perf db-export: Also export thread's current comm

Currently, the initial comm of the main thread is exported. Export also
a thread's current comm. That better supports the tracing of
multi-threaded applications that set different comms for different
threads to make it easier to distinguish them.
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190710085810.1650-13-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/db-export.c

@@ -299,6 +299,7 @@ int db_export__sample(struct db_export *dbe, union perf_event *event,
 	};
 	struct thread *main_thread;
 	struct comm *comm = NULL;
+	struct comm *curr_comm;
 	int err;
 
 	err = db_export__evsel(dbe, evsel);
@@ -350,6 +351,13 @@ int db_export__sample(struct db_export *dbe, union perf_event *event,
 		}
 	}
 
+	curr_comm = thread__comm(thread);
+	if (curr_comm) {
+		err = db_export__comm(dbe, curr_comm, thread);
+		if (err)
+			goto out_put;
+	}
+
 	es.db_id = ++dbe->sample_last_db_id;
 
 	err = db_ids_from_al(dbe, al, &es.dso_db_id, &es.sym_db_id, &es.offset);