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 static DEFINE_STATIC_KEY_MAYBE(CONFIG_CSD_LOCK_WAIT_DEBUG_DEFAULT, csdlock_debug_enabled); 141 142 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 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 __always_inline void __csd_lock_wait(call_single_data_t *csd) 346 { 347 } 348 349 static void csd_lock_record(call_single_data_t *csd) 350 { 351 } 352 353 static __always_inline void csd_lock_wait(call_single_data_t *csd) 354 { 355 smp_cond_load_acquire(&csd->node.u_flags, !(VAL & CSD_FLAG_LOCK)); 356 } 357 #endif 358 359 static __always_inline void csd_lock(call_single_data_t *csd) 360 { 361 if (IS_ENABLED(CONFIG_CSD_LOCK_WAIT_DEBUG) && 362 static_branch_unlikely(&csdlock_debug_enabled)) { 363 364 for (;;) { 365 unsigned int flags; 366 367 __csd_lock_wait(csd); 368 flags = READ_ONCE(csd->node.u_flags); 369 370 if (!(flags & CSD_FLAG_LOCK) && 371 try_cmpxchg_acquire(&csd->node.u_flags, &flags, flags | CSD_FLAG_LOCK)) 372 break; 373 } 374 } else { 375 csd_lock_wait(csd); 376 csd->node.u_flags |= CSD_FLAG_LOCK; 377 } 378 379 /* 380 * prevent CPU from reordering the above assignment 381 * to ->flags with any subsequent assignments to other 382 * fields of the specified call_single_data_t structure: 383 */ 384 smp_wmb(); 385 } 386 387 static __always_inline void csd_unlock(call_single_data_t *csd) 388 { 389 WARN_ON(!(csd->node.u_flags & CSD_FLAG_LOCK)); 390 391 /* 392 * ensure we're all done before releasing data: 393 */ 394 smp_store_release(&csd->node.u_flags, 0); 395 } 396 397 static DEFINE_PER_CPU_SHARED_ALIGNED(call_single_data_t, csd_data); 398 399 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 400 static call_single_data_t *get_single_csd_data(int cpu) 401 { 402 if (static_branch_unlikely(&csdlock_debug_enabled) && 403 (unsigned int)cpu < nr_cpu_ids) 404 return per_cpu_ptr(&csd_data, cpu); 405 return this_cpu_ptr(&csd_data); 406 } 407 #else 408 static call_single_data_t *get_single_csd_data(int cpu) 409 { 410 return this_cpu_ptr(&csd_data); 411 } 412 #endif 413 414 void __smp_call_single_queue(int cpu, struct llist_node *node) 415 { 416 /* 417 * We have to check the type of the CSD before queueing it, because 418 * once queued it can have its flags cleared by 419 * flush_smp_call_function_queue() 420 * even if we haven't sent the smp_call IPI yet (e.g. the stopper 421 * executes migration_cpu_stop() on the remote CPU). 422 */ 423 if (trace_csd_queue_cpu_enabled()) { 424 call_single_data_t *csd; 425 smp_call_func_t func; 426 427 csd = container_of(node, call_single_data_t, node.llist); 428 func = CSD_TYPE(csd) == CSD_TYPE_TTWU ? 429 sched_ttwu_pending : csd->func; 430 431 trace_call__csd_queue_cpu(cpu, _RET_IP_, func, csd); 432 } 433 434 /* 435 * The list addition should be visible to the target CPU when it pops 436 * the head of the list to pull the entry off it in the IPI handler 437 * because of normal cache coherency rules implied by the underlying 438 * llist ops. 439 * 440 * If IPIs can go out of order to the cache coherency protocol 441 * in an architecture, sufficient synchronisation should be added 442 * to arch code to make it appear to obey cache coherency WRT 443 * locking and barrier primitives. Generic code isn't really 444 * equipped to do the right thing... 445 */ 446 if (llist_add(node, &per_cpu(call_single_queue, cpu))) 447 send_call_function_single_ipi(cpu); 448 } 449 450 /* 451 * Insert a previously allocated call_single_data_t element 452 * for execution on the given CPU. data must already have 453 * ->func, ->info, and ->flags set. 454 */ 455 static int generic_exec_single(int cpu, call_single_data_t *csd) 456 { 457 /* 458 * Preemption already disabled here so stopper cannot run on this CPU, 459 * ensuring mutually exclusive CPU offlining and last IPI flush. 460 */ 461 if (cpu == smp_processor_id()) { 462 smp_call_func_t func = csd->func; 463 void *info = csd->info; 464 unsigned long flags; 465 466 /* 467 * We can unlock early even for the synchronous on-stack case, 468 * since we're doing this from the same CPU.. 469 */ 470 csd_lock_record(csd); 471 csd_unlock(csd); 472 local_irq_save(flags); 473 csd_do_func(func, info, NULL); 474 csd_lock_record(NULL); 475 local_irq_restore(flags); 476 return 0; 477 } 478 479 if ((unsigned)cpu >= nr_cpu_ids || !cpu_online(cpu)) { 480 csd_unlock(csd); 481 return -ENXIO; 482 } 483 484 __smp_call_single_queue(cpu, &csd->node.llist); 485 486 return 0; 487 } 488 489 /** 490 * generic_smp_call_function_single_interrupt - Execute SMP IPI callbacks 491 * 492 * Invoked by arch to handle an IPI for call function single. 493 * Must be called with interrupts disabled. 494 */ 495 void generic_smp_call_function_single_interrupt(void) 496 { 497 __flush_smp_call_function_queue(true); 498 } 499 500 /** 501 * __flush_smp_call_function_queue - Flush pending smp-call-function callbacks 502 * 503 * @warn_cpu_offline: If set to 'true', warn if callbacks were queued on an 504 * offline CPU. Skip this check if set to 'false'. 505 * 506 * Flush any pending smp-call-function callbacks queued on this CPU. This is 507 * invoked by the generic IPI handler, as well as by a CPU about to go offline, 508 * to ensure that all pending IPI callbacks are run before it goes completely 509 * offline. 510 * 511 * Loop through the call_single_queue and run all the queued callbacks. 512 * Must be called with interrupts disabled. 513 */ 514 static void __flush_smp_call_function_queue(bool warn_cpu_offline) 515 { 516 call_single_data_t *csd, *csd_next; 517 struct llist_node *entry, *prev; 518 struct llist_head *head; 519 static bool warned; 520 atomic_t *tbt; 521 522 lockdep_assert_irqs_disabled(); 523 524 /* Allow waiters to send backtrace NMI from here onwards */ 525 tbt = this_cpu_ptr(&trigger_backtrace); 526 atomic_set_release(tbt, 1); 527 528 head = this_cpu_ptr(&call_single_queue); 529 entry = llist_del_all(head); 530 entry = llist_reverse_order(entry); 531 532 /* There shouldn't be any pending callbacks on an offline CPU. */ 533 if (unlikely(warn_cpu_offline && !cpu_online(smp_processor_id()) && 534 !warned && entry != NULL)) { 535 warned = true; 536 WARN(1, "IPI on offline CPU %d\n", smp_processor_id()); 537 538 /* 539 * We don't have to use the _safe() variant here 540 * because we are not invoking the IPI handlers yet. 541 */ 542 llist_for_each_entry(csd, entry, node.llist) { 543 switch (CSD_TYPE(csd)) { 544 case CSD_TYPE_ASYNC: 545 case CSD_TYPE_SYNC: 546 case CSD_TYPE_IRQ_WORK: 547 pr_warn("IPI callback %pS sent to offline CPU\n", 548 csd->func); 549 break; 550 551 case CSD_TYPE_TTWU: 552 pr_warn("IPI task-wakeup sent to offline CPU\n"); 553 break; 554 555 default: 556 pr_warn("IPI callback, unknown type %d, sent to offline CPU\n", 557 CSD_TYPE(csd)); 558 break; 559 } 560 } 561 } 562 563 /* 564 * First; run all SYNC callbacks, people are waiting for us. 565 */ 566 prev = NULL; 567 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { 568 /* Do we wait until *after* callback? */ 569 if (CSD_TYPE(csd) == CSD_TYPE_SYNC) { 570 smp_call_func_t func = csd->func; 571 void *info = csd->info; 572 573 if (prev) { 574 prev->next = &csd_next->node.llist; 575 } else { 576 entry = &csd_next->node.llist; 577 } 578 579 csd_lock_record(csd); 580 csd_do_func(func, info, csd); 581 csd_unlock(csd); 582 csd_lock_record(NULL); 583 } else { 584 prev = &csd->node.llist; 585 } 586 } 587 588 if (!entry) 589 return; 590 591 /* 592 * Second; run all !SYNC callbacks. 593 */ 594 prev = NULL; 595 llist_for_each_entry_safe(csd, csd_next, entry, node.llist) { 596 int type = CSD_TYPE(csd); 597 598 if (type != CSD_TYPE_TTWU) { 599 if (prev) { 600 prev->next = &csd_next->node.llist; 601 } else { 602 entry = &csd_next->node.llist; 603 } 604 605 if (type == CSD_TYPE_ASYNC) { 606 smp_call_func_t func = csd->func; 607 void *info = csd->info; 608 609 csd_lock_record(csd); 610 csd_unlock(csd); 611 csd_do_func(func, info, csd); 612 csd_lock_record(NULL); 613 } else if (type == CSD_TYPE_IRQ_WORK) { 614 irq_work_single(csd); 615 } 616 617 } else { 618 prev = &csd->node.llist; 619 } 620 } 621 622 /* 623 * Third; only CSD_TYPE_TTWU is left, issue those. 624 */ 625 if (entry) { 626 csd = llist_entry(entry, typeof(*csd), node.llist); 627 csd_do_func(sched_ttwu_pending, entry, csd); 628 } 629 } 630 631 632 /** 633 * flush_smp_call_function_queue - Flush pending smp-call-function callbacks 634 * from task context (idle, migration thread) 635 * 636 * When TIF_POLLING_NRFLAG is supported and a CPU is in idle and has it 637 * set, then remote CPUs can avoid sending IPIs and wake the idle CPU by 638 * setting TIF_NEED_RESCHED. The idle task on the woken up CPU has to 639 * handle queued SMP function calls before scheduling. 640 * 641 * The migration thread has to ensure that an eventually pending wakeup has 642 * been handled before it migrates a task. 643 */ 644 void flush_smp_call_function_queue(void) 645 { 646 unsigned int was_pending; 647 unsigned long flags; 648 649 if (llist_empty(this_cpu_ptr(&call_single_queue))) 650 return; 651 652 local_irq_save(flags); 653 /* Get the already pending soft interrupts for RT enabled kernels */ 654 was_pending = local_softirq_pending(); 655 __flush_smp_call_function_queue(true); 656 if (local_softirq_pending()) 657 do_softirq_post_smp_call_flush(was_pending); 658 659 local_irq_restore(flags); 660 } 661 662 /** 663 * smp_call_function_single - Run a function on a specific CPU 664 * @cpu: Specific target CPU for this function. 665 * @func: The function to run. This must be fast and non-blocking. 666 * @info: An arbitrary pointer to pass to the function. 667 * @wait: If true, wait until function has completed on other CPUs. 668 * 669 * Returns: %0 on success, else a negative status code. 670 */ 671 int smp_call_function_single(int cpu, smp_call_func_t func, void *info, 672 int wait) 673 { 674 call_single_data_t *csd; 675 call_single_data_t csd_stack = { 676 .node = { .u_flags = CSD_FLAG_LOCK | CSD_TYPE_SYNC, }, 677 }; 678 int this_cpu; 679 int err; 680 681 /* 682 * Prevent preemption and reschedule on another CPU, as well as CPU 683 * removal. This prevents stopper from running on this CPU, thus 684 * providing mutual exclusion of the below cpu_online() check and 685 * IPI sending ensuring IPI are not missed by CPU going offline. 686 */ 687 this_cpu = get_cpu(); 688 689 /* 690 * Can deadlock when called with interrupts disabled. 691 * We allow cpu's that are not yet online though, as no one else can 692 * send smp call function interrupt to this cpu and as such deadlocks 693 * can't happen. 694 */ 695 WARN_ON_ONCE(cpu_online(this_cpu) && irqs_disabled() 696 && !oops_in_progress); 697 698 /* 699 * When @wait we can deadlock when we interrupt between llist_add() and 700 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to 701 * csd_lock() on because the interrupt context uses the same csd 702 * storage. 703 */ 704 WARN_ON_ONCE(!in_task()); 705 706 csd = &csd_stack; 707 if (!wait) { 708 csd = get_single_csd_data(cpu); 709 csd_lock(csd); 710 } 711 712 csd->func = func; 713 csd->info = info; 714 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 715 csd->node.src = this_cpu; 716 csd->node.dst = cpu; 717 #endif 718 719 err = generic_exec_single(cpu, csd); 720 721 if (wait) 722 csd_lock_wait(csd); 723 724 put_cpu(); 725 726 return err; 727 } 728 EXPORT_SYMBOL(smp_call_function_single); 729 730 /** 731 * smp_call_function_single_async() - Run an asynchronous function on a 732 * specific CPU. 733 * @cpu: The CPU to run on. 734 * @csd: Pre-allocated and setup data structure 735 * 736 * Like smp_call_function_single(), but the call is asynchonous and 737 * can thus be done from contexts with disabled interrupts. 738 * 739 * The caller passes his own pre-allocated data structure 740 * (ie: embedded in an object) and is responsible for synchronizing it 741 * such that the IPIs performed on the @csd are strictly serialized. 742 * 743 * If the function is called with one csd which has not yet been 744 * processed by previous call to smp_call_function_single_async(), the 745 * function will return immediately with -EBUSY showing that the csd 746 * object is still in progress. 747 * 748 * NOTE: Be careful, there is unfortunately no current debugging facility to 749 * validate the correctness of this serialization. 750 * 751 * Return: %0 on success or negative errno value on error 752 */ 753 int smp_call_function_single_async(int cpu, call_single_data_t *csd) 754 { 755 int err = 0; 756 757 preempt_disable(); 758 759 if (csd->node.u_flags & CSD_FLAG_LOCK) { 760 err = -EBUSY; 761 goto out; 762 } 763 764 csd->node.u_flags = CSD_FLAG_LOCK; 765 smp_wmb(); 766 767 err = generic_exec_single(cpu, csd); 768 769 out: 770 preempt_enable(); 771 772 return err; 773 } 774 EXPORT_SYMBOL_GPL(smp_call_function_single_async); 775 776 /** 777 * smp_call_function_any - Run a function on any of the given cpus 778 * @mask: The mask of cpus it can run on. 779 * @func: The function to run. This must be fast and non-blocking. 780 * @info: An arbitrary pointer to pass to the function. 781 * @wait: If true, wait until function has completed. 782 * 783 * Selection preference: 784 * 1) current cpu if in @mask 785 * 2) nearest cpu in @mask, based on NUMA topology 786 * 787 * Returns: %0 on success, else a negative status code (if no cpus were online). 788 */ 789 int smp_call_function_any(const struct cpumask *mask, 790 smp_call_func_t func, void *info, int wait) 791 { 792 unsigned int cpu; 793 int ret; 794 795 /* Try for same CPU (cheapest) */ 796 cpu = get_cpu(); 797 if (!cpumask_test_cpu(cpu, mask)) 798 cpu = sched_numa_find_nth_cpu(mask, 0, cpu_to_node(cpu)); 799 800 ret = smp_call_function_single(cpu, func, info, wait); 801 put_cpu(); 802 return ret; 803 } 804 EXPORT_SYMBOL_GPL(smp_call_function_any); 805 806 /* 807 * Flags to be used as scf_flags argument of smp_call_function_many_cond(). 808 * 809 * %SCF_WAIT: Wait until function execution is completed 810 * %SCF_RUN_LOCAL: Run also locally if local cpu is set in cpumask 811 */ 812 #define SCF_WAIT (1U << 0) 813 #define SCF_RUN_LOCAL (1U << 1) 814 815 static void smp_call_function_many_cond(const struct cpumask *mask, 816 smp_call_func_t func, void *info, 817 unsigned int scf_flags, 818 smp_cond_func_t cond_func) 819 { 820 int cpu, last_cpu, this_cpu = smp_processor_id(); 821 struct call_function_data *cfd; 822 bool wait = scf_flags & SCF_WAIT; 823 int nr_cpus = 0; 824 bool run_remote = false; 825 826 lockdep_assert_preemption_disabled(); 827 828 /* 829 * Can deadlock when called with interrupts disabled. 830 * We allow cpu's that are not yet online though, as no one else can 831 * send smp call function interrupt to this cpu and as such deadlocks 832 * can't happen. 833 */ 834 if (cpu_online(this_cpu) && !oops_in_progress && 835 !early_boot_irqs_disabled) 836 lockdep_assert_irqs_enabled(); 837 838 /* 839 * When @wait we can deadlock when we interrupt between llist_add() and 840 * arch_send_call_function_ipi*(); when !@wait we can deadlock due to 841 * csd_lock() on because the interrupt context uses the same csd 842 * storage. 843 */ 844 WARN_ON_ONCE(!in_task()); 845 846 /* Check if we need remote execution, i.e., any CPU excluding this one. */ 847 if (cpumask_any_and_but(mask, cpu_online_mask, this_cpu) < nr_cpu_ids) { 848 cfd = this_cpu_ptr(&cfd_data); 849 cpumask_and(cfd->cpumask, mask, cpu_online_mask); 850 __cpumask_clear_cpu(this_cpu, cfd->cpumask); 851 852 cpumask_clear(cfd->cpumask_ipi); 853 for_each_cpu(cpu, cfd->cpumask) { 854 call_single_data_t *csd = per_cpu_ptr(cfd->csd, cpu); 855 856 if (cond_func && !cond_func(cpu, info)) { 857 __cpumask_clear_cpu(cpu, cfd->cpumask); 858 continue; 859 } 860 861 /* Work is enqueued on a remote CPU. */ 862 run_remote = true; 863 864 csd_lock(csd); 865 if (wait) 866 csd->node.u_flags |= CSD_TYPE_SYNC; 867 csd->func = func; 868 csd->info = info; 869 #ifdef CONFIG_CSD_LOCK_WAIT_DEBUG 870 csd->node.src = this_cpu; 871 csd->node.dst = cpu; 872 #endif 873 trace_csd_queue_cpu(cpu, _RET_IP_, func, csd); 874 875 /* 876 * Kick the remote CPU if this is the first work 877 * item enqueued. 878 */ 879 if (llist_add(&csd->node.llist, &per_cpu(call_single_queue, cpu))) { 880 __cpumask_set_cpu(cpu, cfd->cpumask_ipi); 881 nr_cpus++; 882 last_cpu = cpu; 883 } 884 } 885 886 /* 887 * Choose the most efficient way to send an IPI. Note that the 888 * number of CPUs might be zero due to concurrent changes to the 889 * provided mask. 890 */ 891 if (nr_cpus == 1) 892 send_call_function_single_ipi(last_cpu); 893 else if (likely(nr_cpus > 1)) 894 send_call_function_ipi_mask(cfd->cpumask_ipi); 895 } 896 897 /* Check if we need local execution. */ 898 if ((scf_flags & SCF_RUN_LOCAL) && cpumask_test_cpu(this_cpu, mask) && 899 (!cond_func || cond_func(this_cpu, info))) { 900 unsigned long flags; 901 902 local_irq_save(flags); 903 csd_do_func(func, info, NULL); 904 local_irq_restore(flags); 905 } 906 907 if (run_remote && wait) { 908 for_each_cpu(cpu, cfd->cpumask) { 909 call_single_data_t *csd; 910 911 csd = per_cpu_ptr(cfd->csd, cpu); 912 csd_lock_wait(csd); 913 } 914 } 915 } 916 917 /** 918 * smp_call_function_many() - Run a function on a set of CPUs. 919 * @mask: The set of cpus to run on (only runs on online subset). 920 * @func: The function to run. This must be fast and non-blocking. 921 * @info: An arbitrary pointer to pass to the function. 922 * @wait: If true, wait (atomically) until function has completed 923 * on other CPUs. 924 * 925 * You must not call this function with disabled interrupts or from a 926 * hardware interrupt handler or from a bottom half handler. Preemption 927 * must be disabled when calling this function. 928 * 929 * @func is not called on the local CPU even if @mask contains it. Consider 930 * using on_each_cpu_cond_mask() instead if this is not desirable. 931 */ 932 void smp_call_function_many(const struct cpumask *mask, 933 smp_call_func_t func, void *info, bool wait) 934 { 935 smp_call_function_many_cond(mask, func, info, wait * SCF_WAIT, NULL); 936 } 937 EXPORT_SYMBOL(smp_call_function_many); 938 939 /** 940 * smp_call_function() - Run a function on all other CPUs. 941 * @func: The function to run. This must be fast and non-blocking. 942 * @info: An arbitrary pointer to pass to the function. 943 * @wait: If true, wait (atomically) until function has completed 944 * on other CPUs. 945 * 946 * If @wait is true, then returns once @func has returned; otherwise 947 * it returns just before the target cpu calls @func. 948 * 949 * You must not call this function with disabled interrupts or from a 950 * hardware interrupt handler or from a bottom half handler. 951 */ 952 void smp_call_function(smp_call_func_t func, void *info, int wait) 953 { 954 preempt_disable(); 955 smp_call_function_many(cpu_online_mask, func, info, wait); 956 preempt_enable(); 957 } 958 EXPORT_SYMBOL(smp_call_function); 959 960 /* Setup configured maximum number of CPUs to activate */ 961 unsigned int setup_max_cpus = NR_CPUS; 962 EXPORT_SYMBOL(setup_max_cpus); 963 964 965 /* 966 * Setup routine for controlling SMP activation 967 * 968 * Command-line option of "nosmp" or "maxcpus=0" will disable SMP 969 * activation entirely (the MPS table probe still happens, though). 970 * 971 * Command-line option of "maxcpus=<NUM>", where <NUM> is an integer 972 * greater than 0, limits the maximum number of CPUs activated in 973 * SMP mode to <NUM>. 974 */ 975 976 void __weak __init arch_disable_smp_support(void) { } 977 978 static int __init nosmp(char *str) 979 { 980 setup_max_cpus = 0; 981 arch_disable_smp_support(); 982 983 return 0; 984 } 985 986 early_param("nosmp", nosmp); 987 988 /* this is hard limit */ 989 static int __init nrcpus(char *str) 990 { 991 int nr_cpus; 992 993 if (get_option(&str, &nr_cpus) && nr_cpus > 0 && nr_cpus < nr_cpu_ids) 994 set_nr_cpu_ids(nr_cpus); 995 996 return 0; 997 } 998 999 early_param("nr_cpus", nrcpus); 1000 1001 static int __init maxcpus(char *str) 1002 { 1003 get_option(&str, &setup_max_cpus); 1004 if (setup_max_cpus == 0) 1005 arch_disable_smp_support(); 1006 1007 return 0; 1008 } 1009 1010 early_param("maxcpus", maxcpus); 1011 1012 #if (NR_CPUS > 1) && !defined(CONFIG_FORCE_NR_CPUS) 1013 /* Setup number of possible processor ids */ 1014 unsigned int nr_cpu_ids __read_mostly = NR_CPUS; 1015 EXPORT_SYMBOL(nr_cpu_ids); 1016 #endif 1017 1018 /* An arch may set nr_cpu_ids earlier if needed, so this would be redundant */ 1019 void __init setup_nr_cpu_ids(void) 1020 { 1021 set_nr_cpu_ids(find_last_bit(cpumask_bits(cpu_possible_mask), NR_CPUS) + 1); 1022 } 1023 1024 /* Called by boot processor to activate the rest. */ 1025 void __init smp_init(void) 1026 { 1027 int num_nodes, num_cpus; 1028 1029 idle_threads_init(); 1030 cpuhp_threads_init(); 1031 1032 pr_info("Bringing up secondary CPUs ...\n"); 1033 1034 bringup_nonboot_cpus(setup_max_cpus); 1035 1036 num_nodes = num_online_nodes(); 1037 num_cpus = num_online_cpus(); 1038 pr_info("Brought up %d node%s, %d CPU%s\n", 1039 num_nodes, str_plural(num_nodes), num_cpus, str_plural(num_cpus)); 1040 1041 /* Any cleanup work */ 1042 smp_cpus_done(setup_max_cpus); 1043 } 1044 1045 /** 1046 * on_each_cpu_cond_mask() - Call a function on each processor for which 1047 * the supplied function cond_func returns true, optionally waiting 1048 * for all the required CPUs to finish. This may include the local 1049 * processor. 1050 * @cond_func: A callback function that is passed a cpu id and 1051 * the info parameter. The function is called 1052 * with preemption disabled. The function should 1053 * return a boolean value indicating whether to IPI 1054 * the specified CPU. 1055 * @func: The function to run on all applicable CPUs. 1056 * This must be fast and non-blocking. 1057 * @info: An arbitrary pointer to pass to both functions. 1058 * @wait: If true, wait (atomically) until function has 1059 * completed on other CPUs. 1060 * @mask: The set of cpus to run on (only runs on online subset). 1061 * 1062 * Preemption is disabled to protect against CPUs going offline but not online. 1063 * CPUs going online during the call will not be seen or sent an IPI. 1064 * 1065 * You must not call this function with disabled interrupts or 1066 * from a hardware interrupt handler or from a bottom half handler. 1067 */ 1068 void on_each_cpu_cond_mask(smp_cond_func_t cond_func, smp_call_func_t func, 1069 void *info, bool wait, const struct cpumask *mask) 1070 { 1071 unsigned int scf_flags = SCF_RUN_LOCAL; 1072 1073 if (wait) 1074 scf_flags |= SCF_WAIT; 1075 1076 preempt_disable(); 1077 smp_call_function_many_cond(mask, func, info, scf_flags, cond_func); 1078 preempt_enable(); 1079 } 1080 EXPORT_SYMBOL(on_each_cpu_cond_mask); 1081 1082 static void do_nothing(void *unused) 1083 { 1084 } 1085 1086 /** 1087 * kick_all_cpus_sync - Force all cpus out of idle 1088 * 1089 * Used to synchronize the update of pm_idle function pointer. It's 1090 * called after the pointer is updated and returns after the dummy 1091 * callback function has been executed on all cpus. The execution of 1092 * the function can only happen on the remote cpus after they have 1093 * left the idle function which had been called via pm_idle function 1094 * pointer. So it's guaranteed that nothing uses the previous pointer 1095 * anymore. 1096 */ 1097 void kick_all_cpus_sync(void) 1098 { 1099 /* Make sure the change is visible before we kick the cpus */ 1100 smp_mb(); 1101 smp_call_function(do_nothing, NULL, 1); 1102 } 1103 EXPORT_SYMBOL_GPL(kick_all_cpus_sync); 1104 1105 /** 1106 * wake_up_all_idle_cpus - break all cpus out of idle 1107 * wake_up_all_idle_cpus try to break all cpus which is in idle state even 1108 * including idle polling cpus, for non-idle cpus, we will do nothing 1109 * for them. 1110 */ 1111 void wake_up_all_idle_cpus(void) 1112 { 1113 int cpu; 1114 1115 for_each_possible_cpu(cpu) { 1116 preempt_disable(); 1117 if (cpu != smp_processor_id() && cpu_online(cpu)) 1118 wake_up_if_idle(cpu); 1119 preempt_enable(); 1120 } 1121 } 1122 EXPORT_SYMBOL_GPL(wake_up_all_idle_cpus); 1123 1124 /** 1125 * cpus_peek_for_pending_ipi - Check for pending IPI for CPUs 1126 * @mask: The CPU mask for the CPUs to check. 1127 * 1128 * This function walks through the @mask to check if there are any pending IPIs 1129 * scheduled, for any of the CPUs in the @mask. It does not guarantee 1130 * correctness as it only provides a racy snapshot. 1131 * 1132 * Returns: true if there is a pending IPI scheduled and false otherwise. 1133 */ 1134 bool cpus_peek_for_pending_ipi(const struct cpumask *mask) 1135 { 1136 unsigned int cpu; 1137 1138 for_each_cpu(cpu, mask) { 1139 if (!llist_empty(per_cpu_ptr(&call_single_queue, cpu))) 1140 return true; 1141 } 1142 1143 return false; 1144 } 1145 1146 /** 1147 * struct smp_call_on_cpu_struct - Call a function on a specific CPU 1148 * @work: &work_struct 1149 * @done: &completion to signal 1150 * @func: function to call 1151 * @data: function's data argument 1152 * @ret: return value from @func 1153 * @cpu: target CPU (%-1 for any CPU) 1154 * 1155 * Used to call a function on a specific cpu and wait for it to return. 1156 * Optionally make sure the call is done on a specified physical cpu via vcpu 1157 * pinning in order to support virtualized environments. 1158 */ 1159 struct smp_call_on_cpu_struct { 1160 struct work_struct work; 1161 struct completion done; 1162 int (*func)(void *); 1163 void *data; 1164 int ret; 1165 int cpu; 1166 }; 1167 1168 static void smp_call_on_cpu_callback(struct work_struct *work) 1169 { 1170 struct smp_call_on_cpu_struct *sscs; 1171 1172 sscs = container_of(work, struct smp_call_on_cpu_struct, work); 1173 if (sscs->cpu >= 0) 1174 hypervisor_pin_vcpu(sscs->cpu); 1175 sscs->ret = sscs->func(sscs->data); 1176 if (sscs->cpu >= 0) 1177 hypervisor_pin_vcpu(-1); 1178 1179 complete(&sscs->done); 1180 } 1181 1182 /** 1183 * smp_call_on_cpu() - Call a function on a specific CPU and wait 1184 * for it to return. 1185 * @cpu: The CPU to run on. 1186 * @func: The function to run 1187 * @par: An arbitrary pointer parameter for @func. 1188 * @phys: If @true, force to run on physical @cpu. See 1189 * &struct smp_call_on_cpu_struct for more info. 1190 * 1191 * Returns: %-ENXIO if the @cpu is invalid; otherwise the return value 1192 * from @func. 1193 */ 1194 int smp_call_on_cpu(unsigned int cpu, int (*func)(void *), void *par, bool phys) 1195 { 1196 struct smp_call_on_cpu_struct sscs = { 1197 .done = COMPLETION_INITIALIZER_ONSTACK(sscs.done), 1198 .func = func, 1199 .data = par, 1200 .cpu = phys ? cpu : -1, 1201 }; 1202 1203 INIT_WORK_ONSTACK(&sscs.work, smp_call_on_cpu_callback); 1204 1205 if (cpu >= nr_cpu_ids || !cpu_online(cpu)) 1206 return -ENXIO; 1207 1208 queue_work_on(cpu, system_percpu_wq, &sscs.work); 1209 wait_for_completion(&sscs.done); 1210 destroy_work_on_stack(&sscs.work); 1211 1212 return sscs.ret; 1213 } 1214 EXPORT_SYMBOL_GPL(smp_call_on_cpu); 1215