1#ifndef _LINUX_STOP_MACHINE
2#define _LINUX_STOP_MACHINE
3
4#include <linux/cpu.h>
5#include <linux/cpumask.h>
6#include <linux/smp.h>
7#include <linux/list.h>
8
9/*
10 * stop_cpu[s]() is simplistic per-cpu maximum priority cpu
11 * monopolization mechanism.  The caller can specify a non-sleeping
12 * function to be executed on a single or multiple cpus preempting all
13 * other processes and monopolizing those cpus until it finishes.
14 *
15 * Resources for this mechanism are preallocated when a cpu is brought
16 * up and requests are guaranteed to be served as long as the target
17 * cpus are online.
18 */
19typedef int (*cpu_stop_fn_t)(void *arg);
20
21#ifdef CONFIG_SMP
22
23struct cpu_stop_work {
24	struct list_head	list;		/* cpu_stopper->works */
25	cpu_stop_fn_t		fn;
26	void			*arg;
27	struct cpu_stop_done	*done;
28};
29
30int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
31int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
32void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
33			 struct cpu_stop_work *work_buf);
34int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
35int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
36
37#else	/* CONFIG_SMP */
38
39#include <linux/workqueue.h>
40
41struct cpu_stop_work {
42	struct work_struct	work;
43	cpu_stop_fn_t		fn;
44	void			*arg;
45};
46
47static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
48{
49	int ret = -ENOENT;
50	preempt_disable();
51	if (cpu == smp_processor_id())
52		ret = fn(arg);
53	preempt_enable();
54	return ret;
55}
56
57static void stop_one_cpu_nowait_workfn(struct work_struct *work)
58{
59	struct cpu_stop_work *stwork =
60		container_of(work, struct cpu_stop_work, work);
61	preempt_disable();
62	stwork->fn(stwork->arg);
63	preempt_enable();
64}
65
66static inline void stop_one_cpu_nowait(unsigned int cpu,
67				       cpu_stop_fn_t fn, void *arg,
68				       struct cpu_stop_work *work_buf)
69{
70	if (cpu == smp_processor_id()) {
71		INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
72		work_buf->fn = fn;
73		work_buf->arg = arg;
74		schedule_work(&work_buf->work);
75	}
76}
77
78static inline int stop_cpus(const struct cpumask *cpumask,
79			    cpu_stop_fn_t fn, void *arg)
80{
81	if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
82		return stop_one_cpu(raw_smp_processor_id(), fn, arg);
83	return -ENOENT;
84}
85
86static inline int try_stop_cpus(const struct cpumask *cpumask,
87				cpu_stop_fn_t fn, void *arg)
88{
89	return stop_cpus(cpumask, fn, arg);
90}
91
92#endif	/* CONFIG_SMP */
93
94/*
95 * stop_machine "Bogolock": stop the entire machine, disable
96 * interrupts.  This is a very heavy lock, which is equivalent to
97 * grabbing every spinlock (and more).  So the "read" side to such a
98 * lock is anything which disables preemption.
99 */
100#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
101
102/**
103 * stop_machine: freeze the machine on all CPUs and run this function
104 * @fn: the function to run
105 * @data: the data ptr for the @fn()
106 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
107 *
108 * Description: This causes a thread to be scheduled on every cpu,
109 * each of which disables interrupts.  The result is that no one is
110 * holding a spinlock or inside any other preempt-disabled region when
111 * @fn() runs.
112 *
113 * This can be thought of as a very heavy write lock, equivalent to
114 * grabbing every spinlock in the kernel. */
115int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);
116
117/**
118 * __stop_machine: freeze the machine on all CPUs and run this function
119 * @fn: the function to run
120 * @data: the data ptr for the @fn
121 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
122 *
123 * Description: This is a special version of the above, which assumes cpus
124 * won't come or go while it's being called.  Used by hotplug cpu.
125 */
126int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);
127
128int stop_machine_from_inactive_cpu(int (*fn)(void *), void *data,
129				   const struct cpumask *cpus);
130
131#else	 /* CONFIG_STOP_MACHINE && CONFIG_SMP */
132
133static inline int __stop_machine(int (*fn)(void *), void *data,
134				 const struct cpumask *cpus)
135{
136	unsigned long flags;
137	int ret;
138	local_irq_save(flags);
139	ret = fn(data);
140	local_irq_restore(flags);
141	return ret;
142}
143
144static inline int stop_machine(int (*fn)(void *), void *data,
145			       const struct cpumask *cpus)
146{
147	return __stop_machine(fn, data, cpus);
148}
149
150static inline int stop_machine_from_inactive_cpu(int (*fn)(void *), void *data,
151						 const struct cpumask *cpus)
152{
153	return __stop_machine(fn, data, cpus);
154}
155
156#endif	/* CONFIG_STOP_MACHINE && CONFIG_SMP */
157#endif	/* _LINUX_STOP_MACHINE */
158