LXR linux/include/linux/stop

   1/* SPDX-License-Identifier: GPL-2.0 */
   2#ifndef _LINUX_STOP_MACHINE
   3#define _LINUX_STOP_MACHINE
   4
   5#include <linux/cpu.h>
   6#include <linux/cpumask.h>
   7#include <linux/smp.h>
   8#include <linux/list.h>
   9
  10/*
  11 * stop_cpu[s]() is simplistic per-cpu maximum priority cpu
  12 * monopolization mechanism.  The caller can specify a non-sleeping
  13 * function to be executed on a single or multiple cpus preempting all
  14 * other processes and monopolizing those cpus until it finishes.
  15 *
  16 * Resources for this mechanism are preallocated when a cpu is brought
  17 * up and requests are guaranteed to be served as long as the target
  18 * cpus are online.
  19 */
  20typedef int (*cpu_stop_fn_t)(void *arg);
  21
  22#ifdef CONFIG_SMP
  23
  24struct cpu_stop_work {
  25        struct list_head        list;           /* cpu_stopper->works */
  26        cpu_stop_fn_t           fn;
  27        void                    *arg;
  28        struct cpu_stop_done    *done;
  29};
  30
  31int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
  32int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
  33bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
  34                         struct cpu_stop_work *work_buf);
  35int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
  36int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
  37void stop_machine_park(int cpu);
  38void stop_machine_unpark(int cpu);
  39
  40#else   /* CONFIG_SMP */
  41
  42#include <linux/workqueue.h>
  43
  44struct cpu_stop_work {
  45        struct work_struct      work;
  46        cpu_stop_fn_t           fn;
  47        void                    *arg;
  48};
  49
  50static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
  51{
  52        int ret = -ENOENT;
  53        preempt_disable();
  54        if (cpu == smp_processor_id())
  55                ret = fn(arg);
  56        preempt_enable();
  57        return ret;
  58}
  59
  60static void stop_one_cpu_nowait_workfn(struct work_struct *work)
  61{
  62        struct cpu_stop_work *stwork =
  63                container_of(work, struct cpu_stop_work, work);
  64        preempt_disable();
  65        stwork->fn(stwork->arg);
  66        preempt_enable();
  67}
  68
  69static inline bool stop_one_cpu_nowait(unsigned int cpu,
  70                                       cpu_stop_fn_t fn, void *arg,
  71                                       struct cpu_stop_work *work_buf)
  72{
  73        if (cpu == smp_processor_id()) {
  74                INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
  75                work_buf->fn = fn;
  76                work_buf->arg = arg;
  77                schedule_work(&work_buf->work);
  78                return true;
  79        }
  80
  81        return false;
  82}
  83
  84static inline int stop_cpus(const struct cpumask *cpumask,
  85                            cpu_stop_fn_t fn, void *arg)
  86{
  87        if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
  88                return stop_one_cpu(raw_smp_processor_id(), fn, arg);
  89        return -ENOENT;
  90}
  91
  92static inline int try_stop_cpus(const struct cpumask *cpumask,
  93                                cpu_stop_fn_t fn, void *arg)
  94{
  95        return stop_cpus(cpumask, fn, arg);
  96}
  97
  98#endif  /* CONFIG_SMP */
  99
 100/*
 101 * stop_machine "Bogolock": stop the entire machine, disable
 102 * interrupts.  This is a very heavy lock, which is equivalent to
 103 * grabbing every spinlock (and more).  So the "read" side to such a
 104 * lock is anything which disables preemption.
 105 */
 106#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
 107
 108/**
 109 * stop_machine: freeze the machine on all CPUs and run this function
 110 * @fn: the function to run
 111 * @data: the data ptr for the @fn()
 112 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 113 *
 114 * Description: This causes a thread to be scheduled on every cpu,
 115 * each of which disables interrupts.  The result is that no one is
 116 * holding a spinlock or inside any other preempt-disabled region when
 117 * @fn() runs.
 118 *
 119 * This can be thought of as a very heavy write lock, equivalent to
 120 * grabbing every spinlock in the kernel.
 121 *
 122 * Protects against CPU hotplug.
 123 */
 124int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 125
 126/**
 127 * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
 128 * @fn: the function to run
 129 * @data: the data ptr for the @fn()
 130 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 131 *
 132 * Same as above. Must be called from with in a cpus_read_lock() protected
 133 * region. Avoids nested calls to cpus_read_lock().
 134 */
 135int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 136
 137int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 138                                   const struct cpumask *cpus);
 139#else   /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
 140
 141static inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
 142                                          const struct cpumask *cpus)
 143{
 144        unsigned long flags;
 145        int ret;
 146        local_irq_save(flags);
 147        ret = fn(data);
 148        local_irq_restore(flags);
 149        return ret;
 150}
 151
 152static inline int stop_machine(cpu_stop_fn_t fn, void *data,
 153                               const struct cpumask *cpus)
 154{
 155        return stop_machine_cpuslocked(fn, data, cpus);
 156}
 157
 158static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 159                                                 const struct cpumask *cpus)
 160{
 161        return stop_machine(fn, data, cpus);
 162}
 163
 164#endif  /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
 165#endif  /* _LINUX_STOP_MACHINE */
 166