Re: [PATCH 13/14] migration: Use migrate_has_error() in close_return_path_on_source()

[Cédric Le Goater]

On 2/8/24 14:07, 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. This
> > 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.
> >
> > Avoid relying on '->to_dst_file' and use migrate_has_error() instead.
> >
> > Suggested-by: Peter Xu <peterx@redhat.com>
> > Signed-off-by: Cédric Le Goater <clg@redhat.com>
> > ---
> >   migration/migration.c | 3 +--
> >   1 file changed, 1 insertion(+), 2 deletions(-)
> >
> > diff --git a/migration/migration.c b/migration/migration.c
> > index 
> > d5f705ceef4c925589aa49335969672c0d761fa2..5f55af3d7624750ca416c4177781241b3e291e5d
> >  100644
> > --- a/migration/migration.c
> > +++ b/migration/migration.c
> > @@ -2372,8 +2372,7 @@ static bool close_return_path_on_source(MigrationState 
> > *ms)
> >        * 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);
> >           }
> >       }
>
> Hm, maybe Peter can help defend this, but this assumes that every
> function that takes an 'f' and sets the file error also sets
> migrate_set_error(). I'm not sure we have determined that, have we?

How could we check all the code path ? I agree it is difficult when
looking at the code :/

Thanks,

C.