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_types.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 unsigned long caller;
28 void *arg;
29 struct cpu_stop_done *done;
30 };
31
32 int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
33 int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
34 bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
35 struct cpu_stop_work *work_buf);
36 void stop_machine_park(int cpu);
37 void stop_machine_unpark(int cpu);
38 void stop_machine_yield(const struct cpumask *cpumask);
39
40 extern void print_stop_info(const char *log_lvl, struct task_struct *task);
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
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
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
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
86 static inline void print_stop_info(const char *log_lvl, struct task_struct *task) { }
87
88 #endif /* CONFIG_SMP */
89
90 /*
91 * stop_machine "Bogolock": stop the entire machine, disable
92 * interrupts. This is a very heavy lock, which is equivalent to
93 * grabbing every spinlock (and more). So the "read" side to such a
94 * lock is anything which disables preemption.
95 */
96 #if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
97
98 /**
99 * stop_machine: freeze the machine on all CPUs and run this function
100 * @fn: the function to run
101 * @data: the data ptr for the @fn()
102 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
103 *
104 * Description: This causes a thread to be scheduled on every cpu,
105 * each of which disables interrupts. The result is that no one is
106 * holding a spinlock or inside any other preempt-disabled region when
107 * @fn() runs.
108 *
109 * This can be thought of as a very heavy write lock, equivalent to
110 * grabbing every spinlock in the kernel.
111 *
112 * Protects against CPU hotplug.
113 */
114 int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
115
116 /**
117 * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
118 * @fn: the function to run
119 * @data: the data ptr for the @fn()
120 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
121 *
122 * Same as above. Must be called from with in a cpus_read_lock() protected
123 * region. Avoids nested calls to cpus_read_lock().
124 */
125 int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
126
127 /**
128 * stop_core_cpuslocked: - stop all threads on just one core
129 * @cpu: any cpu in the targeted core
130 * @fn: the function to run
131 * @data: the data ptr for @fn()
132 *
133 * Same as above, but instead of every CPU, only the logical CPUs of a
134 * single core are affected.
135 *
136 * Context: Must be called from within a cpus_read_lock() protected region.
137 *
138 * Return: 0 if all executions of @fn returned 0, any non zero return
139 * value if any returned non zero.
140 */
141 int stop_core_cpuslocked(unsigned int cpu, cpu_stop_fn_t fn, void *data);
142
143 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
144 const struct cpumask *cpus);
145 #else /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
146
147 static __always_inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
148 const struct cpumask *cpus)
149 {
150 unsigned long flags;
151 int ret;
152 local_irq_save(flags);
153 ret = fn(data);
154 local_irq_restore(flags);
155 return ret;
156 }
157
158 static __always_inline int
159 stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
160 {
161 return stop_machine_cpuslocked(fn, data, cpus);
162 }
163
164 static __always_inline int
165 stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
166 const struct cpumask *cpus)
167 {
168 return stop_machine(fn, data, cpus);
169 }
170
171 #endif /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
172 #endif /* _LINUX_STOP_MACHINE */
173
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