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