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Re: [PATCH tracing/kprobes 0/7] tracing/kprobes: kprobe-based event tracer update and perf support
- From: Frederic Weisbecker <fweisbec at gmail dot com>
- To: "Frank Ch. Eigler" <fche at redhat dot com>
- Cc: Masami Hiramatsu <mhiramat at redhat dot com>, Steven Rostedt <rostedt at goodmis dot org>, Ingo Molnar <mingo at elte dot hu>, lkml <linux-kernel at vger dot kernel dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Andi Kleen <ak at linux dot intel dot com>, Christoph Hellwig <hch at infradead dot org>, "H. Peter Anvin" <hpa at zytor dot com>, Jason Baron <jbaron at redhat dot com>, Jim Keniston <jkenisto at us dot ibm dot com>, "K.Prasad" <prasad at linux dot vnet dot ibm dot com>, Lai Jiangshan <laijs at cn dot fujitsu dot com>, Li Zefan <lizf at cn dot fujitsu dot com>, Peter Zijlstra <peterz at infradead dot org>, Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>, Tom Zanussi <tzanussi at gmail dot com>, systemtap <systemtap at sources dot redhat dot com>, DLE <dle-develop at lists dot sourceforge dot net>
- Date: Fri, 11 Sep 2009 21:15:04 +0200
- Subject: Re: [PATCH tracing/kprobes 0/7] tracing/kprobes: kprobe-based event tracer update and perf support
- References: <20090910235258.22412.29317.stgit@dhcp-100-2-132.bos.redhat.com> <20090911013332.GB16396@nowhere> <y0mr5udjoc8.fsf@fche.csb>
On Fri, Sep 11, 2009 at 03:03:35PM -0400, Frank Ch. Eigler wrote:
> Frederic Weisbecker <fweisbec@gmail.com> writes:
>
> > [...] I'm really looking forward seeing this C expression-like
> > kprobe creation tool. It seems powerful enough to replace printk +
> > kernel rebuild. No need anymore to write some printk to debug,
> > worrying, [...]
>
> To a large extent, systemtap had delivered this already some years
> ago, including the cushy ponies dancing in the sunlight. While such
> low-level machinery is fine, some of our experience indicates that it
> is dramatically easier to use if high-level, symbolic, debugging data
> is used to compute probe locations and variable names/types/locations.
>
> It is also too easy to stress the low-level machinery beyond its
> humble origins, in this case meaning putting probes in all kinds of
> tender spots that go "ouch". The kprobes robustness patches coming in
> are great and will benefit all of our efforts, but it will be awhile
> until the kernel can survive a fuzz/crashme type stress test on that
> subsystem. So expect ongoing effort there.
Fully agreed! The more I see corner recursivity cases, the more I think
we'll never fix every potential cases. But yeah it's worth trying to
fix all of them that are reported/anticipated, the more such case
are covered, the more it's usable.