Re: [PATCHv2] efi/unaccepted: Fix soft lockups caused by parallel memory acceptance

[Matthew Wilcox]

On Mon, Oct 16, 2023 at 07:31:22PM +0300, Kirill A. Shutemov wrote:
>   v2:
>    - Fix deadlock (Vlastimil);
>    - Fix comments (Vlastimil);
>    - s/cond_resched()/cpu_relax()/ -- cond_resched() cannot be called
>      from atomic context;

Isn't there an implicit cpu_relax() while we're spinning?  Does this
really accomplish anything?

> +retry:
>  	spin_lock_irqsave(&unaccepted_memory_lock, flags);
[...]
> +		spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
> +
> +		/*
> +		 * The code is reachable from atomic context.
> +		 * cond_resched() cannot be used.
> +		 */
> +		cpu_relax();
> +
> +		goto retry;