include/linux/stop_machine.h

   1 #ifndef _LINUX_STOP_MACHINE
   2 #define _LINUX_STOP_MACHINE
   3
   4 #include <linux/cpu.h>
   5 #include <linux/cpumask.h>
   6 #include <linux/smp.h>
   7 #include <linux/list.h>
   8
   9 /*
  10  * stop_cpu[s]() is simplistic per-cpu maximum priority cpu
  11  * monopolization mechanism.  The caller can specify a non-sleeping
  12  * function to be executed on a single or multiple cpus preempting all
  13  * other processes and monopolizing those cpus until it finishes.
  14  *
  15  * Resources for this mechanism are preallocated when a cpu is brought
  16  * up and requests are guaranteed to be served as long as the target
  17  * cpus are online.
  18  */
  19 typedef int (*cpu_stop_fn_t)(void *arg);
  20
  21 #ifdef CONFIG_SMP
  22
  23 struct cpu_stop_work {
  24         struct list_head        list;           /* cpu_stopper->works */
  25         cpu_stop_fn_t           fn;
  26         void                    *arg;
  27         struct cpu_stop_done    *done;
  28 };
  29
  30 int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
  31 int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
  32 bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
  33                          struct cpu_stop_work *work_buf);
  34 int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
  35 int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
  36 void stop_machine_park(int cpu);
  37 void stop_machine_unpark(int cpu);
  38
  39 #else   /* CONFIG_SMP */
  40
  41 #include <linux/workqueue.h>
  42
  43 struct cpu_stop_work {
  44         struct work_struct      work;
  45         cpu_stop_fn_t           fn;
  46         void                    *arg;
  47 };
  48
  49 static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
  50 {
  51         int ret = -ENOENT;
  52         preempt_disable();
  53         if (cpu == smp_processor_id())
  54                 ret = fn(arg);
  55         preempt_enable();
  56         return ret;
  57 }
  58
  59 static void stop_one_cpu_nowait_workfn(struct work_struct *work)
  60 {
  61         struct cpu_stop_work *stwork =
  62                 container_of(work, struct cpu_stop_work, work);
  63         preempt_disable();
  64         stwork->fn(stwork->arg);
  65         preempt_enable();
  66 }
  67
  68 static inline bool stop_one_cpu_nowait(unsigned int cpu,
  69                                        cpu_stop_fn_t fn, void *arg,
  70                                        struct cpu_stop_work *work_buf)
  71 {
  72         if (cpu == smp_processor_id()) {
  73                 INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
  74                 work_buf->fn = fn;
  75                 work_buf->arg = arg;
  76                 schedule_work(&work_buf->work);
  77                 return true;
  78         }
  79
  80         return false;
  81 }
  82
  83 static inline int stop_cpus(const struct cpumask *cpumask,
  84                             cpu_stop_fn_t fn, void *arg)
  85 {
  86         if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
  87                 return stop_one_cpu(raw_smp_processor_id(), fn, arg);
  88         return -ENOENT;
  89 }
  90
  91 static inline int try_stop_cpus(const struct cpumask *cpumask,
  92                                 cpu_stop_fn_t fn, void *arg)
  93 {
  94         return stop_cpus(cpumask, fn, arg);
  95 }
  96
  97 #endif  /* CONFIG_SMP */
  98
  99 /*
 100  * stop_machine "Bogolock": stop the entire machine, disable
 101  * interrupts.  This is a very heavy lock, which is equivalent to
 102  * grabbing every spinlock (and more).  So the "read" side to such a
 103  * lock is anything which disables preemption.
 104  */
 105 #if defined(CONFIG_SMP) || defined(CONFIG_HOTPLUG_CPU)
 106
 107 /**
 108  * stop_machine: freeze the machine on all CPUs and run this function
 109  * @fn: the function to run
 110  * @data: the data ptr for the @fn()
 111  * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 112  *
 113  * Description: This causes a thread to be scheduled on every cpu,
 114  * each of which disables interrupts.  The result is that no one is
 115  * holding a spinlock or inside any other preempt-disabled region when
 116  * @fn() runs.
 117  *
 118  * This can be thought of as a very heavy write lock, equivalent to
 119  * grabbing every spinlock in the kernel.
 120  *
 121  * Protects against CPU hotplug.
 122  */
 123 int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 124
 125 /**
 126  * stop_machine_cpuslocked: freeze the machine on all CPUs and run this function
 127  * @fn: the function to run
 128  * @data: the data ptr for the @fn()
 129  * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 130  *
 131  * Same as above. Must be called from with in a cpus_read_lock() protected
 132  * region. Avoids nested calls to cpus_read_lock().
 133  */
 134 int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 135
 136 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 137                                    const struct cpumask *cpus);
 138 #else   /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
 139
 140 static inline int stop_machine_cpuslocked(cpu_stop_fn_t fn, void *data,
 141                                           const struct cpumask *cpus)
 142 {
 143         unsigned long flags;
 144         int ret;
 145         local_irq_save(flags);
 146         ret = fn(data);
 147         local_irq_restore(flags);
 148         return ret;
 149 }
 150
 151 static inline int stop_machine(cpu_stop_fn_t fn, void *data,
 152                                const struct cpumask *cpus)
 153 {
 154         return stop_machine_cpuslocked(fn, data, cpus);
 155 }
 156
 157 static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 158                                                  const struct cpumask *cpus)
 159 {
 160         return stop_machine(fn, data, cpus);
 161 }
 162
 163 #endif  /* CONFIG_SMP || CONFIG_HOTPLUG_CPU */
 164 #endif  /* _LINUX_STOP_MACHINE */