Fix mutex bug
@ -195,6 +195,7 @@ static grpc_subchannel *subchannel_factory_create_subchannel(
memset(c, 0, sizeof(*c));
c->base.vtable = &connector_vtable;
c->security_connector = f->security_connector;
gpr_mu_init(&c->mu);
gpr_ref_init(&c->refs, 1);
args->mdctx = f->mdctx;
args->args = final_args;