linux-kernel - Re: [PATCH 2/2] augmented rbtree: rework the RB_DECLARE

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Date:   Mon, 1 Jul 2019 16:40:26 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Michel Lespinasse <walken@...gle.com>
Cc:     Davidlohr Bueso <dave@...olabs.net>,
        David Howells <dhowells@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] augmented rbtree: rework the RB_DECLARE_CALLBACKS
 macro definition

On Mon, Jul 01, 2019 at 09:46:30AM +0200, Peter Zijlstra wrote:
> On Fri, Jun 28, 2019 at 05:49:52PM -0700, Michel Lespinasse wrote:

> > The motivation for this change is that I want to introduce augmented rbtree
> > uses where the augmented data for the subtree is a struct instead of a scalar.

> Can't we have a helper macro that converts an old (scalar) style compute
> into a new style compute and avoid this unfortunate and error prone
> copy/pasta ?

Or add a RBEQUAL argument that does:

-		if (node->RBAUGMENTED == augmented)
+		if (RBEQUAL(&node->RBAUGMENTED, &augmented))

With a bit of foo you can even provide a default implementation that
does: *a == *b.

See GEN_UNARY_RMWcc() for how to do that.