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1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_STOP_MACHINE
3#define _LINUX_STOP_MACHINE
4
5#include <linux/bug.h>
6#include <linux/cpu.h>
7#include <linux/cpumask_types.h>
8#include <linux/smp.h>
9#include <linux/list.h>
10
11/*
12 * stop_cpu[s]() is simplistic per-cpu maximum priority cpu
13 * monopolization mechanism. The caller can specify a non-sleeping
14 * function to be executed on a single or multiple cpus preempting all
15 * other processes and monopolizing those cpus until it finishes.
16 *
17 * Resources for this mechanism are preallocated when a cpu is brought
18 * up and requests are guaranteed to be served as long as the target
19 * cpus are online.
20 */
21typedef int (*cpu_stop_fn_t)(void *arg);
22
23#ifdef CONFIG_SMP
24
25struct cpu_stop_work {
26 struct list_head list; /* cpu_stopper->works */
27 cpu_stop_fn_t fn;
28 unsigned long caller;
29 void *arg;
30 struct cpu_stop_done *done;
31};
32
33int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
34int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
35void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
36 struct cpu_stop_work *work_buf);
37void stop_machine_park(int cpu);
38void stop_machine_unpark(int cpu);
39void stop_machine_yield(const struct cpumask *cpumask);
40
41extern void print_stop_info(const char *log_lvl, struct task_struct *task);
42
43#else /* CONFIG_SMP */
44
45#include <linux/workqueue.h>
46
47struct cpu_stop_work {
48 struct work_struct work;
49 cpu_stop_fn_t fn;
50 void *arg;
51};
52
53static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
54{
55 int ret = -ENOENT;
56 preempt_disable();
57 if (cpu == smp_processor_id())
58 ret = fn(arg);
59 preempt_enable();
60 return ret;
61}
62
63static void stop_one_cpu_nowait_workfn(struct work_struct *work)
64{
65 struct cpu_stop_work *stwork =
66 container_of(work, struct cpu_stop_work, work);
67 preempt_disable();
68 stwork->fn(stwork->arg);
69 preempt_enable();
70}
71
72static inline void stop_one_cpu_nowait(unsigned int cpu,
73 cpu_stop_fn_t fn, void *arg,
74 struct cpu_stop_work *work_buf)
75{
76 if (WARN_ON_ONCE(cpu != smp_processor_id()))
77 return;
78
79 INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
80 work_buf->fn = fn;
81 work_buf->arg = arg;
82 schedule_work(&work_buf->work);
83}
84
85static inline void print_stop_info(const char *log_lvl, struct task_struct *task) { }
86
87#endif /* CONFIG_SMP */
88
89/*
90 * stop_machine "Bogolock": stop the entire machine, disable interrupts.
91 * This is a very heavy lock, which is equivalent to grabbing every raw
92 * spinlock (and more). So the "read" side to such a lock is anything
93 * which disables preemption.
94 */
95#if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
96
97/**
98 * stop_machine: freeze the machine on all CPUs and run this function
99 * @fn: the function to run
100 * @data: the data ptr to pass to @fn()
101 * @cpus: the cpus to run @fn() on (NULL = one unspecified online CPU)
102 *
103 * Description: This causes a thread to be scheduled on every CPU, which
104 * will run with interrupts disabled. Each CPU specified by @cpus will
105 * run @fn. While @fn is executing, there will no other CPUs holding
106 * a raw spinlock or running within any other type of preempt-disabled
107 * region of code.
108 *
109 * When @cpus specifies only a single CPU, this can be thought of as
110 * a reader-writer lock where readers disable preemption (for example,
111 * by holding a raw spinlock) and where the insanely heavy writers run
112 * @fn while also preventing any other CPU from doing any useful work.
113 * These writers can also be thought of as having implicitly grabbed every
114 * raw spinlock in the kernel.
115 *
116 * When @fn is a no-op, this can be thought of as an RCU implementation
117 * where readers again disable preemption and writers use stop_machine()
118 * in place of synchronize_rcu(), albeit with orders of magnitude more
119 * disruption than even that of synchronize_rcu_expedited().
120 *
121 * Although only one stop_machine() operation can proceed at a time,
122 * the possibility of blocking in cpus_read_lock() means that the caller
123 * cannot usefully rely on this serialization.
124 *
125 * Return: 0 if all invocations of @fn return zero. Otherwise, the
126 * value returned by an arbitrarily chosen member of the set of calls to
127 * @fn that returned non-zero.
128 */
129int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
130
131/**
132 * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
133 * @fn: the function to run
134 * @data: the data ptr to pass to @fn()
135 * @cpus: the cpus to run @fn() on (NULL = one unspecified online CPU)
136 *
137 * Same as above. Avoids nested calls to cpus_read_lock().
138 *
139 * Context: Must be called from within a cpus_read_lock() protected region.
140 */
141int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
142
143/**
144 * stop_core_cpuslocked: - stop all threads on just one core
145 * @cpu: any cpu in the targeted core
146 * @fn: the function to run on each CPU in the core containing @cpu
147 * @data: the data ptr to pass to @fn()
148 *
149 * Same as above, but instead of every CPU, only the logical CPUs of the
150 * single core containing @cpu are affected.
151 *
152 * Context: Must be called from within a cpus_read_lock() protected region.
153 *
154 * Return: 0 if all invocations of @fn return zero. Otherwise, the
155 * value returned by an arbitrarily chosen member of the set of calls to
156 * @fn that returned non-zero.
157 */
158int stop_core_cpuslocked(unsigned int cpu, cpu_stop_fn_t fn, void *data);
159
160int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
161 const struct cpumask *cpus);
162#else /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
163
164static __always_inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
165 const struct cpumask *cpus)
166{
167 unsigned long flags;
168 int ret;
169 local_irq_save(flags);
170 ret = fn(data);
171 local_irq_restore(flags);
172 return ret;
173}
174
175static __always_inline int
176stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
177{
178 return stop_machine_cpuslocked(fn, data, cpus);
179}
180
181static __always_inline int
182stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
183 const struct cpumask *cpus)
184{
185 return stop_machine(fn, data, cpus);
186}
187
188#endif /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
189#endif /* _LINUX_STOP_MACHINE */