include/linux/stop_machine.h

   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
  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 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
 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
 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
 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 */