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Date:   Fri, 15 May 2020 21:27:05 -0700
From:   Michel Lespinasse <>
To:     Lai Jiangshan <>
        "Paul E . McKenney" <>,
        Oleg Nesterov <>,
        Andrea Arcangeli <>,
        Rik van Riel <>,
        Mathieu Desnoyers <>,
        Peter Zijlstra <>
Subject: Re: [PATCH V2 2/2] rbtree_latch: don't need to check seq when it
 found a node

On Fri, May 15, 2020 at 03:59:09PM +0000, Lai Jiangshan wrote:
> latch_tree_find() should be protected by caller via RCU or so.
> When it find a node in an attempt, the node must be a valid one
> in RCU's point's of view even the tree is (being) updated with a
> new node with the same key which is entirely subject to timing
> anyway.

I'm not sure I buy this. Even if we get a valid node, is it the one we
were searching for ? I don't see how this could be guaranteed if the
read raced with a tree rebalancing.

Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.

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