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

[Ard Biesheuvel]

On Mon, 16 Oct 2023 at 23:39, Kirill A. Shutemov
<kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
>
> On Mon, Oct 16, 2023 at 06:55:41PM +0100, Matthew Wilcox wrote:
> > 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?
>
> You are right. It is useless. I will drop it in v3.
>

I can drop that bit when applying the patch.

One question I have is whether the sequence

spin_lock_irqsave(&unaccepted_memory_lock, flags);
...
spin_unlock(&unaccepted_memory_lock);
arch_accept_memory(phys_start, phys_end);
spin_lock(&unaccepted_memory_lock);
...
spin_unlock_irqrestore(&unaccepted_memory_lock, flags);

is considered sound and is supported by all architectures?