn("IPI callback %pS sent to offline CPU\n", |
| 235 | csd->func); |
| 236 | } |
| 237 | |
| 238 | llist_for_each_entry_safe(csd, csd_next, entry, llist) { |
| 239 | smp_call_func_t func = csd->func; |
| 240 | void *info = csd->info; |
| 241 | |
| 242 | /* Do we wait until *after* callback? */ |
| 243 | if (csd->flags & CSD_FLAG_SYNCHRONOUS) { |
| 244 | func(info); |
| 245 | csd_unlock(csd); |
| 246 | } else { |
| 247 | csd_unlock(csd); |
| 248 | func(info); |
| 249 | } |
| 250 | } |
| 251 | |
| 252 | /* |
| 253 | * Handle irq works queued remotely by irq_work_queue_on(). |
| 254 | * Smp functions above are typically synchronous so they |
| 255 | * better run first since some other CPUs may be busy waiting |
| 256 | * for them. |
| 257 | */ |
| 258 | irq_work_run(); |
| 259 | } |
| 260 | |
| 261 | /* |
| 262 | * smp_call_function_single - Run a function on a specific CPU |
| 263 | * @func: The function to run. This must be fast and non-blocking. |
| 264 | * @info: An arbitrary pointer to pass to the function. |
| 265 | * @wait: If true, wait until function has completed on other CPUs. |
| 266 | * |
| 267 | * Returns 0 on success, else a negative status code. |
| 268 | */ |
| 269 | int smp_call_function_single(int cpu, smp_call_func_t func, void *info, |
| 270 | int wait) |
| 271 | { |
| 272 | call_single_data_t *csd; |
| 273 | call_single_data_t csd_stack = { |
| 274 | .flags = CSD_FLAG_LOCK | CSD_FLAG_SYNCHRONOUS, |
| 275 | }; |
| 276 | int this_cpu; |
| 277 | int err; |
| 278 | |
| 279 | /* |
| 280 | * prevent preemption and reschedule on another processor, |
| 281 | * as well as CPU removal |
| 282 | */ |
| 283 | this_cpu = get_cpu(); |
| 284 | |
| 285 | /* |
| 286 | * Can deadlock when called with interrupts disabled. |
| 287 | * We allow cpu's that are not yet online though, as no one else can |
| 288 | * send smp call function interrupt to this cpu and as such deadlocks |
| 289 | * can't happen. |
| 290 | */ |
| 291 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() |
| 292 | && !oops_in_progress); |
| 293 | |
| 294 | /* |
| 295 | * When @wait we can deadlock when we interrupt between llist_add() and |
| 296 | * arch_send_call_function_ipi*(); when !@wait we can deadlock due to |
| 297 | * csd_lock() on because the interrupt context uses the same csd |
| 298 | * storage. |
| 299 | */ |
| 300 | WARN_ON_ONCE(!in_task()); |
| 301 | |
| 302 | csd = &csd_stack; |
| 303 | if (!wait) { |
| 304 | csd = this_cpu_ptr(&csd_data); |
| 305 | csd_lock(csd); |
| 306 | } |
| 307 | |
| 308 | err = generic_exec_single(cpu, csd, func, info); |
| 309 | |
| 310 | if (wait) |
| 311 | csd_lock_wait(csd); |
| 312 | |
| 313 | put_cpu(); |
| 314 | |
| 315 | return err; |
| 316 | } |
| 317 | EXPORT_SYMBOL(smp_call_function_single); |
| 318 | |
| 319 | /** |
| 320 | * smp_call_function_single_async(): Run an asynchronous function on a |
| 321 | * specific CPU. |
| 322 | * @cpu: The CPU to run on. |
| 323 | * @csd: Pre-allocated and setup data structure |
| 324 | * |
| 325 | * Like smp_call_function_single(), but the call is asynchonous and |
| 326 | * can thus be done from contexts with disabled interrupts. |
| 327 | * |
| 328 | * The caller passes his own pre-allocated data structure |
| 329 | * (ie: embedded in an object) and is responsible for synchronizing it |
| 330 | * such that the IPIs performed on the @csd are strictly serialized. |
| 331 | * |
| 332 | * NOTE: Be careful, there is unfortunately no current debugging facility to |
| 333 | * validate the correctness of this serialization. |
| 334 | */ |
| 335 | int smp_call_function_single_async(int cpu, call_single_data_t *csd) |
| 336 | { |
| 337 | int err = 0; |
| 338 | |
| 339 | preempt_disable(); |
| 340 | |
| 341 | /* We could deadlock if we have to wait here with interrupts disabled! */ |
| 342 | if (WARN_ON_ONCE(csd->flags & CSD_FLAG_LOCK)) |
| 343 | csd_lock_wait(csd); |
| 344 | |
| 345 | csd->flags = CSD_FLAG_LOCK; |
| 346 | smp_wmb(); |
| 347 | |
| 348 | err = generic_exec_single(cpu, csd, csd->func, csd->info); |
| 349 | preempt_enable(); |
| 350 | |
| 351 | return err; |
| 352 | } |
| 353 | EXPORT_SYMBOL_GPL(smp_call_function_single_async); |
| 354 | |
| 355 | /* |
| 356 | * smp_call_function_any - Run a function on any of the given cpus |
| 357 | * @mask: The mask of cpus it can run on. |
| 358 | * @func: The function to run. This must be fast and non-blocking. |
| 359 | * @info: An arbitrary pointer to pass to the function. |
| 360 | * @wait: If true, wait until function has completed. |
| 361 | * |
| 362 | * Returns 0 on success, else a negative status code (if no cpus were online). |
| 363 | * |
| 364 | * Selection preference: |
| 365 | * 1) current cpu if in @mask |
| 366 | * 2) any cpu of current node if in @mask |
| 367 | * 3) any other online cpu in @mask |
| 368 | */ |
| 369 | int smp_call_function_any(const struct cpumask *mask, |
| 370 | smp_call_func_t func, void *info, int wait) |
| 371 | { |
| 372 | unsigned int cpu; |
| 373 | const struct cpumask *nodemask; |
| 374 | int ret; |
| 375 | |
| 376 | /* Try for same CPU (cheapest) */ |
| 377 | cpu = get_cpu(); |
| 378 | if (cpumask_test_cpu(cpu, mask)) |
| 379 | goto call; |
| 380 | |
| 381 | /* Try for same node. */ |
| 382 | nodemask = cpumask_of_node(cpu_to_node(cpu)); |
| 383 | for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids; |
| 384 | cpu = cpumask_next_and(cpu, nodemask, mask)) { |
| 385 | if (cpu_online(cpu)) |
| 386 | goto call; |
| 387 | } |
| 388 | |
| 389 | /* Any online will do: smp_call_function_single handles nr_cpu_ids. */ |
| 390 | cpu = cpumask_any_and(mask, cpu_online_mask); |
| 391 | call: |
| 392 | ret = smp_call_function_single(cpu, func, info, wait); |
| 393 | put_cpu(); |
| 394 | return ret; |
| 395 | } |
| 396 | EXPORT_SYMBOL_GPL(smp_call_function_any); |
| 397 | |
| 398 | /** |
| 399 | * smp_call_function_many(): Run a function on a set of other CPUs. |
| 400 | * @mask: The set of cpus to run on (only runs on online subset). |
| 401 | * @func: The function to run. This must be fast and non-blocking. |
| 402 | * @info: An arbitrary pointer to pass to the function. |
| 403 | * @wait: If true, wait (atomically) until function has completed |
| 404 | * on other CPUs. |
| 405 | * |
| 406 | * If @wait is true, then returns once @func has returned. |
| 407 | * |
| 408 | * You must not call this function with disabled interrupts or from a |
| 409 | * hardware interrupt handler or from a bottom half handler. Preemption |
| 410 | * must be disabled when calling this function. |
| 411 | */ |
| 412 | void smp_call_function_many(const struct cpumask *mask, |
| 413 | smp_call_func_t func, void *info, bool wait) |
| 414 | { |
| 415 | struct call_function_data *cfd; |
| 416 | int cpu, next_cpu, this_cpu = smp_processor_id(); |
| 417 | |
| 418 | /* |
| 419 | * Can deadlock when called with interrupts disabled. |
| 420 | * We allow cpu's that are not yet online though, as no one else can |
| 421 | * send smp call function interrupt to this cpu and as such deadlocks |
| 422 | * can't happen. |
| 423 | */ |
| 424 | WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() |
| 425 | && !oops_in_progress && !early_boot_irqs_disabled); |
| 426 | |
| 427 | /* |
| 428 | * When @wait we can deadlock when we interrupt between llist_add() and |
| 429 | * arch_send_call_function_ipi*(); when !@wait we can deadlock due to |
| 430 | * csd_lock() on because the interrupt context uses the same csd |
| 431 | * storage. |
| 432 | */ |
| 433 | WARN_ON_ONCE(!in_task()); |
| 434 | |
| 435 | /* Try to fastpath. So, what's a CPU they want? Ignoring this one. */ |
| 436 | cpu = cpumask_first_and(mask, cpu_online_mask); |
| 437 | if (cpu == this_cpu) |
| 438 | cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
| 439 | |
| 440 | /* No online cpus? We're done. */ |
| 441 | if (cpu >= nr_cpu_ids) |
| 442 | return; |
| 443 | |
| 444 | /* Do we have another CPU which isn't us? */ |
| 445 | next_cpu = cpumask_next_and(cpu, mask, cpu_online_mask); |
| 446 | if (next_cpu == this_cpu) |
| 447 | next_cpu = cpumask_next_and(next_cpu, mask, cpu_online_mask); |
| 448 | |
| 449 | /* Fastpath: do that cpu by itself. */ |
| 450 | if (next_cpu >= nr_cpu_ids) { |
| 451 | smp_call_function_single(cpu, func, info, wait); |
| 452 | return; |
| 453 | } |
| 454 | |
| 455 | cfd = this_cpu_ptr(&cfd_data); |
| 456 | |
| 457 | cpumask_and(cfd->cpumask, mask, cpu_online_mask); |
| 458 | __cpumask_clear_cpu(this_cpu, cfd->cpumask); |
| 459 | |
| 460 | /* Some callers race with other cpus changing the passed mask */ |
| 461 | if (unlikely(!cpumask_weight(cfd->cpumask))) |
| 462 | return; |
| 463 | |
| 464 | cpumask_clear(cfd->cpumask_ipi); |
| 465 | for_each_cpu(cpu, cfd->cpumask) { |
| 466 | call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu); |
| 467 | |
| 468 | csd_lock(csd); |
| 469 | if (wait) |
| 470 | csd->flags |= CSD_FLAG_SYNCHRONOUS; |
| 471 | csd->func = func; |
| 472 | csd->info = info; |
| 473 | if (llist_add(&csd->llist, &per_cpu(call_single_queue, cpu))) |
| 474 | __cpumask_set_cpu(cpu, cfd->cpumask_ipi); |
| 475 | } |
| 476 | |
| 477 | /* Send a message to all CPUs in the map */ |
| 478 | arch_send_call_function_ipi_mask(cfd->cpumask_ipi); |
| 479 | |
| 480 | if (wait) { |
| 481 | for_each_cpu(cpu, cfd->cpumask) { |
| 482 | call_single_data_t *csd; |
| 483 | |
| 484 | csd = per_cpu_ptr(cfd->csd, cpu); |
| 485 | csd_lock_wait(csd); |
| 486 | } |
| 487 | } |
| 488 | } |
| 489 | EXPORT_SYMBOL(smp_call_function_many); |
| 490 | |
| 491 | /** |
| 492 | * smp_call_function(): Run a function on all other CPUs. |
| 493 | * @func: The function to run. This must be fast and non-blocking. |
| 494 | * @info: An arbitrary pointer to pass to the function. |
| 495 | * @wait: If true, wait (atomically) until function has completed |
| 496 | * on other CPUs. |
| 497 | * |
| 498 | * Returns 0. |
| 499 | * |
| 500 | * If @wait is true, then returns once @func has returned; otherwise |
| 501 | * it returns just before the target cpu calls @func. |
| 502 | * |
| 503 | * You must not call this function with disabled interrupts or from a |
| 504 | * hardware interrupt handler or from a bottom half handler. |
| 505 | */ |
| 506 | void smp_call_function(smp_call_func_t func, void *info, int wait) |
| 507 | { |
| 508 | preempt_disable(); |
| 509 | smp_call_function_many(cpu_online_mask, func, info, wait); |
| 510 | preempt_enable(); |
| 511 | } |
| 512 | EXPORT_SYMBOL(smp_call_function); |
| 513 | |
| 514 | /* Setup configured maximum number of CPUs to activate */ |
| 515 | unsigned int setup_max_cpus = NR_CPUS; |
| 516 | EXPORT_SYMBOL(setup_max_cpus); |
| 517 | |
| 518 | |
| 519 | /* |
| 520 | * Setup routine for controlling SMP activation |
| 521 | * |
| 522 | * Command-line option of "nosmp" or "maxcpus=0" will disable SMP |
| 523 | * activation entirely (the MPS table probe still happens, though). |
| 524 | * |
| 525 | * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer |
| 526 | * greater than 0, limits the maximum number of CPUs activated in |
| 527 | * SMP mode to <NUM>. |
| 528 | */ |
| 529 | |
| 530 | void __weak arch_disable_smp_support(void) { } |
| 531 | |
| 532 | static int __init nosmp(char *str) |
| 533 | { |
| 534 | setup_max_cpus = 0; |
| 535 | arch_disable_smp_support(); |
| 536 | |
| 537 | return 0; |
| 538 | } |
| 539 | |
| 540 | early_param("nosmp", nosmp); |
| 541 | |
| 542 | /* this is hard limit */ |
| 543 | static int __init nrcpus(char *str) |
| 544 | { |
| 545 | int nr_cpus; |
| 546 | |
| 547 | get_option(&str, &nr_cpus); |
| 548 | if (nr_cpus > 0 && nr_cpus < nr_cpu_ids) |
| 549 | nr_cpu_ids = nr_cpus; |
| 550 | |
| 551 | return 0; |
| 552 | } |
| 553 | |
| 554 | early_param("nr_cpus", nrcpus); |
| 555 | |
| 556 | static int __init maxcpus(char *str) |
| 557 | { |
| 558 | get_option(&str, &setup_max_cpus); |
| 559 | if (setup_max_cpus == 0) |
| 560 | arch_disable_smp_support(); |
| 561 | |
| 562 | return 0; |
| 563 | } |
| 564 | |
| 565 | early_param("maxcpus", maxcpus); |
| 566 | |
| 567 | /* Setup number of possible processor ids */ |
| 568 | unsigned int nr_cpu_ids __read_mostly = NR_CPUS; |
| 569 | EXPORT_SYMBOL(nr_cpu_ids); |
| 570 | |
| 571 | /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */ |
| 572 | void __init setup_nr_cpu_ids(void) |
| 573 | { |
| 574 | nr_cpu_ids = find_last_bit(cpumask_bits(cpu_possible_mask),NR_CPUS) + 1; |
| 575 | } |
| 576 | |
| 577 | /* Called by boot processor to activate the rest. */ |
| 578 | void __init smp_init(void) |
| 579 | { |
| 580 | int num_nodes, num_cpus; |
| 581 | unsigned int cpu; |
| 582 | |
| 583 | idle_threads_init(); |
| 584 | cpuhp_threads_init(); |
| 585 | |
| 586 | pr_info("Bringing up secondary CPUs ...\n"); |
| 587 | |
| 588 | /* FIXME: This should be done in userspace --RR */ |
| 589 | for_each_present_cpu(cpu) { |
| 590 | if (num_online_cpus() >= setup_max_cpus) |
| 591 | break; |
| 592 | if (!cpu_online(cpu)) |
| 593 | cpu_up(cpu); |
| 594 | } |
| 595 | |
| 596 | num_nodes = num_online_nodes(); |
| 597 | num_cpus = num_online_cpus(); |
| 598 | pr_info("Brought up %d node%s, %d CPU%s\n", |
| 599 | num_nodes, (num_nodes > 1 ? "s" : ""), |
| 600 | num_cpus, (num_cpus > 1 ? "s" : "")); |
| 601 | |
| 602 | /* Any cleanup work */ |
| 603 | smp_cpus_done(setup_max_cpus); |
| 604 | } |
| 605 | |
| 606 | /* |
| 607 | * Call a function on all processors. May be used during early boot while |
| 608 | * early_boot_irqs_disabled is set. Use local_irq_save/restore() instead |
| 609 | * of local_irq_disable/enable(). |
| 610 | */ |
| 611 | void on_each_cpu(void (*func) (void *info), void *info, int wait) |
| 612 | { |
| 613 | unsigned long flags; |
| 614 | |
| 615 | preempt_disable(); |
| 616 | smp_call_function(func, info, wait); |
| 617 | local_irq_save(flags); |
| 618 | func(info); |
| 619 | local_irq_restore(flags); |
| 620 | preempt_enable(); |
| 621 | } |
| 622 | EXPORT_SYMBOL(on_each_cpu); |
| 623 | |
| 624 | /** |
| 625 | * on_each_cpu_mask(): Run a function on processors specified by |
| 626 | * cpumask, which may include the local processor. |
| 627 | * @mask: The set of cpus to run on (only runs on online subset). |
| 628 | * @func: The function to run. This must be fast and non-blocking. |
| 629 | * @info: An arbitrary pointer to pass to the function. |
| 630 | * @wait: If true, wait (atomically) until function has completed |
| 631 | * on other CPUs. |
| 632 | * |
| 633 | * If @wait is true, then returns once @func has returned. |
| 634 | * |
| 635 | * You must not call this function with disabled interrupts or from a |
| 636 | * hardware interrupt handler or from a bottom half handler. The |
| 637 | * exception is that it may be used during early boot while |
| 638 | * early_boot_irqs_disabled is set. |
| 639 | */ |
| 640 | void on_each_cpu_mask(const struct cpumask *mask, smp_call_func_t func, |
| 641 | void *info, bool wait) |
| 642 | { |
| 643 | int cpu = get_cpu(); |
| 644 | |
| 645 | smp_call_function_many(mask, func, info, wait); |
| 646 | if (cpumask_test_cpu(cpu, mask)) { |
| 647 | unsigned long flags; |
| 648 | local_irq_save(flags); |
| 649 | func(info); |
| 650 | local_irq_restore(flags); |
| 651 | } |
| 652 | put_cpu(); |
| 653 | } |
| 654 | EXPORT_SYMBOL(on_each_cpu_mask); |
| 655 | |
| 656 | /* |
| 657 | * on_each_cpu_cond(): Call a function on each processor for which |
| 658 | * the supplied function cond_func returns true, optionally waiting |
| 659 | * for all the required CPUs to finish. This may include the local |
| 660 | * processor. |
| 661 | * @cond_func: A callback function that is passed a cpu id and |
| 662 | * the the info parameter. The function is called |
| 663 | * with preemption disabled. The function should |
| 664 | * return a blooean value indicating whether to IPI |
| 665 | * the specified CPU. |
| 666 | * @func: The function to run on all applicable CPUs. |
| 667 | * This must be fast and non-blocking. |
| 668 | * @info: An arbitrary pointer to pass to both functions. |
| 669 | * @wait: If true, wait (atomically) until function has |
| 670 | * completed on other CPUs. |
| 671 | * @gfp_flags: GFP flags to use when allocating the cpumask |
| 672 | * used internally by the function. |
| 673 | * |
| 674 | * The function might sleep if the GFP flags indicates a non |
| 675 | * atomic allocation is allowed. |
| 676 | * |
| 677 | * Preemption is disabled to protect against CPUs going offline but not online. |
| 678 | * CPUs going online during the call will not be seen or sent an IPI. |
| 679 | * |
| 680 | * You must not call this function with disabled interrupts or |
| 681 | * from a hardware interrupt handler or from a bottom half handler. |
| 682 | */ |
| 683 | void on_each_cpu_cond_mask(bool (*cond_func)(int cpu, void *info), |
| 684 | smp_call_func_t func, void *info, bool wait, |
| 685 | gfp_t gfp_flags, const struct cpumask *mask) |
| 686 | { |
| 687 | cpumask_var_t cpus; |
| 688 | int cpu, ret; |
| 689 | |
| 690 | might_sleep_if(gfpflags_allow_blocking(gfp_flags)); |
| 691 | |
| 692 | if (likely(zalloc_cpumask_var(&cpus, (gfp_flags|__GFP_NOWARN)))) { |
| 693 | preempt_disable(); |
| 694 | for_each_cpu(cpu, mask) |
| 695 | if (cond_func(cpu, info)) |
| 696 | __cpumask_set_cpu(cpu, cpus); |
| 697 | on_each_cpu_mask(cpus, func, info, wait); |
| 698 | preempt_enable(); |
| 699 | free_cpumask_var(cpus); |
| 700 | } else { |
| 701 | /* |
| 702 | * No free cpumask, bother. No matter, we'll |
| 703 | * just have to IPI them one by one. |
| 704 | */ |
| 705 | preempt_disable(); |
| 706 | for_each_cpu(cpu, mask) |
| 707 | if (cond_func(cpu, info)) { |
| 708 | ret = smp_call_function_single(cpu, func, |
| 709 | info, wait); |
| 710 | WARN_ON_ONCE(ret); |
| 711 | } |
| 712 | preempt_enable(); |
| 713 | } |
| 714 | } |
| 715 | EXPORT_SYMBOL(on_each_cpu_cond_mask); |
| 716 | |
| 717 | void on_each_cpu_cond(bool (*cond_func)(int cpu, void *info), |
| 718 | smp_call_func_t func, void *info, bool wait, |
| 719 | gfp_t gfp_flags) |
| 720 | { |
| 721 | on_each_cpu_cond_mask(cond_func, func, info, wait, gfp_flags, |
| 722 | cpu_online_mask); |
| 723 | } |
| 724 | EXPORT_SYMBOL(on_each_cpu_cond); |
| 725 | |
| 726 | static void do_nothing(void *unused) |
| 727 | { |
| 728 | } |
| 729 | |
| 730 | /** |
| 731 | * kick_all_cpus_sync - Force all cpus out of idle |
| 732 | * |
| 733 | * Used to synchronize the update of pm_idle function pointer. It's |
| 734 | * called after the pointer is updated and returns after the dummy |
| 735 | * callback function has been executed on all cpus. The execution of |
| 736 | * the function can only happen on the remote cpus after they have |
| 737 | * left the idle function which had been called via pm_idle function |
| 738 | * pointer. So it's guaranteed that nothing uses the previous pointer |
| 739 | * anymore. |
| 740 | */ |
| 741 | void kick_all_cpus_sync(void) |
| 742 | { |
| 743 | /* Make sure the change is visible before we kick the cpus */ |
| 744 | smp_mb(); |
| 745 | smp_call_function(do_nothing, NULL, 1); |
| 746 | } |
| 747 | EXPORT_SYMBOL_GPL(kick_all_cpus_sync); |
| 748 | |
| 749 | /** |
| 750 | * wake_up_all_idle_cpus - break all cpus out of idle |
| 751 | * wake_up_all_idle_cpus try to break all cpus which is in idle state even |
| 752 | * including idle polling cpus, for non-idle cpus, we will do nothing |
| 753 | * for them. |
| 754 | */ |
| 755 | void wake_up_all_idle_cpus(void) |
| 756 | { |
| 757 | int cpu; |
| 758 | |
| 759 | preempt_disable(); |
| 760 | for_each_online_cpu(cpu) { |
| 761 | if (cpu == smp_processor_id()) |
| 762 | continue; |
| 763 | |
| 764 | wake_up_if_idle(cpu); |
| 765 | } |
| 766 | preempt_enable(); |
| 767 | } |
| 768 | EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus); |
| 769 | |
| 770 | /** |
| 771 | * smp_call_on_cpu - Call a function on a specific cpu |
| 772 | * |
| 773 | * Used to call a function on a specific cpu and wait for it to return. |
| 774 | * Optionally make sure the call is done on a specified physical cpu via vcpu |
| 775 | * pinning in order to support virtualized environments. |
| 776 | */ |
| 777 | struct smp_call_on_cpu_struct { |
| 778 | struct work_struct work; |
| 779 | struct completion done; |
| 780 | int (*func)(void *); |
| 781 | void *data; |
| 782 | int ret; |
| 783 | int cpu; |
| 784 | }; |
| 785 | |
| 786 | static void smp_call_on_cpu_callback(struct work_struct *work) |
| 787 | { |
| 788 | struct smp_call_on_cpu_struct *sscs; |
| 789 | |
| 790 | sscs = container_of(work, struct smp_call_on_cpu_struct, work); |
| 791 | if (sscs->cpu >= 0) |
| 792 | hypervisor_pin_vcpu(sscs->cpu); |
| 793 | sscs->ret = sscs->func(sscs->data); |
| 794 | if (sscs->cpu >= 0) |
| 795 | hypervisor_pin_vcpu(-1); |
| 796 | |
| 797 | complete(&sscs->done); |
| 798 | } |
| 799 | |
| 800 | int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys) |
| 801 | { |
| 802 | struct smp_call_on_cpu_struct sscs = { |
| 803 | .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done), |
| 804 | .func = func, |
| 805 | .data = par, |
| 806 | .cpu = phys ? cpu : -1, |
| 807 | }; |
| 808 | |
| 809 | INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback); |
| 810 | |
| 811 | if (cpu >= nr_cpu_ids || !cpu_online(cpu)) |
| 812 | return -ENXIO; |
| 813 | |
| 814 | queue_work_on(cpu, system_wq, &sscs.work); |
| 815 | wait_for_completion(&sscs.done); |
| 816 | |
| 817 | return sscs.ret; |
| 818 | } |
| 819 | EXPORT_SYMBOL_GPL(smp_call_on_cpu); |