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