Re: [PATCHv3 0/2]

[Sean Christopherson <seanjc@google.com>]

On Fri, Feb 28, 2025, Sean Christopherson wrote:
> On Fri, Feb 28, 2025, Lei Yang wrote:
> > Hi Keith
> > 
> > V3 introduced a new bug, the following error messages from qemu output
> > after applying this patch to boot up a guest.
> 
> Doh, my bug.  Not yet tested, but this should fix things.  Assuming it does, I'll
> post a v3 so I can add my SoB.
         v4

Confirmed that it worked, but deleting the pre-mutex check for ONCE_COMPLETED.
Will post v4 later today.

> diff --git a/include/linux/call_once.h b/include/linux/call_once.h
> index ddcfd91493ea..b053f4701c94 100644
> --- a/include/linux/call_once.h
> +++ b/include/linux/call_once.h
> @@ -35,10 +35,12 @@ static inline int call_once(struct once *once, int (*cb)(struct once *))
>                 return 0;
>  
>          guard(mutex)(&once->lock);
> -        WARN_ON(atomic_read(&once->state) == ONCE_RUNNING);
> -        if (atomic_read(&once->state) != ONCE_NOT_STARTED)
> +        if (WARN_ON(atomic_read(&once->state) == ONCE_RUNNING))
>                  return -EINVAL;
>  
> +        if (atomic_read(&once->state) == ONCE_COMPLETED)
> +                return 0;
> +
>          atomic_set(&once->state, ONCE_RUNNING);
>         r = cb(once);
>         if (r)