perf machine: Add machine__thread_exec_comm()

Add machine__thread_exec_comm() to return the comm that matches the last
exec, if the comm_exec flag is present, or the last comm otherwise.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1406786474-9306-3-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 1b383bd..6d2d50d 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -67,6 +67,25 @@
 	machines__destroy_kernel_maps(&session->machines);
 }
 
+static bool perf_session__has_comm_exec(struct perf_session *session)
+{
+	struct perf_evsel *evsel;
+
+	evlist__for_each(session->evlist, evsel) {
+		if (evsel->attr.comm_exec)
+			return true;
+	}
+
+	return false;
+}
+
+static void perf_session__set_comm_exec(struct perf_session *session)
+{
+	bool comm_exec = perf_session__has_comm_exec(session);
+
+	machines__set_comm_exec(&session->machines, comm_exec);
+}
+
 struct perf_session *perf_session__new(struct perf_data_file *file,
 				       bool repipe, struct perf_tool *tool)
 {
@@ -90,6 +109,7 @@
 				goto out_close;
 
 			perf_session__set_id_hdr_size(session);
+			perf_session__set_comm_exec(session);
 		}
 	}
 
@@ -866,8 +886,10 @@
 	switch (event->header.type) {
 	case PERF_RECORD_HEADER_ATTR:
 		err = tool->attr(tool, event, &session->evlist);
-		if (err == 0)
+		if (err == 0) {
 			perf_session__set_id_hdr_size(session);
+			perf_session__set_comm_exec(session);
+		}
 		return err;
 	case PERF_RECORD_HEADER_EVENT_TYPE:
 		/*