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Re: [Xen-devel] [PATCH v6 07/16 RESEND] rbtree: adjust node color in __rb_erase_color() only when necessary

>>> On 21.11.17 at 16:20, <kpraveen.lkml@xxxxxxxxx> wrote:
> From: Michel Lespinasse <walken@xxxxxxxxxx>
> In __rb_erase_color(), we were always setting a node to black after
> exiting the main loop.  And in one case, after fixing up the tree to
> satisfy all rbtree invariants, we were setting the current node to root
> just to guarantee a loop exit, at which point the root would be set to
> black.  However this is not necessary, as the root of an rbtree is already
> known to be black.  The only case where the color flip is required is when
> we exit the loop due to the current node being red, and it's easiest to
> just do the flip at that point instead of doing it after the loop.
> [adrian.hunter@xxxxxxxxx: perf tools: fix build for another rbtree.c change]
> Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx>
> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> Acked-by: David Woodhouse <David.Woodhouse@xxxxxxxxx>
> Cc: Rik van Riel <riel@xxxxxxxxxx>
> Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
> Cc: Daniel Santos <daniel.santos@xxxxxxxxx>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
> Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxx>
> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> [Linux commit d6ff1273928ebf15466a85b7e1810cd00e72998b]
> Ported only rbtree.c to Xen.
> Signed-off-by: Praveen Kumar <kpraveen.lkml@xxxxxxxxx>

Acked-by: Jan Beulich <jbeulich@xxxxxxxx>

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