arch/arm/kernel/smp.c

   1 /*
   2  *  linux/arch/arm/kernel/smp.c
   3  *
   4  *  Copyright (C) 2002 ARM Limited, All Rights Reserved.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10 #include <linux/module.h>
  11 #include <linux/delay.h>
  12 #include <linux/init.h>
  13 #include <linux/spinlock.h>
  14 #include <linux/sched/mm.h>
  15 #include <linux/sched/hotplug.h>
  16 #include <linux/sched/task_stack.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/cache.h>
  19 #include <linux/profile.h>
  20 #include <linux/errno.h>
  21 #include <linux/mm.h>
  22 #include <linux/err.h>
  23 #include <linux/cpu.h>
  24 #include <linux/seq_file.h>
  25 #include <linux/irq.h>
  26 #include <linux/nmi.h>
  27 #include <linux/percpu.h>
  28 #include <linux/clockchips.h>
  29 #include <linux/completion.h>
  30 #include <linux/cpufreq.h>
  31 #include <linux/irq_work.h>
  32
  33 #include <linux/atomic.h>
  34 #include <asm/bugs.h>
  35 #include <asm/smp.h>
  36 #include <asm/cacheflush.h>
  37 #include <asm/cpu.h>
  38 #include <asm/cputype.h>
  39 #include <asm/exception.h>
  40 #include <asm/idmap.h>
  41 #include <asm/topology.h>
  42 #include <asm/mmu_context.h>
  43 #include <asm/pgtable.h>
  44 #include <asm/pgalloc.h>
  45 #include <asm/procinfo.h>
  46 #include <asm/processor.h>
  47 #include <asm/sections.h>
  48 #include <asm/tlbflush.h>
  49 #include <asm/ptrace.h>
  50 #include <asm/smp_plat.h>
  51 #include <asm/virt.h>
  52 #include <asm/mach/arch.h>
  53 #include <asm/mpu.h>
  54
  55 #define CREATE_TRACE_POINTS
  56 #include <trace/events/ipi.h>
  57
  58 /*
  59  * as from 2.5, kernels no longer have an init_tasks structure
  60  * so we need some other way of telling a new secondary core
  61  * where to place its SVC stack
  62  */
  63 struct secondary_data secondary_data;
  64
  65 /*
  66  * control for which core is the next to come out of the secondary
  67  * boot "holding pen"
  68  */
  69 volatile int pen_release = -1;
  70
  71 enum ipi_msg_type {
  72         IPI_WAKEUP,
  73         IPI_TIMER,
  74         IPI_RESCHEDULE,
  75         IPI_CALL_FUNC,
  76         IPI_CPU_STOP,
  77         IPI_IRQ_WORK,
  78         IPI_COMPLETION,
  79         IPI_CPU_BACKTRACE,
  80         /*
  81          * SGI8-15 can be reserved by secure firmware, and thus may
  82          * not be usable by the kernel. Please keep the above limited
  83          * to at most 8 entries.
  84          */
  85 };
  86
  87 static DECLARE_COMPLETION(cpu_running);
  88
  89 static struct smp_operations smp_ops __ro_after_init;
  90
  91 void __init smp_set_ops(const struct smp_operations *ops)
  92 {
  93         if (ops)
  94                 smp_ops = *ops;
  95 };
  96
  97 static unsigned long get_arch_pgd(pgd_t *pgd)
  98 {
  99 #ifdef CONFIG_ARM_LPAE
 100         return __phys_to_pfn(virt_to_phys(pgd));
 101 #else
 102         return virt_to_phys(pgd);
 103 #endif
 104 }
 105
 106 #if defined(CONFIG_BIG_LITTLE) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
 107 static int secondary_biglittle_prepare(unsigned int cpu)
 108 {
 109         if (!cpu_vtable[cpu])
 110                 cpu_vtable[cpu] = kzalloc(sizeof(*cpu_vtable[cpu]), GFP_KERNEL);
 111
 112         return cpu_vtable[cpu] ? 0 : -ENOMEM;
 113 }
 114
 115 static void secondary_biglittle_init(void)
 116 {
 117         init_proc_vtable(lookup_processor(read_cpuid_id())->proc);
 118 }
 119 #else
 120 static int secondary_biglittle_prepare(unsigned int cpu)
 121 {
 122         return 0;
 123 }
 124
 125 static void secondary_biglittle_init(void)
 126 {
 127 }
 128 #endif
 129
 130 int __cpu_up(unsigned int cpu, struct task_struct *idle)
 131 {
 132         int ret;
 133
 134         if (!smp_ops.smp_boot_secondary)
 135                 return -ENOSYS;
 136
 137         ret = secondary_biglittle_prepare(cpu);
 138         if (ret)
 139                 return ret;
 140
 141         /*
 142          * We need to tell the secondary core where to find
 143          * its stack and the page tables.
 144          */
 145         secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;
 146 #ifdef CONFIG_ARM_MPU
 147         secondary_data.mpu_rgn_info = &mpu_rgn_info;
 148 #endif
 149
 150 #ifdef CONFIG_MMU
 151         secondary_data.pgdir = virt_to_phys(idmap_pgd);
 152         secondary_data.swapper_pg_dir = get_arch_pgd(swapper_pg_dir);
 153 #endif
 154         sync_cache_w(&secondary_data);
 155
 156         /*
 157          * Now bring the CPU into our world.
 158          */
 159         ret = smp_ops.smp_boot_secondary(cpu, idle);
 160         if (ret == 0) {
 161                 /*
 162                  * CPU was successfully started, wait for it
 163                  * to come online or time out.
 164                  */
 165                 wait_for_completion_timeout(&cpu_running,
 166                                                  msecs_to_jiffies(1000));
 167
 168                 if (!cpu_online(cpu)) {
 169                         pr_crit("CPU%u: failed to come online\n", cpu);
 170                         ret = -EIO;
 171                 }
 172         } else {
 173                 pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
 174         }
 175
 176
 177         memset(&secondary_data, 0, sizeof(secondary_data));
 178         return ret;
 179 }
 180
 181 /* platform specific SMP operations */
 182 void __init smp_init_cpus(void)
 183 {
 184         if (smp_ops.smp_init_cpus)
 185                 smp_ops.smp_init_cpus();
 186 }
 187
 188 int platform_can_secondary_boot(void)
 189 {
 190         return !!smp_ops.smp_boot_secondary;
 191 }
 192
 193 int platform_can_cpu_hotplug(void)
 194 {
 195 #ifdef CONFIG_HOTPLUG_CPU
 196         if (smp_ops.cpu_kill)
 197                 return 1;
 198 #endif
 199
 200         return 0;
 201 }
 202
 203 #ifdef CONFIG_HOTPLUG_CPU
 204 static int platform_cpu_kill(unsigned int cpu)
 205 {
 206         if (smp_ops.cpu_kill)
 207                 return smp_ops.cpu_kill(cpu);
 208         return 1;
 209 }
 210
 211 static int platform_cpu_disable(unsigned int cpu)
 212 {
 213         if (smp_ops.cpu_disable)
 214                 return smp_ops.cpu_disable(cpu);
 215
 216         return 0;
 217 }
 218
 219 int platform_can_hotplug_cpu(unsigned int cpu)
 220 {
 221         /* cpu_die must be specified to support hotplug */
 222         if (!smp_ops.cpu_die)
 223                 return 0;
 224
 225         if (smp_ops.cpu_can_disable)
 226                 return smp_ops.cpu_can_disable(cpu);
 227
 228         /*
 229          * By default, allow disabling all CPUs except the first one,
 230          * since this is special on a lot of platforms, e.g. because
 231          * of clock tick interrupts.
 232          */
 233         return cpu != 0;
 234 }
 235
 236 /*
 237  * __cpu_disable runs on the processor to be shutdown.
 238  */
 239 int __cpu_disable(void)
 240 {
 241         unsigned int cpu = smp_processor_id();
 242         int ret;
 243
 244         ret = platform_cpu_disable(cpu);
 245         if (ret)
 246                 return ret;
 247
 248         /*
 249          * Take this CPU offline.  Once we clear this, we can't return,
 250          * and we must not schedule until we're ready to give up the cpu.
 251          */
 252         set_cpu_online(cpu, false);
 253
 254         /*
 255          * OK - migrate IRQs away from this CPU
 256          */
 257         migrate_irqs();
 258
 259         /*
 260          * Flush user cache and TLB mappings, and then remove this CPU
 261          * from the vm mask set of all processes.
 262          *
 263          * Caches are flushed to the Level of Unification Inner Shareable
 264          * to write-back dirty lines to unified caches shared by all CPUs.
 265          */
 266         flush_cache_louis();
 267         local_flush_tlb_all();
 268
 269         return 0;
 270 }
 271
 272 static DECLARE_COMPLETION(cpu_died);
 273
 274 /*
 275  * called on the thread which is asking for a CPU to be shutdown -
 276  * waits until shutdown has completed, or it is timed out.
 277  */
 278 void __cpu_die(unsigned int cpu)
 279 {
 280         if (!wait_for_completion_timeout(&cpu_died, msecs_to_jiffies(5000))) {
 281                 pr_err("CPU%u: cpu didn't die\n", cpu);
 282                 return;
 283         }
 284         pr_debug("CPU%u: shutdown\n", cpu);
 285
 286         clear_tasks_mm_cpumask(cpu);
 287         /*
 288          * platform_cpu_kill() is generally expected to do the powering off
 289          * and/or cutting of clocks to the dying CPU.  Optionally, this may
 290          * be done by the CPU which is dying in preference to supporting
 291          * this call, but that means there is _no_ synchronisation between
 292          * the requesting CPU and the dying CPU actually losing power.
 293          */
 294         if (!platform_cpu_kill(cpu))
 295                 pr_err("CPU%u: unable to kill\n", cpu);
 296 }
 297
 298 /*
 299  * Called from the idle thread for the CPU which has been shutdown.
 300  *
 301  * Note that we disable IRQs here, but do not re-enable them
 302  * before returning to the caller. This is also the behaviour
 303  * of the other hotplug-cpu capable cores, so presumably coming
 304  * out of idle fixes this.
 305  */
 306 void arch_cpu_idle_dead(void)
 307 {
 308         unsigned int cpu = smp_processor_id();
 309
 310         idle_task_exit();
 311
 312         local_irq_disable();
 313
 314         /*
 315          * Flush the data out of the L1 cache for this CPU.  This must be
 316          * before the completion to ensure that data is safely written out
 317          * before platform_cpu_kill() gets called - which may disable
 318          * *this* CPU and power down its cache.
 319          */
 320         flush_cache_louis();
 321
 322         /*
 323          * Tell __cpu_die() that this CPU is now safe to dispose of.  Once
 324          * this returns, power and/or clocks can be removed at any point
 325          * from this CPU and its cache by platform_cpu_kill().
 326          */
 327         complete(&cpu_died);
 328
 329         /*
 330          * Ensure that the cache lines associated with that completion are
 331          * written out.  This covers the case where _this_ CPU is doing the
 332          * powering down, to ensure that the completion is visible to the
 333          * CPU waiting for this one.
 334          */
 335         flush_cache_louis();
 336
 337         /*
 338          * The actual CPU shutdown procedure is at least platform (if not
 339          * CPU) specific.  This may remove power, or it may simply spin.
 340          *
 341          * Platforms are generally expected *NOT* to return from this call,
 342          * although there are some which do because they have no way to
 343          * power down the CPU.  These platforms are the _only_ reason we
 344          * have a return path which uses the fragment of assembly below.
 345          *
 346          * The return path should not be used for platforms which can
 347          * power off the CPU.
 348          */
 349         if (smp_ops.cpu_die)
 350                 smp_ops.cpu_die(cpu);
 351
 352         pr_warn("CPU%u: smp_ops.cpu_die() returned, trying to resuscitate\n",
 353                 cpu);
 354
 355         /*
 356          * Do not return to the idle loop - jump back to the secondary
 357          * cpu initialisation.  There's some initialisation which needs
 358          * to be repeated to undo the effects of taking the CPU offline.
 359          */
 360         __asm__("mov    sp, %0\n"
 361         "       mov     fp, #0\n"
 362         "       b       secondary_start_kernel"
 363                 :
 364                 : "r" (task_stack_page(current) + THREAD_SIZE - 8));
 365 }
 366 #endif /* CONFIG_HOTPLUG_CPU */
 367
 368 /*
 369  * Called by both boot and secondaries to move global data into
 370  * per-processor storage.
 371  */
 372 static void smp_store_cpu_info(unsigned int cpuid)
 373 {
 374         struct cpuinfo_arm *cpu_info = &per_cpu(cpu_data, cpuid);
 375
 376         cpu_info->loops_per_jiffy = loops_per_jiffy;
 377         cpu_info->cpuid = read_cpuid_id();
 378
 379         store_cpu_topology(cpuid);
 380 }
 381
 382 /*
 383  * This is the secondary CPU boot entry.  We're using this CPUs
 384  * idle thread stack, but a set of temporary page tables.
 385  */
 386 asmlinkage void secondary_start_kernel(void)
 387 {
 388         struct mm_struct *mm = &init_mm;
 389         unsigned int cpu;
 390
 391         secondary_biglittle_init();
 392
 393         /*
 394          * The identity mapping is uncached (strongly ordered), so
 395          * switch away from it before attempting any exclusive accesses.
 396          */
 397         cpu_switch_mm(mm->pgd, mm);
 398         local_flush_bp_all();
 399         enter_lazy_tlb(mm, current);
 400         local_flush_tlb_all();
 401
 402         /*
 403          * All kernel threads share the same mm context; grab a
 404          * reference and switch to it.
 405          */
 406         cpu = smp_processor_id();
 407         mmgrab(mm);
 408         current->active_mm = mm;
 409         cpumask_set_cpu(cpu, mm_cpumask(mm));
 410
 411         cpu_init();
 412
 413 #ifndef CONFIG_MMU
 414         setup_vectors_base();
 415 #endif
 416         pr_debug("CPU%u: Booted secondary processor\n", cpu);
 417
 418         preempt_disable();
 419         trace_hardirqs_off();
 420
 421         /*
 422          * Give the platform a chance to do its own initialisation.
 423          */
 424         if (smp_ops.smp_secondary_init)
 425                 smp_ops.smp_secondary_init(cpu);
 426
 427         notify_cpu_starting(cpu);
 428
 429         calibrate_delay();
 430
 431         smp_store_cpu_info(cpu);
 432
 433         /*
 434          * OK, now it's safe to let the boot CPU continue.  Wait for
 435          * the CPU migration code to notice that the CPU is online
 436          * before we continue - which happens after __cpu_up returns.
 437          */
 438         set_cpu_online(cpu, true);
 439
 440         check_other_bugs();
 441
 442         complete(&cpu_running);
 443
 444         local_irq_enable();
 445         local_fiq_enable();
 446         local_abt_enable();
 447
 448         /*
 449          * OK, it's off to the idle thread for us
 450          */
 451         cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 452 }
 453
 454 void __init smp_cpus_done(unsigned int max_cpus)
 455 {
 456         int cpu;
 457         unsigned long bogosum = 0;
 458
 459         for_each_online_cpu(cpu)
 460                 bogosum += per_cpu(cpu_data, cpu).loops_per_jiffy;
 461
 462         printk(KERN_INFO "SMP: Total of %d processors activated "
 463                "(%lu.%02lu BogoMIPS).\n",
 464                num_online_cpus(),
 465                bogosum / (500000/HZ),
 466                (bogosum / (5000/HZ)) % 100);
 467
 468         hyp_mode_check();
 469 }
 470
 471 void __init smp_prepare_boot_cpu(void)
 472 {
 473         set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
 474 }
 475
 476 void __init smp_prepare_cpus(unsigned int max_cpus)
 477 {
 478         unsigned int ncores = num_possible_cpus();
 479
 480         init_cpu_topology();
 481
 482         smp_store_cpu_info(smp_processor_id());
 483
 484         /*
 485          * are we trying to boot more cores than exist?
 486          */
 487         if (max_cpus > ncores)
 488                 max_cpus = ncores;
 489         if (ncores > 1 && max_cpus) {
 490                 /*
 491                  * Initialise the present map, which describes the set of CPUs
 492                  * actually populated at the present time. A platform should
 493                  * re-initialize the map in the platforms smp_prepare_cpus()
 494                  * if present != possible (e.g. physical hotplug).
 495                  */
 496                 init_cpu_present(cpu_possible_mask);
 497
 498                 /*
 499                  * Initialise the SCU if there are more than one CPU
 500                  * and let them know where to start.
 501                  */
 502                 if (smp_ops.smp_prepare_cpus)
 503                         smp_ops.smp_prepare_cpus(max_cpus);
 504         }
 505 }
 506
 507 static void (*__smp_cross_call)(const struct cpumask *, unsigned int);
 508
 509 void __init set_smp_cross_call(void (*fn)(const struct cpumask *, unsigned int))
 510 {
 511         if (!__smp_cross_call)
 512                 __smp_cross_call = fn;
 513 }
 514
 515 static const char *ipi_types[NR_IPI] __tracepoint_string = {
 516 #define S(x,s)  [x] = s
 517         S(IPI_WAKEUP, "CPU wakeup interrupts"),
 518         S(IPI_TIMER, "Timer broadcast interrupts"),
 519         S(IPI_RESCHEDULE, "Rescheduling interrupts"),
 520         S(IPI_CALL_FUNC, "Function call interrupts"),
 521         S(IPI_CPU_STOP, "CPU stop interrupts"),
 522         S(IPI_IRQ_WORK, "IRQ work interrupts"),
 523         S(IPI_COMPLETION, "completion interrupts"),
 524 };
 525
 526 static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
 527 {
 528         trace_ipi_raise_rcuidle(target, ipi_types[ipinr]);
 529         __smp_cross_call(target, ipinr);
 530 }
 531
 532 void show_ipi_list(struct seq_file *p, int prec)
 533 {
 534         unsigned int cpu, i;
 535
 536         for (i = 0; i < NR_IPI; i++) {
 537                 seq_printf(p, "%*s%u: ", prec - 1, "IPI", i);
 538
 539                 for_each_online_cpu(cpu)
 540                         seq_printf(p, "%10u ",
 541                                    __get_irq_stat(cpu, ipi_irqs[i]));
 542
 543                 seq_printf(p, " %s\n", ipi_types[i]);
 544         }
 545 }
 546
 547 u64 smp_irq_stat_cpu(unsigned int cpu)
 548 {
 549         u64 sum = 0;
 550         int i;
 551
 552         for (i = 0; i < NR_IPI; i++)
 553                 sum += __get_irq_stat(cpu, ipi_irqs[i]);
 554
 555         return sum;
 556 }
 557
 558 void arch_send_call_function_ipi_mask(const struct cpumask *mask)
 559 {
 560         smp_cross_call(mask, IPI_CALL_FUNC);
 561 }
 562
 563 void arch_send_wakeup_ipi_mask(const struct cpumask *mask)
 564 {
 565         smp_cross_call(mask, IPI_WAKEUP);
 566 }
 567
 568 void arch_send_call_function_single_ipi(int cpu)
 569 {
 570         smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC);
 571 }
 572
 573 #ifdef CONFIG_IRQ_WORK
 574 void arch_irq_work_raise(void)
 575 {
 576         if (arch_irq_work_has_interrupt())
 577                 smp_cross_call(cpumask_of(smp_processor_id()), IPI_IRQ_WORK);
 578 }
 579 #endif
 580
 581 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 582 void tick_broadcast(const struct cpumask *mask)
 583 {
 584         smp_cross_call(mask, IPI_TIMER);
 585 }
 586 #endif
 587
 588 static DEFINE_RAW_SPINLOCK(stop_lock);
 589
 590 /*
 591  * ipi_cpu_stop - handle IPI from smp_send_stop()
 592  */
 593 static void ipi_cpu_stop(unsigned int cpu)
 594 {
 595         if (system_state <= SYSTEM_RUNNING) {
 596                 raw_spin_lock(&stop_lock);
 597                 pr_crit("CPU%u: stopping\n", cpu);
 598                 dump_stack();
 599                 raw_spin_unlock(&stop_lock);
 600         }
 601
 602         set_cpu_online(cpu, false);
 603
 604         local_fiq_disable();
 605         local_irq_disable();
 606
 607         while (1)
 608                 cpu_relax();
 609 }
 610
 611 static DEFINE_PER_CPU(struct completion *, cpu_completion);
 612
 613 int register_ipi_completion(struct completion *completion, int cpu)
 614 {
 615         per_cpu(cpu_completion, cpu) = completion;
 616         return IPI_COMPLETION;
 617 }
 618
 619 static void ipi_complete(unsigned int cpu)
 620 {
 621         complete(per_cpu(cpu_completion, cpu));
 622 }
 623
 624 /*
 625  * Main handler for inter-processor interrupts
 626  */
 627 asmlinkage void __exception_irq_entry do_IPI(int ipinr, struct pt_regs *regs)
 628 {
 629         handle_IPI(ipinr, regs);
 630 }
 631
 632 void handle_IPI(int ipinr, struct pt_regs *regs)
 633 {
 634         unsigned int cpu = smp_processor_id();
 635         struct pt_regs *old_regs = set_irq_regs(regs);
 636
 637         if ((unsigned)ipinr < NR_IPI) {
 638                 trace_ipi_entry_rcuidle(ipi_types[ipinr]);
 639                 __inc_irq_stat(cpu, ipi_irqs[ipinr]);
 640         }
 641
 642         switch (ipinr) {
 643         case IPI_WAKEUP:
 644                 break;
 645
 646 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 647         case IPI_TIMER:
 648                 irq_enter();
 649                 tick_receive_broadcast();
 650                 irq_exit();
 651                 break;
 652 #endif
 653
 654         case IPI_RESCHEDULE:
 655                 scheduler_ipi();
 656                 break;
 657
 658         case IPI_CALL_FUNC:
 659                 irq_enter();
 660                 generic_smp_call_function_interrupt();
 661                 irq_exit();
 662                 break;
 663
 664         case IPI_CPU_STOP:
 665                 irq_enter();
 666                 ipi_cpu_stop(cpu);
 667                 irq_exit();
 668                 break;
 669
 670 #ifdef CONFIG_IRQ_WORK
 671         case IPI_IRQ_WORK:
 672                 irq_enter();
 673                 irq_work_run();
 674                 irq_exit();
 675                 break;
 676 #endif
 677
 678         case IPI_COMPLETION:
 679                 irq_enter();
 680                 ipi_complete(cpu);
 681                 irq_exit();
 682                 break;
 683
 684         case IPI_CPU_BACKTRACE:
 685                 printk_nmi_enter();
 686                 irq_enter();
 687                 nmi_cpu_backtrace(regs);
 688                 irq_exit();
 689                 printk_nmi_exit();
 690                 break;
 691
 692         default:
 693                 pr_crit("CPU%u: Unknown IPI message 0x%x\n",
 694                         cpu, ipinr);
 695                 break;
 696         }
 697
 698         if ((unsigned)ipinr < NR_IPI)
 699                 trace_ipi_exit_rcuidle(ipi_types[ipinr]);
 700         set_irq_regs(old_regs);
 701 }
 702
 703 void smp_send_reschedule(int cpu)
 704 {
 705         smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
 706 }
 707
 708 void smp_send_stop(void)
 709 {
 710         unsigned long timeout;
 711         struct cpumask mask;
 712
 713         cpumask_copy(&mask, cpu_online_mask);
 714         cpumask_clear_cpu(smp_processor_id(), &mask);
 715         if (!cpumask_empty(&mask))
 716                 smp_cross_call(&mask, IPI_CPU_STOP);
 717
 718         /* Wait up to one second for other CPUs to stop */
 719         timeout = USEC_PER_SEC;
 720         while (num_online_cpus() > 1 && timeout--)
 721                 udelay(1);
 722
 723         if (num_online_cpus() > 1)
 724                 pr_warn("SMP: failed to stop secondary CPUs\n");
 725 }
 726
 727 /*
 728  * not supported here
 729  */
 730 int setup_profiling_timer(unsigned int multiplier)
 731 {
 732         return -EINVAL;
 733 }
 734
 735 #ifdef CONFIG_CPU_FREQ
 736
 737 static DEFINE_PER_CPU(unsigned long, l_p_j_ref);
 738 static DEFINE_PER_CPU(unsigned long, l_p_j_ref_freq);
 739 static unsigned long global_l_p_j_ref;
 740 static unsigned long global_l_p_j_ref_freq;
 741
 742 static int cpufreq_callback(struct notifier_block *nb,
 743                                         unsigned long val, void *data)
 744 {
 745         struct cpufreq_freqs *freq = data;
 746         int cpu = freq->cpu;
 747
 748         if (freq->flags & CPUFREQ_CONST_LOOPS)
 749                 return NOTIFY_OK;
 750
 751         if (!per_cpu(l_p_j_ref, cpu)) {
 752                 per_cpu(l_p_j_ref, cpu) =
 753                         per_cpu(cpu_data, cpu).loops_per_jiffy;
 754                 per_cpu(l_p_j_ref_freq, cpu) = freq->old;
 755                 if (!global_l_p_j_ref) {
 756                         global_l_p_j_ref = loops_per_jiffy;
 757                         global_l_p_j_ref_freq = freq->old;
 758                 }
 759         }
 760
 761         if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
 762             (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
 763                 loops_per_jiffy = cpufreq_scale(global_l_p_j_ref,
 764                                                 global_l_p_j_ref_freq,
 765                                                 freq->new);
 766                 per_cpu(cpu_data, cpu).loops_per_jiffy =
 767                         cpufreq_scale(per_cpu(l_p_j_ref, cpu),
 768                                         per_cpu(l_p_j_ref_freq, cpu),
 769                                         freq->new);
 770         }
 771         return NOTIFY_OK;
 772 }
 773
 774 static struct notifier_block cpufreq_notifier = {
 775         .notifier_call  = cpufreq_callback,
 776 };
 777
 778 static int __init register_cpufreq_notifier(void)
 779 {
 780         return cpufreq_register_notifier(&cpufreq_notifier,
 781                                                 CPUFREQ_TRANSITION_NOTIFIER);
 782 }
 783 core_initcall(register_cpufreq_notifier);
 784
 785 #endif
 786
 787 static void raise_nmi(cpumask_t *mask)
 788 {
 789         smp_cross_call(mask, IPI_CPU_BACKTRACE);
 790 }
 791
 792 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 793 {
 794         nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_nmi);
 795 }