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);
  39void stop_machine_yield(const struct cpumask *cpumask);
  40
  41#else   /* CONFIG_SMP */
  42
  43#include <linux/workqueue.h>
  44
  45struct cpu_stop_work {
  46        struct work_struct      work;
  47        cpu_stop_fn_t           fn;
  48        void                    *arg;
  49};
  50
  51static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
  52{
  53        int ret = -ENOENT;
  54        preempt_disable();
  55        if (cpu == smp_processor_id())
  56                ret = fn(arg);
  57        preempt_enable();
  58        return ret;
  59}
  60
  61static void stop_one_cpu_nowait_workfn(struct work_struct *work)
  62{
  63        struct cpu_stop_work *stwork =
  64                container_of(work, struct cpu_stop_work, work);
  65        preempt_disable();
  66        stwork->fn(stwork->arg);
  67        preempt_enable();
  68}
  69
  70static inline bool stop_one_cpu_nowait(unsigned int cpu,
  71                                       cpu_stop_fn_t fn, void *arg,
  72                                       struct cpu_stop_work *work_buf)
  73{
  74        if (cpu == smp_processor_id()) {
  75                INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
  76                work_buf->fn = fn;
  77                work_buf->arg = arg;
  78                schedule_work(&work_buf->work);
  79                return true;
  80        }
  81
  82        return false;
  83}
  84
  85static inline int stop_cpus(const struct cpumask *cpumask,
  86                            cpu_stop_fn_t fn, void *arg)
  87{
  88        if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
  89                return stop_one_cpu(raw_smp_processor_id(), fn, arg);
  90        return -ENOENT;
  91}
  92
  93static inline int try_stop_cpus(const struct cpumask *cpumask,
  94                                cpu_stop_fn_t fn, void *arg)
  95{
  96        return stop_cpus(cpumask, fn, arg);
  97}
  98
  99#endif  /* CONFIG_SMP */
 100
 101/*
 102 * stop_machine "Bogolock": stop the entire machine, disable
 103 * interrupts.  This is a very heavy lock, which is equivalent to
 104 * grabbing every spinlock (and more).  So the "read" side to such a
 105 * lock is anything which disables preemption.
 106 */
 107#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
 108
 109/**
 110 * stop_machine: freeze the machine on all CPUs and run this function
 111 * @fn: the function to run
 112 * @data: the data ptr for the @fn()
 113 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 114 *
 115 * Description: This causes a thread to be scheduled on every cpu,
 116 * each of which disables interrupts.  The result is that no one is
 117 * holding a spinlock or inside any other preempt-disabled region when
 118 * @fn() runs.
 119 *
 120 * This can be thought of as a very heavy write lock, equivalent to
 121 * grabbing every spinlock in the kernel.
 122 *
 123 * Protects against CPU hotplug.
 124 */
 125int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 126
 127/**
 128 * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
 129 * @fn: the function to run
 130 * @data: the data ptr for the @fn()
 131 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 132 *
 133 * Same as above. Must be called from with in a cpus_read_lock() protected
 134 * region. Avoids nested calls to cpus_read_lock().
 135 */
 136int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 137
 138int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 139                                   const struct cpumask *cpus);
 140#else   /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
 141
 142static inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
 143                                          const struct cpumask *cpus)
 144{
 145        unsigned long flags;
 146        int ret;
 147        local_irq_save(flags);
 148        ret = fn(data);
 149        local_irq_restore(flags);
 150        return ret;
 151}
 152
 153static inline int stop_machine(cpu_stop_fn_t fn, void *data,
 154                               const struct cpumask *cpus)
 155{
 156        return stop_machine_cpuslocked(fn, data, cpus);
 157}
 158
 159static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 160                                                 const struct cpumask *cpus)
 161{
 162        return stop_machine(fn, data, cpus);
 163}
 164
 165#endif  /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
 166#endif  /* _LINUX_STOP_MACHINE */
 167