Re: [PATCH v4 6/9] rbtree: Implement generic latch_tree

From: Peter Zijlstra <peterz@infradead.org>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: mingo@kernel.org, rusty@rustcorp.com.au,
	mathieu.desnoyers@efficios.com, oleg@redhat.com,
	paulmck@linux.vnet.ibm.com, torvalds@linux-foundation.org,
	linux-kernel@vger.kernel.org, andi@firstfloor.org,
	rostedt@goodmis.org, 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
Date: Thu, 9 Apr 2015 10:14:20 +0200	[thread overview]
Message-ID: <20150409081420.GM5029@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <552633A3.5020502@cn.fujitsu.com>

On Thu, Apr 09, 2015 at 04:09:07PM +0800, Lai Jiangshan wrote:
> On 04/09/2015 12:48 AM, Peter Zijlstra wrote:
> 
> > +
> > +struct latch_tree_node {
> > +	/*
> > +	 * Because we have an array of two entries in struct latch_tree_nodes
> > +	 * it's not possible to use container_of() to get back to the
> > +	 * encapsulating structure; therefore we have to put in a back pointer.
> > +	 */
> > +	void		*priv;
> > +	struct rb_node	node;
> > +};
> 
> I don't think @priv is strictly needed. It is possible to use container_of()
> to go back. @priv is even not used in this file (except the initialization).
> 
> First, we can use container_of() to find encapsulating structure from the
> struct latch_tree_nodeS.
> 
> Second, we can add a @idx to __lt_insert() and __lt_find(), 

insert yes, find no. Remember that both nodes are in the _same_ tree.

There is no way of knowing if a tree node is an init or core node while
iterating.