linux-kernel - Re: [PATCH v2] perf tools: Introduce perf

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Message-ID: <20151202081605.GB26308@krava.brq.redhat.com>
Date:	Wed, 2 Dec 2015 09:16:05 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Subject: Re: [PATCH v2] perf tools: Introduce perf_thread for backtrace

On Wed, Dec 02, 2015 at 02:42:21PM +0900, Namhyung Kim wrote:
> Backtrace is a crucial info for debugging.  And upcoming refcnt
> tracking facility also wants to use it.
> 
> So instead of relying on glibc's backtrace_symbols[_fd] which misses
> some (static) functions , use our own symbol searching mechanism.  To
> do that, add perf_thread global variable to keep its maps and symbols.
> 
> The backtrace output from TUI is changed like below.  (I made a key
> action to generate a segfault):
> 
> Before:
>   perf: Segmentation fault
>   -------- backtrace --------
>   perf[0x544a8b]
>   /usr/lib/libc.so.6(+0x33680)[0x7fc46420b680]
>   perf[0x54041b]
>   perf(perf_evlist__tui_browse_hists+0x91)[0x5432e1]
>   perf(cmd_report+0x1d20)[0x43cb10]
>   perf[0x487073]
>   perf(main+0x62f)[0x42cb1f]
>   /usr/lib/libc.so.6(__libc_start_main+0xf0)[0x7fc4641f8610]
>   perf(_start+0x29)[0x42cc39]
> 
> After:
>   perf: Segmentation fault
>   -------- backtrace --------
>   perf_evsel__hists_browse(+0x43b) in perf [0x54066b]
>   perf_evlist__tui_browse_hists(+0x91) in perf [0x543531]
>   cmd_report(+0x1d20) in perf [0x43cb50]
>   run_builtin(+0x53) in perf [0x4870b3]
>   main(+0x634) in perf [0x42cb54]
>   __libc_start_main(+0xf0) in libc-2.22.so [0x7fea3577c610]
>   _start(+0x29) in perf [0x42cc79]
> 
> Cc: Frederic Weisbecker <fweisbec@...il.com>
> Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
> v2) fallback to glibc's backtrace_symbols_fd() if failed

create_perf_thread still returns void

jirka
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