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 #include <linux/string_choices.h> 29 30 #include <trace/events/ipi.h> 31 #define CREATE_TRACE_POINTS 32 #include <trace/events/csd.h> 33 #undef CREATE_TRACE_POINTS 34 35 #include "smpboot.h" 36 #include "sched/smp.h" 37 38 #define CSD_TYPE(_csd) ((_csd)->node.u_flags & CSD_FLAG_TYPE_MASK) 39 40 struct call_function_data { 41 call_single_data_t __percpu *csd; 42 cpumask_var_t cpumask; 43 cpumask_var_t cpumask_ipi; 44 }; 45 46 static DEFINE_PER_CPU_ALIGNED(struct call_function_data, cfd_data); 47 48 static DEFINE_PER_CPU_SHARED_ALIGNED(struct llist_head, call_single_queue); 49 50 static DEFINE_PER_CPU(atomic_t, trigger_backtrace) = ATOMIC_INIT(1); 51 52 static void __flush_smp_call_function_queue(bool warn_cpu_offline); 53 54 int smpcfd_prepare_cpu(unsigned int cpu) 55 { 56 struct call_function_data *cfd = &per_cpu(cfd_data, cpu); 57 58 if (!zalloc_cpumask_var_node(&cfd->cpumask, GFP_KERNEL, 59 cpu_to_node(cpu))) 60 return -ENOMEM; 61 if (!zalloc_cpumask_var_node(&cfd->cpumask_ipi, GFP_KERNEL, 62 cpu_to_node(cpu))) { 63 free_cpumask_var(cfd->cpumask); 64 return -ENOMEM; 65 } 66 cfd->csd = alloc_percpu(call_single_data_t); 67 if (!cfd->csd) { 68 free_cpumask_var(cfd->cpumask); 69 free_cpumask_var(cfd->cpumask_ipi); 70 return -ENOMEM; 71 } 72 73 return 0; 74 } 75 76 int smpcfd_dead_cpu(unsigned int cpu) 77 { 78 struct call_function_data *cfd = &per_cpu(cfd_data, cpu); 79 80 free_cpumask_var(cfd->cpumask); 81 free_cpumask_var(cfd->cpumask_ipi); 82 free_percpu(cfd->csd); 83 return 0; 84 } 85 86 int smpcfd_dying_cpu(unsigned int cpu) 87 { 88 /* 89 * The IPIs for the smp-call-function callbacks queued by other 90 * CPUs might arrive late, either due to hardware latencies or 91 * because this CPU disabled interrupts (inside stop-machine) 92 * before the IPIs were sent. So flush out any pending callbacks 93 * explicitly (without waiting for the IPIs to arrive), to 94 * ensure that the outgoing CPU doesn't go offline with work 95 * still pending. 96 */ 97 __flush_smp_call_function_queue(false); 98 irq_work_run(); 99 return 0; 100 } 101 102 void __init call_function_init(void) 103 { 104 int i; 105 106 for_each_possible_cpu(i) 107 init_llist_head(&per_cpu(call_single_queue, i)); 108 109 smpcfd_prepare_cpu(smp_processor_id()); 110 } 111 112 static __always_inline void 113 send_call_function_single_ipi(int cpu) 114 { 115 if (call_function_single_prep_ipi(cpu)) { 116 trace_ipi_send_cpu(cpu, _RET_IP_, 117 generic_smp_call_function_single_interrupt); 118 arch_send_call_function_single_ipi(cpu); 119 } 120 } 121 122 static __always_inline void 123 send_call_function_ipi_mask(struct cpumask *mask) 124 { 125 trace_ipi_send_cpumask(mask, _RET_IP_, 126 generic_smp_call_function_single_interrupt); 127 arch_send_call_function_ipi_mask(mask); 128 } 129 130 static __always_inline void 131 csd_do_func(smp_call_func_t func, void *info, call_single_data_t *csd) 132 { 133 trace_csd_function_entry(func, csd); 134 func(info); 135 trace_csd_function_exit(func, csd); 136 } 137 138 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 139 140 static DEFINE_STATIC_KEY_MAYBE(CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT, csdlock_debug_enabled); 141 142 /* 143 * Parse the csdlock_debug= kernel boot parameter. 144 * 145 * If you need to restore the old "ext" value that once provided 146 * additional debugging information, reapply the following commits: 147 * 148 * de7b09ef658d ("locking/csd_lock: Prepare more CSD lock debugging") 149 * a5aabace5fb8 ("locking/csd_lock: Add more data to CSD lock debugging") 150 */ 151 static int __init csdlock_debug(char *str) 152 { 153 int ret; 154 unsigned int val = 0; 155 156 ret = get_option(&str, &val); 157 if (ret) { 158 if (val) 159 static_branch_enable(&csdlock_debug_enabled); 160 else 161 static_branch_disable(&csdlock_debug_enabled); 162 } 163 164 return 1; 165 } 166 __setup("csdlock_debug=", csdlock_debug); 167 168 static DEFINE_PER_CPU(call_single_data_t *, cur_csd); 169 static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func); 170 static DEFINE_PER_CPU(void *, cur_csd_info); 171 172 static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */ 173 module_param(csd_lock_timeout, ulong, 0444); 174 static int panic_on_ipistall; /* CSD panic timeout in milliseconds, 300000 for five minutes. */ 175 module_param(panic_on_ipistall, int, 0444); 176 177 static atomic_t csd_bug_count = ATOMIC_INIT(0); 178 179 /* Record current CSD work for current CPU, NULL to erase. */ 180 static void __csd_lock_record(call_single_data_t *csd) 181 { 182 if (!csd) { 183 smp_mb(); /* NULL cur_csd after unlock. */ 184 __this_cpu_write(cur_csd, NULL); 185 return; 186 } 187 __this_cpu_write(cur_csd_func, csd->func); 188 __this_cpu_write(cur_csd_info, csd->info); 189 smp_wmb(); /* func and info before csd. */ 190 __this_cpu_write(cur_csd, csd); 191 smp_mb(); /* Update cur_csd before function call. */ 192 /* Or before unlock, as the case may be. */ 193 } 194 195 static __always_inline void csd_lock_record(call_single_data_t *csd) 196 { 197 if (static_branch_unlikely(&csdlock_debug_enabled)) 198 __csd_lock_record(csd); 199 } 200 201 static int csd_lock_wait_getcpu(call_single_data_t *csd) 202 { 203 unsigned int csd_type; 204 205 csd_type = CSD_TYPE(csd); 206 if (csd_type == CSD_TYPE_ASYNC || csd_type == CSD_TYPE_SYNC) 207 return csd->node.dst; /* Other CSD_TYPE_ values might not have ->dst. */ 208 return -1; 209 } 210 211 static atomic_t n_csd_lock_stuck; 212 213 /** 214 * csd_lock_is_stuck - Has a CSD-lock acquisition been stuck too long? 215 * 216 * Returns @true if a CSD-lock acquisition is stuck and has been stuck 217 * long enough for a "non-responsive CSD lock" message to be printed. 218 */ 219 bool csd_lock_is_stuck(void) 220 { 221 return !!atomic_read(&n_csd_lock_stuck); 222 } 223 224 /* 225 * Complain if too much time spent waiting. Note that only 226 * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU, 227 * so waiting on other types gets much less information. 228 */ 229 static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, int *bug_id, unsigned long *nmessages) 230 { 231 int cpu = -1; 232 int cpux; 233 bool firsttime; 234 u64 ts2, ts_delta; 235 call_single_data_t *cpu_cur_csd; 236 unsigned int flags = READ_ONCE(csd->node.u_flags); 237 unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC; 238 239 if (!(flags & CSD_FLAG_LOCK)) { 240 if (!unlikely(*bug_id)) 241 return true; 242 cpu = csd_lock_wait_getcpu(csd); 243 pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n", 244 *bug_id, raw_smp_processor_id(), cpu); 245 atomic_dec(&n_csd_lock_stuck); 246 return true; 247 } 248 249 ts2 = ktime_get_mono_fast_ns(); 250 /* How long since we last checked for a stuck CSD lock.*/ 251 ts_delta = ts2 - *ts1; 252 if (likely(ts_delta <= csd_lock_timeout_ns * (*nmessages + 1) * 253 (!*nmessages ? 1 : (ilog2(num_online_cpus()) / 2 + 1)) || 254 csd_lock_timeout_ns == 0)) 255 return false; 256 257 if (ts0 > ts2) { 258 /* Our own sched_clock went backward; don't blame another CPU. */ 259 ts_delta = ts0 - ts2; 260 pr_alert("sched_clock on CPU %d went backward by %llu ns\n", raw_smp_processor_id(), ts_delta); 261 *ts1 = ts2; 262 return false; 263 } 264 265 firsttime = !*bug_id; 266 if (firsttime) 267 *bug_id = atomic_inc_return(&csd_bug_count); 268 cpu = csd_lock_wait_getcpu(csd); 269 if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu)) 270 cpux = 0; 271 else 272 cpux = cpu; 273 cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */ 274 /* How long since this CSD lock was stuck. */ 275 ts_delta = ts2 - ts0; 276 pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %lld ns for CPU#%02d %pS(%ps).\n", 277 firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), (s64)ts_delta, 278 cpu, csd->func, csd->info); 279 (*nmessages)++; 280 if (firsttime) 281 atomic_inc(&n_csd_lock_stuck); 282 /* 283 * If the CSD lock is still stuck after 5 minutes, it is unlikely 284 * to become unstuck. Use a signed comparison to avoid triggering 285 * on underflows when the TSC is out of sync between sockets. 286 */ 287 BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC)); 288 if (cpu_cur_csd && csd != cpu_cur_csd) { 289 pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n", 290 *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)), 291 READ_ONCE(per_cpu(cur_csd_info, cpux))); 292 } else { 293 pr_alert("\tcsd: CSD lock (#%d) %s.\n", 294 *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request"); 295 } 296 if (cpu >= 0) { 297 if (atomic_cmpxchg_acquire(&per_cpu(trigger_backtrace, cpu), 1, 0)) 298 dump_cpu_task(cpu); 299 if (!cpu_cur_csd) { 300 pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu); 301 arch_send_call_function_single_ipi(cpu); 302 } 303 } 304 if (firsttime) 305 dump_stack(); 306 *ts1 = ts2; 307 308 return false; 309 } 310 311 /* 312 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources 313 * 314 * For non-synchronous ipi calls the csd can still be in use by the 315 * previous function call. For multi-cpu calls its even more interesting 316 * as we'll have to ensure no other cpu is observing our csd. 317 */ 318 static void __csd_lock_wait(call_single_data_t *csd) 319 { 320 unsigned long nmessages = 0; 321 int bug_id = 0; 322 u64 ts0, ts1; 323 324 ts1 = ts0 = ktime_get_mono_fast_ns(); 325 for (;;) { 326 if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id, &nmessages)) 327 break; 328 cpu_relax(); 329 } 330 smp_acquire__after_ctrl_dep(); 331 } 332 333 static __always_inline void csd_lock_wait(call_single_data_t *csd) 334 { 335 if (static_branch_unlikely(&csdlock_debug_enabled)) { 336 __csd_lock_wait(csd); 337 return; 338 } 339 340 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); 341 } 342 #else 343 static void csd_lock_record(call_single_data_t *csd) 344 { 345 } 346 347 static __always_inline void csd_lock_wait(call_single_data_t *csd) 348 { 349 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); 350 } 351 #endif 352 353 static __always_inline void csd_lock(call_single_data_t *csd) 354 { 355 csd_lock_wait(csd); 356 csd->node.u_flags |= CSD_FLAG_LOCK; 357 358 /* 359 * prevent CPU from reordering the above assignment 360 * to ->flags with any subsequent assignments to other 361 * fields of the specified call_single_data_t structure: 362 */ 363 smp_wmb(); 364 } 365 366 static __always_inline void csd_unlock(call_single_data_t *csd) 367 { 368 WARN_ON(!(csd->node.u_flags & CSD_FLAG_LOCK)); 369 370 /* 371 * ensure we're all done before releasing data: 372 */ 373 smp_store_release(&csd->node.u_flags, 0); 374 } 375 376 static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data); 377 378 void __smp_call_single_queue(int cpu, struct llist_node *node) 379 { 380 /* 381 * We have to check the type of the CSD before queueing it, because 382 * once queued it can have its flags cleared by 383 * flush_smp_call_function_queue() 384 * even if we haven't sent the smp_call IPI yet (e.g. the stopper 385 * executes migration_cpu_stop() on the remote CPU). 386 */ 387 if (trace_csd_queue_cpu_enabled()) { 388 call_single_data_t *csd; 389 smp_call_func_t func; 390 391 csd = container_of(node, call_single_data_t, node.llist); 392 func = CSD_TYPE(csd) == CSD_TYPE_TTWU ? 393 sched_ttwu_pending : csd->func; 394 395 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); 396 } 397 398 /* 399 * The list addition should be visible to the target CPU when it pops 400 * the head of the list to pull the entry off it in the IPI handler 401 * because of normal cache coherency rules implied by the underlying 402 * llist ops. 403 * 404 * If IPIs can go out of order to the cache coherency protocol 405 * in an architecture, sufficient synchronisation should be added 406 * to arch code to make it appear to obey cache coherency WRT 407 * locking and barrier primitives. Generic code isn't really 408 * equipped to do the right thing... 409 */ 410 if (llist_add(node, &per_cpu(call_single_queue, cpu))) 411 send_call_function_single_ipi(cpu); 412 } 413 414 /* 415 * Insert a previously allocated call_single_data_t element 416 * for execution on the given CPU. data must already have 417 * ->func, ->info, and ->flags set. 418 */ 419 static int generic_exec_single(int cpu, call_single_data_t *csd) 420 { 421 if (cpu == smp_processor_id()) { 422 smp_call_func_t func = csd->func; 423 void *info = csd->info; 424 unsigned long flags; 425 426 /* 427 * We can unlock early even for the synchronous on-stack case, 428 * since we're doing this from the same CPU.. 429 */ 430 csd_lock_record(csd); 431 csd_unlock(csd); 432 local_irq_save(flags); 433 csd_do_func(func, info, NULL); 434 csd_lock_record(NULL); 435 local_irq_restore(flags); 436 return 0; 437 } 438 439 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) { 440 csd_unlock(csd); 441 return -ENXIO; 442 } 443 444 __smp_call_single_queue(cpu, &csd->node.llist); 445 446 return 0; 447 } 448 449 /** 450 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks 451 * 452 * Invoked by arch to handle an IPI for call function single. 453 * Must be called with interrupts disabled. 454 */ 455 void generic_smp_call_function_single_interrupt(void) 456 { 457 __flush_smp_call_function_queue(true); 458 } 459 460 /** 461 * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks 462 * 463 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an 464 * offline CPU. Skip this check if set to 'false'. 465 * 466 * Flush any pending smp-call-function callbacks queued on this CPU. This is 467 * invoked by the generic IPI handler, as well as by a CPU about to go offline, 468 * to ensure that all pending IPI callbacks are run before it goes completely 469 * offline. 470 * 471 * Loop through the call_single_queue and run all the queued callbacks. 472 * Must be called with interrupts disabled. 473 */ 474 static void __flush_smp_call_function_queue(bool warn_cpu_offline) 475 { 476 call_single_data_t *csd, *csd_next; 477 struct llist_node *entry, *prev; 478 struct llist_head *head; 479 static bool warned; 480 atomic_t *tbt; 481 482 lockdep_assert_irqs_disabled(); 483 484 /* Allow waiters to send backtrace NMI from here onwards */ 485 tbt = this_cpu_ptr(&trigger_backtrace); 486 atomic_set_release(tbt, 1); 487 488 head = this_cpu_ptr(&call_single_queue); 489 entry = llist_del_all(head); 490 entry = llist_reverse_order(entry); 491 492 /* There shouldn't be any pending callbacks on an offline CPU. */ 493 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) && 494 !warned && entry != NULL)) { 495 warned = true; 496 WARN(1, "IPI on offline CPU %d\n", smp_processor_id()); 497 498 /* 499 * We don't have to use the _safe() variant here 500 * because we are not invoking the IPI handlers yet. 501 */ 502 llist_for_each_entry(csd, entry, node.llist) { 503 switch (CSD_TYPE(csd)) { 504 case CSD_TYPE_ASYNC: 505 case CSD_TYPE_SYNC: 506 case CSD_TYPE_IRQ_WORK: 507 pr_warn("IPI callback %pS sent to offline CPU\n", 508 csd->func); 509 break; 510 511 case CSD_TYPE_TTWU: 512 pr_warn("IPI task-wakeup sent to offline CPU\n"); 513 break; 514 515 default: 516 pr_warn("IPI callback, unknown type %d, sent to offline CPU\n", 517 CSD_TYPE(csd)); 518 break; 519 } 520 } 521 } 522 523 /* 524 * First; run all SYNC callbacks, people are waiting for us. 525 */ 526 prev = NULL; 527 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { 528 /* Do we wait until *after* callback? */ 529 if (CSD_TYPE(csd) == CSD_TYPE_SYNC) { 530 smp_call_func_t func = csd->func; 531 void *info = csd->info; 532 533 if (prev) { 534 prev->next = &csd_next->node.llist; 535 } else { 536 entry = &csd_next->node.llist; 537 } 538 539 csd_lock_record(csd); 540 csd_do_func(func, info, csd); 541 csd_unlock(csd); 542 csd_lock_record(NULL); 543 } else { 544 prev = &csd->node.llist; 545 } 546 } 547 548 if (!entry) 549 return; 550 551 /* 552 * Second; run all !SYNC callbacks. 553 */ 554 prev = NULL; 555 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { 556 int type = CSD_TYPE(csd); 557 558 if (type != CSD_TYPE_TTWU) { 559 if (prev) { 560 prev->next = &csd_next->node.llist; 561 } else { 562 entry = &csd_next->node.llist; 563 } 564 565 if (type == CSD_TYPE_ASYNC) { 566 smp_call_func_t func = csd->func; 567 void *info = csd->info; 568 569 csd_lock_record(csd); 570 csd_unlock(csd); 571 csd_do_func(func, info, csd); 572 csd_lock_record(NULL); 573 } else if (type == CSD_TYPE_IRQ_WORK) { 574 irq_work_single(csd); 575 } 576 577 } else { 578 prev = &csd->node.llist; 579 } 580 } 581 582 /* 583 * Third; only CSD_TYPE_TTWU is left, issue those. 584 */ 585 if (entry) { 586 csd = llist_entry(entry, typeof(*csd), node.llist); 587 csd_do_func(sched_ttwu_pending, entry, csd); 588 } 589 } 590 591 592 /** 593 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks 594 * from task context (idle, migration thread) 595 * 596 * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it 597 * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by 598 * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to 599 * handle queued SMP function calls before scheduling. 600 * 601 * The migration thread has to ensure that an eventually pending wakeup has 602 * been handled before it migrates a task. 603 */ 604 void flush_smp_call_function_queue(void) 605 { 606 unsigned int was_pending; 607 unsigned long flags; 608 609 if (llist_empty(this_cpu_ptr(&call_single_queue))) 610 return; 611 612 local_irq_save(flags); 613 /* Get the already pending soft interrupts for RT enabled kernels */ 614 was_pending = local_softirq_pending(); 615 __flush_smp_call_function_queue(true); 616 if (local_softirq_pending()) 617 do_softirq_post_smp_call_flush(was_pending); 618 619 local_irq_restore(flags); 620 } 621 622 /* 623 * smp_call_function_single - Run a function on a specific CPU 624 * @func: The function to run. This must be fast and non-blocking. 625 * @info: An arbitrary pointer to pass to the function. 626 * @wait: If true, wait until function has completed on other CPUs. 627 * 628 * Returns 0 on success, else a negative status code. 629 */ 630 int smp_call_function_single(int cpu, smp_call_func_t func, void *info, 631 int wait) 632 { 633 call_single_data_t *csd; 634 call_single_data_t csd_stack = { 635 .node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, }, 636 }; 637 int this_cpu; 638 int err; 639 640 /* 641 * prevent preemption and reschedule on another processor, 642 * as well as CPU removal 643 */ 644 this_cpu = get_cpu(); 645 646 /* 647 * Can deadlock when called with interrupts disabled. 648 * We allow cpu's that are not yet online though, as no one else can 649 * send smp call function interrupt to this cpu and as such deadlocks 650 * can't happen. 651 */ 652 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() 653 && !oops_in_progress); 654 655 /* 656 * When @wait we can deadlock when we interrupt between llist_add() and 657 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to 658 * csd_lock() on because the interrupt context uses the same csd 659 * storage. 660 */ 661 WARN_ON_ONCE(!in_task()); 662 663 csd = &csd_stack; 664 if (!wait) { 665 csd = this_cpu_ptr(&csd_data); 666 csd_lock(csd); 667 } 668 669 csd->func = func; 670 csd->info = info; 671 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 672 csd->node.src = smp_processor_id(); 673 csd->node.dst = cpu; 674 #endif 675 676 err = generic_exec_single(cpu, csd); 677 678 if (wait) 679 csd_lock_wait(csd); 680 681 put_cpu(); 682 683 return err; 684 } 685 EXPORT_SYMBOL(smp_call_function_single); 686 687 /** 688 * smp_call_function_single_async() - Run an asynchronous function on a 689 * specific CPU. 690 * @cpu: The CPU to run on. 691 * @csd: Pre-allocated and setup data structure 692 * 693 * Like smp_call_function_single(), but the call is asynchonous and 694 * can thus be done from contexts with disabled interrupts. 695 * 696 * The caller passes his own pre-allocated data structure 697 * (ie: embedded in an object) and is responsible for synchronizing it 698 * such that the IPIs performed on the @csd are strictly serialized. 699 * 700 * If the function is called with one csd which has not yet been 701 * processed by previous call to smp_call_function_single_async(), the 702 * function will return immediately with -EBUSY showing that the csd 703 * object is still in progress. 704 * 705 * NOTE: Be careful, there is unfortunately no current debugging facility to 706 * validate the correctness of this serialization. 707 * 708 * Return: %0 on success or negative errno value on error 709 */ 710 int smp_call_function_single_async(int cpu, call_single_data_t *csd) 711 { 712 int err = 0; 713 714 preempt_disable(); 715 716 if (csd->node.u_flags & CSD_FLAG_LOCK) { 717 err = -EBUSY; 718 goto out; 719 } 720 721 csd->node.u_flags = CSD_FLAG_LOCK; 722 smp_wmb(); 723 724 err = generic_exec_single(cpu, csd); 725 726 out: 727 preempt_enable(); 728 729 return err; 730 } 731 EXPORT_SYMBOL_GPL(smp_call_function_single_async); 732 733 /* 734 * smp_call_function_any - Run a function on any of the given cpus 735 * @mask: The mask of cpus it can run on. 736 * @func: The function to run. This must be fast and non-blocking. 737 * @info: An arbitrary pointer to pass to the function. 738 * @wait: If true, wait until function has completed. 739 * 740 * Returns 0 on success, else a negative status code (if no cpus were online). 741 * 742 * Selection preference: 743 * 1) current cpu if in @mask 744 * 2) any cpu of current node if in @mask 745 * 3) any other online cpu in @mask 746 */ 747 int smp_call_function_any(const struct cpumask *mask, 748 smp_call_func_t func, void *info, int wait) 749 { 750 unsigned int cpu; 751 const struct cpumask *nodemask; 752 int ret; 753 754 /* Try for same CPU (cheapest) */ 755 cpu = get_cpu(); 756 if (cpumask_test_cpu(cpu, mask)) 757 goto call; 758 759 /* Try for same node. */ 760 nodemask = cpumask_of_node(cpu_to_node(cpu)); 761 for (cpu = cpumask_first_and(nodemask, mask); cpu < nr_cpu_ids; 762 cpu = cpumask_next_and(cpu, nodemask, mask)) { 763 if (cpu_online(cpu)) 764 goto call; 765 } 766 767 /* Any online will do: smp_call_function_single handles nr_cpu_ids. */ 768 cpu = cpumask_any_and(mask, cpu_online_mask); 769 call: 770 ret = smp_call_function_single(cpu, func, info, wait); 771 put_cpu(); 772 return ret; 773 } 774 EXPORT_SYMBOL_GPL(smp_call_function_any); 775 776 /* 777 * Flags to be used as scf_flags argument of smp_call_function_many_cond(). 778 * 779 * %SCF_WAIT: Wait until function execution is completed 780 * %SCF_RUN_LOCAL: Run also locally if local cpu is set in cpumask 781 */ 782 #define SCF_WAIT (1U << 0) 783 #define SCF_RUN_LOCAL (1U << 1) 784 785 static void smp_call_function_many_cond(const struct cpumask *mask, 786 smp_call_func_t func, void *info, 787 unsigned int scf_flags, 788 smp_cond_func_t cond_func) 789 { 790 int cpu, last_cpu, this_cpu = smp_processor_id(); 791 struct call_function_data *cfd; 792 bool wait = scf_flags & SCF_WAIT; 793 int nr_cpus = 0; 794 bool run_remote = false; 795 bool run_local = false; 796 797 lockdep_assert_preemption_disabled(); 798 799 /* 800 * Can deadlock when called with interrupts disabled. 801 * We allow cpu's that are not yet online though, as no one else can 802 * send smp call function interrupt to this cpu and as such deadlocks 803 * can't happen. 804 */ 805 if (cpu_online(this_cpu) && !oops_in_progress && 806 !early_boot_irqs_disabled) 807 lockdep_assert_irqs_enabled(); 808 809 /* 810 * When @wait we can deadlock when we interrupt between llist_add() and 811 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to 812 * csd_lock() on because the interrupt context uses the same csd 813 * storage. 814 */ 815 WARN_ON_ONCE(!in_task()); 816 817 /* Check if we need local execution. */ 818 if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask)) 819 run_local = true; 820 821 /* Check if we need remote execution, i.e., any CPU excluding this one. */ 822 cpu = cpumask_first_and(mask, cpu_online_mask); 823 if (cpu == this_cpu) 824 cpu = cpumask_next_and(cpu, mask, cpu_online_mask); 825 if (cpu < nr_cpu_ids) 826 run_remote = true; 827 828 if (run_remote) { 829 cfd = this_cpu_ptr(&cfd_data); 830 cpumask_and(cfd->cpumask, mask, cpu_online_mask); 831 __cpumask_clear_cpu(this_cpu, cfd->cpumask); 832 833 cpumask_clear(cfd->cpumask_ipi); 834 for_each_cpu(cpu, cfd->cpumask) { 835 call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu); 836 837 if (cond_func && !cond_func(cpu, info)) { 838 __cpumask_clear_cpu(cpu, cfd->cpumask); 839 continue; 840 } 841 842 csd_lock(csd); 843 if (wait) 844 csd->node.u_flags |= CSD_TYPE_SYNC; 845 csd->func = func; 846 csd->info = info; 847 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 848 csd->node.src = smp_processor_id(); 849 csd->node.dst = cpu; 850 #endif 851 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); 852 853 if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) { 854 __cpumask_set_cpu(cpu, cfd->cpumask_ipi); 855 nr_cpus++; 856 last_cpu = cpu; 857 } 858 } 859 860 /* 861 * Choose the most efficient way to send an IPI. Note that the 862 * number of CPUs might be zero due to concurrent changes to the 863 * provided mask. 864 */ 865 if (nr_cpus == 1) 866 send_call_function_single_ipi(last_cpu); 867 else if (likely(nr_cpus > 1)) 868 send_call_function_ipi_mask(cfd->cpumask_ipi); 869 } 870 871 if (run_local && (!cond_func || cond_func(this_cpu, info))) { 872 unsigned long flags; 873 874 local_irq_save(flags); 875 csd_do_func(func, info, NULL); 876 local_irq_restore(flags); 877 } 878 879 if (run_remote && wait) { 880 for_each_cpu(cpu, cfd->cpumask) { 881 call_single_data_t *csd; 882 883 csd = per_cpu_ptr(cfd->csd, cpu); 884 csd_lock_wait(csd); 885 } 886 } 887 } 888 889 /** 890 * smp_call_function_many(): Run a function on a set of CPUs. 891 * @mask: The set of cpus to run on (only runs on online subset). 892 * @func: The function to run. This must be fast and non-blocking. 893 * @info: An arbitrary pointer to pass to the function. 894 * @wait: Bitmask that controls the operation. If %SCF_WAIT is set, wait 895 * (atomically) until function has completed on other CPUs. If 896 * %SCF_RUN_LOCAL is set, the function will also be run locally 897 * if the local CPU is set in the @cpumask. 898 * 899 * If @wait is true, then returns once @func has returned. 900 * 901 * You must not call this function with disabled interrupts or from a 902 * hardware interrupt handler or from a bottom half handler. Preemption 903 * must be disabled when calling this function. 904 */ 905 void smp_call_function_many(const struct cpumask *mask, 906 smp_call_func_t func, void *info, bool wait) 907 { 908 smp_call_function_many_cond(mask, func, info, wait * SCF_WAIT, NULL); 909 } 910 EXPORT_SYMBOL(smp_call_function_many); 911 912 /** 913 * smp_call_function(): Run a function on all other CPUs. 914 * @func: The function to run. This must be fast and non-blocking. 915 * @info: An arbitrary pointer to pass to the function. 916 * @wait: If true, wait (atomically) until function has completed 917 * on other CPUs. 918 * 919 * Returns 0. 920 * 921 * If @wait is true, then returns once @func has returned; otherwise 922 * it returns just before the target cpu calls @func. 923 * 924 * You must not call this function with disabled interrupts or from a 925 * hardware interrupt handler or from a bottom half handler. 926 */ 927 void smp_call_function(smp_call_func_t func, void *info, int wait) 928 { 929 preempt_disable(); 930 smp_call_function_many(cpu_online_mask, func, info, wait); 931 preempt_enable(); 932 } 933 EXPORT_SYMBOL(smp_call_function); 934 935 /* Setup configured maximum number of CPUs to activate */ 936 unsigned int setup_max_cpus = NR_CPUS; 937 EXPORT_SYMBOL(setup_max_cpus); 938 939 940 /* 941 * Setup routine for controlling SMP activation 942 * 943 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP 944 * activation entirely (the MPS table probe still happens, though). 945 * 946 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer 947 * greater than 0, limits the maximum number of CPUs activated in 948 * SMP mode to <NUM>. 949 */ 950 951 void __weak __init arch_disable_smp_support(void) { } 952 953 static int __init nosmp(char *str) 954 { 955 setup_max_cpus = 0; 956 arch_disable_smp_support(); 957 958 return 0; 959 } 960 961 early_param("nosmp", nosmp); 962 963 /* this is hard limit */ 964 static int __init nrcpus(char *str) 965 { 966 int nr_cpus; 967 968 if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids) 969 set_nr_cpu_ids(nr_cpus); 970 971 return 0; 972 } 973 974 early_param("nr_cpus", nrcpus); 975 976 static int __init maxcpus(char *str) 977 { 978 get_option(&str, &setup_max_cpus); 979 if (setup_max_cpus == 0) 980 arch_disable_smp_support(); 981 982 return 0; 983 } 984 985 early_param("maxcpus", maxcpus); 986 987 #if (NR_CPUS > 1) && !defined(CONFIG_FORCE_NR_CPUS) 988 /* Setup number of possible processor ids */ 989 unsigned int nr_cpu_ids __read_mostly = NR_CPUS; 990 EXPORT_SYMBOL(nr_cpu_ids); 991 #endif 992 993 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */ 994 void __init setup_nr_cpu_ids(void) 995 { 996 set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1); 997 } 998 999 /* Called by boot processor to activate the rest. */ 1000 void __init smp_init(void) 1001 { 1002 int num_nodes, num_cpus; 1003 1004 idle_threads_init(); 1005 cpuhp_threads_init(); 1006 1007 pr_info("Bringing up secondary CPUs ...\n"); 1008 1009 bringup_nonboot_cpus(setup_max_cpus); 1010 1011 num_nodes = num_online_nodes(); 1012 num_cpus = num_online_cpus(); 1013 pr_info("Brought up %d node%s, %d CPU%s\n", 1014 num_nodes, str_plural(num_nodes), num_cpus, str_plural(num_cpus)); 1015 1016 /* Any cleanup work */ 1017 smp_cpus_done(setup_max_cpus); 1018 } 1019 1020 /* 1021 * on_each_cpu_cond(): Call a function on each processor for which 1022 * the supplied function cond_func returns true, optionally waiting 1023 * for all the required CPUs to finish. This may include the local 1024 * processor. 1025 * @cond_func: A callback function that is passed a cpu id and 1026 * the info parameter. The function is called 1027 * with preemption disabled. The function should 1028 * return a blooean value indicating whether to IPI 1029 * the specified CPU. 1030 * @func: The function to run on all applicable CPUs. 1031 * This must be fast and non-blocking. 1032 * @info: An arbitrary pointer to pass to both functions. 1033 * @wait: If true, wait (atomically) until function has 1034 * completed on other CPUs. 1035 * 1036 * Preemption is disabled to protect against CPUs going offline but not online. 1037 * CPUs going online during the call will not be seen or sent an IPI. 1038 * 1039 * You must not call this function with disabled interrupts or 1040 * from a hardware interrupt handler or from a bottom half handler. 1041 */ 1042 void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func, 1043 void *info, bool wait, const struct cpumask *mask) 1044 { 1045 unsigned int scf_flags = SCF_RUN_LOCAL; 1046 1047 if (wait) 1048 scf_flags |= SCF_WAIT; 1049 1050 preempt_disable(); 1051 smp_call_function_many_cond(mask, func, info, scf_flags, cond_func); 1052 preempt_enable(); 1053 } 1054 EXPORT_SYMBOL(on_each_cpu_cond_mask); 1055 1056 static void do_nothing(void *unused) 1057 { 1058 } 1059 1060 /** 1061 * kick_all_cpus_sync - Force all cpus out of idle 1062 * 1063 * Used to synchronize the update of pm_idle function pointer. It's 1064 * called after the pointer is updated and returns after the dummy 1065 * callback function has been executed on all cpus. The execution of 1066 * the function can only happen on the remote cpus after they have 1067 * left the idle function which had been called via pm_idle function 1068 * pointer. So it's guaranteed that nothing uses the previous pointer 1069 * anymore. 1070 */ 1071 void kick_all_cpus_sync(void) 1072 { 1073 /* Make sure the change is visible before we kick the cpus */ 1074 smp_mb(); 1075 smp_call_function(do_nothing, NULL, 1); 1076 } 1077 EXPORT_SYMBOL_GPL(kick_all_cpus_sync); 1078 1079 /** 1080 * wake_up_all_idle_cpus - break all cpus out of idle 1081 * wake_up_all_idle_cpus try to break all cpus which is in idle state even 1082 * including idle polling cpus, for non-idle cpus, we will do nothing 1083 * for them. 1084 */ 1085 void wake_up_all_idle_cpus(void) 1086 { 1087 int cpu; 1088 1089 for_each_possible_cpu(cpu) { 1090 preempt_disable(); 1091 if (cpu != smp_processor_id() && cpu_online(cpu)) 1092 wake_up_if_idle(cpu); 1093 preempt_enable(); 1094 } 1095 } 1096 EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus); 1097 1098 /** 1099 * struct smp_call_on_cpu_struct - Call a function on a specific CPU 1100 * @work: &work_struct 1101 * @done: &completion to signal 1102 * @func: function to call 1103 * @data: function's data argument 1104 * @ret: return value from @func 1105 * @cpu: target CPU (%-1 for any CPU) 1106 * 1107 * Used to call a function on a specific cpu and wait for it to return. 1108 * Optionally make sure the call is done on a specified physical cpu via vcpu 1109 * pinning in order to support virtualized environments. 1110 */ 1111 struct smp_call_on_cpu_struct { 1112 struct work_struct work; 1113 struct completion done; 1114 int (*func)(void *); 1115 void *data; 1116 int ret; 1117 int cpu; 1118 }; 1119 1120 static void smp_call_on_cpu_callback(struct work_struct *work) 1121 { 1122 struct smp_call_on_cpu_struct *sscs; 1123 1124 sscs = container_of(work, struct smp_call_on_cpu_struct, work); 1125 if (sscs->cpu >= 0) 1126 hypervisor_pin_vcpu(sscs->cpu); 1127 sscs->ret = sscs->func(sscs->data); 1128 if (sscs->cpu >= 0) 1129 hypervisor_pin_vcpu(-1); 1130 1131 complete(&sscs->done); 1132 } 1133 1134 int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys) 1135 { 1136 struct smp_call_on_cpu_struct sscs = { 1137 .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done), 1138 .func = func, 1139 .data = par, 1140 .cpu = phys ? cpu : -1, 1141 }; 1142 1143 INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback); 1144 1145 if (cpu >= nr_cpu_ids || !cpu_online(cpu)) 1146 return -ENXIO; 1147 1148 queue_work_on(cpu, system_wq, &sscs.work); 1149 wait_for_completion(&sscs.done); 1150 destroy_work_on_stack(&sscs.work); 1151 1152 return sscs.ret; 1153 } 1154 EXPORT_SYMBOL_GPL(smp_call_on_cpu); 1155