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457c899653
Add SPDX license identifiers to all files which: - Have no license information of any form - Have EXPORT_.*_SYMBOL_GPL inside which was used in the initial scan/conversion to ignore the file These files fall under the project license, GPL v2 only. The resulting SPDX license identifier is: GPL-2.0-only Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
482 lines
12 KiB
C
482 lines
12 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Common SMP CPU bringup/teardown functions
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*/
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#include <linux/cpu.h>
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#include <linux/err.h>
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#include <linux/smp.h>
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#include <linux/delay.h>
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#include <linux/init.h>
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/sched.h>
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#include <linux/sched/task.h>
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#include <linux/export.h>
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#include <linux/percpu.h>
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#include <linux/kthread.h>
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#include <linux/smpboot.h>
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#include "smpboot.h"
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#ifdef CONFIG_SMP
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#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
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/*
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* For the hotplug case we keep the task structs around and reuse
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* them.
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*/
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static DEFINE_PER_CPU(struct task_struct *, idle_threads);
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struct task_struct *idle_thread_get(unsigned int cpu)
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{
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struct task_struct *tsk = per_cpu(idle_threads, cpu);
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if (!tsk)
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return ERR_PTR(-ENOMEM);
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init_idle(tsk, cpu);
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return tsk;
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}
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void __init idle_thread_set_boot_cpu(void)
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{
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per_cpu(idle_threads, smp_processor_id()) = current;
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}
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/**
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* idle_init - Initialize the idle thread for a cpu
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* @cpu: The cpu for which the idle thread should be initialized
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*
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* Creates the thread if it does not exist.
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*/
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static inline void idle_init(unsigned int cpu)
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{
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struct task_struct *tsk = per_cpu(idle_threads, cpu);
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if (!tsk) {
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tsk = fork_idle(cpu);
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if (IS_ERR(tsk))
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pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
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else
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per_cpu(idle_threads, cpu) = tsk;
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}
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}
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/**
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* idle_threads_init - Initialize idle threads for all cpus
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*/
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void __init idle_threads_init(void)
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{
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unsigned int cpu, boot_cpu;
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boot_cpu = smp_processor_id();
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for_each_possible_cpu(cpu) {
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if (cpu != boot_cpu)
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idle_init(cpu);
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}
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}
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#endif
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#endif /* #ifdef CONFIG_SMP */
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static LIST_HEAD(hotplug_threads);
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static DEFINE_MUTEX(smpboot_threads_lock);
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struct smpboot_thread_data {
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unsigned int cpu;
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unsigned int status;
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struct smp_hotplug_thread *ht;
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};
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enum {
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HP_THREAD_NONE = 0,
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HP_THREAD_ACTIVE,
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HP_THREAD_PARKED,
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};
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/**
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* smpboot_thread_fn - percpu hotplug thread loop function
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* @data: thread data pointer
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*
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* Checks for thread stop and park conditions. Calls the necessary
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* setup, cleanup, park and unpark functions for the registered
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* thread.
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*
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* Returns 1 when the thread should exit, 0 otherwise.
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*/
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static int smpboot_thread_fn(void *data)
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{
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struct smpboot_thread_data *td = data;
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struct smp_hotplug_thread *ht = td->ht;
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while (1) {
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set_current_state(TASK_INTERRUPTIBLE);
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preempt_disable();
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if (kthread_should_stop()) {
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__set_current_state(TASK_RUNNING);
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preempt_enable();
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/* cleanup must mirror setup */
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if (ht->cleanup && td->status != HP_THREAD_NONE)
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ht->cleanup(td->cpu, cpu_online(td->cpu));
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kfree(td);
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return 0;
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}
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if (kthread_should_park()) {
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__set_current_state(TASK_RUNNING);
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preempt_enable();
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if (ht->park && td->status == HP_THREAD_ACTIVE) {
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BUG_ON(td->cpu != smp_processor_id());
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ht->park(td->cpu);
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td->status = HP_THREAD_PARKED;
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}
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kthread_parkme();
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/* We might have been woken for stop */
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continue;
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}
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BUG_ON(td->cpu != smp_processor_id());
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/* Check for state change setup */
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switch (td->status) {
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case HP_THREAD_NONE:
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__set_current_state(TASK_RUNNING);
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preempt_enable();
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if (ht->setup)
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ht->setup(td->cpu);
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td->status = HP_THREAD_ACTIVE;
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continue;
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case HP_THREAD_PARKED:
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__set_current_state(TASK_RUNNING);
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preempt_enable();
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if (ht->unpark)
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ht->unpark(td->cpu);
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td->status = HP_THREAD_ACTIVE;
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continue;
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}
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if (!ht->thread_should_run(td->cpu)) {
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preempt_enable_no_resched();
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schedule();
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} else {
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__set_current_state(TASK_RUNNING);
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preempt_enable();
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ht->thread_fn(td->cpu);
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}
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}
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}
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static int
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__smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
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{
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struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
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struct smpboot_thread_data *td;
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if (tsk)
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return 0;
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td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
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if (!td)
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return -ENOMEM;
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td->cpu = cpu;
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td->ht = ht;
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tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
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ht->thread_comm);
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if (IS_ERR(tsk)) {
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kfree(td);
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return PTR_ERR(tsk);
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}
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/*
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* Park the thread so that it could start right on the CPU
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* when it is available.
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*/
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kthread_park(tsk);
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get_task_struct(tsk);
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*per_cpu_ptr(ht->store, cpu) = tsk;
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if (ht->create) {
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/*
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* Make sure that the task has actually scheduled out
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* into park position, before calling the create
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* callback. At least the migration thread callback
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* requires that the task is off the runqueue.
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*/
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if (!wait_task_inactive(tsk, TASK_PARKED))
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WARN_ON(1);
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else
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ht->create(cpu);
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}
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return 0;
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}
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int smpboot_create_threads(unsigned int cpu)
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{
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struct smp_hotplug_thread *cur;
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int ret = 0;
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mutex_lock(&smpboot_threads_lock);
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list_for_each_entry(cur, &hotplug_threads, list) {
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ret = __smpboot_create_thread(cur, cpu);
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if (ret)
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break;
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}
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mutex_unlock(&smpboot_threads_lock);
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return ret;
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}
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static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
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{
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struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
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if (!ht->selfparking)
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kthread_unpark(tsk);
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}
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int smpboot_unpark_threads(unsigned int cpu)
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{
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struct smp_hotplug_thread *cur;
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mutex_lock(&smpboot_threads_lock);
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list_for_each_entry(cur, &hotplug_threads, list)
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smpboot_unpark_thread(cur, cpu);
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mutex_unlock(&smpboot_threads_lock);
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return 0;
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}
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static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
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{
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struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
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if (tsk && !ht->selfparking)
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kthread_park(tsk);
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}
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int smpboot_park_threads(unsigned int cpu)
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{
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struct smp_hotplug_thread *cur;
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mutex_lock(&smpboot_threads_lock);
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list_for_each_entry_reverse(cur, &hotplug_threads, list)
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smpboot_park_thread(cur, cpu);
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mutex_unlock(&smpboot_threads_lock);
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return 0;
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}
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static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
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{
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unsigned int cpu;
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/* We need to destroy also the parked threads of offline cpus */
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for_each_possible_cpu(cpu) {
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struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
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if (tsk) {
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kthread_stop(tsk);
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put_task_struct(tsk);
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*per_cpu_ptr(ht->store, cpu) = NULL;
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}
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}
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}
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/**
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* smpboot_register_percpu_thread - Register a per_cpu thread related
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* to hotplug
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* @plug_thread: Hotplug thread descriptor
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*
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* Creates and starts the threads on all online cpus.
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*/
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int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread)
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{
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unsigned int cpu;
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int ret = 0;
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get_online_cpus();
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mutex_lock(&smpboot_threads_lock);
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for_each_online_cpu(cpu) {
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ret = __smpboot_create_thread(plug_thread, cpu);
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if (ret) {
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smpboot_destroy_threads(plug_thread);
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goto out;
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}
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smpboot_unpark_thread(plug_thread, cpu);
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}
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list_add(&plug_thread->list, &hotplug_threads);
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out:
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mutex_unlock(&smpboot_threads_lock);
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put_online_cpus();
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return ret;
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}
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EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);
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/**
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* smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
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* @plug_thread: Hotplug thread descriptor
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*
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* Stops all threads on all possible cpus.
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*/
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void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
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{
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get_online_cpus();
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mutex_lock(&smpboot_threads_lock);
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list_del(&plug_thread->list);
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smpboot_destroy_threads(plug_thread);
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mutex_unlock(&smpboot_threads_lock);
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put_online_cpus();
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}
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EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
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static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD);
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/*
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* Called to poll specified CPU's state, for example, when waiting for
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* a CPU to come online.
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*/
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int cpu_report_state(int cpu)
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{
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return atomic_read(&per_cpu(cpu_hotplug_state, cpu));
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}
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/*
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* If CPU has died properly, set its state to CPU_UP_PREPARE and
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* return success. Otherwise, return -EBUSY if the CPU died after
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* cpu_wait_death() timed out. And yet otherwise again, return -EAGAIN
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* if cpu_wait_death() timed out and the CPU still hasn't gotten around
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* to dying. In the latter two cases, the CPU might not be set up
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* properly, but it is up to the arch-specific code to decide.
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* Finally, -EIO indicates an unanticipated problem.
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*
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* Note that it is permissible to omit this call entirely, as is
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* done in architectures that do no CPU-hotplug error checking.
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*/
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int cpu_check_up_prepare(int cpu)
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{
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if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
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atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
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return 0;
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}
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switch (atomic_read(&per_cpu(cpu_hotplug_state, cpu))) {
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case CPU_POST_DEAD:
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/* The CPU died properly, so just start it up again. */
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atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
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return 0;
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case CPU_DEAD_FROZEN:
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/*
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* Timeout during CPU death, so let caller know.
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* The outgoing CPU completed its processing, but after
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* cpu_wait_death() timed out and reported the error. The
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* caller is free to proceed, in which case the state
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* will be reset properly by cpu_set_state_online().
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* Proceeding despite this -EBUSY return makes sense
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* for systems where the outgoing CPUs take themselves
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* offline, with no post-death manipulation required from
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* a surviving CPU.
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*/
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return -EBUSY;
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case CPU_BROKEN:
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/*
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* The most likely reason we got here is that there was
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* a timeout during CPU death, and the outgoing CPU never
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* did complete its processing. This could happen on
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* a virtualized system if the outgoing VCPU gets preempted
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* for more than five seconds, and the user attempts to
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* immediately online that same CPU. Trying again later
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* might return -EBUSY above, hence -EAGAIN.
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*/
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return -EAGAIN;
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default:
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/* Should not happen. Famous last words. */
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return -EIO;
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}
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}
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/*
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* Mark the specified CPU online.
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*
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* Note that it is permissible to omit this call entirely, as is
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* done in architectures that do no CPU-hotplug error checking.
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*/
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void cpu_set_state_online(int cpu)
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{
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(void)atomic_xchg(&per_cpu(cpu_hotplug_state, cpu), CPU_ONLINE);
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}
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#ifdef CONFIG_HOTPLUG_CPU
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/*
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* Wait for the specified CPU to exit the idle loop and die.
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*/
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bool cpu_wait_death(unsigned int cpu, int seconds)
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{
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int jf_left = seconds * HZ;
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int oldstate;
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bool ret = true;
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int sleep_jf = 1;
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might_sleep();
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/* The outgoing CPU will normally get done quite quickly. */
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if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
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goto update_state;
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udelay(5);
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/* But if the outgoing CPU dawdles, wait increasingly long times. */
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while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) {
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schedule_timeout_uninterruptible(sleep_jf);
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jf_left -= sleep_jf;
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if (jf_left <= 0)
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break;
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sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10);
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}
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update_state:
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oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
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if (oldstate == CPU_DEAD) {
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/* Outgoing CPU died normally, update state. */
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smp_mb(); /* atomic_read() before update. */
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atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD);
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} else {
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/* Outgoing CPU still hasn't died, set state accordingly. */
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if (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
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oldstate, CPU_BROKEN) != oldstate)
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goto update_state;
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ret = false;
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}
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return ret;
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}
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/*
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* Called by the outgoing CPU to report its successful death. Return
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* false if this report follows the surviving CPU's timing out.
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*
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* A separate "CPU_DEAD_FROZEN" is used when the surviving CPU
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* timed out. This approach allows architectures to omit calls to
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* cpu_check_up_prepare() and cpu_set_state_online() without defeating
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* the next cpu_wait_death()'s polling loop.
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*/
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bool cpu_report_death(void)
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{
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int oldstate;
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int newstate;
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int cpu = smp_processor_id();
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do {
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oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
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if (oldstate != CPU_BROKEN)
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newstate = CPU_DEAD;
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else
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newstate = CPU_DEAD_FROZEN;
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} while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
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oldstate, newstate) != oldstate);
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return newstate == CPU_DEAD;
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}
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#endif /* #ifdef CONFIG_HOTPLUG_CPU */
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