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/interrupt.h> 18 #include <linux/gfp.h> 19 #include <linux/smp.h> 20 #include <linux/cpu.h> 21 #include <linux/sched.h> 22 #include <linux/sched/idle.h> 23 #include <linux/hypervisor.h> 24 #include <linux/sched/clock.h> 25 #include <linux/nmi.h> 26 #include <linux/sched/debug.h> 27 #include <linux/jump_label.h> 28 29 #include <trace/events/ipi.h> 30 #define CREATE_TRACE_POINTS 31 #include <trace/events/csd.h> 32 #undef CREATE_TRACE_POINTS 33 34 #include "smpboot.h" 35 #include "sched/smp.h" 36 37 #define CSD_TYPE(_csd) ((_csd)->node.u_flags & CSD_FLAG_TYPE_MASK) 38 39 struct call_function_data { 40 call_single_data_t __percpu *csd; 41 cpumask_var_t cpumask; 42 cpumask_var_t cpumask_ipi; 43 }; 44 45 static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data); 46 47 static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue); 48 49 static DEFINE_PER_CPU(atomic_t, trigger_backtrace) = ATOMIC_INIT(1); 50 51 static void __flush_smp_call_function_queue(bool warn_cpu_offline); 52 53 int smpcfd_prepare_cpu(unsigned int cpu) 54 { 55 struct call_function_data *cfd = &per_cpu(cfd_data, cpu); 56 57 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, 58 cpu_to_node(cpu))) 59 return -ENOMEM; 60 if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, 61 cpu_to_node(cpu))) { 62 free_cpumask_var(cfd->cpumask); 63 return -ENOMEM; 64 } 65 cfd->csd = alloc_percpu(call_single_data_t); 66 if (!cfd->csd) { 67 free_cpumask_var(cfd->cpumask); 68 free_cpumask_var(cfd->cpumask_ipi); 69 return -ENOMEM; 70 } 71 72 return 0; 73 } 74 75 int smpcfd_dead_cpu(unsigned int cpu) 76 { 77 struct call_function_data *cfd = &per_cpu(cfd_data, cpu); 78 79 free_cpumask_var(cfd->cpumask); 80 free_cpumask_var(cfd->cpumask_ipi); 81 free_percpu(cfd->csd); 82 return 0; 83 } 84 85 int smpcfd_dying_cpu(unsigned int cpu) 86 { 87 /* 88 * The IPIs for the smp-call-function callbacks queued by other 89 * CPUs might arrive late, either due to hardware latencies or 90 * because this CPU disabled interrupts (inside stop-machine) 91 * before the IPIs were sent. So flush out any pending callbacks 92 * explicitly (without waiting for the IPIs to arrive), to 93 * ensure that the outgoing CPU doesn't go offline with work 94 * still pending. 95 */ 96 __flush_smp_call_function_queue(false); 97 irq_work_run(); 98 return 0; 99 } 100 101 void __init call_function_init(void) 102 { 103 int i; 104 105 for_each_possible_cpu(i) 106 init_llist_head(&per_cpu(call_single_queue, i)); 107 108 smpcfd_prepare_cpu(smp_processor_id()); 109 } 110 111 static __always_inline void 112 send_call_function_single_ipi(int cpu) 113 { 114 if (call_function_single_prep_ipi(cpu)) { 115 trace_ipi_send_cpu(cpu, _RET_IP_, 116 generic_smp_call_function_single_interrupt); 117 arch_send_call_function_single_ipi(cpu); 118 } 119 } 120 121 static __always_inline void 122 send_call_function_ipi_mask(struct cpumask *mask) 123 { 124 trace_ipi_send_cpumask(mask, _RET_IP_, 125 generic_smp_call_function_single_interrupt); 126 arch_send_call_function_ipi_mask(mask); 127 } 128 129 static __always_inline void 130 csd_do_func(smp_call_func_t func, void *info, call_single_data_t *csd) 131 { 132 trace_csd_function_entry(func, csd); 133 func(info); 134 trace_csd_function_exit(func, csd); 135 } 136 137 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 138 139 static DEFINE_STATIC_KEY_MAYBE(CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT, csdlock_debug_enabled); 140 141 /* 142 * Parse the csdlock_debug= kernel boot parameter. 143 * 144 * If you need to restore the old "ext" value that once provided 145 * additional debugging information, reapply the following commits: 146 * 147 * de7b09ef658d ("locking/csd_lock: Prepare more CSD lock debugging") 148 * a5aabace5fb8 ("locking/csd_lock: Add more data to CSD lock debugging") 149 */ 150 static int __init csdlock_debug(char *str) 151 { 152 int ret; 153 unsigned int val = 0; 154 155 ret = get_option(&str, &val); 156 if (ret) { 157 if (val) 158 static_branch_enable(&csdlock_debug_enabled); 159 else 160 static_branch_disable(&csdlock_debug_enabled); 161 } 162 163 return 1; 164 } 165 __setup("csdlock_debug=", csdlock_debug); 166 167 static DEFINE_PER_CPU(call_single_data_t *, cur_csd); 168 static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func); 169 static DEFINE_PER_CPU(void *, cur_csd_info); 170 171 static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */ 172 module_param(csd_lock_timeout, ulong, 0444); 173 static int panic_on_ipistall; /* CSD panic timeout in milliseconds, 300000 for five minutes. */ 174 module_param(panic_on_ipistall, int, 0444); 175 176 static atomic_t csd_bug_count = ATOMIC_INIT(0); 177 178 /* Record current CSD work for current CPU, NULL to erase. */ 179 static void __csd_lock_record(call_single_data_t *csd) 180 { 181 if (!csd) { 182 smp_mb(); /* NULL cur_csd after unlock. */ 183 __this_cpu_write(cur_csd, NULL); 184 return; 185 } 186 __this_cpu_write(cur_csd_func, csd->func); 187 __this_cpu_write(cur_csd_info, csd->info); 188 smp_wmb(); /* func and info before csd. */ 189 __this_cpu_write(cur_csd, csd); 190 smp_mb(); /* Update cur_csd before function call. */ 191 /* Or before unlock, as the case may be. */ 192 } 193 194 static __always_inline void csd_lock_record(call_single_data_t *csd) 195 { 196 if (static_branch_unlikely(&csdlock_debug_enabled)) 197 __csd_lock_record(csd); 198 } 199 200 static int csd_lock_wait_getcpu(call_single_data_t *csd) 201 { 202 unsigned int csd_type; 203 204 csd_type = CSD_TYPE(csd); 205 if (csd_type == CSD_TYPE_ASYNC || csd_type == CSD_TYPE_SYNC) 206 return csd->node.dst; /* Other CSD_TYPE_ values might not have ->dst. */ 207 return -1; 208 } 209 210 /* 211 * Complain if too much time spent waiting. Note that only 212 * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU, 213 * so waiting on other types gets much less information. 214 */ 215 static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, int *bug_id) 216 { 217 int cpu = -1; 218 int cpux; 219 bool firsttime; 220 u64 ts2, ts_delta; 221 call_single_data_t *cpu_cur_csd; 222 unsigned int flags = READ_ONCE(csd->node.u_flags); 223 unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC; 224 225 if (!(flags & CSD_FLAG_LOCK)) { 226 if (!unlikely(*bug_id)) 227 return true; 228 cpu = csd_lock_wait_getcpu(csd); 229 pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n", 230 *bug_id, raw_smp_processor_id(), cpu); 231 return true; 232 } 233 234 ts2 = sched_clock(); 235 /* How long since we last checked for a stuck CSD lock.*/ 236 ts_delta = ts2 - *ts1; 237 if (likely(ts_delta <= csd_lock_timeout_ns || csd_lock_timeout_ns == 0)) 238 return false; 239 240 firsttime = !*bug_id; 241 if (firsttime) 242 *bug_id = atomic_inc_return(&csd_bug_count); 243 cpu = csd_lock_wait_getcpu(csd); 244 if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu)) 245 cpux = 0; 246 else 247 cpux = cpu; 248 cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */ 249 /* How long since this CSD lock was stuck. */ 250 ts_delta = ts2 - ts0; 251 pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %llu ns for CPU#%02d %pS(%ps).\n", 252 firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), ts_delta, 253 cpu, csd->func, csd->info); 254 /* 255 * If the CSD lock is still stuck after 5 minutes, it is unlikely 256 * to become unstuck. Use a signed comparison to avoid triggering 257 * on underflows when the TSC is out of sync between sockets. 258 */ 259 BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC)); 260 if (cpu_cur_csd && csd != cpu_cur_csd) { 261 pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n", 262 *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)), 263 READ_ONCE(per_cpu(cur_csd_info, cpux))); 264 } else { 265 pr_alert("\tcsd: CSD lock (#%d) %s.\n", 266 *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request"); 267 } 268 if (cpu >= 0) { 269 if (atomic_cmpxchg_acquire(&per_cpu(trigger_backtrace, cpu), 1, 0)) 270 dump_cpu_task(cpu); 271 if (!cpu_cur_csd) { 272 pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu); 273 arch_send_call_function_single_ipi(cpu); 274 } 275 } 276 if (firsttime) 277 dump_stack(); 278 *ts1 = ts2; 279 280 return false; 281 } 282 283 /* 284 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources 285 * 286 * For non-synchronous ipi calls the csd can still be in use by the 287 * previous function call. For multi-cpu calls its even more interesting 288 * as we'll have to ensure no other cpu is observing our csd. 289 */ 290 static void __csd_lock_wait(call_single_data_t *csd) 291 { 292 int bug_id = 0; 293 u64 ts0, ts1; 294 295 ts1 = ts0 = sched_clock(); 296 for (;;) { 297 if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id)) 298 break; 299 cpu_relax(); 300 } 301 smp_acquire__after_ctrl_dep(); 302 } 303 304 static __always_inline void csd_lock_wait(call_single_data_t *csd) 305 { 306 if (static_branch_unlikely(&csdlock_debug_enabled)) { 307 __csd_lock_wait(csd); 308 return; 309 } 310 311 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); 312 } 313 #else 314 static void csd_lock_record(call_single_data_t *csd) 315 { 316 } 317 318 static __always_inline void csd_lock_wait(call_single_data_t *csd) 319 { 320 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); 321 } 322 #endif 323 324 static __always_inline void csd_lock(call_single_data_t *csd) 325 { 326 csd_lock_wait(csd); 327 csd->node.u_flags |= CSD_FLAG_LOCK; 328 329 /* 330 * prevent CPU from reordering the above assignment 331 * to ->flags with any subsequent assignments to other 332 * fields of the specified call_single_data_t structure: 333 */ 334 smp_wmb(); 335 } 336 337 static __always_inline void csd_unlock(call_single_data_t *csd) 338 { 339 WARN_ON(!(csd->node.u_flags & CSD_FLAG_LOCK)); 340 341 /* 342 * ensure we're all done before releasing data: 343 */ 344 smp_store_release(&csd->node.u_flags, 0); 345 } 346 347 static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data); 348 349 void __smp_call_single_queue(int cpu, struct llist_node *node) 350 { 351 /* 352 * We have to check the type of the CSD before queueing it, because 353 * once queued it can have its flags cleared by 354 * flush_smp_call_function_queue() 355 * even if we haven't sent the smp_call IPI yet (e.g. the stopper 356 * executes migration_cpu_stop() on the remote CPU). 357 */ 358 if (trace_csd_queue_cpu_enabled()) { 359 call_single_data_t *csd; 360 smp_call_func_t func; 361 362 csd = container_of(node, call_single_data_t, node.llist); 363 func = CSD_TYPE(csd) == CSD_TYPE_TTWU ? 364 sched_ttwu_pending : csd->func; 365 366 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); 367 } 368 369 /* 370 * The list addition should be visible to the target CPU when it pops 371 * the head of the list to pull the entry off it in the IPI handler 372 * because of normal cache coherency rules implied by the underlying 373 * llist ops. 374 * 375 * If IPIs can go out of order to the cache coherency protocol 376 * in an architecture, sufficient synchronisation should be added 377 * to arch code to make it appear to obey cache coherency WRT 378 * locking and barrier primitives. Generic code isn't really 379 * equipped to do the right thing... 380 */ 381 if (llist_add(node, &per_cpu(call_single_queue, cpu))) 382 send_call_function_single_ipi(cpu); 383 } 384 385 /* 386 * Insert a previously allocated call_single_data_t element 387 * for execution on the given CPU. data must already have 388 * ->func, ->info, and ->flags set. 389 */ 390 static int generic_exec_single(int cpu, call_single_data_t *csd) 391 { 392 if (cpu == smp_processor_id()) { 393 smp_call_func_t func = csd->func; 394 void *info = csd->info; 395 unsigned long flags; 396 397 /* 398 * We can unlock early even for the synchronous on-stack case, 399 * since we're doing this from the same CPU.. 400 */ 401 csd_lock_record(csd); 402 csd_unlock(csd); 403 local_irq_save(flags); 404 csd_do_func(func, info, NULL); 405 csd_lock_record(NULL); 406 local_irq_restore(flags); 407 return 0; 408 } 409 410 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) { 411 csd_unlock(csd); 412 return -ENXIO; 413 } 414 415 __smp_call_single_queue(cpu, &csd->node.llist); 416 417 return 0; 418 } 419 420 /** 421 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks 422 * 423 * Invoked by arch to handle an IPI for call function single. 424 * Must be called with interrupts disabled. 425 */ 426 void generic_smp_call_function_single_interrupt(void) 427 { 428 __flush_smp_call_function_queue(true); 429 } 430 431 /** 432 * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks 433 * 434 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an 435 * offline CPU. Skip this check if set to 'false'. 436 * 437 * Flush any pending smp-call-function callbacks queued on this CPU. This is 438 * invoked by the generic IPI handler, as well as by a CPU about to go offline, 439 * to ensure that all pending IPI callbacks are run before it goes completely 440 * offline. 441 * 442 * Loop through the call_single_queue and run all the queued callbacks. 443 * Must be called with interrupts disabled. 444 */ 445 static void __flush_smp_call_function_queue(bool warn_cpu_offline) 446 { 447 call_single_data_t *csd, *csd_next; 448 struct llist_node *entry, *prev; 449 struct llist_head *head; 450 static bool warned; 451 atomic_t *tbt; 452 453 lockdep_assert_irqs_disabled(); 454 455 /* Allow waiters to send backtrace NMI from here onwards */ 456 tbt = this_cpu_ptr(&trigger_backtrace); 457 atomic_set_release(tbt, 1); 458 459 head = this_cpu_ptr(&call_single_queue); 460 entry = llist_del_all(head); 461 entry = llist_reverse_order(entry); 462 463 /* There shouldn't be any pending callbacks on an offline CPU. */ 464 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) && 465 !warned && entry != NULL)) { 466 warned = true; 467 WARN(1, "IPI on offline CPU %d\n", smp_processor_id()); 468 469 /* 470 * We don't have to use the _safe() variant here 471 * because we are not invoking the IPI handlers yet. 472 */ 473 llist_for_each_entry(csd, entry, node.llist) { 474 switch (CSD_TYPE(csd)) { 475 case CSD_TYPE_ASYNC: 476 case CSD_TYPE_SYNC: 477 case CSD_TYPE_IRQ_WORK: 478 pr_warn("IPI callback %pS sent to offline CPU\n", 479 csd->func); 480 break; 481 482 case CSD_TYPE_TTWU: 483 pr_warn("IPI task-wakeup sent to offline CPU\n"); 484 break; 485 486 default: 487 pr_warn("IPI callback, unknown type %d, sent to offline CPU\n", 488 CSD_TYPE(csd)); 489 break; 490 } 491 } 492 } 493 494 /* 495 * First; run all SYNC callbacks, people are waiting for us. 496 */ 497 prev = NULL; 498 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { 499 /* Do we wait until *after* callback? */ 500 if (CSD_TYPE(csd) == CSD_TYPE_SYNC) { 501 smp_call_func_t func = csd->func; 502 void *info = csd->info; 503 504 if (prev) { 505 prev->next = &csd_next->node.llist; 506 } else { 507 entry = &csd_next->node.llist; 508 } 509 510 csd_lock_record(csd); 511 csd_do_func(func, info, csd); 512 csd_unlock(csd); 513 csd_lock_record(NULL); 514 } else { 515 prev = &csd->node.llist; 516 } 517 } 518 519 if (!entry) 520 return; 521 522 /* 523 * Second; run all !SYNC callbacks. 524 */ 525 prev = NULL; 526 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { 527 int type = CSD_TYPE(csd); 528 529 if (type != CSD_TYPE_TTWU) { 530 if (prev) { 531 prev->next = &csd_next->node.llist; 532 } else { 533 entry = &csd_next->node.llist; 534 } 535 536 if (type == CSD_TYPE_ASYNC) { 537 smp_call_func_t func = csd->func; 538 void *info = csd->info; 539 540 csd_lock_record(csd); 541 csd_unlock(csd); 542 csd_do_func(func, info, csd); 543 csd_lock_record(NULL); 544 } else if (type == CSD_TYPE_IRQ_WORK) { 545 irq_work_single(csd); 546 } 547 548 } else { 549 prev = &csd->node.llist; 550 } 551 } 552 553 /* 554 * Third; only CSD_TYPE_TTWU is left, issue those. 555 */ 556 if (entry) { 557 csd = llist_entry(entry, typeof(*csd), node.llist); 558 csd_do_func(sched_ttwu_pending, entry, csd); 559 } 560 } 561 562 563 /** 564 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks 565 * from task context (idle, migration thread) 566 * 567 * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it 568 * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by 569 * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to 570 * handle queued SMP function calls before scheduling. 571 * 572 * The migration thread has to ensure that an eventually pending wakeup has 573 * been handled before it migrates a task. 574 */ 575 void flush_smp_call_function_queue(void) 576 { 577 unsigned int was_pending; 578 unsigned long flags; 579 580 if (llist_empty(this_cpu_ptr(&call_single_queue))) 581 return; 582 583 local_irq_save(flags); 584 /* Get the already pending soft interrupts for RT enabled kernels */ 585 was_pending = local_softirq_pending(); 586 __flush_smp_call_function_queue(true); 587 if (local_softirq_pending()) 588 do_softirq_post_smp_call_flush(was_pending); 589 590 local_irq_restore(flags); 591 } 592 593 /* 594 * smp_call_function_single - Run a function on a specific CPU 595 * @func: The function to run. This must be fast and non-blocking. 596 * @info: An arbitrary pointer to pass to the function. 597 * @wait: If true, wait until function has completed on other CPUs. 598 * 599 * Returns 0 on success, else a negative status code. 600 */ 601 int smp_call_function_single(int cpu, smp_call_func_t func, void *info, 602 int wait) 603 { 604 call_single_data_t *csd; 605 call_single_data_t csd_stack = { 606 .node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, }, 607 }; 608 int this_cpu; 609 int err; 610 611 /* 612 * prevent preemption and reschedule on another processor, 613 * as well as CPU removal 614 */ 615 this_cpu = get_cpu(); 616 617 /* 618 * Can deadlock when called with interrupts disabled. 619 * We allow cpu's that are not yet online though, as no one else can 620 * send smp call function interrupt to this cpu and as such deadlocks 621 * can't happen. 622 */ 623 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() 624 && !oops_in_progress); 625 626 /* 627 * When @wait we can deadlock when we interrupt between llist_add() and 628 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to 629 * csd_lock() on because the interrupt context uses the same csd 630 * storage. 631 */ 632 WARN_ON_ONCE(!in_task()); 633 634 csd = &csd_stack; 635 if (!wait) { 636 csd = this_cpu_ptr(&csd_data); 637 csd_lock(csd); 638 } 639 640 csd->func = func; 641 csd->info = info; 642 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 643 csd->node.src = smp_processor_id(); 644 csd->node.dst = cpu; 645 #endif 646 647 err = generic_exec_single(cpu, csd); 648 649 if (wait) 650 csd_lock_wait(csd); 651 652 put_cpu(); 653 654 return err; 655 } 656 EXPORT_SYMBOL(smp_call_function_single); 657 658 /** 659 * smp_call_function_single_async() - Run an asynchronous function on a 660 * specific CPU. 661 * @cpu: The CPU to run on. 662 * @csd: Pre-allocated and setup data structure 663 * 664 * Like smp_call_function_single(), but the call is asynchonous and 665 * can thus be done from contexts with disabled interrupts. 666 * 667 * The caller passes his own pre-allocated data structure 668 * (ie: embedded in an object) and is responsible for synchronizing it 669 * such that the IPIs performed on the @csd are strictly serialized. 670 * 671 * If the function is called with one csd which has not yet been 672 * processed by previous call to smp_call_function_single_async(), the 673 * function will return immediately with -EBUSY showing that the csd 674 * object is still in progress. 675 * 676 * NOTE: Be careful, there is unfortunately no current debugging facility to 677 * validate the correctness of this serialization. 678 * 679 * Return: %0 on success or negative errno value on error 680 */ 681 int smp_call_function_single_async(int cpu, call_single_data_t *csd) 682 { 683 int err = 0; 684 685 preempt_disable(); 686 687 if (csd->node.u_flags & CSD_FLAG_LOCK) { 688 err = -EBUSY; 689 goto out; 690 } 691 692 csd->node.u_flags = CSD_FLAG_LOCK; 693 smp_wmb(); 694 695 err = generic_exec_single(cpu, csd); 696 697 out: 698 preempt_enable(); 699 700 return err; 701 } 702 EXPORT_SYMBOL_GPL(smp_call_function_single_async); 703 704 /* 705 * smp_call_function_any - Run a function on any of the given cpus 706 * @mask: The mask of cpus it can run on. 707 * @func: The function to run. This must be fast and non-blocking. 708 * @info: An arbitrary pointer to pass to the function. 709 * @wait: If true, wait until function has completed. 710 * 711 * Returns 0 on success, else a negative status code (if no cpus were online). 712 * 713 * Selection preference: 714 * 1) current cpu if in @mask 715 * 2) any cpu of current node if in @mask 716 * 3) any other online cpu in @mask 717 */ 718 int smp_call_function_any(const struct cpumask *mask, 719 smp_call_func_t func, void *info, int wait) 720 { 721 unsigned int cpu; 722 const struct cpumask *nodemask; 723 int ret; 724 725 /* Try for same CPU (cheapest) */ 726 cpu = get_cpu(); 727 if (cpumask_test_cpu(cpu, mask)) 728 goto call; 729 730 /* Try for same node. */ 731 nodemask = cpumask_of_node(cpu_to_node(cpu)); 732 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids; 733 cpu = cpumask_next_and(cpu, nodemask, mask)) { 734 if (cpu_online(cpu)) 735 goto call; 736 } 737 738 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */ 739 cpu = cpumask_any_and(mask, cpu_online_mask); 740 call: 741 ret = smp_call_function_single(cpu, func, info, wait); 742 put_cpu(); 743 return ret; 744 } 745 EXPORT_SYMBOL_GPL(smp_call_function_any); 746 747 /* 748 * Flags to be used as scf_flags argument of smp_call_function_many_cond(). 749 * 750 * %SCF_WAIT: Wait until function execution is completed 751 * %SCF_RUN_LOCAL: Run also locally if local cpu is set in cpumask 752 */ 753 #define SCF_WAIT (1U << 0) 754 #define SCF_RUN_LOCAL (1U << 1) 755 756 static void smp_call_function_many_cond(const struct cpumask *mask, 757 smp_call_func_t func, void *info, 758 unsigned int scf_flags, 759 smp_cond_func_t cond_func) 760 { 761 int cpu, last_cpu, this_cpu = smp_processor_id(); 762 struct call_function_data *cfd; 763 bool wait = scf_flags & SCF_WAIT; 764 int nr_cpus = 0; 765 bool run_remote = false; 766 bool run_local = false; 767 768 lockdep_assert_preemption_disabled(); 769 770 /* 771 * Can deadlock when called with interrupts disabled. 772 * We allow cpu's that are not yet online though, as no one else can 773 * send smp call function interrupt to this cpu and as such deadlocks 774 * can't happen. 775 */ 776 if (cpu_online(this_cpu) && !oops_in_progress && 777 !early_boot_irqs_disabled) 778 lockdep_assert_irqs_enabled(); 779 780 /* 781 * When @wait we can deadlock when we interrupt between llist_add() and 782 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to 783 * csd_lock() on because the interrupt context uses the same csd 784 * storage. 785 */ 786 WARN_ON_ONCE(!in_task()); 787 788 /* Check if we need local execution. */ 789 if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask)) 790 run_local = true; 791 792 /* Check if we need remote execution, i.e., any CPU excluding this one. */ 793 cpu = cpumask_first_and(mask, cpu_online_mask); 794 if (cpu == this_cpu) 795 cpu = cpumask_next_and(cpu, mask, cpu_online_mask); 796 if (cpu < nr_cpu_ids) 797 run_remote = true; 798 799 if (run_remote) { 800 cfd = this_cpu_ptr(&cfd_data); 801 cpumask_and(cfd->cpumask, mask, cpu_online_mask); 802 __cpumask_clear_cpu(this_cpu, cfd->cpumask); 803 804 cpumask_clear(cfd->cpumask_ipi); 805 for_each_cpu(cpu, cfd->cpumask) { 806 call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu); 807 808 if (cond_func && !cond_func(cpu, info)) { 809 __cpumask_clear_cpu(cpu, cfd->cpumask); 810 continue; 811 } 812 813 csd_lock(csd); 814 if (wait) 815 csd->node.u_flags |= CSD_TYPE_SYNC; 816 csd->func = func; 817 csd->info = info; 818 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 819 csd->node.src = smp_processor_id(); 820 csd->node.dst = cpu; 821 #endif 822 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); 823 824 if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) { 825 __cpumask_set_cpu(cpu, cfd->cpumask_ipi); 826 nr_cpus++; 827 last_cpu = cpu; 828 } 829 } 830 831 /* 832 * Choose the most efficient way to send an IPI. Note that the 833 * number of CPUs might be zero due to concurrent changes to the 834 * provided mask. 835 */ 836 if (nr_cpus == 1) 837 send_call_function_single_ipi(last_cpu); 838 else if (likely(nr_cpus > 1)) 839 send_call_function_ipi_mask(cfd->cpumask_ipi); 840 } 841 842 if (run_local && (!cond_func || cond_func(this_cpu, info))) { 843 unsigned long flags; 844 845 local_irq_save(flags); 846 csd_do_func(func, info, NULL); 847 local_irq_restore(flags); 848 } 849 850 if (run_remote && wait) { 851 for_each_cpu(cpu, cfd->cpumask) { 852 call_single_data_t *csd; 853 854 csd = per_cpu_ptr(cfd->csd, cpu); 855 csd_lock_wait(csd); 856 } 857 } 858 } 859 860 /** 861 * smp_call_function_many(): Run a function on a set of CPUs. 862 * @mask: The set of cpus to run on (only runs on online subset). 863 * @func: The function to run. This must be fast and non-blocking. 864 * @info: An arbitrary pointer to pass to the function. 865 * @wait: Bitmask that controls the operation. If %SCF_WAIT is set, wait 866 * (atomically) until function has completed on other CPUs. If 867 * %SCF_RUN_LOCAL is set, the function will also be run locally 868 * if the local CPU is set in the @cpumask. 869 * 870 * If @wait is true, then returns once @func has returned. 871 * 872 * You must not call this function with disabled interrupts or from a 873 * hardware interrupt handler or from a bottom half handler. Preemption 874 * must be disabled when calling this function. 875 */ 876 void smp_call_function_many(const struct cpumask *mask, 877 smp_call_func_t func, void *info, bool wait) 878 { 879 smp_call_function_many_cond(mask, func, info, wait * SCF_WAIT, NULL); 880 } 881 EXPORT_SYMBOL(smp_call_function_many); 882 883 /** 884 * smp_call_function(): Run a function on all other CPUs. 885 * @func: The function to run. This must be fast and non-blocking. 886 * @info: An arbitrary pointer to pass to the function. 887 * @wait: If true, wait (atomically) until function has completed 888 * on other CPUs. 889 * 890 * Returns 0. 891 * 892 * If @wait is true, then returns once @func has returned; otherwise 893 * it returns just before the target cpu calls @func. 894 * 895 * You must not call this function with disabled interrupts or from a 896 * hardware interrupt handler or from a bottom half handler. 897 */ 898 void smp_call_function(smp_call_func_t func, void *info, int wait) 899 { 900 preempt_disable(); 901 smp_call_function_many(cpu_online_mask, func, info, wait); 902 preempt_enable(); 903 } 904 EXPORT_SYMBOL(smp_call_function); 905 906 /* Setup configured maximum number of CPUs to activate */ 907 unsigned int setup_max_cpus = NR_CPUS; 908 EXPORT_SYMBOL(setup_max_cpus); 909 910 911 /* 912 * Setup routine for controlling SMP activation 913 * 914 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP 915 * activation entirely (the MPS table probe still happens, though). 916 * 917 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer 918 * greater than 0, limits the maximum number of CPUs activated in 919 * SMP mode to <NUM>. 920 */ 921 922 void __weak __init arch_disable_smp_support(void) { } 923 924 static int __init nosmp(char *str) 925 { 926 setup_max_cpus = 0; 927 arch_disable_smp_support(); 928 929 return 0; 930 } 931 932 early_param("nosmp", nosmp); 933 934 /* this is hard limit */ 935 static int __init nrcpus(char *str) 936 { 937 int nr_cpus; 938 939 if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids) 940 set_nr_cpu_ids(nr_cpus); 941 942 return 0; 943 } 944 945 early_param("nr_cpus", nrcpus); 946 947 static int __init maxcpus(char *str) 948 { 949 get_option(&str, &setup_max_cpus); 950 if (setup_max_cpus == 0) 951 arch_disable_smp_support(); 952 953 return 0; 954 } 955 956 early_param("maxcpus", maxcpus); 957 958 #if (NR_CPUS > 1) && !defined(CONFIG_FORCE_NR_CPUS) 959 /* Setup number of possible processor ids */ 960 unsigned int nr_cpu_ids __read_mostly = NR_CPUS; 961 EXPORT_SYMBOL(nr_cpu_ids); 962 #endif 963 964 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */ 965 void __init setup_nr_cpu_ids(void) 966 { 967 set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1); 968 } 969 970 /* Called by boot processor to activate the rest. */ 971 void __init smp_init(void) 972 { 973 int num_nodes, num_cpus; 974 975 idle_threads_init(); 976 cpuhp_threads_init(); 977 978 pr_info("Bringing up secondary CPUs ...\n"); 979 980 bringup_nonboot_cpus(setup_max_cpus); 981 982 num_nodes = num_online_nodes(); 983 num_cpus = num_online_cpus(); 984 pr_info("Brought up %d node%s, %d CPU%s\n", 985 num_nodes, (num_nodes > 1 ? "s" : ""), 986 num_cpus, (num_cpus > 1 ? "s" : "")); 987 988 /* Any cleanup work */ 989 smp_cpus_done(setup_max_cpus); 990 } 991 992 /* 993 * on_each_cpu_cond(): Call a function on each processor for which 994 * the supplied function cond_func returns true, optionally waiting 995 * for all the required CPUs to finish. This may include the local 996 * processor. 997 * @cond_func: A callback function that is passed a cpu id and 998 * the info parameter. The function is called 999 * with preemption disabled. The function should 1000 * return a blooean value indicating whether to IPI 1001 * the specified CPU. 1002 * @func: The function to run on all applicable CPUs. 1003 * This must be fast and non-blocking. 1004 * @info: An arbitrary pointer to pass to both functions. 1005 * @wait: If true, wait (atomically) until function has 1006 * completed on other CPUs. 1007 * 1008 * Preemption is disabled to protect against CPUs going offline but not online. 1009 * CPUs going online during the call will not be seen or sent an IPI. 1010 * 1011 * You must not call this function with disabled interrupts or 1012 * from a hardware interrupt handler or from a bottom half handler. 1013 */ 1014 void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func, 1015 void *info, bool wait, const struct cpumask *mask) 1016 { 1017 unsigned int scf_flags = SCF_RUN_LOCAL; 1018 1019 if (wait) 1020 scf_flags |= SCF_WAIT; 1021 1022 preempt_disable(); 1023 smp_call_function_many_cond(mask, func, info, scf_flags, cond_func); 1024 preempt_enable(); 1025 } 1026 EXPORT_SYMBOL(on_each_cpu_cond_mask); 1027 1028 static void do_nothing(void *unused) 1029 { 1030 } 1031 1032 /** 1033 * kick_all_cpus_sync - Force all cpus out of idle 1034 * 1035 * Used to synchronize the update of pm_idle function pointer. It's 1036 * called after the pointer is updated and returns after the dummy 1037 * callback function has been executed on all cpus. The execution of 1038 * the function can only happen on the remote cpus after they have 1039 * left the idle function which had been called via pm_idle function 1040 * pointer. So it's guaranteed that nothing uses the previous pointer 1041 * anymore. 1042 */ 1043 void kick_all_cpus_sync(void) 1044 { 1045 /* Make sure the change is visible before we kick the cpus */ 1046 smp_mb(); 1047 smp_call_function(do_nothing, NULL, 1); 1048 } 1049 EXPORT_SYMBOL_GPL(kick_all_cpus_sync); 1050 1051 /** 1052 * wake_up_all_idle_cpus - break all cpus out of idle 1053 * wake_up_all_idle_cpus try to break all cpus which is in idle state even 1054 * including idle polling cpus, for non-idle cpus, we will do nothing 1055 * for them. 1056 */ 1057 void wake_up_all_idle_cpus(void) 1058 { 1059 int cpu; 1060 1061 for_each_possible_cpu(cpu) { 1062 preempt_disable(); 1063 if (cpu != smp_processor_id() && cpu_online(cpu)) 1064 wake_up_if_idle(cpu); 1065 preempt_enable(); 1066 } 1067 } 1068 EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus); 1069 1070 /** 1071 * struct smp_call_on_cpu_struct - Call a function on a specific CPU 1072 * @work: &work_struct 1073 * @done: &completion to signal 1074 * @func: function to call 1075 * @data: function's data argument 1076 * @ret: return value from @func 1077 * @cpu: target CPU (%-1 for any CPU) 1078 * 1079 * Used to call a function on a specific cpu and wait for it to return. 1080 * Optionally make sure the call is done on a specified physical cpu via vcpu 1081 * pinning in order to support virtualized environments. 1082 */ 1083 struct smp_call_on_cpu_struct { 1084 struct work_struct work; 1085 struct completion done; 1086 int (*func)(void *); 1087 void *data; 1088 int ret; 1089 int cpu; 1090 }; 1091 1092 static void smp_call_on_cpu_callback(struct work_struct *work) 1093 { 1094 struct smp_call_on_cpu_struct *sscs; 1095 1096 sscs = container_of(work, struct smp_call_on_cpu_struct, work); 1097 if (sscs->cpu >= 0) 1098 hypervisor_pin_vcpu(sscs->cpu); 1099 sscs->ret = sscs->func(sscs->data); 1100 if (sscs->cpu >= 0) 1101 hypervisor_pin_vcpu(-1); 1102 1103 complete(&sscs->done); 1104 } 1105 1106 int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys) 1107 { 1108 struct smp_call_on_cpu_struct sscs = { 1109 .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done), 1110 .func = func, 1111 .data = par, 1112 .cpu = phys ? cpu : -1, 1113 }; 1114 1115 INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback); 1116 1117 if (cpu >= nr_cpu_ids || !cpu_online(cpu)) 1118 return -ENXIO; 1119 1120 queue_work_on(cpu, system_wq, &sscs.work); 1121 wait_for_completion(&sscs.done); 1122 1123 return sscs.ret; 1124 } 1125 EXPORT_SYMBOL_GPL(smp_call_on_cpu); 1126