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 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 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 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 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 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 */ 141 142 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 } 152 153 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 } 158 159 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