work_on_cpu(): rewrite it to create a kernel thread on demand

}

#ifdef CONFIG_SMP

static struct workqueue_struct *work_on_cpu_wq __read_mostly;

struct work_for_cpu {

	struct work_struct work;

	struct completion completion;

	long (*fn)(void *);

	void *arg;

	long ret;

};

static void do_work_for_cpu(struct work_struct *w)

static int do_work_for_cpu(void *_wfc)

{

	struct work_for_cpu *wfc = container_of(w, struct work_for_cpu, work);

	struct work_for_cpu *wfc = _wfc;

	wfc->ret = wfc->fn(wfc->arg);

	complete(&wfc->completion);

	return 0;

}

/**

 *

 * This will return the value @fn returns.

 * It is up to the caller to ensure that the cpu doesn't go offline.

 * The caller must not hold any locks which would prevent @fn from completing.

 */

long work_on_cpu(unsigned int cpu, long (*fn)(void *), void *arg)

{

	struct work_for_cpu wfc;

	INIT_WORK(&wfc.work, do_work_for_cpu);

	wfc.fn = fn;

	wfc.arg = arg;

	queue_work_on(cpu, work_on_cpu_wq, &wfc.work);

	flush_work(&wfc.work);

	struct task_struct *sub_thread;

	struct work_for_cpu wfc = {

		.completion = COMPLETION_INITIALIZER_ONSTACK(wfc.completion),

		.fn = fn,

		.arg = arg,

	};

	sub_thread = kthread_create(do_work_for_cpu, &wfc, "work_for_cpu");

	if (IS_ERR(sub_thread))

		return PTR_ERR(sub_thread);

	kthread_bind(sub_thread, cpu);

	wake_up_process(sub_thread);

	wait_for_completion(&wfc.completion);

	return wfc.ret;

}

EXPORT_SYMBOL_GPL(work_on_cpu);

	hotcpu_notifier(workqueue_cpu_callback, 0);

	keventd_wq = create_workqueue("events");

	BUG_ON(!keventd_wq);

#ifdef CONFIG_SMP

	work_on_cpu_wq = create_workqueue("work_on_cpu");

	BUG_ON(!work_on_cpu_wq);

#endif

}