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	unsigned long		caller;
28	void			*arg;
29	struct cpu_stop_done	*done;
30};
31
32int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
33int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
34bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
35			 struct cpu_stop_work *work_buf);
36void stop_machine_park(int cpu);
37void stop_machine_unpark(int cpu);
38void stop_machine_yield(const struct cpumask *cpumask);
39
40extern void print_stop_info(const char *log_lvl, struct task_struct *task);
41
42#else	/* CONFIG_SMP */
43
44#include <linux/workqueue.h>
45
46struct cpu_stop_work {
47	struct work_struct	work;
48	cpu_stop_fn_t		fn;
49	void			*arg;
50};
51
52static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
53{
54	int ret = -ENOENT;
55	preempt_disable();
56	if (cpu == smp_processor_id())
57		ret = fn(arg);
58	preempt_enable();
59	return ret;
60}
61
62static void stop_one_cpu_nowait_workfn(struct work_struct *work)
63{
64	struct cpu_stop_work *stwork =
65		container_of(work, struct cpu_stop_work, work);
66	preempt_disable();
67	stwork->fn(stwork->arg);
68	preempt_enable();
69}
70
71static inline bool stop_one_cpu_nowait(unsigned int cpu,
72				       cpu_stop_fn_t fn, void *arg,
73				       struct cpu_stop_work *work_buf)
74{
75	if (cpu == smp_processor_id()) {
76		INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
77		work_buf->fn = fn;
78		work_buf->arg = arg;
79		schedule_work(&work_buf->work);
80		return true;
81	}
82
83	return false;
84}
85
86static inline void print_stop_info(const char *log_lvl, struct task_struct *task) { }
87
88#endif	/* CONFIG_SMP */
89
90/*
91 * stop_machine "Bogolock": stop the entire machine, disable
92 * interrupts.  This is a very heavy lock, which is equivalent to
93 * grabbing every spinlock (and more).  So the "read" side to such a
94 * lock is anything which disables preemption.
95 */
96#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
97
98/**
99 * stop_machine: freeze the machine on all CPUs and run this function
100 * @fn: the function to run
101 * @data: the data ptr for the @fn()
102 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
103 *
104 * Description: This causes a thread to be scheduled on every cpu,
105 * each of which disables interrupts.  The result is that no one is
106 * holding a spinlock or inside any other preempt-disabled region when
107 * @fn() runs.
108 *
109 * This can be thought of as a very heavy write lock, equivalent to
110 * grabbing every spinlock in the kernel.
111 *
112 * Protects against CPU hotplug.
113 */
114int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
115
116/**
117 * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
118 * @fn: the function to run
119 * @data: the data ptr for the @fn()
120 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
121 *
122 * Same as above. Must be called from with in a cpus_read_lock() protected
123 * region. Avoids nested calls to cpus_read_lock().
124 */
125int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
126
127/**
128 * stop_core_cpuslocked: - stop all threads on just one core
129 * @cpu: any cpu in the targeted core
130 * @fn: the function to run
131 * @data: the data ptr for @fn()
132 *
133 * Same as above, but instead of every CPU, only the logical CPUs of a
134 * single core are affected.
135 *
136 * Context: Must be called from within a cpus_read_lock() protected region.
137 *
138 * Return: 0 if all executions of @fn returned 0, any non zero return
139 * value if any returned non zero.
140 */
141int stop_core_cpuslocked(unsigned int cpu, cpu_stop_fn_t fn, void *data);
142
143int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
144				   const struct cpumask *cpus);
145#else	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
146
147static __always_inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
148					  const struct cpumask *cpus)
149{
150	unsigned long flags;
151	int ret;
152	local_irq_save(flags);
153	ret = fn(data);
154	local_irq_restore(flags);
155	return ret;
156}
157
158static __always_inline int
159stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
160{
161	return stop_machine_cpuslocked(fn, data, cpus);
162}
163
164static __always_inline int
165stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
166			       const struct cpumask *cpus)
167{
168	return stop_machine(fn, data, cpus);
169}
170
171#endif	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
172#endif	/* _LINUX_STOP_MACHINE */
173