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Subject: Re: [PATCH v2 2.6.38-rc8-tip 4/20] 4: uprobes: Adding and remove a uprobe in a rb tree.
From: Peter Zijlstra <peterz@infradead.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>, Ingo Molnar <mingo@elte.hu>,  Steven Rostedt <rostedt@goodmis.org>, Linux-mm <linux-mm@kvack.org>, Arnaldo Carvalho de Melo <acme@infradead.org>,  Linus Torvalds <torvalds@linux-foundation.org>, Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,  Christoph Hellwig <hch@infradead.org>, Ananth N Mavinakayanahalli <ananth@in.ibm.com>, Andi Kleen <andi@firstfloor.org>, Oleg Nesterov <oleg@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Jim Keniston <jkenisto@linux.vnet.ibm.com>,  Roland McGrath <roland@hack.frob.com>, SystemTap <systemtap@sources.redhat.com>, LKML <linux-kernel@vger.kernel.org>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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On Tue, 2011-03-15 at 20:22 +0100, Thomas Gleixner wrote:
> I am not sure if its a good idea to walk the tree
> > as and when the tree is changing either because of a insertion or
> > deletion of a probe.
> 
> I know that you cannot walk the tree lockless except you would use
> some rcu based container for your probes. 

You can in fact combine a seqlock, rb-trees and RCU to do lockless
walks.

  https://lkml.org/lkml/2010/10/20/160

and

  https://lkml.org/lkml/2010/10/20/437

But doing that would be an optimization best done once we get all this
working nicely.