Re: [patch 04/13] syslets: core code

Davide Libenzi
2007-02-23T23:08:58Z

On Wed, 21 Feb 2007, Ingo Molnar wrote:

> +asmlinkage long
> +sys_threadlet_on(unsigned long restore_stack,
> + unsigned long restore_eip,
> + struct async_head_user __user *ahu)
> +{
> + struct task_struct *t = current;
> + struct async_head *ah = t->ah;
> + struct async_thread *at = &t->__at;
> + long ret;
> +
> + /*
> + * Do not allow recursive calls of sys_threadlet_on():
> + */
> + if (t->async_ready || t->at)
> + return -EINVAL;
> +
> + if (unlikely(!ah)) {
> + ret = init_head(ah, t, ahu);
> + if (ret)
> + return ret;
> + ah = t->ah;
> + }
> +
> + if (unlikely(list_empty(&ah->ready_async_threads))) {
> + ret = refill_cachemiss_pool(ah, t, ahu);
> + if (ret)
> + return ret;
> + }
> +
> + t->async_ready = at;
> + ah->restore_stack = restore_stack;
> + ah->restore_eip = restore_eip;
> +
> + ah->ahu = ahu;
> +
> + return 0;
> +}
> +
> +asmlinkage long sys_threadlet_off(void)
> +{
> + struct task_struct *t = current;
> + struct async_head *ah = t->ah;
> +
> + /*
> + * Are we still executing as head?
> + */
> + if (ah) {
> + t->async_ready = NULL;
> +
> + return 1;
> + }
> +
> + /*
> + * We got turned into a cachemiss thread,
> + * return to user-space, which can do
> + * the notification, etc:
> + */
> + return 0;
> +}

If we have a new syscall that does the exec, we can save the two on/off
calls. Also, the complete_thread() thingy can be done automatically from
inside the kernel upon function return, by hence making the threadlet
function look like a normal thread function:

long thfn(void *) {

...
return error;
}

No?

- Davide