Date: Thu, 9 Apr 2015 18:59:17 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Linus Torvalds <torvalds@linux-foundation.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>
Subject: Re: [PATCH v4 6/9] rbtree: Implement generic latch_tree
Message-ID: <20150409165917.GQ21418@twins.programming.kicks-ass.net>
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On Thu, Apr 09, 2015 at 09:31:16AM -0700, Linus Torvalds wrote:
> 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.

I was a little surprised myself it worked, but its a constant after
all so it 'should'.

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

Yeah me too, I'll respin the patches proper after I've given it some
actual runtime too.
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