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 */
20 typedef int (*cpu_stop_fn_t)(void *arg);
21
22 #ifdef CONFIG_SMP
23
24 struct 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
31 /*
32 * Structure to determine completion condition and record errors. May
33 * be shared by works on different cpus.
34 */
35 struct cpu_stop_done {
36 atomic_t nr_todo; /* nr left to execute */
37 int ret; /* collected return value */
38 struct completion completion; /* fired if nr_todo reaches 0 */
39 };
40
41 int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
42 int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
43 bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
44 struct cpu_stop_work *work_buf);
45 void stop_machine_park(int cpu);
46 void stop_machine_unpark(int cpu);
47 void stop_machine_yield(const struct cpumask *cpumask);
48 int stop_one_cpu_async(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
49 struct cpu_stop_work *work_buf,
50 struct cpu_stop_done *done);
51 void cpu_stop_work_wait(struct cpu_stop_work *work_buf);
52
53 #else /* CONFIG_SMP */
54
55 #include <linux/workqueue.h>
56
57 struct cpu_stop_work {
58 struct work_struct work;
59 cpu_stop_fn_t fn;
60 void *arg;
61 };
62
stop_one_cpu(unsigned int cpu,cpu_stop_fn_t fn,void * arg)63 static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
64 {
65 int ret = -ENOENT;
66 preempt_disable();
67 if (cpu == smp_processor_id())
68 ret = fn(arg);
69 preempt_enable();
70 return ret;
71 }
72
stop_one_cpu_nowait_workfn(struct work_struct * work)73 static void stop_one_cpu_nowait_workfn(struct work_struct *work)
74 {
75 struct cpu_stop_work *stwork =
76 container_of(work, struct cpu_stop_work, work);
77 preempt_disable();
78 stwork->fn(stwork->arg);
79 preempt_enable();
80 }
81
stop_one_cpu_nowait(unsigned int cpu,cpu_stop_fn_t fn,void * arg,struct cpu_stop_work * work_buf)82 static inline bool stop_one_cpu_nowait(unsigned int cpu,
83 cpu_stop_fn_t fn, void *arg,
84 struct cpu_stop_work *work_buf)
85 {
86 if (cpu == smp_processor_id()) {
87 INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
88 work_buf->fn = fn;
89 work_buf->arg = arg;
90 schedule_work(&work_buf->work);
91 return true;
92 }
93
94 return false;
95 }
96
97 #endif /* CONFIG_SMP */
98
99 /*
100 * stop_machine "Bogolock": stop the entire machine, disable
101 * interrupts. This is a very heavy lock, which is equivalent to
102 * grabbing every spinlock (and more). So the "read" side to such a
103 * lock is anything which disables preemption.
104 */
105 #if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
106
107 /**
108 * stop_machine: freeze the machine on all CPUs and run this function
109 * @fn: the function to run
110 * @data: the data ptr for the @fn()
111 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
112 *
113 * Description: This causes a thread to be scheduled on every cpu,
114 * each of which disables interrupts. The result is that no one is
115 * holding a spinlock or inside any other preempt-disabled region when
116 * @fn() runs.
117 *
118 * This can be thought of as a very heavy write lock, equivalent to
119 * grabbing every spinlock in the kernel.
120 *
121 * Protects against CPU hotplug.
122 */
123 int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
124
125 /**
126 * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
127 * @fn: the function to run
128 * @data: the data ptr for the @fn()
129 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
130 *
131 * Same as above. Must be called from with in a cpus_read_lock() protected
132 * region. Avoids nested calls to cpus_read_lock().
133 */
134 int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
135
136 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
137 const struct cpumask *cpus);
138 #else /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
139
stop_machine_cpuslocked(cpu_stop_fn_t fn,void * data,const struct cpumask * cpus)140 static __always_inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
141 const struct cpumask *cpus)
142 {
143 unsigned long flags;
144 int ret;
145 local_irq_save(flags);
146 ret = fn(data);
147 local_irq_restore(flags);
148 return ret;
149 }
150
151 static __always_inline int
stop_machine(cpu_stop_fn_t fn,void * data,const struct cpumask * cpus)152 stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
153 {
154 return stop_machine_cpuslocked(fn, data, cpus);
155 }
156
157 static __always_inline int
stop_machine_from_inactive_cpu(cpu_stop_fn_t fn,void * data,const struct cpumask * cpus)158 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