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SubjectRe: [PATCH 1/2] locking: Implement an algorithm choice for Wound-Wait mutexes
On Wed, Jun 13, 2018 at 09:47:44AM +0200, Thomas Hellstrom wrote:
> -----
>
> +The algorithm (Wait-Die vs Wound-Wait) is chosen using the _is_wait_die
> +argument to DEFINE_WW_CLASS(). As a rough rule of thumb, use Wound-Wait iff you
> +typically expect the number of simultaneous competing transactions to be small,
> +and the rollback cost can be substantial.
> +
> Three different ways to acquire locks within the same w/w class. Common
> definitions for methods #1 and #2:
>
> -static DEFINE_WW_CLASS(ww_class);
> +static DEFINE_WW_CLASS(ww_class, false);

Minor nit on the api here. Having a "flag" is a royal pain. You have
to go and look up exactly what that "true/false" means every time you
run across it in code to figure out what it means. Don't do that if at
all possible.

Make a new api:
DEFINE_WW_CLASS_DIE(ww_class);
instead that then wraps that boolean internally to switch between the
different types. That way the api is "self-documenting" and we all know
what is going on without having to dig through a header file.

thanks,

greg k-h

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