long _do_fork(struct kernel_clone_args *args)
{
        u64 clone_flags = args->flags;
        struct completion vfork;
        struct pid *pid;
        struct task_struct *p;
        int trace = 0;
        long nr;

        /*
         * Determine whether and which event to report to ptracer.  When
         * called from kernel_thread or CLONE_UNTRACED is explicitly
         * requested, no event is reported; otherwise, report if the event
         * for the type of forking is enabled.
         */
        if (!(clone_flags & CLONE_UNTRACED)) {
                if (clone_flags & CLONE_VFORK)
                        trace = PTRACE_EVENT_VFORK;
                else if (args->exit_signal != SIGCHLD)
                        trace = PTRACE_EVENT_CLONE;
                else
                        trace = PTRACE_EVENT_FORK;

                if (likely(!ptrace_event_enabled(current, trace)))
                        trace = 0;
        }

        p = copy_process(NULL, trace, NUMA_NO_NODE, args);
        add_latent_entropy();

        if (IS_ERR(p))
                return PTR_ERR(p);

        /*
         * Do this prior waking up the new thread - the thread pointer
         * might get invalid after that point, if the thread exits quickly.
         */
        trace_sched_process_fork(current, p);

        pid = get_task_pid(p, PIDTYPE_PID);
        nr = pid_vnr(pid);

        if (clone_flags & CLONE_PARENT_SETTID)
                put_user(nr, args->parent_tid);

        if (clone_flags & CLONE_VFORK) {
                p->vfork_done = &vfork;
                init_completion(&vfork);
                get_task_struct(p);
        }

        wake_up_new_task(p);

        /* forking complete and child started to run, tell ptracer */
        if (unlikely(trace))
                ptrace_event_pid(trace, pid);

        if (clone_flags & CLONE_VFORK) { 
            if (!wait_for_vfork_done(p, &vfork))
                        ptrace_event_pid(PTRACE_EVENT_VFORK_DONE, pid);
        }

        put_pid(pid);
        return nr;
}