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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/arch/arm/kernel/smp.c
  *
  *  Copyright (C) 2002 ARM Limited, All Rights Reserved.
  */
 #include <linux/module.h>
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/spinlock.h>
 #include <linux/sched/mm.h>
 #include <linux/sched/hotplug.h>
 #include <linux/sched/task_stack.h>
 #include <linux/interrupt.h>
 #include <linux/cache.h>
 #include <linux/profile.h>
 #include <linux/errno.h>
 #include <linux/mm.h>
 #include <linux/err.h>
 #include <linux/cpu.h>
 #include <linux/seq_file.h>
 #include <linux/irq.h>
 #include <linux/nmi.h>
 #include <linux/percpu.h>
 #include <linux/clockchips.h>
 #include <linux/completion.h>
 #include <linux/cpufreq.h>
 #include <linux/irq_work.h>
 #include <linux/kernel_stat.h>
 
 #include <linux/atomic.h>
 #include <asm/bugs.h>
 #include <asm/smp.h>
 #include <asm/cacheflush.h>
 #include <asm/cpu.h>
 #include <asm/cputype.h>
 #include <asm/exception.h>
 #include <asm/idmap.h>
 #include <asm/topology.h>
 #include <asm/mmu_context.h>
 #include <asm/procinfo.h>
 #include <asm/processor.h>
 #include <asm/sections.h>
 #include <asm/tlbflush.h>
 #include <asm/ptrace.h>
 #include <asm/smp_plat.h>
 #include <asm/virt.h>
 #include <asm/mach/arch.h>
 #include <asm/mpu.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/ipi.h>
 
 /*
  * as from 2.5, kernels no longer have an init_tasks structure
  * so we need some other way of telling a new secondary core
  * where to place its SVC stack
  */
 struct secondary_data secondary_data;
 
 enum ipi_msg_type {
     IPI_WAKEUP,
     IPI_TIMER,
     IPI_RESCHEDULE,
     IPI_CALL_FUNC,
     IPI_CPU_STOP,
     IPI_IRQ_WORK,
     IPI_COMPLETION,
     NR_IPI,
     /*
      * CPU_BACKTRACE is special and not included in NR_IPI
      * or tracable with trace_ipi_*
      */
     IPI_CPU_BACKTRACE = NR_IPI,
     /*
      * SGI8-15 can be reserved by secure firmware, and thus may
      * not be usable by the kernel. Please keep the above limited
      * to at most 8 entries.
      */
     MAX_IPI
 };
 
 static int ipi_irq_base __read_mostly;
 static int nr_ipi __read_mostly = NR_IPI;
 static struct irq_desc *ipi_desc[MAX_IPI] __read_mostly;
 
 static void ipi_setup(int cpu);
 
 static DECLARE_COMPLETION(cpu_running);
 
 static struct smp_operations smp_ops __ro_after_init;
 
 void __init smp_set_ops(const struct smp_operations *ops)
 {
     if (ops)
         smp_ops = *ops;
 };
 
 static unsigned long get_arch_pgd(pgd_t *pgd)
 {
 #ifdef CONFIG_ARM_LPAE
     return __phys_to_pfn(virt_to_phys(pgd));
 #else
     return virt_to_phys(pgd);
 #endif
 }
 
 #if defined(CONFIG_BIG_LITTLE) && defined(CONFIG_HARDEN_BRANCH_PREDICTOR)
 static int secondary_biglittle_prepare(unsigned int cpu)
 {
     if (!cpu_vtable[cpu])
         cpu_vtable[cpu] = kzalloc(sizeof(*cpu_vtable[cpu]), GFP_KERNEL);
 
     return cpu_vtable[cpu] ? 0 : -ENOMEM;
 }
 
 static void secondary_biglittle_init(void)
 {
     init_proc_vtable(lookup_processor(read_cpuid_id())->proc);
 }
 #else
 static int secondary_biglittle_prepare(unsigned int cpu)
 {
     return 0;
 }
 
 static void secondary_biglittle_init(void)
 {
 }
 #endif
 
 int __cpu_up(unsigned int cpu, struct task_struct *idle)
 {
     int ret;
 
     if (!smp_ops.smp_boot_secondary)
         return -ENOSYS;
 
     ret = secondary_biglittle_prepare(cpu);
     if (ret)
         return ret;
 
     /*
      * We need to tell the secondary core where to find
      * its stack and the page tables.
      */
     secondary_data.stack = task_stack_page(idle) + THREAD_START_SP;
 #ifdef CONFIG_ARM_MPU
     secondary_data.mpu_rgn_info = &mpu_rgn_info;
 #endif
 
 #ifdef CONFIG_MMU
     secondary_data.pgdir = virt_to_phys(idmap_pgd);
     secondary_data.swapper_pg_dir = get_arch_pgd(swapper_pg_dir);
 #endif
     secondary_data.task = idle;
     sync_cache_w(&secondary_data);
 
     /*
      * Now bring the CPU into our world.
      */
     ret = smp_ops.smp_boot_secondary(cpu, idle);
     if (ret == 0) {
         /*
          * CPU was successfully started, wait for it
          * to come online or time out.
          */
         wait_for_completion_timeout(&cpu_running,
                          msecs_to_jiffies(1000));
 
         if (!cpu_online(cpu)) {
             pr_crit("CPU%u: failed to come online\n", cpu);
             ret = -EIO;
         }
     } else {
         pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
     }
 
 
     memset(&secondary_data, 0, sizeof(secondary_data));
     return ret;
 }
 
 /* platform specific SMP operations */
 void __init smp_init_cpus(void)
 {
     if (smp_ops.smp_init_cpus)
         smp_ops.smp_init_cpus();
 }
 
 int platform_can_secondary_boot(void)
 {
     return !!smp_ops.smp_boot_secondary;
 }
 
 int platform_can_cpu_hotplug(void)
 {
 #ifdef CONFIG_HOTPLUG_CPU
     if (smp_ops.cpu_kill)
         return 1;
 #endif
 
     return 0;
 }
 
 #ifdef CONFIG_HOTPLUG_CPU
 static int platform_cpu_kill(unsigned int cpu)
 {
     if (smp_ops.cpu_kill)
         return smp_ops.cpu_kill(cpu);
     return 1;
 }
 
 static int platform_cpu_disable(unsigned int cpu)
 {
     if (smp_ops.cpu_disable)
         return smp_ops.cpu_disable(cpu);
 
     return 0;
 }
 
 int platform_can_hotplug_cpu(unsigned int cpu)
 {
     /* cpu_die must be specified to support hotplug */
     if (!smp_ops.cpu_die)
         return 0;
 
     if (smp_ops.cpu_can_disable)
         return smp_ops.cpu_can_disable(cpu);
 
     /*
      * By default, allow disabling all CPUs except the first one,
      * since this is special on a lot of platforms, e.g. because
      * of clock tick interrupts.
      */
     return cpu != 0;
 }
 
 static void ipi_teardown(int cpu)
 {
     int i;
 
     if (WARN_ON_ONCE(!ipi_irq_base))
         return;
 
     for (i = 0; i < nr_ipi; i++)
         disable_percpu_irq(ipi_irq_base + i);
 }
 
 /*
  * __cpu_disable runs on the processor to be shutdown.
  */
 int __cpu_disable(void)
 {
     unsigned int cpu = smp_processor_id();
     int ret;
 
     ret = platform_cpu_disable(cpu);
     if (ret)
         return ret;
 
 #ifdef CONFIG_GENERIC_ARCH_TOPOLOGY
     remove_cpu_topology(cpu);
 #endif
 
     /*
      * Take this CPU offline.  Once we clear this, we can't return,
      * and we must not schedule until we're ready to give up the cpu.
      */
     set_cpu_online(cpu, false);
     ipi_teardown(cpu);
 
     /*
      * OK - migrate IRQs away from this CPU
      */
     irq_migrate_all_off_this_cpu();
 
     /*
      * Flush user cache and TLB mappings, and then remove this CPU
      * from the vm mask set of all processes.
      *
      * Caches are flushed to the Level of Unification Inner Shareable
      * to write-back dirty lines to unified caches shared by all CPUs.
      */
     flush_cache_louis();
     local_flush_tlb_all();
 
     return 0;
 }
 
 /*
  * called on the thread which is asking for a CPU to be shutdown -
  * waits until shutdown has completed, or it is timed out.
  */
 void __cpu_die(unsigned int cpu)
 {
     if (!cpu_wait_death(cpu, 5)) {
         pr_err("CPU%u: cpu didn't die\n", cpu);
         return;
     }
     pr_debug("CPU%u: shutdown\n", cpu);
 
     clear_tasks_mm_cpumask(cpu);
     /*
      * platform_cpu_kill() is generally expected to do the powering off
      * and/or cutting of clocks to the dying CPU.  Optionally, this may
      * be done by the CPU which is dying in preference to supporting
      * this call, but that means there is _no_ synchronisation between
      * the requesting CPU and the dying CPU actually losing power.
      */
     if (!platform_cpu_kill(cpu))
         pr_err("CPU%u: unable to kill\n", cpu);
 }
 
 /*
  * Called from the idle thread for the CPU which has been shutdown.
  *
  * Note that we disable IRQs here, but do not re-enable them
  * before returning to the caller. This is also the behaviour
  * of the other hotplug-cpu capable cores, so presumably coming
  * out of idle fixes this.
  */
 void arch_cpu_idle_dead(void)
 {
     unsigned int cpu = smp_processor_id();
 
     idle_task_exit();
 
     local_irq_disable();
 
     /*
      * Flush the data out of the L1 cache for this CPU.  This must be
      * before the completion to ensure that data is safely written out
      * before platform_cpu_kill() gets called - which may disable
      * *this* CPU and power down its cache.
      */
     flush_cache_louis();
 
     /*
      * Tell __cpu_die() that this CPU is now safe to dispose of.  Once
      * this returns, power and/or clocks can be removed at any point
      * from this CPU and its cache by platform_cpu_kill().
      */
     (void)cpu_report_death();
 
     /*
      * Ensure that the cache lines associated with that completion are
      * written out.  This covers the case where _this_ CPU is doing the
      * powering down, to ensure that the completion is visible to the
      * CPU waiting for this one.
      */
     flush_cache_louis();
 
     /*
      * The actual CPU shutdown procedure is at least platform (if not
      * CPU) specific.  This may remove power, or it may simply spin.
      *
      * Platforms are generally expected *NOT* to return from this call,
      * although there are some which do because they have no way to
      * power down the CPU.  These platforms are the _only_ reason we
      * have a return path which uses the fragment of assembly below.
      *
      * The return path should not be used for platforms which can
      * power off the CPU.
      */
     if (smp_ops.cpu_die)
         smp_ops.cpu_die(cpu);
 
     pr_warn("CPU%u: smp_ops.cpu_die() returned, trying to resuscitate\n",
         cpu);
 
     /*
      * Do not return to the idle loop - jump back to the secondary
      * cpu initialisation.  There's some initialisation which needs
      * to be repeated to undo the effects of taking the CPU offline.
      */
     __asm__("mov    sp, %0\n"
     "   mov fp, #0\n"
     "   mov r0, %1\n"
     "   b   secondary_start_kernel"
         :
         : "r" (task_stack_page(current) + THREAD_SIZE - 8),
           "r" (current)
         : "r0");
 }
 #endif /* CONFIG_HOTPLUG_CPU */
 
 /*
  * Called by both boot and secondaries to move global data into
  * per-processor storage.
  */
 static void smp_store_cpu_info(unsigned int cpuid)
 {
     struct cpuinfo_arm *cpu_info = &per_cpu(cpu_data, cpuid);
 
     cpu_info->loops_per_jiffy = loops_per_jiffy;
     cpu_info->cpuid = read_cpuid_id();
 
     store_cpu_topology(cpuid);
     check_cpu_icache_size(cpuid);
 }
 
 static void set_current(struct task_struct *cur)
 {
     /* Set TPIDRURO */
     asm("mcr p15, 0, %0, c13, c0, 3" :: "r"(cur) : "memory");
 }
 
 /*
  * This is the secondary CPU boot entry.  We're using this CPUs
  * idle thread stack, but a set of temporary page tables.
  */
 asmlinkage void secondary_start_kernel(struct task_struct *task)
 {
     struct mm_struct *mm = &init_mm;
     unsigned int cpu;
 
     set_current(task);
 
     secondary_biglittle_init();
 
     /*
      * The identity mapping is uncached (strongly ordered), so
      * switch away from it before attempting any exclusive accesses.
      */
     cpu_switch_mm(mm->pgd, mm);
     local_flush_bp_all();
     enter_lazy_tlb(mm, current);
     local_flush_tlb_all();
 
     /*
      * All kernel threads share the same mm context; grab a
      * reference and switch to it.
      */
     cpu = smp_processor_id();
     mmgrab(mm);
     current->active_mm = mm;
     cpumask_set_cpu(cpu, mm_cpumask(mm));
 
     cpu_init();
 
 #ifndef CONFIG_MMU
     setup_vectors_base();
 #endif
     pr_debug("CPU%u: Booted secondary processor\n", cpu);
 
     trace_hardirqs_off();
 
     /*
      * Give the platform a chance to do its own initialisation.
      */
     if (smp_ops.smp_secondary_init)
         smp_ops.smp_secondary_init(cpu);
 
     notify_cpu_starting(cpu);
 
     ipi_setup(cpu);
 
     calibrate_delay();
 
     smp_store_cpu_info(cpu);
 
     /*
      * OK, now it's safe to let the boot CPU continue.  Wait for
      * the CPU migration code to notice that the CPU is online
      * before we continue - which happens after __cpu_up returns.
      */
     set_cpu_online(cpu, true);
 
     check_other_bugs();
 
     complete(&cpu_running);
 
     local_irq_enable();
     local_fiq_enable();
     local_abt_enable();
 
     /*
      * OK, it's off to the idle thread for us
      */
     cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
 }
 
 void __init smp_cpus_done(unsigned int max_cpus)
 {
     int cpu;
     unsigned long bogosum = 0;
 
     for_each_online_cpu(cpu)
         bogosum += per_cpu(cpu_data, cpu).loops_per_jiffy;
 
     printk(KERN_INFO "SMP: Total of %d processors activated "
            "(%lu.%02lu BogoMIPS).\n",
            num_online_cpus(),
            bogosum / (500000/HZ),
            (bogosum / (5000/HZ)) % 100);
 
     hyp_mode_check();
 }
 
 void __init smp_prepare_boot_cpu(void)
 {
     set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
 }
 
 void __init smp_prepare_cpus(unsigned int max_cpus)
 {
     unsigned int ncores = num_possible_cpus();
 
     init_cpu_topology();
 
     smp_store_cpu_info(smp_processor_id());
 
     /*
      * are we trying to boot more cores than exist?
      */
     if (max_cpus > ncores)
         max_cpus = ncores;
     if (ncores > 1 && max_cpus) {
         /*
          * Initialise the present map, which describes the set of CPUs
          * actually populated at the present time. A platform should
          * re-initialize the map in the platforms smp_prepare_cpus()
          * if present != possible (e.g. physical hotplug).
          */
         init_cpu_present(cpu_possible_mask);
 
         /*
          * Initialise the SCU if there are more than one CPU
          * and let them know where to start.
          */
         if (smp_ops.smp_prepare_cpus)
             smp_ops.smp_prepare_cpus(max_cpus);
     }
 }
 
 static const char *ipi_types[NR_IPI] __tracepoint_string = {
     [IPI_WAKEUP]        = "CPU wakeup interrupts",
     [IPI_TIMER]     = "Timer broadcast interrupts",
     [IPI_RESCHEDULE]    = "Rescheduling interrupts",
     [IPI_CALL_FUNC]     = "Function call interrupts",
     [IPI_CPU_STOP]      = "CPU stop interrupts",
     [IPI_IRQ_WORK]      = "IRQ work interrupts",
     [IPI_COMPLETION]    = "completion interrupts",
 };
 
 static void smp_cross_call(const struct cpumask *target, unsigned int ipinr);
 
 void show_ipi_list(struct seq_file *p, int prec)
 {
     unsigned int cpu, i;
 
     for (i = 0; i < NR_IPI; i++) {
         if (!ipi_desc[i])
             continue;
 
         seq_printf(p, "%*s%u: ", prec - 1, "IPI", i);
 
         for_each_online_cpu(cpu)
             seq_printf(p, "%10u ", irq_desc_kstat_cpu(ipi_desc[i], cpu));
 
         seq_printf(p, " %s\n", ipi_types[i]);
     }
 }
 
 void arch_send_call_function_ipi_mask(const struct cpumask *mask)
 {
     smp_cross_call(mask, IPI_CALL_FUNC);
 }
 
 void arch_send_wakeup_ipi_mask(const struct cpumask *mask)
 {
     smp_cross_call(mask, IPI_WAKEUP);
 }
 
 void arch_send_call_function_single_ipi(int cpu)
 {
     smp_cross_call(cpumask_of(cpu), IPI_CALL_FUNC);
 }
 
 #ifdef CONFIG_IRQ_WORK
 void arch_irq_work_raise(void)
 {
     if (arch_irq_work_has_interrupt())
         smp_cross_call(cpumask_of(smp_processor_id()), IPI_IRQ_WORK);
 }
 #endif
 
 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 void tick_broadcast(const struct cpumask *mask)
 {
     smp_cross_call(mask, IPI_TIMER);
 }
 #endif
 
 static DEFINE_RAW_SPINLOCK(stop_lock);
 
 /*
  * ipi_cpu_stop - handle IPI from smp_send_stop()
  */
 static void ipi_cpu_stop(unsigned int cpu)
 {
     if (system_state <= SYSTEM_RUNNING) {
         raw_spin_lock(&stop_lock);
         pr_crit("CPU%u: stopping\n", cpu);
         dump_stack();
         raw_spin_unlock(&stop_lock);
     }
 
     set_cpu_online(cpu, false);
 
     local_fiq_disable();
     local_irq_disable();
 
     while (1) {
         cpu_relax();
         wfe();
     }
 }
 
 static DEFINE_PER_CPU(struct completion *, cpu_completion);
 
 int register_ipi_completion(struct completion *completion, int cpu)
 {
     per_cpu(cpu_completion, cpu) = completion;
     return IPI_COMPLETION;
 }
 
 static void ipi_complete(unsigned int cpu)
 {
     complete(per_cpu(cpu_completion, cpu));
 }
 
 /*
  * Main handler for inter-processor interrupts
  */
 static void do_handle_IPI(int ipinr)
 {
     unsigned int cpu = smp_processor_id();
 
     if ((unsigned)ipinr < NR_IPI)
         trace_ipi_entry_rcuidle(ipi_types[ipinr]);
 
     switch (ipinr) {
     case IPI_WAKEUP:
         break;
 
 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
     case IPI_TIMER:
         tick_receive_broadcast();
         break;
 #endif
 
     case IPI_RESCHEDULE:
         scheduler_ipi();
         break;
 
     case IPI_CALL_FUNC:
         generic_smp_call_function_interrupt();
         break;
 
     case IPI_CPU_STOP:
         ipi_cpu_stop(cpu);
         break;
 
 #ifdef CONFIG_IRQ_WORK
     case IPI_IRQ_WORK:
         irq_work_run();
         break;
 #endif
 
     case IPI_COMPLETION:
         ipi_complete(cpu);
         break;
 
     case IPI_CPU_BACKTRACE:
         printk_deferred_enter();
         nmi_cpu_backtrace(get_irq_regs());
         printk_deferred_exit();
         break;
 
     default:
         pr_crit("CPU%u: Unknown IPI message 0x%x\n",
                 cpu, ipinr);
         break;
     }
 
     if ((unsigned)ipinr < NR_IPI)
         trace_ipi_exit_rcuidle(ipi_types[ipinr]);
 }
 
 /* Legacy version, should go away once all irqchips have been converted */
 void handle_IPI(int ipinr, struct pt_regs *regs)
 {
     struct pt_regs *old_regs = set_irq_regs(regs);
 
     irq_enter();
     do_handle_IPI(ipinr);
     irq_exit();
 
     set_irq_regs(old_regs);
 }
 
 static irqreturn_t ipi_handler(int irq, void *data)
 {
     do_handle_IPI(irq - ipi_irq_base);
     return IRQ_HANDLED;
 }
 
 static void smp_cross_call(const struct cpumask *target, unsigned int ipinr)
 {
     trace_ipi_raise_rcuidle(target, ipi_types[ipinr]);
     __ipi_send_mask(ipi_desc[ipinr], target);
 }
 
 static void ipi_setup(int cpu)
 {
     int i;
 
     if (WARN_ON_ONCE(!ipi_irq_base))
         return;
 
     for (i = 0; i < nr_ipi; i++)
         enable_percpu_irq(ipi_irq_base + i, 0);
 }
 
 void __init set_smp_ipi_range(int ipi_base, int n)
 {
     int i;
 
     WARN_ON(n < MAX_IPI);
     nr_ipi = min(n, MAX_IPI);
 
     for (i = 0; i < nr_ipi; i++) {
         int err;
 
         err = request_percpu_irq(ipi_base + i, ipi_handler,
                      "IPI", &irq_stat);
         WARN_ON(err);
 
         ipi_desc[i] = irq_to_desc(ipi_base + i);
         irq_set_status_flags(ipi_base + i, IRQ_HIDDEN);
     }
 
     ipi_irq_base = ipi_base;
 
     /* Setup the boot CPU immediately */
     ipi_setup(smp_processor_id());
 }
 
 void smp_send_reschedule(int cpu)
 {
     smp_cross_call(cpumask_of(cpu), IPI_RESCHEDULE);
 }
 
 void smp_send_stop(void)
 {
     unsigned long timeout;
     struct cpumask mask;
 
     cpumask_copy(&mask, cpu_online_mask);
     cpumask_clear_cpu(smp_processor_id(), &mask);
     if (!cpumask_empty(&mask))
         smp_cross_call(&mask, IPI_CPU_STOP);
 
     /* Wait up to one second for other CPUs to stop */
     timeout = USEC_PER_SEC;
     while (num_online_cpus() > 1 && timeout--)
         udelay(1);
 
     if (num_online_cpus() > 1)
         pr_warn("SMP: failed to stop secondary CPUs\n");
 }
 
 /* In case panic() and panic() called at the same time on CPU1 and CPU2,
  * and CPU 1 calls panic_smp_self_stop() before crash_smp_send_stop()
  * CPU1 can't receive the ipi irqs from CPU2, CPU1 will be always online,
  * kdump fails. So split out the panic_smp_self_stop() and add
  * set_cpu_online(smp_processor_id(), false).
  */
 void panic_smp_self_stop(void)
 {
     pr_debug("CPU %u will stop doing anything useful since another CPU has paniced\n",
              smp_processor_id());
     set_cpu_online(smp_processor_id(), false);
     while (1)
         cpu_relax();
 }
 
 #ifdef CONFIG_CPU_FREQ
 
 static DEFINE_PER_CPU(unsigned long, l_p_j_ref);
 static DEFINE_PER_CPU(unsigned long, l_p_j_ref_freq);
 static unsigned long global_l_p_j_ref;
 static unsigned long global_l_p_j_ref_freq;
 
 static int cpufreq_callback(struct notifier_block *nb,
                     unsigned long val, void *data)
 {
     struct cpufreq_freqs *freq = data;
     struct cpumask *cpus = freq->policy->cpus;
     int cpu, first = cpumask_first(cpus);
     unsigned int lpj;
 
     if (freq->flags & CPUFREQ_CONST_LOOPS)
         return NOTIFY_OK;
 
     if (!per_cpu(l_p_j_ref, first)) {
         for_each_cpu(cpu, cpus) {
             per_cpu(l_p_j_ref, cpu) =
                 per_cpu(cpu_data, cpu).loops_per_jiffy;
             per_cpu(l_p_j_ref_freq, cpu) = freq->old;
         }
 
         if (!global_l_p_j_ref) {
             global_l_p_j_ref = loops_per_jiffy;
             global_l_p_j_ref_freq = freq->old;
         }
     }
 
     if ((val == CPUFREQ_PRECHANGE  && freq->old < freq->new) ||
         (val == CPUFREQ_POSTCHANGE && freq->old > freq->new)) {
         loops_per_jiffy = cpufreq_scale(global_l_p_j_ref,
                         global_l_p_j_ref_freq,
                         freq->new);
 
         lpj = cpufreq_scale(per_cpu(l_p_j_ref, first),
                     per_cpu(l_p_j_ref_freq, first), freq->new);
         for_each_cpu(cpu, cpus)
             per_cpu(cpu_data, cpu).loops_per_jiffy = lpj;
     }
     return NOTIFY_OK;
 }
 
 static struct notifier_block cpufreq_notifier = {
     .notifier_call  = cpufreq_callback,
 };
 
 static int __init register_cpufreq_notifier(void)
 {
     return cpufreq_register_notifier(&cpufreq_notifier,
                         CPUFREQ_TRANSITION_NOTIFIER);
 }
 core_initcall(register_cpufreq_notifier);
 
 #endif
 
 static void raise_nmi(cpumask_t *mask)
 {
     __ipi_send_mask(ipi_desc[IPI_CPU_BACKTRACE], mask);
 }
 
 void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self)
 {
     nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_nmi);
 }

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