stop_machine.h

Go to the documentation of this file.

#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);
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)

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

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 */