linux-kernel - Re: [PATCH 5/7] perf session: don't rely on evlist in pipe mode

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Date:   Tue, 11 Apr 2017 15:40:50 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     David Carrillo-Cisneros <davidcc@...gle.com>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>, Simon Que <sque@...omium.org>,
        Wang Nan <wangnan0@...wei.com>, Jiri Olsa <jolsa@...nel.org>,
        He Kuang <hekuang@...wei.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        Paul Turner <pjt@...gle.com>
Subject: Re: [PATCH 5/7] perf session: don't rely on evlist in pipe mode

Em Tue, Apr 11, 2017 at 03:40:14PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Apr 10, 2017 at 01:14:30PM -0700, David Carrillo-Cisneros escreveu:
> > Session sets a number parameters that rely on evlist. These parameters
> > are not used in pipe-mode and should not be set, since evlist is
> > unavailable. Fix that.
> 
> Ditching this one as well, until further investigation, well, file must
> be null in this case...

Ah, this is the problem:

[root@...et ~]# perf top
perf: Segmentation fault
-------- backtrace --------
perf[0x57eddb]
/lib64/libc.so.6(+0x35990)[0x7fb435d06990]
perf(perf_session__new+0xb7)[0x4eb547]
perf(cmd_top+0xde9)[0x44ce89]
perf[0x49953f]
perf[0x499831]
perf(main+0x252)[0x428dd2]
/lib64/libc.so.6(__libc_start_main+0xf1)[0x7fb435cf1401]
perf(_start+0x2a)[0x4292da]
[0x0]
[root@...et ~]#
 
> [acme@...et linux]$ git bisect bad
> 5d71c27204d51492abe9fc69064fd36a0bda410b is the first bad commit
> commit 5d71c27204d51492abe9fc69064fd36a0bda410b
> Author: David Carrillo-Cisneros <davidcc@...gle.com>
> Date:   Mon Apr 10 13:14:30 2017 -0700
> 
>     perf session: Don't rely on evlist in pipe mode
>     
>     Session sets a number parameters that rely on evlist. These parameters
>     are not used in pipe-mode and should not be set, since evlist is
>     unavailable. Fix that.
>     
>     Signed-off-by: David Carrillo-Cisneros <davidcc@...gle.com>
>     Acked-by: Jiri Olsa <jolsa@...nel.org>
>     Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
>     Cc: Andi Kleen <ak@...ux.intel.com>
>     Cc: He Kuang <hekuang@...wei.com>
>     Cc: Masami Hiramatsu <mhiramat@...nel.org>
>     Cc: Paul Turner <pjt@...gle.com>
>     Cc: Peter Zijlstra <peterz@...radead.org>
>     Cc: Simon Que <sque@...omium.org>
>     Cc: Stephane Eranian <eranian@...gle.com>
>     Cc: Wang Nan <wangnan0@...wei.com>
>     Link: http://lkml.kernel.org/r/20170410201432.24807-6-davidcc@google.com
>     Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> 
> :040000 040000 7df28fe9d7c9d962b78c0532f4961caea2737b59 34e4fed0042b1401c1a1a247d8ae40df17f9d272 M	tools
> [acme@...et linux]$
>  
> > Signed-off-by: David Carrillo-Cisneros <davidcc@...gle.com>
> > ---
> >  tools/perf/util/session.c | 16 +++++++++++++---
> >  1 file changed, 13 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> > index a25302bc55a8..db554b7461b8 100644
> > --- a/tools/perf/util/session.c
> > +++ b/tools/perf/util/session.c
> > @@ -140,8 +140,14 @@ struct perf_session *perf_session__new(struct perf_data_file *file,
> >  			if (perf_session__open(session) < 0)
> >  				goto out_close;
> >  
> > -			perf_session__set_id_hdr_size(session);
> > -			perf_session__set_comm_exec(session);
> > +			/*
> > +			 * set session attributes that are present in perf.data
> > +			 * but not in pipe-mode.
> > +			 */
> > +			if (!file->is_pipe) {
> > +				perf_session__set_id_hdr_size(session);
> > +				perf_session__set_comm_exec(session);
> > +			}
> >  		}
> >  	} else  {
> >  		session->machines.host.env = &perf_env;
> > @@ -156,7 +162,11 @@ struct perf_session *perf_session__new(struct perf_data_file *file,
> >  			pr_warning("Cannot read kernel map\n");
> >  	}
> >  
> > -	if (tool && tool->ordering_requires_timestamps &&
> > +	/*
> > +	 * In pipe-mode, evlist is empty until PERF_RECORD_HEADER_ATTR is
> > +	 * processed, so perf_evlist__sample_id_all is not meaningful here.
> > +	 */
> > +	if (!file->is_pipe && tool && tool->ordering_requires_timestamps &&
> >  	    tool->ordered_events && !perf_evlist__sample_id_all(session->evlist)) {
> >  		dump_printf("WARNING: No sample_id_all support, falling back to unordered processing\n");
> >  		tool->ordered_events = false;
> > -- 
> > 2.12.2.715.g7642488e1d-goog