root/include/linux/stop_machine.h

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
7. stop_machine
8. stop_machine_from_inactive_cpu

#ifndef _LINUX_STOP_MACHINE
#define _LINUX_STOP_MACHINE

#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/smp.h>
#include <linux/list.h>

/*
 * stop_cpu[s]() is simplistic per-cpu maximum priority cpu
 * monopolization mechanism.  The caller can specify a non-sleeping
 * function to be executed on a single or multiple cpus preempting all
 * other processes and monopolizing those cpus until it finishes.
 *
 * Resources for this mechanism are preallocated when a cpu is brought
 * up and requests are guaranteed to be served as long as the target
 * cpus are online.
 */
typedef int (*cpu_stop_fn_t)(void *arg);

#ifdef CONFIG_SMP

struct cpu_stop_work {
        struct list_head        list;           /* cpu_stopper->works */
        cpu_stop_fn_t           fn;
        void                    *arg;
        struct cpu_stop_done    *done;
};

int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
                         struct cpu_stop_work *work_buf);
int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);

#else   /* CONFIG_SMP */

#include <linux/workqueue.h>

struct cpu_stop_work {
        struct work_struct      work;
        cpu_stop_fn_t           fn;
        void                    *arg;
};

static inline int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
{
        int ret = -ENOENT;
        preempt_disable();
        if (cpu == smp_processor_id())
                ret = fn(arg);
        preempt_enable();
        return ret;
}

static void stop_one_cpu_nowait_workfn(struct work_struct *work)
{
        struct cpu_stop_work *stwork =
                container_of(work, struct cpu_stop_work, work);
        preempt_disable();
        stwork->fn(stwork->arg);
        preempt_enable();
}

static inline void stop_one_cpu_nowait(unsigned int cpu,
                                       cpu_stop_fn_t fn, void *arg,
                                       struct cpu_stop_work *work_buf)
{
        if (cpu == smp_processor_id()) {
                INIT_WORK(&work_buf->work, stop_one_cpu_nowait_workfn);
                work_buf->fn = fn;
                work_buf->arg = arg;
                schedule_work(&work_buf->work);
        }
}

static inline int stop_cpus(const struct cpumask *cpumask,
                            cpu_stop_fn_t fn, void *arg)
{
        if (cpumask_test_cpu(raw_smp_processor_id(), cpumask))
                return stop_one_cpu(raw_smp_processor_id(), fn, arg);
        return -ENOENT;
}

static inline int try_stop_cpus(const struct cpumask *cpumask,
                                cpu_stop_fn_t fn, void *arg)
{
        return stop_cpus(cpumask, fn, arg);
}

#endif  /* CONFIG_SMP */

/*
 * stop_machine "Bogolock": stop the entire machine, disable
 * interrupts.  This is a very heavy lock, which is equivalent to
 * grabbing every spinlock (and more).  So the "read" side to such a
 * lock is anything which disables preemption.
 */
#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)

/**
 * stop_machine: freeze the machine on all CPUs and run this function
 * @fn: the function to run
 * @data: the data ptr for the @fn()
 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 *
 * Description: This causes a thread to be scheduled on every cpu,
 * each of which disables interrupts.  The result is that no one is
 * holding a spinlock or inside any other preempt-disabled region when
 * @fn() runs.
 *
 * This can be thought of as a very heavy write lock, equivalent to
 * grabbing every spinlock in the kernel. */
int stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);

/**
 * __stop_machine: freeze the machine on all CPUs and run this function
 * @fn: the function to run
 * @data: the data ptr for the @fn
 * @cpus: the cpus to run the @fn() on (NULL = any online cpu)
 *
 * Description: This is a special version of the above, which assumes cpus
 * won't come or go while it's being called.  Used by hotplug cpu.
 */
int __stop_machine(int (*fn)(void *), void *data, const struct cpumask *cpus);

int stop_machine_from_inactive_cpu(int (*fn)(void *), void *data,
                                   const struct cpumask *cpus);

#else    /* CONFIG_STOP_MACHINE && CONFIG_SMP */

static inline int __stop_machine(int (*fn)(void *), void *data,
                                 const struct cpumask *cpus)
{
        unsigned long flags;
        int ret;
        local_irq_save(flags);
        ret = fn(data);
        local_irq_restore(flags);
        return ret;
}

static inline int stop_machine(int (*fn)(void *), void *data,
                               const struct cpumask *cpus)
{
        return __stop_machine(fn, data, cpus);
}

static inline int stop_machine_from_inactive_cpu(int (*fn)(void *), void *data,
                                                 const struct cpumask *cpus)
{
        return __stop_machine(fn, data, cpus);
}

#endif  /* CONFIG_STOP_MACHINE && CONFIG_SMP */
#endif  /* _LINUX_STOP_MACHINE */