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);
  35void stop_machine_park(int cpu);
  36void stop_machine_unpark(int cpu);
  37void stop_machine_yield(const struct cpumask *cpumask);
  38
  39#else   /* CONFIG_SMP */
  40
  41#include <linux/workqueue.h>
  42
  43struct cpu_stop_work {
  44        struct work_struct      work;
  45        cpu_stop_fn_t           fn;
  46        void                    *arg;
  47};
  48
  49static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
  50{
  51        int ret = -ENOENT;
  52        preempt_disable();
  53        if (cpu == smp_processor_id())
  54                ret = fn(arg);
  55        preempt_enable();
  56        return ret;
  57}
  58
  59static void stop_one_cpu_nowait_workfn(struct work_struct *work)
  60{
  61        struct cpu_stop_work *stwork =
  62                container_of(work, struct cpu_stop_work, work);
  63        preempt_disable();
  64        stwork->fn(stwork->arg);
  65        preempt_enable();
  66}
  67
  68static inline bool stop_one_cpu_nowait(unsigned int cpu,
  69                                       cpu_stop_fn_t fn, void *arg,
  70                                       struct cpu_stop_work *work_buf)
  71{
  72        if (cpu == smp_processor_id()) {
  73                INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
  74                work_buf->fn = fn;
  75                work_buf->arg = arg;
  76                schedule_work(&work_buf->work);
  77                return true;
  78        }
  79
  80        return false;
  81}
  82
  83#endif  /* CONFIG_SMP */
  84
  85/*
  86 * stop_machine "Bogolock": stop the entire machine, disable
  87 * interrupts.  This is a very heavy lock, which is equivalent to
  88 * grabbing every spinlock (and more).  So the "read" side to such a
  89 * lock is anything which disables preemption.
  90 */
  91#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
  92
  93/**
  94 * stop_machine: freeze the machine on all CPUs and run this function
  95 * @fn: the function to run
  96 * @data: the data ptr for the @fn()
  97 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
  98 *
  99 * Description: This causes a thread to be scheduled on every cpu,
 100 * each of which disables interrupts.  The result is that no one is
 101 * holding a spinlock or inside any other preempt-disabled region when
 102 * @fn() runs.
 103 *
 104 * This can be thought of as a very heavy write lock, equivalent to
 105 * grabbing every spinlock in the kernel.
 106 *
 107 * Protects against CPU hotplug.
 108 */
 109int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 110
 111/**
 112 * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
 113 * @fn: the function to run
 114 * @data: the data ptr for the @fn()
 115 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 116 *
 117 * Same as above. Must be called from with in a cpus_read_lock() protected
 118 * region. Avoids nested calls to cpus_read_lock().
 119 */
 120int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 121
 122int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 123                                   const struct cpumask *cpus);
 124#else   /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
 125
 126static inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
 127                                          const struct cpumask *cpus)
 128{
 129        unsigned long flags;
 130        int ret;
 131        local_irq_save(flags);
 132        ret = fn(data);
 133        local_irq_restore(flags);
 134        return ret;
 135}
 136
 137static inline int stop_machine(cpu_stop_fn_t fn, void *data,
 138                               const struct cpumask *cpus)
 139{
 140        return stop_machine_cpuslocked(fn, data, cpus);
 141}
 142
 143static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 144                                                 const struct cpumask *cpus)
 145{
 146        return stop_machine(fn, data, cpus);
 147}
 148
 149#endif  /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
 150#endif  /* _LINUX_STOP_MACHINE */
 151