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 	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 
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 
print_stop_info(const char * log_lvl,struct task_struct * task)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 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
128 				   const struct cpumask *cpus);
129 #else	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
130 
stop_machine_cpuslocked(cpu_stop_fn_t fn,void * data,const struct cpumask * cpus)131 static __always_inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
132 					  const struct cpumask *cpus)
133 {
134 	unsigned long flags;
135 	int ret;
136 	local_irq_save(flags);
137 	ret = fn(data);
138 	local_irq_restore(flags);
139 	return ret;
140 }
141 
142 static __always_inline int
stop_machine(cpu_stop_fn_t fn,void * data,const struct cpumask * cpus)143 stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus)
144 {
145 	return stop_machine_cpuslocked(fn, data, cpus);
146 }
147 
148 static __always_inline int
stop_machine_from_inactive_cpu(cpu_stop_fn_t fn,void * data,const struct cpumask * cpus)149 stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
150 			       const struct cpumask *cpus)
151 {
152 	return stop_machine(fn, data, cpus);
153 }
154 
155 #endif	/* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
156 #endif	/* _LINUX_STOP_MACHINE */
157