On Tue, Jun 1, 2010 at 11:42 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> 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. > Yes. I had missed that rotate_right of parent following the rotate_left of sibling (or vice-versa). Thanks for fixing this. The latest patch looks good. Acked-by: Venkatesh Pallipadi <venki@xxxxxxxxxx> -- 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