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
  37 #else   /* CONFIG_SMP */
  38
  39 #include <linux/workqueue.h>
  40
  41 struct cpu_stop_work {
  42         struct work_struct      work;
  43         cpu_stop_fn_t           fn;
  44         void                    *arg;
  45 };
  46
  47 static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
  48 {
  49         int ret = -ENOENT;
  50         preempt_disable();
  51         if (cpu == smp_processor_id())
  52                 ret = fn(arg);
  53         preempt_enable();
  54         return ret;
  55 }
  56
  57 static void stop_one_cpu_nowait_workfn(struct work_struct *work)
  58 {
  59         struct cpu_stop_work *stwork =
  60                 container_of(work, struct cpu_stop_work, work);
  61         preempt_disable();
  62         stwork->fn(stwork->arg);
  63         preempt_enable();
  64 }
  65
  66 static inline void stop_one_cpu_nowait(unsigned int cpu,
  67                                        cpu_stop_fn_t fn, void *arg,
  68                                        struct cpu_stop_work *work_buf)
  69 {
  70         if (cpu == smp_processor_id()) {
  71                 INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
  72                 work_buf->fn = fn;
  73                 work_buf->arg = arg;
  74                 schedule_work(&work_buf->work);
  75         }
  76 }
  77
  78 static inline int stop_cpus(const struct cpumask *cpumask,
  79                             cpu_stop_fn_t fn, void *arg)
  80 {
  81         if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
  82                 return stop_one_cpu(raw_smp_processor_id(), fn, arg);
  83         return -ENOENT;
  84 }
  85
  86 static inline int try_stop_cpus(const struct cpumask *cpumask,
  87                                 cpu_stop_fn_t fn, void *arg)
  88 {
  89         return stop_cpus(cpumask, fn, arg);
  90 }
  91
  92 #endif  /* CONFIG_SMP */
  93
  94 /*
  95  * stop_machine "Bogolock": stop the entire machine, disable
  96  * interrupts.  This is a very heavy lock, which is equivalent to
  97  * grabbing every spinlock (and more).  So the "read" side to such a
  98  * lock is anything which disables preemption.
  99  */
 100 #if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)
 101
 102 /**
 103  * stop_machine: freeze the machine on all CPUs and run this function
 104  * @fn: the function to run
 105  * @data: the data ptr for the @fn()
 106  * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 107  *
 108  * Description: This causes a thread to be scheduled on every cpu,
 109  * each of which disables interrupts.  The result is that no one is
 110  * holding a spinlock or inside any other preempt-disabled region when
 111  * @fn() runs.
 112  *
 113  * This can be thought of as a very heavy write lock, equivalent to
 114  * grabbing every spinlock in the kernel. */
 115 int stop_machine(cpu_stop_fn_t fn, void *data, const struct cpumask *cpus);
 116
 117 int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 118                                    const struct cpumask *cpus);
 119 #else    /* CONFIG_STOP_MACHINE && CONFIG_SMP */
 120
 121 static inline int stop_machine(cpu_stop_fn_t fn, void *data,
 122                                  const struct cpumask *cpus)
 123 {
 124         unsigned long flags;
 125         int ret;
 126         local_irq_save(flags);
 127         ret = fn(data);
 128         local_irq_restore(flags);
 129         return ret;
 130 }
 131
 132 static inline int stop_machine_from_inactive_cpu(cpu_stop_fn_t fn, void *data,
 133                                                  const struct cpumask *cpus)
 134 {
 135         return stop_machine(fn, data, cpus);
 136 }
 137
 138 #endif  /* CONFIG_STOP_MACHINE && CONFIG_SMP */
 139 #endif  /* _LINUX_STOP_MACHINE */