perf db-export: Export main_thread in db_export__sample()

Export main_thread in db_export__sample() because it makes the code
easier to understand, and prepares db_export__thread() for further
simplification.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190710085810.1650-5-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 18 insertions, 12 deletions

diff --git a/tools/perf/util/db-export.c b/tools/perf/util/db-export.c
index 14501236c046..63f9edf65eee 100644
--- a/tools/perf/util/db-export.c
+++ b/tools/perf/util/db-export.c
@@ -71,16 +71,10 @@ int db_export__thread(struct db_export *dbe, struct thread *thread,
         thread->db_id = ++dbe->thread_last_db_id;
 
         if (main_thread) {
-                if (main_thread != thread) {
-                        err = db_export__thread(dbe, main_thread, machine,
-                                                comm, main_thread);
+                if (main_thread != thread && comm) {
+                        err = db_export__comm_thread(dbe, comm, thread);
                         if (err)
                                 return err;
-                        if (comm) {
-                                err = db_export__comm_thread(dbe, comm, thread);
-                                if (err)
-                                        return err;
-                        }
                 }
                 main_thread_db_id = main_thread->db_id;
         }
@@ -308,12 +302,24 @@ int db_export__sample(struct db_export *dbe, union perf_event *event,
                 return err;
 
         main_thread = thread__main_thread(al->machine, thread);
-        if (main_thread)
+        if (main_thread) {
                 comm = machine__thread_exec_comm(al->machine, main_thread);
+                /*
+                 * A thread has a reference to the main thread, so export the
+                 * main thread first.
+                 */
+                err = db_export__thread(dbe, main_thread, al->machine, comm,
+                                        main_thread);
+                if (err)
+                        goto out_put;
+        }
 
-        err = db_export__thread(dbe, thread, al->machine, comm, main_thread);
-        if (err)
-                goto out_put;
+        if (thread != main_thread) {
+                err = db_export__thread(dbe, thread, al->machine, comm,
+                                        main_thread);
+                if (err)
+                        goto out_put;
+        }
 
         if (comm) {
                 err = db_export__exec_comm(dbe, comm, main_thread);