linux-kernel - Re: [PATCH 08/10] perf tool: Unify handling of features when writing feature section

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Message-ID: <20111206163358.GL15738@erda.amd.com>
Date:	Tue, 6 Dec 2011 17:33:58 +0100
From:	Robert Richter <robert.richter@....com>
To:	Arnaldo Carvalho de Melo <acme@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Stephane Eranian <eranian@...gle.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 08/10] perf tool: Unify handling of features when writing
 feature section

On 06.12.11 11:36:30, Arnaldo Carvalho de Melo wrote:
> Em Tue, Dec 06, 2011 at 11:32:38AM +0100, Robert Richter escreveu:
> > Also moving special code for HEADER_BUILD_ID out to write_build_id().
> 
> For this one I just would add a big fat warning that if there are
> build-ids on the system but the table can't be written, then extreme
> care has to be taken when doing a perf report.
> 
> I.e. one has to be completely sure that the binaries hasn't changed if
> not validating the build-ids.
> 
> If you fix that please add this warning as well when no build-ids are
> found, which hopefully is the odd case these days as all distros I'm
> aware of have build-ids in all DSOs.

What about the following change in addition? perf record then still
stops with an error, but --no-buildid could be used to proceed anyway:

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 766fa0a..80e08ca 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -493,6 +493,13 @@ static int __cmd_record(struct perf_record *rec, int argc, const char **argv)
                        return err;
        }
 
+       if (!no_buildid
+           && !perf_header__has_feat(&session->header, HEADER_BUILD_ID)) {
+               pr_err("Couldn't generate buildids. "
+                      "Use --no-buildid option to profile anyway.\n");
+               return -1;
+       }
+
        rec->post_processing_offset = lseek(output, 0, SEEK_CUR);
 
        machine = perf_session__find_host_machine(session);


-Robert

-- 
Advanced Micro Devices, Inc.
Operating System Research Center

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