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Message-ID: <20200516042705.GA82414@google.com>
Date: Fri, 15 May 2020 21:27:05 -0700
From: Michel Lespinasse <walken@...gle.com>
To: Lai Jiangshan <laijs@...ux.alibaba.com>
Cc: linux-kernel@...r.kernel.org,
"Paul E . McKenney" <paulmck@...nel.org>,
Oleg Nesterov <oleg@...hat.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Rik van Riel <riel@...hat.com>,
Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
Peter Zijlstra <peterz@...radead.org>
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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