include/linux/stop_machine.h

#ifndef _LINUX_STOP_MACHINE
#define _LINUX_STOP_MACHINE

#include <linux/cpu.h>
#include <linux/cpumask.h>
#include <linux/list.h>
#include <asm/system.h>

#if defined(CONFIG_STOP_MACHINE) && defined(CONFIG_SMP)

/*
 * 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);

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);

/*
 * 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 preeempt.
 */

/**
 * 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 noone 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);

/**
 * stop_machine_create: create all stop_machine threads
 *
 * Description: This causes all stop_machine threads to be created before
 * stop_machine actually gets called. This can be used by subsystems that
 * need a non failing stop_machine infrastructure.
 */
int stop_machine_create(void);

/**
 * stop_machine_destroy: destroy all stop_machine threads
 *
 * Description: This causes all stop_machine threads which were created with
 * stop_machine_create to be destroyed again.
 */
void stop_machine_destroy(void);

#else

static inline int stop_machine(int (*fn)(void *), void *data,
			       const struct cpumask *cpus)
{
	int ret;
	local_irq_disable();
	ret = fn(data);
	local_irq_enable();
	return ret;
}

static inline int stop_machine_create(void) { return 0; }
static inline void stop_machine_destroy(void) { }

#endif /* CONFIG_SMP */
#endif /* _LINUX_STOP_MACHINE */