Question about the usage of kernel_thread

[Yan Zheng <yanzheng@21cn.com>]

Hi.

In LKD2, Robert say:
Linux delegates several tasks to kernel threads, most notably the pdflush task and the ksoftirqd task. These threads are created on system boot by other kernel threads. Indeed, a kernel thread can be created only by another kernel thread. 


But I found that kernel_thread(...) are used wildly like:

#include <linux/kernel.h>
#include <linux/module.h>

static int noop(void *dummy)
{
        printk("current->mm = %p\n", current->mm);
        return 0;
}

static int test_init(void)
{
        kernel_thread(noop, NULL, CLONE_KERNEL | SIGCHLD);
        return 0;
}

static void test_exit(void) {}
module_init(test_init);
module_exit(test_exit); 


In this circumstances, The thread created by kernel_thread has "current->mm != NULL".

My question is:
The new thread is truely kernel thread ? The usage of kernel_thread(...) like this is correct?

Thanks advance.
Best Regards