On Wed, Jun 2, 2010 at 2:11 PM, Suresh Siddha <suresh.b.siddha@xxxxxxxxx> wrote: > On Tue, 2010-06-01 at 11:42 -0700, Peter Zijlstra wrote: >> On Tue, 2010-06-01 at 11:09 -0700, Venkatesh Pallipadi wrote: >> > On Tue, Jun 1, 2010 at 10:42 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: >> > > On Tue, 2010-06-01 at 10:34 -0700, Venkatesh Pallipadi wrote: >> > >> >> > >> Yes. This will cover all the cases on insert. But on erase, there is >> > >> still a case where a rotate of sibling node is done during the >> > >> re-coloration process. There we have a child change on sibling's >> > >> child. I am not able to think of any easy way to handle that case. >> > > >> > > Let me go draw some figures with pen and paper to match up the erase >> > > path with the rb_augment_erase_begin() code, because I can't quite spot >> > > the case we're missing. >> > > >> > > If you have it handy, ascii art might help.. >> > >> > It is this case >> > >> > P >> > / \ >> > N S >> > / \ >> > SL SR >> > >> > changing to >> > >> > P >> > / \ >> > N SL >> > \ >> > S >> > \ >> > SR >> >> Right, but see: http://en.wikipedia.org/wiki/Red-black_tree >> That is delete_case5, however then we fall into delete_case6 and perform >> a left rotation. >> >> So suppose we start with the tree: >> >> P P P SL >> / \ / \ / \ / \ >> D S --> N S --> N SL --> P S >> \ / \ / \ \ / \ >> N SL SR SL* SR S* N SR >> \ >> SR >> >> and then remove D, delete case 5 and finally delete case 6, * marks red. >> >> rb_augment_erase_begin(D) will return N, and then rb_augment_path(N) >> will re-augment: N, P, SL and S. > > > 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() should take care of that. In this case, it will return S as the deepest node and we start the walk-back-to-root from there. Thanks, Venki -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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