linux-kernel - Re: [PATCH] rbtree: stop iteration early in rb_find

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Message-ID: <YSZD6suya8fR/2uY@hirez.programming.kicks-ass.net>
Date:   Wed, 25 Aug 2021 15:21:46 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Michel Lespinasse <michel@...pinasse.org>
Cc:     Li RongQing <lirongqing@...du.com>, dbueso@...e.de,
        mingo@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rbtree: stop iteration early in rb_find_first

On Wed, Aug 25, 2021 at 04:58:59AM -0700, Michel Lespinasse wrote:
> > NAK. This looked slightly wrong before, and is more wrong after.

> Actually, my explanation is wrong too :) but so is the code.
> A failing example would searching 10 in the following tree
> 
> 
>                         10
> 		       /
> 		      5
> 		       \
> 		        10
> 
> The search would stop after visiting node 5, and miss the leaf which
> is the expected node to be returned.

Just to clarify; the current code *does* work here. The proposed patch
breaks it.