On Thu, Jun 24, 2021 at 06:14:39PM +0100, Dr. David Alan Gilbert wrote: > * Leonardo Bras (leob...@redhat.com) wrote: > > Currently, if a qemu instance is started with "-incoming defer" and > > an incorect parameter is passed to "migrate_incoming", it will print the > > expected error and reply with "duplicate yank instance" for any upcoming > > "migrate_incoming" command. > > > > This renders current qemu process unusable, and requires a new qemu > > process to be started before accepting a migration. > > > > This is caused by a yank_register_instance() that happens in > > qemu_start_incoming_migration() but is never reverted if any error > > happens. > > > > Solves this by unregistering the instance if anything goes wrong > > in the function, allowing a new "migrate_incoming" command to be > > accepted. > > > > Fixes: b5eea99ec2f ("migration: Add yank feature", 2021-01-13) > > Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1974366 > > Signed-off-by: Leonardo Bras <leob...@redhat.com> > > > > --- > > migration/migration.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/migration/migration.c b/migration/migration.c > > index 4228635d18..ddcf9e1868 100644 > > --- a/migration/migration.c > > +++ b/migration/migration.c > > @@ -474,9 +474,13 @@ static void qemu_start_incoming_migration(const char > > *uri, Error **errp) > > } else if (strstart(uri, "fd:", &p)) { > > fd_start_incoming_migration(p, errp); > > } else { > > - yank_unregister_instance(MIGRATION_YANK_INSTANCE); > > error_setg(errp, "unknown migration protocol: %s", uri); > > } > > + > > + if (*errp) { > > + yank_unregister_instance(MIGRATION_YANK_INSTANCE); > > + } > > My understanding is that testing *errp isn't allowed, because > it's legal to pass NULL to ignore errors, or legal to pass > &error_abort to mean that any error you do hit will cause the > process to assert; so you need to have something separate you can test.
Per my understanding error_abort should be fine, as the value of error_abort is still NULL (in error_setg() we only check against &error_abort as the pointer, and its value seems to be better always be NULL..). But indeed at least we need "errp && *errp", but that won't capture the case when errp==NULL. So I think we may need to define a local error, check here when unregister yank, and do error_propagate() before return.. -- Peter Xu