signal_cb
signal_set(&ev, SIGALRM, signal_cb, &ev);
signal_set(&ev_one, SIGALRM, signal_cb, &ev_one);
signal_set(&ev_two, SIGALRM, signal_cb, &ev_two);
signal_set(&ev, SIGUSR1, signal_cb, &ev);
signal_set(&ev, SIGUSR1, signal_cb, &ev);
signal_set(&ev1, SIGUSR1, signal_cb, &ev1);
signal_set(&ev2, SIGUSR1, signal_cb, &ev2);
signal_set(&ev, SIGCONT, signal_cb, &ev);
signal_set(&ev, SIGUSR1, signal_cb, &ev);
struct signal_cb *s = container_of(cb, typeof(*s), base);
struct signal_cb cb = { .seen = false };
dma_fence_add_callback(&rq->fence, &cb.base, signal_cb);