Re: [patch 02/12] futex: Move futex exit handling into futex code

[Peter Zijlstra]

On Wed, Nov 06, 2019 at 10:55:36PM +0100, Thomas Gleixner wrote:

> -#ifdef CONFIG_FUTEX
> -	if (unlikely(tsk->robust_list)) {
> -		exit_robust_list(tsk);
> -		tsk->robust_list = NULL;
> -	}
> -#ifdef CONFIG_COMPAT
> -	if (unlikely(tsk->compat_robust_list)) {
> -		compat_exit_robust_list(tsk);
> -		tsk->compat_robust_list = NULL;
> -	}
> -#endif
> -	if (unlikely(!list_empty(&tsk->pi_state_list)))
> -		exit_pi_state_list(tsk);
> -#endif

> +void futex_mm_release(struct task_struct *tsk)
> +{
> +	if (unlikely(tsk->robust_list)) {
> +		exit_robust_list(tsk);
> +		tsk->robust_list = NULL;
> +	}
> +
> +	if (IS_ENABLED(CONFIG_COMPAT)) {
> +		if (unlikely(tsk->compat_robust_list)) {
> +			compat_exit_robust_list(tsk);
> +			tsk->compat_robust_list = NULL;
> +		}
> +	}

I suppose it is this substitution that causes the compile error mingo
found. The problem with IS_ENABLED() is that the whole block still needs
to compile (before it can be thrown out), and in this case
tsk->compat_robust_list doesn't exist.

> +
> +	if (unlikely(!list_empty(&tsk->pi_state_list)))
> +		exit_pi_state_list(tsk);
> +}