Date:	Mon, 7 Dec 2015 15:04:27 +0100
From:	Martin Liška <mliska@...e.cz>
To:	Jiri Olsa <jolsa@...hat.com>
Cc:	Jiri Olsa <jolsa@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RFC] The -Og debugging experience

On 12/07/2015 02:45 PM, Jiri Olsa wrote:
> On Mon, Dec 07, 2015 at 11:48:07AM +0100, Martin Liška wrote:
>> On 12/02/2015 05:48 PM, Jiri Olsa wrote:
>>> heya,
>>> using the -Og for DEBUG=1 builds gives me many 'optimized out' stuff
>>>
>>> It was introduced in here:
>>>   e8b7ea4356fd perf tools: Improve setting of gcc debug option
>>>
>>> - here's backtrace from segfault I was looking at, current code:
>>
>> Hi.
>>
>> Can you please provide a test-case which I can use for testing of the issue?
> 
> just run perf report in gdb and kill it with sigsegv from other terminal
> this gives me several instances of <optimized out> right in the backtrace
> 
> jirka
> 

Hi.

Unfortunately, running 'perf report' for a medium-size report is very fast a
killing the process from other terminal produces:

[Current thread is 1 (Thread 0x7ffff7fc5740 (LWP 7429))]
(gdb) bt
#0  0x00007ffff632d230 in __write_nocancel () from /lib64/libc.so.6
#1  0x00007ffff62c4dff in _IO_new_file_write () from /lib64/libc.so.6
#2  0x00007ffff62c4403 in new_do_write () from /lib64/libc.so.6
#3  0x00007ffff62c5d09 in __GI__IO_do_write () from /lib64/libc.so.6
#4  0x00007ffff62c5417 in __GI__IO_file_xsputn () from /lib64/libc.so.6
#5  0x00007ffff6299cdb in vfprintf () from /lib64/libc.so.6
#6  0x00007ffff62a03f7 in fprintf () from /lib64/libc.so.6
#7  0x00000000004ef12c in hist_entry__fprintf (he=he@...ry=0x1c62b30, size=<optimized out>, size@...ry=0, hists=hists@...ry=0x1813818, 
    bf=bf@...ry=0x1d5cd40 "     0.08%  cc1plus   cc1plus", ' ' <repeats 11 times>, "[.] _Z25number_of_iterations_exitP4loopP8edge_defP15tree_niter_descbb", ' ' <repeats 91 times>..., bfsz=bfsz@...ry=479, fp=fp@...ry=0x7ffff65f0640 <_IO_2_1_stdout_>)
    at ui/stdio/hist.c:427
#8  0x00000000004ef549 in hists__fprintf (hists=hists@...ry=0x1813818, show_header=show_header@...ry=true, max_rows=max_rows@...ry=0, max_cols=max_cols@...ry=0, min_pcnt=0, fp=0x7ffff65f0640 <_IO_2_1_stdout_>) at ui/stdio/hist.c:534
#9  0x000000000042d6a3 in perf_evlist__tty_browse_hists (evlist=0x1812c90, rep=rep@...ry=0x7fffffffc6e0, help=help@...ry=0x515948 "For a higher level overview, try: perf report --sort comm,dso") at builtin-report.c:370
#10 0x000000000042d7d2 in report__browse_hists (rep=rep@...ry=0x7fffffffc6e0) at builtin-report.c:455
#11 0x000000000042d992 in __cmd_report (rep=rep@...ry=0x7fffffffc6e0) at builtin-report.c:571
#12 0x000000000042ec1f in cmd_report (argc=0, argv=0x7fffffffde00, prefix=<optimized out>) at builtin-report.c:957
#13 0x000000000046c496 in run_builtin (p=p@...ry=0x7771a0 <commands+192>, argc=argc@...ry=1, argv=argv@...ry=0x7fffffffde00) at perf.c:387
#14 0x000000000046c693 in handle_internal_command (argc=1, argv=0x7fffffffde00) at perf.c:448
#15 0x000000000046c6fe in run_argv (argcp=argcp@...ry=0x7fffffffdc6c, argv=argv@...ry=0x7fffffffdc60) at perf.c:492
#16 0x000000000046c94c in main (argc=1, argv=0x7fffffffde00) at perf.c:609

Which is fine.

I've been using GCC 5.2. What version are you using?
I've also tried to run './perf test' and terminate the process at random places, but the back trace was OK.

I would appreciate if you send me a patch that causes a segfault that is wrongly displayed.
Thanks,
Martin
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