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From: Ingo Molnar <mingo@elte.hu>
Subject: Re: linux-next: add utrace tree
Date: Fri, 29 Jan 2010 10:51:52 +0100
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To: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Jim Keniston <jkenisto@us.ibm.com>, Stephen Rothwell <sfr@canb.auug.org.au>, Kyle Moffett <kyle@moffetthome.net>, Arnaldo Carvalho de Melo <acme@redhat.com>, Peter Zijlstra <peterz@infradead.org>, Fr??d??ric Weisbecker <fweisbec@gmail.com>, Oleg Nesterov <oleg@redhat.com>, Steven Rostedt <rostedt@goodmis.org>, LKML <linux-kernel@vger.kernel.org>, Tom Tromey <tromey@redhat.com>, "Frank Ch. Eigler" <fche@redhat.com>, linux-next@vger.kernel.org, "H. Peter Anvin" <hpa@zytor.com>, utrace-devel@redhat.com, Linus Torvalds <torvalds@linux-foundation.org>, Thomas Gleixner <tglx@linutronix.de>


* Ananth N Mavinakayanahalli <ananth@in.ibm.com> wrote:

> On Fri, Jan 29, 2010 at 10:11:16AM +0100, Ingo Molnar wrote:
> > 
> > * Ananth N Mavinakayanahalli <ananth@in.ibm.com> wrote:
> > 
> > > On Fri, Jan 29, 2010 at 08:39:07AM +0100, Ingo Molnar wrote:
> > > 
> > > ...
> > > 
> > > > When we merged kprobes ~10 years ago we made the (rather bad) mistake of 
> > > > merging a raw, opaque facility and leaving 'the rest' up to some other entity. 
> > > > IBM kprobes hackers vanished the day the original kprobes code went upstream 
> > > > and the high level entity never truly materialized in-kernel, for nearly a 
> > > > decade!
> > > 
> > > I don't know what you are referring to here... Kprobes was merged in 2.6.9 
> > > (~August 2004 -- less than 6 years ago). [...]
> > 
> > Ok, 6 years then :-)
> >
> > > [...] Since then, we did work on ports to powerpc and s390. We implemented 
> > > kretprobes. We made it much scalable using RCU; we did the powerpc booster 
> > > to skip single-step when possible, not to mention various bug fixes over the 
> > > years.
> > 
> > Except it had no real in-kernel user.
> 
> Not that I want to rebut you Ingo, but there were in-kernel users since 2006
> (net/ipv4/tcp_probe.c) :-)

i said 'real' users. That usage in tcp_probe.c was (and is) really minimal and 
never expanded really.

> Aside, I am also glad that we have more flexibility with the perf 
> integration.

ok, good :)

	Ingo