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