perf stat record: Keep sample_type 0 for pipe session

For pipe sessions we need to keep sample_type zero, because script's
perf_evsel__check_attr is triggered by sample_type != 0, and the check
would fail on stat session.

I was tempted to keep it zero unconditionally, but the pipe session is
sufficient. In perf.data session we are guarded by HEADER_STAT feature.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Kan Liang <kan.liang@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1452028152-26762-2-git-send-email-jolsa@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-stat.c

@@ -184,11 +184,18 @@ static int create_perf_stat_counter(struct perf_evsel *evsel)
 	 * like tracepoints. Clear it up for counting.
 	 */
 	attr->sample_period = 0;
+
 	/*
 	 * But set sample_type to PERF_SAMPLE_IDENTIFIER, which should be harmless
 	 * while avoiding that older tools show confusing messages.
+	 *
+	 * However for pipe sessions we need to keep it zero,
+	 * because script's perf_evsel__check_attr is triggered
+	 * by attr->sample_type != 0, and we can't run it on
+	 * stat sessions.
 	 */
-	attr->sample_type   = PERF_SAMPLE_IDENTIFIER;
+	if (!(STAT_RECORD && perf_stat.file.is_pipe))
+		attr->sample_type = PERF_SAMPLE_IDENTIFIER;
 
 	/*
 	 * Disabling all counters initially, they will be enabled