_FS | CLONE_FILES | SIGCHLD);
if (pid < 0) {
create->result = ERR_PTR(pid);
} else {
wait_for_completion(&create->started);
read_lock(&tasklist_lock);
create->result = find_task_by_pid(pid);
read_unlock(&tasklist_lock);
}
complete(&create->done);
}
再看看kernel_thread（）函数最后调用到了哪里：
/*
* Create a kernel thread.
*/
pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags)
{
struct pt_regs regs;
long pid;
memset(®s, 0, sizeof(regs));
regs.ARM_r1 = (unsigned long)arg;
regs.ARM_r2 = (unsigned long)fn;
regs.ARM_r3 = (unsigned long)do_exit;
regs.ARM_pc = (unsigned long)kernel_thread_helper;
regs.ARM_cpsr = SVC_MODE;
pid = do_fork(flags|CLONE_VM|CLONE_UNTRACED, 0, ®s, 0, NULL, NULL);
MARK(kernel_thread_create, "%ld %p", pid, fn);
return pid;
}
EXPORT_SYMBOL(kernel_thread);
好，最后我们看到了线程通过申请进程的pid号来被创建，关键是我们要知道如何使用这个宏函数，也就是如何应用它。要注意的是它调用了创建线程函数，同时也激活了线程。所以代码中调用了它的话就隐含着已经启动一个线程。