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 void 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 void 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         }
  78 }
  79
  80 static inline int stop_cpus(const struct cpumask *cpumask,
  81                             cpu_stop_fn_t fn, void *arg)
  82 {
  83         if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
  84                 return stop_one_cpu(raw_smp_processor_id(), fn, arg);
  85         return -ENOENT;
  86 }
  87
  88 static inline int try_stop_cpus(const struct cpumask *cpumask,
  89                                 cpu_stop_fn_t fn, void *arg)
  90 {
  91         return stop_cpus(cpumask, fn, arg);
  92 }
  93
  94 #endif  /* CONFIG_SMP */
  95
  96 /*
  97  * stop_machine "Bogolock": stop the entire machine, disable
  98  * interrupts.  This is a very heavy lock, which is equivalent to
  99  * grabbing every spinlock (and more).  So the "read" side to such a
 100  * lock is anything which disables preemption.
 101  */
 102 #if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
 103
 104 /**
 105  * stop_machine: freeze the machine on all CPUs and run this function
 106  * @fn: the function to run
 107  * @data: the data ptr for the @fn()
 108  * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 109  *
 110  * Description: This causes a thread to be scheduled on every cpu,
 111  * each of which disables interrupts.  The result is that no one is
 112  * holding a spinlock or inside any other preempt-disabled region when
 113  * @fn() runs.
 114  *
 115  * This can be thought of as a very heavy write lock, equivalent to
 116  * grabbing every spinlock in the kernel. */
 117 int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 118
 119 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 120                                    const struct cpumask *cpus);
 121 #else    /* CONFIG_STOP_MACHINE && CONFIG_SMP */
 122
 123 static inline int stop_machine(cpu_stop_fn_t fn, void *data,
 124                                  const struct cpumask *cpus)
 125 {
 126         unsigned long flags;
 127         int ret;
 128         local_irq_save(flags);
 129         ret = fn(data);
 130         local_irq_restore(flags);
 131         return ret;
 132 }
 133
 134 static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 135                                                  const struct cpumask *cpus)
 136 {
 137         return stop_machine(fn, data, cpus);
 138 }
 139
 140 #endif  /* CONFIG_STOP_MACHINE && CONFIG_SMP */
 141 #endif  /* _LINUX_STOP_MACHINE */