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	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * kernel/stop_machine.c
  *
  * Copyright (C) 2008, 2005 IBM Corporation.
  * Copyright (C) 2008, 2005 Rusty Russell rusty@rustcorp.com.au
  * Copyright (C) 2010       SUSE Linux Products GmbH
  * Copyright (C) 2010       Tejun Heo <tj@kernel.org>
  */
 #include <linux/compiler.h>
 #include <linux/completion.h>
 #include <linux/cpu.h>
 #include <linux/init.h>
 #include <linux/kthread.h>
 #include <linux/export.h>
 #include <linux/percpu.h>
 #include <linux/sched.h>
 #include <linux/stop_machine.h>
 #include <linux/interrupt.h>
 #include <linux/kallsyms.h>
 #include <linux/smpboot.h>
 #include <linux/atomic.h>
 #include <linux/nmi.h>
 #include <linux/sched/wake_q.h>
 
 /*
  * Structure to determine completion condition and record errors.  May
  * be shared by works on different cpus.
  */
 struct cpu_stop_done {
     atomic_t        nr_todo;    /* nr left to execute */
     int         ret;        /* collected return value */
     struct completion   completion; /* fired if nr_todo reaches 0 */
 };
 
 /* the actual stopper, one per every possible cpu, enabled on online cpus */
 struct cpu_stopper {
     struct task_struct  *thread;
 
     raw_spinlock_t      lock;
     bool            enabled;    /* is this stopper enabled? */
     struct list_head    works;      /* list of pending works */
 
     struct cpu_stop_work    stop_work;  /* for stop_cpus */
     unsigned long       caller;
     cpu_stop_fn_t       fn;
 };
 
 static DEFINE_PER_CPU(struct cpu_stopper, cpu_stopper);
 static bool stop_machine_initialized = false;
 
 void print_stop_info(const char *log_lvl, struct task_struct *task)
 {
     /*
      * If @task is a stopper task, it cannot migrate and task_cpu() is
      * stable.
      */
     struct cpu_stopper *stopper = per_cpu_ptr(&cpu_stopper, task_cpu(task));
 
     if (task != stopper->thread)
         return;
 
     printk("%sStopper: %pS <- %pS\n", log_lvl, stopper->fn, (void *)stopper->caller);
 }
 
 /* static data for stop_cpus */
 static DEFINE_MUTEX(stop_cpus_mutex);
 static bool stop_cpus_in_progress;
 
 static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
 {
     memset(done, 0, sizeof(*done));
     atomic_set(&done->nr_todo, nr_todo);
     init_completion(&done->completion);
 }
 
 /* signal completion unless @done is NULL */
 static void cpu_stop_signal_done(struct cpu_stop_done *done)
 {
     if (atomic_dec_and_test(&done->nr_todo))
         complete(&done->completion);
 }
 
 static void __cpu_stop_queue_work(struct cpu_stopper *stopper,
                     struct cpu_stop_work *work,
                     struct wake_q_head *wakeq)
 {
     list_add_tail(&work->list, &stopper->works);
     wake_q_add(wakeq, stopper->thread);
 }
 
 /* queue @work to @stopper.  if offline, @work is completed immediately */
 static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
 {
     struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
     DEFINE_WAKE_Q(wakeq);
     unsigned long flags;
     bool enabled;
 
     preempt_disable();
     raw_spin_lock_irqsave(&stopper->lock, flags);
     enabled = stopper->enabled;
     if (enabled)
         __cpu_stop_queue_work(stopper, work, &wakeq);
     else if (work->done)
         cpu_stop_signal_done(work->done);
     raw_spin_unlock_irqrestore(&stopper->lock, flags);
 
     wake_up_q(&wakeq);
     preempt_enable();
 
     return enabled;
 }
 
 /**
  * stop_one_cpu - stop a cpu
  * @cpu: cpu to stop
  * @fn: function to execute
  * @arg: argument to @fn
  *
  * Execute @fn(@arg) on @cpu.  @fn is run in a process context with
  * the highest priority preempting any task on the cpu and
  * monopolizing it.  This function returns after the execution is
  * complete.
  *
  * This function doesn't guarantee @cpu stays online till @fn
  * completes.  If @cpu goes down in the middle, execution may happen
  * partially or fully on different cpus.  @fn should either be ready
  * for that or the caller should ensure that @cpu stays online until
  * this function completes.
  *
  * CONTEXT:
  * Might sleep.
  *
  * RETURNS:
  * -ENOENT if @fn(@arg) was not executed because @cpu was offline;
  * otherwise, the return value of @fn.
  */
 int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
 {
     struct cpu_stop_done done;
     struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done, .caller = _RET_IP_ };
 
     cpu_stop_init_done(&done, 1);
     if (!cpu_stop_queue_work(cpu, &work))
         return -ENOENT;
     /*
      * In case @cpu == smp_proccessor_id() we can avoid a sleep+wakeup
      * cycle by doing a preemption:
      */
     cond_resched();
     wait_for_completion(&done.completion);
     return done.ret;
 }
 
 /* This controls the threads on each CPU. */
 enum multi_stop_state {
     /* Dummy starting state for thread. */
     MULTI_STOP_NONE,
     /* Awaiting everyone to be scheduled. */
     MULTI_STOP_PREPARE,
     /* Disable interrupts. */
     MULTI_STOP_DISABLE_IRQ,
     /* Run the function */
     MULTI_STOP_RUN,
     /* Exit */
     MULTI_STOP_EXIT,
 };
 
 struct multi_stop_data {
     cpu_stop_fn_t       fn;
     void            *data;
     /* Like num_online_cpus(), but hotplug cpu uses us, so we need this. */
     unsigned int        num_threads;
     const struct cpumask    *active_cpus;
 
     enum multi_stop_state   state;
     atomic_t        thread_ack;
 };
 
 static void set_state(struct multi_stop_data *msdata,
               enum multi_stop_state newstate)
 {
     /* Reset ack counter. */
     atomic_set(&msdata->thread_ack, msdata->num_threads);
     smp_wmb();
     WRITE_ONCE(msdata->state, newstate);
 }
 
 /* Last one to ack a state moves to the next state. */
 static void ack_state(struct multi_stop_data *msdata)
 {
     if (atomic_dec_and_test(&msdata->thread_ack))
         set_state(msdata, msdata->state + 1);
 }
 
 notrace void __weak stop_machine_yield(const struct cpumask *cpumask)
 {
     cpu_relax();
 }
 
 /* This is the cpu_stop function which stops the CPU. */
 static int multi_cpu_stop(void *data)
 {
     struct multi_stop_data *msdata = data;
     enum multi_stop_state newstate, curstate = MULTI_STOP_NONE;
     int cpu = smp_processor_id(), err = 0;
     const struct cpumask *cpumask;
     unsigned long flags;
     bool is_active;
 
     /*
      * When called from stop_machine_from_inactive_cpu(), irq might
      * already be disabled.  Save the state and restore it on exit.
      */
     local_save_flags(flags);
 
     if (!msdata->active_cpus) {
         cpumask = cpu_online_mask;
         is_active = cpu == cpumask_first(cpumask);
     } else {
         cpumask = msdata->active_cpus;
         is_active = cpumask_test_cpu(cpu, cpumask);
     }
 
     /* Simple state machine */
     do {
         /* Chill out and ensure we re-read multi_stop_state. */
         stop_machine_yield(cpumask);
         newstate = READ_ONCE(msdata->state);
         if (newstate != curstate) {
             curstate = newstate;
             switch (curstate) {
             case MULTI_STOP_DISABLE_IRQ:
                 local_irq_disable();
                 hard_irq_disable();
                 break;
             case MULTI_STOP_RUN:
                 if (is_active)
                     err = msdata->fn(msdata->data);
                 break;
             default:
                 break;
             }
             ack_state(msdata);
         } else if (curstate > MULTI_STOP_PREPARE) {
             /*
              * At this stage all other CPUs we depend on must spin
              * in the same loop. Any reason for hard-lockup should
              * be detected and reported on their side.
              */
             touch_nmi_watchdog();
         }
         rcu_momentary_dyntick_idle();
     } while (curstate != MULTI_STOP_EXIT);
 
     local_irq_restore(flags);
     return err;
 }
 
 static int cpu_stop_queue_two_works(int cpu1, struct cpu_stop_work *work1,
                     int cpu2, struct cpu_stop_work *work2)
 {
     struct cpu_stopper *stopper1 = per_cpu_ptr(&cpu_stopper, cpu1);
     struct cpu_stopper *stopper2 = per_cpu_ptr(&cpu_stopper, cpu2);
     DEFINE_WAKE_Q(wakeq);
     int err;
 
 retry:
     /*
      * The waking up of stopper threads has to happen in the same
      * scheduling context as the queueing.  Otherwise, there is a
      * possibility of one of the above stoppers being woken up by another
      * CPU, and preempting us. This will cause us to not wake up the other
      * stopper forever.
      */
     preempt_disable();
     raw_spin_lock_irq(&stopper1->lock);
     raw_spin_lock_nested(&stopper2->lock, SINGLE_DEPTH_NESTING);
 
     if (!stopper1->enabled || !stopper2->enabled) {
         err = -ENOENT;
         goto unlock;
     }
 
     /*
      * Ensure that if we race with __stop_cpus() the stoppers won't get
      * queued up in reverse order leading to system deadlock.
      *
      * We can't miss stop_cpus_in_progress if queue_stop_cpus_work() has
      * queued a work on cpu1 but not on cpu2, we hold both locks.
      *
      * It can be falsely true but it is safe to spin until it is cleared,
      * queue_stop_cpus_work() does everything under preempt_disable().
      */
     if (unlikely(stop_cpus_in_progress)) {
         err = -EDEADLK;
         goto unlock;
     }
 
     err = 0;
     __cpu_stop_queue_work(stopper1, work1, &wakeq);
     __cpu_stop_queue_work(stopper2, work2, &wakeq);
 
 unlock:
     raw_spin_unlock(&stopper2->lock);
     raw_spin_unlock_irq(&stopper1->lock);
 
     if (unlikely(err == -EDEADLK)) {
         preempt_enable();
 
         while (stop_cpus_in_progress)
             cpu_relax();
 
         goto retry;
     }
 
     wake_up_q(&wakeq);
     preempt_enable();
 
     return err;
 }
 /**
  * stop_two_cpus - stops two cpus
  * @cpu1: the cpu to stop
  * @cpu2: the other cpu to stop
  * @fn: function to execute
  * @arg: argument to @fn
  *
  * Stops both the current and specified CPU and runs @fn on one of them.
  *
  * returns when both are completed.
  */
 int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg)
 {
     struct cpu_stop_done done;
     struct cpu_stop_work work1, work2;
     struct multi_stop_data msdata;
 
     msdata = (struct multi_stop_data){
         .fn = fn,
         .data = arg,
         .num_threads = 2,
         .active_cpus = cpumask_of(cpu1),
     };
 
     work1 = work2 = (struct cpu_stop_work){
         .fn = multi_cpu_stop,
         .arg = &msdata,
         .done = &done,
         .caller = _RET_IP_,
     };
 
     cpu_stop_init_done(&done, 2);
     set_state(&msdata, MULTI_STOP_PREPARE);
 
     if (cpu1 > cpu2)
         swap(cpu1, cpu2);
     if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2))
         return -ENOENT;
 
     wait_for_completion(&done.completion);
     return done.ret;
 }
 
 /**
  * stop_one_cpu_nowait - stop a cpu but don't wait for completion
  * @cpu: cpu to stop
  * @fn: function to execute
  * @arg: argument to @fn
  * @work_buf: pointer to cpu_stop_work structure
  *
  * Similar to stop_one_cpu() but doesn't wait for completion.  The
  * caller is responsible for ensuring @work_buf is currently unused
  * and will remain untouched until stopper starts executing @fn.
  *
  * CONTEXT:
  * Don't care.
  *
  * RETURNS:
  * true if cpu_stop_work was queued successfully and @fn will be called,
  * false otherwise.
  */
 bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
             struct cpu_stop_work *work_buf)
 {
     *work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, .caller = _RET_IP_, };
     return cpu_stop_queue_work(cpu, work_buf);
 }
 
 static bool queue_stop_cpus_work(const struct cpumask *cpumask,
                  cpu_stop_fn_t fn, void *arg,
                  struct cpu_stop_done *done)
 {
     struct cpu_stop_work *work;
     unsigned int cpu;
     bool queued = false;
 
     /*
      * Disable preemption while queueing to avoid getting
      * preempted by a stopper which might wait for other stoppers
      * to enter @fn which can lead to deadlock.
      */
     preempt_disable();
     stop_cpus_in_progress = true;
     barrier();
     for_each_cpu(cpu, cpumask) {
         work = &per_cpu(cpu_stopper.stop_work, cpu);
         work->fn = fn;
         work->arg = arg;
         work->done = done;
         work->caller = _RET_IP_;
         if (cpu_stop_queue_work(cpu, work))
             queued = true;
     }
     barrier();
     stop_cpus_in_progress = false;
     preempt_enable();
 
     return queued;
 }
 
 static int __stop_cpus(const struct cpumask *cpumask,
                cpu_stop_fn_t fn, void *arg)
 {
     struct cpu_stop_done done;
 
     cpu_stop_init_done(&done, cpumask_weight(cpumask));
     if (!queue_stop_cpus_work(cpumask, fn, arg, &done))
         return -ENOENT;
     wait_for_completion(&done.completion);
     return done.ret;
 }
 
 /**
  * stop_cpus - stop multiple cpus
  * @cpumask: cpus to stop
  * @fn: function to execute
  * @arg: argument to @fn
  *
  * Execute @fn(@arg) on online cpus in @cpumask.  On each target cpu,
  * @fn is run in a process context with the highest priority
  * preempting any task on the cpu and monopolizing it.  This function
  * returns after all executions are complete.
  *
  * This function doesn't guarantee the cpus in @cpumask stay online
  * till @fn completes.  If some cpus go down in the middle, execution
  * on the cpu may happen partially or fully on different cpus.  @fn
  * should either be ready for that or the caller should ensure that
  * the cpus stay online until this function completes.
  *
  * All stop_cpus() calls are serialized making it safe for @fn to wait
  * for all cpus to start executing it.
  *
  * CONTEXT:
  * Might sleep.
  *
  * RETURNS:
  * -ENOENT if @fn(@arg) was not executed at all because all cpus in
  * @cpumask were offline; otherwise, 0 if all executions of @fn
  * returned 0, any non zero return value if any returned non zero.
  */
 static int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg)
 {
     int ret;
 
     /* static works are used, process one request at a time */
     mutex_lock(&stop_cpus_mutex);
     ret = __stop_cpus(cpumask, fn, arg);
     mutex_unlock(&stop_cpus_mutex);
     return ret;
 }
 
 static int cpu_stop_should_run(unsigned int cpu)
 {
     struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
     unsigned long flags;
     int run;
 
     raw_spin_lock_irqsave(&stopper->lock, flags);
     run = !list_empty(&stopper->works);
     raw_spin_unlock_irqrestore(&stopper->lock, flags);
     return run;
 }
 
 static void cpu_stopper_thread(unsigned int cpu)
 {
     struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
     struct cpu_stop_work *work;
 
 repeat:
     work = NULL;
     raw_spin_lock_irq(&stopper->lock);
     if (!list_empty(&stopper->works)) {
         work = list_first_entry(&stopper->works,
                     struct cpu_stop_work, list);
         list_del_init(&work->list);
     }
     raw_spin_unlock_irq(&stopper->lock);
 
     if (work) {
         cpu_stop_fn_t fn = work->fn;
         void *arg = work->arg;
         struct cpu_stop_done *done = work->done;
         int ret;
 
         /* cpu stop callbacks must not sleep, make in_atomic() == T */
         stopper->caller = work->caller;
         stopper->fn = fn;
         preempt_count_inc();
         ret = fn(arg);
         if (done) {
             if (ret)
                 done->ret = ret;
             cpu_stop_signal_done(done);
         }
         preempt_count_dec();
         stopper->fn = NULL;
         stopper->caller = 0;
         WARN_ONCE(preempt_count(),
               "cpu_stop: %ps(%p) leaked preempt count\n", fn, arg);
         goto repeat;
     }
 }
 
 void stop_machine_park(int cpu)
 {
     struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
     /*
      * Lockless. cpu_stopper_thread() will take stopper->lock and flush
      * the pending works before it parks, until then it is fine to queue
      * the new works.
      */
     stopper->enabled = false;
     kthread_park(stopper->thread);
 }
 
 static void cpu_stop_create(unsigned int cpu)
 {
     sched_set_stop_task(cpu, per_cpu(cpu_stopper.thread, cpu));
 }
 
 static void cpu_stop_park(unsigned int cpu)
 {
     struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
 
     WARN_ON(!list_empty(&stopper->works));
 }
 
 void stop_machine_unpark(int cpu)
 {
     struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
 
     stopper->enabled = true;
     kthread_unpark(stopper->thread);
 }
 
 static struct smp_hotplug_thread cpu_stop_threads = {
     .store          = &cpu_stopper.thread,
     .thread_should_run  = cpu_stop_should_run,
     .thread_fn      = cpu_stopper_thread,
     .thread_comm        = "migration/%u",
     .create         = cpu_stop_create,
     .park           = cpu_stop_park,
     .selfparking        = true,
 };
 
 static int __init cpu_stop_init(void)
 {
     unsigned int cpu;
 
     for_each_possible_cpu(cpu) {
         struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
 
         raw_spin_lock_init(&stopper->lock);
         INIT_LIST_HEAD(&stopper->works);
     }
 
     BUG_ON(smpboot_register_percpu_thread(&cpu_stop_threads));
     stop_machine_unpark(raw_smp_processor_id());
     stop_machine_initialized = true;
     return 0;
 }
 early_initcall(cpu_stop_init);
 
 int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
                 const struct cpumask *cpus)
 {
     struct multi_stop_data msdata = {
         .fn = fn,
         .data = data,
         .num_threads = num_online_cpus(),
         .active_cpus = cpus,
     };
 
     lockdep_assert_cpus_held();
 
     if (!stop_machine_initialized) {
         /*
          * Handle the case where stop_machine() is called
          * early in boot before stop_machine() has been
          * initialized.
          */
         unsigned long flags;
         int ret;
 
         WARN_ON_ONCE(msdata.num_threads != 1);
 
         local_irq_save(flags);
         hard_irq_disable();
         ret = (*fn)(data);
         local_irq_restore(flags);
 
         return ret;
     }
 
     /* Set the initial state and stop all online cpus. */
     set_state(&msdata, MULTI_STOP_PREPARE);
     return stop_cpus(cpu_online_mask, multi_cpu_stop, &msdata);
 }
 
 int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
 {
     int ret;
 
     /* No CPUs can come up or down during this. */
     cpus_read_lock();
     ret = stop_machine_cpuslocked(fn, data, cpus);
     cpus_read_unlock();
     return ret;
 }
 EXPORT_SYMBOL_GPL(stop_machine);
 
 #ifdef CONFIG_SCHED_SMT
 int stop_core_cpuslocked(unsigned int cpu, cpu_stop_fn_t fn, void *data)
 {
     const struct cpumask *smt_mask = cpu_smt_mask(cpu);
 
     struct multi_stop_data msdata = {
         .fn = fn,
         .data = data,
         .num_threads = cpumask_weight(smt_mask),
         .active_cpus = smt_mask,
     };
 
     lockdep_assert_cpus_held();
 
     /* Set the initial state and stop all online cpus. */
     set_state(&msdata, MULTI_STOP_PREPARE);
     return stop_cpus(smt_mask, multi_cpu_stop, &msdata);
 }
 EXPORT_SYMBOL_GPL(stop_core_cpuslocked);
 #endif
 
 /**
  * stop_machine_from_inactive_cpu - stop_machine() from inactive CPU
  * @fn: the function to run
  * @data: the data ptr for the @fn()
  * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
  *
  * This is identical to stop_machine() but can be called from a CPU which
  * is not active.  The local CPU is in the process of hotplug (so no other
  * CPU hotplug can start) and not marked active and doesn't have enough
  * context to sleep.
  *
  * This function provides stop_machine() functionality for such state by
  * using busy-wait for synchronization and executing @fn directly for local
  * CPU.
  *
  * CONTEXT:
  * Local CPU is inactive.  Temporarily stops all active CPUs.
  *
  * RETURNS:
  * 0 if all executions of @fn returned 0, any non zero return value if any
  * returned non zero.
  */
 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
                   const struct cpumask *cpus)
 {
     struct multi_stop_data msdata = { .fn = fn, .data = data,
                         .active_cpus = cpus };
     struct cpu_stop_done done;
     int ret;
 
     /* Local CPU must be inactive and CPU hotplug in progress. */
     BUG_ON(cpu_active(raw_smp_processor_id()));
     msdata.num_threads = num_active_cpus() + 1; /* +1 for local */
 
     /* No proper task established and can't sleep - busy wait for lock. */
     while (!mutex_trylock(&stop_cpus_mutex))
         cpu_relax();
 
     /* Schedule work on other CPUs and execute directly for local CPU */
     set_state(&msdata, MULTI_STOP_PREPARE);
     cpu_stop_init_done(&done, num_active_cpus());
     queue_stop_cpus_work(cpu_active_mask, multi_cpu_stop, &msdata,
                  &done);
     ret = multi_cpu_stop(&msdata);
 
     /* Busy wait for completion. */
     while (!completion_done(&done.completion))
         cpu_relax();
 
     mutex_unlock(&stop_cpus_mutex);
     return ret ?: done.ret;
 }

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