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Date: Thu, 9 Apr 2015 09:31:16 -0700
Message-ID: <CA+55aFzL+0wDKev7ZWWMZVfr5ofcX=1qyCFkwMehC4ti0=C0CQ@mail.gmail.com>
Subject: Re: [PATCH v4 6/9] rbtree: Implement generic latch_tree
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>, Ingo Molnar <mingo@kernel.org>,
        Rusty Russell <rusty@rustcorp.com.au>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Andi Kleen <andi@firstfloor.org>, Steven Rostedt <rostedt@goodmis.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Michel Lespinasse <walken@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        David Woodhouse <David.Woodhouse@intel.com>,
        Rik van Riel <riel@redhat.com>
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On Thu, Apr 9, 2015 at 5:13 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>
>  struct latch_tree_node {
> +       struct rb_node node[2];
>  };
>
> +static __always_inline struct latch_tree_node *
> +__lt_from_rb(struct rb_node *node, int idx)
> +{
> +       return container_of(node, struct latch_tree_node, node[idx]);
> +}

Ugh. That syntax of offset_of() worries me a bit, but some grepping
shows that we already use this form of offset_of() in parts of the
kernel, so I guess it's fine.

Even with that small "Ugh", I do have to admit to preferring this to
having the back-pointer.

                        Linus
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