Root/kernel/smpboot.c

1/*
2 * Common SMP CPU bringup/teardown functions
3 */
4#include <linux/err.h>
5#include <linux/smp.h>
6#include <linux/init.h>
7#include <linux/sched.h>
8#include <linux/percpu.h>
9
10#include "smpboot.h"
11
12#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
13/*
14 * For the hotplug case we keep the task structs around and reuse
15 * them.
16 */
17static DEFINE_PER_CPU(struct task_struct *, idle_threads);
18
19struct task_struct * __cpuinit idle_thread_get(unsigned int cpu)
20{
21    struct task_struct *tsk = per_cpu(idle_threads, cpu);
22
23    if (!tsk)
24        return ERR_PTR(-ENOMEM);
25    init_idle(tsk, cpu);
26    return tsk;
27}
28
29void __init idle_thread_set_boot_cpu(void)
30{
31    per_cpu(idle_threads, smp_processor_id()) = current;
32}
33
34/**
35 * idle_init - Initialize the idle thread for a cpu
36 * @cpu: The cpu for which the idle thread should be initialized
37 *
38 * Creates the thread if it does not exist.
39 */
40static inline void idle_init(unsigned int cpu)
41{
42    struct task_struct *tsk = per_cpu(idle_threads, cpu);
43
44    if (!tsk) {
45        tsk = fork_idle(cpu);
46        if (IS_ERR(tsk))
47            pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
48        else
49            per_cpu(idle_threads, cpu) = tsk;
50    }
51}
52
53/**
54 * idle_threads_init - Initialize idle threads for all cpus
55 */
56void __init idle_threads_init(void)
57{
58    unsigned int cpu, boot_cpu;
59
60    boot_cpu = smp_processor_id();
61
62    for_each_possible_cpu(cpu) {
63        if (cpu != boot_cpu)
64            idle_init(cpu);
65    }
66}
67#endif
68

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