Re: linux-next: add utrace tree

[Ingo Molnar <mingo@elte.hu>]

* 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