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