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 int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
32 int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
33 bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
34 struct cpu_stop_work *work_buf);
35 #ifdef CONFIG_CPU_ISOLATION_OPT
36 int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
37 #endif
38 void stop_machine_park(int cpu);
39 void stop_machine_unpark(int cpu);
40 void stop_machine_yield(const struct cpumask *cpumask);
41
42 #else /* CONFIG_SMP */
43
44 #include <linux/workqueue.h>
45
46 struct cpu_stop_work {
47 struct work_struct work;
48 cpu_stop_fn_t fn;
49 void *arg;
50 };
51
stop_one_cpu(unsigned int cpu,cpu_stop_fn_t fn,void * arg)52 static 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
stop_one_cpu_nowait_workfn(struct work_struct * work)62 static 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
stop_one_cpu_nowait(unsigned int cpu,cpu_stop_fn_t fn,void * arg,struct cpu_stop_work * work_buf)71 static 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
stop_cpus(const struct cpumask * cpumask,cpu_stop_fn_t fn,void * arg)86 static inline int stop_cpus(const struct cpumask *cpumask,
87 cpu_stop_fn_t fn, void *arg)
88 {
89 if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
90 return stop_one_cpu(raw_smp_processor_id(), fn, arg);
91 return -ENOENT;
92 }
93
94 #endif /* CONFIG_SMP */
95
96 /*
97 * stop_machine "Bogolock": stop the entire machine, disable
98 * interrupts. This is a very heavy lock, which is equivalent to
99 * grabbing every spinlock (and more). So the "read" side to such a
100 * lock is anything which disables preemption.
101 */
102 #if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
103
104 /**
105 * stop_machine: freeze the machine on all CPUs and run this function
106 * @fn: the function to run
107 * @data: the data ptr for the @fn()
108 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
109 *
110 * Description: This causes a thread to be scheduled on every cpu,
111 * each of which disables interrupts. The result is that no one is
112 * holding a spinlock or inside any other preempt-disabled region when
113 * @fn() runs.
114 *
115 * This can be thought of as a very heavy write lock, equivalent to
116 * grabbing every spinlock in the kernel.
117 *
118 * Protects against CPU hotplug.
119 */
120 int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
121
122 /**
123 * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
124 * @fn: the function to run
125 * @data: the data ptr for the @fn()
126 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
127 *
128 * Same as above. Must be called from with in a cpus_read_lock() protected
129 * region. Avoids nested calls to cpus_read_lock().
130 */
131 int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
132
133 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
134 const struct cpumask *cpus);
135 #else /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
136
stop_machine_cpuslocked(cpu_stop_fn_t fn,void * data,const struct cpumask * cpus)137 static __always_inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
138 const struct cpumask *cpus)
139 {
140 unsigned long flags;
141 int ret;
142 local_irq_save(flags);
143 ret = fn(data);
144 local_irq_restore(flags);
145 return ret;
146 }
147
148 static __always_inline int
stop_machine(cpu_stop_fn_t fn,void * data,const struct cpumask * cpus)149 stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
150 {
151 return stop_machine_cpuslocked(fn, data, cpus);
152 }
153
154 static __always_inline int
stop_machine_from_inactive_cpu(cpu_stop_fn_t fn,void * data,const struct cpumask * cpus)155 stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
156 const struct cpumask *cpus)
157 {
158 return stop_machine(fn, data, cpus);
159 }
160
161 #endif /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
162 #endif /* _LINUX_STOP_MACHINE */
163