[Crash-utility] Re: [ANNOUNCE][RFC][PATCH] Crash-utility, tracing: enable crash to analyze tracing from core-file (make tracing can act as a flight recorder)
----- Forwarded Message -----
From: "Peter Zijlstra" <peterz(a)infradead.org>
To: "Lai Jiangshan" <laijs(a)cn.fujitsu.com>
Cc: "Dave Anderson" <anderson(a)redhat.com>, "Ingo Molnar"
<mingo(a)elte.hu>, "Frederic Weisbecker" <fweisbec(a)gmail.com>,
"Thomas Gleixner" <tglx(a)linutronix.de>, "Arnaldo Carvalho de
Melo" <acme(a)ghostprotocols.net>, "Luis Claudio R. Goncalves"
<lclaudio(a)uudg.org>, "Clark Williams" <clark.williams(a)gmail.com>,
"Jon Masters" <jonathan(a)jonmasters.org>, "Andrew Morton"
<akpm(a)linux-foundation.org>, "Mathieu Desnoyers"
<mathieu.desnoyers(a)polymtl.ca>, "Christoph Hellwig"
<hch(a)infradead.org>, "Xiao Guangrong"
<xiaoguangrong(a)cn.fujitsu.com>, "Zhaolei" <zhaolei(a)cn.fujitsu.com>,
"kosaki motohiro" <kosaki.motohiro(a)jp.fujitsu.com>, "Li Zefan"
<lizf(a)cn.fujitsu.com>, "Masami Hiramatsu" <mhiramat(a)redhat.com>,
"Frank Ch. Eigler" <fche(a)redhat.com>, "Tom Zanussi"
<tzanussi(a)gmail.com>, "Jason Baron" <jbaron(a)redhat.com>,
srostedt(a)redhat.com, "LKML" <linux-kernel(a)vger.kernel.org>
Sent: Tuesday, August 4, 2009 6:36:52 AM GMT -05:00 US/Canada Eastern
Subject: Re: [ANNOUNCE][RFC][PATCH] Crash-utility, tracing: enable crash to analyze
tracing from core-file (make tracing can act as a flight recorder)
On Tue, 2009-08-04 at 14:52 +0800, Lai Jiangshan wrote:
Peter Zijlstra wrote:
> On Mon, 2009-08-03 at 22:48 +0800, Lai Jiangshan wrote:
>> + /* SIGH, we cann't get "print fmt" from core-file */
>
> doesn't crash have a vmlinux around to look at?
I don't known how to look at it:
static int \
ftrace_format_##call(struct trace_seq *s) \
{ \
struct ftrace_raw_##call field __attribute__((unused)); \
int ret = 0; \
\
tstruct; \
\
trace_seq_printf(s, "\nprint fmt: " print); \
\
return ret; \
}
We need the address of the const string <"\nprint fmt: " print>,
I don't know how to get it current from vmlinux.
I have sent a patch which try to reduce the size of .txt in kernel
and reduce coupling. This patch has a little side-effect:
the "print fmt"'s address is saved in struct ftrace_event_call.
Aah, right, I thought the fmt string was easily obtainable from the
_ftrace_events section, but now I see it is not, the patch you mention
below does indeed make it so.
[
http://lkml.org/lkml/2009/7/30/30
This patch is really useful for kernel. We don't change the kernel
even a single line for the purpose of we can read the core-file easier.
Well, I see no harm in changing the kernel a little when it makes no
difference to the kernel but makes post-mortem analysis a little bit
easier.
This patch is also helpful for crash more or less. So I mention it.
]