linux-kernel - Re: [PATCH 3/3] rbtree_test: add more rbtree integrity checks

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Date:	Fri, 22 Mar 2013 16:12:47 -0700
From:	Davidlohr Bueso <davidlohr.bueso@...com>
To:	Michel Lespinasse <walken@...gle.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] rbtree_test: add more rbtree integrity checks

On Thu, 2013-03-21 at 20:36 -0700, Michel Lespinasse wrote:
> On Mon, Mar 18, 2013 at 4:21 PM, Davidlohr Bueso <davidlohr.bueso@...com> wrote:
> > When checking the rbtree, account for more properties:
> >
> >    - Both children of a red node are black.
> >    - The tree has at least 2**bh(v)-1 internal nodes.
> 
> > -               WARN_ON_ONCE(is_red(rb) &&
> > -                            (!rb_parent(rb) || is_red(rb_parent(rb))));
> > +
> > +               if (is_red(rb)) {
> > +                       /*
> > +                        * root must be black and no path contains two
> > +                        * consecutive red nodes.
> > +                        */
> > +                       WARN_ON_ONCE(!rb_parent(rb) || is_red(rb_parent(rb)));
> > +
> > +                       /* both children of a red node are black */
> > +                       WARN_ON_ONCE(is_red(rb->rb_left) || is_red(rb->rb_right));
> > +               }
> 
> This seems quite redundant with the previous test - if we're going to
> visit each children, then at that point we're going to check that they
> can't be black if their parent (the current node) is black. So I don't
> see that the tests adds any coverage.

Hmm ok I see your point. I'll drop this test and just keep the last one.

Thanks for taking a look,
Davidlohr

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