perf db-export: Move export__comm_thread into db_export__sample()

Move call to db_export__comm_thread() from db_export__thread() into
db_export__sample() because it makes the code easier to understand, and
add explanatory comments.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/20190710085810.1650-7-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/db-export.c b/tools/perf/util/db-export.c
index 99ad759..78f62a7 100644 (file)
--- a/tools/perf/util/db-export.c
+++ b/tools/perf/util/db-export.c
@@ -59,25 +59,17 @@ int db_export__machine(struct db_export *dbe, struct machine *machine)
 }
 
 int db_export__thread(struct db_export *dbe, struct thread *thread,
-                     struct machine *machine, struct comm *comm,
-                     struct thread *main_thread)
+                     struct machine *machine, struct thread *main_thread)
 {
        u64 main_thread_db_id = 0;
-       int err;
 
        if (thread->db_id)
                return 0;
 
        thread->db_id = ++dbe->thread_last_db_id;
 
-       if (main_thread) {
-               if (main_thread != thread && comm) {
-                       err = db_export__comm_thread(dbe, comm, thread);
-                       if (err)
-                               return err;
-               }
+       if (main_thread)
                main_thread_db_id = main_thread->db_id;
-       }
 
        if (dbe->export_thread)
                return dbe->export_thread(dbe, thread, main_thread_db_id,
@@ -303,15 +295,19 @@ int db_export__sample(struct db_export *dbe, union perf_event *event,
 
        main_thread = thread__main_thread(al->machine, 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,
+               err = db_export__thread(dbe, main_thread, al->machine,
                                        main_thread);
                if (err)
                        goto out_put;
+               /*
+                * Export comm before exporting the non-main thread because
+                * db_export__comm_thread() can be called further below.
+                */
+               comm = machine__thread_exec_comm(al->machine, main_thread);
                if (comm) {
                        err = db_export__exec_comm(dbe, comm, main_thread);
                        if (err)
@@ -321,10 +317,21 @@ int db_export__sample(struct db_export *dbe, union perf_event *event,
        }
 
        if (thread != main_thread) {
-               err = db_export__thread(dbe, thread, al->machine, comm,
-                                       main_thread);
+               /*
+                * For a non-main thread, db_export__comm_thread() must be
+                * called only if thread has not previously been exported.
+                */
+               bool export_comm_thread = comm && !thread->db_id;
+
+               err = db_export__thread(dbe, thread, al->machine, main_thread);
                if (err)
                        goto out_put;
+
+               if (export_comm_thread) {
+                       err = db_export__comm_thread(dbe, comm, thread);
+                       if (err)
+                               goto out_put;
+               }
        }
 
        es.db_id = ++dbe->sample_last_db_id;

diff --git a/tools/perf/util/db-export.h b/tools/perf/util/db-export.h
index 6e26732..811a678 100644 (file)
--- a/tools/perf/util/db-export.h
+++ b/tools/perf/util/db-export.h
@@ -75,8 +75,7 @@ void db_export__exit(struct db_export *dbe);
 int db_export__evsel(struct db_export *dbe, struct perf_evsel *evsel);
 int db_export__machine(struct db_export *dbe, struct machine *machine);
 int db_export__thread(struct db_export *dbe, struct thread *thread,
-                     struct machine *machine, struct comm *comm,
-                     struct thread *main_thread);
+                     struct machine *machine, struct thread *main_thread);
 int db_export__exec_comm(struct db_export *dbe, struct comm *comm,
                         struct thread *main_thread);
 int db_export__comm_thread(struct db_export *dbe, struct comm *comm,