[RFC PATCH 14/14] migration: Fix return-path thread exit

["Cédric Le Goater" <clg@redhat.com>]

In case of error, close_return_path_on_source() can perform a shutdown
to exit the return-path thread.  However, in migrate_fd_cleanup(),
'to_dst_file' is closed before calling close_return_path_on_source()
and the shutdown fails, leaving the source and destination waiting for
an event to occur.

Close the file after calling close_return_path_on_source() so that the
shutdown succeeds and the return-path thread exits.

Signed-off-by: Cédric Le Goater <clg@redhat.com>
---

 This is an RFC because the correct fix implies reworking the QEMUFile
 construct, built on top of the QEMU I/O channel.

 migration/migration.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/migration/migration.c b/migration/migration.c
index 5f55af3d7624750ca416c4177781241b3e291e5d..de329f2c553288935d824748286e79e535929b8b 100644
--- a/migration/migration.c
+++ b/migration/migration.c
@@ -1313,6 +1313,8 @@ void migrate_set_state(int *state, int old_state, int new_state)
 
 static void migrate_fd_cleanup(MigrationState *s)
 {
+    QEMUFile *tmp = NULL;
+
     g_free(s->hostname);
     s->hostname = NULL;
     json_writer_free(s->vmdesc);
@@ -1321,8 +1323,6 @@ static void migrate_fd_cleanup(MigrationState *s)
     qemu_savevm_state_cleanup();
 
     if (s->to_dst_file) {
-        QEMUFile *tmp;
-
         trace_migrate_fd_cleanup();
         bql_unlock();
         if (s->migration_thread_running) {
@@ -1341,15 +1341,14 @@ static void migrate_fd_cleanup(MigrationState *s)
          * critical section won't block for long.
          */
         migration_ioc_unregister_yank_from_file(tmp);
-        qemu_fclose(tmp);
     }
 
-    /*
-     * We already cleaned up to_dst_file, so errors from the return
-     * path might be due to that, ignore them.
-     */
     close_return_path_on_source(s);
 
+    if (tmp) {
+        qemu_fclose(tmp);
+    }
+
     assert(!migration_is_active(s));
 
     if (s->state == MIGRATION_STATUS_CANCELLING) {
-- 
2.43.0