Re: [PATCH 1/2] migration: Add a file_error argument to close_return_path_on_source()

["Cédric Le Goater" <clg@redhat.com>]

On 2/2/24 15:30, Fabiano Rosas wrote:
> Cédric Le Goater <clg@redhat.com> writes:
> 
>> close_return_path_on_source() retrieves the migration error from the
>> the QEMUFile '->to_dst_file' to know if a shutdown is required to exit
>> the return-path thread. However, in migrate_fd_cleanup(), '->to_dst_file'
>> is cleaned up before calling close_return_path_on_source() and the
>> shutdown is never performed, leaving the source and destination
>> waiting for an event to occur.
> 
> Isn't this just missing qemu_file_shutdown() at migrate_fd_cleanup?
> 
>      if (s->to_dst_file) {
>          ...
>          migration_ioc_unregister_yank_from_file(tmp);
> +       qemu_file_shutdown(tmp);
>          qemu_fclose(tmp);
>      }
> 

That would make the return-path thread exit indeed. It should not
be necessary when there are no errors though and this is done
outside of the close_return_path_on_source() helper. There could
be side effects.


I took into account Peter's comment and replaced the changes of
PATCH 1 with :

@@ -2372,8 +2372,7 @@ static bool close_return_path_on_source(
       * cause it to unblock if it's stuck waiting for the destination.
       */
      WITH_QEMU_LOCK_GUARD(&ms->qemu_file_lock) {
-        if (ms->to_dst_file && ms->rp_state.from_dst_file &&
-            qemu_file_get_error(ms->to_dst_file)) {
+        if (migrate_has_error(ms) && ms->rp_state.from_dst_file) {
              qemu_file_shutdown(ms->rp_state.from_dst_file);
          }
      }

Nevertheless, we need to qemu_file_shutdown() correctly the socket
for this to work and the problem seems more complex than just moving
code as I did in PATCH 2.

Thanks,

C.