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SubjectRe: [PATCH] rbtree: undo augmented damage -v2
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On Thu, 2010-06-03 at 09:13 +0200, Peter Zijlstra wrote:
> On Wed, 2010-06-02 at 14:11 -0700, Suresh Siddha wrote:
> > P SL
> > / \ / \
> > N S ---> N S
> > / / \ / \
> > C SL SR C SR
> >
> > If P needs to be removed, we need to re-augment S also in this case,
> > right? It looks like we are not handling this case.
>
>
> rb_augment_erase_begin(P) will return S if I read the code right, so
> rb_augment_path(S) will the re-augment S, SL, N.

To be more explicit: P has two children, so we select the next entry,
SL, as its substitute. Since SL doesn't have a right child we select its
parent, S.

If SL were to represent a subtree with a right child, then we'd select
that, lets call it SLR. SLR would then end up being a direct descendant
of S, and hence rb_augment_path(SLR) would still pass S on its way up.




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