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         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 */