root/include/linux/stop_machine.h

INCLUDED FROM

DEFINITIONS

1. stop_one_cpu
2. stop_one_cpu_nowait_workfn
3. stop_one_cpu_nowait
4. stop_cpus
5. try_stop_cpus
6. stop_machine_cpuslocked
7. stop_machine
8. stop_machine_from_inactive_cpu

   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 */