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 CPUs 90 * might arrive late, either due to hardware latencies or because this 91 * CPU disabled interrupts (inside stop-machine) before the IPIs were 92 * sent. So flush out any pending callbacks explicitly (without waiting 93 * for the IPIs to arrive), to ensure that the outgoing CPU doesn't go 94 * offline with work still pending. 95 * 96 * This runs with interrupts disabled inside the stopper task invoked by 97 * stop_machine(), ensuring mutually exclusive CPU offlining and IPI flush. 98 */ 99 __flush_smp_call_function_queue(false); 100 irq_work_run(); 101 return 0; 102 } 103 104 void __init call_function_init(void) 105 { 106 int i; 107 108 for_each_possible_cpu(i) 109 init_llist_head(&per_cpu(call_single_queue, i)); 110 111 smpcfd_prepare_cpu(smp_processor_id()); 112 } 113 114 static __always_inline void 115 send_call_function_single_ipi(int cpu) 116 { 117 if (call_function_single_prep_ipi(cpu)) { 118 trace_ipi_send_cpu(cpu, _RET_IP_, 119 generic_smp_call_function_single_interrupt); 120 arch_send_call_function_single_ipi(cpu); 121 } 122 } 123 124 static __always_inline void 125 send_call_function_ipi_mask(struct cpumask *mask) 126 { 127 trace_ipi_send_cpumask(mask, _RET_IP_, 128 generic_smp_call_function_single_interrupt); 129 arch_send_call_function_ipi_mask(mask); 130 } 131 132 static __always_inline void 133 csd_do_func(smp_call_func_t func, void *info, call_single_data_t *csd) 134 { 135 trace_csd_function_entry(func, csd); 136 func(info); 137 trace_csd_function_exit(func, csd); 138 } 139 140 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 141 142 static DEFINE_STATIC_KEY_MAYBE(CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT, csdlock_debug_enabled); 143 144 /* 145 * Parse the csdlock_debug= kernel boot parameter. 146 * 147 * If you need to restore the old "ext" value that once provided 148 * additional debugging information, reapply the following commits: 149 * 150 * de7b09ef658d ("locking/csd_lock: Prepare more CSD lock debugging") 151 * a5aabace5fb8 ("locking/csd_lock: Add more data to CSD lock debugging") 152 */ 153 static int __init csdlock_debug(char *str) 154 { 155 int ret; 156 unsigned int val = 0; 157 158 ret = get_option(&str, &val); 159 if (ret) { 160 if (val) 161 static_branch_enable(&csdlock_debug_enabled); 162 else 163 static_branch_disable(&csdlock_debug_enabled); 164 } 165 166 return 1; 167 } 168 __setup("csdlock_debug=", csdlock_debug); 169 170 static DEFINE_PER_CPU(call_single_data_t *, cur_csd); 171 static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func); 172 static DEFINE_PER_CPU(void *, cur_csd_info); 173 174 static ulong csd_lock_timeout = 5000; /* CSD lock timeout in milliseconds. */ 175 module_param(csd_lock_timeout, ulong, 0644); 176 static int panic_on_ipistall; /* CSD panic timeout in milliseconds, 300000 for five minutes. */ 177 module_param(panic_on_ipistall, int, 0644); 178 179 static atomic_t csd_bug_count = ATOMIC_INIT(0); 180 181 /* Record current CSD work for current CPU, NULL to erase. */ 182 static void __csd_lock_record(call_single_data_t *csd) 183 { 184 if (!csd) { 185 smp_mb(); /* NULL cur_csd after unlock. */ 186 __this_cpu_write(cur_csd, NULL); 187 return; 188 } 189 __this_cpu_write(cur_csd_func, csd->func); 190 __this_cpu_write(cur_csd_info, csd->info); 191 smp_wmb(); /* func and info before csd. */ 192 __this_cpu_write(cur_csd, csd); 193 smp_mb(); /* Update cur_csd before function call. */ 194 /* Or before unlock, as the case may be. */ 195 } 196 197 static __always_inline void csd_lock_record(call_single_data_t *csd) 198 { 199 if (static_branch_unlikely(&csdlock_debug_enabled)) 200 __csd_lock_record(csd); 201 } 202 203 static int csd_lock_wait_getcpu(call_single_data_t *csd) 204 { 205 unsigned int csd_type; 206 207 csd_type = CSD_TYPE(csd); 208 if (csd_type == CSD_TYPE_ASYNC || csd_type == CSD_TYPE_SYNC) 209 return csd->node.dst; /* Other CSD_TYPE_ values might not have ->dst. */ 210 return -1; 211 } 212 213 static atomic_t n_csd_lock_stuck; 214 215 /** 216 * csd_lock_is_stuck - Has a CSD-lock acquisition been stuck too long? 217 * 218 * Returns @true if a CSD-lock acquisition is stuck and has been stuck 219 * long enough for a "non-responsive CSD lock" message to be printed. 220 */ 221 bool csd_lock_is_stuck(void) 222 { 223 return !!atomic_read(&n_csd_lock_stuck); 224 } 225 226 /* 227 * Complain if too much time spent waiting. Note that only 228 * the CSD_TYPE_SYNC/ASYNC types provide the destination CPU, 229 * so waiting on other types gets much less information. 230 */ 231 static bool csd_lock_wait_toolong(call_single_data_t *csd, u64 ts0, u64 *ts1, int *bug_id, unsigned long *nmessages) 232 { 233 int cpu = -1; 234 int cpux; 235 bool firsttime; 236 u64 ts2, ts_delta; 237 call_single_data_t *cpu_cur_csd; 238 unsigned int flags = READ_ONCE(csd->node.u_flags); 239 unsigned long long csd_lock_timeout_ns = csd_lock_timeout * NSEC_PER_MSEC; 240 241 if (!(flags & CSD_FLAG_LOCK)) { 242 if (!unlikely(*bug_id)) 243 return true; 244 cpu = csd_lock_wait_getcpu(csd); 245 pr_alert("csd: CSD lock (#%d) got unstuck on CPU#%02d, CPU#%02d released the lock.\n", 246 *bug_id, raw_smp_processor_id(), cpu); 247 atomic_dec(&n_csd_lock_stuck); 248 return true; 249 } 250 251 ts2 = ktime_get_mono_fast_ns(); 252 /* How long since we last checked for a stuck CSD lock.*/ 253 ts_delta = ts2 - *ts1; 254 if (likely(ts_delta <= csd_lock_timeout_ns * (*nmessages + 1) * 255 (!*nmessages ? 1 : (ilog2(num_online_cpus()) / 2 + 1)) || 256 csd_lock_timeout_ns == 0)) 257 return false; 258 259 if (ts0 > ts2) { 260 /* Our own sched_clock went backward; don't blame another CPU. */ 261 ts_delta = ts0 - ts2; 262 pr_alert("sched_clock on CPU %d went backward by %llu ns\n", raw_smp_processor_id(), ts_delta); 263 *ts1 = ts2; 264 return false; 265 } 266 267 firsttime = !*bug_id; 268 if (firsttime) 269 *bug_id = atomic_inc_return(&csd_bug_count); 270 cpu = csd_lock_wait_getcpu(csd); 271 if (WARN_ONCE(cpu < 0 || cpu >= nr_cpu_ids, "%s: cpu = %d\n", __func__, cpu)) 272 cpux = 0; 273 else 274 cpux = cpu; 275 cpu_cur_csd = smp_load_acquire(&per_cpu(cur_csd, cpux)); /* Before func and info. */ 276 /* How long since this CSD lock was stuck. */ 277 ts_delta = ts2 - ts0; 278 pr_alert("csd: %s non-responsive CSD lock (#%d) on CPU#%d, waiting %lld ns for CPU#%02d %pS(%ps).\n", 279 firsttime ? "Detected" : "Continued", *bug_id, raw_smp_processor_id(), (s64)ts_delta, 280 cpu, csd->func, csd->info); 281 (*nmessages)++; 282 if (firsttime) 283 atomic_inc(&n_csd_lock_stuck); 284 /* 285 * If the CSD lock is still stuck after 5 minutes, it is unlikely 286 * to become unstuck. Use a signed comparison to avoid triggering 287 * on underflows when the TSC is out of sync between sockets. 288 */ 289 BUG_ON(panic_on_ipistall > 0 && (s64)ts_delta > ((s64)panic_on_ipistall * NSEC_PER_MSEC)); 290 if (cpu_cur_csd && csd != cpu_cur_csd) { 291 pr_alert("\tcsd: CSD lock (#%d) handling prior %pS(%ps) request.\n", 292 *bug_id, READ_ONCE(per_cpu(cur_csd_func, cpux)), 293 READ_ONCE(per_cpu(cur_csd_info, cpux))); 294 } else { 295 pr_alert("\tcsd: CSD lock (#%d) %s.\n", 296 *bug_id, !cpu_cur_csd ? "unresponsive" : "handling this request"); 297 } 298 if (cpu >= 0) { 299 if (atomic_cmpxchg_acquire(&per_cpu(trigger_backtrace, cpu), 1, 0)) 300 dump_cpu_task(cpu); 301 if (!cpu_cur_csd) { 302 pr_alert("csd: Re-sending CSD lock (#%d) IPI from CPU#%02d to CPU#%02d\n", *bug_id, raw_smp_processor_id(), cpu); 303 arch_send_call_function_single_ipi(cpu); 304 } 305 } 306 if (firsttime) 307 dump_stack(); 308 *ts1 = ts2; 309 310 return false; 311 } 312 313 /* 314 * csd_lock/csd_unlock used to serialize access to per-cpu csd resources 315 * 316 * For non-synchronous ipi calls the csd can still be in use by the 317 * previous function call. For multi-cpu calls its even more interesting 318 * as we'll have to ensure no other cpu is observing our csd. 319 */ 320 static void __csd_lock_wait(call_single_data_t *csd) 321 { 322 unsigned long nmessages = 0; 323 int bug_id = 0; 324 u64 ts0, ts1; 325 326 ts1 = ts0 = ktime_get_mono_fast_ns(); 327 for (;;) { 328 if (csd_lock_wait_toolong(csd, ts0, &ts1, &bug_id, &nmessages)) 329 break; 330 cpu_relax(); 331 } 332 smp_acquire__after_ctrl_dep(); 333 } 334 335 static __always_inline void csd_lock_wait(call_single_data_t *csd) 336 { 337 if (static_branch_unlikely(&csdlock_debug_enabled)) { 338 __csd_lock_wait(csd); 339 return; 340 } 341 342 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); 343 } 344 #else 345 static void csd_lock_record(call_single_data_t *csd) 346 { 347 } 348 349 static __always_inline void csd_lock_wait(call_single_data_t *csd) 350 { 351 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); 352 } 353 #endif 354 355 static __always_inline void csd_lock(call_single_data_t *csd) 356 { 357 csd_lock_wait(csd); 358 csd->node.u_flags |= CSD_FLAG_LOCK; 359 360 /* 361 * prevent CPU from reordering the above assignment 362 * to ->flags with any subsequent assignments to other 363 * fields of the specified call_single_data_t structure: 364 */ 365 smp_wmb(); 366 } 367 368 static __always_inline void csd_unlock(call_single_data_t *csd) 369 { 370 WARN_ON(!(csd->node.u_flags & CSD_FLAG_LOCK)); 371 372 /* 373 * ensure we're all done before releasing data: 374 */ 375 smp_store_release(&csd->node.u_flags, 0); 376 } 377 378 static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data); 379 380 void __smp_call_single_queue(int cpu, struct llist_node *node) 381 { 382 /* 383 * We have to check the type of the CSD before queueing it, because 384 * once queued it can have its flags cleared by 385 * flush_smp_call_function_queue() 386 * even if we haven't sent the smp_call IPI yet (e.g. the stopper 387 * executes migration_cpu_stop() on the remote CPU). 388 */ 389 if (trace_csd_queue_cpu_enabled()) { 390 call_single_data_t *csd; 391 smp_call_func_t func; 392 393 csd = container_of(node, call_single_data_t, node.llist); 394 func = CSD_TYPE(csd) == CSD_TYPE_TTWU ? 395 sched_ttwu_pending : csd->func; 396 397 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); 398 } 399 400 /* 401 * The list addition should be visible to the target CPU when it pops 402 * the head of the list to pull the entry off it in the IPI handler 403 * because of normal cache coherency rules implied by the underlying 404 * llist ops. 405 * 406 * If IPIs can go out of order to the cache coherency protocol 407 * in an architecture, sufficient synchronisation should be added 408 * to arch code to make it appear to obey cache coherency WRT 409 * locking and barrier primitives. Generic code isn't really 410 * equipped to do the right thing... 411 */ 412 if (llist_add(node, &per_cpu(call_single_queue, cpu))) 413 send_call_function_single_ipi(cpu); 414 } 415 416 /* 417 * Insert a previously allocated call_single_data_t element 418 * for execution on the given CPU. data must already have 419 * ->func, ->info, and ->flags set. 420 */ 421 static int generic_exec_single(int cpu, call_single_data_t *csd) 422 { 423 /* 424 * Preemption already disabled here so stopper cannot run on this CPU, 425 * ensuring mutually exclusive CPU offlining and last IPI flush. 426 */ 427 if (cpu == smp_processor_id()) { 428 smp_call_func_t func = csd->func; 429 void *info = csd->info; 430 unsigned long flags; 431 432 /* 433 * We can unlock early even for the synchronous on-stack case, 434 * since we're doing this from the same CPU.. 435 */ 436 csd_lock_record(csd); 437 csd_unlock(csd); 438 local_irq_save(flags); 439 csd_do_func(func, info, NULL); 440 csd_lock_record(NULL); 441 local_irq_restore(flags); 442 return 0; 443 } 444 445 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) { 446 csd_unlock(csd); 447 return -ENXIO; 448 } 449 450 __smp_call_single_queue(cpu, &csd->node.llist); 451 452 return 0; 453 } 454 455 /** 456 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks 457 * 458 * Invoked by arch to handle an IPI for call function single. 459 * Must be called with interrupts disabled. 460 */ 461 void generic_smp_call_function_single_interrupt(void) 462 { 463 __flush_smp_call_function_queue(true); 464 } 465 466 /** 467 * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks 468 * 469 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an 470 * offline CPU. Skip this check if set to 'false'. 471 * 472 * Flush any pending smp-call-function callbacks queued on this CPU. This is 473 * invoked by the generic IPI handler, as well as by a CPU about to go offline, 474 * to ensure that all pending IPI callbacks are run before it goes completely 475 * offline. 476 * 477 * Loop through the call_single_queue and run all the queued callbacks. 478 * Must be called with interrupts disabled. 479 */ 480 static void __flush_smp_call_function_queue(bool warn_cpu_offline) 481 { 482 call_single_data_t *csd, *csd_next; 483 struct llist_node *entry, *prev; 484 struct llist_head *head; 485 static bool warned; 486 atomic_t *tbt; 487 488 lockdep_assert_irqs_disabled(); 489 490 /* Allow waiters to send backtrace NMI from here onwards */ 491 tbt = this_cpu_ptr(&trigger_backtrace); 492 atomic_set_release(tbt, 1); 493 494 head = this_cpu_ptr(&call_single_queue); 495 entry = llist_del_all(head); 496 entry = llist_reverse_order(entry); 497 498 /* There shouldn't be any pending callbacks on an offline CPU. */ 499 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) && 500 !warned && entry != NULL)) { 501 warned = true; 502 WARN(1, "IPI on offline CPU %d\n", smp_processor_id()); 503 504 /* 505 * We don't have to use the _safe() variant here 506 * because we are not invoking the IPI handlers yet. 507 */ 508 llist_for_each_entry(csd, entry, node.llist) { 509 switch (CSD_TYPE(csd)) { 510 case CSD_TYPE_ASYNC: 511 case CSD_TYPE_SYNC: 512 case CSD_TYPE_IRQ_WORK: 513 pr_warn("IPI callback %pS sent to offline CPU\n", 514 csd->func); 515 break; 516 517 case CSD_TYPE_TTWU: 518 pr_warn("IPI task-wakeup sent to offline CPU\n"); 519 break; 520 521 default: 522 pr_warn("IPI callback, unknown type %d, sent to offline CPU\n", 523 CSD_TYPE(csd)); 524 break; 525 } 526 } 527 } 528 529 /* 530 * First; run all SYNC callbacks, people are waiting for us. 531 */ 532 prev = NULL; 533 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { 534 /* Do we wait until *after* callback? */ 535 if (CSD_TYPE(csd) == CSD_TYPE_SYNC) { 536 smp_call_func_t func = csd->func; 537 void *info = csd->info; 538 539 if (prev) { 540 prev->next = &csd_next->node.llist; 541 } else { 542 entry = &csd_next->node.llist; 543 } 544 545 csd_lock_record(csd); 546 csd_do_func(func, info, csd); 547 csd_unlock(csd); 548 csd_lock_record(NULL); 549 } else { 550 prev = &csd->node.llist; 551 } 552 } 553 554 if (!entry) 555 return; 556 557 /* 558 * Second; run all !SYNC callbacks. 559 */ 560 prev = NULL; 561 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { 562 int type = CSD_TYPE(csd); 563 564 if (type != CSD_TYPE_TTWU) { 565 if (prev) { 566 prev->next = &csd_next->node.llist; 567 } else { 568 entry = &csd_next->node.llist; 569 } 570 571 if (type == CSD_TYPE_ASYNC) { 572 smp_call_func_t func = csd->func; 573 void *info = csd->info; 574 575 csd_lock_record(csd); 576 csd_unlock(csd); 577 csd_do_func(func, info, csd); 578 csd_lock_record(NULL); 579 } else if (type == CSD_TYPE_IRQ_WORK) { 580 irq_work_single(csd); 581 } 582 583 } else { 584 prev = &csd->node.llist; 585 } 586 } 587 588 /* 589 * Third; only CSD_TYPE_TTWU is left, issue those. 590 */ 591 if (entry) { 592 csd = llist_entry(entry, typeof(*csd), node.llist); 593 csd_do_func(sched_ttwu_pending, entry, csd); 594 } 595 } 596 597 598 /** 599 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks 600 * from task context (idle, migration thread) 601 * 602 * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it 603 * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by 604 * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to 605 * handle queued SMP function calls before scheduling. 606 * 607 * The migration thread has to ensure that an eventually pending wakeup has 608 * been handled before it migrates a task. 609 */ 610 void flush_smp_call_function_queue(void) 611 { 612 unsigned int was_pending; 613 unsigned long flags; 614 615 if (llist_empty(this_cpu_ptr(&call_single_queue))) 616 return; 617 618 local_irq_save(flags); 619 /* Get the already pending soft interrupts for RT enabled kernels */ 620 was_pending = local_softirq_pending(); 621 __flush_smp_call_function_queue(true); 622 if (local_softirq_pending()) 623 do_softirq_post_smp_call_flush(was_pending); 624 625 local_irq_restore(flags); 626 } 627 628 /* 629 * smp_call_function_single - Run a function on a specific CPU 630 * @func: The function to run. This must be fast and non-blocking. 631 * @info: An arbitrary pointer to pass to the function. 632 * @wait: If true, wait until function has completed on other CPUs. 633 * 634 * Returns 0 on success, else a negative status code. 635 */ 636 int smp_call_function_single(int cpu, smp_call_func_t func, void *info, 637 int wait) 638 { 639 call_single_data_t *csd; 640 call_single_data_t csd_stack = { 641 .node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, }, 642 }; 643 int this_cpu; 644 int err; 645 646 /* 647 * Prevent preemption and reschedule on another CPU, as well as CPU 648 * removal. This prevents stopper from running on this CPU, thus 649 * providing mutual exclusion of the below cpu_online() check and 650 * IPI sending ensuring IPI are not missed by CPU going offline. 651 */ 652 this_cpu = get_cpu(); 653 654 /* 655 * Can deadlock when called with interrupts disabled. 656 * We allow cpu's that are not yet online though, as no one else can 657 * send smp call function interrupt to this cpu and as such deadlocks 658 * can't happen. 659 */ 660 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() 661 && !oops_in_progress); 662 663 /* 664 * When @wait we can deadlock when we interrupt between llist_add() and 665 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to 666 * csd_lock() on because the interrupt context uses the same csd 667 * storage. 668 */ 669 WARN_ON_ONCE(!in_task()); 670 671 csd = &csd_stack; 672 if (!wait) { 673 csd = this_cpu_ptr(&csd_data); 674 csd_lock(csd); 675 } 676 677 csd->func = func; 678 csd->info = info; 679 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 680 csd->node.src = smp_processor_id(); 681 csd->node.dst = cpu; 682 #endif 683 684 err = generic_exec_single(cpu, csd); 685 686 if (wait) 687 csd_lock_wait(csd); 688 689 put_cpu(); 690 691 return err; 692 } 693 EXPORT_SYMBOL(smp_call_function_single); 694 695 /** 696 * smp_call_function_single_async() - Run an asynchronous function on a 697 * specific CPU. 698 * @cpu: The CPU to run on. 699 * @csd: Pre-allocated and setup data structure 700 * 701 * Like smp_call_function_single(), but the call is asynchonous and 702 * can thus be done from contexts with disabled interrupts. 703 * 704 * The caller passes his own pre-allocated data structure 705 * (ie: embedded in an object) and is responsible for synchronizing it 706 * such that the IPIs performed on the @csd are strictly serialized. 707 * 708 * If the function is called with one csd which has not yet been 709 * processed by previous call to smp_call_function_single_async(), the 710 * function will return immediately with -EBUSY showing that the csd 711 * object is still in progress. 712 * 713 * NOTE: Be careful, there is unfortunately no current debugging facility to 714 * validate the correctness of this serialization. 715 * 716 * Return: %0 on success or negative errno value on error 717 */ 718 int smp_call_function_single_async(int cpu, call_single_data_t *csd) 719 { 720 int err = 0; 721 722 preempt_disable(); 723 724 if (csd->node.u_flags & CSD_FLAG_LOCK) { 725 err = -EBUSY; 726 goto out; 727 } 728 729 csd->node.u_flags = CSD_FLAG_LOCK; 730 smp_wmb(); 731 732 err = generic_exec_single(cpu, csd); 733 734 out: 735 preempt_enable(); 736 737 return err; 738 } 739 EXPORT_SYMBOL_GPL(smp_call_function_single_async); 740 741 /* 742 * smp_call_function_any - Run a function on any of the given cpus 743 * @mask: The mask of cpus it can run on. 744 * @func: The function to run. This must be fast and non-blocking. 745 * @info: An arbitrary pointer to pass to the function. 746 * @wait: If true, wait until function has completed. 747 * 748 * Returns 0 on success, else a negative status code (if no cpus were online). 749 * 750 * Selection preference: 751 * 1) current cpu if in @mask 752 * 2) nearest cpu in @mask, based on NUMA topology 753 */ 754 int smp_call_function_any(const struct cpumask *mask, 755 smp_call_func_t func, void *info, int wait) 756 { 757 unsigned int cpu; 758 int ret; 759 760 /* Try for same CPU (cheapest) */ 761 cpu = get_cpu(); 762 if (!cpumask_test_cpu(cpu, mask)) 763 cpu = sched_numa_find_nth_cpu(mask, 0, cpu_to_node(cpu)); 764 765 ret = smp_call_function_single(cpu, func, info, wait); 766 put_cpu(); 767 return ret; 768 } 769 EXPORT_SYMBOL_GPL(smp_call_function_any); 770 771 /* 772 * Flags to be used as scf_flags argument of smp_call_function_many_cond(). 773 * 774 * %SCF_WAIT: Wait until function execution is completed 775 * %SCF_RUN_LOCAL: Run also locally if local cpu is set in cpumask 776 */ 777 #define SCF_WAIT (1U << 0) 778 #define SCF_RUN_LOCAL (1U << 1) 779 780 static void smp_call_function_many_cond(const struct cpumask *mask, 781 smp_call_func_t func, void *info, 782 unsigned int scf_flags, 783 smp_cond_func_t cond_func) 784 { 785 int cpu, last_cpu, this_cpu = smp_processor_id(); 786 struct call_function_data *cfd; 787 bool wait = scf_flags & SCF_WAIT; 788 int nr_cpus = 0; 789 bool run_remote = false; 790 791 lockdep_assert_preemption_disabled(); 792 793 /* 794 * Can deadlock when called with interrupts disabled. 795 * We allow cpu's that are not yet online though, as no one else can 796 * send smp call function interrupt to this cpu and as such deadlocks 797 * can't happen. 798 */ 799 if (cpu_online(this_cpu) && !oops_in_progress && 800 !early_boot_irqs_disabled) 801 lockdep_assert_irqs_enabled(); 802 803 /* 804 * When @wait we can deadlock when we interrupt between llist_add() and 805 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to 806 * csd_lock() on because the interrupt context uses the same csd 807 * storage. 808 */ 809 WARN_ON_ONCE(!in_task()); 810 811 /* Check if we need remote execution, i.e., any CPU excluding this one. */ 812 if (cpumask_any_and_but(mask, cpu_online_mask, this_cpu) < nr_cpu_ids) { 813 cfd = this_cpu_ptr(&cfd_data); 814 cpumask_and(cfd->cpumask, mask, cpu_online_mask); 815 __cpumask_clear_cpu(this_cpu, cfd->cpumask); 816 817 cpumask_clear(cfd->cpumask_ipi); 818 for_each_cpu(cpu, cfd->cpumask) { 819 call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu); 820 821 if (cond_func && !cond_func(cpu, info)) { 822 __cpumask_clear_cpu(cpu, cfd->cpumask); 823 continue; 824 } 825 826 /* Work is enqueued on a remote CPU. */ 827 run_remote = true; 828 829 csd_lock(csd); 830 if (wait) 831 csd->node.u_flags |= CSD_TYPE_SYNC; 832 csd->func = func; 833 csd->info = info; 834 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 835 csd->node.src = smp_processor_id(); 836 csd->node.dst = cpu; 837 #endif 838 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); 839 840 /* 841 * Kick the remote CPU if this is the first work 842 * item enqueued. 843 */ 844 if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) { 845 __cpumask_set_cpu(cpu, cfd->cpumask_ipi); 846 nr_cpus++; 847 last_cpu = cpu; 848 } 849 } 850 851 /* 852 * Choose the most efficient way to send an IPI. Note that the 853 * number of CPUs might be zero due to concurrent changes to the 854 * provided mask. 855 */ 856 if (nr_cpus == 1) 857 send_call_function_single_ipi(last_cpu); 858 else if (likely(nr_cpus > 1)) 859 send_call_function_ipi_mask(cfd->cpumask_ipi); 860 } 861 862 /* Check if we need local execution. */ 863 if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask) && 864 (!cond_func || cond_func(this_cpu, info))) { 865 unsigned long flags; 866 867 local_irq_save(flags); 868 csd_do_func(func, info, NULL); 869 local_irq_restore(flags); 870 } 871 872 if (run_remote && wait) { 873 for_each_cpu(cpu, cfd->cpumask) { 874 call_single_data_t *csd; 875 876 csd = per_cpu_ptr(cfd->csd, cpu); 877 csd_lock_wait(csd); 878 } 879 } 880 } 881 882 /** 883 * smp_call_function_many(): Run a function on a set of CPUs. 884 * @mask: The set of cpus to run on (only runs on online subset). 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 * You must not call this function with disabled interrupts or from a 891 * hardware interrupt handler or from a bottom half handler. Preemption 892 * must be disabled when calling this function. 893 * 894 * @func is not called on the local CPU even if @mask contains it. Consider 895 * using on_each_cpu_cond_mask() instead if this is not desirable. 896 */ 897 void smp_call_function_many(const struct cpumask *mask, 898 smp_call_func_t func, void *info, bool wait) 899 { 900 smp_call_function_many_cond(mask, func, info, wait * SCF_WAIT, NULL); 901 } 902 EXPORT_SYMBOL(smp_call_function_many); 903 904 /** 905 * smp_call_function(): Run a function on all other CPUs. 906 * @func: The function to run. This must be fast and non-blocking. 907 * @info: An arbitrary pointer to pass to the function. 908 * @wait: If true, wait (atomically) until function has completed 909 * on other CPUs. 910 * 911 * Returns 0. 912 * 913 * If @wait is true, then returns once @func has returned; otherwise 914 * it returns just before the target cpu calls @func. 915 * 916 * You must not call this function with disabled interrupts or from a 917 * hardware interrupt handler or from a bottom half handler. 918 */ 919 void smp_call_function(smp_call_func_t func, void *info, int wait) 920 { 921 preempt_disable(); 922 smp_call_function_many(cpu_online_mask, func, info, wait); 923 preempt_enable(); 924 } 925 EXPORT_SYMBOL(smp_call_function); 926 927 /* Setup configured maximum number of CPUs to activate */ 928 unsigned int setup_max_cpus = NR_CPUS; 929 EXPORT_SYMBOL(setup_max_cpus); 930 931 932 /* 933 * Setup routine for controlling SMP activation 934 * 935 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP 936 * activation entirely (the MPS table probe still happens, though). 937 * 938 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer 939 * greater than 0, limits the maximum number of CPUs activated in 940 * SMP mode to <NUM>. 941 */ 942 943 void __weak __init arch_disable_smp_support(void) { } 944 945 static int __init nosmp(char *str) 946 { 947 setup_max_cpus = 0; 948 arch_disable_smp_support(); 949 950 return 0; 951 } 952 953 early_param("nosmp", nosmp); 954 955 /* this is hard limit */ 956 static int __init nrcpus(char *str) 957 { 958 int nr_cpus; 959 960 if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids) 961 set_nr_cpu_ids(nr_cpus); 962 963 return 0; 964 } 965 966 early_param("nr_cpus", nrcpus); 967 968 static int __init maxcpus(char *str) 969 { 970 get_option(&str, &setup_max_cpus); 971 if (setup_max_cpus == 0) 972 arch_disable_smp_support(); 973 974 return 0; 975 } 976 977 early_param("maxcpus", maxcpus); 978 979 #if (NR_CPUS > 1) && !defined(CONFIG_FORCE_NR_CPUS) 980 /* Setup number of possible processor ids */ 981 unsigned int nr_cpu_ids __read_mostly = NR_CPUS; 982 EXPORT_SYMBOL(nr_cpu_ids); 983 #endif 984 985 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */ 986 void __init setup_nr_cpu_ids(void) 987 { 988 set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1); 989 } 990 991 /* Called by boot processor to activate the rest. */ 992 void __init smp_init(void) 993 { 994 int num_nodes, num_cpus; 995 996 idle_threads_init(); 997 cpuhp_threads_init(); 998 999 pr_info("Bringing up secondary CPUs ...\n"); 1000 1001 bringup_nonboot_cpus(setup_max_cpus); 1002 1003 num_nodes = num_online_nodes(); 1004 num_cpus = num_online_cpus(); 1005 pr_info("Brought up %d node%s, %d CPU%s\n", 1006 num_nodes, str_plural(num_nodes), num_cpus, str_plural(num_cpus)); 1007 1008 /* Any cleanup work */ 1009 smp_cpus_done(setup_max_cpus); 1010 } 1011 1012 /* 1013 * on_each_cpu_cond(): Call a function on each processor for which 1014 * the supplied function cond_func returns true, optionally waiting 1015 * for all the required CPUs to finish. This may include the local 1016 * processor. 1017 * @cond_func: A callback function that is passed a cpu id and 1018 * the info parameter. The function is called 1019 * with preemption disabled. The function should 1020 * return a boolean value indicating whether to IPI 1021 * the specified CPU. 1022 * @func: The function to run on all applicable CPUs. 1023 * This must be fast and non-blocking. 1024 * @info: An arbitrary pointer to pass to both functions. 1025 * @wait: If true, wait (atomically) until function has 1026 * completed on other CPUs. 1027 * 1028 * Preemption is disabled to protect against CPUs going offline but not online. 1029 * CPUs going online during the call will not be seen or sent an IPI. 1030 * 1031 * You must not call this function with disabled interrupts or 1032 * from a hardware interrupt handler or from a bottom half handler. 1033 */ 1034 void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func, 1035 void *info, bool wait, const struct cpumask *mask) 1036 { 1037 unsigned int scf_flags = SCF_RUN_LOCAL; 1038 1039 if (wait) 1040 scf_flags |= SCF_WAIT; 1041 1042 preempt_disable(); 1043 smp_call_function_many_cond(mask, func, info, scf_flags, cond_func); 1044 preempt_enable(); 1045 } 1046 EXPORT_SYMBOL(on_each_cpu_cond_mask); 1047 1048 static void do_nothing(void *unused) 1049 { 1050 } 1051 1052 /** 1053 * kick_all_cpus_sync - Force all cpus out of idle 1054 * 1055 * Used to synchronize the update of pm_idle function pointer. It's 1056 * called after the pointer is updated and returns after the dummy 1057 * callback function has been executed on all cpus. The execution of 1058 * the function can only happen on the remote cpus after they have 1059 * left the idle function which had been called via pm_idle function 1060 * pointer. So it's guaranteed that nothing uses the previous pointer 1061 * anymore. 1062 */ 1063 void kick_all_cpus_sync(void) 1064 { 1065 /* Make sure the change is visible before we kick the cpus */ 1066 smp_mb(); 1067 smp_call_function(do_nothing, NULL, 1); 1068 } 1069 EXPORT_SYMBOL_GPL(kick_all_cpus_sync); 1070 1071 /** 1072 * wake_up_all_idle_cpus - break all cpus out of idle 1073 * wake_up_all_idle_cpus try to break all cpus which is in idle state even 1074 * including idle polling cpus, for non-idle cpus, we will do nothing 1075 * for them. 1076 */ 1077 void wake_up_all_idle_cpus(void) 1078 { 1079 int cpu; 1080 1081 for_each_possible_cpu(cpu) { 1082 preempt_disable(); 1083 if (cpu != smp_processor_id() && cpu_online(cpu)) 1084 wake_up_if_idle(cpu); 1085 preempt_enable(); 1086 } 1087 } 1088 EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus); 1089 1090 /** 1091 * struct smp_call_on_cpu_struct - Call a function on a specific CPU 1092 * @work: &work_struct 1093 * @done: &completion to signal 1094 * @func: function to call 1095 * @data: function's data argument 1096 * @ret: return value from @func 1097 * @cpu: target CPU (%-1 for any CPU) 1098 * 1099 * Used to call a function on a specific cpu and wait for it to return. 1100 * Optionally make sure the call is done on a specified physical cpu via vcpu 1101 * pinning in order to support virtualized environments. 1102 */ 1103 struct smp_call_on_cpu_struct { 1104 struct work_struct work; 1105 struct completion done; 1106 int (*func)(void *); 1107 void *data; 1108 int ret; 1109 int cpu; 1110 }; 1111 1112 static void smp_call_on_cpu_callback(struct work_struct *work) 1113 { 1114 struct smp_call_on_cpu_struct *sscs; 1115 1116 sscs = container_of(work, struct smp_call_on_cpu_struct, work); 1117 if (sscs->cpu >= 0) 1118 hypervisor_pin_vcpu(sscs->cpu); 1119 sscs->ret = sscs->func(sscs->data); 1120 if (sscs->cpu >= 0) 1121 hypervisor_pin_vcpu(-1); 1122 1123 complete(&sscs->done); 1124 } 1125 1126 int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys) 1127 { 1128 struct smp_call_on_cpu_struct sscs = { 1129 .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done), 1130 .func = func, 1131 .data = par, 1132 .cpu = phys ? cpu : -1, 1133 }; 1134 1135 INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback); 1136 1137 if (cpu >= nr_cpu_ids || !cpu_online(cpu)) 1138 return -ENXIO; 1139 1140 queue_work_on(cpu, system_wq, &sscs.work); 1141 wait_for_completion(&sscs.done); 1142 destroy_work_on_stack(&sscs.work); 1143 1144 return sscs.ret; 1145 } 1146 EXPORT_SYMBOL_GPL(smp_call_on_cpu); 1147