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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 at infradead dot org>
- To: Thomas Gleixner <tglx at linutronix dot de>
- Cc: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>, Ingo Molnar <mingo at elte dot hu>, Steven Rostedt <rostedt at goodmis dot org>, Linux-mm <linux-mm at kvack dot org>, Arnaldo Carvalho de Melo <acme at infradead dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, Christoph Hellwig <hch at infradead dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Andi Kleen <andi at firstfloor dot org>, Oleg Nesterov <oleg at redhat dot com>, Andrew Morton <akpm at linux-foundation dot org>, Jim Keniston <jkenisto at linux dot vnet dot ibm dot com>, Roland McGrath <roland at hack dot frob dot com>, SystemTap <systemtap at sources dot redhat dot com>, LKML <linux-kernel at vger dot kernel dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>
- Date: Tue, 15 Mar 2011 20:48:19 +0100
- Subject: Re: [PATCH v2 2.6.38-rc8-tip 4/20] 4: uprobes: Adding and remove a uprobe in a rb tree.
- References: <20110314133403.27435.7901.sendpatchset@localhost6.localdomain6> <20110314133444.27435.50684.sendpatchset@localhost6.localdomain6> <alpine.LFD.2.00.1103151425060.2787@localhost6.localdomain6> <20110315173041.GB24254@linux.vnet.ibm.com> <alpine.LFD.2.00.1103151916120.2787@localhost6.localdomain6>
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.