Re: [PATCH 0/1] kthreads: simplify !kthreadd_task logic, kill kthreadd_task_init_done

[Oleg Nesterov <oleg@redhat.com>]

On 09/19, Wu Fei wrote:
>
> On Fri, Sep 04, 2009 at 09:37:49AM +0200, Ingo Molnar wrote:
> >
> > Lets delay this until i can debug it more fully.
> >
> CONFIG_PREEMPT_VOLUNTARY looks like the key of this problem,
> might_resched becomes _cond_resched, and since d86ee480 changes
> it not to check SYSTEM_RUNNING,

... and should_resched() is true under preempt_disable()

> --- a/init/main.c
> +++ b/init/main.c
> @@ -452,10 +452,10 @@ static noinline void __init_refok rest_init(void)
>  	int pid;
>
>  	rcu_scheduler_starting();
> -	kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
> -	numa_default_policy();
>  	pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
>  	kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
> +	kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);

We can't do this. kernel_init() should run with ->pid == 1, we are
going to exec /sbin/init.

Oleg.