----- Forwarded Message -----
From: "Peter Zijlstra" <peterz@xxxxxxxxxxxxx>
To: "Lai Jiangshan" <laijs@xxxxxxxxxxxxxx>
Cc: "Dave Anderson" <anderson@xxxxxxxxxx>, "Ingo Molnar" <mingo@xxxxxxx>, "Frederic Weisbecker" <fweisbec@xxxxxxxxx>, "Thomas Gleixner" <tglx@xxxxxxxxxxxxx>, "Arnaldo Carvalho de Melo" <acme@xxxxxxxxxxxxxxxxxx>, "Luis Claudio R. Goncalves" <lclaudio@xxxxxxxx>, "Clark Williams" <clark.williams@xxxxxxxxx>, "Jon Masters" <jonathan@xxxxxxxxxxxxxx>, "Andrew Morton" <akpm@xxxxxxxxxxxxxxxxxxxx>, "Mathieu Desnoyers" <mathieu.desnoyers@xxxxxxxxxx>, "Christoph Hellwig" <hch@xxxxxxxxxxxxx>, "Xiao Guangrong" <xiaoguangrong@xxxxxxxxxxxxxx>, "Zhaolei" <zhaolei@xxxxxxxxxxxxxx>, "kosaki motohiro" <kosaki.motohiro@xxxxxxxxxxxxxx>, "Li Zefan" <lizf@xxxxxxxxxxxxxx>, "Masami Hiramatsu" <mhiramat@xxxxxxxxxx>, "Frank Ch. Eigler" <fche@xxxxxxxxxx>, "Tom Zanussi" <tzanussi@xxxxxxxxx>, "Jason Baron" <jbaron@xxxxxxxxxx>, srostedt@xxxxxxxxxx, "LKML" <linux-kernel@xxxxxxxxxxxxxxx>
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.
> ]
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